For the visualisation of the occurrence of submerged vortex in hydraulic pump sump model tests, the present studies showed that the simulated flow should be higher than that corresponding to Froude number simulation. A "k-Froude" velocity simulation is used in this study. The upper limit of the model simulation for the occurrence of the submerged vortices was observed to be when the ratio of viscous forces to surface tension forces is the same for the prototype and the geometrically similar model. If the corresponding swirl angles of the flow in the inlet ducts measured at Froude scaling velocity is less than 5 degrees, the occurrence of submerged vortices generally does not exist for model flow tested below the critical model test flow velocity defined by the similarity of the ratio of Weber Number and the Reynolds number of the flow filed in model and prototype.
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