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Research Papers: Flows in Complex Systems

Experimental Investigation of Flow Over a Transversely Oscillating Square Cylinder at Intermediate Reynolds Number

[+] Author and Article Information
Manish Kumar Chauhan

Mechanical and
Industrial Engineering Department,
Indian Institute of Technology, Roorkee,
Roorkee, Uttarakhand 247667, India
e-mail: manishku.25@gmail.com

Sushanta Dutta

Associate Professor
Mem. ASME
Mechanical and
Industrial Engineering Department,
Indian Institute of Technology, Roorkee,
Roorkee, Uttarakhand 247667, India
e-mail: duttafme@iitr.ac.in

Bhupendra Kumar Gandhi

Professor
Mem. ASME
Mechanical and
Industrial Engineering Department,
Indian Institute of Technology, Roorkee,
Roorkee, Uttarakhand 247667, India
e-mail: bkgmefme@iitr.ac.in

Bhupendra Singh More

Mechanical and
Industrial Engineering Department,
Indian Institute of Technology, Roorkee,
Roorkee, Uttarakhand 247667, India
e-mail: bmore812@gmail.com

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received April 9, 2015; final manuscript received October 16, 2015; published online January 6, 2016. Assoc. Editor: Peter Vorobieff.

J. Fluids Eng 138(5), 051105 (Jan 06, 2016) (19 pages) Paper No: FE-15-1251; doi: 10.1115/1.4031878 History: Received April 09, 2015; Revised October 16, 2015

This paper presents an experimental study of flow over a square cylinder oscillating in transverse direction. The Reynolds number selected for present study is 485. Limited study has also been made for two other Reynolds numbers, namely, 295 and 775. The objective of the present study is to modify the near-wake flow structure using actuation of the cylinder for possible reduction in drag force. Transverse oscillations to the cylinder are provided using electromagnetic actuators. The flow field is investigated using two-dimensional (2D)-particle image velocimetry (PIV) system, hotwire anemometer (HWA), as well as flow visualization techniques. The effect of oscillation frequency and the amplitude on parameters like Strouhal number, drag coefficient, recirculation length, power spectrum, and Reynolds stress are studied. It is observed that the recirculation length is reduced significantly with increase in forcing frequency, and consequently drag coefficient is also reduced. For a constant forcing frequency, the vortex strength is reduced with the increase in the amplitude. Further, variation of instantaneous spanwise vorticity shows that separated shear length decreases with increase in forcing frequency. As a result, vortices are moved closer to the cylinder. These phenomena affect the forces acting on the cylinder. Lock-on is also observed at a frequency close to the vortex shedding frequency of the stationary cylinder.

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References

Figures

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Fig. 1

Schematic diagram of experimental setup

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Fig. 2

Schematic diagram of oscillation arrangement of a square cylinder

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Fig. 3

Comparison of Strouhal number with literature for flow over a stationary square cylinder

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Fig. 4

Drag coefficient values at different Reynolds numbers and comparison with literature

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Fig. 5

Flow visualization for transverse oscillation of a circular cylinder (top, Ref. [15]) and of a square cylinder (bottom, present) at f/f0 = 1 and A/D = 0.1

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Fig. 6

Drag coefficient as a function of Reynolds number with different oscillation frequency ratio at A/D = 0.1

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Fig. 7

Strouhal number variation with Reynolds number for different forcing frequency at fixed A/D = 0.1

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Fig. 8

Time-averaged nondimensionalized velocity vectors and contours of an oscillating cylinder at Re = 485, AR = 50, and A/D = 0.1

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Fig. 9

Time-averaged nondimensionalized u-velocity profiles of an oscillating cylinder at Re = 485 and A/D = 0.1

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Fig. 10

Time-averaged nondimensionalized v-velocity profiles of an oscillating cylinder at Re = 485 and A/D = 0.1

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Fig. 11

Time-averaged streamlines in wake of an oscillating cylinder at Re = 485 and A/D = 0.1

