低レイノルズ数域における十分発達したチャネル流に対する粗さの影響

抄録

The effect of surface roughness arranged on one wall was investigated for a fully developed channel flow at low Reynolds numbers. The surface roughness was arranged with the roughness pitch ratio PR=2, 4 and 8. The friction coefficient was estimated from wall static pressure distribution. The streamwise mean velocity was measured with a particle image velocimetry. The Reynolds numbers were set in the range of R_eH ≅1000-6000, where R_eH is the Reynold number based on the channel height. The friction coefficient profile of PR=2 behaves like the transition from laminar to turbulent flows for R_eH <2000. The value of the friction coefficient increases with PR. For R_eH ≅1500, the value of the streamwise mean velocity profile of PR=2 is decreased near the channel center and increased near the walls compared to the parabolic profile of the laminar flow between parallel plates, but the profiles of PR=4 and 8 are decreased in the lower plate side with the surface roughness and increased in the upper plate side. For R_eH ≅2000, the velocity profile becomes nearly flat near the centerline of the channel for PR=2 and is almost similar to that of R_eH ≅1500 for PR=4 and 8.