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Applying cylindrical coordinate system in comsol

Posted Mar 23, 2023, 1:49 a.m. EDT Version 5.6 4 Replies

M Gnanasekaran
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I am studying a 3d transient model to understand the effect of combined Buoyancy-Marangoni convection in a cylindrical geometry. I want to apply the cylindrical coordinates (r, θ, a). As a solution to this, I have changed the default cartesian system (x, y,z) to cylindrical coordinates under component< definitons<cylindrical coordinates. But while postprocessing I am unable to get the resullts in (r, θ, a) coordinate systems. Eg: If we want to take the azimuthal velocity ie Vθ, in the drop down only cartisean variables are available ie Vx, Vy, Vz.

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4 Replies Last Post Mar 27, 2023, 11:19 a.m. EDT
M Gnanasekaran
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Posted: 2 years ago Mar 23, 2023, 1:50 a.m. EDT

I have attached a doc file that contains my doubts with images.Please go through it and suggest me some solutions.

Thank You

I have attached a doc file that contains my doubts with images.Please go through it and suggest me some solutions. Thank You
Henrik Sönnerlind COMSOL Employee

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Posted: 2 years ago Mar 23, 2023, 11:04 a.m. EDT

The local coordinate system in the Fluid node is only used to interpret the inputs (that is, Velocity Field and possibly a nonisotropic Thermal Conductivity).

If you want to transform the velocity into a local coordinate system, you can use the Vector Transform node, found under Definitions -> Variable Utilities.

As for your second question, it is better if you can upload your model (or a similar one).

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Henrik Sönnerlind
COMSOL
The local coordinate system in the *Fluid* node is only used to interpret the inputs (that is, *Velocity Field* and possibly a nonisotropic *Thermal Conductivity*). If you want to transform the velocity into a local coordinate system, you can use the *Vector Transform* node, found under *Definitions* -> *Variable Utilities*. As for your second question, it is better if you can upload your model (or a similar one).
M Gnanasekaran
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Posted: 2 years ago Mar 27, 2023, 1:47 a.m. EDT

Thank you for your kind suggestions.

I have used the vector transform node like you suggested. But unfortunatley I still get results in x,y,z coorinates. Can u please where I made a mistake?. I have attached the images.

Thank you for your kind suggestions. I have used the vector transform node like you suggested. But unfortunatley I still get results in x,y,z coorinates. Can u please where I made a mistake?. I have attached the images.

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Henrik Sönnerlind COMSOL Employee

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Posted: 2 years ago Mar 27, 2023, 11:19 a.m. EDT

a) You have not selected any input in Vector Transform. You should select the velocity vector there.
b) The result to be displayed is the variable created in Vector Transform; a name that you choose.

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Henrik Sönnerlind
COMSOL
a) You have not selected any input in *Vector Transform*. You should select the velocity vector there. b) The result to be displayed is the variable created in *Vector Transform*; a name that you choose.

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