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.