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two velocity inlets - same edge

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Old   July 19, 2005, 22:31
Default two velocity inlets - same edge
  #1
john
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I am modeling water and gas phases through a 2D pipe.

At the inlet, I want to have two velocity inlet boundary conditions (one for each phase).

I am not sure how to do this.

I have tried to create two edges at the inlet which allows me to create two velocity inlet conditions. However when I export the mesh, Gambit is unable to export the edge (and the second boundary condition). This is logical since it was not attached to the mesh.

Any ideas on how to solve this problem will be appreciated.
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Old   July 19, 2005, 22:33
Default Re: two velocity inlets - same edge
  #2
zxaar
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split the edge connected to mesh into two parts as you want, and then specify the boundary condition on it.
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Old   July 20, 2005, 02:35
Default Re: two velocity inlets - same edge
  #3
Swarup
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one way is that you create two edges at outlet also and then carry out meshing edge to edge between inlet and outlet. it should be exported. once imported, merge the edges you do not need to create a single edge (say at outlet) and you will be able to assign a single boundary condition to that edge. Swarup.
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Old   July 20, 2005, 04:04
Default Re: two velocity inlets - same edge
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Mahesh
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If those flows are mixing, with multiphase model, u can define seperate velocity for each phase.
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Old   July 20, 2005, 07:12
Default Re: two velocity inlets - same edge
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John
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Initially the liquid phase is laminar and separate from the turbulent gas phase. It then comes to a junction where the liquid phase separates and becomes turbulent. It is here that the liquid may mix slightly with the gas phase.

I am using the VOF model since for the majority of the flow, the liquid film is separate.

I have solved, with help from everyone above, the problem of defining two booundary conditions (by splitting the edge).

I would like to know if it necessary to define the laminar liquid zone as a laminar zone.

If so, how would I do this?

Thankyou all.
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Old   July 20, 2005, 08:00
Default Re: two velocity inlets - same edge
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Mahesh
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If ur liquid is always is laminar, in the BC panel, define the fluid as laminar.
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Old   July 20, 2005, 08:19
Default Re: two velocity inlets - same edge
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edi ghirardi
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models>viscous>laminar

Edi.
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Old   July 20, 2005, 08:48
Default Re: two velocity inlets - same edge
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John
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The gas phase is turbulent, hence I want a turbulent model.

The question I asked wasn't put right. Let me ask this:

How would you go about defining the turbulent parameters for the liquid phase (which is only a thin film on the inside of a pipe). I am using the standard k-epsilon turbulence model.

I have calculated the turbulent length, l, and intensity, I, values for the gas phase using the diameter of the pipe and the reynolds number of the gas.

Is there a method for calculating these turbulence parameters for a thin liquid film on the inside of a pipe wall?
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Old   July 20, 2005, 09:25
Default Re: two velocity inlets - same edge
  #9
edi ghirardi
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Well, this may be a hint but never tested: define your viscous modelling as turbolent with the parameters calculated for the gaseous phase and define the fluid zone where you suppose the liquid phase is as a laminar zone in the boundary condition panel (supposing the liquid is flowing as laminar). You must divide your domain, of course. I think you can do it with VOF.

Hope this helps,

Edi.
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Old   July 21, 2005, 13:50
Default Re: two velocity inlets - same edge
  #10
T.Hariharanath
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hi,u can split the edge,according to ur requirment,and give in gambit two different boundary conditions for these two edges,then this solves ur poblem
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