3d jet discharging in to atmosphere
 

I am performing numerical simulations on particle laden jets for my final year major project. I am trying to create a 3d mesh in gambit for a jet which discharges in to atmosphere. A 2d mesh creation for the same problem was simple enough but i am having problems to understand how a 3d geometery is created in gambit. Do i need to create a jet source first e,g a pipe or a duct which is then connected to a bigger box, in to which the jet will be discharged? I have tried to create the mesh this way and applied the boundary conditions to the best of my knowlegde but when i run the simulation in fluent, the flow is only simulated in the small duct/pipe and it seems like it never enters the bigger box. I will be very grateful for any suggestions.

it sounds like a connectivity problem between your pipe and the bigger box.
Try to enforce connectivity at this "interface" (face/connectivity)

Thanks for your reply max I already managed to create the geometry. When I used connect faces command in gambit I got the message that it didn't make any difference (can't remember the exact message now). I then used spilt volumes command and that did the trick. However while meshing the geometry when I selected the both volumes and tried to generate the mesh using default value of 1, it ended up generating a surface mesh therefore I had to mesh the edges of the face which is common for both volumes and where two volumes connect each other and then mesh the rest of the volume. Hope that help anyone else trying to solve the same problem.
Now I want to simulate a two-phase flow using the same geometry. To be precise it is a liquid droplets laden jet so should I use multiphase model or discrete phase model? The scope of my project remains within the regime of dilute suspension and two way coupling therefore the volume fraction of particles should not exceed 10e-3 but in DPM there is no option for volume fraction. Any suggestions for this problem? Thanks once again for your reply