Alden was retained by the Northern Water Conservancy District (Northern Water) for the Hansen Supply Canal Poudre River Drop Structure Replacement Project. Alden was the prime consultant for the Project and provided complete structural and hydraulic engineering services, including hydraulic modeling for the design of the replacement drop structure and overall site improvements. The new structure included a stepped spillway, stilling basin, and retaining walls.
Alden performed Computational Fluid Dynamics (CFD) modeling of the existing structure and the proposed structure. The new structure is designed for a peak discharge of 1,500 cfs. Alden also performed 3D finite element modeling for the structural design. Alden collaborated with Northern Water staff to identify maintenance needs and preferences for the new structure. The stilling basin includes an access bridge, jib cranes, and stoplogs to isolate the structure for future maintenance and inspections. The existing site featured extremely steep slopes at 1V:1H with poor surface drainage. The final grading established stable slopes and improved surface drainage to keep water away from the new structure.
Details of the project included:
Concrete structure demolition, removal, and repair
New concrete stepped spillway, concrete stilling basin, and concrete retaining walls
Foot bridge with access stairs
Subsurface drain system and surface drainage improvements
Temporary construction cofferdam and dewatering
Site grading and access road
Trapezoidal channel restoration and riprap sizing
The project also required coordination regarding the environmental impacts to the Preble's mouse habitat and an adjacent eagle's nest. Design was completed in July 2019. Construction was completed in March 2020 with the first water flowing through the structure on April 1, 2020.
}', 9='{type=image, value=Image{width=1200, height=675, url='https://www.aldenlab.com/hubfs/Projects/Poudre-River-Drop-Structure/Poudre-New-Construction-Structure-After-2.jpeg'}}', 10='{type=string, value=The newly constructed Poudre River Drop Structure along the Hansen Supply Canal}', 11='{type=image, value=Image{width=1200, height=675, url='https://www.aldenlab.com/hubfs/Projects/Poudre-River-Drop-Structure/site-improvements-for-new-drop-structure-poudre-river-structure-project.jpg'}}', 12='{type=string, value=Site improvements for the new Poudre River Drop Structure Project}', 13='{type=image, value=Image{width=3420, height=1869, url='https://www.aldenlab.com/hubfs/Projects/Poudre-River-Drop-Structure/Poudre-Existing-Structure-Before.jpg'}}', 14='{type=string, value=The original Poudre River Drop Structure}', 15='{type=image, value=Image{width=720, height=487, url='https://www.aldenlab.com/hubfs/Projects/Poudre-River-Drop-Structure/Poudre-Original-Structure-and-Site-Prior-New-Construction.jpg'}}', 16='{type=string, value=The existing site featured extremely steep slopes with poor surface drainage}', 17='{type=image, value=Image{width=1200, height=675, url='https://www.aldenlab.com/hubfs/Projects/Poudre-River-Drop-Structure/Poudre-River-Drop-Structure-CFD-Modeling.jpg'}}', 18='{type=string, value=Alden performed CFD modeling of the existing and proposed structures}', 19='{type=image, value=Image{width=840, height=473, url='https://www.aldenlab.com/hubfs/Projects/Poudre-River-Drop-Structure/Concrete-Placement-During-Periodic-Inspection-Visits-Poudre-River-Drop-Structure.jpg'}}', 20='{type=string, value=In addition to preparing design drawings and technical specifications, Alden also provided engineering services during construction}', 26='{type=number, value=1}', 29='{type=string, value=
2020 H2O Project Award
The Poudre River Drop Structure Project was the recipient of The Colorado Contractors Association's 4th Annual H2O Awards. The Project won in the category of Open Concrete Flow Structures under $6 million.
Design Team – Alden and geotechnical subconsultant, Lithos Engineering
Client – Northern Water
Contractor - Zak Dirt
}', 30='{type=string, value=Alden provided structural and hydraulic engineering and CFD modeling to replace the Poudre River drop structure with a stepped spillway and stilling basin.}'}
Dam Remediation Using High and Low Mobility Pressure Grouting
Logan Martin Dam, owned and operated by Alabama Power Company, is a hydroelectric generation site located on the Coosa River in Vincent, Alabama. Since construction in the late 1960’s, ongoing remedial pressure grouting projects have targeted significant seepage flow reduction beneath the embankment dam which is founded on karst, a limestone geology characterized by underground aquifers, caverns, and the potential for sinkholes, particularly as seepage flow erodes the underlying limestone and continually changes its distribution. Alden and Alabama Power have partnered to design and construct a large scale enclosed pressure grouting test chamber (3’ wide by 3’ tall by 30’ long) and an associated test protocol to evaluate and optimize grout mix design performance in geo-materials that simulate the fractured, cavernous geology at Logan Martin Dam.
This first-of-a-kind test approach uses a small production scale grout plant to prepare and inject the high mobility grout mixtures into the test chamber. The test chamber is designed with discharge ports along its length to allow water initially occupying the test chamber—and subsequently grout—to be displaced as newly batched grout is injected. Throughout the grout injection process, pressure and temperature measurements within the test chamber, as well as discharge flow rate and discharge flow specific gravity measurements out of the test chamber, are used to monitor and evaluate grout dispersion characteristics within the chamber.
Grout injection criteria used to govern test advancement and later termination includes displaced grout quality (i.e., displaced grout specific gravity relative to that of the freshly batched grout) and the internal test chamber pressure. After grout injection, various performance metrics are evaluated to quantify mix effectiveness. The normalized grout take, for example, evaluates the overall mix efficiency by relating the injected grout volume to the volume available within the geo-material for grout to occupy.
Since conception, updates to the test facility and protocol have been made to facilitate low mobility grout testing, as well as grout performance testing in the presence of water cross flow. Results from this ongoing research program are being used to reduce grouting cost through grout mix design and bore hole spacing optimization, while also improving dam safety by increasing knowledge on how grout penetrates rock fractures without in-situ excavation.
}', 9='{type=image, value=Image{width=1500, height=575, url='https://www.aldenlab.com/hubfs/Projects/Grout-Testing/Grout-Performance-Testing-Chamber.jpeg'}}', 10='{type=string, value=Alden and Alabama Power have partnered to design and construct a first-of-its-kind grout performance testing chamber }', 11='{type=image, value=Image{width=1504, height=314, url='https://www.aldenlab.com/hubfs/Projects/Grout-Testing/Grout-Performance-Testing-Rock-Side-View-1.jpeg'}}', 12='{type=string, value=A side view of grouted rock after the grout injection process aids in evaluation of grout dispersion characteristics within the chamber}', 26='{type=number, value=0}', 30='{type=string, value=An innovative large scale enclosed pressure grouting test chamber is being used to evaluate and optimize grout mix design performance at Logan Martin Dam}'}
Through funding made available by the U.S. Department of Energy, Alden conducted a series of studies to evaluate and optimize the design and operation of two modular and scalable fish bypass systems developed specifically to provide safe downstream passage of silver American Eels at hydropower projects. The goal of the studies was to address the need for biologically effective and less expensive downstream fish passage technologies for silver eels. The studies were developed specifically for this fish species and life stage due to population declines in many areas of its range and the potential for mortality to occur if eels migrating to the marine environment to spawn are entrained through hydro turbines during their journey to the sea. The large size and unique behaviors of silver eels have made it difficult for dam owners to implement downstream passage measures that are both biologically and cost effective, resulting in a need for new innovative technologies.
The studies conducted by Alden included a laboratory evaluation of the biological performance of the two bypass systems, a field evaluation of biological performance conducted with full-scale bypass systems installed at the intake of a small hydro project in New Hampshire, CFD modeling of the laboratory flume and field evaluation site, and a desktop assessment of the potential for application of each technology at hydro projects within the known range of American Eel and the expected benefits (i.e., biological and economic). Few organizations have the capabilities to conduct this array of technical studies, but Alden’s scientists and engineers have been using various combinations of these approaches and methods to develop and evaluate state-of-the-art fish passage and protection systems for nearly 50 years.
Assistance with the performance and completion of these studies was provided by Lakeside Engineering (bypass design and installation) and Blue Leaf Environmental (DIDSON acoustic camera and 3D acoustic telemetry services).
}', 6='{type=string, value=https://www.aldenlab.com/hubfs/videos/Eel_Fish_Passage_2020.mp4}', 7='{type=string, value=https://www.aldenlab.com/hubfs/videos/Eel_Fish_Passage_Field_Study.mp4}', 8='{type=string, value=Evaluation of bypass performance with silver eels happened in both controlled laboratory settings and at a small hydro project to determine the bypass efficiency and behavioral responses, so as to optimize design and operation of the bypass systems.}', 9='{type=image, value=Image{width=1200, height=600, url='https://www.aldenlab.com/hubfs/Projects/DOE-Eel-Passage/Laboratory-Test-Facility-DOE-Eel-Fish-Passage-Study.jpg'}}', 10='{type=string, value=The laboratory evaluation was conducted in a large re-circulating flume using the Klawa horizontal zig-zag eel bypass system and a vertical eel bypass system developed by Lakeside Engineering}', 11='{type=image, value=Image{width=1200, height=600, url='https://www.aldenlab.com/hubfs/Projects/DOE-Eel-Passage/DOE-Eel-Passage-Study-biologist-with-eel.jpg'}}', 12='{type=string, value=Silver American eels were PIT tagged and measured for length, weight, and eye diameters prior to testing}', 13='{type=image, value=Image{width=1200, height=580, url='https://www.aldenlab.com/hubfs/Projects/DOE-Eel-Passage/Pathlines-colored-by-velocity-DOE-Eel-Fish-Passage-Study.jpg'}}', 14='{type=string, value=CFD modeling was performed to model the hydraulic conditions of the lab and field studies}', 15='{type=image, value=Image{width=1200, height=600, url='https://www.aldenlab.com/hubfs/Projects/DOE-Eel-Passage/Mine-Falls-Field-Installation-DOE-Eel-Passage-Study-1.jpg'}}', 16='{type=string, value=Field evaluation of biological performance conducted with full-scale bypass systems installed at the intake of a small hydro project}', 17='{type=image, value=Image{width=1200, height=600, url='https://www.aldenlab.com/hubfs/Projects/DOE-Eel-Passage/Mine-Falls-Hydro-Project-Nashua-NH-DOE-Eel-Passage-Study-Field-Location.jpg'}}', 18='{type=string, value=Mine Falls Hydroelectric Project, located on the Nashua River in Nashua, New Hamsphire, was chosen as the site for the field evaluation}', 26='{type=number, value=0}', 30='{type=string, value=Read how Alden tested the effects of innovative downstream fish passage technologies with lab, CFD, and field analysis. Funded by the Department of Energy}'}
Alden was contracted by Imperia Engineering for mock-up and head loss testing of cured in place pipe (CIPP) lining. Seabrook Nuclear Power plant was planning to perform maintenance on its service water piping system which consists of safety and non-safety function concrete lined pipe. The planned maintenance consisted of lining the pipes using a glass fiber reinforced epoxy resin composite. To ensure the maintenance activity would be successful, Imperia Engineering organized a mock-up test of the installation mechanics for the smallest inner diameter pipe (20”) and contracted Alden to perform flow testing on the mock-up pipe loop to help determine the effects of the lining on the flow performance of the piping network.
