Laboratory study of wind impact on steep unidirectional waves in a long tank
Zitan Zhang (Shanghai Jiao Tong University)
Tianning Tang (University of Oxford)
Xiaobo Zheng (Lanzhou University of Technology)
Wentao Xu (Shanghai Jiao Tong University)
Lijun Zhang (Shanghai Jiao Tong University)
Jung Hoon Lee (University of Melbourne)
Thomas A.A. Adcock (University of Oxford)
Jason Monty (University of Melbourne)
Alexey Slunyaev (Russian Academy of Sciences)
T.S. van den Bremer (TU Delft - Environmental Fluid Mechanics, University of Oxford)
Ye Li (The University of Edinburgh, Technical University of Denmark (DTU), Southern University of Science and Technology , Shanghai Jiao Tong University)
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Abstract
Understanding the effect of wind forcing on steep unidirectional waves is important for the study of wind-wave interaction. In this paper, unidirectional random wave experiments are carried out in a large-scale wave tank in which waves interacted with turbulent wind generated by wind fans. The properties and evolution of deep-water gravity waves subject to following wind forcing are investigated through parametric laboratory experiments. The effect of wind forcing on the significant wave height varies with the initial wave steepness. Wind forcing increases the growth of waves of small initial steepness but attenuates large, steep waves as a result of the vertical angle of the wind to the free surface in our experiments. The energy input by wind forcing increases the high-frequency tail of the wave spectra, and this effect increases with fetch. The mean frequency increases under wind forcing. The effect of wind forcing on the probability of extreme events is investigated. Wind forcing enhances wave steepness, resulting in a deviation of the exceedance probability from first-order and second-order theoretical distributions and an increased value of kurtosis but not skewness.