Experimental study on the similarity of flow in pump sump models

To study the similarity law in the flow of pump sump, especially on the critical submergence for both air entraining vortex and submerged vortex, three model pump sumps are constructed with geometrical similarity. Changing the flow rate and water height, the condition when sump vortex occurs is studied in each model. On the air entraining vortex, there are two critical lines of submergence, one is in proportional to the flow rate or velocity at bell inlet, the other is almost independent from flow rate. The former may be the effect of Froude number, but the later is not clear. On the submerged vortex, the line is not clear in the smallest model. Comparing the coefficients of above lines, the kinetic similarity is got at the same velocity condition, not Froude number similarityor Reynolds number similarity.