Nadge, PM and Govardhan, RN (2011) Flow over a Backward Facing Step: Mean separation bubble and spanwise structure. In: 2011 IUTAM Symposium on Bluff Body Flows, Blubof 2011, 12 December 2011through 16 December 2011, Kanpur, pp. 124-127.
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The flow over a backward-facing step represents a conceptually simple case of a separating and reattaching flow, and has been studied extensively. In this paper, we present results about the internal structure of the mean separation bubble downstream of the step and the spanwise structure of the unsteady flow around the reattachment region. The measurements with PIV are done over a range of Reynolds numbers, 7000 < Reh < 67, 000, based on the step height (h) and for a range of expansion ratios, 1.11 < ER< 2.5 (ER = downstream channel height/upstream channel height). These measurements show that the reattachment length (Xr/h) becomes independent of Reynolds number for Reh>20, 000, for all expansion ratios. As the expansion ratio is increased, the reattachment length (Xr/h) is found to increase and reach a saturation value of 8.5 for ER>1.8. The internal structure of the mean separation bubble, when normalized by the reattachment length, is found to be nearly the same for high Reynolds numbers and for all expansion ratios investigated. In the spanwise-streamwise plane, instantaneous velocity fields obtained close to reattachment show streaky structures, similar to those seen in boundary layers. Conditional averaging of such velocity fields, show large-scale structures with length-scale of about 2 step-heights in the spanwise direction. © IUTAM Symposium on Bluff Body Flows, Blubof 2011.
| Item Type: | Conference Paper |
|---|---|
| Publication: | IUTAM Symposium on Bluff Body Flows, Blubof 2011 |
| Publisher: | Indian Institute of Technology, IIT, Kanpur |
| Additional Information: | The copyright for this article belongs to Indian Institute of Technology, IIT, Kanpur. |
| Keywords: | Boundary layers; Expansion; Facings, Channel height; Expansion ratio; Flows over a backward facing step; Internal structure; Reattachment length; Reynold number; Separation bubble; Spanwise structures; Step-height; Velocity field, Reynolds number |
| Department/Centre: | Division of Mechanical Sciences > Mechanical Engineering |
| Date Deposited: | 14 Sep 2024 11:02 |
| Last Modified: | 14 Sep 2024 11:02 |
| URI: | http://eprints.iisc.ac.in/id/eprint/84586 |
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