Combustion jET
 

Hello I am trying to model combustion out of a jet. I have got a running simulation using k-epsilon, species transport models to model turbulence and combustion. However the results are not very realistic. the flow outside of the jet spreads too much and the just outside of the nozzle exit the flow is doing something very strange which I can not explain. I have attached a picture of my velocity field and what the field looks like experimentally I would really appreciate some help fixing this as I have tried everything to fix this.