Undercurrent: The Alden Blog

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Industrial fluid dynamics insights


3 Benefits of Sediment Transport Modeling
Walking from building to building in late March, one of our engineers noticed some interesting patterns in puddles of melting snow. As the water ran off the snow piles, it carried with it fine sediment—a perfect, small-scale example of what sediment transport looks like. Naturally, he took out his phone and captured a few quick videos to share. Sediment transport is a naturally occurring process, the results of which we see all around us. On geomorphic time scales, the shapes of our rivers, coastlines, even canyons and mountains are made in large part due to erosion, sediment transport, and deposition. All pretty cool things. Now, if we talk about this in terms of an engineering time scale, sediment transport can mean very different things. Sediment can be beneficial, and sediment can have adverse impacts on infrastructure. To our clients, scaled physical and numerical modeling of sediment transport is typically looked at for one of three reasons. Improving O&M Costs Simply put, sediment and man-made machinery can be a problematic mix that can damage equipment or imped process flows. In the example of ...

Simulating Plasma Physics with CFD in Honor of Star Wars Day
PLASMA. It’s the fourth state of matter, and is generated when gas molecules get so hot that they can’t hold on to their electrons anymore and become charged particles. When that happens, electrical effects become increasingly important to the physics of the flow. In other words, as plasma gets hotter, it becomes one with the (Lorentz) force. This all sounds pretty exotic, but plasma is more common than you might think. In fact, plasma is the most abundant state of ordinary matter in the universe – it is what stars are made of. The only thing that may rival the mass of plasma in the universe is of course… DARK MATTER. Here on earth, there are plenty of examples of plasma also: Aurora Borealis, lightning, fluorescent lights, plasma displays in TVs, and spark plugs just to name a few. Here at Alden, we’ve been doing some work with plasma lately, but unfortunately for you dear reader, due to proprietary information agreements, we are not at liberty to discuss these supremely awesome projects. Instead, since Star Wars Day ...

Computational Fluid Dynamics: Examining Guinness Bubbles
We know we aren’t the first to ponder the phenomenon of watching bubbles sink when a pint of Guinness is poured. Is it magic within the stout that causes this defiance again the laws of physics? Or is there something else going on with this tasty elixir? And really, what good is keeping all our scientific knowledge bottled up if we can’t pop the top off it and apply it to more social pursuits? In the spirit of St. Patrick’s Day, we did just that. Bubbles are the circulation engine More studies than you realize have been conducted about the sinking bubble phenomenon that occurs within a freshly poured pint of Guinness. In one recent study, three Irish mathematicians investigated the shape of the glass. In their flow simulations, they found the rise or fall of the bubbles is directly related to the shape of the glass into which the beer is poured. A glass with a smaller base (like a stout glass) is going to result in a higher bubble density near the middle, causing entrained bubbles ...

Deep Breath: The Impact of Alden's Work on Power Plant Emission Controls
Each year, National Engineers Week falls on the week of February 22 — George Washington’s actual birthday—in part to commemorate a man who is considered the nation’s first engineer. But not only that, the week is meant to highlight the contributions engineers have made to the world as we know it. Just think about that for a minute as you read this on a display screen that wouldn’t exist if not for engineering ingenuity. The list of accomplishments engineers have made to our society and the history books is massive. From our perspective, we can highlight many areas in which Alden engineers have contributed to the annals of history. From testing airplane propellers and missile ballistics to the work on dam safety and fish passage and protection programs, we’ve had a hand in shaping our world throughout our 125 years of continual operation. But trying to find a singular project to discuss for this week? That task is nearly impossible. So, that’s when I asked Dave Anderson, Senior Vice President and Chief Technology Officer to weigh in.  Besides wanting to ...

Preventing Ice Build-Up on Wet Stacks
Preventing Ice Build-Up on Wet Stacks
Ice chunks the size of Volkswagens falling from the sky! Sounds like a Hollywood special effects scene in an action movie, right? Unfortunately, this is a real-life danger that can occur just about anywhere, but especially on wet stacks running in cold weather. It should go without saying that ice falling from a tall stack can have damaging, even catastrophic effects on process equipment and personal safety. But with some situational knowledge and attention to design details, you can prevent ice build-up on wet-stacks before it becomes a problem.  Icing and the Downwash Effect Essentially, to operate an ice-free wet stack system, you need to properly handle the discharge of wet flue gas during prolonged exposure to cold temperatures. Units running at low loads on cold, windy days can see a dangerous icing develop from an effect called plume downwash. Plume downwash occurs when a cross-wind at the top of the stack deflects the plume from its vertical path. This phenomenon is more likely to happen when flue gas exits at a lower velocity—like, for example, when units aren’t running ...

