# Falling Droplet using InterFoam

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 October 16, 2013, 12:28 Falling Droplet using InterFoam #1 New Member   Kostis Join Date: Jan 2013 Posts: 6 Rep Power: 5 Hi guys, I am trying to simulate a 3D droplet falling due to gravity forces with interFoam as simple as that. When the droplet reaches a velocity I will put it in a jet flow using mapFields. I have encountered some strange things and I cant even do the first part. a) Should I change the pressure inside the droplet due to the surface tension? p=2*sigma/r. What about the distribution of pressure inside the droplet due to gravity? b) Do you believe that the outcome would be the same if I enter a velocity in funkySetFieldsDict? c) Finally, the droplet disintergrates very quickly before it reaches the velocity (1m/s) which is totally unnatural. Why is that? (personally, I do not think it is about contact angle) Thank you for you time Kostis

 November 12, 2013, 19:22 #2 Member   Shawn Fotovati Join Date: Jul 2009 Location: Cincinnati, OH Posts: 41 Rep Power: 9 You should not change the pressure. Solver must calculate it during the solution. If droplet disintegrates, I believe it is due to mesh, change the mesh and see if it is improved. I have another problem; Right before droplet hits the surface, it stops moving, and hangs around in the air! I have no idea why this happens for my case!

 December 2, 2013, 18:30 #3 New Member   Join Date: Dec 2013 Posts: 2 Rep Power: 0 cosbergel, I have been having trouble with a 3D droplet behaving almost the same way you described. My grid is refined to .1mm spacing for a 2mm droplet which I thought was sufficient. An order of magnitude refinement did not help. Were you able to figure out your problem? I was using multiphaseInterFoam, but the advice should probably be similar for both. I appreciate any help!

 December 3, 2013, 06:15 #4 New Member   Kostis Join Date: Jan 2013 Posts: 6 Rep Power: 5 @ sfotovati as far as the pressure is concerned, you are right that the solver calculates the pressure inside the droplet but I found out that it is better to put it as an initial condition because otherwise you ll have perturbations on the surface of the droplet. I think that you have put wrong boundary condition on the wall. @btsusi I manage to solve my problem firstly by not using dynamic refinement and then by changing the div schemes (specially for alpha1) for interFoam and interDyMFoam which I had it finally working. In my opinion satisfactory number of cells inside a droplet is 50- 100. Regards, Kostis

 December 3, 2013, 10:10 #5 New Member   Join Date: Dec 2013 Posts: 2 Rep Power: 0 cosbergel, Thank you for the quick response, I will try your advice!

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