Sound field predictions for a monopole source moving uniformly in a stratified medium above an impedance plane

摘要

This paper investigates the pressure time history of a monopole source moving uniformlyabove an impedance ground. The classical Lorentz transform converts the problem of auniformly moving source into an equivalent problem of a stationary source in the Lorentzframe. A modified Lorentz transform is proposed which facilitates the numerical analysisin a horizontally stratified medium while allowing a height-dependent density and soundspeed profile to be incorporated in the analysis. A set of the Lorentz frame governingequations has been obtained that allows implementation of a Fast Field Program (FFP) inthe Lorentz frame. A global matrix formulation is developed by adapting the stationarysource method to the moving frame. Further refinements yield an improved representationof the global matrix that can be expressed in a tri-diagonal form. It can subsequently beinverted with much greater efficiency than the original penta-diagonal matrix. A threedimensionalFFP can be applied to obtain the pressure time-histories at various sidelinedistances simultaneously. The numerical results are compared against a ray tracingalgorithm. Unlike the ray theory approach, the wave-based FFP formulation can lead tomore accurate predictions since wave phenomena such as interference and diffraction areincluded.