The chosen piping configuration for the mock-up test focuses on a section of 20” pipe that supplies systems related to turbine cooling. The section in question combined a number of direction and elevation changing pipe fittings. Incorporating this section into the mock-up provided a challenge for the installer and provided some insight into the potential stack-up of flow losses from these types of fitting combinations. It made the positive identification of individual fitting losses much more challenging.
Along with assembling the provided test piping, Alden constructed a custom flow loop with a large recirculation pump and a flow meter assembly. The flow meter assembly consisted of two flow meters allowing measurements of flow rate to better than 1% uncertainty down to 2000 gpm. The recirculation pump had a relatively low discharge head capability (<45ft) but a high run out flow rate of 17,500 gpm. The loop was connected to a large water tank reservoir to allow the loop to be reconfigured and accessed between tests.
Each piece of test piping was outfitted with multiple sets of taps for the purpose of pressure loss measurements. Pressure loss measurements along the pipeline were taken at a range of flow rates to evaluate Reynolds number effects.
The pipeline was tested by Alden first in its original cement lined state, then with Weko seals installed at various joint locations, and then finally following CIPP lining of the entire length of test piping (lining performed onsite at Alden by Aquarehab). Alden analyzed the test results to determine friction losses and loss coefficients for each type of fitting and straight sections of pipe, under all three scenarios, providing the required insight to the viability of CIPP lining at Seabrook. Measurements showed that the friction factor drop in the pipe was sufficient to compensate for the reduced pipe diameter. However, losses substantially increased at turns where excess material folds increase turbulent losses by obstructing flow near the inside turn of the wall. Mock-up testing and careful hydraulic analysis is therefore required when applying the lining system to a pipeline where the pump performance margin is small.
Contact us for more information on mock-up testing.
}', 9='{type=image, value=Image{width=1500, height=900, url='https://www.aldenlab.com/hubfs/Projects/Seabrook-Pipe-Lining-Testing/Seabrook-Lined-Pipes-Lining-Contractor-AquaRehab.jpg'}}', 10='{type=string, value=Alden constructed a custom flow loop with the provided test piping that was lined onsite by a contractor}', 11='{type=image, value=Image{width=1500, height=900, url='https://www.aldenlab.com/hubfs/Projects/Seabrook-Pipe-Lining-Testing/Finished-Epoxy-Lined-Pipe-to-Elbow-for-mock-up-testing.jpg'}}', 12='{type=string, value=Mock-up testing and careful hydraulic analysis provided insight to the viability of CIPP lining at Seabrook}', 26='{type=number, value=0}', 30='{type=string, value=Alden performed mock-up flow testing to help determine the effects of cured in place pipe lining on flow performance at the Seabrook Nuclear Power Plant.}'}
Between 1932 and 2010 the state of Louisiana has lost about 2006 square miles of land due to a combination of subsidence, sea level rise, and management of the Mississippi River. Computer models predict a further loss of 1800 to 4200 square miles in the next 50 years, amounting to 55% of the land in Plaquemines Parish and resulting in $300 million in annual economic damage. Following hurricanes Katrina and Rita, the Coastal Protection and Restoration Authority (CPRA) was formed as a single state entity with the authority to protect and restore the lands of coastal Louisiana.
The $50 billion coastal master plan includes restoration and risk reduction projects. The restoration projects include barrier island restoration, hydrologic restoration, marsh creation, ridge restoration, sediment diversion, and shoreline protection. The Barataria and Breton Basins have experienced some of the largest land loss—almost 700 square miles. Two sediment diversions are being designed, one for each basin. The sediment diversions connect the Mississippi River to the basins, allowing for the controlled diversion of up to 75,000 cfs of water and sediment to the Barataria basin and 30,000 cfs to the Breton basin.
The design and construction of sediment diversions on the scale proposed for Barataria and Breton is unprecedented, the results of which will rely heavily on the numeric and physical modeling required to design the major diversion features, including the inlet, conveyance, and outlet structures. Alden is constructing two 1:65-scale, live-bed physical models to test performance and effectiveness of the diversions.
}', 6='{type=string, value=https://cdn2.hubspot.net/hubfs/5468894/Projects/Mid-Barataria/client-visit-052119.mp4}', 9='{type=image, value=Image{width=null, height=null, url='https://cdn2.hubspot.net/hubfs/5468894/Projects/Mid-Barataria/Client-Visit-052119.jpeg'}}', 10='{type=string, value=Clients and Alden Engineers discussing model at initial testing visit}', 11='{type=image, value=Image{width=null, height=null, url='https://cdn2.hubspot.net/hubfs/5468894/Projects/Mid-Barataria/Final-Construction-Diversion.jpeg'}}', 12='{type=string, value=Model of the river sediment diversion inlet prior to water and sediment being added to the model}', 13='{type=image, value=Image{width=null, height=null, url='https://www.aldenlab.com/hubfs/Projects/Mid-Barataria/Final-Construction-Ship-2.jpeg'}}', 14='{type=string, value=Model of a barge being used in conjuction with Mississippi River model for Mid-Barataria}', 15='{type=image, value=Image{width=null, height=null, url='https://www.aldenlab.com/hubfs/Projects/Mid-Barataria/Mid-B-Construction-River-Bed.jpeg'}}', 16='{type=string, value=The Mid-Barataria Mississippi River model in mid-construction}', 17='{type=image, value=Image{width=null, height=null, url='https://www.aldenlab.com/hubfs/Projects/Mid-Barataria/Mid-B-Template-Construction.jpeg'}}', 18='{type=string, value=Templating the river model
}', 19='{type=image, value=Image{width=null, height=null, url='https://www.aldenlab.com/hubfs/social-suggested-images/Mid-Barataria-River-Sediment.jpeg'}}', 20='{type=string, value=Sediment is simulated using hand-screed light weight media, spread 4-8 inches thick in this live bed model}', 26='{type=number, value=0}'}
Even though McGuire Nuclear Power Plant is located on the shores of Lake Norman, it relies on cooling water from a separate service water pond. Duke Energy, operators of the plant, wanted to investigate the conditions of the service pipeline that connects the service pond to the plant. They elected to use a robotic underwater vehicle attached to a tether. However, because the service water line connecting the pond to the plant is an important safety function, the retraction tension on the robotic underwater vehicle needed to be validated before the vehicle was deployed using a mock-up test.
Mock-up testing would determine if the tether would remain within the tether failure tension after the vehicle has advanced past several turns and more than several hundred feet into the pipeline. The main sources of tension on the tether are the turns in the pipeline.
Alden worked with Hibbard Inshore to set up a model of the pipeline bends with limited straight pipe lengths between them to correctly simulate the tether friction during a retraction. In addition, the mock-up test demonstrated to the plant the ability to identify various pipeline characteristics of interest that could be encountered during the real inspection. The mock-up also provided a similar level of water visibility to ensure the rover inspection would still be successful under turbid water conditions.
Contact us for more information on mock-up testing.
}', 9='{type=image, value=Image{width=2304, height=1296, url='https://www.aldenlab.com/hubfs/Projects/Rover/Alden-Rover-Mock-Up-Test-Piping.jpg'}}', 10='{type=string, value=A model of the pipeline bends was used to correctly simulate the friction that the tether would experience during a retraction}', 11='{type=image, value=Image{width=2304, height=1296, url='https://www.aldenlab.com/hubfs/Projects/Rover/Alden-Rover-Mock-Up-Test-Rover.jpg'}}', 12='{type=string, value=By using a mock-up test, the team at Alden was able to validate the retraction tension on a robotic underwater vehicle before the vehicle was deployed}', 26='{type=number, value=0}', 30='{type=string, value=Alden performed mock-up testing to correctly simulate tension on a tethered ROV}'}
A Heat Recovery Steam Generator (HRSG) had suspected flow deficiencies which was causing suboptimal performance of the unit. Alden was contacted to use CFD to conduct an evaluation of the unit and design flow controls to improve its steam generation.
To complete this evaluation, Alden developed a baseline CFD model of the HRSG from the turbine outlet to the tube bank inlet to understand how the flow develops in this section. An area of recirculation and the reasons it developed were identified. A set of flow controls was designed to address the recirculating gas. Alden worked with the client to ensure that the flow controls were both effective and practical to construct and install into the existing system.
Results
Using the drawings provided, the oil & gas plant constructed and implemented the flow controls designed by Alden. Subsequently, the plant saw a 17% improvement in steam generation when the unit was tested with the new flow controls
Project Highlights
CFD model identified flow inefficiency
Flow controls were iteratively designed with input from the clients
Steam generation increased 17% after implementation of the flow controls
}', 9='{type=image, value=Image{width=1185, height=575, url='https://www.aldenlab.com/hubfs/Projects/HRSG-Flow-Control/HRSG-Baseline-CFD.jpg'}}', 10='{type=string, value=Alden developed baseline CFD to evaluate a HRSG unit with suspected flow deficiencies}', 11='{type=image, value=Image{width=1185, height=575, url='https://www.aldenlab.com/hubfs/Projects/HRSG-Flow-Control/HRSG-Flow-Control-CFD.jpg'}}', 12='{type=string, value=A set of flow controls were designed to address an area of recirculating gas}', 26='{type=number, value=0}', 30='{type=string, value=Alden used CFD to evaluate and improve a heat recovery steam generator (HRSG) performance }'}
The Cedar Cliff dam and hydropower project is located approximately six miles from Cullowhee, in Jackson Country, North Carolina. The dam and hydroelectric facility is owned by Duke Energy and is located downstream of three other hydroelectric projects that are operated as a system.
The primary spillway includes a Tainter gate and the existing auxiliary spillway system includes two fuse plug sections (with different crest/activation elevations). It was determined that the combination of the primary and auxiliary spillway systems were not adequate to safely pass the regulatory-increased Inflow Design Flood (IDF). The construction of a Hydroplus Fusegate system with six semi-labyrinth Fusegates in an enlarged auxiliary spillway channel was selected to increase spillway capacity to safely pass the new IDF which is now the full Probable Maximum Flood (PMF).
Two reduced scale physical models were constructed to determine the required size of a ventilation system for the proposed Cedar Cliff Fusegates and headpond and tailwater levels at each Fusegate for flows up to the sixth Fusegate activating. The tailwater levels were required for design of the Fusegate ballast system.
}', 6='{type=string, value=https://www.aldenlab.com/hubfs/Projects/Cedar-Cliff/Cedar-Cliff-Model-Testing.mp4}', 9='{type=image, value=Image{width=null, height=null, url='https://cdn2.hubspot.net/hubfs/5468894/Projects/Cedar%20Cliff/Cedar-Cliff-Model-Test-Chute-Looking-Upstream.jpg'}}', 10='{type=string, value=Model testing looking upstream}', 11='{type=image, value=Image{width=null, height=null, url='https://cdn2.hubspot.net/hubfs/5468894/Projects/Cedar%20Cliff/Cedar-Cliff-Model-Test-Looking-Downstream.jpg'}}', 12='{type=string, value=Model tesing looking downstream}', 13='{type=image, value=Image{width=null, height=null, url='https://cdn2.hubspot.net/hubfs/5468894/Projects/Cedar%20Cliff/Cedar-Cliff-Model-Final-Construction-tailwater.jpg'}}', 14='{type=string, value=Cedar Cliff modeling during final construction}', 15='{type=image, value=Image{width=null, height=null, url='https://cdn2.hubspot.net/hubfs/5468894/Projects/Cedar%20Cliff/Cedar-Cliff-Model-Final-Construction.jpg'}}', 16='{type=string, value=Cedar Cliff model at final construction}', 17='{type=image, value=Image{width=null, height=null, url='https://cdn2.hubspot.net/hubfs/5468894/Projects/Cedar%20Cliff/Cedar-Cliff-Model-Construction-Piping.jpg'}}', 18='{type=string, value=View of the piping structures used to supply water to the Cedar Cliff model}', 23='{type=string, value=Z:Jobs1170CCUprate - Cedar Cliff Uprate}', 26='{type=number, value=0}'}
In order to meet screen velocity requirements of the Clean Water Act 316 b rule, American Electric Power has investigated the possibility of replacing the Clifty Creek Power Plant traveling water screens with an array of cylindrical wedgewire screens in the cooling water intake forebay. The site on the Ohio River experiences significant siltation, and there were concerns about associated vulnerability of the wedgewire screens.
