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Polar plots

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Hi,

I want to run a COMSOL in order to find the velocity inside a tube. I used 2D axisymmetric and found the velocity in r and z direction. However, I need to find velocity in r and theta direction for the entire range of r and theta. I think I need the polar plot group but I don't know how should I used it. I will really appreciate your help.

Thanks

Negin

4 Replies Last Post Jun 27, 2012, 4:47 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 Jun 26, 2012, 2:59 p.m. EDT
Hi

if its the third 2D-axi coordinate its "phi" (and not theta), but a 2D-axi is indepedent of "phi" so normally it's value are all 0. Els I believe you must go in 3D to get all three vector components, the you define either a cylindrical coordinate, or a psherical, or use somethin like an r=sqrt(x^2+y^2) and atan2(v,u) for a phi in the X-Y plane

--
Good luck
Ivar
Hi if its the third 2D-axi coordinate its "phi" (and not theta), but a 2D-axi is indepedent of "phi" so normally it's value are all 0. Els I believe you must go in 3D to get all three vector components, the you define either a cylindrical coordinate, or a psherical, or use somethin like an r=sqrt(x^2+y^2) and atan2(v,u) for a phi in the X-Y plane -- Good luck Ivar

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Posted: 1 decade ago Jun 27, 2012, 1:31 p.m. EDT
Hi,
Thanks for your response. Actually it is a 2D which has only r and theta( no Phi is needed). I want to create my results in a plot which itsaxis are r and theta. So as you said Phi is zero. Just r and theta is needed. I did the exact same thing with MATLAB (r,theta) and plot my velocities in polar coordinates and I want to compare my results with COMSOL, in order to get the exact same results from both of them.
Thanks,
Negin
Hi, Thanks for your response. Actually it is a 2D which has only r and theta( no Phi is needed). I want to create my results in a plot which itsaxis are r and theta. So as you said Phi is zero. Just r and theta is needed. I did the exact same thing with MATLAB (r,theta) and plot my velocities in polar coordinates and I want to compare my results with COMSOL, in order to get the exact same results from both of them. Thanks, Negin

Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago Jun 27, 2012, 2:11 p.m. EDT
Hi

OK I didnt cat it then, in 2D COMSOL is by default in the cartesian coordinates (x,y) but you can easily set up a cylindrical coordinate (r, theta) with coresponds to r=sqrt((x-x0)^2+(y-Y0)^2) and theta = atan2(y,x).
Either you define the two variables, or you add a cylidrical coordinate "sys2" and you access sys2.r and sys2.theta (I have a doubt about the second name pls check, I'm not by my WS ;)

Then you can generate your polar plot with r and theta (your vaiables), or the default sys2 references

--
Good luck
Ivar
Hi OK I didnt cat it then, in 2D COMSOL is by default in the cartesian coordinates (x,y) but you can easily set up a cylindrical coordinate (r, theta) with coresponds to r=sqrt((x-x0)^2+(y-Y0)^2) and theta = atan2(y,x). Either you define the two variables, or you add a cylidrical coordinate "sys2" and you access sys2.r and sys2.theta (I have a doubt about the second name pls check, I'm not by my WS ;) Then you can generate your polar plot with r and theta (your vaiables), or the default sys2 references -- Good luck Ivar

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Posted: 1 decade ago Jun 27, 2012, 4:47 p.m. EDT
Thanks for your answer

Negin
Thanks for your answer Negin

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