[aspect-devel] Boundary Temperature

[Juliane Dannberg]

Hi Felipe,

if you want to use time-dependent boundary conditions, you can do that 
basically using the same input parameters you sent in your previous 
email, you just have to add another Variable name, the time t, in the 
'Function' subsection, and then use it in your function expression. This 
allows you to have spatially and temporally varying boundary conditions.

To see an example for how that would look like in the 'Function' 
subsection, you can have a look at the cookbook "5.2.3 Convection in a 
box with prescribed, variable velocity boundary conditions" in the 
Aspect manual, which addresses exactly that question (only for the 
velocity, and not the temperature, but the idea is the same).

Hope that helps!
Juliane


On 01/11/2017 01:38 PM, FELIPE ORELLANA ROVIROSA wrote:
> Hi Juliane,
>
>     Thanks for replying.
>
>      I have already successfully implemented many models with 
> homogeneous Dirichlet BC on temperature. I did this using 'set Fixed 
> temperature boundary indicators = bottom, top '.
>      What I am trying to do now is to prescribe space-time temperature 
> BC functions.
>
>      Yes I know there was a missing '')'' on my email text. Certainly, 
> I run the model with the correct math expression (well-balanced 
> parenthesis), but there was an error when copypasting on the email. 
> Congrats for being so sharp on the details.
>
>       Yes, yesterday I ended up thinking that there was no such a 
> thing like "prescribed temperature boundary indicators".
>
>       I will try my best following your suggestions on this. I guess 
> it should not be too hard (temperature is a scalar..).
>
> Many thanks,
>
> Felipe
>
>
>
> On Tue, Jan 10, 2017 at 9:57 AM, Juliane Dannberg 
> <dannberg at gfz-potsdam.de <mailto:dannberg at gfz-potsdam.de>> wrote:
>
>     Hi Felipe,
>
>     the error message basically already tells you what the problem is:
>     There is no parameter called "prescribed temperature boundary
>     indicators".
>     What you want to use is "Fixed temperature boundary indicators".
>     This is a comma separated list of names denoting those boundaries
>     on which the temperature is fixed and described by the boundary
>     temperature object selected in its own section of this input file
>     (see manual).
>
>     Section "5.1 How to set up computations" in the manual, and some
>     of the cookbooks, describe how to use this parameter. For your
>     example, if you want to have a fixed temperature at the top ad
>     bottom of your model, you would use
>
>     subsection Model settings
>       set Fixed temperature boundary indicators = bottom, top
>     end
>
>     In addition, in the section of the parameter file where you
>     specify the boundary temperature model, you have to specify the
>     model that you want to use (this line is missing in your example).
>     This plugin will then be used for all of the boundaries you have
>     specified in your list of Fixed temperature boundary indicators
>     earlier. This could look like this:
>
>     subsection Boundary temperature model
>       set Model name = function
>
>       subsection Function
>         set Variable names      = x,y
>         set Function constants  =
>         set Function expression = 1500  + 200*exp(-(16/(2.5e11))*(
>     (x-6e5)^2 + (y-4e5)^2 ))
>      end
>     end
>
>     (Note that there's also a ")" missing in your function expression).
>
>     Best,
>     Juliane
>
>
>     On 01/11/2017 12:03 AM, FELIPE ORELLANA ROVIROSA wrote:
>>
>>      Hi all,
>>
>>         I am trying to prescribe a function as the temperature
>>     boundary condition, say inhomogeneous Dirichlet for the heat
>>     equation.
>>
>>         I guess the syntax must be rather simple, but I am not
>>     getting it. I have browsed and browsed examples unsuccessfully.
>>
>>       I am trying things of this kind:
>>
>>        subsection Model settings
>>       set Fixed temperature boundary indicators   = top
>>       set prescribed temperature boundary indicators = bottom: function
>>
>>     subsection Boundary Temperature model
>>       subsection Function
>>         set Variable names      = x,y
>>         set Function constants  =
>>         set Function expression = 1500  + 200*exp(-(16/(2.5e11))*(
>>     (x-6e5)^2 + (y-4e5)^2 )
>>      end
>>     end
>>
>>      and when trying to run it, the system complains:
>>      Line <91> of file <input string>: No such entry was declared:
>>         prescribed temperature boundary indicators
>>         <Present subsection:
>>             subsection Model settings
>>
>>     ''invalid input parameter file''.
>>
>>     hope someone can help me,
>>     cheers,
>>     Felipe
>>
>>
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>
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