# How to study pressure drop of continous phase in VOF model

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 February 5, 2014, 06:26 How to study pressure drop of continous phase in VOF model #1 Member   sajeesh Join Date: Feb 2013 Posts: 52 Rep Power: 6 Sponsored Links 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

 February 5, 2014, 07:28 #2 Senior Member     Alex Join Date: Jun 2012 Location: Germany Posts: 1,504 Rep Power: 25 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.

 February 5, 2014, 08:24 #3 Member   sajeesh Join Date: Feb 2013 Posts: 52 Rep Power: 6 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.

 February 5, 2014, 09:42 #4 Senior Member     Alex Join Date: Jun 2012 Location: Germany Posts: 1,504 Rep Power: 25 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.

 February 5, 2014, 23:01 #5 Member   sajeesh Join Date: Feb 2013 Posts: 52 Rep Power: 6 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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