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Research Papers: Fundamental Issues and Canonical Flows

Large-Eddy Simulation of Wake and Boundary Layer Interactions Behind a Circular Cylinder

[+] Author and Article Information
S. Sarkar1

Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur-208016, Indiasubra@iitk.ac.in

Sudipto Sarkar

Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur-208016, India

1

Corresponding author.

J. Fluids Eng 131(9), 091201 (Aug 14, 2009) (13 pages) doi:10.1115/1.3176982 History: Received October 23, 2008; Revised June 16, 2009; Published August 14, 2009

Large-eddy simulations (LESs) of flow past a circular cylinder in the vicinity of a flat plate have been carried out for three different gap-to-diameter (G/D) ratios of 0.25, 0.5, and 1.0 (where G signifies the gap between the flat plate and the cylinder, and D signifies the cylinder diameter) following the experiment of Price (2002, “Flow Visualization Around a Circular Cylinder Near to a Plane Wall,” J. Fluids Struct., 16, pp. 175–191). The flow visualization along with turbulent statistics are presented for a Reynolds number of Re=1440 (based on D and the inlet free-stream velocity U). The three-dimensional time-dependent, incompressible Navier–Stokes equations are solved using a symmetry-preserving finite-difference scheme of second-order spatial and temporal accuracy. The immersed-boundary method is employed to impose the no-slip boundary condition at the cylinder surface. An attempt is made to understand the physics of flow involving interactions of shear layers shed from the cylinder and the wall boundary layer. Present LES reveals the shear layer instability and formation of small-scale eddies apart from their mutual interactions with the boundary layer. It has been observed that G/D ratio has a large influence on the modification of wake dynamics and evolution of the wall boundary layer. For a low gap ratio, it is difficult to identify the boundary layer because of its strong interactions with the shear layers; however, a rapid transition to turbulence of the boundary layer, which is similar to bypass transition, is observed for a large gap ratio.

Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 2

Grid independent test for G=0.25D and Re=1440 considering (a) mean streamline velocity (U¯/U∞) and (b) turbulent kinetic energy profiles at different streamwise locations: –⋅–⋅–288×192×32 (grid 1), – – – 384×160×32 (grid 2), — 384×192×32 (grid 3), and ⋯⋯⋅⋅384×192×64 (grid 4)

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Figure 3

Instantaneous spanwise vorticity (ωz): (a) and (b) experiment at Re=1900(1); (c) and (d) present LES at Re=1440. (a) and (c) G/D=0.25 and (b) and (d) G/D=0.5.

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Figure 4

Power spectra density of streamwise velocity at x/D=3.3, y/D=1.5 for Re=1440, and G/D=0.25: — present LES, ⋯ experiment (1)

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Figure 5

Span averaged vorticity contours for G/D=0.25. A total of 20 nondimensional contours are considered in between −5 and +5. The negative vorticity is represented by dotted line.

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Figure 6

Span averaged vorticity contours for G/D=0.5. For details refer Fig. 5.

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Figure 1

Computational configuration and boundary conditions

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Figure 11

The mean (a) streamwise and wall-normal velocity contours and (b) coefficient of pressure distributions for different G/D. Streamwise velocity contours are drawn by flood and wall-normal velocity contours are drawn by line (black color) diagrams. The thick white line indicates zero contour level for mean streamwise velocity.

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Figure 12

Profiles of Cf for G/D=0.25, 0.5, and 1.0. The solid lines indicate Cf¯ and the dotted lines are corresponding instantaneous Cf separated by 0.2T. Turbulent Cf profile is obtained from the correlation Cf=0.058/Rex1/5.

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Figure 13

Isosurfaces of spanwise vorticity (ωz=±2.0) for G/D=0.25, 0.5, and 1.0

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Figure 14

Streamwise velocity contour and vector plot of velocity fluctuations (u′,v′) for (a) front view (x-y plane) along with a zoomed section, (b) top view (x-z plane) considering a gap ratio of G/D=1.0. For better visualization, two vectors are skipped in the x-direction and four vectors in the y-direction, respectively.

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Figure 15

Spanwise correlation functions of the streamwise and the wall-normal velocity fluctuations

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Figure 16

Time-averaged nondimensional urms near the wall: (a) between x/D=3.5–5.0 and (b) after x/D=7.5

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Figure 17

Streamwise velocity contour and vector plot of velocity fluctuations (u′,v′) for (a) front view (x-y plane) and (b) side views (y-z plane) considering a gap ratio of G/D=0.5. For details refer Fig. 1.

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Figure 18

The power spectra at Re=1440 for G/D=0.5: (a) streamwise velocity and (b) spanwise velocity

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Figure 19

Profiles of streamwise mean and rms velocity along with the Blasius solution for G/D=0.25, 0.5, and 1.0 at x/D=2, 3, 5, 7, 10, and 15; — U¯/U∞, – – – urms/U∞, ⋯⋯⋅⋅ Blasius solution

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Figure 20

Time-averaged nondimensional turbulent kinetic energy productions near the wall and after x/D=7.5

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Figure 21

Profiles of turbulent kinetic energy and production for G/D=0.25, 0.5, and 1.0 at x/D=2, 3, 5, 7, 10, and 15; — TKE, – – – production

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Figure 7

Span averaged vorticity contours for G/D=1.0. For details refer Fig. 5.

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Figure 8

(a) Trajectory of vortex peak and (b) variation in ωz peak for G/D=0.25 and Re=1440

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Figure 9

(a) Trajectory of vortex peak and (b) variation in ωz peak for G/D=1.0 and Re=1440

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Figure 10

Mean streamlines for G/D=0.25, 0.5, and 1.0

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