Hybrid approach for simulating flow-induced sound around moving bodies based on ghost-cell immersed boundary method

A hybrid approach based on the immersed boundary method (IBM) is developed for computation of flow-induced sound around moving bodies. In this method, a high-fidelity direct numerical simulation (DNS) solver is used to simulate the incompressible flow field. The sound field is predicted by discretizing acoustic perturbation equations (APEs) with dispersion-relation-preserving space scheme and low-dispersion and low-dissipation Runge-Kutta time integration. A sharp-interface IBM based on ghost-cell is implemented for present two-step DNS-APE approach to deal with complex moving bodies with Cartesian grids. The present method is validated through simulations of sound generation caused by flow past a rotating cylinder, an oscillating cylinder, and tandem oscillating and stationary cylinders. The sound generated by typical kinds of complicated bio-inspired locomotions, i.e., flapping flight by wings of varied shapes and collective undulatory swimming in tandem, are investigated using present method. The results demonstrate potential of the hybrid approach in addressing flow-induced sound generation and propagation with complex moving boundaries in a fluid medium, especially for the sound characteristics of bio-mimetic flows, which might shed lights on investigations on bio-acoustics, ethology of complex animal system, and related bio-mimetic design for quietness.