CFD SIMULATION OF FLOW IN MODEL PUMP SUMPS FOR DETECTION OF VORTICES

摘要

Demand is high for reducing the size of sumps to reduce construction costs of urban drainage pump stations. As a result of the reduction in size, undesirable vortices like air-entrained and submerged vortices are apt to appear in the sumps because of increases in flow velocities. Based on criteria in the JSME Standard, the appearance of such vortices is not permissible for conventional sumps, experiments with scale models usually have been done to assess the performance of these sumps. However, those tests are expensive and time-consuming, and therefore, alternative CFD methods for evaluating sump performance have been expected. The JSME Standard "Standard Method for Model Testing the performance of a Pump Sump" was revised in March 2005 by a committee of the Turbomachinery Society of Japan. The committee also established a benchmark for flows in model sumps applying ten CFD codes. The calculated results were compared for flow patterns, locations of vortices, and their vorticity. Although the simulated flow patterns near the bell are almost all the same, the calculated values of the local vorticity were much more different among the various codes. It was confirmed that the existence of air-entrained and submerged vortices could be predicted by applying a newly developed identification method for vortices.