Journal of Fluid Mechanics

Papers

Boundary layer flow and bed shear stress under a solitary wave

PHILIP L.-F. LIUa1, YONG SUNG PARKa1 and EDWIN A. COWENa1

a1 School of Civil and Environmental Engineering, Cornell University, Ithaca, NY 14853, USA

Abstract

Liu & Orfila (J. Fluid Mech. vol. 520, 2004, p. 83) derived analytical solutions for viscous boundary layer flows under transient long waves. Their analytical solutions were obtained with the assumption that the nonlinear inertia force was negligible in the momentum equations. In this paper, using Liu & Orfila's solution and the solutions for the nonlinear boundary layer equations, we examine the boundary layer flow characteristics under a solitary wave. It is found that while the horizontal component of the free-stream velocity outside the boundary layer always moves in the direction of wave propagation, the fluid particle velocity near the bottom inside the boundary layer reverses direction as the wave decelerates. Consequently, the bed shear stress also changes sign during the deceleration phase. Laboratory measurements, including the free-surface displacement, particle image velocimetry (PIV) resolved velocity fields of the viscous boundary layer, and the calculated bed shear stress were also collected to check the theoretical results. Excellent agreement is observed.

(Received January 19 2006)

(Revised August 28 2006)

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