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Article

Fluid stress balance in a turbulent particulate channel flow

Authors: Fukagata, K., Zahrai, S., Bark, F.H.
Document Type: Conference
Pubstate: Published
Journal: Proc. 3rd Int. Conf. On Multiphase flow, Lyon, France, 8-12 June
Volume: P157   1-8
Year: 1998

Abstract

Large eddy simulations of particulate two-phase flow were carried out taking into account the modulation of fluid velocity field due to the presence of particles. Since the density ratio of particle to fluid considered is of the order of $10^3$, the coupling from particle to fluid was modeled by adding the reaction forces from the drag force as a body force to the fluid.

Two cases, one of relatively low mass loading with 50 micron glass particles and one of high mass loading with 70 micron copper particles, were simulated and compared with the statistics from the one-way coupling simulations with the same parameters. In both cases, RMS levels of transverse fluid velocities in two-way coupling simulations were found to be lower than those predicted by one-way coupling simulations.

Particle force balance was shown to be satisfied also in the case of two-way coupling simulations. Similarly to the cases of one-way coupling, the drag force in the wall-normal direction was found to balance the transport of particle flux by turbulence.

Modulation of turbulent structure near the wall were observed. In the case of glass particles at mass flow ratio of 0.30, longer fluid velocity streaks compared to those in undisturbed flows were observed. In the case of copper particles at mass flow ratio of 3.04, the turbulent structure was found to be completely destroyed.

Apart from the simulations, a relation between the mean shear stress, the Reynolds stress and the interphase force was derived from the Navier-Stokes equation taking into account the interphase forces. The derived relation was compared with the data obtained from the simulation. The contribution from particle stress was found to be about half of the Reynolds stress in the case with 50 micron glass particles at low loading ratio. The Reynolds stresse was strongly damped in the case of 70 micron copper particles at high loading ratio.