Direct computation of acoustic scattering and difference frequency generation

Abstract

A simulation of the scattered field at the difference-frequency resulting from the nonlinear interaction of two beams at differing frequencies incident on a fluid scatterer is performed. The total wavefield response is modeled using a finite-difference time-domain approximation and a perfectly matched layer to estimate the spatial scattering features of the medium. A pulsed ultrasonic transducer beam is modeled and its interaction with a fluid scatterer with spatially varying compressibility contrast is visualized. The second-order pressure field is determined as a response to the difference-frequency source field constructed from the first order-response of the scatterer to the two incident beams as well as a spatial distribution of the nonlinear parameter. The performance and accuracy of the numerical simulation is examined.