April 4 2017, 2.30 pm

COLLISION STATISTICS IN PARTICLE-LADEN TURBULENT CHANNEL FLOW

 Prof. J.G.M. Kuerten - Eindhoven University of Technology, Department of Mechanical Engineering

Sala Ferrari (II piano), DIMEAS, Politecnico di Torino

Abstract

For particle-laden homogeneous isotropic turbulence it is usually assumed that particle collisions are not important if the particle volume fraction is less than 10^-3. In turbulent channel flow much higher particle volume fractions can locally occur due to turbophoresis and particle clustering. In the low-speed streaks close to the walls of the channel local particle volume fractions can be up to two orders of magnitude larger than the mean particle volume fraction.

We investigated the effects of particle collisions for this flow at two Reynolds numbers and studied the particle collision rate. Since the determination of particle collisions is computationally expensive expressions for the particle collision rate are important in order to enable stochastic collision modeling. An unwanted phenomenon in point-particle DNS is the occurrence of repeated collisions, i.e. collisions between the same two particles in rapid succession. We propose a method to exclude these unphysical collisions and show that this methods results in good agreement between the observed collision rate and a theoretical model.

Official seminar announcement at Polito Web Page is available here.