Quantification of Flow Noise Produced by an Oscillating Foil

TL;DR

This study numerically quantifies flow noise generated by an oscillating hydrofoil, revealing how flow and kinematic parameters influence sound pressure levels and their patterns, with implications for underwater vehicle design and bioacoustics.

Contribution

It introduces a detailed numerical analysis of flow noise from oscillating hydrofoils using FW-H method across various parameters, linking acoustic emissions to hydrodynamic forces.

Findings

Flow noise exhibits dipole-like pressure distributions.

Sound pressure levels depend on Reynolds and Strouhal numbers.

Dipole axes orientation is influenced by reduced frequency.

Abstract

Getting inspired from swimming natural species, a lot of research is being carried out in the field of unmanned underwater vehicles. During the last two decades, more emphasis on the associated hydrodynamic mechanisms, structural dynamics, control techniques and, its motion and path planning has been prominently witnessed in the literature. Considering the importance of the involved acoustic mechanisms, we focus on the quantification of flow noise produced by an oscillating hydrofoil here employed as a kinematic model for fish or its relevant appendages. In our current study, we perform numerical simulations for flow over an oscillating hydrofoil for a wide range of flow and kinematic parameters. Using the Ffowcs-Williams and Hawkings (FW-H) method, we quantify the flow noise produced by a fish during its swimming for a range of kinematic and flow parameters including Reynolds number, reduced frequency, and Strouhal number. We find that the distributions of the sound pressure levels at the oscillating frequency and its first even harmonic due to the pressure fluctuations in the fluid domain are dipole-like patterns. The magnitudes of these sound pressure levels depend on the Reynolds number and Strouhal number, whereas the direction of their dipole-axes appears to be affected by the reduced frequency only. Moreover, We also correlate this emission of sound radiations with the hydrodynamic force coefficients.