Scale Effects in Pump Sump Models

Experiments were conducted using one full‐sized and two reducedscale models of a pump sump to geometric scales of 1:2 and 1:4 to determine whether scale effects distort the predictive ability of hydraulic models of pump sumps with such large scale ratios. Possible scale effects on vortexing, pipe swirl, inlet losses, and air ingestion due to air‐drawing vortices have been examined using the experimental results. No significant scale effects on free‐surface vortexing were evident in the tested ranges. Pipe flow swirl and inlet losses were seen to exhibit some scale effects. The air‐core vortices encountered were generally weak with very low air withdrawals. Within the accuracy of measurements of air‐withdrawal rates, the model did not indicate any gross underprediction of air withdrawals.