小曲率矩形截面弯管内流动特性数值模拟

Numerical Simulation of Flow Characteristics in a Curved Rectangular Duct for Small Curvature Ratio

本文对小曲率矩形截面弯管内的不稳定流动特性进行了数值模拟研究，分析了不同了De数时的流动发展过程以及De数对流动特性的影响。De数在0-200范围内，通过截面速度及轴向速度在不同De数的比较，得到了临界De数约为135。结果表明，当De数小于135时，截面内的二次流为两涡结构，但当De数大于135时，截面内的二次流动发展为四涡结构。De数在125～135范围内，当弯管内存在扰动时，出现分叉流动现象，即不稳定的流动结构。这些研究对工业管道的设计和优化具有一定的指导意义。

In this paper, the flow characteristics in a small curvature curved rectangular duct are investigated numerically. The evolutive process of the flow is studied at different De number in detail, and the influence of different De number on the flow characteristics is analyzed. De number changes from 0 to 200. The critical De number about 150 can be obtained by comparison of secondary flow distribution in the cross section and main flow velocity in the axis direction at different De number. The results show that the secondary flow structure has two vortices when De number is less than 135, but four vortices flow structure in the cross section will be obtained if the De number is more than 135. The flow bifurcation in the case of De number in range of 125-135 will be present if there have effects of the pitch on the flow in the curved rectangular duct. These calculated results are useful for the design and optimum of industrial duct.