Bulletin of the American Physical Society
76th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 19–21, 2023; Washington, DC
Session T37: Separated Flows: Experiments
4:25 PM–6:09 PM,
Monday, November 20, 2023
Room: 203AB
Chair: Karen Mulleners, École polytechnique fédérale de Lausanne (EPFL)
Abstract: T37.00004 : Unsteadiness in turbulent separated flow over a three-dimensional Gaussian hill*
5:04 PM–5:17 PM
Presenter:
Kevin H Manohar
(University of Calgary)
Authors:
Kevin H Manohar
(University of Calgary)
Hariprasad Annamalai
(GE Aerospace)
Owen Williams
(University of Washington)
Robert J Martinuzzi
(University of Calgary)
Chris Morton
(McMaster University)
The flow is dominated by four key frequencies at Re = 226,000 based on the bump height. Two low frequencies are associated with motions of the separation front, while a third, higher frequency results from shear layer vortex shedding observed only along the centreline symmetry plane. Notably, a very low-frequency side-to-side spanwise oscillation of the recirculation zone is observed. The Strouhal number of this oscillation is similar to those seen in other hill-type geometries, but the Bump flow does not exhibit the random switching instability reported for these flows. Proper orthogonal decomposition reveals the anti-symmetric spanwise oscillation interacting with other symmetric modes governing the streamwise length of the recirculation zone. Moreover, the mean field shows that the separated streamsurface does not reattach back onto the wall; instead, a second separation event occurs downstream with centreline upwash.
*The authors thank the Natural Sciences and Engineering Research Council (NSERC) of Canada for their support through the Discovery Grant, Research Tool & Instrumentation and Postgraduate Scholarship programs as well as the Government of Alberta through the AGES and Alberta Innovates graduate scholarships. The authors would also like to gratefully acknowledge funding from Boeing Commercial Airplanes that has supported the creation of the Gaussian speed-bump test case and the test articles at the University of Washington used in this study.
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