Effects of air-side freestream turbulence on the development of air–liquid surface waves

Abstract

It is important to investigate the effects of air-side freestream turbulence on the development of air–liquid surface waves. Two turbulent-grid air flows are generated by regular and fractal grids in a wind-wave tank. Wind velocity and water-level fluctuations are measured with and without grids. The results show that regular and fractal grids can generate turbulent-grid air flows with different wind velocity fluctuations. The spectra of water-level fluctuations in the regular-type and fractal-type grid cases are consistent with those of pure wind-driven waves without a grid. Furthermore, as wind-wave properties, including the fetch law, dispersion relation, and Toba’s 3/2 power law, all hold in cases with and without grids, it is confirmed that the waves develop through the turbulence only near the free water surface, and not through the air-side freestream turbulence. This suggests that the effects of air-side freestream turbulence on wave development are negligible.