Learning Forum

[AlexJohn]

I have one surface of the body which is exposed to several laser beams with Gaussian profile. I want to calculate changes in temperature of this body due to this lasers.

Firstly I tried to use MASS71 (Thermal Mass) element (because you can set heat generation for them which I did) for each node of the surface, using CP to couple their temperatures. But with this solution I have problem due to sizes and/or thermal capacitance of the this MASS71 body: what should I set as it's volume to get realistic results?

Secondly I tried to use simple heat flux with the help of function editor. It's quite simple for one laser, however for multiple it's not very suitable solution as I should sum all of single functions in one function. And I don't get how to do it in .mac file w/o using function editor - in case if I want to use, say, not 3 beams, but 5,6, e.t.c.

What is the most suitable solution for this problem? How can one get "sum" of two TABLES (I can get table in function editor for every single beam)? Which characteristic properties should I choose to simulate this with the help of thermal mass elements?

[Sean Harvey]

I have simulated Gaussian laser using the function editor and apply as SF in a command object. I use MAPDL to generate the function and then apply it. See a portion of apdl below (which is just a copy paste from APDL after generating the function. This is for just 1 laser.
I think what you can then do to apply multiple is we have to write some APDL to overlay surface effect elements on the themal element face, and repeat for how many lasers you have. Then you have multiple tables defined (one for each laser) and apply one table to the surface effect element(s). The heat flux goes into the surface effect element and then into the underlying mesh, all in parallel.
I don't know your model topology, but you can find thermal surface effect elements such as surf151, 152, etc.
If you need more details, let us know. I was thinking we could use *toper to add the tables, but not sure this works with tables generated from function editor. I tried but ran into some errors, so I thought the surface effect might be an alternative.
..! Commands inserted into this file will be executed just prior to the ANSYS SOLVE command.
! These commands may supersede command settings set by Workbench.


! Active UNIT system in Workbench when this object was created: U.S. Customary (in, lbm, lbf, s, V, A)
! NOTE: Any data that requires units (such as mass) is assumed to be in the consistent solver unit system.
! See Solving Units in the help system for more information.


! define gaussian heat flux


fini
/prep7


*DEL,_FNCNAME
*DEL,_FNCMTID
*DEL,_FNC_C1
*DEL,_FNC_C2
.
.
.
*SET,%_FNCNAME%(0,28,1), 0.0, -3, 0, 1, -2, 3, -1
*SET,%_FNCNAME%(0,29,1), 0.0, 99, 0, 1, -3, 0, 0
! End of equation: (({M1}*exp(-1*({TIME}-t0)^2/(t1)^2)))
!-->
fini
/solu


cmsel,s,flux_loc
sf,all,hflux,%gauss3%
allsel
Regards Sean

[Chandra Sekaran]

Will this work for your case?
i) Create multiple single functions (say 5 functions for 5 lasers) i.e. 5 tables.
2) Then you can coat the surface on which you want to apply the load with multiple layers of surf152 elements. So if you want to apply 5 lasers you coat the same surface with 5 layers of surf152 elements with keyopt(8)=1. Then apply the 5 laser fluxes- one to each layer using the SFE command with HFLUX option.
If you want to apply only 3 lasers, simply do not apply the load on two of the layers.

[Chandra Sekaran]

The load should be cumulative.

[AlexJohn]

Ah, yes, that sounds just like what I needed. Didn't know you can apply multiple heat fluxes using method described in both posts.
Big thanks!