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Research Papers: Flows in Complex Systems

Characterization of Tab-Induced Counter-Rotating Vortex Pair for Mixing Applications

[+] Author and Article Information
Jeongmoon Park

Department of Mechanical Engineering,
Texas A&M University,
College Station, TX 77843
e-mail: park469@tamu.edu

Axy Pagan-Vazquez

U.S. Army Construction Engineering
Research Laboratory (CERL),
Champaign, IL 61826;
Department of Mechanical Engineering,
University of Illinois Urbana-Champaign,
Urbana, IL 61801
e-mail: Axy.Pagan-Vazquez@usace.army.mil;
paganva2@illinois.edu

Jorge L. Alvarado

Mem. ASME
Department of Engineering Technology and
Industrial Distribution,
Texas A&M University,
College Station, TX 77843
e-mail: jorge.alvarado@tamu.edu

Leonardo P. Chamorro

Department of Mechanical Engineering,
University of Illinois Urbana-Champaign,
Urbana, IL 61801
e-mail: lpchamo@illinois.edu

Scott M. Lux

U.S. Army Construction Engineering
Research Laboratory (CERL),
Champaign, IL 61826
e-mail: Scott.M.Lux@usace.army.mil

Charles P. Marsh

U.S. Army Construction Engineering
Research Laboratory (CERL),
Champaign, IL 61826
e-mail: Charles.P.Marsh@usace.army.mil

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received February 8, 2016; final manuscript received August 20, 2016; published online December 7, 2016. Editor: Malcolm J. Andrews.This work is in part a work of the U.S. Government. ASME disclaims all interest in the U.S. Government's contributions.

J. Fluids Eng 139(3), 031102 (Dec 07, 2016) (12 pages) Paper No: FE-16-1088; doi: 10.1115/1.4034864 History: Received February 08, 2016; Revised August 20, 2016

An experimental and numerical investigation was carried out to explore the effects of four vortex generators (VG) on the onset of flow instabilities, the paths and characteristics of the induced coherent counter-rotating vortices at a Reynolds number Re ≈ 2000. The flow field around the VG was characterized using a smoke visualization technique and simulated numerically using Reynolds-averaged Navier-Stokes (RANS). The taper angle of the VG was varied based on the used tab geometries, including triangular, trapezoidal, and rectangular tabs, which shared the same height, inclination angle, and base width. The results reveal that each VG was able to generate a counter-rotating vortex pair (CVP), and that the taper angle has direct effects on the path of the CVP, the onset location of Kelvin–Helmholtz (K-H) instabilities, and the circulation strength of the vortex structures. Furthermore, a linear relation between VG taper angle and the onset of instability was observed experimentally. Before the onset of K–H instability, the path of the CVP in the wake of a VG can be predicted using a pseudo-viscous model, which was validated numerically and experimentally.

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References

Figures

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Fig. 1

CVP generator and basic variables: (a) isometric view, (b) side view, (c) top view, and (d) width at 50% chord (w)

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Fig. 2

(a) Schematic of the experimental setup, (b) photograph of the vortex generator in the test section, and (c) smoke visualization images

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Fig. 3

Instantaneous CVP images by smoke visualization at x/h of 1 and Re = 1965 (a) VG-A (ϕ = 0 deg), (b) VG-B (ϕ = 7.6 deg), (c) VG-C (ϕ = 13.5 deg), and (d) VG-D (ϕ = 19.3 deg), (e) CVP vertical core distance, a, and (f) CVP horizontal separation distance, b

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Fig. 4

(a) Visualization of Kelvin–Helmholtz instability in the wake of a VG at Re = 1965 and (b) determination of the location ofthe onset of Kelvin–Helmholtz instability by overlaying 15 consecutive images

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Fig. 5

Conceptual description of (a) rows of CVP and (b) single CVP on a flat wall. The dashed lines indicate periodic boundary condition.

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Fig. 6

(a) Numerical simulation domain∼330, ∼100, and ∼100 nodes in x, y, and z directions and (b) Cartesian-based structured and uniform mesh used in the simulations

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Fig. 7

Centerline velocity profiles for various grid sizes at x/h = 1.5 for VG-B case

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Fig. 8

Streamwise location of the onset of K–H instability for different taper angles of trapezoidal VGs

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Fig. 9

Centerline velocity profiles (a) VG-A (ϕ = 0 deg), (b) VG-B (ϕ = 7.6 deg), (c) VG-C (ϕ = 13.5 deg), and (d) VG-D (ϕ = 19.3 deg)

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Fig. 10

Vortex paths on the y–z plane for single CVP (Eq. (7)) and rows of CVP (Eq. (4)) for VG-A (ϕ = 0 deg)

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Fig. 11

Projection of the vortex path on the y–z plane: (a) VG-A (ϕ = 0 deg), (b) VG-B (ϕ = 7.6 deg), (c) VG-C (ϕ = 13.5 deg), and (d) VG-D (ϕ = 19.3 deg)

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Fig. 12

Vortex path on the x–y plane: (a) VG-A (ϕ = 0 deg), (b) VG-B (ϕ = 7.6 deg), (c) VG-C (ϕ = 13.5 deg), and (d) VG-D (ϕ = 19.3 deg)

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Fig. 13

Vortex path on the x–z plane: (a) VG-A (ϕ = 0 deg), (b) VG-B (ϕ = 7.6 deg), (c) VG-C (ϕ = 13.5 deg), and (d) VG-D (ϕ = 19.3 deg)

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Fig. 14

Vortex path on the x–y plane: (a) VG-R1 (AR = 0.86), (b) VG-R2 (AR = 0.78), (c) VG-R3 (AR = 0.7), (d) VG-R4 (AR = 0.44), and (e) VG-R5 (AR = 0.22)

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Fig. 15

Vortex path on the x–z plane: (a) VG-R1 (AR = 0.86), (b) VG-R2 (AR = 0.78), (c) VG-R3 (AR = 0.7), (d) VG-R4 (AR = 0.44), and (e) VG-R5 (AR = 0.22)

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Fig. 16

Circulation (Γ) at x/h = 1.2

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Fig. 17

Decay of circulation along the downstream: (a) VG-A (ϕ = 0 deg), (b) VG-B (ϕ = 7.6 deg), (c) VG-C (ϕ = 13.5 deg), and (d) VG-D (ϕ = 19.3 deg)

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Fig. 18

Decay of circulation along the downstream: (a) VG-R1 (AR = 0.86), (b) VG-R2 (AR = 0.78), (c) VG-R3 (AR = 0.7), (d) VG-R4 (AR = 0.44), and (e) VG-R5 (AR = 0.22)

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