Acoustic Aperture Diffraction in a Transversely Moving Medium
The theory of diffraction from a screen in a static medium is well known. The diffraction pattern is altered, however, if there is relative motion between the diffraction plane, the observation plane or the medium between planes. The case of relative transverse motion of the medium is investigated theoretically by generalizing the wave equation to include this motion, assuming a uniform, constant velocity. An equivalent Rayleigh-Sommerfeld integral is developed for this case. It is used to obtain a closed-form solution for the diffraction pattern in the Fraunhofer region for medium velocities less than the speed of sound. This solution is used to predict the amplitude distributions for several diffracting screen configurations. The results of this theory have application in performance characterization for a number of highscan-rate acoustic imaging systems.
KeywordsRadiation Pattern Cylindrical Lens Moving Medium Medium Velocity Rectangular Aperture
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