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This paper presents three-dimensional numerical simulations and experimental investigations of cavitating flow through an axial inducer. Particularly, this work focuses on the influence of radial tip clearance on cavitation behavior. Numerical analysis was carried out on two different configurations: first, the inducer was modeled without taking tip clearance into consideration. Later, the inducer was modeled with nominal tip clearance and some modifications of this. It was found that radial tip clearance has a significant influence on the overall inducer performance in the non-cavitating regime because of the small size of the inducer. Moreover, the effects of radial tip clearance are strong in inducer cavitation behavior. Numerical results and experimental data with nominal tip clearance were compared in cavitating and noncavitating regimes and these were discussed. The cavitation model used for calculation is based on a single-fluid multiphase flow method, assuming thermal equilibrium between phases. It is based on the classical conservation equations of the vapor phase and a mixture phase, with mass transfer due to cavitation appearing as a source and a sink term in the vapor mass fraction equation. Mass transfer rates are derived from the Rayleigh-Plesset model for bubble dynamics.

This work presents the results of numerical simulation of unsteady cavitating flow through a two ebladed axial inducer. First, the analysis was carried out in a blade cascade, this twoedimensional simplified model, obtained from the studied axial inducer, was used as a test case. Later, the numerical simulations were extended to the original three-dimensional inducer. All numerical calculations were realized in cavitating flow regime. Initially, the results were obtained in steady state, and then in unsteady state. The main purpose of this study is to explore the local cavitation instabilities, such as alternate blade cavitation and rotating blade cavitation, which can appear in this type of devices when they work under certain operating conditions. The numerical results show that the fluid flow in the axial inducer is altered by the emergence of the cavitation. These vapor regions are formed, firstly near to the leading edge of each blade. The behavior of the cavitation depends on the operating conditions of the inducer, mainly by the flow rate and the suction pressure. The numerical simulation was performed using a commercial code based on a cellecentered finite evolume method. The cavitation model used for calculations assumes a thermal equilibrium between phases. It is based on the classical conservation equations of the vapor phase and a mixture phase, with mass transfer due to the cavitation appearing as a source and a sink term in the vapor mass fraction equation. The mass transfer rate is derived from a simplified RayleighePlesset model for bubble dynamics.