complex propagation constant in VectorHelmholtzSolver

Numerical methods and mathematical models of Elmer
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Vowa
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Joined: 07 Feb 2017, 04:10
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complex propagation constant in VectorHelmholtzSolver

Post by Vowa »

Hi ElmerFEM community,

I'm trying to implement a port feed and absorbing boundary conditions for a propagating wave with a complex propagation constant in the VectorHelmholtzSolver module.

I've studied the manual as well as the tutorial, but I'm still not sure how to implement an electric field with the form of exp(gamma*z) with the propagation constant gamma given as gamma = alpha + i beta.

Can someone please explain how I would have to define the Magnetic Boundary Load and Electric Robin Coefficient in this case?

Thanks!
stroop
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Joined: 22 Nov 2016, 17:26
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Location: Germany

Re: complex propagation constant in VectorHelmholtzSolver

Post by stroop »

Hey,
this is what I did but I'm no 100% sure it is right, so if anyone sees a mistake please correct me.

For the wall I applied the Leontovich impedance boundary condition because since beta is complex it meants that the signal attentuates so the electric feild can't be zero.
I followed what was in the models manual so,

Electric Robin coeffcient = real part of -i*mu*Zp^-1
Electric Robin coeffcient = imag part of -i*mu*Zp^-1

Inport - Port feed boundary condition

Electric Robin coeffcient = -1* imaginary pat of beta
Electric Robin coeffcient im = real part of beta

Magnetic boundary load = real part of 2*i*beta*Ep
Magnetic boundary load = imag part of 2*i*beta*Ep

Outport - absorbing boundary condition

Electric Robin coeffcient im = w*sqrt(e_0*mu_0)
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