The paper presents full 3D numerical simulations and experimental investigations of the cavitating flow through three axial inducers. These inducers are identified by the tip blade angle at the leading edge β1T=8, 10, and 13deg. The numerical and experimental investigations were carried out at the LEMFI laboratory (Laboratoire d’Energétique et de Mécanique de Fluides Interne) of the ENSAM-Paris center (Ecole Nationale Supérieure d’Arts et Métiers). A review of the cavitating regime modeling and the cavitation homogeneous model used for this paper’s calculations is first presented. The numerical model is based on a combination of the multiphase flow equations with a truncated version of the Rayleigh-Plesset model predicting the complicated growth and collapse processes of bubbles. The mass transfers due to cavitation are source/sink terms in continuity equations of the liquid and vapor phases. The cavitation model also features a solution methodology which implicitly couples the continuity and momentum equations together. The main results are presented for the inducers at a range of flow rates and cavitation numbers: (1) Experimental results concerning: (i) the overall performances: Pressure head coefficient and efficiency versus flow rates; (ii) critical cavitation number (5% and 15% of drop) versus the flow rate; (2) Numerical results concerning: (i) the overall performances; (ii) the numerically investigated water vapor volume fraction distributions and other CFD results, which enable us to explain the cavitating behavior for these inducers; (iii) the location and sizes of the blade cavity and backflow vortex. Finally, the comparisons between experimental and simulated results on the overall performances, cavity sizes and cavity location are discussed. A qualitative agreement between experimental and predicted results was found for two inducers for a range of flow rates. The head breakdown in the simulations started at a different cavitation coefficient than that in the experiment.

The paper presents full 3D numerical simulations and experimental investigations of the cavitating flow through three axial inducers. These inducers are identified by the blades leading edge angle at the periphery β1T = 8°, 10°, 13° and are thus noted as Inducer 8°, Inducer 10° and Inducer 13°. They have the same tip and hub diameters. The numerical and experimental investigations were carried out at the LEMFI-Paris laboratory. This enabled us to explain the cavitating operation for off-design conditions. In Part I of this paper we describe the design methodology adopted for the inducers and which is deduced from literature and in house experience. Then the main experimental results are presented for the studied inducers at a range of flow rates and cavitation numbers concerning: • The overall performances: pressure head coefficient and efficiency versus several flow rates. • Critical cavitation number (5% and 15% of drop) versus the flow rate. In Part II of this paper, a review of the cavitating regime modeling and the cavitation VOF model used for this paper’s calculations is firstly presented. The numerical approach is based on a combination of the VOF technique with a truncated version of the Rayleigh-Plesset model predicting the complicated growth and collapse processes of bubbles. The cavitation model also features a control volume finite element discretization and a solution methodology which implicitly couples the continuity and momentum equations together. The numerical results of Part II concern: • The overall performances. • The numerically investigated water vapor volume fraction distributions and other CFD results, which enable us to explain the cavitating behavior for these inducers. • The location and sizes of the blade cavity and backflow vortex. Finally, the comparisons between experimental and simulated results on the overall performances, cavities sizes and cavities location are discussed. A good agreement between experimental and predicted results was found for a range of flow rates. The head breakdown in the simulations started at a different cavitation coefficient than that in the experiment.

The goal of this paper is to compare the experimental performance within the cavitating regime for three axial inducers identified by the leading edge angle at the periphery of the blades, β1T = 10, 13, 15° and which will be noted as inducer 10°, inducer 13° and inducer 15°. The three-dimensional flow was analysed using the CFD code ‘CFX-BladeGENRELSP +’. This enabled us to explain the unstable and cavitating operation for off-design conditions. A brief bibliographic review of the cavitating regime and the outlines of the design method for the three axial inducers that were studied are first presented. Then, for these inducers; the main results are presented: 1) Overall performance—head coefficient and critical cavitation number (5 and 15 per cent drop) vs. the flow rate; 2) Vibration behaviour vs. the flow rate and the suction pressure; and 3) CFD results, which enable us to explain the unstable experimental behaviour for these inducers.

In this work, experimental and three-dimensional numerical simulations are pursued with the intent of elucidating the differences that the hub shape has on three inducer performances and on other important engineering properties in cavitating and non-cavitating regimes. Two inducers have a cylindrical hub and the third one has a conical hub. They are noted as BH inducer (big hub), SH inducer (small hub), and CH inducer (conical hub). These machines were designed with the goal to reduce the amount of cavitation and vibration, on the one hand, and to improve the overall performance, on the other hand. Both sets of experimental and numerical data suggest that the cavitating and non-cavitating performances are affected by changes in the hub shape. The hub configuration and cavitation numbers considered give rise to various cavitation structures on the suction side of the blades, characterized — at some flow rates — by recirculating flow regions and backflow vortices. The results show the relative superiority of the CH inducer through the critical cavitation coefficient of 5 per cent, even if this inducer is very unstable for all flow rates. It was also found that the BH inducer is the most stable and that for a 15 per cent head drop, the three inducers have quite the same performances. The main experimental and numerical results presented here concern the overall performances, especially the hydrodynamic mechanism of head drop and the visualization of three-dimensional flow structures. We also present the vibratory behaviour versus the flow rate and the suction pressure. The computational three-dimensional flow in non-cavitating regimes enabled us to explain the unstable and cavitating operation for off-design conditions. The numerical computation in cavitating flows is carried out using the computational fluid dynamics (CFD) software CFX-TASCFlow2.12, which cavitation model was validated on our BH inducer.