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Research Papers: Flows in Complex Systems

Optimizing Jets for Active Control of Wake Refinement for Ground Vehicles

[+] Author and Article Information
Domenic L. Barsotti, Eduardo A. Divo

Department of Mechanical Engineering,
Embry-Riddle Aeronautical University,
Daytona Beach, FL 32114

Sandra K. S. Boetcher

Department of Mechanical Engineering,
Embry-Riddle Aeronautical University,
Daytona Beach, FL 32114
e-mail: sandra.boetcher@erau.edu

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received July 2, 2014; final manuscript received June 9, 2015; published online August 6, 2015. Assoc. Editor: Feng Liu.

J. Fluids Eng 137(12), 121108 (Aug 06, 2015) (10 pages) Paper No: FE-14-1349; doi: 10.1115/1.4030913 History: Received July 02, 2014

The present study investigates active drag reduction of an Ahmed body with a rear slant angle of 25 deg. The drag is reduced by implementing slot jets on the rear slant and rear surface of the Ahmed body. Transient numerical experiments were conducted using the improved delayed detached eddy simulation (IDDES) turbulence model. Jet velocity, position, size, and angle were parametrically varied, and time-averaged drag coefficients for various jet configurations were calculated. Reynolds numbers based on the length of the Ahmed body were varied, but special focus was given to the high-drag case when Re = 1.4 × 106. It was found that by using slot jets at the rear and rear slant, the drag coefficient was reduced by 22%. In order to investigate the physical mechanisms for the reduction in drag, proper orthogonal decomposition (POD) was used to visualize the turbulent coherent structures in the near wake of the Ahmed body.

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References

Figures

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Fig. 1

Ahmed body with 25 deg rear slant, all dimensions in millimeter

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Fig. 2

Flow structures of the Ahmed body from the study of Vino et al. [3]: (1)—flow separation on rear slant, (2)—large vortex structure, and (3)—conical streamwise vortices

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Fig. 3

Slot jet location on rear face of Ahmed body, dimensions in millimeter

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Fig. 4

Point distribution in Ahmed body wake for POD sampling

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Fig. 5

Comparison of current results with experimental data

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Fig. 6

Schematic of jet configurations on the rear of the Ahmed body: (a) top and bottom (φ = 0 deg) and (b) top and bottom (φ = 25 deg)

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Fig. 7

Drag coefficient versus jet velocity for φ=0 deg

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Fig. 8

Drag coefficient versus jet velocity for φ=25 deg

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Fig. 9

Slot jet location on rear slant of the Ahmed body, dimensions in millimeter

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Fig. 10

Schematic of jet configurations for Ahmed body with a rear slant jet: (a) slant, top, and bottom (b) slant and bottom and (c) slant

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Fig. 11

Eigenvalue λ versus mode

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Fig. 12

Fraction of the total turbulent kinetic energy versus mode

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Fig. 13

Isosurfaces of the first POD mode of the u velocity for the no jets case

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Fig. 14

Isosurfaces of the first POD mode of the u velocity for the rear jets case

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Fig. 15

Isosurfaces of the first POD mode of the u velocity for the rear slant jet case

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Fig. 16

Vortex drag coefficient as a function of dimensionless distance behind the Ahmed body

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Fig. 17

Streamlines behind the Ahmed body shaded by (v2+w2)2 in units of m2/s2 for (a) no jets, (b) rear jets, and (c) rear slant jet

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Fig. 18

Contours of planes behind the Ahmed body parallel to the rear face at distances of 150 mm from the rear and 500 mm from the rear shaded by (v2+w2)2 in units of m2/s2 for no jets: (a) 150 mm and (d) 500 mm; rear jets: (b) 150 mm and (e) 500 mm; and rear slant jet: (c) 150 mm and (f) 500 mm

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