後向きステップを有するチャネル流れにおける流路拡大比とレイノルズ数の効果

抄録

The effects of expansion ratio and Reynolds number on backward-facing step flow are investigated experimentally. The expansion ratio ER is changed to 1.5, 1.75 and 2.0, and the Reynolds number based on the mean velocity and the hydraulic diameter of inlet channel ranges from 1.5 × 10³ to 6.0 × 10³ . The Reynolds number range includes laminar, transition and turbulent flows. The forward flow fraction γ and local skin friction factor C_f are measured using a micro flow sensor. In the laminar region, the distributions of γ, C_f and wall static pressure change greatly between ER = 1.5 and ER = 1.75. In the turbulent region, there is no significant difference in these distributions even if the ER is different. The reattachment length non-dimensionalized at the step height decreases when the flow upstream of the step transitions from the laminar to the turbulent, and is minimized when ER = 2.