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A Simple Approach to Estimate Flow-Induced Noise from Steady State CFD Data

A computationally efficient method to approximate the total sound power and far-field acoustic intensity spectra generated by turbulent flow past a rigid body is proposed. The method is based on Proudman’s analytical formula for the sound generated by isotropic turbulence. This formula expresses the sound intensity of locally isotropic turbulence for low Mach numbers in terms of the kinetic energy of the turbulence, k, and its dissipation rate, ε . In this work, the approach is extended to non-uniform turbulent flows and the associated acoustic spectra are expressed in terms of the standard steadystate variables, k and ε , conventionally used in computational fluid dynamics (CFD). Since these steady-state variables of turbulent flow are much easier to calculate than the non-stationary turbulent fluctuations used in traditional formulations for the flow sound, this approach dramatically reduces the computational burden of the flow noise calculation. Such a computationally efficient method for predicting flow noise is essential for conducting extensive ‘what-if’ studies such as shape optimisation to reduce flow noise. The final expressions for the proposed method are calibrated against experimental and numerical data for flow noise of turbulent jets and boundary layers. The method is then applied to study the coefficient of drag and Mach number dependence of the sound generated by flow past a slender body.