Characteristics of Turbulence Structure and Undertow in the Surf Zone

摘要: The characteristic motion of water under breaking waves and the turbulence structure in surf zone were investigated through detailed two-dimensional velocity measurements a wave flume. Significant difference was found between processes outer inner regions zone. field each region consists steady current, periodic motion, organized vortex turbulence. It that caused by an important fluid connecting vertical profiles undertow, which is current below trough level, from histories measured hot-film laser-Doppler-velocimeters. generated upper layer prevents development bottom boundary region. distribution mean Reynolds stress eddy viscosity coefficient can be approximated linear functions elevation. offshore-directed shear on so large it not neglected modeling undertow. transition point defined as offshore limit quasi-steady distance to expressed terms depth slope. In order describe mechanism energy transfer during accurately, model presented vortexes taken into account transmitter process calculated this agreed with experimental results qualitatively. mass momentum fluxes also discussed. transport induced vortexes. By using models transport, for quantitatively evaluated dissipation rate basis dimensional analysis. variation level predicted good accuracy considering flux evaluate undertow arbitrary beach topography incident condition.