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How to study pressure drop of continous phase in VOF model

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Old   February 5, 2014, 06:26
Default How to study pressure drop of continous phase in VOF model
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sajeesh
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I am doing simulation of droplet production in a T junction microchannel
using Ansys fluent VOF model.I can make the droplet and measure the diameter
of the droplet formed during the simulation as i am doing in the practical
situation.

I have separate inlets for supplying primary(oil) and secondary phases(water).

Now my problem is that while i am tracking the droplet i want to find out
the pressure drop between two test section in the channel in two situations
(1) when the droplet is not there in the test section (2) when the droplet is
present in this test section.Presently i am getting a pressure drop. That
pressure drop remains same irrespective of the size of droplet reaches there (
for another simulation with another size of droplet).So can you tell me a
method to find out the pressure drop with droplet and with out droplet in the
test section.

Now i am doing 2D simulation (as flow between the parallel plates). I define a
line in the test section.When droplet touch the section the
pressure starts to peak and reaches maximum when center of droplet crosses the
line and again drop to previous pressure when the droplet leaves the line.I
could not explain the phenomena.

Physically when droplet crosses that line the pressure in the section should hike because of the presence of droplet in the downstream
section.But in my case as soon as droplet leaves the line pressure drops to
initial value.

Is this method is not sufficient to study the pressure fluctuation.Is this
beacause of the sharing of pressure by phases in VOF model.Otherwise please
suggest me a method to study the pressure fluctuation when droplet formed by
this VOF method

Please help me

Expecting a reply
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Old   February 5, 2014, 07:28
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As long as the droplet has low velocity relative to the flow and is small compared to the channel height I would not expect much change for the pressure distribution in the channel.
So your results seem plausible to me.

The peak in pressure (i guess you mean the average pressure value over the line you described) could come from the Laplace pressure within the droplet itself.
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Old   February 5, 2014, 08:24
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Thank You very much for the fast reply.

Sir my channel is 100 um and the droplet formed of the order of 60 um.At this case pressure will fluctuate.isnt it sir.Can i continue with VOF model for this pressure drop study.
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Old   February 5, 2014, 09:42
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I am not an expert on the VOF method, but I see no reason why it should not be suitable to study the pressure field in the case you described.
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Old   February 5, 2014, 23:01
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Sir

In tutorial it is saying it is solving only one momentum equation between the phases. Two phases shares the pressure.This is the reason for my doubt
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