Wichita Water Utilities ASR River Intake and Pump Station CFD and Physical Hydraulic Model Study

CLIENT: Wichita Water Utilities

The Wichita Water Utilities ASR River Intake and Pump Station project is to be located on the right bank of the Little Arkansas River and consist of nine isolated pump bays with a 12.75 cfs submersible pump installed in each bay. The firm capacity of the pump station will be 102 cfs. The overall objectives of the model investigations were to evaluate potential sediment movement in the vicinity of the screens, assess solid deposition in the individual pump bays, evaluate bank stability, determine if the initial design of the pump station provided adequate approach hydraulics and uniform flow to the pumps, and develop modifications to the initial design to improve the approach flow hydraulics to the pumps.

Working with the Wichita Water Utilities and Burns & McDonnell, NHC conducted CFD modeling and determined that the pump station will have minimal effect on flow patterns, sediment deposition, and erosion of the Little Arkansas River for medium and high river flows. At low river flows, the pump station will likely change the natural flow pattern downstream of the intake due to a major portion of the river flow being withdrawn into the intake. Sediment transport will occur in the river; however, the impact of the pump station on scour and deposition is expected to be minimal.

A 1:5 scale physical model study demonstrated that the initial design was susceptible to high pre-swirl of the flow approaching the pumps due to non‑uniform flow entering the pump bays. Unacceptable surface and subsurface vortices formed in the vicinity of the pumps. In addition, the flow velocities entering the pumps were outside the specified criteria. 

Modifications were developed in the physical model to correct the performance problems. With the modifications installed, the flow was more uniform entering the pump bays, and flow pre-swirl, surface and subsurface vortices, and the velocity distribution approaching the pump impeller were all within acceptable limits.