about the top of the mixing tank

boh_tea · August 18, 2010, 02:43

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?

August 18, 2010, 02:43	about the top of the mixing tank	#1
boh_tea New Member Ming Join Date: Jul 2010 Posts: 12 Rep Power: 15	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!

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August 18, 2010, 03:54		#2
xrs333 Senior Member xrs333 Join Date: Aug 2010 Posts: 125 Rep Power: 16	Hi, boh_tea, if you arrive at that goal, you get some like VOF.

August 18, 2010, 05:52		#3
boh_tea New Member Ming Join Date: Jul 2010 Posts: 12 Rep Power: 15	Hi xrs333, does that mean that in order to do that ,I have to use VOF model?

August 18, 2010, 07:01		#4
xrs333 Senior Member xrs333 Join Date: Aug 2010 Posts: 125 Rep Power: 16	yes, you have to use models that can track phase interface, and among several models of this category only VOF is integrated in Fluent .

August 18, 2010, 07:58		#5
boh_tea New Member Ming Join Date: Jul 2010 Posts: 12 Rep Power: 15	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.

August 18, 2010, 08:26		#6
xrs333 Senior Member xrs333 Join Date: Aug 2010 Posts: 125 Rep Power: 16	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.

August 18, 2010, 11:47		#7
boh_tea New Member Ming Join Date: Jul 2010 Posts: 12 Rep Power: 15	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?

August 21, 2010, 03:58		#8
boh_tea New Member Ming Join Date: Jul 2010 Posts: 12 Rep Power: 15	Any idea how to set the top wall into free slip condition?Is there a way to do so?