Study On The Wind-generated Wave And Wind-wave Field Under The Downburst

The downburst is an extremely bad weather phenomenon,which is often accompanied by thunderstorms to produce a strong sinking stream and impact the ground and then radiate around.Different from the atmospheric boundary layer wind,it will produce instantaneous maximum wind speed near the ground,which will cause serious damage to the building structure in the whole wind field.At present,many scholars have studied the wind field characteristics of the downburst,but when the downburst occurs on the sea surface,the characteristics of the downwind field and the wave field based on the wind-wave coupling cooperation are not clear.The mechanism of wind-wave coupling in the downburst environment is discussed by numerical simulation and experimental research in this paper.Specific studies are as follows:(1)Numerical simulation of wind-wave fields.Based on the classical jet model,a numerical model is established for simulating the two-phase flow of wind and wave.The characteristics of wind field and wave field are studied by numerical simulation of different conditions.According to the results of numerical simulation,it is found that the average wind profile of the downburst under wind and wave coupling is similar to that of the classical wind profile,that is,the wind speed reaches the maximum near the liquid surface,and then decreases rapidly with the increase of height.In the wave field,a concave surface will be formed at the liquid level directly below the inlet of the jet because of the action of the downburst flow,and the wind field will drive the wave to produce and develop around.(2)Derivation of similarity theory.Based on the momentum equation of two-phase flow,the similarity criterion suitable for wind-wave field in downburst environment is deduced.Through this similarity criterion,the similar relationship between different scaled models is further deduced.The characteristics of the actual wind-wave field can be predicted by the data of the scale model.At the same time,the similarity criterion is verified by numerical simulation,and the Reynolds number independence is further discussed.According to the theoretical derivation,it is found that when the scale ratio of the scaled models is ?_l,the scaled models and prototype can achieve similarity as long as the incident wind speed scale ratio is?_l.(3)Experimental study of wind-wave fields.The jet model device of the laboratory is reformed,the flume is installed on the original platform,the characteristics of the wind-wave field are further explored by means of experiment,and the wave forming system is added to the flume to explore the influence of the background wave on the wind-wave field.Compared with the experimental results and the numerical simulation results,it is found that the results are close,so the reliability of the numerical simulation results is verified.At the same time,it is found that the wind field will affect the wave field in high frequency band,while the background wave will affect the wave field in low frequency band.