# [aspect-devel] Questions on Boundary temperature model/Function

Wolfgang Bangerth bangerth at tamu.edu
Fri Feb 27 18:46:53 PST 2015

```On 02/27/2015 12:27 PM, Timo Heister wrote:
> We currently don't have a way to set different type of boundaries for
> different indicators, but you should be able to write it as one
> expression that will be evaluated for the top and bottom boundary (as
> a function of x and z). What happens if you do this?

For example, like this:

subsection Initial conditions
set Model name = function
subsection Function
set Variable names      = x,z
set Function constants  = Tcon=1673, xstep=0.5, dT=100, L=3000, \
sm=0.02, Ttop=273
set Function expression = if (z<1500, \
(((Tcon - (1-xstep)*dT) +  dT*(0.5 + \
(1/pi)*atan( (x - xstep*L)./(sm*L) ))) - Ttop) * \
(L-z)/L + Ttop \
, \
273)
end
end

Note the if(cond,yes-expression,no-expression) that switches based on the
z-coordinate.

Best
W.

--
------------------------------------------------------------------------
Wolfgang Bangerth               email:            bangerth at math.tamu.edu
www: http://www.math.tamu.edu/~bangerth/

```