[Getdp] ... thermal radiation between two surfaces ...

Matt Koch mattkoch at alum.mit.edu
Wed Mar 15 04:03:11 CET 2006

Hello Christophe,

thanks for your response to this posting as well. You are absolutely 
correct about your "integral" statement. I vaguely understand your code 
below, though, but mostly, I am wondering how one knows over what space 
the integration takes place? For example, "Gamma" could have a radial 
and axial direction, so is the integral over "rdr" or "dz" or a 
combination? Also, which quantity is being integrated - I am assuming it 
is "q", but what then is "foo"? Also, this seems to be the integral of 
"q" on a surface acting on quantity "q" of that same surface. What if I 
need integral of "qA" of surface A acting on quantity "qB" of surface B?

More generally, I would like to make a Region A interact with a Region 
B. Ideally that is via radiation and conduction, including integrals 
such as the one above. However, I am not at that level yet, i.e. I want 
to hold off on integrals and stick to the quantities themselves for now. 
I am still trying to figure out how to formulate the problem in general, 
and how to make specific quantities (e.g. the temperature on a surface 
at a specific position) from Region A available to Region B (at a 
specific surface and position).

I have taken the liberty to include a set of files that try to 
accomplish this, but it is obviously not correct. Perhaps there is a 
small modification that would make it work? This is built upon the disk 
example I sent earlier, only now there are two disks (A and B), whereby 
disk B has a heat flux imposed onto it, and I want to make the 
temperature on disk B available to disk A, because disk B would 
obviously heat disk A, such as by convection and radiation. Perhaps you 
can help?


Matt Koch, Ph.D., P.E.
Science & Technology Consultants (SciTeX)
978-726-4202 (c)
mattkoch at scitex.us

Christophe Geuzaine wrote:
> mkoch at gvtc.com wrote:
>> Hi there,
>> I have seen radiation in GetDP applied to a SINGLE surface in a 
>> similar fashion
>> as convection. That is to say, both transfer heat into the 
>> temperature of
>> "infinity" or "bulk" or "ambient" via effective heat transfer 
>> coefficients.
>> I am interested in radiation BETWEEN the surfaces of TWO bodies, both 
>> modeled in
>> GetDP and both changing temperature as the problem dictates. An 
>> additional
>> complication enters with geometric configuration (or view) factors, 
>> which are
>> typical of radiation. But I think I can handle those as long as I 
>> know how to
>> "access" and "combine" the two surfaces and their temperatures in the
>> FunctionSpace and the Formulation. Can anybody get me started on such a
>> problem?
> Doesn't this lead to an integral term, where the value at one point 
> depends on the values at all other points on the boundary?
> Then you might want to look at "Integral" quantities in Formulations 
> (instead of "Local"). I'm not sure if there is an example on the 
> mailing list for this, though. An integral term will look something 
> like this:
> Formulation {
>   { Name MagSta_phi; Type FemEquation;
>     Quantity {
>       { Name integral; Type Integral; [ foo[] * Dof{q} ];
>         In Gamma; Integration I1; Jacobian JSur; }
>       ...
>     }
>     Equation {
>       Galerkin { [ bar[] * Dof{integral} , {q} ] ;
>                  In Gamma; Integration I1; Jacobian JSur; }
>       ...
>     }
>   }
> }
>> I have loosely explored the following two sections of the 
>> documentation, but do
>> not want to waste time on it if it is not the right approach.
>> 5.5.2 High order nodal finite element space
>> 5.5.3 Nodal finite element space with floating potentials
>> Thanks,
>> Matt Koch, Ph.D., P.E.
>> President
>> Science & Technology Consultants (SciTeX)
>> 978-726-4202 (c)
>> mattkoch at scitex.us
>> www.scitex.us
>> ----------------------------------------------------------------
>> This message was sent using GVTC's Webmail System.
>> _______________________________________________
>> getdp mailing list
>> getdp at geuz.org
>> http://www.geuz.org/mailman/listinfo/getdp
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