Simulating Oil on the water is not hard with Flip.
Just we should set lower Density for Oil , for example :
Water Density : 1000
Oil Density : 975
Also we should set a little Viscosity for Oil.

Now we can see that the Oil go up and cover top of the water.

But in this project I wanted to save circle shape of the Oil (Drop shape) on animation.
In the normal way Oil's drops covered water after certain time and lose it's circle shape (Drop Shape)!

So I found a very simple and interesting way for solving this problem :

1. At the first I used different ID attr for each drop.

2. I added a “SOP Solver” in the AutoDOPNetwork to save circle shape (Drop Shape) of the oils on the water over time.

3. I added “For Each” SOP in the SOP Solver for doing below operation on all of the drops

4. I measured Area of each drop and compare it with reference value.
If Area is greater than reference value , Then I used negative “Divergence Field” to fix area of each drops between certain value .

You can see final result in this link :

http://www.jkcompany.org/JK_HoudiniAlbum.html [jkcompany.org]

Very nice approach, indeed. The divergence part, specially.
Are you taking a big hit on performance because of the For Each acting at sim time? In my head it sounds kinda slow for a lot of particles….

Oh No , I didn't used “For Each SOP” for each particles , I used it only for each drop !

In my video , I have only two Oil Drop , OK , and I have only 2 unique ID for Drops , So “For Each SOP” doing this operation only 2 times and it's not slow :wink:

Good Technique..Thanks for sharing!

Hi Joker386.

I would like to make a project based on the interaction between two fluids with different densities.
Your water/oil animation is really amazing and a very good starting point for me, but I can't understand how to make the two fluids react each other.
Let's say we have a tank filled with a certain fluid (with a certain density).
I want to create an object pouring a different fluid (with different density) into the tank.
But the pouring fluid does not interact (collide) with the tank and gets lost below the tank.
Any solution?
Thank you in advance