波と流れの共存場における底面近傍の水粒子速度の特性について

Abstract

Near-bottom water particle velocities in the fields where waves and currents co-exist areinvestigated both theoretically and experimentally. A new method is presented for calculatingthe water particle velocity in the turbulent boundary layer in a wave-current co-existing field.A boundary layer thickness δw in the co-existing field is expected to be variable with the waterparticle velocity of waves relatively to the current velocity. In this method, the boundary layerequation is solved as a free boundary problem by treating δw as an unknown boundary value.Several characteristics of the turbulent boundary layer such as the friction factor, friction velocity, boundary layer thickness and so on are calculated by this method, and the effect of the wave-currentvelocity ratio on them is discussed.In addition, near-bottom velocities are measured by a laser-doppler velocimeter in the current-only field, wave-only field and wave-current co-existing field, and the results are compared with thetheoretical ones.