Sound and vibration in underwater and other structures

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This project aims to provide a fuller understanding of the vibrational and acoustic-radiation properties of engineering structures that are common in underwater applications and in aircraft design. Such bodies are typically composed of thin flexible plates (comprising the hull or fuselage), which are reinforced by bulkheads or ribs or other spatial inhomogeneities. The transmission of elastic waves along or through such structures is highly complex as the ribs act to scatter the waves into other vibrational modes, and the presence of the surrounding fluid also provides an alternate propagation route and coupling mechanism to generate acoustic waves.In this project the student will employ a range of advanced asymptotic and modelling techniques to understand better a number of key questions in this area, such as how to minimize the sound radiation from internal vibrational sources and how to reduce noise from the surrounding fluid impinging onto the vehicle itself. To make progress, a variety of simplified models shall be examined by analytical and computational methods, which exploit the disparity of lengthscales found naturally (building on the work discussed in [1]). The student will, as time allow, also consider the effects of coatings and other advanced 'smart' materials on sound emission and absorption.[1] P.A. Cotterill, W.J. Parnell, I.D. Abrahams, R. Miller, and M. Thorpe. The time-harmonic antiplane elastic response of a constrained layer. Journal of Sound and Vibration. 348: 167-184, 2015.