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-   -   Magnetic stiring in a glass (http://www.cfd-online.com/Forums/cd-adapco/52372-magnetic-stiring-glass.html)

Bo Jensen March 7, 2000 13:51

Magnetic stiring in a glass
 
Hi!

I have just started modelling a glass with a fluid that is moved by a little magnet rod located on the bottom of this glass. The magnet is moved by a magnetic field from a surface placed below the glass. Now, it there anybody who has any sugestions to how this can be done??

What I have tried untill now is just to say that a area in the the centre of the flow domain (at the bottom) is removed from the geometry (Area is corresponding to the area that would have been occupied by the magnet rod during one revolution). Then I have put on a rotational velocity on the walls of the "rod" area. But is that true....

Regards

Bo

philip March 13, 2000 04:42

Re: Magnetic stiring in a glass
 
Bo,

When using STAR-CD and moving domains one must clearly differentiate between wall motion normal and tangential to the fluid.

If the wall motion is normal to the fluid then it pushes the fluid with it.

If the wall motion is tangential to the fluid then its influence is only felt in via shear force.

If you apply a rotational velocity on the walls of the "rod" area then you are only adding the shear force, not any of the normal component of the wall moving.

To model the normal component you need to use either rotating reference frames or full moving mesh. If this is one of these little lozenge mixers seen in labs etc then the assumptions for rotating references frames are inappropriate for this.

The full moving mesh may seem a little daunting but within Prostar there is are commands MIXVES and MIXASI that set up and run such cases in a single command

Regards

Philip


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