THE EFFECT OF INLET CONDITIONS ON FLOW OVER BACKWARD-FACING STEP

The objectives of this paper are to present measurements of physical p henomena associated with two-dimensional separation of a turbulent bou ndary layer over a backward-facing step (B.W.F.S.). Two flow condition s were studied: Sharp leading edge (S.E.) with flow underneath (Case I ) and blunt leading edge (B.E.) with flow underneath (Case II). The co mparisons between the two cases are discussed with reference to change s in: (i) The potential flow. (ii) The free shear layer surrounding th e bubbles. (iii) The separation condition (separation point, shape of bubbles, reattachment point, etc.). All the experiments on the full sc ale model were carried out inside an open-circuit low-speed wind tunne l. The experiments were carried out at a Reynolds number of Re-H = 7.9 x 10(4) based on step height H. Measurements were made of the longitu dinal, (U) over bar, and vertical, (V) over bar, components of the mea n velocity, the two normal stress components (u) over bar(-2) and, (v) over bar(-2) and the shear stress <(uv)over bar>. These data were obt ained using the Flying Hot-Wire (F.H.W.) anemometer. The F.H.W. anemom eter can be used with minimal flow interference. The experimental inve stigations have shown significant differences between the recirculatin g regions associated with the two conditions studied due to different inlet conditions. (C) 1998 Elsevier Science Ltd. All rights reserved.