Effect of Expansion Ratio on Fluid Flow Characteristics of Channel Flow with a Backward-Facing Step

Abstract

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 the 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.