Numerical Investigation into Effects of Viscous Flux Vectors on Hydrofoil Cavitation Flow and Its Radiated Flow Noise

Abstract

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.

Numerical Investigation of Tip Vortex Cavitation Inception and Noise of Underwater Propellers of Submarine Using Sequential Eulerian–Lagrangian Approaches

“…In a flow field where the large-scale cavitation structure occurs due to a decrease in the cavitation number, the molecules on the bubble surface are sufficiently far away for one another; thus, the molecular force is negligible. Then, the critical pressure being a function of the only temperature equals the vapor pressure, which is why the cavitation flows, such as sheet and cloud cavitation, have been successfully predicted with the Eulerian methods based on the RANS solver combined with the homogeneous mixture model [34][35][36][37][38][39][40]. However, the Eulerian method has difficulty in accounting for the water quality effect because the critical pressure varies with the initial nuclei size.…”

Editorial for Special Issue: Underwater Acoustics, Communications, and Information Processing

“…Kim et al numerically investigated the effects of viscous flux vectors on hydrofoil cavitation flow, dynamically to characterize and model the radiated flow noise in [6], to resolve computational complexity and numerical instability problems. Their work justified the conclusion that the thin-layer model could provide predictions as accurate as the full viscous model, but required less computational time.…”

A Numerical Study on the Distribution and Evolution Characteristics of an Acoustic Field in the Time Domain of a Centrifugal Pump Based on Powell Vortex Sound Theory

“…However, it was difficult for the experimental method to identify the acoustic source accurately and analyze the coupling between flow and acoustic fields, by comparison, the numerical simulation approach was an ideal method to solve these issues. With the improvement of the Lighthill equation, a hybrid numerical method combining Lighthill acoustic analogy theory with Computational Fluid Dynamics (CFD) was widely used for flow-induced noise calculation [8][9][10][11]. According to the hybrid method, when the flow field simulation was completed, the wall pressure fluctuation in time domain was extracted and transformed into dipole acoustic source, then the noise signal in frequency domain was obtained.…”