Abstract
In this study, cavitation flow around a hydrofoil and its radiated hydro-acoustic fields were numerically investigated, with an emphasis on the effects of viscous flux vectors. The full three-dimensional unsteady compressible Reynolds-averaged Navier–Stokes equations were numerically solved. The mass transfer model was adopted to model phase changes between liquid water and vapor. To resolve the numerical instability problem arising from the rapid changes in local density and speed of sound of the mixture, the preconditioning and dual-time stepping methods were employed. The filter-based turbulent model was applied to resolve the unstable cavitation flow field more accurately. In splitting the viscous terms, three approaches for dealing with viscous flux vectors were considered: the so-called viscous lagging, full viscous, and thin-layer models. Radiated hydro-acoustic waves were predicted by applying the Ffowcs Williams and Hawkings equations. The effects of the viscous flux vectors on the predicted flow fields and its radiated noise were then examined by comparing the hydro-dynamic forces, velocity distribution, volume fraction, far-field sound directivities, and sound spectrum of the three approaches. The results revealed that the thin-layer model can provide predictions as accurate as the full viscous model, but required less computational time.
Highlights
Cavitation typically occurs when the local pressure in a flow field drops below the vapor pressure of the liquid, and forms vapor cavities or gas bubbles
By following the procedure from a previous study (Kim et al [16]), the Ffowcs Williams and Hawkings (FW-H) equation can be rewritten in a form appropriate to account for flow noise, due to cavitation flow, over an acoustically compact stationary body, as follows p0 ( x, t) =
Prior to the detailed investigation of the predicted unsteady cavitation flows around the hydrofoil using the above viscous flux models, the averaged properties of the predicted flow field, using current numerical methods, are compared to the numerical results obtained from the large eddy simulation (LES) and experiments, to confirm the validity of the current numerical methods
Summary
Cavitation typically occurs when the local pressure in a flow field drops below the vapor pressure of the liquid, and forms vapor cavities or gas bubbles. This fact and the understanding that the propeller cavitation is one of most contributing factors to flow noise sources of commercial ships necessitates the improved understanding of numerical and physical issues related to cavitation flows and its radiated noise For this purpose, in this study, the effects of viscous flux vectors on the generation, development, and extinction of cavitation from a hydrofoil, and the radiated hydro-acoustic flow noise, is numerically investigated with three different approaches to treating viscous flux vectors: viscous lagging, thin-layer, and full viscous models. In. Section 3, the governing equations and the numerical methods are described, with detailed explanations concerning the treatment of viscous flux vectors in association with the preconditioned implicit pseudo-time marching scheme. The predicted results of the cavitation flow field and its radiated acoustic field are presented and analyzed, with emphasis placed on the effects of viscous flux vectors according to the types of viscous flux models employed
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