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Inclined cylinder, countercurrent-multiphase flow

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Old   July 23, 2013, 12:46
Default Inclined cylinder, countercurrent-multiphase flow
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Ravi Agrawal
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Hi, I am working on a problem with countercurrent multiphase flow in an inclined cylinder.(Using air and sand). Sand enters from elevated side in a way that interface line makes 90 degree angle at centre of the circular inlet section. Both air and sand have constant mass flow rates as their respective inlet conditions and other properties.
In figure attached, face 5 is the interface. Sand is below this face and air on above. So far both inner circular face and arc face are disconnected. What more needs to be done here(except meshing,inclination and zone assignement). OR I shouldnt make sand zone at all? If its OK here then how to active those interfaces.
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Old   July 25, 2013, 14:55
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Please check my settings in VOF model :

unsteady, implicit, implicit body force,none is selected in phase interaction.

It is a counter current flow, so air inlet is sand outlet and vice-versa. I know the inlet mass flow rates for both. Air-inlet and sand-inlet are at two opposite sides of cylinder, but sand outflow and air outflow rate are also to be specified at respectively both the sides, which I dont know at priori.

I have initialized it using 'compute from all zones'. Do I have to do patching for sand phase zone. Why is it important to do?
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Old   July 26, 2013, 01:13
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I would suggest you to check this tutorial: http://aerojet.engr.ucdavis.edu/flue...tg/node255.htm
You aren't suppose to set the vof for pressure outlet for instance.
But you need this set up for inlet.
In your case, if you splitted your cylinder with your "interface", then your cylinder caps are also splitted. One will be used for sand and the other for air.
That means you have 2 inlets BC and 2 outlets BC.
If you also defined 2 separated fluid domains, then you patch them for initialization: At t=0, you have sand below your interface and air above
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Old   July 26, 2013, 15:17
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I splitted it as there is only one face which solver considered as interior. Cylinder caps are splitted and I have separate inlets and outlets for air and sand at opposite ends. (I defined them as two different fluid domains)

In image I have shown only inlets, outlets and interface for clarity. Air flows from left to right and sand, right to left. Air starts flowing above while sand, below the interface at t=0.
I used mass flow inlets for inlets and pressure outlets for outlets.

I can specify the air and sand flow rates at their respective inlets, but at the same respective locations, sand and air flow rates are also asked to specify, which are unknown.
Back FLow temperature values are asked with pressure outlet conditions, which I am not sure about. Should I use outflow conditions then. I am looking at the tutorial, pressure outlet is used there too.
I had another confusion on inclination. Will it be taken into account bu just specifying gravity components or direction vectors needs to be changed at inlets.

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Old   July 31, 2013, 00:56
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Quote:
Originally Posted by abc197 View Post
I can specify the air and sand flow rates at their respective inlets, but at the same respective locations, sand and air flow rates are also asked to specify, which are unknown.
i didn't understand
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Old   July 31, 2013, 01:49
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I know the inlet mass flow rates or velocities for air and sand. At Air-inlet, for each phase it asks for mass flow rate, for air-phase I can specify, but for sand phase, I have nothing to specify, sand inlet is on opposite side, below the interface. Similarly, at solid inlet, I cant specify flow rate for air.
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Old   July 31, 2013, 02:00
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ok, I see.
I am now completely out of my skills.
Maybe you should consider working with DPM instead of VOF (but I don't have any experience)
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Old   July 31, 2013, 02:12
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Originally Posted by -mAx- View Post
ok, I see.
I am now completely out of my skills.
Maybe you should consider working with DPM instead of VOF (but I don't have any experience)
However I did manage to make the proper geometry. I will consider DPM or granular flow to solve this problem. Thanks for your guidelines so far. It hasbeen of great help.
Regards.
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Old   July 31, 2013, 03:01
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Actually this problem is almost same as this one, with a simplification that there is no small cylinder.
Rotating Cylinder Full of Fluid
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