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弯曲型河流是自然界最为常见的河流形态,其水流特性以及河床泥沙的作用特性,对河流蠕动发展具有重要的影响,是河流动力学中研究的重要课题.弯曲河道中水流流态的转化涉及河床形态和河势单元的发展模式,包括:弯曲河道三维拟序涡与二次环流产生的条件;不同水流条件下拟序涡尺度分级情况;大尺度紊流结构与河湾自适应、互选择性,等等.本文以弯曲河流明渠为背景,首先对其层流转捩到紊流的特性进行研究,与顺直河道相比,其稳定中性曲线前移,失稳临界雷诺数降低,流动失稳过程中,对扰动波数的响应范围加大,层流更容易失稳.这些研究结果是传统流动稳定性理论中所没有的,本文的研究结果也弥补了这方面的不足和空白.
Curved river is the most common form of river in nature, and its water flow characteristics and sediment characteristics of riverbed have an important impact on river creep development, which is an important issue in river dynamics research. River bed morphology and river potential units, including: the conditions of three-dimensional quasi-vortex eddy and secondary circulation of curved channels; the classification of eddy scales under different water flow conditions; large-scale turbulence structure and river bay adaptation, mutual selection Etc. Based on the curved open channel, this paper studies the characteristics of the laminar transition to the turbulent flow. Compared with the straight channel, the steady-state neutral curve advances, the critical instability Reynolds number decreases, and the flow In the process of instability, the response range of disturbing wave number increases, and the laminar flow is more prone to instability.These results are not found in the traditional theory of fluid stability, and the results of this paper also make up for the shortcomings and gaps in this aspect.