Cell Convection

Hello!
I need some tricks to know how can I simulate my problem.

I've got a rectangular cell ( 4cm height, 2,5 width, 3 mm thick) with a dilute suspension in it.
I want to investigate the possibile convection motion arising from different temperatures on the walls and from the sedimentaion of those particles ( 3 micron diamater ), but comsol offer me so many options that I'm a bit puzzled :s
(which physics should i use?? laminar flow? thermal flow? dilute suspension? or multiphysics?)

Another problem is that comsol always ask me to set inflow and outflow but i'm ina stationery condition and i don't have any flow but only sedimentation.

Finally i would like to know if is possibile to simulate a sedimentation of these colloids

Can anybody help me?

Thank you :)