Inertial Particles in Wall-Bounded Turbulence: Turbophoresis, Wall-Modeled Large-Eddy Simulations, and Particle-Particle Collisions

Speaker: Perry Johnson, Center for Turbulence Research, Stanford University
May 14, 2019

Presentation

Abstract

In wall-bounded turbulent flows, heavy particles tend to accumulate in the near-wall region (viscous and buffer layers) due to a phenomenon known as turbophoresis. These enhanced particle concentration levels can depend strongly on the interaction of particles with coherent flow structures (rolls, streaks, etc.), which presents challenges for wall-modeled large-eddy simulations (LES). This talk will explain how the presence of near-wall structures influences particle dynamics and explore how the relative importance of this interaction depends on particle and flow properties, primarily the friction Stokes number. Implications for wall-modeled LES with Lagrangian particle tracking will be drawn and briefly demonstrated.

Further, as the bulk particle volume fraction increases, particle-particle collisions can play a significant role in attenuating the effect of turbophoresis. This strong sensitivity of turbophoresis to the bulk volume fraction poses difficulties for Lagrangian-Eulerian models of the particle phase with a reduced number of computational particles. A correction scheme for recovering collisional effects by artificially enhanced collisional diameter will be demonstrated, including both low and high Stokes number behaviors.

Biography

Perry Johnson received his Ph.D. in Mechanical Engineering from Johns Hopkins University (JHU) in 2017. At JHU, he was a National Science Foundation (NSF) Graduate Research Fellow and received the Corrsin Kovasznay outstanding paper award. He then joined the Center for Turbulence Research at Stanford University as a postdoctoral fellow. His research interests center on modeling and computing various features of turbulence and multiphase flow physics.

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