A unified sweep-stick mechanism to explain particle clustering in two- and three-dimensional homogeneous, isotropic turbulence

• Published in: Physics of fluids (1994) Vol. 21; no. 11
• Main Authors: COLEMAN, S. W, VASSILICOS, J. C
• Format: Journal Article
• Language: English
• Published: Melville, NY American Institute of Physics 01.11.2009
• Subjects: Exact sciences and technology; Fluid dynamics; Fundamental areas of phenomenology (including applications); Isotropic turbulence; homogeneous turbulence; Multiphase and particle-laden flows; Nonhomogeneous flows; Physics; Turbulent flows, convection, and heat transfer; Three dimensional flow; Particle cluster; Two-phase flow; Digital simulation; Modelling; Isotropic turbulence; Spherical particle; Particle suspension; Turbulence structure; Homogeneous turbulence
• ISSN: 1070-6631; 1089-7666
• DOI: 10.1063/1.3257638

Our work focuses on the sweep-stick mechanism of particle clustering in turbulent flows introduced by Chen et al. [L. Chen, S. Goto, and J. C. Vassilicos, “Turbulent clustering of stagnation points and inertial particles,” J. Fluid Mech. 553, 143 (2006)] for two-dimensional (2D) inverse cascading homogeneous, isotropic turbulence (HIT), whereby heavy particles cluster in a way that mimics the clustering of zero-acceleration points. We extend this phenomenology to three-dimensional (3D) HIT, where it was previously reported that zero-acceleration points were extremely rare. Having obtained a unified mechanism we quantify the Stokes number dependency of the probability of the heavy particles to be at zero-acceleration points and show that in the inertial range of Stokes numbers, the sweep-stick mechanism is dominant over the conventionally proposed mechanism of heavy particles being centrifuged from high vorticity regions to high strain regions. Finally, having a clustering coincidence between particles and zero-acceleration points, both in 2D and 3D HIT, motivates us to demonstrate the sweep and stick parts of the mechanism in both dimensions. The sweeping of regions of low acceleration regions by the local fluid velocity in both flows is demonstrated by introducing a velocity of the acceleration field. Finally, the stick part is demonstrated by showing that heavy particles statistically move with the same velocity as zero-acceleration points, while moving away from any nonzero-acceleration region, irrespective of their Stokes number. These results explain the clustering of inertial particles given the clustering of zero-acceleration points.