Fast 3D simulation of 2nd harmonic ultrasound field from arbitrary transducer geometries

A method for fast numerical simulation of nonlinear wave propagation based on a quasi-linear approximation has previously been presented. In the current study this method has been further developed to yield correct levels of the second- harmonic wave. The method can be used for 3D simulations of second-harmonic fields from arbitrarily transducer geometries. The method has been validated by comparing simulations to results produced by a conventional nonlinear simulation model and to experimental measurements. The reference simulation model was a numerical solution of the KZK equation for a forward-propagating pulse using a operator splitting approach. Experimental verifications were performed with hydrophone measurements in a water tank. Results showed a good match between the simulation models and measurements for MI up to 0.4 for an annular array probe and for MI up to 1 for a rectangular probe. For higher MI values the quasi-linear method showed a gradual increased over-estimation of the second harmonic field.