2018/11/16 by V. Kumaran, Kumaran, V., Pradeep Muramalla +5
Earth and Planetary Sciences · Engineering · #Aeolian processes and effects #FOS: Physical sciences #Fluid Dynamics (physics.flu-dyn) #Granular flow and fluidized beds #Particle Dynamics in Fluid Flows
paper · pdf · doi:10.48550/arxiv.1811.06694
openalex publication_date 2018/11/16 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Two mechanisms are considered responsible for the turbulence modification due\nto suspended particles in a turbulent gas-particle suspension. Turbulence\naugmentation is due to the enhancement of fluctuations by wakes behind\nparticles, whereas turbulence attenuation is considered to result from the\nincreased dissipation due to the particle drag. In order to examine the\nturbulence attenuation mechanism, Direct Numerical Simulations (DNS) of a\nparticle-gas suspension are carried out at a Reynolds number of about 3333\nbased on the average gas velocity \u, channel width h, and the gas\nkinematic viscosity. The particle Reynolds number based on the particle\ndiameter dp, gas kinematic viscosity and the flow velocity \u is\nabout 42 and the Stokes number is in the range 7-450. The particle volume\nfraction is in the range 0-2 \× 10-3, and the particle mass loading is\nin the range 0-9. As the volume fraction is increased, a discontinuous\ndecrease in the turbulent velocity fluctuations is observed at a critical\nvolume fraction. from 9 \× 10-4 to 1 \× 10-3. There is a\nreduction, by one order of magnitude, in the mean square fluctuating velocities\nin all directions and in the Reynolds stress. Though there is a modest increase\nin the energy dissipation due to particle drag, this increase is smaller than\nthe decrease in the turbulent energy production; moreover, there is a decrease\nin the total energy dissipation rate when there is turbulence collapse. Thus,\nturbulence attenuation appears to be due to a disruption of the turbulence\nproduction mechanism, and not due to the increased dissipation due to the\nparticles. There is a discontinuous collapse in the turbulence intensities at a\ncritical particle loading, instead of the continuous decrease as the particle\nloading is increased.\n