Study on behavior wind-induced flow and water quality in a density stratified closed water area with aquatic plants

池塘、水库、湖泊、河口等密度分层封闭水域的水环境动力学受基于机械扰动和热扰动的湍流的影响。热干扰包括白天以太阳辐射为基础的照明和供暖，以及夜间以排放为基础的冷却。风致水流的机械扰动和风在水面上产生的风浪。我们认为封闭水域风致水流的机械扰动是由于风对水面的作用而产生的。在实验室风浪水槽中对机械扰动引起的湍流卷吸现象进行了实验研究。认为浮游植物对水面的占有率对封闭水域内的湍流卷吸作用有一定的影响。结果表明，漂浮水草的存在对湍流卷吸尺度有显著影响。研究还发现，夹带速度与密度分层流动的稳定性参数Richardson数的-3/2次方有关。主要结论如下：(1)从夹带速度实验来看，浮水植物覆盖率β的增加降低了上层的夹带速度。(2)从湍流结构实验来看，随着浮游植物覆盖率的增加，湍流能量减少。(3)浮水植物覆盖率β的增加，降低了表层产生的湍流能量。当湍流能量转化为势能时，卷吸速度的降低与湍流结构之间明显地建立了密切的关系。

Water environmental dynamics in closed water areas with density stratify such as ponds, reservoirs, lakes and estuaries are effected by turbulent flows based on mechanical and thermal disturbances. The thermal disturbance consists of lighting and heating based on solar radiation in the daytime and cooling based on emission at the night. The mechanical disturbance of wind induced flow and wind wave generated by wind action on the surface. We considered the mechanical disturbance of wind induced flow was generated by wind action on the surface in the closed water areas. An experimental investigation of turbulent entrainment induced by the mechanical disturbance was carried out in a laboratory wind -wave tank. We considered that the occupying rate of the floating water plants to the water surface affected on the turbulent entrainment in the closed water area. The results indicated that the existence the floating water plants contributed to make a significant effect on the scale of the turbulent entrainment. It was also found that the entrainment velocity depended on the Richardson number to the power of-3/2, the stability parameter of density stratified fluid flow. The following conclusions can be drawn : (1).From the experiment of entrainment velocity, the increase of the covered rate β of floating water plants decreases the entrainment velocity of the upper layer. (2).From the experiment of turbulent structure, the increase of the covered rate of floating water plants decreases the amount of turbulent energy. (3).The increase of the covered rate β of floating water plants decreases the turbulent energy of the upper layer that is produced at the surface. As the turbulent energy is transformed into potential energy, a close relationship between the decrease of entrainment velocity and the turbulent structure is clearly established.