wallGradT and wrong answer
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Hi everyone
I want to get normal gradient of temperature at wall boundary in laminar incompressible flow.I've modified wallGradU utility as someone in other posts said. I want to know why wallGradT remains fixed in some cells?and how I can make it correct? my geometry is pipe with 1 meter length and 0.003 meter radius and the blockMeshDict is like: Code:
convertToMeters 1; Code:
dimensions [0 0 0 1 0 0 0]; Code:
ddtSchemes can any body help me? thanks. arjang |
Nobody can help?:(
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Greetings Arjang,
Well, knowing which posts you are referring to would help, in order to assess if something might have gone wrong. In addition, knowing the "U" and "p" boundary conditions would also help, as well as knowing which solver you have used and if has converged. And a picture of what your are seeing in ParaView would also help. Best regards, Bruno |
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thanks for your attention. I'm want help about wallGradT. Nu = wallGradT*D/(Twall - Tbulk) for calculating Nusselt number I've calculated bulk Temperature and also normal gradient of temperature at wall boundary. as you can see in the attached file,the amount of wallGradT in some cells remains fixed but the amount of Tbulk has increased continuously and this fact caused the Nusselt diagram to have oscillation.(please look at attached files) but It must not have this behaviour. I've used newSimpleFoam solver which I've added energy equation to. and the solution has converged( but the manner of convergence of T equation is not good,I mean the initial residuals of T did not constantly decrease). TEqn: Code:
fvScalarMatrix TEqn Code:
dimensions [0 1 -1 0 0 0 0]; Code:
dimensions [0 2 -2 0 0 0 0]; sincerely yours, Arjang Attachment 27269 Attachment 27270 |
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Hi Arjang,
Is there any chance you can share the complete case, instead of only parts of it? I ask this because at least the following information is still missing:
Because right now, my guess is that this is a sampling problem (insufficient data points or wrongly located points), or the case is incorrectly prepared. Best regards, Bruno |
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Hi Dear Bruno
yes why not:). and I've developed solver like below: createFields Code:
Info<< "Reading transportProperties\n" << endl; Code:
Code:
int main(int argc, char *argv[]) Code:
int main(int argc, char *argv[]) - I've plot these data over line in paraFoam with following coordination: point1: (0 0 0.003) point2: (1 0 0.003) and the resolution is 100 (this cause 101 points being plotted). Thanks Best Regards. |
Hello Arjang,
just a few question and hints.
Code:
fvScalarMatrix TEqn 5. As you mentioned that your case has no smooth convergence for T i think this is a manner of the not used underrelaxation in your equation. Code:
{ I think if you Change your solvers and add the Relaxation to your TEqn you will get accurate and better results. Try it and let us know. Regards Tobi |
Hi Tobias
thanks for your Tips. I did your suggestions I mean: 1.using PBiCG instead of BICCG for T. 2.adding TEqn.relax(); inTEqn.H now the convergence of T is smooth:) but the oscillations in Nu diagram exists yet:(. Danke Schon . Arjang |
Quote:
Hi, did you check the hints Bruno mentioned? At the moment it seems that it is a sampling Problem like he said. Additionally. Check the regions with These "Nu" oscillations. I think Bruno is telling you the correct Problem because if you interpolate the massflow of an inlet and outlet you will not get the same values (Interpolation Problem with paraview). Regards Tobi |
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