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Pointwise constraints for time derivatives are not supported
Posted Jun 18, 2010, 12:03 p.m. EDT 2 Replies
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Hello,
I am having problems running a model in COMSOL 4.0 where I receive the error "Pointwise constraints for time derivatives are not supported". I am aware that this was discussed before and that boundary conditions should be applied to volumes, surfaces and edges at the least but where my confusion lies is that the boundary conditions used work in COMSOL 3.5a but not in COMSOL 4.0.
The model I am recreating is the peristaltic_pump.mph example available with COMSOL 3.5a. The fluid subdomain has displacement derivatives for input velocities, such as ut and wt, for example . Yet when these are used in the same fashion in COMSOL 4.0 the error message "Pointwise constraints for time derivatives are not supported" is returned.
I would like to know what changed from 3.5a to 4.0 that this model, defined in exactly the same manner, does not run consistently between both versions of the software.
Secondly, how do I get this model to solve?
Thank you for your time,
Tyler Bevan
I am having problems running a model in COMSOL 4.0 where I receive the error "Pointwise constraints for time derivatives are not supported". I am aware that this was discussed before and that boundary conditions should be applied to volumes, surfaces and edges at the least but where my confusion lies is that the boundary conditions used work in COMSOL 3.5a but not in COMSOL 4.0.
The model I am recreating is the peristaltic_pump.mph example available with COMSOL 3.5a. The fluid subdomain has displacement derivatives for input velocities, such as ut and wt, for example . Yet when these are used in the same fashion in COMSOL 4.0 the error message "Pointwise constraints for time derivatives are not supported" is returned.
I would like to know what changed from 3.5a to 4.0 that this model, defined in exactly the same manner, does not run consistently between both versions of the software.
Secondly, how do I get this model to solve?
Thank you for your time,
Tyler Bevan
2 Replies Last Post May 18, 2011, 1:34 p.m. EDT
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Posted:
1 decade ago
Hi
I beleive it could come from the fact that a point "inherits" some of its "average" properties from the two or more lines intersecting at that location (just as lines inherit an average of the adjacent boundaries etc) this makes it very easy to build up singulartities on points, and often on lines too. For boundaries/surfaces these are of either two types: external, hence inherite from the single volume close by, or internal and there normally one apply continuity, else we have the fight with the assembly and the duplication of up/down conditions.
So try to modiufy your case to avoid point constraints, you can cetainly split up some of those lines/edges close to the points of interest, no ?
The difference 3.5 to 4 could come (I believe but do nt know) from slight changes in the inhertance means
Have fun Comsoling
Ivar
I beleive it could come from the fact that a point "inherits" some of its "average" properties from the two or more lines intersecting at that location (just as lines inherit an average of the adjacent boundaries etc) this makes it very easy to build up singulartities on points, and often on lines too. For boundaries/surfaces these are of either two types: external, hence inherite from the single volume close by, or internal and there normally one apply continuity, else we have the fight with the assembly and the duplication of up/down conditions.
So try to modiufy your case to avoid point constraints, you can cetainly split up some of those lines/edges close to the points of interest, no ?
The difference 3.5 to 4 could come (I believe but do nt know) from slight changes in the inhertance means
Have fun Comsoling
Ivar
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Posted:
1 decade ago
hi,
i have also same problem "Pointwise constraints for time derivatives are not supported". i tried with stationary solution.it gives some value.but when you tried with time dependent , it gives pointwise constraints error. if this error is due to some more line intersecting in geometry,then same error should come for stationary also.but in real it is not.
so plz give me suitable reply.....
i have also same problem "Pointwise constraints for time derivatives are not supported". i tried with stationary solution.it gives some value.but when you tried with time dependent , it gives pointwise constraints error. if this error is due to some more line intersecting in geometry,then same error should come for stationary also.but in real it is not.
so plz give me suitable reply.....