Alden performed flow modeling to evaluate this possibility, and provide possible solutions. The model scope included river flow both upstream and downstream of the intake structure and flow within the intake structure. To model the geometric details of the system accurately, a field survey conducted by Alden was performed prior to the flow modeling efforts. The flow study included 2D and 3D numeric modeling, as well as scale physical modeling.
}', 23='{type=string, value=T:Hydraulic1150CliftyPhy - Clifty Creek Physical Model}', 9='{type=image, value=Image{width=null, height=null, url='https://cdn2.hubspot.net/hubfs/5468894/Projects/Clifty%20Creek/Clifty-Creek-Site-Visit.jpg'}}', 10='{type=string, value=Field survey conducted prior to model testing}', 26='{type=number, value=0}'}
The South Station Transportation Center (SSTC), located in Boston, Massachusetts, consists of a train terminal, regional bus terminal, and a public parking garage. Currently the bus terminal and parking garage are located above the south portion of the train platforms. The section of the tracks and platforms between the north end of the SSTC and the head house, which ranges in length from about 365 to 525 feet, is currently uncovered and open to the atmosphere.
The Boston South Station Project proposed to build high rise structures and to expand the bus terminal over the existing platform areas of South Station. In effect, the development will fully enclose the station tracks and platforms with the exception of the south “portal” area and the east edge of the development along Track 13.
Work Performed
Three locomotive/track arrangements were modeled to provide a representation of the “worst case” conditions with respect to the collection of the main and HEP engine diesel exhausts and cooling fan flows.
The efficacy of multiple exhaust hoods were evaluated to meet target health and safety standards while trains were parked at idle at the head end of the tracks. Specifically, the analyses were performed to ensure that the proposed track exhaust and general ventilation systems were able to maintain safe levels of train engine emissions concentrations and ambient air temperature while the trains were parked and idling in the station.
Project Evolution
1990 Alden initially provided the design for track exhaust hoods to remove diesel products from the ventilation systems to achieve safe levels. Design work was proved out through the use of physical scale modeling, chosen for its cost effectiveness
2005-2008 Alden provided the initial ventilation design for the high rise overbuild construction project
2017-2018 Following the reboot of the projct, Alden evaluated multiple scenarios to develop and finalize a robust ventilation system that could handle a variety of station situations.
Visualization of the Computational Model [below] shows the transient locomotive through station to show thermal and pollutant capture.
}', 6='{type=string, value=https://www.aldenlab.com/hubfs/videos/South-Station-Train-Ventilation-CFD-Modeling-Animation.mp4}', 9='{type=image, value=Image{width=null, height=null, url='https://www.aldenlab.com/hubfs/Projects/South-Station-Ventilation/2018-Final-Artist-Render.png'}}', 10='{type=string, value=The final artistic track view with passengers for scale (2018).}', 11='{type=image, value=Image{width=null, height=null, url='https://www.aldenlab.com/hubfs/Projects/South-Station-Ventilation/2008-Track1-2-Feasibility.png'}}', 12='{type=string, value=Track 1 & 2 Plenum Concept/Feasibility Study using CFD (2008). }', 13='{type=image, value=Image{width=null, height=null, url='https://www.aldenlab.com/hubfs/Projects/South-Station-Ventilation/2018-Track1-2-Design-for-Construction.png'}}', 14='{type=string, value=Track 1 & 2 Final Plenum Design for Construction using CFD (2018). }', 26='{type=number, value=0}', 29='{type=string, value=
}', 30='{type=string, value=Read how CFD modeling was used to show compliance with specifications and code requirements for a major New England rail station.}'}
An existing roof vent arrangement was allowing rainwater to enter the Pot Room. Alden supported efforts to develop a roof vent geometry to eliminate the intrusion of rain water. The purpose of the CFD study was to ensure that the roof vent modification did not increase pot room temperature levels beyond specified limits for workers in the plant.
To evaluate the existing and proposed Pot Room arrangements, thermal and fluid flow profiles in the immediate vicinity of the pots were determined based on air flows through the plant floor and wall mounted vents. The detailed CFD model was developed from plant drawings to include all major basement, pot room and roof venting geometries. The surrounding ambient environment was included with quiescent atmospheric conditions and average ambient temperature. Thermal losses form the pots to the pot room air and from the pot room to the environment were included in the analysis. The results of the CFD modeling showed that the proposed modification to the roof venting arrangement was acceptable and would not increase the temperature in the worker-occupied spaces by more than 2 degrees F.
}', 9='{type=image, value=Image{width=null, height=null, url='https://www.aldenlab.com/hubfs/Projects/Smelter-Pot-Room/Smelter-Pot-Room-Diagram.jpg'}}', 10='{type=string, value=Thermal and fluid flow profiles were evaluated for both existing and proposed venting arrangements}', 11='{type=image, value=Image{width=null, height=null, url='https://www.aldenlab.com/hubfs/Projects/Smelter-Pot-Room/Smelter-Pot-Room-Temperature-CFD.jpg'}}', 12='{type=string, value=Heat transfer from the pots to the air passing through the pot room were evaluated}', 13='{type=image, value=Image{width=null, height=null, url='https://www.aldenlab.com/hubfs/Projects/Smelter-Pot-Room/Smelter-Pot-Room-Ventilation-CFD.jpg'}}', 14='{type=string, value=CFD confirmed the efficacy of the modified roof vent system to maintain safe temperatures.}', 26='{type=number, value=0}', 30='{type=string, value=Read how a CFD study ensured that a roof vent modification did not increase pot room temperature levels beyond safe levels}'}
Plant McDonough, owned and operated by Southern Company, has
experienced excessive siltation at the makeup water intake. The intake uses cylindrical wedgewire
screening within an intake originally designed for much larger, once-through
cooling water flows. Flow modeling was performed to provide a viable passive
solution to reducing the sediment accumulation at the intake. To model the
geometric details of the system accurately, a field survey was performed prior
to the flow modeling efforts. The flow study included both CFD modeling and
scale physical modeling.
For this investigation, Alden developed a
1:20 scale live bed physical model. This
model was extremely well tuned to reproduce the behavior of bed load
sediment. Even with the very fine
crushed walnut shell particles, however, it was challenging to reproduce the
behavior of suspended load. The use of a
high fidelity CFD model, therefore, proved extremely useful for this project,
in that suspended load is generally very accurately tracked with CFD models,
which are not well validated for bed load simulation. By using the two together, the two extremes
of sediment transport are captured, and developing a solution that covers this
range has a high likelihood of success.
}', 9='{type=image, value=Image{width=null, height=null, url='https://cdn2.hubspot.net/hubfs/5468894/Projects/Plant%20McDonough/Physical-Model-Plant-McDonough.jpg'}}', 10='{type=string, value=A 1:20 live bed physical model was constructed to reproduce the behavior of suspended sediment load}', 11='{type=image, value=Image{width=null, height=null, url='https://cdn2.hubspot.net/hubfs/5468894/Projects/Plant%20McDonough/Original-Construction-Plant-McDonough.jpg'}}', 12='{type=string, value=Image of the plant under original construction, provided courtesy of Southern Company}', 23='{type=string, value=T:Hydraulic1140MCDPhy}', 26='{type=number, value=0}'}
{id=18271797054, createdAt=1571226251795, updatedAt=1633352692776, path='using-turbine-survival-models-and-existing-data-to-understand-the-impacts-of-hydropower-projects-on-an-endangered-species', name='Endangered Species Impact: Turbine Survival Models | Alden Projects', 32='{type=number, value=80}', 1='{type=string, value=Using Turbine Survival Models and Existing Data to Understand the Impacts of Hydropower Projects on an Endangered Species}', 2='{type=list, value=[{id=7, name='Environmental', order=5}, {id=13, name='Hydropower', order=1}]}', 34='{type=number, value=0}', 3='{type=list, value=[{id=12, name='Fish Passage', order=16}, {id=15, name='Fish Protection', order=17}]}', 4='{type=list, value=[{id=7, name='Desktop Analysis', order=4}]}', 5='{type=string, value=
A major component of an Atlantic salmon population model developed by NMFS is the survival of smolts and kelts passing downstream at hydropower projects. To obtain this information, NMFS contracted Alden to estimate downstream passage survival of Atlantic salmon smolts and kelts at 15 hydroelectric projects on Maine’s Penobscot River and its tributaries. These desktop survival estimates focus on direct mortality attributable to passage at dams and to multiple dam passage. An established turbine blade strike probability and mortality model was used to estimate direct survival of fish passing through turbines at each project. Survival rates for fish that pass downstream over spillways or through fish bypass facilities were estimated based on existing site-specific data or from studies conducted at other hydro projects with the same or similar species. Most of the projects included in the study have upstream passage facilities for anadromous species (river herring, American shad, and/or Atlantic salmon), as well as operating downstream bypasses for juvenile and adult outmigrants. Some of the projects have installed narrow-spaced bar racks or overlays to reduce fish entrainment through turbines.
The results of Alden’s survival analysis provided data in a level of detail that would have been extremely expensive and difficult to accomplish with field studies. Typically, turbine passage survival studies conducted in the field only evaluate one or two turbines operating at one or two gate settings (i.e., flow rates). The methods and model developed for NMFS for Atlantic salmon on the Penobscot River are transferable to other river systems and species. The theoretical model for predicting strike probability is applicable to most species and the blade strike mortality data for rainbow trout are considered representative of many other species.
}', 9='{type=image, value=Image{width=null, height=null, url='https://cdn2.hubspot.net/hubfs/5468894/Projects/NMFS-Survival/Mattaceunk-Brookfield.jpg'}}', 10='{type=string, value=Studies were conducted at the Mattaceunk hydropower project.}', 26='{type=number, value=0}', 30='{type=string, value=Using Turbine Survival Models and Existing Data to Understand the Impacts of Hydropower Projects on an Endangered Species}'}
{id=18271797055, createdAt=1571226251797, updatedAt=1633352364718, path='fish-survival-in-fish-return-systems-at-cooling-water-intakes', name='Fish Return Survival at Cooling Water Intakes | Alden Projects', 32='{type=number, value=90}', 1='{type=string, value=Fish Survival in Fish Return Systems at Cooling Water Intakes}', 2='{type=list, value=[{id=7, name='Environmental', order=5}, {id=13, name='Hydropower', order=1}]}', 34='{type=number, value=0}', 3='{type=list, value=[{id=3, name='316(b) Compliance', order=2}, {id=12, name='Fish Passage', order=16}, {id=15, name='Fish Protection', order=17}]}', 35='{type=string, value=building15}', 4='{type=list, value=[{id=3, name='Physical Modeling', order=0}, {id=10, name='Laboratory Testing', order=7}]}', 5='{type=string, value=
The Electric Power Research Institute (EPRI) has funded laboratory studies at Alden on the biological efficacy of fine-mesh screens for safely collecting larval and juvenile fish. However, little information existed on the effects of fish return systems on larval or early juvenile survival. Alden performed two years of laboratory evaluations on factors affecting larval fish survival in fish return systems at cooling water intake structures (CWISs). The project provided the additional data necessary to determine the overall biological efficacy of larval fish collection and return systems. The study was designed to evaluate the effects of velocity, drop height, length, drops and bends on larval fish survival through a fish return system.
