the case is multiphase flow --Eulerian model --species transport model --laminar flow --unsteady solver --3 dimensions --incompressible flow

the case involved two different fluids go through two different tubes and then enter to the tank and well mix together.

i set the velocity inlet BC for the fluid tube inlet... then wall BC for the tank and also wall BC for the tube wall. so what should the BC for the tube face that attached to the tank to make the fluid can flow inside the tank?

thanks.

First your have to spesified what is the final product of this two phase?, is it mixing type? or chemical reaction? Then after you spesified this, you have to define the phase one plus the phase to will obey what law?. Let say the result is mixing phase, then at boundary condition inlet velocity there will be mixture boundary condition, at this stage you can choose what is the velocity of each phase.

Since you have to inlet tube where only pass by only one phase each. You can easly make zero velocity for other phase while your desired phase that pass this tube has its velocity. You can do reverse value for other tube.

You should use 'interface' BC. It should be 'connected' to the tank face.

thanks prasad.