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In this study, a numerical analysis was carried out to investigate the effects of blade thickness on hydraulic performance and cavitation phenomenon of a mixed-flow pump. The three-dimensional Reynolds-averaged Navier-Stokes equation, which was discretized using the finite volume method, was applied to solve a steady-state analysis. For cavitation analysis, the Rayleigh-Plesset equation was applied to calculate the transition between liquid and vapor phases. The hydraulic performance of a mixed-flow pump changes depending on the blade thickness and was systematically analyzed under various operating conditions. Blade thickness was defined as a blockage, and the cavitation coefficient was considered to express the suction performance. Cavitation characteristics were analyzed for each blockage in relation to the vapor volume fraction. The amount and pattern of vapor were different for each blade thickness case. Furthermore, in this paper, detailed flow analyses that consider the angle of incidence are presented and discussed. To verify the numerical analysis results, an experimental test was conducted at specific points. [ABSTRACT FROM AUTHOR]

Unsteady cavitating turbulent flow around a twisted hydrofoil was analyzed to illustrate the physical mechanism of the cavitygenerated pressure fluctuations. The numerical simulations of cavitating flow were based on the Partially-Averaged Navier-Stokes (PANS) method and a mass transfer cavitation model. The validity of PANS model has been evaluated and confirmed in cavitation simulations by present authors using three different cases, 2D hydrofoil (Ji et al. 2012 [37]), 3D hydrofoil (Ji et al. 2013 [31]) and marine propeller (Ji et al. 2012 [38]), which shows that the PANS model with f = 0.2 and f = 1 can obtain more accurate estimates of unsteady cavitating flows with large-scale fluctuations at a reasonable cost. In present paper we intended to shed light on the physical process responsible for the pressure fluctuations excited by cavitation. The cavity volume was analyzed to illustrate the relationship between the cavitation evolution and the pressure fluctuations. The results show that the cavity volumetric acceleration curve tracks remarkably well with the main features of the time-dependent pressure fluctuations except for the high frequency component. Thus, the cavity volumetric acceleration is the main source of the excited pressure fluctuations by cavitation. It is noted that the cavitation induced pressure fluctuations are transmitted along the suction surface of the hydrofoil and are synchronized with those on the pressure surface at the midplane of the twisted hydrofoil. Further, the pressure fluctuations on the pressure surface decrease towards the center from both the leading and trailing edges of the hydrofoil, with a minimum at 60% chord length from the leading edge. [ABSTRACT FROM AUTHOR]

Cavitating flow is usually formed on the surface of a high-speed underwater object. When the object moves near the free surface at high speed, the cavitation signature becomes a main factor to be overcome by the sensors of a military satellite. This paper studies the free surface effect on the ventilated cavitation process. The governing equations are Navier-Stokes equations based on a homogeneous mixture model. The multiphase flow solver used here relies on an implicit preconditioning scheme in curvilinear coordinates. The cavitation model used is a new cavitation model developed by Merkle et al. (2006). Computations of free surface effects were carried out with a NACA0012 hydrofoil to enable comparisons with experimental data presented in the literature. Calculations were then performed considering the ventilated cavitation process, including the effect of a noncondensable gas with free surface effect. [ABSTRACT FROM AUTHOR]

This paper describes the influence of geometrical parameters on the hydrofoil performance in non-cavitating and cavitating flows. The two-phase incompressible Navier-Stokes solver is used to compute the hydrofoil performance in two operating conditions. The new hydrofoil useful for performance improvement is obtained through the optimization design with RSM and the application of nose-drooping geometry. In the optimization design with the response surface model between hydrofoil performance and hydrofoil geometry, it is observed that the design concept of maximum lift-to-drag ratio is appropriate for the improvement of hydrofoil performance. The application of nose-drooping design concept results in the increase of hydrofoil performance in non-cavitating and cavitating flows. [ABSTRACT FROM AUTHOR]