Free jet B.C.
 

I am simulating a Free jet using a domain 20 diameters*20 diameters (300 x 300 pts). The Euler equations are solved in r_z coordinates with symmetry imposed on the jet centerline. The simulation is started with jet being issued from a convergent nozzle. (The nozzle exit is a fixed boundary condition) I use the non-reflective boundary condition proposed by Thompson. It seems when the jet goes through the boundary reflections are generated. How can i overcome this?

Thanks Shuo