Author(s): Toomas Liiv

Linked Author(s): Toomas Liiv

Keywords: No Keywords

Abstract: The velocity field created by a plunging breaking wave on a rough uniform slope of 1 to 17 was studied experimentally in a two-dimensional wave flume. Laser-Doppler anemometry was used to measure the velocity field inside the surf zone. Such flow variables such as turbulence intensities, Reynolds stresses and turbulent kinetic energy are examined. It is found that all turbulent quantities depend on the value of flow acceleration and bottom roughness. During the deceleration phase, all turbulent quantities reach their maximum values. Turbulent kinetic energy is highest under the wave crest and decreases rapidly to a constant value under the wave trough. The bottom boundary layer roughness significantly changes the nearbed flow structure. Maximum horizontal velocity in the zone close to the surf zone bed was reduced, whereas the maximum vertical velocity in the bottom zone increased. The turbulent quantities close to the bottom boundary layer increased whereas close to the wave trough level the turbulence level stayed the same. The results suggest that the increase in turbulent quantities depend on Reynolds number of the flow. The effect is strengthened as the Reynolds number increases. The effect of bottom roughness diminishes with distance from the bed.

DOI:

Year: 2001