A 2D nonlinear wave propagation solver written in open-source MATLAB code

We describe a MATLAB implementation of a 2D wave solver capable of simulating the linear and nonlinear propagation of ultrasonic waves through an attenuating medium modeled as a 2D spatial grid, the acoustic properties of which can be arbitrarily assigned at each node. The object of this work is to create a freely distributed nonlinear wave solver that is useful for both ultrasound research and the instruction of nonlinear and ultrasound acoustics, and that is written in a popular interpreted language so that the model can be quickly and easily modified to address a range of simulation tasks. The solver is based on a pseudospectral derivative, time-domain integration algorithm previously described by Wojcik, et al. (1997), and models frequency-dependent attenuation through the application of multiple relaxation mechanisms. Forcing functions can be applied over simulation time to nodes on the calculation surface to simulate arbitrary ultrasound array geometries. The time record of any parameters can also be stored in order to, for example, measure the magnitude of harmonics or determine an array's point spread function. We present results from the solver, discuss its theoretical basis and structure, describe its calculation requirements given a variety of grid geometries and acoustic conditions, and provide the contact information needed to obtain the code.