}', 9='{type=image, value=Image{width=null, height=null, url='https://cdn2.hubspot.net/hubfs/5468894/Projects/EPRI-Fish-Survival/fish-return-90-degree-bends.jpg'}}', 10='{type=string, value=Testing 90 degree bends in a fish return system}', 11='{type=image, value=Image{width=null, height=null, url='https://cdn2.hubspot.net/hubfs/5468894/Projects/EPRI-Fish-Survival/Juvenile-bluegill-arranged-numbered.jpg'}}', 12='{type=string, value=Juvenile bluegill are arranged and numbered for analysis}', 13='{type=image, value=Image{width=null, height=null, url='https://cdn2.hubspot.net/hubfs/5468894/Projects/EPRI-Fish-Survival/juvenile-latent-mortality-test-tanks.jpg'}}', 14='{type=string, value=A look at a juvenile latent mortality testing tank}', 26='{type=number, value=0}', 30='{type=string, value=Alden performed two years of laboratory evaluations on factors affecting larval fish survival in fish return systems at cooling water intake structures}'}
{id=18271797056, createdAt=1571226251800, path='development-of-the-epri-technical-reference-manual-for-fish-protection-at-cooling-water-intake-structures', name='Development of the EPRI Technical Reference Manual for Fish Protection at Cooling Water Intake Structures | Alden Lab Projects', 32='{type=number, value=101}', 1='{type=string, value=Development of the EPRI Technical Reference Manual for Fish Protection at Cooling Water Intake Structures}', 2='{type=list, value=[{id=7, name='Environmental', order=5}, {id=13, name='Hydropower', order=1}]}', 34='{type=number, value=0}', 3='{type=list, value=[{id=3, name='316(b) Compliance', order=2}, {id=15, name='Fish Protection', order=17}]}', 4='{type=list, value=[{id=9, name='Technical Analysis', order=6}]}', 5='{type=string, value=
In 2012, Alden developed a report providing an updated review of the state of knowledge on fish protection technologies for use at power plant cooling water intake structures (CWISs) to meet requirements of §316(b) of the Clean Water Act (CWA). In general, power generating facilities have some flexibility in selecting fish protection technologies. The information provided in the report can be used by power generators, resource managers, and permitting agencies to determine the potential for different fish protection technologies to reduce impingement and/or entrainment losses at CWISs. Fish protection technologies are generally grouped into five functional categories—physical barriers, collection systems, diversion systems, behavioral guidance devices, and flow reduction. The performance, operational and maintenance issues, and documented installations of each technology in each functional category were described in the report. The results of the review indicated the importance of site-specific factors to the biological effectiveness and engineering practicality of a technology.
}', 9='{type=image, value=Image{width=null, height=null, url='https://cdn2.hubspot.net/hubfs/5468894/Projects/EPRI%20Technical%20Reference%20Manual/wedgewire-screen.jpg'}}', 10='{type=string, value=Cylindrical wedgewire screen in the Alden test flume}', 26='{type=number, value=0}'}
{id=18271797057, createdAt=1571226251802, updatedAt=1633352516808, path='laboratory-evaluation-of-fine-mesh-traveling-screens-for-protecting-larval-fish-at-cooling-water-intake-structures', name='Fine-mesh Traveling Screens for Protecting Larval Fish at CWIS | Alden Projects', 32='{type=number, value=110}', 1='{type=string, value=Laboratory Evaluation of Fine-mesh Traveling Screens for Protecting Larval Fish at Cooling Water Intake Structures}', 2='{type=list, value=[{id=7, name='Environmental', order=5}, {id=13, name='Hydropower', order=1}]}', 34='{type=number, value=0}', 3='{type=list, value=[{id=4, name='Intakes', order=3}]}', 35='{type=string, value=building15}', 4='{type=list, value=[{id=7, name='Desktop Analysis', order=4}, {id=10, name='Laboratory Testing', order=7}, {id=14, name='Prototype Testing', order=11}]}', 5='{type=string, value=
The main objective of the study was to determine the post-collection survival of larval fish when exposed to compounding stresses of screen impingement and transfer. In particular, the project sought to determine the effects of water velocity and duration of impingement on survival. This was a multi-year, multi-phase study that included small-scale, tabletop testing along with large-scale prototype testing involving multiple species.
Survival was evaluated for impingement and entrainment of larval fish of differing sizes and species. Initial testing was done in smaller, tabletop test flumes to allow extensive replication and to help in the selection of test conditions and variables to be used in the large flume testing. Testing was then moved to a large scale flume, using three different prototypes of traveling screens. Collection efficiency and survival rates were measured for different species, fish sizes, and flow velocities.
}', 9='{type=image, value=Image{width=null, height=null, url='https://cdn2.hubspot.net/hubfs/5468894/Projects/Traveling-Screens/flume-screens-water.jpg'}}', 10='{type=string, value=Three fine mesh screens in the Alden test flume with water}', 26='{type=number, value=0}', 30='{type=string, value=Read about a multi-year, multi-phase impingement survival study that included small-scale, tabletop testing along with large-scale prototype testing involving multiple species. }'}
The Highland Ditch Company services more than 40,000 acres of farmland. Its primary diversion infrastructure is located near Lyons, Colorado, along the St. Vrain River in Boulder County.
In September 2013, a five-day rainfall exceeded the annual average in Boulder County. The resulting flood destroyed Highland's diversion dam and headgate structure, which were built in 1870.
A design-build team was contracted to replace the hydraulic structures as quickly as possible so the system would be operational before spring runoff. The accelerated schedule was implemented so that water would be available for the 2014 irrigation season.
Alden's role included:
Hydrologic analysis
Hydraulic design
Structural engineering
Field inspections and engineering services during construction
The project design accommodated short lead times and readily available materials. Our team also developed rebar and steel shop drawings, which saved several weeks in the schedule.
The project features include:
350 cfs diversion structure with 5 headgates
Sluice structure with 2 sluice gates
70’ long diversion dam, including a grout curtain below
60’ long trash rack
More than 100’ of concrete retaining walls and wing walls
Scour protection
800’ long trapezoidal channel
This project started only weeks after the historic flood event in September 2013. Alden worked closely with the contractor to meet the aggressive schedule; construction was completed on February 5, 2014.
September 12 - 15, 2013: Peak of flooding; St. Vrain diversion structures fail
September 17, 2013: Engineering team, contractor, and owner meet at the site; design begins
October 5, 2013: Contractor begins reconstruction of the canal
October 30, 2013: First concrete placement for the new diversion structure
December 15, 2013: St. Vrain Creek is first diverted to Highland Ditch
February 5, 2014: Construction completed
}', 30='{type=string, value=When historic floods damaged the St. Vrain Diversion Structure, a design-build team was contracted to replace the hydraulic structures as quickly as possible. Read how Alden meet the aggressive schedule.}'}
A streamlined modeling approach reduced both cost and time to achieve an optimized design solution.
Williams Station Unit 1 is a 610 MW coal fired station owned by South Carolina Electric & Gas (SCE&G). The plant installed a new wet flue gas desulphurization (WFGD) system, which removes SO2 entrained in the flue gas stream. The approach of the physical flow model study was to minimize the potential for liquid pullback into the absorber inlet ducts by improving the gas flow distributions into the absorber. A parallel CFD model study was performed to optimize the spray nozzle locations and spray types to reduce high gas velocity zones and create a uniform even spray coverage across the absorber vessel to optimize SO2 removal.
Computational fluid dynamic (CFD) and scaled physical models of the planned WFGD system used velocity inlet profiles based on field data to provide better accuracy of the simulations. Modifications to the inlet ductwork and within the WFGD were made to improve the gas flow and SO2 removal efficiency. The CFD model was also used to design and optimize the spray nozzle grid and wall rings while the physical model minimized the potential for liquid pullback into the inlet ducting with designs to the inlet awning. The results of the study provided flow controls and a spray nozzle injection grid design to minimize liquid pullback while providing uniform spray coverage, which is necessary to optimize SO2 removal.
}', 9='{type=image, value=Image{width=null, height=null, url='https://www.aldenlab.com/hubfs/Projects/WFGD/wet-flue-gas-desulfurization-system-physical-model.jpg'}}', 10='{type=string, value=A scaled physical model was used to evaluate the performance of the planned WFGD by simulating the gas flow distributions through the system}', 11='{type=image, value=Image{width=null, height=null, url='https://www.aldenlab.com/hubfs/Projects/WFGD/wet-flue-gas-desulfurization-system-CFD.jpg'}}', 12='{type=string, value=The CFD model was used to optimize the slurry spray patterns to maximize the removal performance.}', 26='{type=number, value=0}', 30='{type=string, value=Read how CFD and scaled physical modeling was used to evaluate the performance of the planned WFGD and designed a spray grid for the WFGD absorber to optimize SO2 removal. }'}
A three-dimensional computational fluid dynamics (CFD) model was used to evaluate the time-averaged steady-state flow field within the Anaerobic Digester Basin.
Horizontal and vertical flow velocities within the mixing basin were provided to at select elevations within the mixing tank. The results of the CFD model demonstrated that the tank was indeed well mixed, particularly near the floor of the tank, which is critical for keeping solids well mixed, and entrained in the flow. Part of the design is to have some of the nozzles angled upward to increase mixing at higher elevations in the tank as well, which was shown to be effective in the CFD model. Velocities were presented graphically as contour plots, and elevation-averaged values were also presented.
Though not performed in this project, Alden can also include chemical and/or biological reactions in the CFD models. This can help to determine local reaction rates within the tank, concentration gradients, and what the rate-limiting factor is at any location in the tank. Time-varying simulations can also be run to study influences of different inputs in batch processes.
}', 9='{type=image, value=Image{width=null, height=null, url='https://www.aldenlab.com/hubfs/Projects/anaerobic-digester/Anaerobic-digester-CFD-nodes.jpg'}}', 10='{type=string, value=A steady-state flow field within the Anaerobic Digester Basin was evaluated with a three-dimensional CFD model.}', 11='{type=image, value=Image{width=null, height=null, url='https://www.aldenlab.com/hubfs/Projects/anaerobic-digester/Anaerobic-digester-jet-mixer-model.jpg'}}', 12='{type=string, value=Flow velocities were provided within the mixing basin to characterize the hydraulics in the basin. }', 26='{type=number, value=0}', 30='{type=string, value=Read how a CFD model helped to confirm adequate mixing in a proposed Monogram Foods Anaerobic Digester Basin, which employs KLa's K2DJM-10 jet mixing system.}'}
When an SDA unit that was showing signs of improper droplet evaporation, CFD modeling was used to predict spray and deposition patterns in an SDA reactor in order to develop a solution to improve droplet evaporation.
