Near-field acoustic holography for underwater moving surfaces

Abstract

Near-field acoustic holography has been the standard technique to accurately image static structure vibration from nearby acoustic pressure measurements. The classical application bases the method on the stable solution of an integral surface representation of the acoustic pressure. In this work, we will be concerned with the extension of NAH to image a vibrating structure moving underwater. In an underwater medium, even at slow speeds, the action between the flow and structure produces many radiation sources that could severely limit the accuracy of the integral surface representation used for static NAH. Using the Lighthill acoustic analogy, we use an integral surface representation for the structure’s radiated sound and a quadrupole source that models the corresponding flow-induced sound. Finally, we will justify the validity of the proposed method for COMSOL numerically generated pressure data that results from the internal excitation of a cylindrical structure moving over an underwater medium. This work has been supported by the Office of Naval Research.