I would like to simulate the EM scattering of a sphere of about the same dimensions of the wavelength. After checked the test cases and in particular the waveguide example, I need to make some changes that I'm not sure how to implement:
The wavefront has to be plane
It shouldn't be any scattering coming from the boundaries
Any suggestions would be great and very useful for more complex simulations that I would have to implement in the future
Thank you to send me at the other post which has been helpful for elaborate my understanding of the Elmer. However, I'm still struggling with my problem. I would like that the boundaries behave as transparent for the incoming plane wave. From my simulation it seems that most of the incoming wave is absorbed even before getting to the sphere as in my attachment below.
Header
CHECK KEYWORDS Warn
Mesh DB "." "."
Include Path ""
Results Directory ""
End
Simulation
Max Output Level = 5
Coordinate System = Cartesian
Coordinate Mapping(3) = 1 2 3
Simulation Type = Steady state
Steady State Max Iterations = 1
Output Intervals(1) = 1
Coordinate Scaling = 1e-6
Solver Input File = case.sif
Post File = case.vtu
End
Constants
Gravity(4) = 0 -1 0 9.82
Stefan Boltzmann = 5.670374419e-08
Permittivity of Vacuum = 8.85418781e-12
Permeability of Vacuum = 1.25663706e-6
Boltzmann Constant = 1.380649e-23
Unit Charge = 1.6021766e-19
End
Body 1
Target Bodies(1) = 1
Name = "Body 1"
Equation = 1
Material = 2
End
Body 2
Target Bodies(1) = 2
Name = "Body 2"
Equation = 1
Material = 1
End
Solver 3
Equation = Result Output
Output Format = Vtu
Procedure = "ResultOutputSolve" "ResultOutputSolver"
Save Geometry Ids = True
Output File Name = case
Exec Solver = Always
End
Solver 1
Equation = Vector Helmholtz Equation
Procedure = "VectorHelmholtz" "VectorHelmholtzSolver"
Quadratic Approximation = True
Linear System Preconditioning Damp Coefficient im = 1.0
Variable = E[E re:1 E:1]
Exec Solver = Always
Stabilize = True
Optimize Bandwidth = True
Steady State Convergence Tolerance = 1.0e-5
Nonlinear System Convergence Tolerance = 1.0e-7
Nonlinear System Max Iterations = 20
Nonlinear System Newton After Iterations = 3
Nonlinear System Newton After Tolerance = 1.0e-3
Nonlinear System Relaxation Factor = 1
Linear System Solver = Iterative
Linear System Iterative Method = BiCGStabl
Linear System Max Iterations = 500
Linear System Convergence Tolerance = 1.0e-6
BiCGstabl polynomial degree = 6
Linear System Preconditioning = vanka
Linear System ILUT Tolerance = 1.0e-3
Linear System Abort Not Converged = False
Linear System Residual Output = 10
Linear System Precondition Recompute = 1
End
Solver 2
Equation = Vector Helmholtz Post Process
Field Variable = E
Procedure = "VectorHelmholtz" "VectorHelmholtzCalcFields"
Calculate Electric Field = True
Calculate Div of Poynting Vector = True
Calculate Poynting Vector = True
Calculate Magnetic Field Strength = True
Calculate Magnetic Flux Density = True
Exec Solver = Always
Stabilize = True
Optimize Bandwidth = True
Steady State Convergence Tolerance = 1.0e-5
Nonlinear System Convergence Tolerance = 1.0e-7
Nonlinear System Max Iterations = 20
Nonlinear System Newton After Iterations = 3
Nonlinear System Newton After Tolerance = 1.0e-3
Nonlinear System Relaxation Factor = 1
Linear System Solver = Iterative
Linear System Iterative Method = BiCGStabl
Linear System Max Iterations = 500
Linear System Convergence Tolerance = 1.0e-6
BiCGstabl polynomial degree = 6
Linear System Preconditioning = vanka
Linear System ILUT Tolerance = 1.0e-3
Linear System Abort Not Converged = False
Linear System Residual Output = 10
Linear System Precondition Recompute = 1
End
Equation 1
Name = "Equation 1"
Angular Frequency = $ 2*pi*10e14
$ omega = 2*pi*10e14
$ kc= omega/(3e8)
Active Solvers(3) = 3 1 2
End
Material 1
Name = "Air"
Relative Permittivity = 1
End
Material 2
Name = "Metal"
Relative Permittivity = Real -4000
End
Boundary Condition 1
Target Boundaries(4) = 2 3 5 6
Name = "PEC"
Electric Robin Coefficient im = $ kc
Electric Robin Coefficient = $ kc
End
Boundary Condition 2
Target Boundaries(1) = 1
Name = "inport"
Electric Robin Coefficient im = $ kc
Magnetic Boundary Load 2 = Variable "Coordinate 1"; REAL MATC "cos(kc*tx)"
End
Boundary Condition 3
Target Boundaries(1) = 7
Name = "outport"
Electric Robin Coefficient im = $ kc
End
Maybe you could share the full case somewhere. One critical thing is that you have ~>10 elements for each wave. Otherwise you cannot capture the solution. This makes FEM quite heavy for large wave numbers.
For outlet you can use "Absorbing BC = True" that automatically sets appropriate impedance so that wave will not reflect.