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Calculation of Area over a boundary

Posted 3 nov. 2015, 23:45 UTC−5 Fluid & Heat Version 4.3 4 Replies

Ravi Kumar Garikina
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How to calculate the area over a given boundary (a circle in 2D axisymmetric) in comsol 4.3?
I am using 'Intop()' to calculate the area with '1' in the brackets. Is this way of calculating the area is correct? If this is okay, what will be the units of my output.
Can anyone help me out with this.
4 Replies Last Post 5 nov. 2015, 00:40 UTC−5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 10 years ago 4 nov. 2015, 02:04 UTC−5
Hi

into1(1) means integrate over the entity (domain, boundary, edge or point) the value 1*dx*dy*dz. This is the definition of a Volume, surface, length, respectively count of points. So this is indeed the correct way to get the area (to the precision of the mesh and its discretization, try it out on a circle and reconstruct "pi")

--
Good luck
Ivar
Hi into1(1) means integrate over the entity (domain, boundary, edge or point) the value 1*dx*dy*dz. This is the definition of a Volume, surface, length, respectively count of points. So this is indeed the correct way to get the area (to the precision of the mesh and its discretization, try it out on a circle and reconstruct "pi") -- Good luck Ivar
Ravi Kumar Garikina
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Posted: 10 years ago 4 nov. 2015, 11:06 UTC−5
Thanks Ivar.

But, when I am entering intop(1) over the surface of a sphere in 2D axisymmetric, the units of length (meter) are being displayed.
Thanks Ivar. But, when I am entering intop(1) over the surface of a sphere in 2D axisymmetric, the units of length (meter) are being displayed.
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 10 years ago 4 nov. 2015, 12:54 UTC−5
Hi

Indeed in 2D-axi (and 1D-axi, but no longer in 2D nor 1D where you must multiply by the depth respectively the Area manually) a point is in fact a line (hop) around 2*pi*r, therefore there is an additional tick box in the integration tab, stating "Compute integral in revolved geometry" which adds a 2*pi*r[m] to the integration and the "r(r,z) is taken from the point coordinates.

For the Results Derived Values (no Point integration there !) the tick is called "Compute Surface Integral" or "Compute Volume integral"

then you get the right units and value ;)

Always check the units it will tell you if you are missing a dimension.

--
Good luck
Ivar
Hi Indeed in 2D-axi (and 1D-axi, but no longer in 2D nor 1D where you must multiply by the depth respectively the Area manually) a point is in fact a line (hop) around 2*pi*r, therefore there is an additional tick box in the integration tab, stating "Compute integral in revolved geometry" which adds a 2*pi*r[m] to the integration and the "r(r,z) is taken from the point coordinates. For the Results Derived Values (no Point integration there !) the tick is called "Compute Surface Integral" or "Compute Volume integral" then you get the right units and value ;) Always check the units it will tell you if you are missing a dimension. -- Good luck Ivar
Ravi Kumar Garikina
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Posted: 10 years ago 5 nov. 2015, 00:40 UTC−5
Thanks a lot sir.
Thanks a lot sir.

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