[cosbergel]

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

[sfotovati]

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!

[btsusi]

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!

[cosbergel]

@ 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

[btsusi]

cosbergel,
Thank you for the quick response, I will try your advice!

[wavefunction]

Originally Posted by cosbergel

@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.

Hello cosbergel! I am currently running a simulation on evaporation of a sessile droplet. The same problem of droplet disintegration happens to me too. Do you have any tips on solving this? Should I change the div schemes to a bounded scheme like Gauss upwind?