Garg Himani, Calzavarini Enrico, Mompean Gilmar, Berti Stefano
Université de Lille, Unité de Mécanique de Lille, UML EA 7512, F-59000, Lille, France.
Eur Phys J E Soft Matter. 2018 Oct 2;41(10):115. doi: 10.1140/epje/i2018-11726-4.
The aggregation properties of heavy inertial particles in the elastic turbulence regime of an Oldroyd-B fluid with periodic Kolmogorov mean flow are investigated by means of extensive numerical simulations in two dimensions. Both the small- and large-scale features of the resulting inhomogeneous particle distribution are examined, focusing on their connection with the properties of the advecting viscoelastic flow. We find that particles preferentially accumulate on thin highly elastic propagating structures and that this effect is the largest for intermediate values of particle inertia. We provide a quantitative characterization of this phenomenon that allows to relate it to the accumulation of particles in filamentary highly strained flow regions producing clusters of correlation dimension close to 1. At larger scales, particles are found to undergo turbophoretic-like segregation. Indeed, our results indicate a close relationship between the profiles of particle density and fluid velocity fluctuations. The large-scale inhomogeneity of the particle distribution is interpreted in the framework of a model derived in the limit of small, but finite, particle inertia. The qualitative characteristics of different observables are, to a good extent, independent of the flow elasticity. When increased, the latter is found, however, to slightly reduce the globally averaged degree of turbophoretic unmixing.
通过二维的大量数值模拟，研究了具有周期性柯尔莫哥洛夫平均流的奥尔德罗伊德 - B流体在弹性湍流状态下重惯性粒子的聚集特性。研究了所得非均匀粒子分布的小尺度和大尺度特征，重点关注它们与平流粘弹性流特性的联系。我们发现粒子优先聚集在薄的高弹性传播结构上，并且这种效应在粒子惯性的中间值时最大。我们对这一现象进行了定量表征，使其能够与丝状高应变流区域中粒子的聚集相关联，这些区域产生了关联维数接近1的簇。在更大尺度上，发现粒子会发生类似涡旋电泳的分离。实际上，我们的结果表明粒子密度分布和流体速度波动之间存在密切关系。粒子分布的大尺度不均匀性在一个基于小但有限的粒子惯性极限推导的模型框架内进行了解释。不同可观测量的定性特征在很大程度上与流动弹性无关。然而，当流动弹性增加时，发现它会略微降低全局平均的涡旋电泳分离程度。
