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Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

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scattering from a gold sphere in 4.2

Posted 2011年7月29日 GMT-4 03:42 Plasma Physics, RF & Microwave Engineering, Heat Transfer & Phase Change, Materials, Mesh, Modeling Tools & Definitions, Parameters, Variables, & Functions, Studies & Solvers Version 3.5a, Version 4.2 5 Replies

Anupam Ghosh
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I am trying to re run the scattering program (for single wavelength) in 4.2 which is available in model gallery in 3.5a version:-

www.comsol.com/showroom/documentation/model/3459/

I have written a similar program in 4.2 but it shows errors:-
1>error1: in compiling equations
2>error2 : it asks to put triangular mesh at the boundaries , once i switch to physics controlled mesh ,then
3>error3 : duplicate variable name : c_const , then when i remove it from the parameter declaration ,then
4>error4 : failed to evaluate variable "mod1.emw.E0x" [most probably at the perfect electric conductor boundary] n a subsequent expression.

i m new to comsol n i cannot figure out the source of error and how to troubleshoot it.I have attached the model with this post, if someone can help then that will be gr8.

Attachments:

5 Replies Last Post 2011年10月11日 GMT-4 18:30
Xingang Ren
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Posted: 1 decade ago 2011年8月8日 GMT-4 12:18
CAN YOU SEND ME THE GOLD_LIB.XML!
THANK YOU !
CAN YOU SEND ME THE GOLD_LIB.XML! THANK YOU !
Anupam Ghosh
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Posted: 1 decade ago 2011年8月8日 GMT-4 12:25
I am solving it for single wavelength - i specified the n,k value accordingly in the model.
I am solving it for single wavelength - i specified the n,k value accordingly in the model.
Alejandro Rodriguez Perez
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Posted: 1 decade ago 2011年9月10日 GMT-4 23:34
I had the same issue. Change the scattering boundary condition from spherical to plane wave. It is not optimal but since your PML will absorve all the scattered field, you will be fine. For more, look at this tutorial:
www.youtube.com/watch?v=fXm1GKXDXM0

Hope it helps
I had the same issue. Change the scattering boundary condition from spherical to plane wave. It is not optimal but since your PML will absorve all the scattered field, you will be fine. For more, look at this tutorial: http://www.youtube.com/watch?v=fXm1GKXDXM0 Hope it helps
Anupam Ghosh
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Posted: 1 decade ago 2011年9月12日 GMT-4 05:54
Thanks Alejandro, the link is really helpful.
Thanks Alejandro, the link is really helpful.
Anupam Ghosh
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Posted: 1 decade ago 2011年10月11日 GMT-4 18:30
Hi Alejandro,

For the same configuration as yours (i.e.radius of : scatterer = 15nm,inner pml=90nm;outer pml=120nm) .
When I place an auxiliary boundary (for defining Efar) between scatterer and inner pml and then do the calculation (as done in 3.5 version of mie scattering ) to calculate - rcs and scattering cross section ;then the results dont match with Mie code but the absorption cross section being calculated as a function of resistive losses at the scatterer turns out to be quite fine.

3.5 version uses the integration coupling , where as in 4.2 model example of rcs calculation for Al boat is done using extrusion coupling.I did the simulation using your configuration and integration coupling as described in 3.5 to calculate far field quantities - rcs, scattering cross section and scattered power but they are incorrect.How come absorpton cross section is right and scattering cross section is messed up - this is not allowing me to calculate the quantity of interest - extinction cross section.

Basically - how do we calculate the radar cross section and the scattering cross section in 4.2 ? I tried the 3.5 way of doing it but as mentioned above the results dont match for far field calculations.If you can suggest a solution then it will be great.I have attached one of the models in case you want to have a look.


Thank you,
Anupam.
Hi Alejandro, For the same configuration as yours (i.e.radius of : scatterer = 15nm,inner pml=90nm;outer pml=120nm) . When I place an auxiliary boundary (for defining Efar) between scatterer and inner pml and then do the calculation (as done in 3.5 version of mie scattering ) to calculate - rcs and scattering cross section ;then the results dont match with Mie code but the absorption cross section being calculated as a function of resistive losses at the scatterer turns out to be quite fine. 3.5 version uses the integration coupling , where as in 4.2 model example of rcs calculation for Al boat is done using extrusion coupling.I did the simulation using your configuration and integration coupling as described in 3.5 to calculate far field quantities - rcs, scattering cross section and scattered power but they are incorrect.How come absorpton cross section is right and scattering cross section is messed up - this is not allowing me to calculate the quantity of interest - extinction cross section. Basically - how do we calculate the radar cross section and the scattering cross section in 4.2 ? I tried the 3.5 way of doing it but as mentioned above the results dont match for far field calculations.If you can suggest a solution then it will be great.I have attached one of the models in case you want to have a look. Thank you, Anupam.

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