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surface area of inclined disc at interface

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Hi there,

I want to calculate surface area of a circular disc on each side of the interface. The interface is very thin and disc rotates around the interface from vertical to horizontal direction (0 to 90 deg). The surface area on one side of interface will change with the change in angle of rotation.
How can i do it.
I have build circular geometry. i want to define the interface and angle of rotation.


Thanks

Raj


1 Reply Last Post 02.06.2010, 02:04 GMT-4
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 02.06.2010, 02:04 GMT-4
Hi

normally a surface intergation is a boundary coupling variable (or a postprocessing boundary integration) with the integran value of "1", in 2D axi, its a line integration of 2*pi*r (in 3.5, pls check in 4.0 normally the 2*pi is already included) in 2D axi for some GUI you have the tick box to automatically include the 2*pi*r. In 2D an area is again an edge integration but of the depth or thickness "d" along Z that by default is mostly 1[m], you can check this by studying the units that COMSOL proposes.

Furthermore, to do a postprocessing integration (what I use to check my formulas) you need to fill in all matrices for the calcuations, as these integrations are done on the meshed volumes, to get this in 3.5 do a Solve - Get initial value before you launch a postprocessing boundary integration.

Try it out on a simple geometry (rectangle, circle ...) until you feel comfortable with the notations

And last consideration: check the "frame" on which you integrate, this depends on the application mode you are using such as ALE with "ref" frame. In V4 there are new names such as : mesh, material and stationary, check the doc

Have fun Comsoling
Ivar
Hi normally a surface intergation is a boundary coupling variable (or a postprocessing boundary integration) with the integran value of "1", in 2D axi, its a line integration of 2*pi*r (in 3.5, pls check in 4.0 normally the 2*pi is already included) in 2D axi for some GUI you have the tick box to automatically include the 2*pi*r. In 2D an area is again an edge integration but of the depth or thickness "d" along Z that by default is mostly 1[m], you can check this by studying the units that COMSOL proposes. Furthermore, to do a postprocessing integration (what I use to check my formulas) you need to fill in all matrices for the calcuations, as these integrations are done on the meshed volumes, to get this in 3.5 do a Solve - Get initial value before you launch a postprocessing boundary integration. Try it out on a simple geometry (rectangle, circle ...) until you feel comfortable with the notations And last consideration: check the "frame" on which you integrate, this depends on the application mode you are using such as ALE with "ref" frame. In V4 there are new names such as : mesh, material and stationary, check the doc Have fun Comsoling Ivar

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