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-   -   about the top of the mixing tank (http://www.cfd-online.com/Forums/fluent/79250-about-top-mixing-tank.html)

boh_tea August 18, 2010 02:43

about the top of the mixing tank
 
Hi all,

Is it possible to make the top of a stirred tank become a free surface such as in the real life mixing condition where on top of the mixing fluid is air?Is it possible to achieve that by setting velocity gradient or pressure gradient of the top to 0?Or can i patch a air region to the top of the tank (without VOF model)?Or reconstruct the geometry with 1 region of fluid(air) above the fluid(mixing fluid) would do?

Thanks!

xrs333 August 18, 2010 03:54

Hi, boh_tea,
if you arrive at that goal, you get some like VOF.

boh_tea August 18, 2010 05:52

Hi xrs333,

does that mean that in order to do that ,I have to use VOF model?

xrs333 August 18, 2010 07:01

yes, you have to use models that can track phase interface, and among several models of this category only VOF is integrated in Fluent .

boh_tea August 18, 2010 07:58

Is making a volume above the stationary fluid volume in gambit which use to define with air will give similar result besides of using vof?Is this workable?

Thanks for replying.

xrs333 August 18, 2010 08:26

Are you sure that the shape of the free surface is unfluctuating, or calm. If so it is, you may cautiously use wall boundary condition with zero shear stress to model the free surface.

boh_tea August 18, 2010 11:47

No,the top surface should be in parabolic shape according to what my lecturer told me.What I mean is that constructing one more volume above the stirred tank,as i am using MRF approach,so it is above the stationary fluid region.

For setting the wall to zero shear stress,is it done by changing the wall condition from no slip to shear condition while its pressure is set to 0?

boh_tea August 21, 2010 03:58

Any idea how to set the top wall into free slip condition?Is there a way to do so?


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