管内螺旋涡流的数值模拟研究

Numerical Study of Helical Vortices in a Circular Pipe

本文用数值模拟的方法研究了螺旋纽带在圆管中引发的涡流形成过程与机理,分别用RNGκ-ε和RSM模型模拟计算,并与相关文献的实验结果进行对比,用更准确的RSM模型进行后续研究。在螺旋纽带中,由于边界层分离,先出现两个涡,根据角动量守恒,这两个涡的旋向与纽带旋向相反,在主流切向速度的作用下,这两个涡逐渐衰减,在衰减过程中,同样由于边界层分离,形成与纽带旋向相同的两个涡,这四个涡会暂时共存,之后逐渐减弱消失,随着流动的发展,由于流线弯曲不稳定,出现旋向与纽带相同的两个涡,并一直维持此涡结构。螺旋纽带中的二次流动是在壁面切应力,科氏力和离心力综合作用下产生的。

The present paper describes the numerical study of the creation process and mechanism of helical vortices induced by a twisted tape inside a circular pipe. The RNG κ-ε and the RSM turbulence model are used, the latter is in better agreement with experimental results, so the RSM turbulence model deserves further investigation. In the region of twisted tape, firstly, as the boundary layer of twisted tape separates, two vortices appeared and strength, they rotate counter relative to the tape twist, due to the conservation law of angular momentum. The two vortices decay as the influence of tangential velocity of the main flow. During their decaying process, another two co-rotating vortices appear due to the boundary layer separation, these four vortices coexist temporarily, then they decay and disappear. As the development of the flow, ＇two co-rotating helical vortices exist as the instability induced by streamlines deformation. Once the twisted tape ends, the co-rotating secondary vortices remain inside the straight pipe. Secondary motion induced by twisted tape inserts is based on wall shear stress, coriolis force and centrifugal force.