The drag reduction on commercial vehicles using front deflectors is studied using CFD for Tata Ace vehicle. The tools used are Fluent & Gambit.

1. AERODYNAMIC DRAG REDUCTION IN
COMMERCIAL VEHICLES (TATAACE)
USING FRONT DEFLECTOR
JJ TECHNICAL SOLUTIONS
(www.mechieprojects.com)

2. AIM
1. To study and understand the aerodynamic air flow over a TATAACE pickup truck
2. To calculate the aero-force acting on the vehicle for 10m/s velocity & compute the drag
coefficient
3. To study and compare the effect of different shape of front deflectors on drag coefficient
4. To design the aerodynamic shape deflector for the minimum coefficient of drag.

3. PROBLEM FORMULATION
Tools Used:
1. Drafting/Modeling: SolidWorks
2. Meshing: Gambit
3. Analysis & Post Processing: Fluent
Tata Ace
Velocity Inlet
Meshing of Model in Gambit & Defining Boundary Conditions
Pressure Outlet
Velocity Inlet
Wall
Types of Deflector Considered
Case 1. No Deflector
Case 2. Straight Deflector
Case 3. Convex Deflector
Case 4. Concave Deflector
L2L 6L

4. Problem Definition in FLUENT
Define the problem as,
Solver -Pressure based
Formulation -Implicit
Space -2D
Time -Steady
Viscous -Two-equation SST-k-omega model
Enable the Energy equation
The fluid type used is Air defined as ideal gas
Operating pressure= 0 Pa

5. LIFT, DRAG, AND MOMENT COEFFICIENTS
• Behavior of L, D, and M depend on a, but also on velocity and altitude
• V∞, r ∞, Wing Area (S), Wing Shape, m ∞, compressibility
• Characterize behavior of L, D, M with coefficients (cl, cd, cm)
 Re,,
2
1
2
1
3
2
2







Mfc
Scq
L
ScV
M
c
SccVM
m
m
m
a
r
r
 Re,,
2
1
2
1
2
2
2







Mfc
Sq
D
SV
D
c
ScVD
d
d
d
a
r
r
 Re,,
2
1
2
1
1
2
2







Mfc
Sq
L
SV
L
c
ScVL
l
l
l
a
r
r
Note on Notation:
We use lower case, cl, cd, and cm for infinite wings (airfoils)
We use upper case, CL, CD, and CM for finite wings

6. PRESSURE COEFFICIENT, CP
• Use non-dimensional description, instead of plotting actual values of
pressure
• Pressure distribution in aerodynamic literature often given as Cp
• So why do we care?
• Distribution of Cp leads to value of cl
• Easy to get pressure data in wind tunnels
• Shows effect of M∞ on cl
2
2
1



 



V
pp
q
pp
Cp
r

7. Structured Grid/Mesh created in Gambit
Types of Deflector Considered
Case 1. No Deflector
Case 2. Straight Deflector
Case 3. Convex Deflector
Case 4. Concave Deflector
Velocity Inlet
Pressure Outlet
Velocity Inlet
Wall

8. Solution Convergence in Fluent

9. Contours of Static Pressure around the Tata Ace at velocity = 10m/s
Case 1 : No Deflector

10. Contours of Dynamic Pressure around the Tata Ace at velocity = 10m/s
Case 1 : No Deflector

11. Contours of Velocity Magnitude around the Tata Ace at velocity = 10m/s
Case 1 : No Deflector

12. Contours of Velocity Magnitude around the Tata Ace at velocity = 10m/s
Case 1 : No Deflector

13. Contours of Velocity Magnitude around the Tata Ace at velocity = 10m/s
Case 1 : No Deflector

14. Velocity Magnitude Vectors around the Tata Ace at velocity = 10m/s
Case 1 : No Deflector

15. Pressure Coeff. Plot around the Tata Ace at velocity = 10m/s
Case 1 : No Deflector

16. Contours of Static Pressure around the Tata Ace at velocity = 10m/s
Case 2 : Straight Deflector

17. Contours of Velocity magnitude around the Tata Ace at velocity = 10m/s
Case 2 : Straight Deflector

18. Case 2 : Straight Deflector
Contours of Velocity magnitude around the Tata Ace at velocity = 10m/s

19. Case 2 : Straight Deflector
Plot of Pressure Coeff. around the Tata Ace at velocity = 10m/s

20. Case 3 : Convex Deflector
Contours of Velocity magnitude around the Tata Ace at velocity = 10m/s

21. Case 3 : Convex Deflector
Contours of Velocity magnitude around the Tata Ace at velocity = 10m/s

22. Case 3 : Convex Deflector
Plot of Pressure Coeff. around the Tata Ace at velocity = 10m/s

23. Case 4 : Concave Deflector
Contours of Static Pressure around the Tata Ace at velocity = 10m/s

24. Case 4 : Concave Deflector
Contours of Velocity magnitude around the Tata Ace at velocity = 10m/s

25. Case 4 : Concave Deflector
Contours of Velocity magnitude around the Tata Ace at velocity = 10m/s

26. Case 4 : Concave Deflector
Plot of Pressure Coeff. around the Tata Ace at velocity = 10m/s

27. Case 3
Case 2Case 1
Case 4

28. Pressure
Force (N)
Viscous
Force (N)
Total force
(N)
Pressure
Coeff.
Viscous
Coeff.
Total
Coeff. Lift Coeff.
Drag
Coeff.
Config. 1 210.4669 1.719078 212.1859 1.527197 0.012474 1.539671 -1.14E+00 1.54E+00
Config. 2 134.3915 3.477828 137.8693 0.975176 0.025236 1.000412 -4.64E-01 1.00E+00
Config. 3 116.5591 2.387426 118.9465 0.84578 0.017324 0.863104 -3.93E-01 8.63E-01
Config. 4 220.5458 1.832951 222.3787 1.600332 0.0133 1.613632 -4.88E-03 1.61E+00
Types of Deflector Considered
Case 1. No Deflector
Case 2. Straight Deflector
Case 3. Convex Deflector
Case 4. Concave Deflector

29. CONCLUSION
1. The contours of Velocity & Pressure is plotted, around the Tata Ace
for velocity of 10m/s
2. The velocity increases near the tip of the highest portion of the
vehicle at the point of sharp curvature changes
3. A swirl/ backflow is generated at the rear end of the car with
negative velocity.
4. The pressure coefficient is plotted for the top & bottom side of the
car.
5. The pressure force, viscous force and total force acting on the Tata
Ace vehicle is plotted for different deflector configurations
6. The Drag coefficient (Cd) is minimum for Convex deflector.
7. By using a front deflector the Cd reduces from 1.61 to 0.863.

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31. This is purely an academic work and has no financial or other
interest.
The results achieved in this should be independently verified.