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impeller mixing

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Hello

Thanks in advance for any help. I'm just starting to learn!

I would like to model impeller mixing in a cylindrical tank. I am starting with a transient 2D model (with the idea of eventually having a 3D model), so the geometry looks like a circle with a cross on the center (the radial impeller). I want to make the "cross" rotate and then analyze the velocity profiles with time.

The density and viscosity are that of water. I am assigning free displacement on the subdomain, while moving the boundaries of the impeller with the equations:

dx = cos(-2*pi*rpm*t)*X-sin(-2*pi*rpm*t)*Y-X
dy = sin(-2*pi*rpm*t)*X+cos(-2*pi*rpm*t)*Y-Y

Meanwhile, from the fliud mechanics side, I need the walls to have a no slip condition. I have tried several alternatives but I keep getting an error message about pointwise constraints not allowed for transient analyses.

I'm very confused.

Thanks again!

2 Replies Last Post 6 juil. 2010, 14:37 UTC−4
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 30 juin 2010, 01:39 UTC−4
Hi
it not obvious from what you saying, without the model to catch what is wrong, but I believe this exist as a full mdoel description in one of the docs, or was it on one of the models on the web ?

You ahve an excellent approach to start in 2D its much easier (but still not always obvious ;), before attacking 3D

Have fun Comsoling
Ivar
Hi it not obvious from what you saying, without the model to catch what is wrong, but I believe this exist as a full mdoel description in one of the docs, or was it on one of the models on the web ? You ahve an excellent approach to start in 2D its much easier (but still not always obvious ;), before attacking 3D Have fun Comsoling Ivar

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Posted: 1 decade ago 6 juil. 2010, 14:37 UTC−4
Hello Ivar

Thank you so much for your reply. I did see a paper from one of the Comsol conferences by Grosz, 2005, where he used momentum source modeling. Is this the model you are referring to? I haven´t been able to find anything else.

Thank you,
Sylvana
Hello Ivar Thank you so much for your reply. I did see a paper from one of the Comsol conferences by Grosz, 2005, where he used momentum source modeling. Is this the model you are referring to? I haven´t been able to find anything else. Thank you, Sylvana

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