Directed acoustic beams interacting with heat mode: Coupled nonlinear equations and the modified KZK equation

摘要

The method of one-dimensional disturbances splitting into progressive waves of opposite directions and the heat mode by projection technique is applied to the quasi-plane problem. By such projecting the fundamental system of equations is transformed to three coupled nonlinear equations for the interacting modes. The thermoviscous flow is considered. In the case of self-action the system of coupled equations leads to the Khokhlov-Zabolotskaya- Kuznetsov(KZK) equation for acoustic beam. An evolution equation for a beam with account of iterated influence of the other modes is derived if this beam is dominant. The corrected evolution equation for a beam with cubic nonlinear terms is derived, and well as formulae on evolution of the first and second expansion terms of pressure in paraxial region. [References: 19]