[Ulixes]

Hi everyone I am a student trying to simulate the flow of a droplet inside a microchannel with Fluent's VOF model.

I have been working on those simulations for 6 six and really have troubles to get some coherent results.

Basically the microchannel I am using is modellized by a simple 2D rectangle for which I am expecting a Poiseuille flow when no droplet is inside. First I have set a velocity inlet boundary condition and all simulations failed (the droplet inserted in the center of the channel sticks quickly against the walls).

Then I've tried to set a mass flow rate as inlet boundary condition. I am monitoring the mass flow rate and the maximum velocities at the outlet which are know from theoretical calcultions (by the way the outlet is far enough from the droplet so that this latter does not affect the flow). I have verified those values but computing a stationary simulation without droplet.

Now the problem is that when I am including the droplet the outgoing mass flow rate is the right one as soon as the simulation is launched whereas the maximum outlet simulation quickly converges toward a value which is not the expected one (let's say 1,8 m/s instead of 2,5 m/s).

I've checked all the calculus and the reported values of Fluent and everything is consistent. So it's not a setting problem. Maybe I am sing the wrong solver (PISO) ?

By the way, sorry for the terrible english.