一个湍能封闭模型对风暴潮海底底应力的应用研究

A STUDY OF BOTTOM STRESS OF STORM SURGE -An Application of a Turbulent Energy Closure Model

将一个三维湍能封闭模型应用于开阔海区的风暴潮，通过数值计算探讨了Ｔａｙｌｏｒ底摩擦二次率的拖曳系数随空间的分布及拖曳系数与水深、海底粗糙度、风向和风速等因素的关系。本文对底摩擦二次率的可靠性做了评价。

In the present paper a three-dimensional turblent closure model is applied to a simple model under storm surge condations. The space distributions of the drag coefficient of the quadratic law of bottom stress are numerically studied. The relations between the drag coefficient and the water depth, the roughness length of sea bed, the wind speed and direction are also discussed. The results of the numerical experiments show that in most part of the region the quadratic law is valid and the value of the drag coefficient depends mainly on the water depth, the roughness length of sea bed, and slightly on the wind speed, but not on the direction of wind. However, in a small part of the region (named singular area) the value of the drag coefficient significantly differs from that of most part of the sea. The singular area usually locates where water velocity is very small. The quadratical law of bottom stress is no longer valid in the singular area. Owing to the conclution that the drag coeffcient is closely relative to the water depth and the roughness length of sea bed and there is a singular area of the drag coefficient, Cpcan hot be taken as a constant all over the sea when computing storm surge in real coastal seas by using two-dimensional depth-averaged shallow sea hydrodynamical models with the quadratic formula of bottom stress. The locale value of CD should be selected according to the local water depth, roughness of sea bed and flow condition. The results obtained in this paper will be beneficial to the selection and further study of the drag coefficient.