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-   -   How to model a moving heat source? (http://www.cfd-online.com/Forums/flow-3d/27371-how-model-moving-heat-source.html)

James March 12, 2009 14:56

How to model a moving heat source?
 
How can FLOW-3D be used to model a moving heat source? The user manual only tells how to model uniform or localized heat sources. But what if the location of a heat source changes during a process? Thanks!

HC March 12, 2009 15:06

Re: How to model a moving heat source?
 
is the heat source inside some solid object? if so, you may try create an extra moving solid object and use it as the heat source.

James March 12, 2009 15:21

Re: How to model a moving heat source?
 
It is on the surface of a solid object. For example, a moving laser beam is irradiated on the surface of a metal part.

HC March 12, 2009 15:28

Re: How to model a moving heat source?
 
I think you can try creating a moving object and specify the heat source with density*specific heat equal to 0. that way, the heat source value becomes the heat flux at the component's surface.

James March 12, 2009 16:54

Re: How to model a moving heat source?
 
Thank you! In this way, how can I apply the heat flux only at a portion of the component's surface? I mean, the heat source is not applied to the whole surface, just to a circular region of the surface.

HC March 12, 2009 18:11

Re: How to model a moving heat source?
 
One way is to create another moving component that wraps around the heat source and only have that circular region facing outwards. This method might not be appropriate for the cases you are simulating, as you do not want the new moving components to affect the heat transfer/fluid flow.

May I ask what kind of case you are trying to simulate?


James March 12, 2009 22:58

Re: How to model a moving heat source?
 
I am simulating laser coating.

HC March 13, 2009 10:38

Re: How to model a moving heat source?
 
so how does the laser beam move? does it just moves along a flat surface? if it does, you can just try what we have suggested and you dont need to create another wrapping component as the other area on the moving heat source component will not be in contact with the material. you also need to specify free-slip on the moving component as the laser beam would not have any force acting on the material.

Anyways, basically you need to make sure no setup in the simulation would contradict the basic process in laser coating. if it does, please give more details on the process, or you want to think about customization.

James March 13, 2009 18:00

Re: How to model a moving heat source?
 
My application is like this: a laser beam passes over the top surface of the base material to induce local melting.The effect is that it brings a heat flux on the surface. Accompanying the laser beam is a droplet source of coating material that strike the surface and provide the extra material. So during the process, the surface of the base material is not flat because it is coated. It is something like laser welding.

The difficulty of modeling is that the heat flux is not on the whole surface at a specific moment (just a circular spot) and moves along the surface.

If I use customization, how should I do? Thank you!


H.C March 16, 2009 13:52

so do the laser beam and droplet source happen to be at the same location at that time? if not and laser beam melts the FLAT base material first before a droplet is placed on the surface, you can still use that technique to mimic the process.

the customization you could try is to modify heatfl.F. Basically you need to keep track of the i/j/k index of the cells where the laser beam is projected on, and to specify the heat source in the subroutine. It is kind of different as it is thermal energy per unit mass instead of heat flux at the surface, but it might be ok if the cells are fine enough.

James March 17, 2009 12:49

Re:How to model a moving heat source
 
Thank you for your reply! Yes, the laser beam and droplet source are always at the same location. But before laser beam melts the FLAT base material, probabily the powder particles will be blown off. I don't need to model this. In my simulation, I let the droplets fall onto the base material only after a molten pool has formed. Could you please say again what "that technique to mimic the process" is? Because you mentioned several methods, I am a little bit confused.

For the customization, is heatfl1 an array with subscripts i,j,k or a variable? Can I use other variables like t, xi(i),yj(j) and zk(k) in this subroutine? Another related question is: how does Flow-3D distingush among a void cell, a fluid cell and a solid cell? Thank you!

boy January 7, 2015 22:59

Quote:

Originally Posted by H.C (Post 209648)
so do the laser beam and droplet source happen to be at the same location at that time? if not and laser beam melts the FLAT base material first before a droplet is placed on the surface, you can still use that technique to mimic the process.

the customization you could try is to modify heatfl.F. Basically you need to keep track of the i/j/k index of the cells where the laser beam is projected on, and to specify the heat source in the subroutine. It is kind of different as it is thermal energy per unit mass instead of heat flux at the surface, but it might be ok if the cells are fine enough.

Hi H.C,

I'm doing the same thing as you have done years ago, since heatfl is power source per unit mass,when I define a gauss plane heat source, how can I convert power rate (unit: W) to power source per unit mass? In other words, when the power rate equal 1w, then heatfl= ?, thank you~


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