Accuracy Assessment of RANS Predictions of Active Flow Control for Hydrofoil Cavitation (original) (raw)

Cavitation Control on Hydrofoils

– The purpose of this study is to design a passive controller on the hydrofoil, CAV 2003, to decrease and control the size of the cavitating bubble around the hydrofoil forming of the pressure drop in a specific area near the hydrofoil surface. For the purpose, a novel idea is presented here by a numerical simulation. In this idea, an appendage is located on the hydrofoil wall to decrease the size of the bubble. The location of this appendage is important to make a good condition to decrease the bubble size. Secondly, the size and height of the appendage have a significant effect on the flow around the hydrofoil and consequently select a wrong size and height can have an adverse effect. The characteristics of the numerical method, based on the cavitating bubble behaviour, are time dependent, pressure based, and finite volume. The set of Navier Stokes equations are supposed to be incompressible. Additionally, to capture the turbulent boundary layer near the hydrofoil surface, RNG k-ε model is used. The first part of this paper is allocated to verification the accuracy of the numerical simulation. The second part is the presentation on the effects of the passive controller, including the shape of the appendage and its location.

Numerical Modeling of Unsteady Cavitating Flows around a Stationary Hydrofoil

International Journal of Rotating Machinery, 2012

The objective of this paper is to evaluate the predictive capability of three popular transport equation-based cavitation models for the simulations of partial sheet cavitation and unsteady sheet/cloud cavitating flows around a stationary NACA66 hydrofoil. The 2D calculations are performed by solving the Reynolds-averaged Navier-Stokes equation using the CFD solver CFX with thek-ωSST turbulence model. The local compressibility effect is considered using a local density correction for the turbulent eddy viscosity. The calculations are validated with experiments conducted in a cavitation tunnel at the French Naval Academy. The hydrofoil has a fixed angle of attack ofα=6° with a Reynolds number of Re = 750,000 at different cavitation numbersσ. Without the density modification, over-prediction of the turbulent viscosity near the cavity closure reduces the cavity length and modifies the cavity shedding characteristics. The results show that it is important to capture both the mean and fl...

Numerical Modeling of Cavitating Flows Around Hydrofoils

2014

Abstract: This paper present a study of using a proposed finite element model to predict cavitating flow motions around two dimensional hydrofoils. The proposed model solves the governing equations of momentum and mass conservation including advection, pressure and shear stress terms. To describe turbulence influences around the hydrofoil the Prandtl-Kolgomorov model is included. The cavitating conditions are modeled through a mixture model involving liquid and vapor flows. The water vapor fraction is evaluated using a transport equation with source and sink for evaporation and condensation. The finite element model uses linear spatial polynomials to approximate the variables, a characteristic scheme to approach the non-linear advection terms and non-reflecting boundary conditions for the open outlet sides of the domain. Numerical experiments are performed for cavitation numbers 0.9 and 0.5 considering the NACA 0015 hydrofoil profile. The model is able to predict the essential featu...