A new time-domain approach for nonlinear wave propagation: Comparison with the KZK equation approach in the case of an unfocused cw beam

Abstract

A time-domain numerical model for simulating acoustic pulse focusing in soft tissue has already been presented. In this model, the main effects responsible for finite-amplitude wave propagation, i.e., diffraction, frequency-dependent attenuation, and nonlinearity, were taken into account. Here, a comparison between the results of this model with those of the KZK model is presented. Using this model, the acoustic pressure field of a plane circular transducer was simulated in water for a large range of cw-mode input excitation levels. The on- and off-axis pressure-time waveforms and their corresponding harmonic components were calculated using this model and the KZK model, and very good agreement was obtained between the two models. Furthermore, these results were verified by previously published experimental measurements. At present, all implementations of the KZK model are limited to planar or weakly focused sources. This study, along with this group’s previous work, reveals the validity of this finite-amplitude wave propagation model for a wide degree of source focusing (from a planar to a highly focused source), and in cw as well as PW modes. It is also shown that the computation time for this model is much less than for the KZK, using the same input parameters.