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ASK: easy functions in COMSOL4.3
Posted Sep 26, 2013, 1:54 a.m. EDT Interfacing, Heat Transfer & Phase Change, Parameters, Variables, & Functions Version 4.3b 3 Replies
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I am now trying to model a moving laser beam (as heat flux) on a steel plate. I try to do this by following steps:
1. build a solid block (domain 1) to represent the steel plate.
2. set 'heat flux' on one of the surfaces (boundary 1).
3. type in all the parameters including r0(laser on-plate beam diameter), Q(laser power)
4. to implement a moving laser beam, I use variables x0, y0(laser center coordinates, time dependent, x0=0+2*t, y0=1+2*t, speed=2).
Now I encounter problems to specify the heat flux on the boundary. What I want to do is to set it this way:
****************
function [q_in] = SetHeatFlux(x, x0, y, y0, r0, Q)
distance=(sqrt(x-x0)^2+(y-y0)^2);
if distance<=r0
q_in=Q/(pi*r0^2);
else
q_in=0;
end
****************
Well, first let us forget about the moving laser, i.e. x0, y0 = constant. The aforementioned function may be implemented using LiveLink for MATLAB, but the manual says that I have to make all the input and output vectors, which brings too much trouble as I am not good at handling matrix··· I would prefer an easy function like this.
Could you help me? My appreciations.
Ce ZHU
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For distance and q_in you can define following variables:
distance (sqrt(x-x0)^2+(y-y0)^2
q_in if(distance<=r0,Q/(pi*r0^2),0)
r0 needs to defined too.
Place these under "variables".
Best regards
Tero
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Thanks for your help. It works well. However, I am now having other problems. Instead of simple scan path like a straight line or a circle, I need to study complex paths like spiral, zigzag, and so on. You may consider that I need to use a lot of functions likes if(), for(). If I use the built-in functions of COMSOL, there will be too many variables. A user defined function like a m-file of MATLAB will be great (no such file or script in COMSOL, right?). The problem of LiveLink of MATLAB may be that I need to cope with vectors. Input arguments like power, radius of the laser beam, scanning velocity which are constant parameters may be not easy to handle as vectors in equations. I would much prefer to use them as scalar. What kind of program strategy would you recommend? Is there any modelling skills and concepts I need to know?
BTW, using external functions will definitely slow down the calculation right? But to what extent? What kind of external functions you would recommend, Matlab, C ?
Warm regards,
Ce
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Sorry for late reply...
Difficult task! I don't have experience external programs with Comsol so I cannot help you with this. Sorry.
Best regards
Tero