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absolute tolerance for thermal stress problem
Posted 10 déc. 2011, 15:42 UTC−5 Version 4.1, Version 4.2, Version 4.2a 3 Replies
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So I am modeling the 2D transient freezing of a cylinder of tissue with 80% water (my model is a 2D wedge as Im assuming L >> D). I am using a quasi-static viscoelastic model with time dependent temperature equation in the thermal stress module. Therefore I expect a 7% increase in total volume (under the assumption volumetric expansion of water is 9%). My initial radius is 0.01m and so I expect a final radius 0f 0.0103 which tells me I expect a final displacement of 3.5*10^-4 m.
Now my question is, what do I set the relative and absolute tolerance? I know you should set the absolute tolerance one order of magnitude less than the displacement in order to get any accuracy. But which displacement do I consider? DO I use the displacement at each time step or the displacement from the initial and final states? During each time step the displacement is ~10^-8 m.
Currently, I am using relative tolerance = 0.0001 and absolute tolerance = 10^-6 to 10^-8. Any suggestions? I have been looking at the effects of varying tolerances and increasing elements. I see that as I decrease my absolute tolerance, the convergence plot osscilates more and more.
Thanks
Alex
Now my question is, what do I set the relative and absolute tolerance? I know you should set the absolute tolerance one order of magnitude less than the displacement in order to get any accuracy. But which displacement do I consider? DO I use the displacement at each time step or the displacement from the initial and final states? During each time step the displacement is ~10^-8 m.
Currently, I am using relative tolerance = 0.0001 and absolute tolerance = 10^-6 to 10^-8. Any suggestions? I have been looking at the effects of varying tolerances and increasing elements. I see that as I decrease my absolute tolerance, the convergence plot osscilates more and more.
Thanks
Alex
3 Replies Last Post 20 déc. 2011, 10:09 UTC−5