# OpenFOAM stress analysis results are showing 8-10% error with analytical solution.

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 September 10, 2012, 12:52 OpenFOAM stress analysis results are showing 8-10% error with analytical solution. #1 Member   Sangeeta Join Date: Jul 2012 Location: Kingston, Canada Posts: 70 Rep Power: 7 Sponsored Links Hello everyone, I am running solidDisplacementFoam problem for thermal stress analysis. My solution is converged but not showing good agreement with analytical solution. Simulation results shows 8-10% error with analytical solution. Does 8-10% error is fine for solid problems? Has anybody an idea? Regards, Sangeeta

September 10, 2012, 14:32
#2
Senior Member

Philip Cardiff
Join Date: Mar 2009
Location: Dublin,Ireland
Posts: 638
Rep Power: 23
Hi Sangeeta,

I presume you are referring to the "hollow cylinder with internal temperature" case as described by Timoshenko, Theory of Elasticity.

I tried this case and I found that the errors become very small (much much less than 1%) as you refine the mesh.

I have attached an graph showing a comparison between the results from a coarse and fine mesh.

To answer your question about "is 8-10% error ok?", in general for solid mechanics, it depends on the assumptions made in the analytical solutions (and in the numerical model). But for relatively straight-forward linear elastic and thermal elastic, the results should be very close to the analytical, especially as the mesh is refined.

Hope it helps,
Philip
Attached Files
 hotCylinder.pdf (79.4 KB, 114 views)

September 10, 2012, 15:06
#3
Member

Sangeeta
Join Date: Jul 2012
Posts: 70
Rep Power: 7
Quote:
 Originally Posted by bigphil Hi Sangeeta, I presume you are referring to the "hollow cylinder with internal temperature" case as described by Timoshenko, Theory of Elasticity. I tried this case and I found that the errors become very small (much much less than 1%) as you refine the mesh. I have attached an graph showing a comparison between the results from a coarse and fine mesh. To answer your question about "is 8-10% error ok?", in general for solid mechanics, it depends on the assumptions made in the analytical solutions (and in the numerical model). But for relatively straight-forward linear elastic and thermal elastic, the results should be very close to the analytical, especially as the mesh is refined. Hope it helps, Philip
Hi Philip,

Thanks a lot for the reply. Actually here I am solving another problem of thermal stresses for OpenFOAM validation. This problem is given in Timoshenko (page no. 399). This is for a rectangular plate.

I am going to email this case to you.

Thanks,
Sangeeta

May 5, 2017, 11:39
hollow cylinder with internal temperature
#4
New Member

Guido Lupieri
Join Date: Sep 2011
Posts: 3
Rep Power: 7
hello
I have tried to resolve the problem of the title, that is also a case of the tutorial,
by subjecting the 2D cylinder to the following boundary conditions:
for temperature T=100 in the hollow and T=0 at the outer patch,
for displacement D=0 tractionDisplacement (traction and pressure).

The results looks not as accurate as the ones of Dr. Cardiff/analytical case
that I have seen in this forum, even if I try to refine the grid.

Did somebody try the same tutorial case recently?
Thanks
Cheers

Guido
Attached Images
 computing_vs_cardiff.png (9.5 KB, 11 views)

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