gas flow out of a C-D channel
 

Hi dear all,


I met a problem when simulating a high-temperature gas flow through a convergent-divergent channel (the channel consists of several parts, and the last part at the end of the channel is a divergent nozzle). Since both the geometry and the boundary conditions are axis-symmetric in this case, I expect the gas flow exiting the nozzle would be axi-symmetric (centering around the axis). However, what I found is: the gas flow first shoot out of the nozzle along the centerline, then, as the iteration goes, the gas jet starts to bend and eventually follows the curve of the divergent nozzle, exiting the domain (downstream of the nozzle) from the side, instead of the outlet which is in the opposite direction from the gas inlet.



I’m confused about this behavior, and would like to know if any of you have had similar problems before, or if you could kindly point out what mistakes I made during the simulation. (although the flow channel is convergent-divergent, the flow is subsonic with a maximum Mach number of ~0.5.)
Thank you very much!



ljp