Computational Studies on Flow Separation Controls at Relatively Low Reynolds Number Regime

AbstractThe unsteady flow separation of airfoil with a local flexible structure (LFS) is studied numerically in Lagrangian frames in detail, in order to investigate the nature of its high aerodynamic performance. For such aeroelastic system, the characteristic-based split (CBS) scheme combined with arbitrary Lagrangian-Eulerian (ALE) framework is developed firstly for the numerical analysis of unsteady flow, and Galerkin method is used to approach the flexible structure. The local flexible skin of airfoil, which can lead to self-induced oscillations, is considered as unsteady perturbation to the flow. Then, the ensuing high aerodynamic performances and complex unsteady flow separation at low Reynolds number are studied by Lagrangian coherent structures (LCSs). The results show that the LFS has a significant influence on the unsteady flow separation, which is the key point for the lift enhancement. Specifically, the oscillations of the LFS can induce the generations of moving separation and vortex, which can enhance the kinetic energy transport from main flow to the boundary layer. The results could give a deep understand of the dynamics in unsteady flow separation and flow control for the flow over airfoil.

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Leading-edge tubercles delay flow separation for a tapered swept-back wing at very low Reynolds number

Ocean Engineering ◽

10.1016/j.oceaneng.2019.04.018 ◽

2019 ◽

Vol 181 ◽

pp. 173-184 ◽

Cited By ~ 2

Author(s):

Zhaoyu Wei ◽

T.H. New ◽

Lian Lian ◽

Yanni Zhang

Keyword(s):

Reynolds Number ◽

Flow Separation ◽

Low Reynolds Number ◽

Leading Edge ◽

Low Reynolds

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Study on flow separation and transition of the airfoil in low Reynolds number

Physics of Fluids ◽

10.1063/1.5118736 ◽

2019 ◽

Vol 31 (10) ◽

pp. 103601 ◽

Cited By ~ 5

Author(s):

B. C. Khoo

Keyword(s):

Reynolds Number ◽

Flow Separation ◽

Low Reynolds Number ◽

Low Reynolds

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Numerical and Experimental Investigation of Low Reynolds Number Effects on Laminar Flow Separation and Transition in a Cascade of Compressor Blades

Volume 3: Heat Transfer; Electric Power; Industrial and Cogeneration ◽

10.1115/2000-gt-0276 ◽

2000 ◽

Cited By ~ 1

Author(s):

Shunji Enomoto ◽

C. Hah ◽

G. V. Hobson

Keyword(s):

Reynolds Number ◽

Laminar Flow ◽

Flow Separation ◽

Low Reynolds Number ◽

Numerical Procedure ◽

Compressor Blade ◽

Navier Stokes ◽

Flow Transition ◽

Reynolds Number Effects ◽

Low Reynolds

The results of an experimental and numerical comparison of the effects of low Reynolds number on flow separation and transition in a controlled-diffusion compressor cascade are presented. The flow separation and subsequent flow transition are associated with low Reynolds number effects in the compressor blade rows. Current steady-state Reynolds-averaged Navier-Stokes codes with available turbulence and transition models do not calculate the current flow phenomena properly. An unsteady three-dimensional Navier-Stokes calculation that applies a third-order accurate upwind method has been performed and the numerical results are compared to the measurements in detail. The results from the current numerical procedure agree very well with the measurements in terms of laminar flow separation, reattachment, and subsequent flow transition at low Reynolds numbers. The present study indicates that flow separation and flow transition inside compressor blade rows at low Reynolds number are phenomena dominated by relatively larger eddies near the wall and can be simulated with the current type of unsteady numerical procedure.

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