Study on wind shear acting on the water surface of closed water bodies

To simulate water quality in closed water bodies, it is necessary to simulate their circulation first because the circulation is closely related to the distribution of water quality variables in the closed water bodies. In simulation of the circulation in the closed water bodies, the study on wind stress acting on their water surface is prerequisite because in the closed water bodies, where the exchange with external waters is usually small, wind becomes the main factor help them circulate. Therefore, the main objective of this research is to investigate how the wind acts on the water surface and how the wind friction velocity spatially varies on the water surface of the closed water bodies through conducting indoor experiments. The experimental apparatus includes a rectangular tank filled with water modeling on a closed water body, a wind generating machine and a wind speed measuring sensor (Kanomax Japan Inc.). The measurements of wind velocity profiles above the water surface were conducted with the variety of average wind speed (U) under different percentages of aquatic plant coverage on the water surface. The results of this research indicate that when the effect of waves is negligible, the spatial variations of the wind friction velocity and the water surface velocity are relatively homogeneous along the free water surface. In addition, the water surface velocity is about 3% of the wind speed on average. These results are very useful for simulating the wind-induced flow in closed water bodies.