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Large-eddy simulation of flow over a rotating cylinder: the lift crisis at Re_D = 6 × 10^4

Cheng, W. and Pullin, D. I. and Samtaney, R. (2018) Large-eddy simulation of flow over a rotating cylinder: the lift crisis at Re_D = 6 × 10^4. Journal of Fluid Mechanics, 855 . pp. 371-407. ISSN 0022-1120. http://resolver.caltech.edu/CaltechAUTHORS:20181008-151606899

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Abstract

We present wall-resolved large-eddy simulation (LES) of flow with free-stream velocity U∞ over a cylinder of diameter D rotating at constant angular velocity Ω, with the focus on the lift crisis, which takes place at relatively high Reynolds number Re_D = U∞D/ν, where ν is the kinematic viscosity of the fluid. Two sets of LES are performed within the (ReD, α)-plane with α = ΩD/(2U∞) the dimensionless cylinder rotation speed. One set, at Re_D = 5000, is used as a reference flow and does not exhibit a lift crisis. Our main LES varies α in 0 ⩽ α ⩽ 2.0 at fixed Re_D = 6×10^4. For α in the range α = 0.48−0.6 we find a lift crisis. This range is in agreement with experiment although the LES shows a deeper local minimum in the lift coefficient than the measured value. Diagnostics that include instantaneous surface portraits of the surface skin-friction vector field C_f, spanwise-averaged flow-streamline plots, and a statistical analysis of local, near-surface flow reversal show that, on the leeward-bottom cylinder surface, the flow experiences large-scale reorganization as α increases through the lift crisis. At α = 0.48 the primary-flow features comprise a shear layer separating from that side of the cylinder that moves with the free stream and a pattern of oscillatory but largely attached flow zones surrounded by scattered patches of local flow separation/reattachment on the lee and underside of the cylinder surface. Large-scale, unsteady vortex shedding is observed. At α = 0.6 the flow has transitioned to a more ordered state where the small-scale separation/reattachment cells concentrate into a relatively narrow zone with largely attached flow elsewhere. This induces a low-pressure region which produces a sudden decrease in lift and hence the lift crisis. Through this process, the boundary layer does not show classical turbulence behaviour. As α is further increased at constant Re_D, the localized separation zone dissipates with corresponding attached flow on most of the cylinder surface. The lift coefficient then resumes its increasing trend. A logarithmic region is found within the boundary layer at α = 1.0.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1017/jfm.2018.644DOIArticle
ORCID:
AuthorORCID
Cheng, W.0000-0003-3960-4162
Samtaney, R.0000-0002-4702-6473
Additional Information:© 2018 Cambridge University Press. Received 22 February 2018; revised 28 June 2018; accepted 5 August 2018; first published online 19 September 2018. This work was partially supported by the KAUST baseline research funds of R.S. The Cray XC40, Shaheen, at KAUST was utilized for all the reported LES.
Funders:
Funding AgencyGrant Number
King Abdullah University of Science and Technology (KAUST)UNSPECIFIED
Subject Keywords:Boundary Layers: Boundary layer separation; Boundary Layers: Boundary Layers; Turbulent Flows: Turbulence simulation
Record Number:CaltechAUTHORS:20181008-151606899
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20181008-151606899
Official Citation:Cheng, W., Pullin, D., & Samtaney, R. (2018). Large-eddy simulation of flow over a rotating cylinder: The lift crisis at Re_D = 6 × 10^4. Journal of Fluid Mechanics, 855, 371-407. doi:10.1017/jfm.2018.644
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:90164
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:08 Oct 2018 22:34
Last Modified:08 Oct 2018 22:34

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