Effect of leading-edge cavitation of a hydrofoil on the near-field sound pressure

Leading-edge (LE) cavitation of a blade is a frequent occurrence in hydraulic machinery during off-design operation, often accompanied by unsteady flow and high-amplitude noise. To quantitatively assess the noise caused by cavitation, the Powell vortex sound theory was refined to consider the non-uniform distribution of sound speed and the compressibility effect resulting from mass transfer near the vapor–liquid interface. This led to the development of a new model capable of visualizing the spatiotemporal distribution of sound pressure in cavitating flows. Unsteady simulations were conducted on a hydrofoil at various cavitation numbers and were validated using experimental data. Three different types of sound sources were identified: unbalanced vortex force, non-uniform kinetic energy, and compressibility effect, with the compressibility effect being the dominant source under LE cavitation conditions. The sound pressure during cavitation exhibited dramatic fluctuations over time and was closely related to the spatial position, particularly peaking during the transient moments of LE cavitation break-off, with the highest sound pressure observed near the vapor–liquid interface. There was a strong correlation between sound pressure and vapor volume fraction, suggesting that cavitation noise is a result of the dynamic evolution of cavitation. As the cavitation number decreased from 2.02 to 1.04, the sound pressure level substantially increased, with an increment of up to 17 dB. This paper presents a method for simulating and visualizing near-field sound pressure considering cavitation, providing valuable insights into the relationship between LE cavitation and sound pressure levels.