Background
Spray Dryer Absorbers (SDAs) are designed to remove acid gases, mainly sulfur dioxide (SO2), from flue gas streams. Atomizers are used to inject droplets of lime slurry into the SDA reaction chamber, which then evaporate and react with the sulfur dioxide in the flue gas to form calcium sulfate, a solid powder that is typically captured in a fabric filter (or baghouse). Proper evaporation of the injected slurry is critical to the performance of SDA units. When the droplets do not evaporate, the system can have decreased removal performance, exhibit deposition on the walls, and cause droplet carryover into the outlet ductwork, which can then create issues with fabric filter operation.
Work Performed
A Computational Fluid Dynamic (CFD) model of the SDA reactor was used to simulate the gas and droplet flow patterns, droplet evaporation, and wall wetting due to droplet deposition. The model was validated using temperature and moisture content field data, as well as by the comparison of the predicted wall wetting to field photographs of deposition. The model predictions were incredibly accurate and provided a unique insight into the spray patterns within the reactor. Using this information, modifications to the reactor swirl vanes and outlet hood design were made to improve evaporation and mitigate wall wetting.
Results
The new reactor modifications were implemented in the field. The client has happily reported improved SDA removal performance, the elimination of deposits on the walls, no fabric filter bag wetting, and reduced operating pressure loss—all of which result in reduced SDA operating costs.
}', 9='{type=image, value=Image{width=null, height=null, url='https://www.aldenlab.com/hubfs/Projects/Spray-Dry-Absorber/Spray-Dry-Absorber-modeling.jpg'}}', 10='{type=string, value=CFD modeling was used to evaluate design changes to a system in an environment where data cannot be feasibly obtained in the field.}', 26='{type=number, value=0}', 30='{type=string, value=Read about an SDA unit that was showing signs of improper droplet evaporation, and how CFD modeling was used to predict spray and deposition patterns in an SDA reactor in order to develop a solution to improve droplet evaporation.}'}
In response to hurricane Katrina, the US Army Corps of
Engineers decided to increase the frontal protection on four pump stations in
the greater New Orleans area. Two of the
pump stations (Bonnabel and Duncan) required the construction of wave breaks in
Lake Pontchartrain as well as additional frontal protection in the form a
T-walls. ALDEN provided wave break
design assistance and analysis for using Computational Fluid Dynamics (CFD)
tools to evaluate wave break performance. Hydraulic performance of the discharge
flow with wave breaks and extended discharge due to the T-wall installation was
confirmed with physical hydraulic models.
3-D CFD was used to evaluate the
effectiveness of several different wave break designs for reducing the height
of the wave impacting the front of the pump station. The wave spectrum used at the model
boundaries was derived from the ADCIRC model.
Model results were used to improve the wave break design with the
objective of minimizing the structure length and maximizing wave height
reduction. The models were also used to
evaluate the potential impacts of the wave breaks on the erosion and deposition
of sediment in the pump discharge canal.
Modifications derived in the CFD models were evaluated in two 1:30 scale
physical models for final design verification.
}', 9='{type=image, value=Image{width=null, height=null, url='https://cdn2.hubspot.net/hubfs/5468894/Projects/Bonnabel-Duncan-Pump-Stations/bonnabel-wave-break-phsyical-modeling-testing.jpg'}}', 10='{type=string, value=Shown is the Bonnabel pump station model that was used to evaluate impacts of wave breaks}', 11='{type=image, value=Image{width=null, height=null, url='https://cdn2.hubspot.net/hubfs/5468894/Projects/Bonnabel-Duncan-Pump-Stations/duncan-pump-station-physical-model.jpg'}}', 12='{type=string, value=Two 1:30 scale physical models were used for final design verification produced by CFD models}', 23='{type=string, value=T:HydraulicBPS Discharge T:HydraulicDPS Discharge}', 26='{type=number, value=0}'}
ALDEN conducted a comprehensive,
multi-faceted flow model study of the addition of a proposed powerhouse
(including three turbines) at the Meldahl Locks and Dam facility on the Ohio
River. Meldahl Locks and Dam are
operated by the Huntington District of the U. S. Army Corps of Engineers
(USACE) for navigation. As part of the
powerhouse design optimization, Alden studied the effect of the power house
addition on flow conditions in the approaches.
Flow patterns approaching the powerhouse were also evaluated to ensure
optimum turbine performance.
Alden designed, constructed and tested an undistorted,
1:120 scale comprehensive riverine model physical that included approximately
17,000 ft of the Ohio River. The model
was used to evaluate and minimize the impact of the hydropower project on
navigation.
In addition to the physical model, a 3D CFD model of the
powerhouse intake was coupled with a 1:40 scale model of the intake canal and
powerhouse structure to evaluate excavation requirements and ensure favorable
flow patterns at the power house intake for increased turbine life and
efficiency.
}', 23='{type=string, value=T:HydraulicMeldahl Nav T:HydraulicMeldahl Power}', 9='{type=image, value=Image{width=null, height=null, url='https://cdn2.hubspot.net/hubfs/5468894/Projects/Meldahl-Locks-and-Dam/Meldahl-locks-dam-physical-model.jpg'}}', 10='{type=string, value=A 1:120 scale comprehensive riverine model physical of approximately 17,000 ft of the Ohio River helped to evaluate and minimize the impact of the hydropower project on navigation. }', 26='{type=number, value=0}'}
The existing flood control dam at Canton, Oklahoma, was being upgraded with an auxiliary spillway to enable it to safely pass the new Probable Maximum Flood (PMF). The auxiliary spillway weir will be equipped with Fusegates, which will tip individually at predetermined water elevations to release flood water as needed. The service and auxiliary spillways together must be able to discharge a PMF of 17,000m3/s without overtopping the dam. To facilitate this, a hybrid numerical and physical hydraulic model study of the spillway system was conducted at Alden Research Laboratory.
First, a numerical model study was carried out for various approach geometry designs to investigate approach flow patterns, resulting water surface elevations throughout the reservoir and spillways, as well as flow rate splits between the two spillways. Based on the CFD results, a favorable design was selected, constructed and tested in a large-scale 1:54 scale topographic physical model. The advantage of this hybrid, integrated numerical and physical modeling approach is that each model can be used where it has its strengths: Numerous modifications of the approach channel geometry were made in a cost-effective way in the numerical model. The large-scale physical model was then used to validate the numerical results, for final modifications that brought the maximum reservoir elevation at PMF to within acceptable levels, to obtain the spillway rating curves and for Fusegate-specific tests.
The Canton Dam spillway physical model at 31 CFS
}', 9='{type=image, value=Image{width=null, height=null, url='https://cdn2.hubspot.net/hubfs/5468894/Projects/Canton-Dam-Spillway/Canton-Dam-Spillway.jpg'}}', 10='{type=string, value=The Canton Dam spillway in Canton, Oklahoma}', 11='{type=image, value=Image{width=null, height=null, url='https://cdn2.hubspot.net/hubfs/5468894/Projects/Canton-Dam-Spillway/Canton-Dam-overlay-numerical-on-physical-model.jpg'}}', 12='{type=string, value=Overlay of the physical and numerical model results}', 13='{type=image, value=Image{width=null, height=null, url='https://cdn2.hubspot.net/hubfs/5468894/Projects/Canton-Dam-Spillway/Canton-Dam-CFD-Model.jpg'}}', 14='{type=string, value=Configuration of the Canton Dam CFD Model, with mesh detail of the auxiliary spillway and in the existing service spillway area (Run 8 shown)}', 15='{type=image, value=Image{width=null, height=null, url='https://cdn2.hubspot.net/hubfs/5468894/Projects/Canton-Dam-Spillway/Canton-Dam-Physical-Model.jpg'}}', 16='{type=string, value=Canton Dam undistorted 1:54 scale topographic physical model}', 23='{type=string, value=T:HydraulicCanton Dam Spillway}', 26='{type=number, value=0}', 30='{type=string, value=Spillway upgrades to Canton Dam took advantage of hybrid modeling using integrated numerical and physical modeling to ensure its design & safety. Read how}'}
McLaughlin Whitewater Design Group was developing a new course at Coweta Falls on the Lower Chattahoochee River near Columbus, Georgia. McLaughlin hired Alden to build a scaled physical hydraulic model of the course to make sure it would perform as designed.
The whitewater course is part of an aquatic ecosystem restoration project involving the removal of the Eagle and Phenix Dam and the City Mills Dam and construction of a series of environmental, recreation, and aesthetic features. The overall goal of the project is to restore riverine and shoal habitat. The two dams will be removed with oversight by the Army Corps of Engineers to reveal natural whitewater rapids. MWDG plans to enhance the whitewater experience by adding a combination of grouted boulder structures, newly excavated channels, a tunable wave-shaper and upgraded river access.
The physical model study evaluated a number of proposed site modifications to be installed for optimization and enhancement of whitewater features within the river, including the installation of the tunable wave-shaper. The model was used to perform visual qualitative evaluations of the whitewater features. as well as to quantitatively track the water surface elevations throughout the model at different river flows and varying river tailwater elevations.
The model simulated the Coweta Falls portion of the river to a geometric scale of 1:12, and included a small portion of the Eagle and Phenix dam that will remain on either side of the river after the dam is removed and the two naturally formed channels within the modeled portion of the river. The proposed site modifications were also modeled including the channel entrance sills, invert sills, whitewater sills and tunable wave-shaper. The model was primarily tested at prototypical river flows ranging from 900 to 13,400 CFS, but was capable of flows of 20,000+ CFS. The model also included provisions for adjusting tailwater over the range of expected river tailwater elevations.
}', 9='{type=image, value=Image{width=null, height=null, url='https://cdn2.hubspot.net/hubfs/5468894/Projects/Coweta-Falls-Kayak-Course/coweta-sm.jpg'}}', 10='{type=string, value=Coweta Falls during a site visit pre-construction}', 11='{type=image, value=Image{width=3008, height=2000, url='https://www.aldenlab.com/hubfs/Projects/Coweta-Falls-Kayak-Course/DSC_0046.jpg'}}', 12='{type=string, value=The physical model during construction}', 13='{type=image, value=Image{width=1200, height=664, url='https://www.aldenlab.com/hubfs/Projects/Coweta-Falls-Kayak-Course/Coweta-Falls-Model-Evaluation-2.jpeg'}}', 14='{type=string, value=Evaluation the model during testing}', 15='{type=image, value=Image{width=1200, height=798, url='https://www.aldenlab.com/hubfs/Projects/Coweta-Falls-Kayak-Course/Coweta-Falls-Model-Evaluation.jpg'}}', 16='{type=string, value=Modifications were made to improve the hydraulics of the whitewater course}', 17='{type=image, value=Image{width=1200, height=676, url='https://www.aldenlab.com/hubfs/Projects/Coweta-Falls-Kayak-Course/AdobeStock_363956433%20(1)-1-2.jpeg'}}', 18='{type=string, value=Kayakers ready to enter the whitewater course installed on the Chattahoochee River in Columbus, Georgia}', 23='{type=string, value=T:HydraulicCoweta Falls}', 26='{type=number, value=0}', 29='{type=string, value=
Video taken during a walk through of the Physical Model
}', 30='{type=string, value=Using a 1:12 scaled physical hydraulic model, Alden tested a new whitewater course design at Coweta Falls to ensure the course would perform as designed.}'}
Alden designed, constructed and tested a ~1:7 Froude scale physical hydraulic model to evaluate the hydraulic performance of the Tarrant Regional Water District Integrated Pipeline Project Joint Cedar Creek Pump Station in accordance with the Hydraulic Institute Standards (HIS).
