Presented By: Pradeep Raja Muthunagalingam

AERODYNAMIC DRAG & LIFT REDUCTION FOR A PASSENGER CAR

R.I.T - Mechanical Engineering Tuesday, December 16, 2014

• Computational Fluid Dynamics (CFD) methodology to acquire the stream structure around a passenger car.

• Model of passenger car, Wind tunnel has been designed and applied the boundary conditions in ANSYS workbench 15.0.

• Air flow over passenger car with & without tail plates are simulated and their coefficients of drag & lift are studied

• Utilization of tail plates brings a reduction in drag by 4.98% and lift by 15.1%.

OVERVIEW

R.I.T - Mechanical Engineering Tuesday, December 16, 2014

• To demonstrate the reduction in aerodynamic drag for a passenger car utilizing tail plates

• To calculate drag & lift coefficient for passenger car with and without tail plates; compare the numerical results obtained from simulation with the empirical data.

• To plot the Drag coefficient, Lift Coefficient, Pressure contour and velocity vector contour for both cars and compare them.

AIM

R.I.T - Mechanical Engineering Tuesday, December 16, 2014

GEOMETRY

R.I.T - Mechanical Engineering Tuesday, December 16, 2014

Height = 1475mm; Width = 1490mm; Length = 3395mm; Tail plate = 12.

Length of tunnel = 50m; Height of tunnel = 4.5m; Width of tunnel = 9m

MATERIAL PROPERTIES

R.I.T - Mechanical Engineering Tuesday, December 16, 2014

Parameters ValuesFluid Type Air

Density 1.175

Viscosity 1.7894 *

BOUNDARY CONDITIONS

R.I.T - Mechanical Engineering Tuesday, December 16, 2014

Conditions Parameters Values

Velocity Inlet

Magnitude 22 m/s

Turbulence Specification Method Intensity and Viscosity Ratio

Turbulence Intensity 1.00%

Turbulence Viscosity Ratio 5

Pressure Outlet

Gauge Pressure magnitude 0 pa

Gauge Pressure direction normal to boundary

Turbulence Specification Method Intensity and Viscosity Ratio

Backflow Turbulence Intensity 5%

Backflow Turbulent Viscosity Ratio

10

Wall Zones

vehicle surface-no slip wall B/cGround face- invicisd wall B/CSide faces -inviscid wall B/C

MESH – CAR WITHOUT TAIL PLATE

R.I.T - Mechanical Engineering Tuesday, December 16, 2014

Quality – Coarse at wall , Refined near car surfaceTechniques – Face sizing, InflationGrid density – 338243 cells

MESH – CAR WITH TAIL PLATE

R.I.T - Mechanical Engineering Tuesday, December 16, 2014

Quality – Coarse at wall , Refined near car surfaceTechniques – Face sizing, InflationGrid density – 469703 cells

SOLVER SETTINGS

R.I.T - Mechanical Engineering Tuesday, December 16, 2014

  Solution method Spatial Discretization values

Solver 1 SIMPLE

Gradient Least Squares Cell BasedPressure Second orderMomentum First order upwindTurbulent Kinetic energy First order upwindTurbulent Dissipation rate First order upwind

Solver 2 SIMPLE

Gradient Least Squares Cell BasedPressure Second orderMomentum Second order upwindTurbulent Kinetic energy Second order upwindTurbulent Dissipation rate Second order upwind

Solver 3 SIMPLEC

Gradient Least Squares Cell BasedPressure Second orderMomentum Second order upwindTurbulent Kinetic energy Second order upwindTurbulent Dissipation rate Second order upwind

Solver 4 Coupled

Gradient Least Squares Cell BasedPressure Second orderMomentum Second order upwindTurbulent Kinetic energy Second order upwindTurbulent Dissipation rate Second order upwind

CONVERGENCE

R.I.T - Mechanical Engineering Tuesday, December 16, 2014

Model = K-epsilonCriteria = Status – AchievedMass flow Rate - Equal

RESULTS – OPTIMUM SOLVER

R.I.T - Mechanical Engineering Tuesday, December 16, 2014

0.351

0.41

0.381

0.395 0.391

Drag CoefficientEmpirical Solver 1 Solver 2 Solver 3Solver 4

Solvers

0.231

0.196

0.211 0.208

0.217

Lift Coefficient

Empirical Solver 1 Solver 2 Solver 3 Solver 4

Solvers

RESULTS – DRAG COEFFICIENT

R.I.T - Mechanical Engineering Tuesday, December 16, 2014

Car without tail plate = 0.381 Car with tail plate = 0.362

RESULTS – LIFT COEFFICIENT

R.I.T - Mechanical Engineering Tuesday, December 16, 2014

Car without tail plate = 0.211 Car with tail plate = 0.179

RESULTS – PRESSURE CONTOUR

R.I.T - Mechanical Engineering Tuesday, December 16, 2014

Car without tail plate Car with tail plate

RESULTS – VELOCITY VECTOR

R.I.T - Mechanical Engineering Tuesday, December 16, 2014

Car without tail plate Car with tail plate

RESULTS – DRAG & LIFT REDUCTION

R.I.T - Mechanical Engineering Tuesday, December 16, 2014

1 20.31

0.32

0.33

0.34

0.35

0.36

0.37

0.38

0.39

0.351

0.337

0.381

0.362

Reduction in Drag Coeffi cient

Empirical Simulation

Dra

g Co

effici

ent

1 20.1

0.12

0.14

0.16

0.18

0.2

0.22

0.24 0.231

0.1920.211

0.179

Reduction in Lift Coeffi cient

Empirical Simulation

Lift

Coe

ffici

ent

RESULTS – % REDUCTION OF DRAG & LIFT

R.I.T - Mechanical Engineering Tuesday, December 16, 2014

  Drag Coefficient Cd Lift Coefficient Cl

Empirical Simulation Empirical Simulation

Car Without Tail Plate

0.351 0.381 0.231 0.211

Car With Tail Plate

0.337 0.362 0.192 0.179

% of Reduction

3.87% 4.98% 16.6% 15.1%

• Coefficient of drag has been reduced by 4.98% and coefficient of lift is reduced by 15.1%.

• Tail Plate is the one of the effective tools to reduce the drag force on vehicle.

• Drag force can be reduced by using add on devices on vehicle and fuel economy, stability of a passenger car can be improved

CONCLUSION

R.I.T - Mechanical Engineering Tuesday, December 16, 2014