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Strange results when solving on a picometer scale.
Posted Feb 21, 2011, 4:47 a.m. EST Heat Transfer & Phase Change, Studies & Solvers Version 3.5a 1 Reply
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Hi,
I wish to model heat flow along actual chains of polymers.
Because of this I am using models with sizes of the order of picometers in 2D, and I am solving with the heat transfer by conduction mode with transient analysis.
Problem:
When I make my models there seems to be heat entering the model even though I havn't defined any sources of heat yet.
If I simply graw a box and press solve (with the UMFPACK solver) I get an error saying:
"Repeated error test failures. May have reached a singularity."
and COMSOL tells me my box with no sources of heat defined has a temperature of 3.36e302 K.
I tried switching to the PARADISO solver and I get a different error saying:
"Error in linear system solver.
The_relative_error_is_greater_than_the_relative_tolerance"
I get no such errors unless I am working on tiny picometer scales.
Does anyone know what could be the cause (and solution to) these errors and these 'phantom' sources of heat?
Thank you for taking the time to reply.
I wish to model heat flow along actual chains of polymers.
Because of this I am using models with sizes of the order of picometers in 2D, and I am solving with the heat transfer by conduction mode with transient analysis.
Problem:
When I make my models there seems to be heat entering the model even though I havn't defined any sources of heat yet.
If I simply graw a box and press solve (with the UMFPACK solver) I get an error saying:
"Repeated error test failures. May have reached a singularity."
and COMSOL tells me my box with no sources of heat defined has a temperature of 3.36e302 K.
I tried switching to the PARADISO solver and I get a different error saying:
"Error in linear system solver.
The_relative_error_is_greater_than_the_relative_tolerance"
I get no such errors unless I am working on tiny picometer scales.
Does anyone know what could be the cause (and solution to) these errors and these 'phantom' sources of heat?
Thank you for taking the time to reply.
1 Reply Last Post Feb 21, 2011, 6:07 a.m. EST
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Posted:
1 decade ago
Hi
if you go too small you must ensure a) you have also set the geometry relative and absolute repair sizes such that your geometry is not misinterpreted. b) check your scaling you might get a numerical issue, you can ask the solver to be more detailed for its log in the solver subnodes (sorry that is for 4)
--
Good luck
Ivar
if you go too small you must ensure a) you have also set the geometry relative and absolute repair sizes such that your geometry is not misinterpreted. b) check your scaling you might get a numerical issue, you can ask the solver to be more detailed for its log in the solver subnodes (sorry that is for 4)
--
Good luck
Ivar