Dynamics of nonlinear piston‐generated and vertical‐array‐generated foci

Recent work using a vertical array of linear sources to produce a distant virtual source array [Walker et al., J. Acoust. Soc. Am. 120, 3007 (2006)] motivates investigation of the possibility of generating a nonlinear virtual source array. First, the nonlinear focal properties of a single piston as a function of amplitude and piston aperture are examined using the NPE [McDonald and Kuperman, J. Acoust. Soc. Am. 81, 1406 (1987)] and compared with results from the KZK equation [J. Acoust. Soc. Am. 119, 3618 (2006)]. Next, results are shown for a phased vertical array of spherical explosive sources, which produce Mach stemlike structures as the nonlinear component waves interact. Finally, the fully three‐dimensional problem of multiple piston beams focusing in a predetermined pattern is described. [Work supported by the Office of Naval Research.]