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-   -   Lift and Drag Coefficients (http://www.cfd-online.com/Forums/cd-adapco/55857-lift-drag-coefficients.html)

xdm February 12, 2007 11:36

Lift and Drag Coefficients
 
Hi guys, can you tell me the way to calculate lift and drag coefficients for a wing with star cd.

Thanks

Kasper Skriver February 13, 2007 05:27

Re: Lift and Drag Coefficients
 
You will have to somehow extract the forces. Normal and tangential. Then you would be able to calculate the coefficients from projected areas.


xdm February 13, 2007 06:14

Re: Lift and Drag Coefficients
 
Kasper, i know the theory! I just want to know the commands in pro-star!

Kasper Skriver February 13, 2007 06:18

Re: Lift and Drag Coefficients
 
Ho much will you pay me then?


Kasper Skriver February 13, 2007 06:28

Re: Lift and Drag Coefficients
 
In the star_uguide.pdf at page 9-26

7. Calculating aerodynamic coefficients " command ACOEFF.

This facility works in conjunction with values of total force components at the wall, loaded via the Wall Post Data dialog. A set of wall shells, enveloping the object whose coefficients are to be calculated, must also be created using a CSET operation.

a) add some shells on the wall boundary

b) do some wall post data

c) command acoeff, try help acoeff

d) pay my bills

BR and hope its working

Kasper Skriver

paulh February 13, 2007 14:50

Re: Lift and Drag Coefficients
 
You might also try to use 'Monitor Boundary Behavior' and export the forces per iteration. At the end of the analysis, import the text file into your favorite spreadsheet and do the math to get Cd & Cl. I would use this to judge convergence. I don't have any experience with wings, but for pass cars and heavy vehicles, drag settles down significantly after the residuals flatten out. However, use the acoef command for the final value. Although the trends are correct, there seems to be a problem with the absolute values coming out the boundary monitoring routines.

Tobbe February 14, 2007 09:19

Re: Lift and Drag Coefficients
 
CD-Adapco have a posdat subroutine for monitoring drag and lift. If you ask nicely they will probably give it to you for free. Otherwise, if its only drag and lift you are interested in and the geometry just is a simple wing, I would recomend using Star CCM+ instead, its much easier to monitor drag and lift in CCM+.

talha April 8, 2007 17:55

gambit modelling and fluent analysis of jeep
 
i would like to know and recieve the 3D modelling and analysis of jeep using gambit and fluent.


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