Lagrangian meshfree particle method for modeling acoustic wave propagation in moving fluid

Abstract

Introducing the Lagrangian approach to acoustic simulation is supposed to reduce the difficulty in solving problems with deformable boundaries, complex topologies, or multiphase media. Specific examples are sound generation in the vocal track and bubble acoustics. As a Lagrangian meshfree particle method, the traditional smoothed particle hydrodynamics (SPH) method has been applied in acoustic computation but in a quiescent medium. This study presents two Lagrangian approaches for modeling sound propagation in moving fluid. In the first approach, which can be regarded as a direct numerical simulation method, both standard SPH and the corrective smoothed particle method (CSPM) are utilized to solve the fluid dynamic equations and obtain pressure change directly. In the second approach, both SPH and CSPM are used to solve the Lagrangian acoustic perturbation equations; the particle motion and the acoustic perturbation are separated and controlled by two sets of governing equations. Subsequently, sound propagation in flows with different Mach numbers is simulated with several boundary conditions including the perfected matched layers. Computational results show clear Doppler effects. The two Lagrangian approaches demonstrate convergence with exact solutions, and the different boundary conditions are validated to be effective.