Large-eddy simulation of separation and reattachment of a flat plate turbulent boundary layer

Cheng, W.; Pullin, D. I.; Samtaney, Ravi

Large-eddy simulation of separation and reattachment of a flat plate turbulent boundary layer

Type

Article

Authors

Cheng, W.

Pullin, D. I.
Samtaney, Ravi

KAUST Department

Fluid and Plasma Simulation Group (FPS)
Mechanical Engineering Program
Physical Science and Engineering (PSE) Division

KAUST Grant Number

URF/1/1394-01

Online Publication Date

2015-11-11

Print Publication Date

2015-12

Date

2015-11-11

Abstract

© 2015 Cambridge University Press. We present large-eddy simulations (LES) of separation and reattachment of a flat-plate turbulent boundary-layer flow. Instead of resolving the near wall region, we develop a two-dimensional virtual wall model which can calculate the time- and space-dependent skin-friction vector field at the wall, at the resolved scale. By combining the virtual-wall model with the stretched-vortex subgrid-scale (SGS) model, we construct a self-consistent framework for the LES of separating and reattaching turbulent wall-bounded flows at large Reynolds numbers. The present LES methodology is applied to two different experimental flows designed to produce separation/reattachment of a flat-plate turbulent boundary layer at medium Reynolds number Reθ based on the momentum boundary-layer thickness θ. Comparison with data from the first case at demonstrates the present capability for accurate calculation of the variation, with the streamwise co-ordinate up to separation, of the skin friction coefficient, Reθ, the boundary-layer shape factor and a non-dimensional pressure-gradient parameter. Additionally the main large-scale features of the separation bubble, including the mean streamwise velocity profiles, show good agreement with experiment. At the larger Reθ = 11000 of the second case, the LES provides good postdiction of the measured skin-friction variation along the whole streamwise extent of the experiment, consisting of a very strong adverse pressure gradient leading to separation within the separation bubble itself, and in the recovering or reattachment region of strongly-favourable pressure gradient. Overall, the present two-dimensional wall model used in LES appears to be capable of capturing the quantitative features of a separation-reattachment turbulent boundary-layer flow at low to moderately large Reynolds numbers.

Citation

Cheng W, Pullin DI, Samtaney R (2015) Large-eddy simulation of separation and reattachment of a flat plate turbulent boundary layer. Journal of Fluid Mechanics 785: 78–108. Available: http://dx.doi.org/10.1017/jfm.2015.604.

Acknowledgements

W.C. and R.S. were supported by the KAUST Office of Competitive Research Funds (OCRF) under Award No. URF/1/1394-01. D.I.P. was partially supported under KAUST OCRF Award No. URF/1/1394-01 and partially by NSF award CBET 1235605.