Abstract
To provide theoretical basis for cavitation noise control, the cavitation evolution around a hydrofoil and its induced noise were numerically investigated. A modified turbulence model and Zwart cavitation model were employed to calculate the flow field and predict the cavitation phenomenon accurately. Then, the acoustic analogy method based on the Ffowcs Williams-Hawking (FW-H) equation was applied to analyze the cavitation-induced noise. Seven cavitation numbers were selected for analysis. Acoustic power spectral density (PSD) and acoustic pressure were investigated to establish the relationship between cavitation number and their acoustic characteristics. It was indicated that as cavitation number decreases, cavitation cycle length gets shorter and the magnitude of acoustic power spectral density increases dramatically. One peak value of acoustic power spectral density induced by the extending and retracting of leading-edge cavitation can be obtained under sheet cavitation conditions, while under cloud cavitation, two peak values of acoustic power spectral density can be obtained and are induced by superposition from leading-edge cavitation and trailing vortex.
Highlights
Cavitation mainly occurs in the location where the local pressure of the liquid drops below the threshold value at a specified temperature
The filter-based turbulence model (FBM) and Zwart cavitation model were employed to calculate the flow field and accurately predict the cavitation phenomenon, while the acoustic analogy method based on the Ffowcs Williams-Hawking (FW-H) equation was applied to analyze the flow-induced noise with different cavitation numbers
The results indicate that the distance from locations of peak value in specific times were 0.2–0.4 C away from cavitation growth and collapsing points, which corresponds with the analysis above
Summary
Cavitation mainly occurs in the location where the local pressure of the liquid drops below the threshold value at a specified temperature. Huang [8] studied the turbulent vortex–cavitation interactions in transient sheet and cloud cavitation phenomena Their analysis of the vorticity transport equation revealed a strong correlation between the cavity and vorticity structure. Sanghyeon Kim [17] investigated the effects of cavitation-flow patterns of hydrofoils, with an emphasis on turbulence models, and corresponding radiated noise was analyzed. The present study analyzes different acoustic characteristics of noise induced by the cavitation flow around an NACA0015 hydrofoil through numerical methods. The filter-based turbulence model (FBM) and Zwart cavitation model were employed to calculate the flow field and accurately predict the cavitation phenomenon, while the acoustic analogy method based on the FW-H equation was applied to analyze the flow-induced noise with different cavitation numbers. The control measures can be improved to be more specific and effective
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