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. The 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 analyses. 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 to the Coanda effect. This confirms the experimental observation that a decrease in aspect ratio has a stabilizing effect. Unless the aspect ratio is increased 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 study, we also confine ourselves to studying flow separation, reattachment, and recirculation by employing a theoretically rigorous theory of topology. Much 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.