Numerical assessment of the cavitation-induced impeller-volute interaction in a centrifugal pump

The steady-state effects of cavitation on the performance of centrifugal pumps are well known. However, the interactions between cavity dynamics and the noncavitating flow unsteadiness have not been fully explored yet. In the present work, such unsteady phenomena are investigated focusing on cavitation-induced impeller-volute interactions. An improved cavitation model is used to generate a numerical dataset covering three working conditions of a commercial centrifugal pump. For each operating point, a range of cavitation numbers is considered, spanning from cavitation inception to the developed cavitation regime. After that, a frequency-based postprocessing methodology is applied to assess the unsteady flow features, quantifying the roles of blade passage fluctuations and cavity-induced dynamics. Pressure, velocity, and bubble size fluctuations are analyzed at the impeller-volute interface, and bubble radius fields at the volute wall are used to predict potential erosion zones beyond the reach of classical Eulerian mixture models. The results point to a transition from blade-passage–dominated to cavity-dominated dynamics near the 3% head-drop condition. After this transition, non-periodic fluctuations arise, amplifying tongue-induced excitations and producing maximum pressure fluctuations. Furthermore, impeller outlet flow deflection is identified as a mechanism driving these enhanced fluctuations. These findings provide new insight into the coupled unsteady behavior of cavitating flows and suggest design strategies for improved flow guidance under cavitating conditions. • Cavitation increases flow unsteadiness in centrifugal pumps • A numerical dataset is built to assess the cavitation-induced unsteadiness • Coupling between impeller-volute interactions and cavity dynamics is found • An improved cavitation model is used to capture detailed bubble behaviour • Unsteady bubble dynamics are observed at the volute tongue