Hi all,

What is the correct way to set smooth coefficients in space for high 
p-order of elements simulation in deal.ii?

E.g. in Step-6 nonconstant coefficient is a step function  alpha=20 for 
R<0.5 and alpha=1 otherwise (0<R<1).  How to set it to be a smooth 
function, e.g. some polynomial function of order 'n' like 
alpha=20*(1-R^n)+1? So it should be enough to use few high-order elements 
for the whole model to converge to the smooth solution.

I`ve checked a number of tutorials 
(e.g. 
http://www.dealii.org/developer/doxygen/deal.II/step_4.html#Righthandsideandboundaryvalues
 
, equation data section in step-27, and few others - all of them use a 
point-wise approximation of an analytic function  (so it is tuned for 
h-refinements), which is practically the same as a step function for a 
given mesh. 

This is actually very important when solving any open-boundary problem 
using perfectly-matching layer (PML), as soon as the latter needs to have a 
parameter grading (conductivity). Any ideas\examples how it can be done 
using deal.ii?

As an external reference, there is a PhD 
thesis http://arizona.openrepository.com/arizona/handle/10150/195940 with a 
description of a single cell PML. In a short, it is preferable to use one 
high-p  element to set PML from the point of view of performance (wave 
reflection) to DoF ratio.

Best regards,
Konstantin Ladutenko 


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