StreamFunction
Hello Forum,
I am doing an analysis to a cavity flow using SimpleFoam....:) Is there any known issue/error with the OF(2.1.2) function StreamFunction ? Apparently, I am having proper results within my vorticity vector field but when I plot the point field resulting from the streamFunction in Paraview, it seems that the results are 10 times smaller....I also see that the units of the streamfunction scalar field are L3 T-1. How are these units being derived? Regards, Luis |
Hi Luis,
Can you provide a simple test case? Best regards, Bruno |
1 Attachment(s)
Dear Bruno and Luis,
I find the same with version 1.6-ext: the stream function seems to be too small by a factor of 10 and has dimensions length^3/time. I attach a case of a linear shear flow, U = (y/H)*V, with H the height of the domain, and V the velocity at the upper boundary. The stream function should be: \Psi = 0.5*((y/H)^2 -1)*V*H best regards, Christiane |
Hi,
the factor 0.1 seems to stem from the cell width in the empty direction, which is \Delta z = 0.1 in the above example. Reducing \Delta z to 0.01 also reduces the streamFunction by another factor of 10. So it seems, that the streamFunction utility computes \Psi*\Delta z, not \Psi. This would also explain the dimensions length^3/time. Do you agree? best regards, Christiane |
Greetings Christiane,
Many thanks for the test case, but I haven't yet managed to look into it. But I've taken a quick look into the source code of "streamFunction" on both 2.2.x and 1.6-ext:
Another indication is that it doesn't seem to work for 3D simulations, because it assumes that Z is the empty orientation. I'll try to look at the test case later today. Best regards, Bruno |
Hi Bruno,
yes, the face flux field phi is phi = U_f & S_f, with S_f the area of the face. For the computation of the stream function U_f & S_f/\Delta z would be needed instead. best regards, Christiane |
Hi Christiane,
Of course! Why didn't I visualize that... the face area still depends on Z, even though the flow is only over X-Y. OK, then there are 2 immediate solutions:
Bruno |
Hi Bruno,
thanks! I requested bug fixes at both sites: http://www.openfoam.org/mantisbt/view.php?id=976 http://sourceforge.net/apps/mantisbt...iew.php?id=185 best regards, Christiane |
bug still is available in OpenFOAM_4ext but solved in foundation version.
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Hi all
Does streamFunction work on openFoam-v7? |
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