Particle chirality does not matter in the large-scale features of strong turbulence.

IF 3.6 2区 工程技术 Q1 MECHANICS Journal of Fluid Mechanics Pub Date : 2024-09-20 eCollection Date: 2024-09-25 DOI:10.1017/jfm.2024.577
G Piumini, M P A Assen, D Lohse, R Verzicco
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Abstract

We use three-dimensional direct numerical simulations of homogeneous isotropic turbulence in a cubic domain to investigate the dynamics of heavy, chiral, finite-size inertial particles and their effects on the flow. Using an immersed-boundary method and a complex collision model, four-way coupled simulations have been performed and the effects of particle-to-fluid density ratio, turbulence strength, and particle volume fraction have been analysed. We find that freely falling particles on the one hand add energy to the turbulent flow but, on the other hand, they also enhance the flow dissipation: depending on the combination of flow parameters, the former or the latter mechanism prevails, thus yielding enhanced or weakened turbulence. Furthermore, particle chirality entails a preferential angular velocity which induces a net vorticity in the fluid phase. As turbulence strengthens, the energy introduced by the falling particles becomes less relevant and stronger velocity fluctuations alter the solid phase dynamics, making the effect of chirality irrelevant for the large-scale features of the flow. Moreover, comparing the time-history of collision events for chiral particles and spheres (at the same volume fraction) suggests that the former tend to entangle, in contrast to the latter which rebound impulsively.

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粒子的手性在强湍流的大尺度特征中并不重要。
我们利用立方域中均质各向同性湍流的三维直接数值模拟,研究了重型手性有限尺寸惯性粒子的动力学及其对流动的影响。利用沉浸边界法和复杂碰撞模型,进行了四向耦合模拟,并分析了颗粒与流体密度比、湍流强度和颗粒体积分数的影响。我们发现,自由下落的粒子一方面会增加湍流的能量,另一方面也会增强流体的耗散:根据流体参数的组合,前一种或后一种机制会占上风,从而产生增强或减弱的湍流。此外,粒子的奇异性还会导致优先角速度,从而在流体相中产生净涡度。随着湍流的增强,下落颗粒引入的能量变得不那么重要,更强的速度波动改变了固相动力学,使得手性效应与流动的大尺度特征无关。此外,比较手性粒子和球体(相同体积分数)碰撞事件的时间历史表明,前者倾向于缠结,而后者则是冲动反弹。
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来源期刊
CiteScore
6.50
自引率
27.00%
发文量
945
审稿时长
5.1 months
期刊介绍: Journal of Fluid Mechanics is the leading international journal in the field and is essential reading for all those concerned with developments in fluid mechanics. It publishes authoritative articles covering theoretical, computational and experimental investigations of all aspects of the mechanics of fluids. Each issue contains papers on both the fundamental aspects of fluid mechanics, and their applications to other fields such as aeronautics, astrophysics, biology, chemical and mechanical engineering, hydraulics, meteorology, oceanography, geology, acoustics and combustion.
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