# How to find lift coefficient by fluent?

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February 4, 2011, 07:52
#21
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Maxime Perelli
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Quote:
 Originally Posted by John222 Sorry but when you say different mesh faces do you mean the Sizing (maximum face size) I am using (car.x_t) geomtry file from Ansys. and in the max face size by default its 1.78m. can someone tell me the full steps of how to change mesh faces 10.000-20.000-30.000.
If I take your mesh picture, I assume you meshed it with tri.
Then you gave a element size, let say 1 for example.
You can refine your mesh by changing the value of element size (0.5 instead of 1).
Then remesh, export, etc...
I see you have local refinement in your mesh. If you used size functions, then you need to change the max size in each size function, instead of the value in the surface-mesh panel
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February 4, 2011, 08:22
#22
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John
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Quote:
 Originally Posted by -mAx- If I take your mesh picture, I assume you meshed it with tri. Then you gave a element size, let say 1 for example. You can refine your mesh by changing the value of element size (0.5 instead of 1). Then remesh, export, etc... I see you have local refinement in your mesh. If you used size functions, then you need to change the max size in each size function, instead of the value in the surface-mesh panel

Please check the pictures of my coarse tri results. and the mesh too.
what do you think?
Attached Images
 drag.jpg (94.1 KB, 80 views) lift.jpg (93.7 KB, 78 views) untitled.jpg (95.7 KB, 71 views) mesh.jpg (95.8 KB, 88 views)

 February 4, 2011, 08:47 #23 Super Moderator     Maxime Perelli Join Date: Mar 2009 Location: Switzerland Posts: 3,232 Rep Power: 34 oh you are working with workbench... So forget what I said previously (I thought you were working with Gambit) I cannot help you on the meshing side since I only have Gambit. But if you are interested by aero Coeff, I would apply Boundary Layer around your car (especially if your flow is turbulent >>Check lectures about first cell layer height & y+) Also I wouldn't iterate with just 100 iterations: you can see that your Cl is still falling __________________ In memory of my friend Hervé: CFD engineer & freerider

February 4, 2011, 11:10
#24
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John
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Quote:
 Originally Posted by -mAx- oh you are working with workbench... So forget what I said previously (I thought you were working with Gambit) I cannot help you on the meshing side since I only have Gambit. But if you are interested by aero Coeff, I would apply Boundary Layer around your car (especially if your flow is turbulent >>Check lectures about first cell layer height & y+) Also I wouldn't iterate with just 100 iterations: you can see that your Cl is still falling
Please see my problematic issue with my mesh I changed it from coarse to medium and had errors:-

- The following surfaces cannot be meshed with acceptable quality. Try using a different element size or virtual topology.

- A mesh could not be generated using the current meshing options and settings. Hint: The problem geometry areas might have been highlighted. Switching to wireframe mode may make them more visible.

What can I do to fix this issue?
Attached Images
 problematic.jpg (88.8 KB, 73 views)

 February 7, 2011, 02:14 #25 Super Moderator     Maxime Perelli Join Date: Mar 2009 Location: Switzerland Posts: 3,232 Rep Power: 34 As I said, I don't have experience with Workbench __________________ In memory of my friend Hervé: CFD engineer & freerider

February 20, 2012, 12:39
#26
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Quote:
 Originally Posted by -mAx- enter 1 0 0 for Force Projection on x-axis enter 0 1 0 for Force Projection on y-axis enter 0 0 1 for Force Projection on z-axis Now choose the right force you want to observe, and enable the plot option in monitor/force Fluent will plot the accorded Coeff while iterating. Your solution will be full converged if the the plotted coefficient remains constant while iterating. You also have to set the right reference values for getting the right Coefficient
Hello max

I have a problem with Ansys Fluent too. I am wondering is there any recomended link to test aerodynamic on automotive such as truck or car. My drag and lift coefficient is not the same as I found in those journals.

Is there any improtant things i should beware when doing simulation on a scaled model? Some journal stated that the Reynolds number of model and real scale must be the same, is that so?

 February 21, 2012, 06:50 #27 Super Moderator     Maxime Perelli Join Date: Mar 2009 Location: Switzerland Posts: 3,232 Rep Power: 34 for coefficients, you have to set reference parameters http://my.fit.edu/itresources/manual...ug/node972.htm __________________ In memory of my friend Hervé: CFD engineer & freerider

 February 23, 2012, 02:24 #28 New Member   Join Date: Feb 2012 Posts: 3 Rep Power: 7 thx for the reply. will figure it out.

March 16, 2012, 12:15
#29
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sheth roh
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Quote:
 Originally Posted by -mAx- for coefficients, you have to set reference parameters http://my.fit.edu/itresources/manual...ug/node972.htm
I would like to know how can we plot Cl Vs time and Cd-time on a moving body. At each instance the vector perpendicular to surface would change in such cases.

October 8, 2015, 11:39
#30
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Quote:
 Originally Posted by -mAx- for coefficients, you have to set reference parameters http://my.fit.edu/itresources/manual...ug/node972.htm
I am working on similar problem that I need to calculate drag force, but I have a cylinder which is rotating on its own axis as well as on the central axis of a 5 times larger cylinder. So the force component is not x or z it will be some combination of x and z. Like the radius is r=sqrt(x^2+z^2). I am not sure about the resultant drag force, how to compute it.

 March 21, 2017, 20:53 fluent 3d #31 New Member   Barata Laode Join Date: Nov 2016 Location: Kanazawa Ishikawa JAPAN Posts: 1 Rep Power: 0 Dear all, I am a new comer in fluent analysis, Does anyone can provide possible explanation why I get zero Cl value in my result, I run fluent 3d rectangular cantilevered into water tunnel thansk alot regards Barata

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