Numerical and Experimental Analysis of Cavitating Flow in a Low Specific Speed Centrifugal Pump With Different Surface Roughness

Three-dimensional (3D) simulations with ansys cfx 16.1 as well as measurements of the cavitating flow in a low specific speed centrifugal pump (nq = 12 min−1) are performed for different operation conditions and varying surface roughness. Surface roughness is considered by wall functions in the flow simulations. Good agreement between measured and calculated head is achieved for noncavitating flow. Net positive suction head (NPSH3%) rises toward overload due to incidence, flow separation, and vapor zones at the volute tongue. The NPSH3% rise is slightly higher for rough walls according to measurements and significantly overestimated by the wall function approach, irrespective of the roughness level in the simulation. A low-Reynolds number approach at the volute tongue leads to a more accurate prediction of NPSH3% than wall functions, at the cost of high computational effort.