Side wall effects on the structure of laminar flow over a plane-symmetric sudden expansion

Computational investigations have been performed in order to study the side -wall effect on a fluid downstream of a channel expansion which is plane. T he expansion ratio under investigation is 3 and the aspect ratios are 3, 3. 5, 3.75, 3, 5, 6, 7, 8, 9, 10, 12, 18, 24, 48, in the three-dimensional ana lyses. For the flow with a value of Re = 60, results show symmetric nature of the flow when the channel aspect ratio has a value less than 3.5. Beyond this critical aspect ratio, flow symmetry can no longer be sustained due t o the Coanda effect. This confirms the experimental observation that a decr ease in aspect ratio has a stabilizing effect. Unless the aspect ratio is i ncreased further to a value above 12, flow in the third dimension plays an essential role to characterize the inherent nature of the flow. In this stu dy, we also confine ourselves to studying flow separation, reattachment, an d recirculation by employing a theoretically rigorous theory of topology. M uch insight into the vortical flow structure can be revealed from limiting streamlines, on which critical points, as spiral focal points and saddles, are plotted. (C) 2000 Elsevier Science Ltd. All rights reserved.