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PARTICLE-TURBULENCE INTERACTIONS IN THE PRESENCE OF A ROUGH WALL

Godwin F.K. Tay
Department of Mechanical and Manufacturing Engineering University of Manitoba Winnipeg, MB, Canada R3T 5V6

David C.S. Kuhn
Department of Mechanical and Manufacturing Engineering University of Manitoba Winnipeg, MB, Canada R3T 5V6

Mark F. Tachie
Department of Mechanical and Manufacturing Engineering, University of Manitoba, Winnipeg MB, R3T 5V6 Canada

Résumé

Experiments were conducted over smooth and rough walls in a low Reynolds number horizontal turbulent channel flow laden with small (64 µm) glass particles. A particle image velocimetry technique was used to measure velocities of both the carrier fluid and particles. Various turbulent characteristics were examined to investigate the impact of wall roughness on the particle-turbulence interactions. The results show that particles increased the turbulent intensities near the wall, and reduced them in the outer layer, but these effects were dampened for the rough wall. On the contrary, particles increased the peak value of the Reynolds shear stress in the presence of the rough wall when compared to the unladen flow. Particle velocity fluctuation intensities matched those of the unladen fluid for the smooth wall, but the peak velocity fluctuation intensities were enhanced in the presence of wall roughness due to particle-wall collisions. The effect is larger for the streamwise velocity fluctuation intensity than the wall-normal velocity fluctuation intensity. The present results indicate that the particle motion is more responsive to the presence of the rough wall than the particle-laden fluid.