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Research Papers: Flows in Complex Systems

# Very Large Eddy Simulation of Passive Drag Control for a D-Shaped Cylinder

[+] Author and Article Information
Xingsi Han

e-mail: xingsi@chalmers.se

Siniša Krajnović

e-mail: sinisa@chalmers.se
Division of Fluid Dynamics,
Department of Applied Mechanics,
Chalmers University of Technology,
SE-412 96 Gothenburg, Sweden

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the Journal of Fluids Engineering. Manuscript received October 8, 2012; final manuscript received May 24, 2013; published online July 23, 2013. Assoc. Editor: Michael G. Olsen.

J. Fluids Eng 135(10), 101102 (Jul 23, 2013) (9 pages) Paper No: FE-12-1505; doi: 10.1115/1.4024654 History: Received October 08, 2012; Revised May 24, 2013

## Abstract

The numerical study reported here deals with the passive flow control around a two-dimensional D-shaped bluff body at a Reynolds number of $Re=3.6×104$. A small circular control cylinder located in the near wake behind the main bluff body is employed as a local disturbance of the shear layer and the wake. 3D simulations are carried out using a newly developed very large eddy simulation (VLES) method, based on the standard k − ε turbulence model. The aim of this study is to validate the performance of this method for the complex flow control problem. Numerical results are compared with available experimental data, including global flow parameters and velocity profiles. Good agreements are observed. Numerical results suggest that the bubble recirculation length is increased by about 36% by the local disturbance of the small cylinder, which compares well to the experimental observations in which the length is increased by about 38%. A drag reduction of about 18% is observed in the VLES simulation, which is quite close to the experimental value of 17.5%. It is found that the VLES method is able to predict the flow control problem quite well.

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## References

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## Figures

Fig. 1

The arrangement of the main bluff body and the control cylinder in one xOy plane [9]

Fig. 2

Distribution of the pressure coefficient around the main bluff body. Experimental data are from Ref. [9].

Fig. 3

Comparisons of time-averaged flow fields in the wake region given by experiment [9] and VLES method: (a) natural flow in experiment; (b) controlled flow in experiment; (c) natural flow by the VLES method; (d) controlled flow by the VLES method. The streamlines are projected on the central plane z/D = 0.

Fig. 4

Comparison of time-averaged streamwise velocity profiles. Experimental data are from Ref. [9].

Fig. 5

Isosurfaces of the computed spanwise vorticity ωZ by the VLES method: (a) natural flow and (b) controlled flow

Fig. 6

Comparison of the time-averaged velocities by the VLES method: (a) U/U0 in the natural flow; (b) V/U0 in the natural flow; (c) U/U0 in the controlled flow; (d) V/U0 in the controlled flow

Fig. 7

Comparison of the computed spanwise vorticity ωZ by the VLES method projected on the central plane z/D = 0: (a) natural flow and (b) controlled flow

Fig. 8

Comparison of the rms velocities by the VLES method: (a) Urms/U0 in the natural flow; (b) Urms/U0 in the controlled flow; (c) Vrms/U0 in the natural flow; (d) Vrms/U0 in the controlled flow; (e) Wrms/U0 in the natural flow; (f) Wrms/U0 in the controlled flow

Fig. 9

Comparison of the rms velocities along the central line of y/D = 0 by the VLES method on mesh M2 for the natural and controlled flows

Fig. 10

Contours of the instantaneous unresolved turbulent intensity by the VLES method: (a) natural flow on mesh M1; (b) controlled flow on mesh M1; (c) natural flow on mesh M2; (d) controlled flow on mesh M2

Fig. 11

Contours of the instantaneous turbulent viscosity ratio r = μt/μ by the VLES method: (a) natural flow on mesh M1; (b) controlled flow on mesh M1; (c) natural flow on mesh M2; (d) controlled flow on mesh M2

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