Experimental and Numerical Investigations of Plane Duct Flows With Sudden Contraction

Abstract

The present paper reports on experimental and numerical studies of laminar, two-dimensional flow through plane ducts with sudden contractions in cross-sectional area. A laser-Doppler anemometer and a flow computational program were complementarity employed to study details of the flow close to the step. The results reveal details of the velocity profile variations in the vicinity of the contraction. Information is also provided on the separated flow region in the front concave corner of the duct and on the separated flow region just downstream of the lip of the step. The dimensions of the front separation region are shown to agree well with existing data. The recirculating flow region just downstream of the lip is much smaller than occasionally assumed. At higher contraction ratios off-axis velocity maxima occur just downstream of the contraction. It is shown that strong elongational flow fields occur. These are concentrated to a very small region close to the step.