Accurate determination of object-image distance for planar objects in uniform subsonic flow

In this article, a technique for processing the image data to determine the object distance from the image plane, when a planar object is illuminated by a plane acoustic wave and the medium is in uniform subsonic flow, is presented. Closed-form expressions for the range are developed in terms of the Fourier transform of the image data for three specific directions of the flow, i.e., (i) normal and away from the object, (ii) normal and towards the object, (iii) parallel to the object. The Mach number of the flow is also determined from the image data, in addition to the range, making the technique useful, especially in the nearfield of the object. © 1987, Acoustical Society of America. All rights reserved.