Discussion Forum

Hi, Evgeny!

But Comsol not calculated the part of expression...

You can see on the screenshot (Screenshot_1.png) that Peicewise function works correctly.

Expression field absolutely don't has contects help...

It's not exactly the case. With CTRL+Space shortcut you can open the list of parameters, variables, functions and operators that you can use in Expressions (see the Screenshot_2.png).

The help of Comsol in laptop version is too small...

Please check that help files are installed. Online version of the help system is available here: https://doc.comsol.com/6.1/docserver/#!/com.comsol.help.comsol/helpdesk/helpdesk.html

Hello Dmitry

Thank you for you quick reply 1. Yes, context help is working by CTRL+SHIFT, but only for Expression field not for Function. 2. Please see the results of calculation fuction on my laptop... The both function gives a equal results. It is too strange, may be it my error and i'm a stupid. 3. Please help me and show (give) the direct link to paragraphs in your link ( https://doc.comsol.com/6.1/docserver/#!/com.comsol.help.comsol/helpdesk/helpdesk.html), where i can find the complete list of all variables, operators and etc which i can to implement in Expression and Function field.

Best regards, Evgeny

Evgeny,

In the "with" screenshot, the plot is of a function called Myrad, not hrad. Could that be the issue?

Jeff

Hello Jeff

"Myrad" it was previous function name before correction. I have change the name and at any case results the same - not correct. After your message i repeated few time to calculate - negave. I'm confused, the my version of Comsol is last - 6.1.0.282. This is a error of system i think, because the d(Enth(T),T) not working as well (my other forum topic). I'll thinking...

Best regards, Evgeny

Hello Evgeny,

If I change the function definition to include 293[K] in the piecewise function and click the Plot button, the values of the plotted function change as expected in the Function Plot window. I cannot really see any other reason than that you have not updated the function plot.

For lists of available mathematical and logical functions, user-defined functions, physical and mathematical constants, operators, and variables that you can use in expressions in your COMSOL Multiphysics models, see the Global and Local Definitions chapter in the COMSOL Multiphysics Reference Manual (also available in the Help and Documentation windows in the COMSOL Desktop where you can search for topics).

Note that some variables, such as the spatial coordinates, depend on the chosen space dimension in the model component, and that variables have a "scope" (that is, some of them are only available in a model component and depending on which physics interfaces you have added). There is also a "scope syntax" for accessing, for example, material properties during results evaluation. In the settings for plot nodes, for example, you can also use Ctrl+Space or the Insert Expression and Replace Expression buttons to choose from all available and applicable variables.

Best regards,

Magnus

Hello Evgeny,

If I change the function definition to include 293[K] in the piecewise function and click the Plot button, the values of the plotted function change as expected in the Function Plot window. I cannot really see any other reason than that you have not updated the function plot.

For lists of available mathematical and logical functions, user-defined functions, physical and mathematical constants, operators, and variables that you can use in expressions in your COMSOL Multiphysics models, see the Global and Local Definitions chapter in the COMSOL Multiphysics Reference Manual (also available in the Help and Documentation windows in the COMSOL Desktop where you can search for topics).

Note that some variables, such as the spatial coordinates, depend on the chosen space dimension in the model component, and that variables have a "scope" (that is, some of them are only available in a model component and depending on which physics interfaces you have added). There is also a "scope syntax" for accessing, for example, material properties during results evaluation. In the settings for plot nodes, for example, you can also use Ctrl+Space or the Insert Expression and Replace Expression buttons to choose from all available and applicable variables.

Best regards,

Magnus

Hello Magnus Please see the record of screen. I'm reinstall the COMSOL 6.1.0.282, but the result the same. This is a system bag i think

Evgeny,

I see the plot change, albeit subtly, at 0:40 in your video.

Note that T^4-293^4 is not very different from T^4 when T>300 (T^4 grows very quickly and dominates 293^4). When T<300, the 0.1*sigma_const multiplying factor causes both expressions you're plotting to be essentially zero and therefore visually indistinguishable.

Jeff

Thank you Jeff

It is correct. The values is too big and "covered" the small "-293^4" addition. This issue is closed "d" operator not working on Win7, and I'm update to Win 10. Now all working.

Best regards, Evgeny