Loading noise induced by cavitating flow and its simplified model prediction

Abstract

This study employs a computational fluid dynamics approach in combination with acoustic analogy to investigate the loading noise characteristics induced by cavitating flow around a NACA66 (MOD) hydrofoil. The Large Eddy Simulation coupled with the Schnerr-Sauer cavitation model is used to capture the transient motion behaviour of the cavitating flow, which agrees well with experimental observations. The study covers three typical states of cavitation: sheet cavitation (σ = 1.44), sheet/cloud transition cavitation (σ = 1.29), and cloud cavitation (σ = 0.83). The study demonstrates that the energy of the loading noise source is concentrated in the middle-frequency band for sheet cavitation, while it is concentrated in the low-frequency band for cloud cavitation. The cavitation instability promotes loading noise to generate drastic fluctuation and even several extreme impulses, which are directly related to the processes of cloud formation and cavitation multistage shedding. Finally, a simplified model for calculating the loading noise is proposed, and its errors and equivalence are evaluated. The model can effectively predict the loading noise induced by cavitating flow and enable decoupling of data from the flow field to the sound field, which may facilitate the separation of the dipole component from the total noise in experimental measurements.