管内窄边扭旋元件诱导螺旋流的旋流强度分析

为了研究螺旋流在形成、发展及衰减过程中旋流强度的变化规律，采用数值模拟方法对管内置窄边扭旋元件诱导产生的螺旋流进行分析，得到了雷诺数和元件扭率对旋流强度的影响规律。结果表明：流体进入扭旋元件后，在元件两侧形成两个与主螺旋流旋向相反的二次涡流；流体流出扭旋元件后，旋流螺距经历一个由大变小，再由小变大的过程；在螺旋流形成发展阶段，雷诺数对旋流强度影响较小，旋流强度随着元件扭率的增大而迅速提高，由于惯性作用旋流强度在元件出口1/6元件长度处达到最大，该位置与雷诺数和元件扭率无关；整个螺旋流发展阶段旋流强度呈现一种指数变化规律；流体流过旋流强度最大截面后，由于流体粘滞力大于惯性力，旋流强度以近似线性的规律衰减，雷诺数越大衰减速度越慢，扭率对旋流衰减速度影响较小。

Swirl intensity analysis of the swirl flow induced by a narrow twisted element in a pipe#br#

In order to study the swirl intensity variations in the swirl flow during its formation, development and decay, the swirl flow induced by a narrow twisted element in a pipe has been analyzed by numerical simulation, and the influence of varying Reynolds number and element torsion ratio on the swirl intensity has been investigated. It was found that secondary vortices rotating in the opposite direction to the main spiral flow were formed at each side of the twisted element as soon as the fluid enters the twisted element. After the fluid flows out of the twisted element, the swirl flow changes from large pitch to small one, and then back to a larger pitch again. During the forming and developing stage of the swirl flow, the Reynolds number has little influence on the swirl strength, and swirl intensity increases rapidly with increasing twist ratio. Due to the flowing inertia effect, swirl intensity reaches a maximum at a 1/6 pitch cross section downstream from the twisted element exit, and this is independent of the Reynolds number and the torsion of the twisted element. An exponential variation appears in the whole fluid developing process. After the fluid flows over the maximum swirl intensity section, since the fluid viscosity is greater than the inertia force, the swirl intensity decays linearly along the pipe, with larger Reynolds numbers resulting in slower decay rates. However, the twist ratio has little effect on the decay of the swirl flow. 