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Scaling direction parameter in PML node

Posted Jan 19, 2011, 11:14 a.m. EST RF & Microwave Engineering Version 4.1, Version 4.2 5 Replies

Jaroslav Luksch
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Hello everyone,
I have a problem with PML. I don't fully understand one parameter and that's Scaling direction. It is located in the Manual scaling sub-node which is located in the PML node if the type of PML is set to General. In the RF module manual is written "The first parameter" (Scaling direction) "sets the direction from the interface to the outer boundary." From this
sentence I would understand this parameter can take the value of 0,1 or -1. But I know from Comsol this parameter can take any real number. And here is my misunderstanding. Which direction does this parameter scale? Is it the real direction or the imaginary direction or both of them? I eliminate the last possibility by myself because both directions should be scaled by the PML scaling factor from the PML node if I correctly understand the equation (2-1) from the RF module manual, page 29.
Jaroslav Luksch
5 Replies Last Post Sep 6, 2011, 2:17 a.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jan 19, 2011, 4:03 p.m. EST
Hi

I generally leave the default values for the PML, just checking the shape linear, cylindrical or spherical, but I would too need to look into the doc to give a reasonnable reply

--
Good luck
Ivar
Hi I generally leave the default values for the PML, just checking the shape linear, cylindrical or spherical, but I would too need to look into the doc to give a reasonnable reply -- Good luck Ivar
Olav Gaute Hellesø
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Posted: 1 decade ago Aug 24, 2011, 4:37 a.m. EDT
I have the same problem, so an answer to this would be most appreciated. My model is a waveguide which is terminated by a cartesian PML, while for the surrounding evanescent field, a general PML seems to be necessary.
I have the same problem, so an answer to this would be most appreciated. My model is a waveguide which is terminated by a cartesian PML, while for the surrounding evanescent field, a general PML seems to be necessary.
Jaroslav Luksch
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Posted: 1 decade ago Aug 31, 2011, 11:35 a.m. EDT
Hi Olav,
I've solved my problems so I believe I can give you an advice. If your computing window is rectangular or cuboidal I'm deeply convinced the cartesian PML will be the right stuff for you. The general PML is useful for example if your computing window is triangular or if you know the wave propagation direction in advance and that direction differs from cartesian coordinates indeed.
Hi Olav, I've solved my problems so I believe I can give you an advice. If your computing window is rectangular or cuboidal I'm deeply convinced the cartesian PML will be the right stuff for you. The general PML is useful for example if your computing window is triangular or if you know the wave propagation direction in advance and that direction differs from cartesian coordinates indeed.
Olav Gaute Hellesø
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Posted: 1 decade ago Sep 5, 2011, 6:59 a.m. EDT
Hi Jaroslav,
In my case the solution was to use General PML, insert Manual scaling and set "Geometric width" to the wavelength in the material. Also, Scaling direction was set to the propagation direction only.
Hi Jaroslav, In my case the solution was to use General PML, insert Manual scaling and set "Geometric width" to the wavelength in the material. Also, Scaling direction was set to the propagation direction only.
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Sep 6, 2011, 2:17 a.m. EDT
Hei Olav

anoher point, not sure it's related. But I often use spherical shapes for my PMLs, thenI must not only chec to use "spherical" coordinates in the PML node, BUT ALSO correctly put the senter at the centre of the sphere, which is not alsways at the default 0,0,0. This applies probably also to the other shapes.

Where I'm not yet confident myself, is how to best generate "onion-peel" mesh elements (partcularly for the sphere case) for the PMLs as that seems more appropriate for such domains

--
Good luck
Ivar
Hei Olav anoher point, not sure it's related. But I often use spherical shapes for my PMLs, thenI must not only chec to use "spherical" coordinates in the PML node, BUT ALSO correctly put the senter at the centre of the sphere, which is not alsways at the default 0,0,0. This applies probably also to the other shapes. Where I'm not yet confident myself, is how to best generate "onion-peel" mesh elements (partcularly for the sphere case) for the PMLs as that seems more appropriate for such domains -- Good luck Ivar

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