Discussion Forum

Start by drawing the geometry with COMSOL.

I done this. but then i have no idea which physics behind the spraying process and i have not find any literatur about such processes. i think perhaps navier stokes. The nozzle-typ is a hollow cone. So i have a thin layer at first, which break at small droplets. But i dont know how i can descrbe this process with equations.

Michael,

I hesitated before I decided to respond because I don't like discouraging people but I think what you are wanting to do is a hugely monumental task and you don't realize what you are up against :) Please forgive my candor.

Simulating drop breakup/spray formation from first principles is very hard because 1- the underlying physics is non-trivial (not that N-S is trivial itself, but this is even more complicated due to the nature of free surface BCs) and 2- implemeting this computationally is very difficult too. Belive me I would know because I spent my entire Ph.D. coming up with a way of doing this for a single droplet and simulating it with finite element code that I wrote myself.

I suggest you find some literature and read up on the subject to see for yourself the underlying physics/math before you even begin to worry about simulating it.

If you need engineering answers there might be other feasible ways of getting them (engineering correlations, experiments etc.). Although I am a computational guy myself, CFD is not always the best way to go after a problem- it all depends on what you want and what your constraints are.

Hope this helps
Ozgur

I am also interested in spray simulation for liquids, nozzles.

So is it save to assume that Comsol is not the program I'm looking for?
Here they mention nozzles: www.comsol.com/products/cfd/?tab=appareas but I guess that is an optimistic marketing thing.

Did anyone see a simulation model with mist?

i came through your post because i have same model that i have to use for my thesis, so is there any luck to simulate nozzle spray (mist)?





Thanks

I agree about the complexity of this problem. Droplet breakup in a nozzle is largely governed by flow non-idealities at the surface of the ligand. Numerically, these instabilities are difficult to quantify. Then tracking the free surface formation from fundamental principles becomes a monumental task. There are many empirical models for drop formation, but are limited to specific nozzle designs. You might be able to couple a finite element approach for flow within a nozzle with the empirical equations for the breakup to get what you need.