[Getdp] plane wave scattering by a sphere

[laurent bernard]

Hello,

I am trying to compute the field scattered by an homogeneous sphere exposed
to an incident  electromagnetic plane wave.
The unknown is the scattered field (electric field for example).
The source is the incident field in the volume of the sphere. (See for
example P.D.Ledger's thesis §5.3 for the variational formulation of the
problem http://www.sam.math.ethz.ch/~ledger/publication.html).
PML are used to troncate the computational domain.
Only one-quarter of the sphere is represented (taking advantage of the
symmetries).

The mesh is generated using Gmsh (netgen algorithm with optimization) (18159
elements)

Problems:
Nb_Fill must be set to 3000 in order the obtain convergence. For lower
Nb_Fill, the solver faces break-down. In consequence, the resolution is
highly RAM and time consuming. So i don't manage to solve the problem on a
finer mesh, and i can't use second order elements.
The solution shows unexpected irregularities (see attached pdf file, which
shows the components of the total electric field on a segment passing
through the sphere).

Questions:
Is there any mistake in the .pro files? In the geommetry? (see attached
files)
If not, what should i do to improve the results? to solve the problem using
less RAM?

thank you,
best regards

Laurent Bernard
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