Calculation of transient fields in immersed solids radiated by linear focusing arrays

This paper aims at calculating transient fields radiated by linear arrays into immersed solids by using the angular spectrum approach (ASA), which is implemented based upon the temporal and the 2-D spatial discrete Fourier transform (DFT). The sinc-Fourier transform algorithm is extensively employed and allows arbitrary spatial sampling frequency to be used for sampling source plane without restriction of integer number of sampling intervals representing the elements and the gaps between the adjacent elements in various arrays. Calculation of transient fields in immersed solids from the array is presented in some detail. The wave mode conversion at the liquid-solid interface is taken into account. Specific fields in copper immersed in water are given according to the focusing laws used by the arrays in two different cases, i.e., nonfocusing and focusing longitudinal (or compressional) wave (LW). For each case, transient LW and shear wave (SW) fields are presented