Effect of Reynolds number and concentration on modulation of turbulence by finite size neutrally buoyant particles.
Résumé
Direct numerical simulations of particle laden flow are carried out with the Force-Coupling Method to study the effect of finitesize neutrally buoyant particles on turbulent plane Couette flow. Two particle sizes and various concentrations (from 1 to 10%) are investigated for different Reynolds numbers above the transition to turbulence. Our results show that particle dispersion is determined by a balance between hydrodynamic wall repulsion, turbulent mixing and particle induced self-diffusion. Due to the presence of particles, close to the wall, turbulence intensity is attenuated in streamwise direction but is increased in wall-normal direction. This effect is enhanced by larger particles. The stress budget is also modified with two additional components, originating from particle rigidity (Stresslet) and particle Reynolds stress. The Stresslet contribution is stronger near the wall where the strain rate is the largest whereas maximum particle turbulent stress occurs in the core region where cross-gradient mixing is induced by turbulent flow structures. Reynolds stress budgets show no significant modulation of flow turbulence by particles. The viscous dissipation rate is the main component enhanced by particles near the transition threshold.
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