Wave-Induced Effect on the Airside Velocity Field Above the Wind-Generated Water Waves

An experimental study was conducted to investigate the influence of surface waves on the airside flow behavior over the water surface. Two-dimensional velocity field in a plane perpendicular to the surface was measured using particle image velocimetry (PIV) at wind speeds of 3.7 and 4.4 m s⁻¹. The results show that the wave induced velocities are significant immediately adjacent to the water surface and their magnitudes decreases with height and become negligible at a height three times the significant wave height. The structure of the wave induced vorticity indicates two different type of flow pattern on the windward and leeward sides of the wave crest. Positive and negative magnitudes of the turbulent and wave induced Reynolds stress respectively, indicates upward and down transfer of momentum flux across air water interface. The results also indicate that the flow dynamics in the region two to three times significant wave heights are significantly different than that at greater heights. Higher magnitudes of the turbulent and wave induced Reynolds stresses were observed in this region which could not be predicted from the measurements at greater heights. Thus, it is concluded the understanding of the wave effects to the airflow field especially within the crest-trough region is vital to improve our knowledge about the air-water heat, mass and momentum exchange.