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Imposing Dirichlet domain condition
Posted Mar 5, 2014, 11:42 a.m. EST Fluid & Heat 2 Replies
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Hello all,
I wonder if there is a way to impose a Dirichlet condition not on a boundary but on a domain. Let's say, for instance, that at a time tn of my calculation I want to impose null velocity in my fluid depending on local temperature/concentration/etc. Weak constraints (Lagrange multipliers) are not well suited as the velocity condition is not initially set nor permanent...
So, how can I achieve that ?
Thanks in advance for your help !
Guillaume
I wonder if there is a way to impose a Dirichlet condition not on a boundary but on a domain. Let's say, for instance, that at a time tn of my calculation I want to impose null velocity in my fluid depending on local temperature/concentration/etc. Weak constraints (Lagrange multipliers) are not well suited as the velocity condition is not initially set nor permanent...
So, how can I achieve that ?
Thanks in advance for your help !
Guillaume
2 Replies Last Post Mar 7, 2014, 4:12 a.m. EST
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Posted:
1 decade ago
Guillaume,
If you have "Advanced Physics Options" activated in the Show menu, you can right-click on any physics interface and see sub-menus entitled "More" in the domain, boundary, etc. sections. These sub-menus contain options for adding pointwise or weak constraints on the various geometric entity levels. If you multiply the constraint expression by a conditional expression [e.g. u*(t>1)*(t<2)], you can turn the constraints on and off as a function of time.
This type of technique can be successfully implemented on a domain, but if you use it to specify something non-physical, strange results may ensue...
--
Luke Gritter
AltaSim Technologies
If you have "Advanced Physics Options" activated in the Show menu, you can right-click on any physics interface and see sub-menus entitled "More" in the domain, boundary, etc. sections. These sub-menus contain options for adding pointwise or weak constraints on the various geometric entity levels. If you multiply the constraint expression by a conditional expression [e.g. u*(t>1)*(t<2)], you can turn the constraints on and off as a function of time.
This type of technique can be successfully implemented on a domain, but if you use it to specify something non-physical, strange results may ensue...
--
Luke Gritter
AltaSim Technologies
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Posted:
1 decade ago
Hi Luke
I already tried with weak constraint but it lead to a singular matrix at the first step (even with a conditionally stated constraint ). However I did not try with pointwise constraints (I had not noticed this option ) which seems to work. Unfortunately I experience strong convergence problem with this condition enabled: as soon as the constraint is active, the calculation does not converge !
Well, thanks anyway for the tip !
Guillaume
I already tried with weak constraint but it lead to a singular matrix at the first step (even with a conditionally stated constraint ). However I did not try with pointwise constraints (I had not noticed this option ) which seems to work. Unfortunately I experience strong convergence problem with this condition enabled: as soon as the constraint is active, the calculation does not converge !
Well, thanks anyway for the tip !
Guillaume