I might be able to help with finding the terminal velocity of the droplet, but it's all nonlinear depending on the size. What is the size of the droplet? Is it falling through air?

Droplet size under consideration varies from 5 um to 500 um. Yes, its falling through air.

I think those droplets are big enought that you should be able to use the Stoke's settling velocity as a decent estimate, though less than about twenty microns might need a better estimation. Ther teminal velocity of the 100 micron and smaller droplets is surprisingly slow. Down to about 10 microns they fall so slowly that I suspect the surface tension is going to overwhelm much of your other deformation simulations.

There is a little Stokes calculator here: http://www.ajdesigner.com/phpstokeslaw/stokes_law_terminal_velocity.php

A good first step might be to plot your settling velocity for your range of particle diameters. (They're droplet shaped, but you can use the aerodynamic diameter, which is basically the average diameter.) I suspect that you're going to see that you'll need a few different simulations for the impact and spreading.

Thanks a lot. Could you please help me with the questions. I asked in my post? I did some simulations but I am having trouble dealing with a few things.

You have a very difficult problem with this. I don't know the specifics of your simulation software, but the physics behind this is insanely complicated, I'm afraid it's too complicated for me ... the transition from impact to spreading and surface tension, the droplet doesn't hit all at once but rather hits as a time-varying function of the diameter of the droplet. Then when it does hit the diameter changes through the impact. The surface tension changes nonlinearly with the contact area, the surface characteristics change through the impact too.

I'm getting a headache just trying to make sense of all this complexity. If you can handle it from an engineering perspective and put some level of faith in your simulation software then you're way ahead of anything I can offer. Even the Stokes settling velocity is just a crude approximation.

You have the 2,000 lb. grizzly bear of hydrodynamic problems on your hands.

You may want to look at the work of Taehun Lee. For example http://prem.ccny.cuny.edu/files/Lattice%20Boltzmann%20Simulations%20of%20Micron-scale%20Drop%20Impact%20on%20Dry%20Surfaces.pdf

Thank you very much

In reality there a great many numerical methods that solve multiphase flow problems such as tours.The most commonly used one is the VOF method applied either through a research code or within a commercial one such as CFX. Also note that none are capable of taking into account all of the complexity in such problems in a completely satisfactory way. This also includes SPH which has some severe problems of its own. For example while the VOF method ensures excellent mass conservation and interface width it has been known to produce unphysical volume groupings. On the other hand SPH has problems properly satisfying solid wall boundary conditions.

its best to do a good deal of background research and choose the method which is best for your problem. If you need a quick solution then you must rely on commercial codes with all of their associated weaknesses. This area of fluid dynamics remains a vigorous research area and is by no means resolved.

Thank you Frank Bierbrauer.

You can use interFoam solver of OpenFoam which uses VOF but level Set can be added if you want. In that case you can set the initial velocity to the droplet by changing internal Field values and dynamic contact angle by giving values to thetaR and thetaA.

Thank you very much Suhas Suresh. I have been using Gerris Flow solver for a while. It uses quadtree/octree based adaptive mesh refinement and it provides excellent result for interface tracking. It uses VOF method. It also has contact angle support

Hi, I am trying to simulate the impact of a sphere particle (0.5mm) and a plate with COMSOL. I use the Solid Mechanics module and Stationary study for the simulation. I also want to set an initial velocity for the particle, so I revised the "Structural velocity field"in the "Initial Values" node. However, I found it totally did not work. I just got the same results without the setting and I am very confused. Could you tell me how did you set the initial velocity for the droplet with your simulation? Thank you in advance.