Cavitation in pumps is a well-known phenomenon that occurs when local static pressure approaches vapor pressure for the working fluid. The flowing fluid under this condition changes its phase from liquid to gas and form bubbles. These bubbles travel along with flowing fluid and reach a zone with relatively high pressure. As the pressure builds up, the size of the bubble reduces and at some stage bubbles collapse generating very high pressure locally that could damage the metallic blade surfaces. Extensive research activities are going to investigate cavitation phenomenon. At Kirloskar Bothers Ltd, a mixed flow pump was investigated thoroughly for its cavitation performance. The newly introduced Cavitation module in a CFD package, CFX, was used to predict the cavitation phenomenon for this pump. The performance of the pump was predicted first by using single-phase module. The overall performance prediction of the pump matched well with the measured results. The solver was switched over to account for cavitation study using multiphase flow phenomenon. The numerical approach brings out formation of vapor and growth of its volume fraction as the suction pressure is dropped. The paper describes both of these approaches and presents results in the form of impact of cavitation on overall performance of the pump. The vapor bubble formation and its volume fraction growth with reduction in suction pressure are brought out using numerical approach.

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