[sgov000ster]

I have cylindrical domain through which air is flowing at a constant volumetric flow rate.So, only the volumetric flow rate is known at the outlet ( where flow is incompressible), with a known cross sectional area. Within the cylinder ,however, a transient injection of evaporating particles is made at around 200m/s.By the time the spray reaches the outlet , the flow is incompressible. The way I was looking to approach the problem is by specifying a fixed velocity at the outlet through the velocity inlet BC, so that volumetric flow rate is fixed while using the compressible gas law. However, the species concentration needs to be specified at the outlet. The vapor conc at t=0 is 0. The vapor conc. /mass /pressure as a function of time is unknown. Specifying a 0 vapor fraction at the outlet, leads to vapor build up within the system after sometime, which accelerates the flow and leads to basically an unrealistic flow field and poor convergence.

Any suggestions?