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Analysing oil droplet distribution and droplet size of oil in an oil-water mixture


    • Muhammad_atif

      Hello all,

      I am running an analysis of the oil-water control valves. My aim is to improve the amount of shear generated by the valve body as the flow pass through it. As a result of this shear, the droplet breaks down and the separation of oil from water becomes difficult in the later stage.

      I am running oil and water multiphase analysis using the Eulerian model in Ansys Fluent. I am using water as primary and oil as a secondary fluid and I am using sauter mean model to provide range of droplet diameter (min0.0001 to max0.0002). I am new with multiphase and have a couple of questions.

      1. My volume fraction is high and unable to use the DPM model. Is there a way to see droplet size distribution using the Eulerian model?
      2. I used the diameter option available under the properties tab but the information does not make any sense. Please see attached picture, I have created a stratified flow at the inlet where the top half is oil and bottom half of the pipe is water. But the line plot at the middle near the inlet is showing 0.0001 dia of oil whereas this area is completely filled with water(also the contour plot is showing oil droplet at the bottom half of the pipe where it should be zero as the area is covered by water). My question is what is this diameter range and how it is defining the diameter of a droplet when the flow is fully stratified? I used the VOF model as well and the flow pattern at the inlet side was similar but after valve the flow becomes dispersed so the Ansys manual suggests using the Eulerian model. I also have a swirler in the outlet side so the flow would be quite dispersed nature.
      3. I am expecting the oil droplet to break as they pass through the valve and coalescence after passing through swirler. Is it possible to capture this phenomenon without turning the Population balance model ON? I tried turning it on and have not noticed any difference in the results with and without it. The oil volume fraction is high in the middle of the pipe after it passes through the swirler. I am wondering how this coalescence took place when the population balance model was off?

      I hope my questions are making sense. Please let me know if something is not very clear here.



    • DrAmine
      Ansys Employee
      1/for that ou require population balance or iac transport model.
      2/given your screenshots I guess a multivof eulerian model is sufficient though. There you won't have any distribution.

      You have a multi regime flow problem so a regime aware modeling is requires.

    • Muhammad_atif
      Hi DrAmine Thank you so much for your reply.
      I am already using iac model with the settings given below. But when I am plotting contour or xy plot it is showing only one size (Max dia) of droplets in the whole domain. Is there something I am defining wrong?
      My objective of the study is to show the droplet breakage and coalescence as the oil-water mixture passes through the valve. Is there a way to quantify this phenomenon in Ansys?


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