Menu

Discussion Forum

New Discussion
查找

Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

Space variant boundary conditions

Posted 2014年9月9日 GMT-4 04:42 Fluid & Heat, Heat Transfer & Phase Change, Computational Fluid Dynamics (CFD), Parameters, Variables, & Functions Version 4.4 5 Replies

Anoop Asranna
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Hello everyone,
I am modelling the combustion chamber of a biomass stove. For now, I aim to simulate just the fluid flows.
I am using the non isothermal flow interface to model this(axisymmetric). My fluid domain is continious and need to specify the heat source only in the interior of the combustion chamber.
I know this can be done using a step function. But how do you implement this step function on to a boundary condition? In my case, I am specifying a heat source and I want to implement the step function onto this. What is the syntax for the same?
Really need your help.Have been wasting too much time on this!

thanks,
Anoop
5 Replies Last Post 2014年9月10日 GMT-4 15:54
Pieter Westerik
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 2014年9月10日 GMT-4 09:44
To the Definitions or Global Definitions node you can add a Functions -> Step function, which has the default name 'step1', but you can change it, and also its parameters. Then you can use it in your heat source, you can give it the value 'step1(r)' or 'step1(z)' or '100*(1-step1(r))' or however you want to use it. Does that help?
To the Definitions or Global Definitions node you can add a Functions -> Step function, which has the default name 'step1', but you can change it, and also its parameters. Then you can use it in your heat source, you can give it the value 'step1(r)' or 'step1(z)' or '100*(1-step1(r))' or however you want to use it. Does that help?
Anoop Asranna
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 2014年9月10日 GMT-4 10:21
Thanks for the reply Pieter.
Not sure if it is working though. I defined a step function in global definitions. Then I added a heat source boundary condition(non isothermal flow). there in the Heat source section I put in 'step1(r)*2500' in the 'Total Power' space.(In my case, there is heat generation at every point inside the combustion chamber.I need to specify a step function because my domain is continuous )
When I run this there is an error message saying 'Strings are only allowed in function arguments'.
Am I missing something here?
Thanks in advance.
Thanks for the reply Pieter. Not sure if it is working though. I defined a step function in global definitions. Then I added a heat source boundary condition(non isothermal flow). there in the Heat source section I put in 'step1(r)*2500' in the 'Total Power' space.(In my case, there is heat generation at every point inside the combustion chamber.I need to specify a step function because my domain is continuous ) When I run this there is an error message saying 'Strings are only allowed in function arguments'. Am I missing something here? Thanks in advance.
Anoop Asranna
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 2014年9月10日 GMT-4 10:42
I have attached the file .Might be helpful.
I have attached the file .Might be helpful.

Attachments:

Anoop Asranna
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 2014年9月10日 GMT-4 10:42
I have attached the file .Might be helpful.
I have attached the file .Might be helpful.
Josh Thomas Certified Consultant
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 2014年9月10日 GMT-4 15:54
Anoop-

You must call your step function in the Total power edit field as follows:

step1(r[1/m])*2500[W]

This will use the r-coordinate independent variable as the input to your step function. The [1/m] makes the call to the step function unitless. This is not crucial but it avoids the text from turning orange indicating a units inconsistency.

--
Best regards,
Josh Thomas
AltaSim Technologies
Anoop- You must call your step function in the Total power edit field as follows: step1(r[1/m])*2500[W] This will use the r-coordinate independent variable as the input to your step function. The [1/m] makes the call to the step function unitless. This is not crucial but it avoids the text from turning orange indicating a units inconsistency. -- Best regards, Josh Thomas AltaSim Technologies

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.

Suggested Content