Nonlinear wave propagation from a discrete annular array: Experiments

Abstract

To date, efforts to model nonlinear wave propagation from a bounded beam source have chiefly been concerned with unfocused and weakly focused circular piston sources [Lee and Hamilton, J. Acoust. Soc. Am. 97, 906–917 (1995)]. When the peak pressure does not exceed approximately 150 MPa, the Khokhlov–Zabolotskaya–Kuznetsov (KZK) nonlinear parabolic wave equation yields numerical solutions in agreement with experiments. However, little research has been reported on nonlinear wave propagation from an array of discrete sources. Theoretical and experimental results for an eight-element annular array will be presented. The source signal is typically a ten-cycle sine wave tone burst with a center frequency of 500 kHz. The outer diameter of the array is 0.14 m, and the surface areas of the elements are equal. While theoretical predictions will be shown, the experimental aspects of this research will be emphasized. [Work supported by ONR.] by Kargl