Heat equation - Dual bodies - Volumic and Surfacic source

[LYS]

Dear elmer users,

Assume that we have a dual bodies material. The sample is heated with a pulse CO2 laser. The first body is partially transparent to the laser wavelength, thus we have an volumic heat source. The second material is opaque to the wavelength, the part of the energy which has been transmitted through the first body is deposed at the surface of the second body (like a heat flux).
We have thus a heat source which is volumic in the first body and surfacic in the second.

I wrote a elmer program .sif in which this two heat sources had been taken into account but I'm not sure that the surfacic heat source is well applied to the second body.
I read in the elmer forum, that I need used the option "Flux Integrate Body= number of body" in the Boundary Condition to specify exactly the body in wich the heat flux is applied.

Is that I understand well the use of this option ?

Thank you very much
Elisabeth

[Juha]

Hi,

i don't really know what the "Flux Integrate Body" stands for, but it surely has nothing to do
with applying heat flux boundary conditions. You should be able to apply the heat flux to
given boundary simply by using something like

Code: Select all

Boundary Condition n
  Target Boundaries = id
  Heat Flux = value
End

'id' is the identification number of the boundary in the mesh files.

Regards, Juha

[LYS]

Thank you Juha for your fast reply,
I'm sorry, I didn't say in my first post, but I have write my Boundary condition like this :

Code: Select all

Boundary Condition 6
Target Boundaries(1) = 26
Name = "FluxSpotLaser 1"
Heat Flux = Variable Coordinate 1, Coordinate 2, Time
Real MATC "HeatFluxE1(tx(0),tx(1),tx(2))"
Heat Flux Bc = Logical True
Flux Integrate Body = 8
End

with like you can see the "Heat Flux condition", my question is just to know if the "Flux Integrate Body" option allows to force the application of the heat flux at the good body

Regards,
Élisabeth

[raback]

Hi Élisabeth

The "Flux Integrate Body" does not have any affect here. It is related to options in SaveData module where the user can define which side is used to estimate the flux over an internal boundary. Also, I don't understand what you mean by "good body".

-Peter

[LYS]

Hi Peter,

Thank you very much for your clearly reply
My material is formed with two differents material (with differents thermal and optical properties).
when I write "the good body" I did want say that the heat flux is apply only to the second material (opaceous to the laser wavelength) and not to the first (partialy transparent to the laser wavelength) for who I applied a volumic heat source.

Elisabeth

[raback]

Hi

If no special tricks is applied temprature will be continuous over any interface so you cannot choose on which side the heat flux is applied. The heat flux on internal boundary will be difference between conductive fluxes to the two different directions.

-Peter

[LYS]

I have an other question, when I run my program I observe that the value of temperature obtained for the value of z (z=n+1 see attached file) just after the Boundary position (where heat flux is applied) is completly illogical (I have for exemple a value of 287 K then the initial and external temperature is 293K ).
In my opinion, for the values of z>n+1 the temperature evaluation are logical.

I don't see where is the problem, have you seen already this problem ?

Élisabeth

[raback]

I don't see where is the problem, have you seen already this problem ?

Sorry, I don't quite get the problem. Generally problems with monotonicity are related to insufficient space or time-resolution near sharp interfaces. -Peter

[LYS]

I use a step of 1µm in the first material (20µm thickness) and also a step of 1 µm in the first 20 µm of the second material.
If I understand, you suggest that I decrease the space resolution arround the position of transition between the two material ?
Thank you
Élisabeth