The pump station consists of six 66 inch tee screens and 7 vertical pumps, each with a rated capacity of 27 to 49.4 million gallons per day (mgd). The maximum total flow for the pump station is 277 mgd, which corresponds to all seven pumps operating. The design requires each of the seven pumps to be placed into a depressed pump can located in the wet well floor.
Work Performed
Baseline tests were conducted to evaluate the pump hydraulic performance in terms of vortex formation, swirl at the pump impeller, and the velocity distribution approaching the pump impeller. The tests were conducted at two water levels; the normal water surface elevation and the maximum pool elevation. The test results identified the presence of unacceptable dye cAre subsurface vortices emanating from the can walls.
Two design modifications were developed and evaluated each of which met the HIS acceptance criteria. The first design modification included can-wall roughness vanes at 10 degree intervals to dissipate the unacceptable vortices. The second design modification included an inverted torus dish installed on the can floor (under the pump suction) as well as shortening the existing vertical can vanes. The dish modification was selected as the preferred modification since it demonstrated the most streamlined flow entering the pump.
Project Highlights
Baseline design was an innovative combination of a traditional wet well configuration with recessed pump suction cans to minimize overall excavation costs.
Two design modifications were provided to the client that satisfied the HIS acceptance criteria and the most cost-effective design was selected.
}', 9='{type=image, value=Image{width=1200, height=700, url='https://www.aldenlab.com/hubfs/Projects/Tarrant-Pump-Intake/tank-and-cans.jpeg'}}', 10='{type=string, value=A physical model of seven pumps used for this pump station}', 11='{type=image, value=Image{width=1200, height=700, url='https://www.aldenlab.com/hubfs/Projects/Tarrant-Pump-Intake/wet%20well2-1.jpeg'}}', 12='{type=string, value=An innovative combination of a traditional wet well configuration with recessed pump suction cans minimized overall excavation costs}', 13='{type=image, value=Image{width=1200, height=700, url='https://www.aldenlab.com/hubfs/Projects/Tarrant-Pump-Intake/pump%20can-1.jpeg'}}', 14='{type=string, value=Detail of a pump can}', 15='{type=image, value=Image{width=1200, height=700, url='https://www.aldenlab.com/hubfs/Projects/Tarrant-Pump-Intake/model%20tank-1.jpeg'}}', 16='{type=string, value=View of the model tank}', 26='{type=number, value=0}', 30='{type=string, value=A 1:7 scale physical model looked at the performance of the Integrated Pipeline Project Joint Cedar Creek PS in accordance with HI Standards}'}
Alden’s engineers and biologists conducted extensive CFD modeling and biological evaluations to help the Holyoke Gas & Electric Department (HG&E) develop an effective downstream passage solution for endangered shortnose sturgeon at the Hadley Falls Station on the Connecticut River. The results of these studies produced engineering and hydraulic design criteria for an exclusion rack and downstream bypass. The CFD modeling examined flow conditions for several alternative rack designs, as well as the bypass discharge to ensure safe downstream passage of fish and minimal interference of upstream migrants trying to locate the entrance to a fish lift. Alden also developed conceptual designs and preliminary cost estimates for the preferred alternatives and conducted biological testing in a large laboratory flume with various configurations of bar racks and bypass entrance designs with juvenile shortnose sturgeon. Agency acceptance of the final design was obtained by HG&E after Alden completed a desktop analysis of total downstream passage survival using the laboratory bypass efficiency data and theoretical estimates of turbine survival.
}', 9='{type=image, value=Image{width=null, height=null, url='https://www.aldenlab.com/hubfs/Projects/Hadley-Falls/Hadley-Falls-close-up.jpg'}}', 10='{type=string, value=A view of Hadley Falls}', 26='{type=number, value=0}', 11='{type=image, value=Image{width=null, height=null, url='https://www.aldenlab.com/hubfs/Projects/Hadley-Falls/Hadley-Falls-Aerial.jpg'}}', 12='{type=string, value=An aerial view of the project area}'}
On startup, the air quality control system (AQCS) at Deerhaven Generating Station was not able to meet its guarantees for SO capture and reagent usage. Also, the material handling systems were not operating properly, forcing the units to shutdown. To identify and solve these problems, Alden built three scaled physical flow models to simulate the complex gas-solids interactions in each component of the Turbosorp system. The design solutions that were found during model testing were implemented in the field with great success. As a result, the Deerhaven AQCS was able to meet all the performance guarantees within its contract, and has since been host to a dry scrubbers users group as an example of how these systems should operate.
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During periods of spill, Cabinet Gorge Dam was generating total dissolved gas (TDG) concentrations in excess of water quality standards. Through a series of feasibility studies, design evaluations, retrofits and/or modifications, Alden engineers worked to help Avista Corporation meet their FERC licensing requirements for the hydroelectric project located in Idaho on the Clark Fork River.
In early studies, the Alden team performed a 1:50 scale physical hydraulic model study to investigate re-commissioning of diversion tunnels used during construction of the project as bypass tunnels to pass spill flows at lower TDG levels than are generated during spillway operation. Studies revealed that the reduction in TDG afforded by the bypass tunnels was less than originally expected.
Additional feasibility studies were conducted to evaluate two alternatives for TDG reduction. One idea was the creation of off-stream “gas stripping” channels downstream of the dam, which ultimately proved to be fish passage un-friendly. Ultimately, modification of the existing spillway crest was found to be most feasible.
Full hydraulic and structural engineering services from feasibility through design and construction have been completed for the modifications to five of the eight spill bays in order to reduce TDG. Construction plans and specifications were prepared, and documentation for submittal to FERC was produced. Alden also provided construction technical support.
In addition to the work done to reduce TDG, Alden engineers also performed several structural projects for Cabinet Gorge Dam:
A Stoplog Deployment Crane was designed and fabrication-level drawings developed for the deployment crane system for lifting 10-ton stoplogs. The steel frame was designed to allow assembly and disassembly at each of the eight spill bays. Performance specifications for the 15-ton top running hoist were also provided
The FERC Supporting Technical Information (STI) Documents were reviewed and updated for Section 6—Hydrology/Hydraulics and Section— Stability/Stress Analysis.
In further compliance measures, the development of a fish trap design in the project tailrace for the expedited transmissivity of ESA listed bull trout past the project was supported. This effort also used the 1:50 scale model for initial site selection studies. Alden also provided a fisheries and hydraulic engineering representative on a “panel of experts” who advised on the best approach for trap site selection and design. Computational Fluid Dynamics (CFD) modeling of the project tailrace was performed to confirm satisfactory location and performance of the selected trap design. The CFD model developed for the fish trap studies also confirmed compatibility of the TDG mitigation measures with the fish trap operations and to guide future development of the TDG mitigation.
}', 9='{type=image, value=Image{width=null, height=null, url='https://www.aldenlab.com/hubfs/Projects/Cabinet-Gorge-Dam/cabinet-gorge-dam-safety-engineering-design.jpeg'}}', 10='{type=string, value=A view of the Cabinet Gorge Spillway}', 11='{type=image, value=Image{width=null, height=null, url='https://www.aldenlab.com/hubfs/Projects/Cabinet-Gorge-Dam/Cabinet_Gorge.jpg'}}', 12='{type=string, value=Looking downstream from the spillway structure}', 13='{type=image, value=Image{width=null, height=null, url='https://www.aldenlab.com/hubfs/Projects/Cabinet-Gorge-Dam/Alden-Engineers-Cabinet-Gorge-Dam.jpeg'}}', 14='{type=string, value=Site visit by Alden Engineers}', 15='{type=image, value=Image{width=1182, height=500, url='https://www.aldenlab.com/hubfs/assets/images/billboards/Physical-Modeling.jpg'}}', 16='{type=string, value=A 1:50 scaled physical model not only informed TDG mitigation options, but was also used for fish passage studies.}', 26='{type=number, value=1}', 29='{type=string, value=
Dive in Deeper
Read more about Total Dissolved Gas at High Head Dams in this three-part blog series.
}', 30='{type=string, value=This project involved structural engineering services from feasibility through design and construction for TDG modifications to five of the eight spill bays at Cabinet Gorge Dam.}'}
The Mathis Dam Spillway project highlights Alden’s integrated hydraulic and structural engineering services in which there was close collaboration between hydraulic modeling, hydraulic design, and structural design experts.
Alden used numerical modeling and physical modeling to evaluate the discharge capacity and pressure distribution on the surface of the Mathis Dam spillway, and as a result, Alden developed a spillway shape modification that eliminated the negative pressures on the spillway. These spillway modifications were designed and detailed and approved by FERC in May 2018.
Project Summary
Mathis Dam is an Ambursen-style dam built in 1915, using a slab-and-buttress type construction. It's Existing spillway does not follow an Ogee profile. As a result, there were concerns with negative pressures on the spillway face and the peak reservoir stage during the Probable Maximum Flood (PMF).
Alden used numerical modeling to assess potential changes in the spillway capacity and reservoir levels resulting from spillway gate replacement. Numerical modeling showed that surface pressures were low enough to lift the spillway slabs and adversely affect spillway performance.
Based on the results of the numerical modeling, a 1:15 physical model was constructed. The physical model was used to confirm negative pressure results and to develop modifications (ventilation step) to eliminate the negative pressures.
Alden provided structural design, plans, and documentation for the spillway modifications. The design was submitted to FERC and approved with no comments.
Construction for the spillway modifications is scheduled for fall 2019
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One chromatography column developer was having challenges scaling up an existing design to a larger version. Our team worked with the manufacturer using Computational Fluid Dynamics (CFD) to understand the reasons for the reduced performance. CFD modeling was used to pinpoint reduced performance when moving from existing, small scale units to upscaled columns.
In the work we peformed, we were able to validate a CFD model and calibrate porous dispersion coefficients for the existing column. Moving to the larger column, however, initial results could not be reproduced with CFD. It was found that for the upscaled column, the synthetic textile mesh that forms the boundary between the distributor and the packed bed had deformed under the packing pressure of the column, such that the distributor was pinched off, and the outer radius of the packed bed was starved of flow. Computing the deformation of this mesh around the radial rib supports—and including this effect in the CFD simulations—showed that the upscale experimental results could be reproduced. The solution was verified in subsequent experiments.
Through a recommended design change, we were able to show that the high level of performance typical of the existing column could be reproduced in the upscaled column. The improved design is also able to be packed more consistently, and operates at a lower pressure loss than the original.
}', 9='{type=image, value=Image{width=null, height=null, url='https://www.aldenlab.com/hubfs/Projects/Chromatography-Scale-Up/Chromatography-equipment.jpg'}}', 10='{type=string, value=Chromatography (the separation of chemical components) is an important aspect of a number of drug production processes. }', 26='{type=number, value=0}', 30='{type=string, value=Running CFD models for existing and upscaled chromatography columns helped determine the cause of reduced performance and subsequently produced a redesign.}'}
Alden's Modeling of the Smithland Lock and Dam powerhouse project is an example of coordinated use of Computational Fluid Dynamics (CFD) and physical modeling to resolve performance, navigation, constructability and cost issues in the design of a low head hydropower project. A 1:120 scale physical model together with a two dimensional computational river and sediment transport model were used to evaluate the impacts of American Municipal Power's project on lock navigation and sediment deposition. A separate 1:60 scale physical model was used together with CFD to optimize the intake channel.
