We investigated the Kármán vortex behind a circular cylinder in a polymer solution by a molecular dynamics simulation. The vortex characteristics are distinctly different for short and long polymers. The solution with the long polymer exhibits a reduction in the vortex shedding frequency and broadening of the lift coefficient spectrum. On the other hand, the characteristics of the short-polymer solution are almost the same as those of the Newtonian fluid. These facts are consistent with the experiments. Because the distributions of the gyration radius and the orientational order of the long-polymer solution are highly inhomogeneous in the flow field, we conclude that the extensional property of the polymer plays an important role in changing the flow characteristics.

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聚合物对卡尔曼涡的影响：分子动力学研究

我们通过分子动力学模拟研究了聚合物溶液中圆柱后的Kármán涡。短聚合物和长聚合物的涡旋特性明显不同。具有长聚合物的溶液显示出涡旋脱落频率降低和升力系数谱变宽。另一方面，短聚合物溶液的特性与牛顿流体的特性几乎相同。这些事实与实验是一致的。由于长聚合物溶液的回转半径和取向顺序的分布在流场中高度不均匀，因此我们得出结论，聚合物的拉伸性能在改变流动特性中起着重要的作用。