# DRAG

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 March 19, 2008, 16:23 DRAG #1 Diego Flores Guest   Posts: n/a How I can measure the DRAG in any model of Fluent?? For instance a 3d Car model or in 3d wing

 March 19, 2008, 20:53 Re: DRAG #2 Jonathan Vogt Guest   Posts: n/a From the menu: Report -> Forces... select all the surfaces of the car or wing (whatever you want to find the drag on) and select the vector direction of the drag force. So, if x points forward (where the car is going) then for drag you'd set the vector direction to: x = -1 y = 0 z = 0 and the result is you get the component of the total force acting on the surfaces you selected - in the rear pointing direction - which is drag!

 March 21, 2008, 13:32 Re: DRAG #3 red lemon Guest   Posts: n/a remember to set reference area in CD/CL calc and switch to correct reference velocity also

 August 29, 2009, 19:06 Drag On 3D Truck #4 New Member   Mrt Join Date: Mar 2009 Posts: 21 Rep Power: 9 I calculated drag force and coefficient in the same way that you have mentioned but I obtained 0.313 for 3D truck geometry. In literature, drag coef. value for truck is between 0.6-0.9. Furtherome, 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. Also, what is CD/CL calc.for reference are that you mentioned in the last message? Thanks, Murat

April 17, 2011, 07:48
#5
Member

Aamer Shahzad
Join Date: Mar 2010
Posts: 58
Rep Power: 8
Quote:
 Originally Posted by Jonathan Vogt ;149324 From the menu: Report -> Forces... select all the surfaces of the car or wing (whatever you want to find the drag on) and select the vector direction of the drag force. So, if x points forward (where the car is going) then for drag you'd set the vector direction to: x = -1 y = 0 z = 0 and the result is you get the component of the total force acting on the surfaces you selected - in the rear pointing direction - which is drag!
Dear Jonathan Vogt

its perfect to use X=-1, Y=0 and Z=0, to find drag on a car that is translating in positive X direction..... But how can we calculate drag for a car that is rotating about Y -axis...... (i.e initially it is aligned to +X axis and then during rotation it get aligned to +Z axis after rotating 90 degree and then it again gets realigned to +X axis after travelling another 90 degree...

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