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January 7, 2011, 12:14 

#21  
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Quote:
this is really strange, there happens nothing at mine case ( the case is running well) this is mine controlDict. ( i am using 1.7.1 version ) FoamFile { version 2.0; format ascii; class dictionary; location "system"; object controlDict; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // application icoFoam; startFrom startTime; startTime 0; stopAt endTime; endTime 0.5; deltaT 0.0005; writeControl timeStep; writeInterval 20; purgeWrite 0; writeFormat ascii; writePrecision 6; writeCompression uncompressed; timeFormat general; timePrecision 6; runTimeModifiable yes; functions ( forces { type forceCoeffs; functionObjectLibs ( "libforces.so" ); outputControl timeStep; outputInterval 1; patches ( AirFoil ); pName p; UName U; log true; rhoInf 1; CofR ( 0 0 0 ); liftDir (0 1 0); dragDir (1 0 0); pitchAxis ( 0 0 1 ); magUInf 25; lRef 1; Aref 1; } ); 

January 7, 2011, 12:22 

#22 
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David Boger
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I'm using 1.6ext, so if there's a difference caused by 1.7.x, I'm not familiar with it.
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January 9, 2011, 19:02 

#23 
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how can I see the content of libforces.so (any lib file ) ?
If someone here uses 1.7x version please check for me if the libforces.so works as I have cited here . 

January 9, 2011, 19:39 

#24 
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David Boger
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Content of the library? Do you mean the source code? You can see it here. Go to "classes" and then pick "forces" from the list.
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January 9, 2011, 19:57 

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January 27, 2011, 17:28 

#26 
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Guilherme da Silva
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Dear foamers,
the sampleDict sent by velezisaza worked well for me. i am working to get Cp from a cylinder in a tunnel. however, the sample tool provided me all data on patch. How can I extract pressure information in a line, i.e., in the patch intersection with a plane (like normal to Z and at 0,0,0) ? Should I do it by hand? Does openfoam have a tool for this? regards, 

March 16, 2011, 06:00 

#27 
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Hello!
I've got a question about liftDir (0 1 0); dragDir (0 0 1); pitchAxis (0 0 0); liftDir and dragDir : Lift and Drag direction vectors are specified . But, if I ser liftDir (0 0.1 0) I have another result of Cd. So, how is right to set lift and drag Dir?And, what is pitchAxis? I blow on a box, Did I need it? 

March 16, 2011, 12:11 

#28 
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José
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Dear all,
I am using this function that it is needed in controlDict in orer to get the lift, drag and moment coefficients for a computation of the flow around an airfoil. The results I get for the lift and drag coefficients are very good compared to the reference I am using for both lift and drag coefficients but they are very bad for the moment coefficients. I use CofR=0.25*chord. Any idea why I am getting this bad results? Thanks, José 

March 17, 2011, 05:40 

#29 
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Maryam Mousazadeh
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hello.
I want to figure drag coefficient on walls of a cube which is located in a flat plane in 3D. I put ·rhoInf : the density of fluid. ·MagUinf : uniform velocity in the upstream of cube. ·Aref : the area of each cube's surface · lref :the length of each cube's edge · dragDir : flow direction (Uinlet=(1,0,0) in 0 directory) but this result is not true. would you tell me my mistakes? thanks. 

May 20, 2011, 10:59 

#30 
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Hi,
I have only replaced the mesh on the tutorial incom/simplefoam/airfoil2D. I want to check the Cl , Cd values. the airfoil size is the real size on the mesh. But I get nonsense values. I am using openfoam 1.7.1, with the following function: functions { forceCoeffs { type forceCoeffs; functionObjectLibs ("libforces.so"); patches (UpperCamber LowerCamber TrailingEdge); log true pName p; Uname U; rhoName rhoInf; rhoInf 1.225; magUInf 25; CofR (0.25 0 0); liftDir (0 1 0); dragDir (1 0 0); pitchAxis (0 0 1); lRef 1; Aref 1; outputControl timeStep; outputInterval 1; } } How can I solve this issue . Because I am using the tutorials I assume that the flow is correct. 

May 21, 2011, 08:13 

#31 
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Can someone please obtain the Cl, Cd, Cm values for the tutorial case , incompressible/simpleFoam/airFoil2D
I am using 1.7.1 version, I can't get the right values. I am almost thinking of a bug 

May 21, 2011, 12:35 

#32 
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May 21, 2011, 15:53 

#33 
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I have tried to get the coefficients for the given mesh in the tutorial (airFoil2D) as well as the mesh that I have drawn, both failed
Can someone maybe write here the obtained coefficients of tutorial airFoil2D case ? I will compare it with obtained value of the 1.71 version. 

May 23, 2011, 09:58 

#34 
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can someone help me about this issue ?


July 5, 2011, 09:34 

#35 
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I have obtained lift and drag from forceCoefficients. I have also calculated lift and the drag using the data of wallShearStress and the pressure distribution.
The results are: Cd Cl forceCoeff: 0.0113219 0.339877 calculatedMatlab: 0.009311 0.33927 Cl value is close, but the discrepancy of the Cd value is too big. From the experiments the Cd value should be around 0.00889 (airfoil). Am I doing something wrong ? or is it the forceCoeffs ?????? *if someone wants to test it I can send mine matlab file. 

July 5, 2011, 11:36 

#36  
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When I multiply the value of the calculatedMatlab with the density 1.225, I get 0.0114, almost the same value from forceCoeffs. Can someone please explain why I have to multiply the " skin friction coefficient ( obtained from the wallShearStress" with the density to get the same value ? ( incompressible flow) 

July 5, 2011, 14:28 

#37  
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July 6, 2011, 12:34 

#38 
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August 28, 2011, 17:56 

#39  
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Francois
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To all users using version 1.7.*, and having the dreaded:
Quote:
Simply add, in the function definitions: Quote:
Quote:
Francois. 

October 21, 2012, 10:08 

#40  
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Quote:
Hello! Did you figure this out?! I need the same. I need the Cp values on a point on the patch, i.e., in the patch intersection with a line (with given y, z and parallel to x for example) Could you please let me know how can I get that? Thanks! 

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