Separation-Induced Water Level Oscillations in Cooling Tower Pump Intake Structures

Recent experience has shown that relatively minor interaction between regions of flow separation can have a significant impact on water level oscillations in pump intake structures. Intake structures that appear to follow established design guidance have exhibited periodic water level oscillations of up to 1 meter or more. This can have a negative impact not only on the approach flow to the pumps but also on the operating conditions such as submergence and NPSH. This paper presents the results of several recent physical model studies that identified large-scale water level oscillations. A sensitivity analysis has been conducted, and common features between intakes that appear to contribute to the oscillations are presented along with relatively simple remedial measures. Recommendations on how to avoid oscillating water levels are presented and discussed.