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Fig. 12

Nondimensionalized centerline velocity recovery in streamwise direction (left) of transverse oscillating frequencies (present study) and centerline recovery at inline cylinder oscillation (right, Ref. [5])

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Fig. 13

Nondimensionalized fluctuating velocity development along centerline in streamwise direction (left) and transverse direction (right) at various oscillating frequencies, Re = 485 and A/D = 0.1

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Fig. 14

Power spectra of v-velocity in the wake of an oscillating cylinder at different frequency ratio, A/D = 0.1 and Re = 485

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Fig. 15

Instantaneous nondimensionalized spanwise vorticity contours (ωz) at particular instants in the wake of a stationary cylinder at Re = 485. Maximum, minimum, and increments in ωz are 4.0, − 4.0, and 0.5.

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Fig. 16

Instantaneous nondimensionalized spanwise vorticity contours (ωz) at particular instants in the wake of an oscillating cylinder at frequency ratio (f/f0) = 0.5; A/D = 0.1; and Re = 485. Maximum, minimum, and increments in ωz are 4.0, −4.0, and 0.5.

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Fig. 17

Instantaneous nondimensionalized spanwise vorticity contours (ωz) at particular instants in the wake of an oscillating cylinder at frequency ratio (f/f0) = 1.0; A/D = 0.1; and Re = 485. Maximum, minimum, and increments in ωz are 4.0, −4.0, and 0.5.

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Fig. 18

Instantaneous nondimensionalized spanwise vorticity contours (ωz) at particular instants in the wake of an oscillating cylinder at frequency ratio (f/f0) = 2.0; A/D = 0.1; and Re = 485. Maximum, minimum, and increments in ωz are 4.0, −4.0, and 0.5.

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Fig. 19

Time-averaged spanwise vorticity contours (ωz) in the wake of an oscillating cylinder for various frequency ratios (f/f0 = 0, 0.5, 1, and 2), Re = 485, and A/D = 0.1

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Fig. 20

Time-averaged nondimensionalized streamwise fluctuating velocity (urms) contours of an oscillating square cylinder. f/f0 = 0, 0.5, 1, and 2; A/D = 0.1; and Re = 485.

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Fig. 21

Time-averaged nondimensionalized transverse fluctuating component of velocity (vrms) of an oscillating square cylinder at Re = 485 and A/D = 0.1

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Fig. 22

Nondimensionalized turbulent kinetic energy production for stationary and oscillating square cylinder at Re = 485 and A/D = 0.1

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Fig. 23

Nondimensionalized turbulent kinetic energy dissipation for stationary and oscillating square cylinder at Re = 485 and A/D = 0.1

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Fig. 24

Nondimensionalized turbulent kinetic energy diffusion for stationary and oscillating square cylinder at Re = 485 and A/D = 0.1

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Fig. 25

Percentage turbulence intensity (urms2 + vrms2)0.5/U for stationary and oscillating square cylinder at Re = 485 and A/D = 0.1

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Fig. 26

Time-averaged nondimensionalized Reynolds stress ( −u′v′) for stationary and oscillating cylinder at Re = 485 and A/D = 0.1

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Fig. 27

Instantaneous particle traces in x–y plane over stationary and oscillating square cylinder with fixed amplitude of oscillation (A/D = 0.1) at Re = 485

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Fig. 28

Time-averaged streamlines in the wake of a square cylinder with different amplitude ratios at fixed frequency ratio (f/f0 = 1)

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Fig. 29

Time-averaged nondimensionalized spanwise vorticity contours (ωz) in the wake of a square cylinder with different amplitude ratios at fixed frequency ratio (f/f0 = 1)

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Fig. 30

Percentage turbulence intensity (urms2 + vrms2)0.5/U in the wake of a square cylinder with different amplitude ratios at fixed frequency (f/f0 = 1)

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Fig. 31

Power spectra of v-velocity in the wake of an oscillating cylinder at different amplitude ratios, Re = 485 and f/f0 = 1

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Fig. 32

Instantaneous flow visualization images in x–y plane over a stationary and oscillating square cylinder at various amplitude ratios with fixed frequency (f/f0 = 1) and Re = 485

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