The Interaction of Crossed Waves and Wind-Induced Currents in a Laboratory Tank

Abstract

Subsurface current measurements were made to examine the response of wind-induced currents to the onset of mechanically generated crossed waves and to compare the results with the Craik-Leibovich (1976) theory of Langmuir circulations (LCs). To separate mean current including LCs from the wave-induced current the current data have been decomposed into two frequency ranges. In this paper we only describe the results of low-frequency data that consist of mean and turbulent motion of frequencies lower than the crossed waves.

The primary features of the experimental results are: (1) The most important effect of the wave-current interaction is the deepening of mixed layer. (2) The upwelling and downwelling currents associated with the LCs were clearly confirmed at antinodes and nodes of crossed waves, respectively, but the two components of horizontal current were largely governed by the direct wind-driven current rather than by the LCs. Nevertheless, it is found that the Reynolds stress associated with organized motion still plays an important role in the downward transport of the downwind momentum.