River Intake Pump Station
CFD Model Study

CLIENT: Lake Oswego Tigard Water Partnership

A CFD model study was conducted to support the design of the River Intake Pump Station by the Lake Oswego Tigard Water Partnership to withdraw up to 38 million gallons per day (mgd) of water from the Clackamas River, Oregon.  As designed, the 41-foot long and 21-foot wide pump station includes four operating pumps and a standby pump. River water enters the structure through three gates, downstream of T-screens, and water flows to the bays through a longitudinal channel with a control gate.  

As a sub-consultant to Black & Veatch, NHC conducted three-dimensional CFD modeling of the pump station for the initially proposed design, which showed pre-swirls of about 12, significantly higher than the limit set by the Hydraulic Institute of 5. The pre-swirls were reduced by two alternatives: a) constructing columns at the entrance of each pump bay along with wall fillets and a center splitter; and b) attaching a vane/grating basket to the bell of each operating pump. Both alternatives included reducing the pump bay width to twice the pump bell diameter. The design team selected the second alternative to minimize the possibility of sediment accumulation around the columns of the first alternative.