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.

Asymmetry and bifurcations in three-dimensional sudden-contraction channel flows

“…1) may be characterized as (i) the formation of two recirculating eddies at the upstream salient corners and (ii) the growth of two separation bubbles (tip corner eddies) immediately downstream of the plane of contraction. Notably, while most of the available investigations (e.g., Dennis and Smith [2], Durst and Loy [3], Durst et al [4], Hawken et al [5], and Huang and Seymour [6]) on the topic remained concerned with two-dimensional (2D) flow behaviors observed at moderate Reynolds numbers, almost all practical flow situations are, however, inherently three dimensional and they often occur at a relatively higher Reynolds number (Re). Notably, in three dimensions the physically sensitive critical parameters in a sudden-contraction flow are the aspect ratio A, the contraction ratio C, and the Re.…”

“…Notably, most of the existing investigations (e.g., Refs. [2,[4][5][6]) preassumed the symmetric nature of the flow and often conducted 2D simulations in the half-channel. However, our simulated results, covering a wide range of physically sensitive parameter spaces, clearly indicate that the pitchfork bifurcation remains inherently the strongest feature of 3D plane sudden-contraction channel flows.…”

The behaviour of macromolecules in the flow through a sudden planar contraction

“…Assuming the flow of the Newtonian solvent to be laminar, steady and two-dimensional, the momentum and continuity equations were solved using the computer program TEACH (as described by Gosman and Ideriah [9]). Different Reynolds numbers and different contraction ratios fl = D/d were calculated and good agreement with experimental results was obtained [4]• For the present work the contraction ratio fi = 2 was chosen. The Reynolds numbers Re (based on the upstream gap D) considered were 53 and 1326, respectively.…”

Numerical solution of the steady, compressible, Navier-Stokes equations in two and three dimensions by a coupled space-marching method

“…The predicted centerline velocity distributions are shown in Figure 5.25 along with the experimental results of Durst et al [84].…”

“…Mei and Plotkin were able to demonstrate a reasonable degree of mesh independence in their solutions. The very high gradients near the contraction also produced a large degree of uncertainty in the experimental data of Durst et al [84].…”