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Designed to simulate the Mississippi River’s depth, sediment, and flow, the Lower Mississippi River Physical Model is used by researchers, scientists, and engineers to improve our understanding of the lowermost Mississippi River and to study how it responds to modification.
The expanded small scale physical model is constructed from 216 foam panels measuring 5 ft. x 10 ft. long. This model lives in the LSU Center for River Studies where it enables researchers to study sediment diversion projects used to divert river water and sediment to replenish and help sustain the vanishing coastal wetlands in the region.
The Lower Mississippi River Physical Model encompasses the area bounded by the Terrebonne Ridge on the west, approximately RM 175, the North Shore of Lake Pontchartrain on the north, to the Chandeleur Islands on the east, and to the 250 foot contour line in the Gulf of Mexico. The mobile bed model is a distorted scale of 1:6,000 in the horizontal direction and 1:400 in the vertical direction.
The model is nearly as large as an Olympic-size swimming pool and was constructed with a toleramce of 1mm.
The model is machined from foam blocks that are then assembled on the model support platform. Innovative construction techniques and high precision measurement techniques were developed for the model construction.
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The time lapse video shows how the model was constructed. The model serves as both a scientific test bed and as an exhibit.
The Littoral Combat Ship (LCS) concept boat was studied for the U.S. Navy. The LCS is intended to operate in coastal areas of the globe, and the ship will be fast, highly maneuverable, and geared to support mine detection/elimination, anti-submarine warfare, and surface warfare, particularly against small surface craft.
Alden performed a 1:5 scale physical model study for the air intake and the uptake for one of the 2 gas turbine enclosures. The main objectives of the model study were to provide velocity distributions and pressure loss data within the intake, uptake, and enclosure as well as the mixing of the enclosure cooling air with the turbine exhaust gas and the exhaust plume flow characteristics.
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Alden performed design studies and field startup testingof PSE’s Upper and Lower Baker Dams Floating Surface Collector (FSC) systems. The FSC concept is well-suited for downstream fish passage in deep reservoirs with large variations in water level. Guide nets stretching from the water surface to reservoir bottom funnel migrant fish to the FSC, which provides attraction flow through high-flow submersible pumps. As flow is drawn into the FSC, dewatering screens funnel the fish to holding pens for transportation around the dam.
ALDEN conducted a 3-D Computational Fluid Dynamics (CFD) model study of the reservoir hydraulics, guide nets, and FSC to optimize the location, orientation, and discharge of the Upper Baker FSC. Alden then developed a physical model of a preliminary version of the FSC dewatering screens and pumps to improve pump performance and screen channel hydraulics. After construction, ALDEN provided comprehensive field startup testing of the hydraulic performance of the FSC, balanced the dewatering screens, and provided critical operations information to PSE.
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Alden conducted CFD and physical modeling studies to support the design of the new power plant at the Taweelah Smelter Project in the United Arab Emirates.
A CFD model of the effluent aeration basin was used to simulate flow and develop modifications in order to provide uniform flow within the chambers and ensure optimum mixing.
Physical hydraulic models of the cooling tower, seawater intake, and outfall basin were used to investigate pump approach flow hydraulics. Because hydraulic phenomena which can adversely affect pump performance were found in all three station designs, design modifications were developed that provided acceptable approach flow conditions for the range of the station's operations.
}', 9='{type=image, value=Image{width=1366, height=768, url='https://www.aldenlab.com/hubfs/Projects/Taweelah/Taweelah-outfall-overview-iso.jpg'}}', 10='{type=string, value=Isometric View of the Outfall Model Construction}', 11='{type=image, value=Image{width=1366, height=768, url='https://www.aldenlab.com/hubfs/Projects/Taweelah/Taweelah-Pump-Bays-Overview.jpg'}}', 12='{type=string, value=Overview of the Pump Bays}', 13='{type=image, value=Image{width=1366, height=768, url='https://www.aldenlab.com/hubfs/Projects/Taweelah/Taweelah-cooling-tower.jpg'}}', 14='{type=string, value=View of the Cooling Tower Model During Testing}', 15='{type=image, value=Image{width=1366, height=768, url='https://www.aldenlab.com/hubfs/Projects/Taweelah/Taweelah-test-conditions.jpg'}}', 16='{type=string, value=Detail of the Model During Testing}', 26='{type=number, value=0}', 30='{type=string, value=CFD and physical modeling studies supported the design of the new power plant at the Taweelah Smelter Project in the United Arab Emirates.}'}
Alden designed, constructed, and tested two 1:20 scale physical hydraulic models of the new 2-mile long surge protection barrier and associated gate bypass structures that will protect the city of New Orleans from surges generated by a 100-year storm. A model of a typical section of the surge barrier was used to optimize the scour protection on the protected side of the floodwall. A model of the bypass gate, which allows ship traffic through the barrier, was tested to determine the forces acting on the gates during the storm's receedance, as well as to measure wave heights, pressure, and vibration at the gate structure during hurricane conditions. Both models utilized a wave generation system to create hurricane conditions during testing
}', 9='{type=image, value=Image{width=1021, height=680, url='https://www.aldenlab.com/hubfs/Projects/Inner-Harbor/Inner-Harbor-Aerial.jpg'}}', 10='{type=string, value=An aerial view of the project location}', 11='{type=image, value=Image{width=1000, height=750, url='https://www.aldenlab.com/hubfs/Projects/Inner-Harbor/Inner-Harbor-Mid-Construction.jpg'}}', 12='{type=string, value=One of the 1:20 scale models in mid-construction}', 13='{type=image, value=Image{width=2816, height=2112, url='https://www.aldenlab.com/hubfs/Projects/Inner-Harbor/Inner-harbor-model-shakedown.jpg'}}', 14='{type=string, value=1:20 scale models utilized wave generators to create hurricane conditions during testing}', 26='{type=number, value=0}', 30='{type=string, value=A 2-mile long surge protection barrier and gate bypass structures meant to protect New Orleans were modeled using two 1:20 scale physical hydraulic models}'}
As part of Austin, Texas, Waller Creek has historically had problems with flooding, erosion and water quality. The addition of a proposed storm water tunnel was evaluated for hydraulic capacity, air entrainment and flow patterns in the tunnel entrances.
Testing was conducted on an undistorted, 1:33 scale comprehensive physical model of the Waller Creek Tunnel. The main morning glory spillway, two secondary spillways and the tunnel discharge were modeled. The model was used to evaluate flow patterns and flow splits approaching the morning glory spillway, the entrainment of air at the spillway and the pressure losses in the system. Modifications were derived that split the flow more evenly and improved the performance of the spillway and tunnel.
In addition to the physical model, a 3D numeric model using Flow-3D was developed to examine the flow patterns into the morning glory spillway and the flow patterns entering the tunnel from the downstream laterals. Modifications were developed in CFD and tested in the physical model to minimize the number of modifications required to the physical model to arrive at acceptable flow patterns.
}', 9='{type=image, value=Image{width=null, height=null, url='https://cdn2.hubspot.net/hubfs/5468894/Projects/Waller-Creek-Tunnel/DSC02699.jpg'}}', 10='{type=string, value=A close up of the inlet on the 1:33 scale comprehensive physical model}', 11='{type=image, value=Image{width=1100, height=733, url='https://www.aldenlab.com/hubfs/Projects/Waller-Creek-Tunnel/Waller-Creek-Tunnel-Inlet-1.jpg'}}', 12='{type=string, value=Another view of the inlet structure}', 13='{type=image, value=Image{width=1200, height=788, url='https://www.aldenlab.com/hubfs/Projects/Waller-Creek-Tunnel/Waller-Creek-Tunnel-Model-Outlet.jpeg'}}', 14='{type=string, value=Overview of the Waller Creek Tunnel model outlet structure}', 15='{type=image, value=Image{width=1200, height=800, url='https://www.aldenlab.com/hubfs/Projects/Waller-Creek-Tunnel/Waller-Creek-Model-View.jpg'}}', 16='{type=string, value=View of the physical model set up within the lab}', 23='{type=string, value=T:HydraulicWC Tunnel T:HydraulicWallerCreek }', 26='{type=number, value=0}', 30='{type=string, value=Read how Alden designed, constructed and tested an undistorted 1:33 scale comprehensive physical model of the proposed storm water tunnel at Waller Creek.}'}
To support design upgrades to the existing Primary Settling Tanks (PSTs) of the 26th Ward Waste Water Treatment Plant (WWTP) for the New York City Department of Environmental Protection (DEP), Alden conducted a Computational Fluid Dynamics (CFD) model
study to assist in evaluating the hydraulic and sedimentation performance of: 1) A new Flow Distribution Structure (FDS), 2) A new influent channel that services each PST with new ports and target baffles, and 3) New PST effluent
weirs and troughs. The study included developing three-dimensional (3D) CFD
models and conducting a series of simulations to verify flow and grit
distributions favorable for optimal performance.
A
series of FDS designs were modeled for: flow and grit distributions to
each operating tank; water surface elevations at inflow chamber of FDS; water
surface elevations upstream of the troughs; the relationship between the water
surface elevation and flow rates; and weir setting and optimization of the FDS
design. The best design was chosen for
grit and flow splits.
The PST design was modeled for flow and grit
distributions through ports using: various influent channel configurations;
flow and grit distribution within the PSTs and performance in conjunction with
the existing baffle boards, target baffles, vertical baffle wall, flow
distributors, symmetrical and asymmetrical layouts of inlet piping to influent
channel ports, downstream weirs and troughs; prediction of the water surface
elevation in the FDS compartment; and estimation of flow and grit distributions
of other PSTs. The results of the model
indicated possible design improvements, which were then implemented and tested
in the model. Afterwards, the PST weirs
and troughs were modeled in details to ensure favorable hydraulic performance.
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As part of project/dam surrender and removal efforts at the Saccarappa Hydroelectric Project (Saccarappa), Alden provided S. D. Warren Company d/b/a Sappi North America (Sappi) with the final design and fish passage analysis for nature-like fishways in the upper channels at Saccarappa Falls. The final design involves reshaping the existing bedrock channel into a form that is more conducive to fish passage while mimicking the morphology of a natural bedrock channel. Alden provided agency consultation while developing the design and will ultimately provide construction support. The proposed design complements a proposed double Denil fishway over the lower portion Saccarappa Falls designed in partnership with Acheron Engineering.
Alden conducted a site visit and reviewed existing geotechnical, hydrologic, site constraints, and other site data prior to developing the final design for the nature-like fishways. The final design was achieved by way of iteration between a 3D CAD representation of the proposed bathymetric surface and a 3D computational fluid dynamics (CFD) model. Expected small-scale roughness of the channel bed was incorporated into the CAD surface through a novel texturizing technique based on a high resolution laser scan of the existing bedrock surface. The CFD model was used to simulate proposed conditions at four discrete design flow rates. Hydraulic data output by the CFD model (e.g., depth and velocity) informed subsequent improvements of the proposed surface in CAD. Sappi and agency review and feedback was provided at 30%, 60%, 90%, and final drafts of the design. Fish passage effectiveness of the final design was analyzed by Alden biologists and engineers using USFWS’s SMath models developed for assessing velocity impediments by estimating fatigue, survivorship, and work. Alden will provide engineering consultation and inspections to support project construction.
