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Velocity Distribution and Particle Trajectories in Internal Wave Propagating on an Upper Slope

Author(s): Kim-Cuong Nguyen; Motohiko Umeyama; Tetsuya Shintani

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Keywords: PIV Measurements; Internal waves; Particle trajectory; Water particle velocity

Abstract: This paper presents the experimental and numerical investigations of kinematics of internal waves propagating over a sloping bottom in two-layer stratified water. The distributions of particle velocities, trajectories have been investigated for different layer thickness ratios and wave periods. The spatial velocity field was first measured using PIV technique in the experimental tank. Then, we predicted the velocity numerically by twodimensional hydrodynamic model. The particle velocity in the lower layer is stronger as the waves approach to the slope. A technique to transfer the velocity in Eulerian grids into Lagrangian velocity is presented. Therefore, the particle trajectory can be estimated due to the shoaling of internal waves. The trajectories of water particles are not elliptical and not closed for each case. We confirmed from the measured and computed results that a particle near the density interface yields a maximum forward drift and particles away from interface tend to move backward to conserve the mass in the closed tank. The vertical excursion of the particle becomes smaller than its horizontal excursion with distance up in the water column. The measured velocity and particle paths were also compared and in fair agreement with numerical results.


Year: 2012

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