I have to simulate an impingement jet (water)on a flat plate.I'm not sure which model I have to choose, Mixture,VOF... I also have problems with the boundary conditions,inlet velocity,wall_nozzle,outlet_side,outlet_top, wall_plate.Is this correct? I got warnings reversed flow, and the flow field is not correct! Can someone help me, thanks!

Well, if it is a water jet in air and the velocity is not so high that drag and lift forces play a major role, I would suggest VOF. In the inlet remember to specify the volume fraction of water (I think it must be 1, right?). Consider whatever to enable gravity or not. If you have reversed flow at the outlet (pressure outlet), consider to extend your domain until the flow is more stable.

These are some simple suggestions, hope it helps,

Edi.

Why VOF and not a mixture model, what is with turbulence model, I thougth it is not available in VOF. The only data I have is the inlet_velocity and the nozzle to plate distance.I have extended my domain, but the flow still looks really strange!Are my boundary conditions OK? Inlet_velocity, plate_wall, nozzle_wall, side_wall_pressure outlet and the upper wall also pressure outlet!Thanks!

How about discrete phase model? I also model a impingment jet, you can enable the accretion rate option. I am still working on this. Hope this will help.