Data Management Matters
The Hidden Costs of Data Storage in an Enterprise –– Over the years, end users have expressed the general concern that data management isn’t worth their time.  In all fairness, this misconception is understandable due to the inexpensive and continually decreasing cost of consumer-grade disk drives.  Ultimately, firms should work towards changing that mindset because the true cost is far greater in an enterprise’s production environment.  To identify the associated costs, I have prepared the following analysis of raw storage consumption, performance impacts, and resources needed to store data in a locally-hosted Microsoft Windows server environment. Raw Storage Needs for a 1GB File in a Sample Production Environment FIGURE 1 Referencing Figure 1, a 1GB file not only consumes raw storage across multiple storage platforms (e.g. local storage, backup volumes, etc.), but at a higher quantity than in its original form.  This is a direct result of high availability and fault tolerance achieved when using a Redundant Array of Independent Disks, better known as RAID.  One requirement for this essential feature with ...

NUPIC 2017 Vendor Meeting
The 26th Annual NUPIC Vendor Meeting was held June 21st and 22nd at the Hilton Riverside New Orleans and hosted by Entergy.  This was Alden’s 4th time attending the event (see last year’s blog post for more information about the NUPIC organization).  The meeting is an important opportunity for utility auditors and representatives to meet with suppliers outside of a NUPIC audit.  As Oscar Limpias, the VP of Nuclear Oversight at Entergy noted in his keynote address, “vendor performance and the partnership between vendors and utilities is critical to the future of nuclear generation”. A variety of topics were presented, including decommissioning, new plant construction, small modular reactors, equipment reliability, commercial grade dedication (CGD) and the revised CGD guidance, cyber-security considerations for suppliers, counterfeit items and delivering the nuclear promise. Copies of the presentations can be found on the NUPIC site (https://nupic.com/NUPIC/Home/HotTopics.aspx).  A common theme throughout the two days was the current state of nuclear power and its future.  While NUPIC, itself, saves each utility an estimated $1 million per year, there are more opportunities to reduce cost in relation to ...

Takeaways from HydroVision 2017 in Denver, Colorado, July 27-29
HydroVision International is the largest gathering of hydro professionals worldwide. Over 3,000 hydro professionals and over 300 hydro related product and service providers were on the exhibit floor. The participants are from 51 countries. The event highlights perspectives on the role of hydropower, explores issues affecting the hydropower industry, covers issues and concerns affecting hydro resources, publicizes current market opportunities and challenges, and facilitates development of a vision to meet challenges and to ensure sustainable development. Alden is active in supporting the hydro industry, with physical hydraulic modeling, 3D and 2D numeric modeling, fish passage design and testing. We attend Hydrovision every year, and participate in the exhibit, as well as technical conference and training sessions. I was able to meet with most of our dams and hydro clients and teaming partners. The attendance from the private power producers, utilities, consulting companies and equipment manufacturers were adequate but there was clearly less participation from the federal government, especially from the U.S. Army Corps of Engineers (USACE). I observed increased energy and optimism in developing renewable and small hydro with a ...

Eel Shining to Locate Upstream Passage Routes
Searching for eels is an activity reserved for those who like to stay up late. Only under the cover of darkness is one able to have the best chance to find these nocturnal fish. Surveying for American eels, Anguilla rostrata, with lanterns at night or “shining” is a common method to document their presence in rivers across eastern North America. Juvenile American eels often congregate downstream of obstacles that block their upstream movement (eels are catadromous fish, meaning adults spawn in saltwater and the young move into freshwater to rear and mature before returning to the marine environment to complete the reproductive cycle). Hydroelectric dams are common impediments to upstream migrants along river courses. Finding optimal areas to establish passage routes for eels to move upstream is a primary reason to shine for eels.  Eels, being a fish, become more active as the water temperature rises. When the temperature is above 10 degrees C, which generally occurs from May to October in New England, eels of all ages and sizes become more active. The recently born glass eels, (so called ...

Energy Dissipating Devices: Total Dissolved Gas Production at High Head Dams - Part 3
In Parts 1 and 2 of this series we talked about production of total dissolved gas (TDG) at high head dams, and the use of air supply systems to mitigate cavitation damage to spillways and spillway modifications. In this part, we’ll discuss the structural designs used to reduce TDG during flow release from spillways. Super-cavitating roughness elements, or baffle blocks for short, are designed to break up flow as water travels down a spillway. Depending on the placement of the blocks on the spillway surface, they can also help spread out the jet of water laterally as it exits the spillway, resulting in a larger impact area on the tailrace. Why does this help reduce TDG production? As we discussed in Part 1, dissolved gas supersaturation in the tailrace is a function of how long it takes the bubbles from the aerated flow to reach the water surface. By spreading out the impact zone of the spillway jet, and decreasing the amount of energy the jet has, plunge depth of the jet is reduced and the aerated flow can rise ...