Discussion Forum

Posted: 1 decade ago 3 lug 2012, 11:38 GMT-4

Please reply me! i think the problem is from weak constraint! how can i adjust it?

Posted: 1 decade ago 5 lug 2012, 10:37 GMT-4

Why do I feel like NOBODY can help me?

Posted: 1 decade ago 6 lug 2012, 02:57 GMT-4

Hi I do not believe it's NOT that we do not want to help, but rather that we do not understand the question correctly, or exactly what in your model is not working. -- Good luck Ivar

Posted: 1 decade ago 6 lug 2012, 03:15 GMT-4

Dear Ivar, Hi! many thanks for your attention! i attached my model, my problem is: if i use "weak Constraint", my model couldn't solve!!!! and bring an error below: ------------------------------------------------------------------------------------------------------------------------ Failed to find a solution for the initial parameter. Singular matrix. There are 364 void equations (empty rows in matrix) for the variable mod1.lm. at coordinates: (0.01,0.003), (0.00966667,0.003), (0.00983333,0.003), (0.01,0.00263238), (0.01,0.00281619), ... and similarly for the degrees of freedom (empty columns in matrix). Returned solution is not converged. ------------------------------------------------------------------------------------------------------------------------ i don't know why?

Attachments:

• Hall_Effeft_2.mph

Posted: 1 decade ago 6 lug 2012, 03:38 GMT-4

Hi Why not check again tha all domains have materials defined, for me you miss a material and related physicsal constants, hence the error -- Good luck Ivar

Posted: 1 decade ago 6 lug 2012, 03:53 GMT-4

Hi, thanks, ok, i define copper for contacts, and also i put "shlag(2,'lm')" in constraint expression! but it bring error yet!!! strange for me is, when i disable "weak constraint" it working! would you please find attachment...

Attachments:

• Hall_Effeft_2.mph

Posted: 8 years ago 13 gen 2017, 15:48 GMT-5

I realize this thread has been dormant for a while, but someone may still find a working version of the simulation useful, so my attempt is attached. I disabled the weak constraint, as I'm not sure what the physical purpose is in this case... all of the geometric boundaries have conditions assigned via other nodes. schlag seems to be an outdated function used to define a Lagrange shape function (see page 26, http://www.mscs.dal.ca/cluster/manuals/comsol/mlinterface.pdf) and is generally no longer used in the current version of comsol. Basically it's been replaced by the Discretization drop-down menu for weak constraint nodes. As far as this particular simulation goes (opening it in 5.2a), there was a problem for me with the current conservation nodes' domain selection. Current Conservation 2 should be applied to the large silicon rectangle in the middle only, as it's here we'd like to implement the effective conductivity; everywhere else, the isotropic conductivity should be employed. All in all, a neat little demonstration of modeling a Lorentz force without using a Lorentz Velocity Node (see AC/DC's mef module).

Attachments:

• Hall_Effect.mph

Posted: 7 years ago 6 ago 2017, 12:16 GMT-4

Hi Christian. Is there a possibility to have your Hall effect sensor simulation in COMSOL 5.2 ? Thanks. Ma Men.

Posted: 7 years ago 7 ago 2017, 02:34 GMT-4

I am sorry for interruption with my question but I tried from three months continuously to get the answer or any help that how to apply a constant/uniform M.Field in wave optics physics to check the effect on scattering cross section of gold nano sphere. Please help me Best Ali

Posted: 7 years ago 7 ago 2017, 10:33 GMT-4

Hey Ma Men, Perhaps the instructions here (http://evgeni.org/oldfish/Top_nine_hints_for_working_with_Comsol#What_this_allows_you_to_do) or here (http://femlab_users.yahoogroups.narkive.com/Cf9oJliO/comsol-users-how-to-open-a-file-made-with-a-new-version-with-the-previous-one) could be of use. I don't know much about transferring models between versions of Comsol, but check it out, there may be an easy way. Best, Christian