# Aerodynamic Coefficients

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 August 24, 2015, 11:16 Aerodynamic Coefficients #1 New Member   Sukratu Barve Join Date: Mar 2009 Posts: 16 Rep Power: 15 I am using sonicFOAM for a not very unsteady flow. I am using a 3D geometry for aerospace applications. The solver is working on the case and appears to be giving proper screen messages. Now I wanted the aerodynamic coefficients and realized that the controlDIct file has lines which make the solver record only lift, drag and moment coefficients, which may be used for 2D geometries. There are however, six such coefficients in all for me with my 3D case. Nobody seems to have required all six, perhaps! I did not find anything regarding that on the net! Any help would be appreciated.

 August 24, 2015, 13:24 #2 Senior Member   Hassan Kassem Join Date: May 2010 Location: Germany Posts: 240 Rep Power: 16 Sorry but your question is not clear, which coefficients you want to compute? Generally, If they are direction based, just define new forceCoeffs functionObject with different directions. OR you could develop new function object for that. Otherwise if you are looking to compute different coefficients based on force type, you can define in controlDict forces functionObject and calculate the coefficient based on these pressure and viscous forces. Also it is possible to develop new functionObject for this purpose.

 August 25, 2015, 11:21 #3 New Member   Sukratu Barve Join Date: Mar 2009 Posts: 16 Rep Power: 15 I need to calculate the following aerodynamic coefficients: Drag Coeff.(C_D) Lift Coeff.(C_L) Side Force Coeff. (C_S) Rolling Moment Coeff. (C_l) Pitching Moment Coeff.(C_m) Yawing Moment Coeff. (C_n) The syntax for the lines to be included in controlDict for lift and drag seem to be liftDir (1 ,1 ,1 ); dragDir (1,0,1); and there is a line to take in the pitching axis pitchDir (0,0,1) ; which presumably give the direction about which the moment of the "moment" coefficient in two dimensions is calculated. (Please ignore the details of the directions above. I have cooked them up just to explain which lines I mean) Now do I simply say something like yawDIr (0,1,0); to obtain the yawing coefficient ? Or will I have to ask the solver to give me force components and moment components in a file and obtain the coefficients separately by shell scripting and formulae code files? Right now, that seems to be the best option for me. But something like sideforceDir (1,0,0); would be fabulous

 August 25, 2015, 11:27 #4 New Member   Sukratu Barve Join Date: Mar 2009 Posts: 16 Rep Power: 15 Sorry it is not pitchDir but pitchAxis.

 August 25, 2015, 11:44 #5 New Member   Sukratu Barve Join Date: Mar 2009 Posts: 16 Rep Power: 15 Apparently this works. Will try it over tomorrow and post back on this thread. http://www.cfd-online.com/Forums/ope...ecoeffs-c.html Last edited by wyldckat; August 26, 2015 at 17:54. Reason: merged posts that were a few minutes apart

 August 25, 2015, 12:19 #6 Senior Member   Hassan Kassem Join Date: May 2010 Location: Germany Posts: 240 Rep Power: 16 Without even modifying the source code you can define two functionObjects for coefficient in controlDict with different directions and axis.

 August 25, 2015, 12:57 #7 New Member   Sukratu Barve Join Date: Mar 2009 Posts: 16 Rep Power: 15 Will try that as well.

 August 26, 2015, 11:15 Error during wmake operation #8 New Member   Sukratu Barve Join Date: Mar 2009 Posts: 16 Rep Power: 15 We seem to get problems during wmake. I have mentioned those in the following thread http://www.cfd-online.com/Forums/ope...tml#post561195