CFD Online Logo CFD Online URL
Home > Forums > Software User Forums > ANSYS > FLUENT

Analysis of 2D Car Drag coefficient and Lift coefficient

Register Blogs Members List Search Today's Posts Mark Forums Read

Like Tree1Likes
  • 1 Post By LuckyTran

LinkBack Thread Tools Search this Thread Display Modes
Old   August 9, 2018, 00:15
Default Analysis of 2D Car Drag coefficient and Lift coefficient
New Member
Join Date: Aug 2018
Posts: 2
Rep Power: 0
Chao is on a distinguished road
I'm a beginner in the field. Now I am confused about some settings.
I'm doing a analysis job to compare the difference between a car with rear wing and the other one without rear wing.

First, I don't sure which car (the one with rear wing or the one without rear wing)should have a bigger Cd value, somebody says that cars with rear wings will increase drag as well as downforce, is that right ?

Second, I always get Cl values about, but the values seem to be too large. As I google some similar papers to check the results, their Cl values are about -0.2xxx.

So, plz help me to check if there are any mistakes settings that need to be corrected.Thanks!

There are my settings below: (I change these settings only, the others are default)

-I use 1:1 2D cars, created by SpaceClaim. I set up the cars with 4875mm 1780mm 1435mm, So should I change the unit in Ansys Workbench into mm ?

-viscous model: k-e

-inlet 30 m/s (velocity inlet)

-reference values:
Area : 2.09 m^2 (frontal area of the car)
Depth:1.58 m (car width)
length:1.78 m (car length)
velocity:30 m/s (should I give the velocity again here? I have given velocity inlet 30 m/s already)

after these I run 500 iterations
Chao is offline   Reply With Quote

Old   August 10, 2018, 13:10
Senior Member
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 5,112
Rep Power: 60
LuckyTran has a spectacular aura aboutLuckyTran has a spectacular aura aboutLuckyTran has a spectacular aura about
Check that your model is 4875mm and not 4875m.

The reference values are needed to calculate the coefficients. Yes you need to put a reference velocity. The inlet velocity is the inlet velocity as a boundary condition. You still need a reference velocity, which can be different than the inlet velocity (more obvious if you have more than 1 inlet).

Check that the reference values you supplied are consistent with the definition of drag coefficient. In 2D you have another problem to worry about. Make sure the reference area and reference depth are consistent. In 3D, the reference area is the frontal area, but in 2D there is no more a frontal area only the (height of the car front). Using the actual frontal area of the the 3D car in 2D might be incorrect because Fluent takes the pressure load on the "2D front of the car" and multiplies it by the reference depth to get the force and then normalizes it by the reference area. A lot of people set the reference depth to 1m so that all their results are per meter basis (i.e. force / meter depth) rather than using the width of the car.
Chao likes this.
LuckyTran is offline   Reply With Quote

Old   August 11, 2018, 03:30
New Member
Join Date: Aug 2018
Posts: 2
Rep Power: 0
Chao is on a distinguished road
thanks for reply~ I'll try that again)
Chao is offline   Reply With Quote


2d car fluent

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Calculation of lift and drag coefficients on airfoil CoolHersheys OpenFOAM Post-Processing 5 September 27, 2021 07:04
wrong SU2 calculation for lift and drag coefficient for NAC4421 mechy SU2 7 January 9, 2017 06:18
Drag and Lift coefficient for diffusor rego STAR-CCM+ 3 May 7, 2012 19:05
Automotive test case vinz OpenFOAM Running, Solving & CFD 98 October 27, 2008 09:43

All times are GMT -4. The time now is 19:41.