Date of Award
M.S. in Engineering Science
Dr. Wen Wu
Dr. Taiho Yeom
Dr. Shan Jiang
Direct numerical simulations are carried out to study the flow separation in a channel flow rotating about the spanwise axis. A bump is introduced on one side of the channel by an immersed boundary method. The numerical schemes are studied, the solver is validated, and the computational domain and grid resolution requirements are determined. The characteristics of the separating flow behind the bump are described by comparing the flow at rotation numbers Ro = 0, 0.42, and 1.0. The bulk Reynolds number of the channel is 2,500. Both clockwise and counterclockwise rotations at these two rates are examined. The bump and the separated flow are under the anti-cyclonic effects of the Coriolis force when the rotation rate is positive, or cyclonic stabilization when the rotation is negative. When positive rotation unstabilizes the boundary layer, the separation on the bump surface is delayed, despite of the lower mean velocity near the wall than the one in the non-rotating case. The reattachment is also promoted by positive rotation and the separation bubble is almost eliminated at the high rotation number. Rotation augments the turbulence in the separated shear layer and generates stochastic small-scale eddies in the separating shear layer. When the rotation rate is negative, the bump is on the stable wall. Quasi-laminar flow is formed on this side of the channel. As the flow travels over the bump, it forms a laminar separation bubble that is more than twice the one in the non-rotating case in the average sense. The separated shear layer is quite stable. It eventually gets disturbed by the Tollmienâ€“Schlichting waves and quickly loses its coherence as the Coriolis force advects the disturbance to the wall and enhances the shear layer-wall interaction.
Patel, Devika Vipul, "FLOW SEPARATION IN ROTATING CHANNELS" (2022). Electronic Theses and Dissertations. 2264.
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