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Starting in 2009, Alden has been working with a confidential nuclear power facility to determine the feasibility of monitoring cooling water intake flow rate. The work began with a feasibility study of available equipment and/or techniques that can be used to monitor the intake flow rate. A comprehensive list of available technologies that can be used to monitor intake flows was developed, along with brief descriptions of each technology. The list of available technologies or methods that were generated was evaluated to determine those feasible for implementation at the facility. Detailed assessments of the technologies selected for further evaluation were then conducted and were provided along with listed advantages and disadvantages associated with implementation. Alden then recommended a technology believed to be best suited for use at the facility compared to the other technologies further evaluated.In support of the feasibility study conclusions,
Alden has conducted pump performance testing in 2012, 2013, 2014, and 2015. A total of 10 circulation water pumps have been tested using the dye dilution method to determine flow rate. By injecting a known amount of dye upstream, and allowing for sufficient mixing, the dye concentration downstream will yield the flow rate (mass balance calculation). The dye dilution testing was conducted to determine the actual circulating water flow rates at different pump speeds and tidal conditions in order to address environmental regulatory questions about water usage.
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Clay Boswell Energy Center Unit 4 is a coal fired station owned by Minnesota Power. The plant had a need to reduce flue gas temperatures upstream of their NID emissions control system for removing SO2 from the flue gas stream—while the plant remained online. This created a design limitation for the injection system since the nozzles would have to fit through the duct ports, and the lances would only be supported by the duct penetration, not internally.
Our engineers calculated the quench water requirements to achieve the desired gas temperature cooling and then selected candidate spray nozzles for the system. The sulfuric acid dewpoint temperature was also calculated for design considerations. Remaining above the acid dewpoint is important to avoid corrosion of the ductwork. Then a computational fluid dynamic (CFD) model of the scope of ductwork was created, and prepared using inlet boundary conditions representative of the plant flue gas profiles. Based on the desired gas flow pattern for optimal spray injection, required residence time for evaporation, and access in the field to the ductwork for lance installation and quench system piping, a location for the quench system was selected. The candidate spray nozzle injection characteristics, such as droplet size distribution, spray pattern, and droplet velocity, were input into the model and used to evaluate various nozzle arrangements. The final arrangement provided the target gas temperature reduction, within the desired uniformity, and minimized wetting of surfaces.
ALDEN worked closely with plant personnel to design a quench system that could be installed while the plant remained online · ALDEN used CFD modeling to simulate numerous quench spray nozzles types and arrangements to determine the best option · ALDEN designed a cost-effective functional design for the quench system
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Shiller Station, a 150 MW coal and oil fired station owned by Public Service Company of New Hampshire, was experiencing high bag wear in their fabric filter (FF) unit that was causing unscheduled outages for repair. Using computational fluid dynamic (CFD) modeling to simulate the ash laden gas flow through the fabric filter system, causes of the bag wear were identified, and modifications were developed to stop the issue. The plant has installed the recommended flow controls, and have reported that not only is the bag wear issue resolved, they also gained over 1-inwg of pressure savings from the modifications.
Work Performed
Using a CFD model of the complete fabric filter system, including connecting ductwork, inlet and outlet manifolds, and each FF compartment with bags, the cause of the high bag wear rate was identified—poor gas flow distributions in the inlet manifold and entering each compartment. Modifications were developed to create more uniform gas velocities through the inlet ductwork and entering each compartment, and to reduce the gas velocity magnitude impacting the bags. The final design created smooth flow throughout the connecting ductwork and manifolds. The design also eliminated the high velocity jets that were impinging on the bags.
Results
The plant has reported that they are no longer experiencing premature bag wear and ash deposition in the ductwork has been minimized. As a result of this modification, the plant also reported a gain of over 1-inwg due to the pressure loss savings.
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Our team and Air Consulting Associates (ACA) were was contracted by Southern Environmental Inc. (SEI) for the planned Electrostatic Precipitator (ESP) upgrades for a large US utility. Our team performed the upfront physical flow model studies while ACA proivded technical support throughout the entire project.
An ESP operates by electrically charging ash particles in the fluegas and then attracting the charged particles onto collecting plates which are then rapped to send the ash to the hoppers where it can safely be removed from the system. For optimum system operation, the distribution of the gas velocity must be very uniform entering the ESP to maximize the collection efficiency of the ESP and to minimized particulate emissions. Upstream duct fallout of ash particles and the flue gas distribution into the ID fans are also important components of ESP operation that must be considered to inhibit premature outages.
Work Performed
Physical flow modeling techniques were used to develop and optimize duct and ESP flow controls and ash handling devices to achieve best performance targets for ash removal. The connecting ductwork from the existing air preheaters to the rebuilt ESPs were also included in the studies to provide flow controls designs to optimize air preheater performance. The model simulated the field gas velocities, pressure losses, and ash particulate transport and removal.
Results
Not only did we design a cost-effective design for the flow controls and perforated plates to provide optimal ash removal, our recommended design achieved the ICAC EP-7 targets for uniformity of flue gas velocities at the inlets to the first collecting fields and at the outlets of the last collecting fields to maximize particulate removal efficiency
Each of the three units passed their respective performance test guarantees after the recommendations from the physical flow model had been implemented.
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Alden simulated the planned Kansas City Power and Light Iatan Unit 2 (POWER Magazine’s 2011 plant of the year) Selective Catalytic Reduction Systems (SCR) to maximize the NOx removal efficiency. An SCR operates by injecting a reagent, typically ammonia (NH3), into the flue gas stream, and then catalyzing a reaction to convert the NO2 and NO3 into nitrogen and water. For optimum system operation, the distribution of the NOx, reactant, gas velocity, and temperature must be very uniform entering the catalyst to maximize the reaction and prolong catalyst life. Upstream collection of large particle ash (LPA), and the distribution of fine ash at the inlet face of the first catalyst are also important components of SCR operation that must be considered to inhibit premature outages caused by pluggage.
Work Performed
Physical and computational flow modeling techniques were used to develop and optimize duct and SCR flow controls, ammonia injection grid, mixing devices, and ash handling devices to achieve best performance targets for NOx removal. The new connecting ductwork from the retrofit SCR to the existing air preheaters was also included in the study to provide flow controls designs to optimize air preheater performance. The models simulated the field gas velocities, temperatures, pressure losses, NOx concentrations, NH3 injections, and ash particulate transport and removal.
}', 9='{type=image, value=Image{width=600, height=399, url='https://www.aldenlab.com/hubfs/Projects/Selective-Catalytic-Reduction-System-Design/KC-Power-and-Light-Iatan-Unit-2.jpg'}}', 10='{type=string, value=The Selective Catalytic Reduction Systems (SCR) for the Kansas City Power and Light Iatan Unit 2 (POWER Magazine’s 2011 plant of the year) was simulated to maximize the NOx removal efficiency.}', 11='{type=image, value=Image{width=3456, height=2305, url='https://www.aldenlab.com/hubfs/Projects/Selective-Catalytic-Reduction-System-Design/KC-Power-and-Light-Iatan-Unit-2-physical-model-2.jpg'}}', 12='{type=string, value=A combination of computational and scaled physical modeling was used to simulate, design, and optimize the operating performance of the SCR system}', 13='{type=image, value=Image{width=630, height=429, url='https://www.aldenlab.com/hubfs/Projects/Selective-Catalytic-Reduction-System-Design/KC-Power-and-Light-Iatan-Unit-2-CFD-model-2.jpg'}}', 14='{type=string, value=recommended design achieved the target uniformity of NH3:NOx, gas temperature, and gas velocity at the first catalyst layer to maximize removal efficiency}', 15='{type=image, value=Image{width=3456, height=2304, url='https://www.aldenlab.com/hubfs/Projects/Selective-Catalytic-Reduction-System-Design/KC-Power-and-Light-Iatan-Unit-2-physical-model.jpg'}}', 16='{type=string, value=A cost-effective design for the AIG and SCR systems provided optimal NOx removal and catalyst life}', 17='{type=image, value=Image{width=2048, height=1536, url='https://www.aldenlab.com/hubfs/Projects/Selective-Catalytic-Reduction-System-Design/KC-Power-and-Light-Iatan-Unit-2-design.jpg'}}', 18='{type=string, value=An upstream ash collection device was developed to remove large particle ash, which is known to cause catalyst pluggage, and simulated the distribution of expected fine ash entering the first catalyst layer, which showed uniform loading.}', 26='{type=number, value=0}', 30='{type=string, value=Read how computational and scaled physical modeling simulated the planned SCR and helped design performance devices to optimize the NH3:NOx, fluegas velocity, temperature, ash, and pressure losses through the SCR system. }'}
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Marsulex Environmental Technologies (MET) contracted Alden to re-engineer a heat recovery system for flue gas reheat at Great River Energy Coal Creek Generating Station. The goal of the system was to ensure that no condensation would be present in the flue gas system as it enters the stack and vents to ambient conditions. The reheat was provided through the use of multiple available heat sources within the existing facility. A Computational Fluid Dynamics (CFD) Model Study was also peformed to simulate the operation of the system.
With the available heat from various locations in the plant analyzed, our flow experts designed the final system to remove ambient air from the boiler house and to heat that air through contact with the economizer ductwork prior to the re-heat fans. Two separate CFD models—that included convective and radiative heat transfer—were then used for final evaluation of the design. The first model included the Reheat Air System and Wet Flue Gas Desulfurization inlet ductwork. The second model was for the reheat ducting and mixing chamber, in which the reheated air mixed with the flue gas.
CFD results showed that the project goals for pressure drop, temperature rise, and mixing of ambient air with flue gas were all met.
}', 9='{type=image, value=Image{width=1200, height=585, url='https://www.aldenlab.com/hubfs/Projects/Utility-Power-Flue-Gas-Reheat-System-Design/Utility-Power-flue-gas-reheat-design-cfd.jpg'}}', 10='{type=string, value=The performance goals of a redesigned heat recovery system for a power plant exhaust system were confirmed with CFD.}', 26='{type=number, value=0}', 30='{type=string, value=Read how Alden redesigned a heat recovery system for a power plant exhaust system and confirmed performance goals with CFD}'}
Clay Boswell Station Unit 4, a 535 MW coal fired station owned by Minnesota Power, planned to retrofit a new SO2 removal system, and needed design through flow modeling to ensure successful operation of the system. Alden used a scaled physical flow model to simulate coal ash deposition in the connecting ductwork and distribution manifold of the planned emissions control system. A modification to the manifold ductwork and new internal flow controls were developed to mitigate areas of ash piling. The plant installed the recommended flow controls and has experienced no major ash piling.
Work Performed
Alden developed a scaled physical model of the planned emissions control system and associated ductwork. The model used velocity inlet profiles based on field data to improve the accuracy of simulations. Initial tests identified one area in particular where high levels of ash deposition were observed in the distribution manifold. Duct modifications and flow control designs were investigated to mitigate the deposition. The final design eliminated the ash deposition.
Results
After several months of operation with the recommendations implemented, plant personnel conducted a walkdown of the system and confirmed that the ductwork and distribution manifold were free of ash piling.
Project Highlights
The testing simulated ash transport and deposition in a scaled cold flow model
A cost-effective design for the DFGD inlet ducting system was provided
Plant feedback after operation confirmed the recommendations were effective
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