Discussion Forum

Posted: 1 decade ago Jun 21, 2010, 1:28 p.m. EDT

Hi I believe you can also define a "Model - Definition - Probes" Plot and then use the two arrows "replace expression" and set in the desired item (depends on your physics and on the type of "probe plot" you have selected If you define the plot "up" in the tree it will be automatiacally generated for you for each solve (even if you delete the sequence, as if you define it lower down in the results section it will be cleared/deleted if you delete your sequence and you must redefine everything for the plot Have fun Comsoling Ivar

Posted: 1 decade ago Jun 24, 2010, 5:35 p.m. EDT

Thanks for your help, Ivar! I was able to get it working by replacing the "T" variable with "jh.normJ". I created a 1D Plot Group and chose "Line Graph". Next to "Y-Axis Data" header, I found all sorts of expressions depending on the physics being used in the model. For example, "jh.sigma" for electrical conductivity, "jh.Qh" for power dissipation density, and "solid.disp" for solid displacement. Knowing these expressions makes it easier to "talk" to COMSOL in its own language when there's no easy GUI (or at least, not one that I've learned about yet). Admittedly, it was quite a round about way to do it! But I thought I'd share. I am still getting familiar with COMSOL, and hope to get better at using probes like you suggested.

Posted: 1 decade ago Jun 25, 2010, 3:18 a.m. EDT

Hi then turn on the "equations" in the preferences menu, you will get a sub-tree entry with most relevant internal equations used by COMSOL, and with a nice description formost of them. These get populated only if there are someting relevant and the values are 0. This helps as the solver/study list is only there once you have set up a first full model The best way I have experienced to learn COMSOL is to take as many courses from COMSOL (see the event list) as possible but not all at the same time ;), to go to the conferences and follow the courses there, to do the homeworks as as many examples as possible from the doc, by starting with the simplest cases possible, and use the examples on the web sites (often one level of complexity higher). And finally to study the cases of others on the forum and try helping them, that has been the best learning booster for me. Have fun Comsoling Ivar

Posted: 1 decade ago Jun 25, 2010, 9:11 a.m. EDT

Oh neat -- I didn't know about the equation mode! Thanks! I'm excited to learn more about this great software.

Posted: 1 decade ago Nov 12, 2010, 12:31 p.m. EST

[QUOTE] Hello! I have a parametric geometry in COMSOL 4.0, and would like to plot the current density as a function of the change in geometry. I've been able to plot a maximum density plot in this way: 1. Right click Definitions --> Model Couplings --> Maximum (creates definition named maxop1) 2. Compute study 3. Create a 1D Plot Group --> Global Plot 4. Select data set and all parameter values 5. In the Expression column, type "maxop1(T)" 6. Plot chart Can I do something similar to plot the current density? What variable name should I use instead of T (I've tried nJ_dc and just J based on expression names from version 3.4)? Is there a list of names for other variables (heat flux, electric field, electric potential, etc.) available online somewhere? Thanks in advance for your help! [/QUOTE] When I try this method using Average instead of Maximum, I get an error stating "Unknown function Name: aveop1 plot: glob1 (Global)" What am I doing wrong?

Posted: 1 decade ago Nov 13, 2010, 4:20 a.m. EST

Hi it might be that if you have solved your case, then only you define the operator (higfher up in the model tree), the solution is not yet updated, you need to select the solution and performan manual "update" or rerun the simulation -- Good luck Ivar

Posted: 1 decade ago Jan 28, 2011, 4:09 a.m. EST

Thanks to both of u, From your discussion I have solved my problem of Parametric sweep of a structure going under joule heating. Regards