Numerical Investigation of Aerodynamic Braking for a Ground Vehicle

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Abstract

The purpose of this article is to observe the effect of an air brake on the aerodynamics of a ground vehicle and also to study the influence of change in the parameters like the velocity of the vehicle, the angle of inclination, height, and position of the air brake on the aerodynamics of the vehicle body. The test subject used is an Ahmed body which is a generic 3D car body as it retains all the aerodynamic characteristics of a ground vehicle. Numerical investigation has been carried out by RNG k-ε turbulence model. Results are presented in terms of streamlines and drag coefficient to understand the influence of pertinent parameters on flow physics. It is found that with the use of an air brake, though the drag coefficient remains more or less constant with velocity, it increases with the increase in height and angle of inclination of the air brake. But the effect of position of air brake on the coefficient of drag is surprising since for certain heights of the air brake the drag coefficient is maximum at the foremost point and as the air brake moves towards the rear it is first observed to decrease and then increase. It is also observed that with the increase in height of the air brake the drag coefficient monotonically decreases as the position of the air brake is moved towards the rear. Taguchi method has been employed with L16 orthogonal array to obtain the optimal configuration for the air brake. For each of the selected parameters, four different levels have been chosen to obtain the maximum drag coefficient value. The study could provide an invaluable database for the optimal design of an airbrake for a ground vehicle.

Keywords

Aerodynamics Computational fluid dynamics Aerodynamic brake Ahmed body Ground vehicle Optimization Taguchi method 

Abbreviations

ABS

Anti-lock braking system

BL

Boundary layer

RNG

Re-normalization group

Notations

Adj MS

Adjusted mean squares

Adj SS

Adjusted sums of squares

CD

Drag coefficient

C, C, Cµ, σε, σk

RNG k-ε model parameters

DF

Total degrees of freedom

F

F-value

G

Gravity, 9.81 m/s2

H

Height of the air brake, cm

K

Turbulent kinetic energy per unit mass, m2/s2

L

Length of the car, m

P

Pressure, N/m2

p

p value

Re

Reynolds number

Seq SS

Sequential sums of squares

Sij

Mean strain rate tensor

U

Velocity, m/s

V

Velocity of the vehicle, m/s

X

Length of the air brake from the defined origin, cm

Greek letters

ρ

Density, kg/m3

µ

Viscosity, N-s/m2

ε

Dissipation rate of turbulent kinetic energy per unit mass, m2/s2

θ

Angle of Inclination of the air brake, degree

σεk

Constants in RNG k-ε model

η

Ratio of turbulence to mean shear time scale

ηo

RNG k-ε model parameter

Subscripts

Eff

Effective

i, j, k

Spatial coordinates

t

Turbulent

Notes

Acknowledgements

The author is thankful NIT Warangal for assistance in performing simulations.

