A Fully Parallel Dual-Grid Immersed-Boundary Framework for Flow-Induced Sound from Complex Moving and Deforming Bodies

Abstract

Predicting flow-induced sound from moving and deforming bodies is computationally demanding because the near-field hydrodynamics and the far-field acoustics require substantially different spatial resolutions and domain extents. A fully parallel hybrid framework is developed to address this disparity by coupling an incompressible Navier-Stokes solver to an acoustic perturbation equation (APE) solver on independently generated, non-conforming Cartesian grids. A sharp-interface ghost-cell immersed boundary method, with radial-basis-function reconstruction, imposes the boundary conditions for complex moving geometries on both grids. The converged flow field supplies the acoustic source through a one-way, precomputed parallel interpolation operator. This arrangement confines the flow grid to the body and wake while allowing the acoustic grid to extend independently into the far field. The framework is validated for Gaussian-pulse propagation, pulse scattering by a rigid cylinder, tonal sound from flow past a cylinder, and radiation from a traveling wavy foil. The predicted waveforms, wavelengths, pressure amplitudes, and radiation patterns agree closely with analytical solutions and published reference data. Applications to eel and Jack fish locomotion, a four-eel school, a manta ray, and a harbor seal further demonstrate the treatment of realistic three-dimensional morphologies, large boundary deformation, and multiple interacting swimmers. The results resolve morphology-dependent acoustic signatures and interference-driven changes in far-field directivity without requiring the flow grid to span the acoustic far field.