Effect of the particle-induced turbulence-modification on two-equation models for particle-laden wall-bounded turbulent flows

Abstract

It is noted that in particle-laden flows, the particles generally promotes large changes in the turbulence characteristics of the fluid. This chapter illustrates two-equation models for particle-laden wall-bounded turbulent flows, in particular, the k-ɛ model that takes into account only the direct interaction between the particles and the surrounding fluid, and do not consider the indirect effects, due to the disruption the particles being promoted in the turbulence dynamics itself. This disruption can promote large changes in the "standard values" of the constants of the k-ɛ model. This chapter illustrates the influence of the particle-turbulence interaction on the k-ɛ model, using point-particle Eulerian- Lagrangian DNS/LES simulations, in a fully-developed turbulent channel flow laden with small heavy spheric particles. It focuses on the effect the particles have on the constant Cμ, associated with the kinematic eddy-viscosity. The particles promote large non-uniform changes in the value of Cμ which can increase or decrease, depending on the distance to the wall and the Reynolds number. The particles promote a large uniform decrease in the value of the kinematic eddy-viscosity suggesting that in simple wall-bounded flows it can be possible to take into account the effect of the particles on the kinematic eddy- viscosity using simpler mixing-length models, without the use of a two-equation framework.