# COMSOL+Heat Transfer

1. Sep 6, 2008

### Skyeagle

Hi guys,

I found this forum by chance. Was wondering if anyone could help out with my problem. I am very new to this COMSOL and I am required to tackle a problem.

I am required to simulate laser drilling onto a material using comsol to obtain the heat transfer pattern. I have chosen silicon in the drop-down box

I used the New>FEM>Heat Transfer>Conduction>Transient Analysis.
I then created a rectangle with 3 sides thermally insulated and the top is having heat flux.

Under Boundary settings, I need to enter the equation in the Q field as the heat source
The equation is like this: (10^7) x exponential (-10^3 x X^2) for a time of 2 seconds.

I keep having syntax errors. How do I put in the equation properly?

Thanks.

2. Sep 6, 2008

### PerennialII

Hi Skyeagle,

Comsol syntax is pretty much identical to that of Matlab (well they share plenty of history) ..... so for your equation you might try something like:

(10^7)*exp((-10^3)*x^2)*(t<=2)

I'm assuming what you're after with the "x" is a cartesian coordinate (or that is how comsol would interpret from the above)? The "t<=2" evaluates as "1" for t <=2 (assuming your t is in seconds) and 0 otherwise (you can do the same thing with a simple "if" - construct or use several of the other available step - function - lookalikes, if you for example wish to smoothen the transition to 0 value).

3. Sep 6, 2008

### Skyeagle

PerennialII ,

Thanks for the reply. yup. I got the waveform as per the syntax that you have given. Right now I need to generate the temperature profile which I am facing some problem.

Its not what I am expecting.

4. Sep 7, 2008

### PerennialII

Yeah, these often take surprising chunks of time to get them working. Let me know if can try to come up with further pointers.

5. Sep 8, 2008

### CFDFEAGURU

If you like I can help you out with a simulation in Ansys. Let me know if you want my help.

6. Feb 27, 2009

### cap_kenn

hi, im dont no nothing about COMSOL, apart from the using a user guid to make a model and plot a graph.. what i wish to achieve is a wire ( rectangle ) which gives heat at one end and over time the heat eventually transfers over to the other.

Thanks kenn

7. Feb 28, 2009

### rr00053

i think you cn try with the heat transfer using the conduction model to do this....try using tat and contact if u have any doubt

8. Mar 2, 2009

### cap_kenn

as a complete novis to this software, could you explain to me in a step by step process how to achive a model of heat flow from one end of a wire to another? i would reli appreciate this, as well as a stress flow model aswell (where one end increases in tensile stress and the other end increases in compressive stress), many thanks