Chaotic mixing in a helix-like pipe with periodic variations in curvature and torsion
Chaotic mixing in a helix-like pipe with periodic variations in curvature and torsion
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DOI：
10.1088/0169-5983/42/3/035506
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发表时间：
2010-06
影响因子：
1.5
通讯作者：
B. Jang;M. Funakoshi
中科院分区：
文献类型：
--
作者：
B. Jang;M. Funakoshi
本文用数值方法研究了在轴向压力梯度作用下螺旋形圆管中定常粘性流体颗粒的混沌运动及其混合效率。该管以恒定节距缠绕在圆形或椭圆形柱体周围，使得该管的中心线的曲率κ和扭转τ连续地且周期性地变化。如果κ和τ都很小且缓慢变化，则流体颗粒的横截面运动预计近似由迪恩流和刚性旋转流的总和控制。从庞加莱截面和混合程度指数的值，它被发现，有一个中间范围内的流动雷诺数Re在庞加莱截面的混沌区域大，混合效率在短时间内是高的。此外，更大的混沌区域和更高的混合效率观察到的管道缠绕在一个较小半径的圆柱和管道缠绕在一个较薄的椭圆柱。这些结果可用特征比λ=12τ/（κRe）在一个周期内的变化来解释。
Chaotic motion of fluid particles due to a steady viscous flow in a helix-like circular pipe caused by an axial pressure gradient, and the mixing efficiency of this flow are numerically examined here. The pipe is wound around a circular or elliptic cylinder with a constant pitch so that the curvature κ and torsion τ of the centerline of this pipe vary continuously and periodically. If both κ and τ are small and slowly varying, the cross-sectional motion of fluid particles is expected to be approximately governed by the sum of Dean's flow and the flow of rigid rotation. From Poincaré sections and the values of an index of the extent of mixing, it is found that there is an intermediate range of Reynolds number Re of flow within which chaotic regions in Poincaré sections are large and mixing efficiency over a short time is high. Moreover, larger chaotic regions and higher mixing efficiency are observed for pipes wound around a circular cylinder of smaller radius and for pipes wound around a thinner elliptic cylinder. These results can be explained by the variation in characteristic ratio λ=12τ/(κRe) in one period.