Resonance with square scatterer

ajf367
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3 years 7 months ago - 3 years 7 months ago #3616 by ajf367

Resonance with square scatterer was created by ajf367

Edited: I am very new to NGSolve. I'm trying to verify some resonance values that I've solved for through collocation methods on the integral equation form for the 2D Helmholtz equation with constant value scatterer, the scatterer has value 3, so the equation looks like
[tex]\Delta u + 3 \lambda u =0[/tex]
with Sommerfeld radiation conditions.

I'm using the tutorial as well as things I've seen on other posts and have the following code:

Code:

geo = SplineGeometry()

Points = [(0,0),    (1,0),    (1,1),      (0,1)]
for pnt in Points:
    geo.AddPoint(*pnt)
for pids in [[0,1],[1,2],[2,3], [3,0]]:
    geo.Append(["line"]+pids,leftdomain=1,rightdomain=2,bc="scat")

geo.AddCircle( (0.5,0.5), 1.2, leftdomain=3, bc="outerbdn")
geo.AddCircle( (0.5,0.5), 1.0, leftdomain=2, rightdomain=3, bc="innerbdn")

geo.SetMaterial(1, "inner")
geo.SetMaterial(2, "air")
geo.SetMaterial(3, "pmlregion")
mesh = Mesh(geo.GenerateMesh(maxh=0.1))
mesh.Curve(3)

mesh.SetPML(pml.Radial(rad=1,alpha=1j,origin=(0.5,0.5)), "pmlregion") 

omega_0 = 1
omega_tilde = 3

domain_values = {'inner': omega_tilde,'air': omega_0, 'pmlregion': omega_0}
values_list = [domain_values[mat] for mat in mesh.GetMaterials()]
omega = CoefficientFunction(values_list)

Draw(omega, mesh, 'piecewise')


fes = H1(mesh, order=4, complex=True, dirichlet="dir")

u = fes.TrialFunction()
v = fes.TestFunction()

a = BilinearForm (fes, symmetric=True)
a += grad(u)*grad(v)*dx

m = BilinearForm (fes, symmetric=True)
m += u*v*dx

a.Assemble()
m.Assemble()
u = GridFunction(fes, multidim=50, name='resonances')

with TaskManager():
    lam = ArnoldiSolver(a.mat, m.mat, fes.FreeDofs(),
                        u.vecs, shift=0)
Draw(u)
print ("lam: ", lam)

If someone can let me know if this is actually solving for the resonance values with a [0,1]x[0,1] square scatterer with value 3 I would be greatly appreciative.

Last edit: 3 years 7 months ago by ajf367. Reason: Worked some code out and I think if might be better now, still unsure.

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