弯曲河流湍流结构动力演化特征

Evolution Features of Turbulent Structures in A Bend River

将弯曲河流中湍流结构看做一种扰动波,通过分析扰动波增长率的变化来研究湍流结构的动力演化特征.针对二维弯曲河流,采用流动稳定性理论与摄动法建立河流自然坐标下的湍流运动理论模式,运用差分法离散方程,利用Muller法进行特征值求解,进而分析弯曲河道二维湍流结构在不同弯曲度和雷诺数条件下的变化.结果表明,湍动能量主要由小尺度涡体结构产生的脉动来提供,小尺度涡体结构的演变比较剧烈,对河道弯曲度和雷诺数的改变也更敏感.另外,弯曲河道对拟序波有一定的选择性,也正是这些特征波的湍流结构促成了弯道的形成及保持.

The turbulent structure in a meandering river was considered as a type of perturbation wave. In this paper, evolution features of the turbulent structure were studied by the change of perturbation increase rate. Aiming at the turbulent structure in a two dimensional bend flow, a turbulent motion theory for fully rough flow was established in natural coordinate system using the hydrodynamic stability theory and the perturbation method. Finite difference method and Muller method were adopted to solve the equations in order to investigate the variation of the two dimensional turbulent structure under different crooked degrees and Reynolds numbers. The result shows that the turbulent energy would be provided mainly by small eddies, the motion of which is violent and high sensitive to the curvature and Reynolds number. Moreover, the river bend has selectivity on the perturbation waves which develop and maintain the river meandering.