VERTICAL VARIATIONS OF FLUID VELOCITIES AND SHEAR STRESS IN SURF ZONES

Abstract

Detailed laboratory measurements are made of the velocity fluctuations to investigate the processes of the turbulence generation, advection, diffusion and dissipation in the surf zone. An order of magnitude analysis of the transport equation of the turbulent kinetic energy using the normalization adopted by Kobayashi and Wurjanto (1992) indicates an approximate local equilibrium of turbulence for shallow water waves in the surf zone. Estimates are found for common surf zone turbulence parameters. The calibrated values are used to show that the eddy viscosity varies gradually over depth and is nearly time-invariant and that the local equilibrium of turbulence is a reasonable approximation for spilling waves in the inner surf zone.