Drag Reduction of a Passenger Car Using Flow Control Techniques

  • Akshoy Ranjan PaulEmail author
  • Anuj Jain
  • Firoz Alam


The paper describes flow control techniques viz. vane-type vortex generator (VG) array and rear-spoiler on its trunk (boot) side used to reduce drag of a passenger car. The experimental and computational studies were carried out and different cases and combinations were analyzed for the car model by varying incoming airflow angle and spoiler angle and orientations of VG array to find out the optimum conditions for which drag coefficient is found minimum. Shear stress transport (SST) k-w turbulence model is found suitable in predicting the multi-scale rear-wake vortices of the car geometry. It is found that the crossflow increases the drag coefficient, which can however be reduced effectively if both VG array and rear-spoiler are used. Parametric analysis shows that counter-rotating VG array is found useful in reducing drag (around 23 %) as it promotes better flow mixing at its downstream, which is helpful in avoiding flow separation. The finding is also supported by the flow visualization study. It is also found that saving up to 11.5 % in the fuel consumption can be achieved by reducing drag using these techniques. The wake analysis and turbulent kinetic energy plots indicated that the counterrotating VG array while used with a rear spoiler parallel to the flow reduced drag considerably.

Key words

Car aerodynamics Flow separation Vortex Generator (VG) Rear spoiler Drag coefficient Turbulent Kinetic Energy (TKE) 




drag coefficient (dimensionless)


centerline length of car (mm)


wall static pressure coefficient (dimensionless)


turbulence model constant


height of car model (mm)


turbulent kinetic energy (m2s−2)


length of car model (mm)


length of rear spoiler (mm)


static pressure (Nm−2)


reynolds number (dimensionless)


velocity (ms−1)


width of car model (mm)

x, y, z


Greek Letters


rear spoiler angle w.r.t. flow (degree)


car angle w.r.t. flow (degree)


turbulent kinetic energy dissipation rate (m2s−3)


kinematic viscosity coefficient (m2s−1)


specific dissipation (s−1)



vector indices


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Copyright information

© KSAE 2019

Authors and Affiliations

  1. 1.Department of Applied MechanicsMotilal Nehru National Institute of Technology AllahabadPrayagrajIndia
  2. 2.School of Aerospace, Mechanical and Manufacturing EngineeringRMIT UniversityMelbourneAustralia

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