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Calculating volume

Posted Apr 27, 2012, 11:38 a.m. EDT Mesh, Parameters, Variables, & Functions, Studies & Solvers Version 4.2a 7 Replies

Sushant Agarwal
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Hello:

How do I calculate volume of an object in COMSOL?
Please see attached file for a simple example.
I have a sphere which I expand using ALE. I want to know the volume change, i.e., volume at the beginning and volume after expansion.
Thanks
sushant

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7 Replies Last Post Aug 28, 2012, 9:48 p.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Apr 27, 2012, 4:46 p.m. EDT
Hi

I'm not behind my WS so I cannot "take a look".
But in all generality the volume is simple the integration over the domain of the operand "1". Now you must choose the correct reference frame (depends also on which physics) to get the volume before / after some changes

In 2D the volume is the surface integration * depth (often called "d", sometimes simply normalised to 1[m] all physcs dependent), and in 2D-axi one must integrate 2*pi*r (the loop length) over a domain = area to get the final full volume

--
Good luck
Ivar
Hi I'm not behind my WS so I cannot "take a look". But in all generality the volume is simple the integration over the domain of the operand "1". Now you must choose the correct reference frame (depends also on which physics) to get the volume before / after some changes In 2D the volume is the surface integration * depth (often called "d", sometimes simply normalised to 1[m] all physcs dependent), and in 2D-axi one must integrate 2*pi*r (the loop length) over a domain = area to get the final full volume -- Good luck Ivar
Abbie
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Posted: 1 decade ago Aug 27, 2012, 4:25 a.m. EDT
Hi,

If i have a 2D geometry in half ellipse (attached .jpg), and I wish to calculate its volume (revolving volume: become half prolate ellipsoid), how can I calculate the "revolving" volume of the 2D geometry in COMSOL?

I tried to calculate using surface integration*depth (1[m]), but it does not give the expected volume, i guess it is because the "depth" indicates an extrusion rather than revolving?

(Due to some reasons, I have to use 2D geometry rather than 2D axisymmetric.)

Thanks.
Hi, If i have a 2D geometry in half ellipse (attached .jpg), and I wish to calculate its volume (revolving volume: become half prolate ellipsoid), how can I calculate the "revolving" volume of the 2D geometry in COMSOL? I tried to calculate using surface integration*depth (1[m]), but it does not give the expected volume, i guess it is because the "depth" indicates an extrusion rather than revolving? (Due to some reasons, I have to use 2D geometry rather than 2D axisymmetric.) Thanks.

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Alexander Kuznetsov
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Posted: 1 decade ago Aug 27, 2012, 2:17 p.m. EDT

I tried to calculate using surface integration*depth (1[m])


use volume integration instead
[QUOTE] I tried to calculate using surface integration*depth (1[m]) [/QUOTE] use volume integration instead
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Aug 27, 2012, 4:02 p.m. EDT
Hi

if you want an ellisoid, you should use 2D-axi and not 2D, then you do a surface volume on the (r>=0) part and select use revolution to obtain volume, basically it multiplies the integration operand by 2*pi*r the "loop length"

--
Good luck
Ivar
Hi if you want an ellisoid, you should use 2D-axi and not 2D, then you do a surface volume on the (r>=0) part and select use revolution to obtain volume, basically it multiplies the integration operand by 2*pi*r the "loop length" -- Good luck Ivar
Abbie
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Posted: 1 decade ago Aug 27, 2012, 9:08 p.m. EDT


use volume integration instead


Hi Alexander,

To calculate volume by selecting volume integration, data set is required, right? What data set should I create to calculate the volume of ellipsoid?


Thanks.
[QUOTE] use volume integration instead [/QUOTE] Hi Alexander, To calculate volume by selecting volume integration, data set is required, right? What data set should I create to calculate the volume of ellipsoid? Thanks.

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Abbie
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Posted: 1 decade ago Aug 27, 2012, 9:15 p.m. EDT


if you want an ellisoid, you should use 2D-axi and not 2D, then you do a surface volume on the (r>=0) part and select use revolution to obtain volume, basically it multiplies the integration operand by 2*pi*r the "loop length"




Thanks Ivar. Due to the implemented material properties is non-symmetric, so I choose 2D geometry rather than 2D axisymmetric (however the geometry is still in symmetry).

May I know is it impossible to obtain ellipsoid volume from calculation in 2D?
[QUOTE] if you want an ellisoid, you should use 2D-axi and not 2D, then you do a surface volume on the (r>=0) part and select use revolution to obtain volume, basically it multiplies the integration operand by 2*pi*r the "loop length" [/QUOTE] Thanks Ivar. Due to the implemented material properties is non-symmetric, so I choose 2D geometry rather than 2D axisymmetric (however the geometry is still in symmetry). May I know is it impossible to obtain ellipsoid volume from calculation in 2D?
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Aug 28, 2012, 9:48 p.m. EDT
Hi

but 2D implies an invariant along the depth direction (Z) and all items/variables dependent variables are expressed as per meter depth

It's not the same coordinate development and physics equations between 2D and 2D - axi.

I agree if your material property does not match the 2D-axi symmetry, then for me you have only true 3D left for your model

--
Good luck
Ivar
Hi but 2D implies an invariant along the depth direction (Z) and all items/variables dependent variables are expressed as per meter depth It's not the same coordinate development and physics equations between 2D and 2D - axi. I agree if your material property does not match the 2D-axi symmetry, then for me you have only true 3D left for your model -- Good luck Ivar

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