## Equation-Based Modeling in COMSOL Videos

##### Phil Kinnane March 7, 2011

COMSOL Multiphysics offers direct access to mathematical models utilized in its interfaces and allows users to customize their own theoretical model within COMSOL with unparalleled ease. Here are three video tutorials on how users can add their own Partial Differential Equations (PDEs) within the COMSOL Multiphysics interface.

### Natural Convection

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1. Murilo Pessoa de Oliveira April 13, 2013   11:17 pm

I would like to replace the fluid and include the AIR but also consider the effects of thermal radiation in the annular space, How to do this?

2. Phil Kinnane April 16, 2013   1:35 pm

Hi Murilo, the model here is a little out of date and probably wouldn’t be appropriate for the latest release. Also, it would be very difficult to include the radiation physics using the underlying equations. This is instead supported by the Heat Transfer Module

3. Amin Parvizi October 2, 2013   9:23 am

Greetings,

As a matter of fact, I have two Poisson equations with two different source term ( D^2 =f1 and D^2=f2 , D^2 is Laplacian) in 2D and , I do not know what is the boundary condition. Would it possible to use the equation based modeling in Comsol to solve this kind of equations?

Best Regards

4. Phil Kinnane October 7, 2013   10:51 am

Hi Amin,
Yes, of course you do need to know the boundary conditions, but once you figure that out, you certainly can solve two coupled Poisson equations in COMSOL.

5. Nor Syamimi October 11, 2013   4:01 am

hi, i am currently doing on solid mechanics model..i’m having trouble to calculate the line length of my model before and after deformation to calculate the object elongation. I am an beginner in comsol..

mimi

6. Ozgur Taner October 21, 2013   4:59 pm

Is it possible to edit one of the coefficients as a second PDE’s dependent variable? For instance, changing ‘alpha’ in coefficient form as ‘u2′. In this case, does Comsol apply the nabla operator to both of the variables, or it only considers alpha as a coefficient (which will be the value of u2 in this case)? Thanks in advance.

7. Nishanth Mehanathan January 22, 2014   12:05 am

Hi How can I include curl of a vector in the PDE …

8. Hassanein Mobarek October 24, 2014   6:28 pm

Hi,
I have a question regarding to create my own PDE in COMSOL, I know that I have to use one of three templates available in COMSOL but still I don’t know how to transfer my high nonlinear equation into one of the equation templates.
Regards

9. Phil Kinnane October 27, 2014   8:57 am

Hi Hassanein,

You may want to check out the following blogs that also talk about the subject:
http://www.comsol.com/blogs/solving-algebraic-field-equations/
http://www.comsol.com/blogs/equation-based-modeling-a-custom-model-of-a-beating-heart/
http://www.comsol.com/blogs/understanding-traffic-congestion-via-equation-based-modeling/
http://www.comsol.com/blogs/modeling-viscous-fingering-equation-based-modeling/

Failing that, I suggest that you make an attempt and, if this doesn’t solve, then send your attempt to the Support team (support@comsol.com) to see whether they can help you.

Best regards,

Phil