Browsing by Author "Hawwa, Muhammad A."

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    Interaction of Surface Gravity Waves on a Nonuniformly Periodic Seabed
    Nayfeh, Ali H.; Hawwa, Muhammad A. (AIP Publishing, 1994-01-01)
    The interaction of surface gravity waves on a nonuniformly periodic seabed is considered. The method of multiple scales is used to analyze the interaction leading to two coupled-mode equations. The power reflection coefficient is used as an indicator to evaluate the filter action of the bottom corrugation. The results show that the modes are strongly coupled when the Bragg resonant condition is satisfied. The characteristics of the filtration are found to be enhanced by imposing special types of amplitude and phase modulated periodic nonuniformities, including amplitude taper and chirped periodic variations.
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    Torsional mode coupling and filtering in a composite waveguide with multiperiodic interface corrugations
    Asfar, Omar R.; Hawwa, Muhammad A. (Acoustical Society of America, 1993-05-01)
    This study is concerned with the interaction of six torsional modes in a composite axisymmetric waveguide whose interfaces are sinusoidally corrugated in the axial direction. The modes are interacting when two resonant conditions on the codirectional modes and a Bragg condition occur simultaneously. In light of the weakness of the interface corrugations, the perturbation method of multiple scales is used to derive the mode coupling equations. A novel numerical scheme for two-point boundary-value problems is used to solve the coupled amplitude equations. The power reflection coefficient of a filter section is then calculated for the cases of uniform, tapered, and chirped corrugations. An optimal filter is realized by combining both taper and chirp thus producing a nearly ideal characteristics.