Fully Nonlinear Boussinesq-Type Equations for Waves and Currents over Porous Beds
Publication: Journal of Engineering Mechanics
Volume 132, Issue 2
Abstract
The paper introduces a complete set of Boussinesq-type equations suitable for water waves and wave-induced nearshore circulation over an inhomogeneous, permeable bottom. The derivation starts with the conventional expansion of the fluid particle velocity as a polynomial of the vertical coordinate followed by the depth integration of the vertical components of the Euler equations for the fluid layer and the volume-averaged equations for the porous layer to obtain the pressure field. Inserting the kinematics and pressure field into the Euler and volume-averaged equations on the horizontal plane results in a set of Boussinesq-type momentum equations with vertical vorticity and -dependent terms. A new approach to eliminating the dependency in the Boussinesq-type equations is introduced. It allows for the existence and advection of the vertical vorticity in the flow field with the accuracy consistent with the level of approximation in the Boussinesq-type equations for the pure wave motion. Examination of the scaling of the resistance force reveals the significance of the vertical velocity to the pressure field in the porous layer and leads to the retention of higher-order terms associated with the resistance force. The equations are truncated at , where measure of frequency dispersion. An analysis of the vortical property of the resultant equations indicates that the energy dissipation in the porous layer can serve as a source of vertical vorticity up to the leading order. In comparison with the existing Boussinesq-type equations for both permeable and impermeable bottoms, the complete set of equations improve the accuracy of potential vorticity as well as the damping rate. The new equations retain the conservation of potential vorticity up to . Such a property is desirable for modeling wave-induced nearshore circulation but is absent in existing Boussinesq-type equations.
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Acknowledgments
This study has been supported by the Office of Naval Research, Coastal Geosciences Program through research Grant No. ONRN00014-04-1-0310. Discussions with Dr. James Kirby and assistance from Dr. Eric Cruz are sincerely acknowledged.
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Information & Authors
Information
Published In
Journal of Engineering Mechanics
Volume 132 • Issue 2 • February 2006
Pages: 220 - 230
Copyright
© 2006 ASCE.
History
Received: Feb 3, 2005
Accepted: Jun 9, 2005
Published online: Feb 1, 2006
Published in print: Feb 2006
Notes
Note. Associate Editor: Nikolaos D. Katopodes
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