[Getdp] Characteristic function in galerkin term

sdurand sdurand at cage.ugent.be
Fri Jun 19 09:30:08 CEST 2009

Hello everybody,

is it possible to use a characteristic function of the form

Iee [domainTot] = ($X^2 + $Y^2 <1 ) ? 1 : 0;

in the Galerkin term to integrate over an inner domain? I want to use
something like

Galerkin { [ Iee[]*({u}-{ud}), {p} ]; In domainTot;
	Jacobian Vol; Integration GradGrad; }

where domainTot is the whole domain and the integral should be
calculated over the unit circle.

I always get the "Null right hand side of linear system"-remark.
However, if I plot the function Iee[]*( u - ud ) in gmsh after
postprocessing, it is indeed zero outside, but it is certainly not zero
inside the unit circle. How can I solve this problem?

Thank you,

Stephane Durand
Department of Mathematical analysis
Research group of Numerical Functional Analysis and Mathematical
Ghent University

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