On 3/11/21 10:33 PM, Giselle Sosa Jones wrote:
I have a diffusion problem where the diffusion coefficient K depends on the
solution at the previous time step and is therefore discontinuous. I am trying
to implement a weighted average for DG, which is similar to the standard
average, with the difference that the weights are not 0.5, but a weighted
average with the value of K on each side of a face. I have been
using VectorTools::point_value to evaluate approximate solutions at given
points, but now I need to evaluate those approximate solutions at the two
neighboring cells. Do you have any idea about to how to approach this?
Giselle,
VectorTools::point_value() is not the way to do this. It's extremely expensive
to evaluate solutions this way, and as you noticed already, it's not the right
tool anyway at places where the solution is discontinuous.
The way this is supposed to work is by using FEValues/FEFaceValues to evaluate
an existing solution at the quadrature points. You should take a look at
step-15 and how it evaluates the previous solution when it builds the
matrix/rhs for the current nonlinear step.
Best
Wolfgang
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Wolfgang Bangerth email: [email protected]
www: http://www.math.colostate.edu/~bangerth/
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