Numerical simulation of nonlinear effects in high power ultrasound applications

An extension of a recently developed simulation scheme for the calculation of nonlinear wave propagation in thermo-viscous fluid media is presented. Based on the nonlinear wave equation derived by Kuznetsov, the nonlinear pressure field is calculated by means of a finite element formulation. Furthermore, generated mean acoustic force densities can be obtained. Considering real-live high intensity sources which involve pressure amplitudes of up to 100 MPa and higher, significant differences between linear and nonlinear calculations are exhibited, resulting in force density changes up to 4 order of magnitudes. Plane wave applications as well as plane piston sources are used in these investigations. Streaming velocity calculations based on the streaming forces of plane piston sources are also presented. As an application of our calculation scheme a high intensity focusing pulse source, as used in medical applications, with a peak pressure amplitude of approx. 80 MPa is presented