References

  1. 1.
    P. Ken, Automobile Braking Systems, 6th edn. (Cengage Learning, Boston, 2014)Google Scholar
  2. 2.
    W. Jonathan, N. Andrew, D.S. Philip, The Ultimate History of Fast Cars: Vehicles Built for the Fast Lane (Parragon Publishing India, Noida, 2011)Google Scholar
  3. 3.
    J. Katz, Race Car Aerodynamics: Designing for Speed (Robert Bentley Publishers, Cambridge, 1996)Google Scholar
  4. 4.
    S. Carroll, Tune to Win (Aero Publishers, Fall Brook, 1978)Google Scholar
  5. 5.
    L. Trevor, D.S.C. Philip, The Ultimate History of Mercedes-Benz (Parragon Pubishing India, Noida, 2010)Google Scholar
  6. 6.
    The Car that Loves to Hold the Road, Popular science magazine. Bon. Corp. 268(2), 22 (2006)Google Scholar
  7. 7.
    S.R. Ahmed, G. Ramm, G. Faltin, Some salient features of the time-averaged ground vehicle wake. SAE Technical Paper 840300 (1984). doi: 10.4271/840300
  8. 8.
    J.D. Anderson-Jr, Fundamentals of Aerodynamics, 5th edn. (McGraw Hill, New York, 2014)Google Scholar
  9. 9.
    G. Emmanuel, Computational study of flow around a simplified car body. J Wind Eng. Ind. Aerod. 96(6–7), 1207–1217 (2008)Google Scholar
  10. 10.
    C.H. Bruneau, C. Emmanuel, D. Delphine, G. Patrick, M. Iraj, Coupling active and passive techniques to control the flow past the square back Ahmed body. Comp. Fluids 39(10), 1875–1892 (2010)CrossRefMATHGoogle Scholar
  11. 11.
    F.H. Hsu, R.L. Davis, New drag reduction design for tractor-trailers using CFD. Int. J. Aerod. 1(2), 192–205 (2010)CrossRefGoogle Scholar
  12. 12.
    G. Pujals, S. Depardon, C. Cossu, Drag reduction of a 3D bluff body using coherent streamwise streaks. Exp. Fluids 49(5), 1085–1094 (2010)CrossRefGoogle Scholar
  13. 13.
    S.K. Das, P. Kumar, S. Rawat, Alterations of formula 3 race car diffuser geometry for optimized downforce. Int. J. Eng. Res. Tech. 6(3), 351–358 (2013)Google Scholar
  14. 14.
    S. Mukherjee, A. Kamal, K. Kumar, Optimization of material removal rate during turning of SAE 1020 material in CNC lathe using Taguchi technique. Procedia Eng. 97, 29–35 (2014)CrossRefGoogle Scholar
  15. 15.
    W. Follett, A. Ketchum, A. Darian, Y. Hus, Application of optimization techniques to design of unconventional rocket nozzle configurations, 13th Workshop for CFD Applications in Rocket Propulsion Huntsville, Alabama, 1995, pp. 879–888Google Scholar
  16. 16.
    P. Juan Murcia, A. Pinilla, CFD analysis of blunt trailing edge airfoils obtained with several modification methods. Revista de Ingeniería. 33, 14–24 (2011)Google Scholar
  17. 17.
    A. Jafari, T. Tynjala, S.M. Mousavi, P. Sarkomaa, CFD Simulation and evaluation of controllable parameters effect on thermomagnetic convection in ferro-fluids using Taguchi technique. J. Comp. Fluids. 37, 1344–1353 (2008)CrossRefMATHGoogle Scholar
  18. 18.
    D.J. Krishna, R.R. Deshpande, Taguchi based methodology to generate correlation via numerical analysis for natural convection in a differentially heated cavity—HMTC1300663, in Proceedings of the 22nd National and 11th International ISHMT-ASME Heat and Mass Transfer Conference (IIT Kharagpur, India, 2013)Google Scholar
  19. 19.
    N. Ozalp, D. Jaya Krishna, CFD Analysis on the influence of helical carving in a vortex flow solar reactor. Int. J. Hydrog. Energy 35(12), 6248–6260 (2010)CrossRefGoogle Scholar
  20. 20.
    D. Jaya Krishna, N. Ozalp, Response to the comments made by Khalid M. Saqr on our paper titled-CFD analysis on the influence of helical carving in a vortex flow solar reactor. Int. J. Hydrog. Energy 36(3), 2323–2326 (2011)CrossRefGoogle Scholar
  21. 21.
    I. Bayraktar, D. Landman, O. Baysal, Experimental and computational investigation of Ahmed body for ground vehicle aerodynamics. SAE Technical Paper 2001-01-2742 (2001). doi: 10.4271/2001-01-2742
  22. 22.
    R.N. Jazar, Vehicle Dynamics: Theory and Application (Springer, New York, 2008)CrossRefGoogle Scholar

Copyright information

© The Institution of Engineers (India) 2017

Authors and Affiliations

  1. 1.Department of Mechanical EngineeringNational Institute of Technology WarangalWarangalIndia

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