[coastal593]

hi all,

i am interested in simulating a simple system in which a water droplet impacts a film of water/some other fluid on a surface. i have solved the water-impacting-water system with interFoam and the results look quite nice. i have 3 questions about how to move forward with this ...

1) i am interested in incorporating charge into my droplets, specifically in relationship to the possibility of rayleigh-explosion events due to local radius of curvature changes in the droplet upon transport and collision. anyone have any thoughts on this possibility? i'm not sure how to incorporate this or if it's currently possible.

2) i am very interested in >2 phase systems, and i see that a arbitrary phase solver is currently slated to be released with 1.4. is the any way to play around with this before official release?

3) currently my droplet starts out in rectangular form but quickly "sphericalilizes" itself due to surface tension. is there any way using setFieldsDict to indicate a spherical droplet instead of a box? right now this doesn't much matter but in a case of charged droplets this might be a big deal.

thanks very much!
anthony

[mavimo]

Hi Antony
I'm developed a similar case (a drop impact over wall), about question 3 I had subdivide sphere with 4 rectangles similar to:


Simmetry plane
*****|
*****|___
*****|___|_
*****|*********|_
*****|*********|**|
*****|*********|_|
*****|_____|
*****|___|
*****|


You can increase number of rectangle to simulate a sphere.

Bye
Marco

[pierre]

Hello,

Regarding the charge thing, I am not sure what you mean. Is it an ionised droplet phenomenon or the so-called micro-explosion of droplet when evaporation occurs.

For setting an initial field, well you can define a droplet centre cell and then loop through all cells of the domain and give them gamma = 1 if they are within a given distance (droplet radius of that seed cell) something like

Info<< "Reading field gamma\n" << runTime.timeName() << endl;

volScalarField gamma
(
IOobject
(
"gamma",
runTime.timeName(),
mesh,
IOobject::MUST_READ,
IOobject::AUTO_WRITE
),
mesh
);

vector dropletCentre = vector(1.0, 1.0, 0.0);
scalar radius = 3.0;
const vectorField& centres(mesh.C());

forAll(gamma, cellI)
{
if(mag(centres[cellI] - dropletCentre) < radius)
{
gamma[cellI] = 1.0;
}
}

Pierre

[coastal593]

thanks for your info on no. 3 i will give that a whirl.

regarding charge: currently in interfoam i am not dealing with evaporation so it would not be induced this way. to my knowledge interfoam has no mass transport abilities. however, certainly evaporation does occur and an implementation of both the ionized droplet transport and evaporation/rayleigh-explosion would be of interest.

currently though i am most interested in the possibility of charge-repulsion within a droplet and how that might evolve in the transport of these droplets to a film and upon collision.

thanks,
anthony

[mavimo]

About question 3 you can see this page.

bye
Marco