Experimental study on flow kinematics of breaking wave impinging and overtopping on a deck structure

Abstract

The present study experimentally investigates the flow kinematics due to breaking waves impinging and overtopping on a simplified deck structure. Several breaking-wave impinging scenarios in relation to the model deck are conducted. The resulting flow velocities in the aerated regions are measured using bubble image velocimetry (BIV). A wave focusing method is employed to generate plunging breakers. Repeated measurements are performed to obtain mean flow and turbulence characteristics. Two distinguished flow behaviors are observed among all seven scenarios. For the cases of a fully developed plunging breaker interacting with the deck structure, the maximum horizontal velocities above and below the structure are both around 1.2C, with C being the phase speed of the breaking wave; for the cases of a non-fully-developed plunging breaker impingement, the flow velocity below the deck is surprisingly large, with a value of 1.8C below the deck against 1.2C above the deck. Furthermore, the use of a dam-break flow to model the overtopping horizontal velocities on the deck is performed with satisfactory agreements for all the impinging scenarios. Moreover, the temporal and spatial varying prediction equation proposed by Ryu et al. (2007b) is used to model overtopping flow velocities, showing the applicability of this simplified methodology.