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Definition of normal vector of the boundaries in COMSOL
Posted Sep 3, 2010, 11:29 a.m. EDT 3 Replies
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Hello, everyone,
When I did powerflow integration on some boundary, the sign of the outflow is positive or negative which can not be explained by myself.
The outflow power defined (eg. in RF) : nPo_rfw=nx_rfw*Pox_rfw+ny_rfw*Poy_rfw+nz_rfw*Poz_rfw. It is defined as the scalar product of the power flow and the normal vector to the boundary.
However, I am totally confused about the definition of the normal vector of a plane boundary in COMSOL.
For example , an plane x=-0.1, the normal vector should be [1 0 0],right?
If it is like that, can you explain me eg. in the library model: waveguide_hbend_3d
The normal vector of boundary 1 is [1 0 0] or [-1 0 0], why the outflow power on boundary 1 is negative?
How can I plot normal vector nx_rfw, ny_rfw, nz_rfw inside GUI?
I want to check the sign of the normal vector. If I type this directly in the plot parameter, It does not show the value.
Can anyone explain me a little bit?
When I did powerflow integration on some boundary, the sign of the outflow is positive or negative which can not be explained by myself.
The outflow power defined (eg. in RF) : nPo_rfw=nx_rfw*Pox_rfw+ny_rfw*Poy_rfw+nz_rfw*Poz_rfw. It is defined as the scalar product of the power flow and the normal vector to the boundary.
However, I am totally confused about the definition of the normal vector of a plane boundary in COMSOL.
For example , an plane x=-0.1, the normal vector should be [1 0 0],right?
If it is like that, can you explain me eg. in the library model: waveguide_hbend_3d
The normal vector of boundary 1 is [1 0 0] or [-1 0 0], why the outflow power on boundary 1 is negative?
How can I plot normal vector nx_rfw, ny_rfw, nz_rfw inside GUI?
I want to check the sign of the normal vector. If I type this directly in the plot parameter, It does not show the value.
Can anyone explain me a little bit?
3 Replies Last Post Sep 6, 2010, 4:59 a.m. EDT
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Posted:
1 decade ago
Hi,
Regarding plot of the normal vectors, you can try to use boundary plot instead of subdomain plot.
Wei
Regarding plot of the normal vectors, you can try to use boundary plot instead of subdomain plot.
Wei
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Posted:
1 decade ago
Hi
the normal direction are defined wrt the body/domain, it points normally "outward" from a closed volume ("up") and if you define a plane you need to say where is the geoemtrical entity of higher value (volume for a plane, surface for an edge, but a point has a singularity w.r.t normal ;) to define the outward ("up") direction ofthe normal.
Just a plane has two directions for a normal, they are opposite, you need to define a sign convention, in Comsol its normally + is outward away from the closed body
But indeed use the arrow plots to see, visualise nx,ny.nz or any other vector
Hope this helps
--
Good luck
Ivar
the normal direction are defined wrt the body/domain, it points normally "outward" from a closed volume ("up") and if you define a plane you need to say where is the geoemtrical entity of higher value (volume for a plane, surface for an edge, but a point has a singularity w.r.t normal ;) to define the outward ("up") direction ofthe normal.
Just a plane has two directions for a normal, they are opposite, you need to define a sign convention, in Comsol its normally + is outward away from the closed body
But indeed use the arrow plots to see, visualise nx,ny.nz or any other vector
Hope this helps
--
Good luck
Ivar
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Posted:
1 decade ago
Thank you for your reply! I understand now.