Near-Field and Far-Field Sound Radiation from a Line-Driven Fluid-Loaded Infinite Flat Plate Having Periodic and Non-Periodic Attached Rib Stiffeners
NAVAL UNDERSEA WARFARE CENTER NEWPORT DIV NEW LONDON CT NEW LONDON DETACHMENT
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The far-field and near-field solutions for the radiated acoustic pressure fro a line-driven fluid-loaded, rib-stiffened thin elastic plate have been obtained. The plate has been configured to have two sets of rib-stiffeners, though the formulation given may be extended to include additional rib-stiffener sets. The stiffeners composing a given set are identical and are spaced periodically with distance Q. However, one set of stiffeners is shifted by an amount from the other set. In this manner, portions of the plate may be configured with repeating sections having non-periodic rib spacing. The stiffeners exert reactive forces upon the plate, but not angular moments. Fluid loading is included on the upper surface of the plate while the lower surface is unloaded, except for a time harmonic line force applied normal to the lower surface. Expressions are derived, for the special case of periodic inter-rib spacing, which give the wavenumbers at which the magnitude of the wavenumber response obtains relative maximum and minimum values. For a stiffened plate, it is seen that excitation frequencies below coincidence generate large magnitude supersonic wavenumber components.
- Submarine Engineering
- Acoustic Detection and Detectors