Fluent 6.2-Drag coefficients on 3D Truck

MDinc · August 29, 2009, 19:20

Hi to all,

I calculated drag force and coefficient on Fluent 6.2 but I obtained 0.313 for 3D truck geometry. In literature, drag coef. value for truck is between 0.6-0.9. Furthermore, what is wrong with my calculations? I set the ref. values 20 m/s for velocity and 7.2 m2 for frontal area of truck.
(RSM Turbulence Model, has about 5 million element, has additional parts on truck like plow in front and airfoil, side vanes... in the rear corner of truck.)

Thanks,
Murat

poiu · August 30, 2009, 04:29

where did you set the calculation of the drag force?
you use your own formula?

MDinc · August 31, 2009, 13:04

I gave the reference values on Fluent (Report-Refererance Values...). Then I selected 'Report forces-X (Vector)-All Truck Surfaces' . Lastly, Fluent calculated all coefficients and forces (pressure, viscous, total...). However, CFD results and literature results does not match. Is error on reference values?

Murat

Chris D · September 1, 2009, 13:36

Are you using the same reference values as your source?

MDinc · September 1, 2009, 19:26

Yes, velocity same and frontal are same.

Chris D · September 1, 2009, 22:17

What did you mean in your original post when you said, "has additional parts on truck like plow in front and airfoil, side vanes..."? Do you mean that your model had a plow, airfoil, etc., but the model you're using for comparison does not? If you're trying to match your results to someone else's results, I think you would need to model the same geometry. Maybe I'm just not understanding what the problem is, though.

MDinc · September 2, 2009, 03:25

It is not important, I mean the additional parts. What I try to say is drag coefficient for a kind of big truck found like 0.313 even small cars do not have such a low drag coefficient. Thus, I am trying to figure out where the mistake is, in reference values ( Velocity, frontal area...) or in solution.

Thanks,
Murat

poiu · September 29, 2009, 08:41

Quote:

Originally Posted by MDinc

Hi to all,

I calculated drag force and coefficient on Fluent 6.2 but I obtained 0.313 for 3D truck geometry. In literature, drag coef. value for truck is between 0.6-0.9. Furthermore, what is wrong with my calculations? I set the ref. values 20 m/s for velocity and 7.2 m2 for frontal area of truck.
(RSM Turbulence Model, has about 5 million element, has additional parts on truck like plow in front and airfoil, side vanes... in the rear corner of truck.)

Thanks,
Murat

hi:
does your question resolved?
which one do you think is the drag force?
the total force?

August 29, 2009, 19:20	Fluent 6.2-Drag coefficients on 3D Truck	#1
MDinc New Member Mrt Join Date: Mar 2009 Posts: 21 Rep Power: 17	Hi to all, I calculated drag force and coefficient on Fluent 6.2 but I obtained 0.313 for 3D truck geometry. In literature, drag coef. value for truck is between 0.6-0.9. Furthermore, what is wrong with my calculations? I set the ref. values 20 m/s for velocity and 7.2 m2 for frontal area of truck. (RSM Turbulence Model, has about 5 million element, has additional parts on truck like plow in front and airfoil, side vanes... in the rear corner of truck.) Thanks, Murat

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August 30, 2009, 04:29		#2
poiu New Member Join Date: Mar 2009 Posts: 18 Rep Power: 17	where did you set the calculation of the drag force? you use your own formula?

August 31, 2009, 13:04		#3
MDinc New Member Mrt Join Date: Mar 2009 Posts: 21 Rep Power: 17	I gave the reference values on Fluent (Report-Refererance Values...). Then I selected 'Report forces-X (Vector)-All Truck Surfaces' . Lastly, Fluent calculated all coefficients and forces (pressure, viscous, total...). However, CFD results and literature results does not match. Is error on reference values? Murat

September 1, 2009, 13:36		#4
Chris D Senior Member Chris Join Date: Jul 2009 Location: Ohio, USA Posts: 169 Rep Power: 16	Are you using the same reference values as your source?

September 1, 2009, 19:26		#5
MDinc New Member Mrt Join Date: Mar 2009 Posts: 21 Rep Power: 17	Yes, velocity same and frontal are same.

September 1, 2009, 22:17		#6
Chris D Senior Member Chris Join Date: Jul 2009 Location: Ohio, USA Posts: 169 Rep Power: 16	What did you mean in your original post when you said, "has additional parts on truck like plow in front and airfoil, side vanes..."? Do you mean that your model had a plow, airfoil, etc., but the model you're using for comparison does not? If you're trying to match your results to someone else's results, I think you would need to model the same geometry. Maybe I'm just not understanding what the problem is, though.

September 2, 2009, 03:25		#7
MDinc New Member Mrt Join Date: Mar 2009 Posts: 21 Rep Power: 17	It is not important, I mean the additional parts. What I try to say is drag coefficient for a kind of big truck found like 0.313 even small cars do not have such a low drag coefficient. Thus, I am trying to figure out where the mistake is, in reference values ( Velocity, frontal area...) or in solution. Thanks, Murat