Abstract
In this study, cavitation flow of hydrofoils is numerically investigated to characterize the effects of turbulence models on cavitation-flow patterns and the corresponding radiated sound waves. The two distinct flow conditions are considered by varying the mean flow velocity and angle of attack, which are categorized under the experimentally observed unstable or stable cavitation flows. To consider the phase interchanges between the vapor and the liquid, the flow fields around the hydrofoil are analyzed by solving the unsteady compressible Reynolds-averaged Navier–Stokes equations coupled with a mass-transfer model, also referred to as the cavitation model. In the numerical solver, a preconditioning algorithm with dual-time stepping techniques is employed in generalized curvilinear coordinates. The following three types of turbulence models are employed: the laminar-flow model, standard k − ε turbulent model, and filter-based model. Hydro-acoustic field formed by the cavitation flow of the hydrofoil is predicted by applying the Ffowcs Williams and Hawkings equation to the predicted flow field. From the predicted results, the effects of the turbulences on the cavitation flow pattern and radiated flow noise are quantitatively assessed in terms of the void fraction, sound-pressure-propagation directivities, and spectrum.
Highlights
Cavitation is the phenomenon wherein vapor bubbles are formed from liquid water when the local pressure of the fluid decreases below the vapor pressure
Shen and Dimotakis (1990) conducted a water-tunnel test with NACA 66 hydrofoil to investigate the influence of surface cavitation on the associated hydrodynamic forces
It is reported that the cavitation number associated with the origin of the tip-vortex cavitation exhibits a complex dependence on the Reynolds number and air contents, whereas the tip-vortex trajectory is independent of any physical parameters
Summary
Cavitation is the phenomenon wherein vapor bubbles are formed from liquid water when the local pressure of the fluid decreases below the vapor pressure. Pressure fluctuation on a propeller surface and cavitationvolume changes were predicted and were analyzed using a potential-based vortex lattice method These results were used to model noise sources by employing the acoustic analogy proposed by Lighthill (1952, 1954). Among these issues, the effects of turbulences on cavitation due to a hydrofoil and its radiated hydro-acoustic wave are numerically investigated using a hybrid method wherein a more suitable numerical method is applied sequentially in each computation phase. The cavitation flow is numerically predicted using computational-fluid-dynamics technique based on a homogeneous mixture model, and the cavitation noise is predicted by employing an acoustic analogy to the predicted flow data.
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