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Cylindrical coordinates

Posted 20 gen 2011, 18:29 GMT-5 Fluid & Heat, Interfacing, Chemical Reaction Engineering, Geometry, Parameters, Variables, & Functions Version 4.0a 2 Replies

Lu Han
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Hi,
How do you input the components of gradient operator in cylindrical coordiantes?
I understasnd in Cartesian coordinates the variables ux, uy, and uz are the components of the gradient u. How about in cylindrical coordinates?

Thanks,
Lu
2 Replies Last Post 26 gen 2011, 14:51 GMT-5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 21 gen 2011, 01:36 GMT-5
Hi
If you are in 3D you must write them out yourself, but you can use a cylindrical coordinate system (see also the KB) to help.
in 2D-axi you are already in cylindrical coordinates in some way

--
Good luck
Ivar
Hi If you are in 3D you must write them out yourself, but you can use a cylindrical coordinate system (see also the KB) to help. in 2D-axi you are already in cylindrical coordinates in some way -- Good luck Ivar
Lu Han
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Posted: 1 decade ago 26 gen 2011, 14:51 GMT-5
I am using the PDE module with 2D axial-symmetric. Specifically, how would you write the gradient or divergence of a vector in COMSOL?
For instance, say I want to take the gradient of vector f, it would be:
diff(f,r)+1/r*diff(f,theta) + diff(f,z)

and if I want to take the difference of vector g, it would be:
diff(g,r) + g/r + 1/r*diff(g,theta) + diff(g,z)

(abiding vector calculus of course)

Is that what you were pointing at?

Thank you for your help
I am using the PDE module with 2D axial-symmetric. Specifically, how would you write the gradient or divergence of a vector in COMSOL? For instance, say I want to take the gradient of vector f, it would be: diff(f,r)+1/r*diff(f,theta) + diff(f,z) and if I want to take the difference of vector g, it would be: diff(g,r) + g/r + 1/r*diff(g,theta) + diff(g,z) (abiding vector calculus of course) Is that what you were pointing at? Thank you for your help

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