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June 14, 2011, 13:27 |
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#61 |
Member
The True
Join Date: Dec 2010
Posts: 80
Rep Power: 15 |
I have to change the pRef value to calculate the forces.
I am adding this statement to functions forces: pRef 1000; This does not change anything in values, it looks like it is invariant to the pRef value. How can I adapt the pRef value |
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June 16, 2011, 09:39 |
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#62 |
Member
The True
Join Date: Dec 2010
Posts: 80
Rep Power: 15 |
The flow field looked oke but given Cl value was not oke. So, I decided to calculate the Cl value by sampling pressure values. I get, Cl = 0.166, which looks oke , for airfoil at 0 angle of attack. ( I have not calculated shear stress, don't know how to do it yet. For now I assume it is small, icoFoam)
The OpenFoam gives these value: Cl = 0.00166316; Cd = 0.0000724 Strange, I see it now, it looks like Cl and Cd is missing a multiply with 100 |
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June 21, 2011, 12:08 |
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#63 |
Member
The True
Join Date: Dec 2010
Posts: 80
Rep Power: 15 |
Still I haven't been able to specify the pRef value
I have tried this in the controlDict file, to calculate force coefficients: pref pRefPoint (x y z); but openfoam doesn't see pRefPoint(x y z) as a scalar I get this error: wrong token type - expected Scalar |
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September 8, 2011, 17:22 |
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#64 |
Member
Santiago
Join Date: Dec 2009
Posts: 85
Rep Power: 16 |
Hi,
I would like to be able to take a look at the libforces.so file to understand how it calculate the forces and eventually modify the library. Does anyone knows how to do that? Thanks |
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September 16, 2011, 18:13 |
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#65 |
Member
Santiago
Join Date: Dec 2009
Posts: 85
Rep Power: 16 |
This thread http://www.cfd-online.com/Forums/ope...tml#post324445 is related to force calculations. Does any one know the answer? Thanks
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February 3, 2012, 22:37 |
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#66 | |
Senior Member
musaddeque hossein
Join Date: Mar 2009
Posts: 309
Rep Power: 18 |
Quote:
wallPressure { type surfaces; functionObjectLibs ("libsampling.so"); outputControl outputTime; outputInterval 5; surfaceFormat raw; interpolationScheme cell; fields ( alpha1 p ); surfaces ( leftwalls { type patch; patches (leftWall); interpolate true; triangulate false; } rightwalls { type patch; patches (rightWall); interpolate true; triangulate false; } ); } |
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March 20, 2012, 07:00 |
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#67 |
Member
The True
Join Date: Dec 2010
Posts: 80
Rep Power: 15 |
Hi,
I have used for mine new simulation the solution of old case. Only the angle of attack ( so velocity and lift and drag coefficients ) is changed. The simulations went oke, however the calculated lift and drag coefficients are wrong. If I sample the pressure coefficients than I get the correct Cl , Cd values however not exact as I want. Because of the many simulations I do not want to run them all again. Is there any solution for this issue ? Is it possible to calculate the aerodynamic coefficients just based on the last time step ? Last edited by Eren10; March 20, 2012 at 08:41. |
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May 10, 2012, 10:13 |
Wall pressures in InterDyMFoam
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#68 |
Senior Member
musaddeque hossein
Join Date: Mar 2009
Posts: 309
Rep Power: 18 |
Dear all:
I am simulating a small 2D tank with dimensions 8m long, 5m high and 0.01m in depth. I am subjecting the tank to a sinusoidal displacement only and have modified the controlDict to provide wall pressures for the left and right walls at every 0.02 secs. In my opinion, if I am supplying a sinusoidal displacement, the pressures should also be sinusoidal. However when I plot the pressures corresponding to fluid phase in the left and right walls, I get what looks like a very choppy representation, which does not make sense. Any help or advice on how to fix this would be greatly appreciated, Thanks. I have attached the input plot and the pressure plot. My mesh size is 200x200x1 |
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October 17, 2012, 13:54 |
IRef Aref------> BI ELEMENT AIRFOIL
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#69 |
New Member
Fabio
Join Date: Sep 2012
Posts: 1
Rep Power: 0 |
One question: If I had a bi element airfoil (main&flap), I put in the patches the name of the two walls (main, flap), but for lRef e Aref I need to put 2 different values because the main airfoil and the flap have different chord and so different area. Help me please
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November 11, 2013, 12:16 |
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#70 |
Member
Pengchuan Wang
Join Date: Nov 2012
Location: Michigan USA
Posts: 58
Rep Power: 13 |
Hi Petter,
I know this is an old thread. But I want to know whether you have found a way to calculate the multi-phase torque? Right now I'm using interFoam as well. And I'm stuck with the multi-phase torque calculation. If you have any updates, please let me know. Thank you very much. Penghcuan |
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November 17, 2013, 10:09 |
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#71 |
Senior Member
musaddeque hossein
Join Date: Mar 2009
Posts: 309
Rep Power: 18 |
Is there some way to introduce fluid / wall friction? I am running sloshingtank2d in interdymfoam. The sloshing I get goes on as long as the simulation continues. How can I introduce wall friction so that the sloshing will slowly dissipate once the displacement stops?
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July 8, 2014, 11:42 |
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#72 |
New Member
yalong cai
Join Date: Feb 2014
Location: New York
Posts: 13
Rep Power: 12 |
Hello, Santos,
I have confusions about the value of rhoInf, in this thread, different values appeared, e.g. 1.17, 1.225 and 1000. This difference confuses me. Thanks for your attention. |
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September 2, 2015, 17:49 |
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#73 | |
Member
Join Date: Apr 2015
Posts: 42
Rep Power: 11 |
Quote:
Could you find out if your nu nu ... approach at the top of the transport properties file is a valid workaround for the problem? Just FYI: for the turbulent interFoam, there is no problem in the force calculations, but the problem exists when using laminar interFoam. This problem is "solved" when I take your approach but I am not sure if it is a correct way of tackling this problem. I am using 221 version. Cheers, Hossein |
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