Vortex generation and evolution in water waves propagating over a submerged rectangular obstacle Part I. Solitary waves

Interactions between a solitary wave and a submerged rectangular obstacle a re investigated both experimentally and numerically. The Particle Image Vel ocimetry (PIV) technique is used to measure the velocity field in the vicin ity of the obstacle. The generation and evolution of vortices due to flow s eparation at the corners of the obstacle are recorded and analyzed. It is f ound that although the size of the vortex at the weatherside of the obstacl e is smaller than that at the leeside, the turbulence intensity is, however , stronger. A numerical model, based on the Reynolds Averaged Navier-Stokes (RANS) equations with a k-epsilon turbulence model, is first verified with the measurements. Overall, the agreement between the numerical results and laboratory velocity measurements is good. Using the RANS model, a series o f additional numerical experiments with different wave heights and differen t heights of the rectangular obstacle are then performed to test the import ance of the energy dissipation due to the generation of vortices. The corre sponding wave transmission coefficient, the wave reflection coefficient and the energy dissipation coefficient are calculated and compared with soluti ons based on the potential flow theory. As the height of the obstacle incre ases to D/h = 0.7, the energy dissipation inside the vortices can reach nea rly 15% of the incoming wave energy. (C) 2001 Elsevier Science B.V. All rig hts reserved.