I'm sorry but where did you come up with this conclusion? from computer software prediction?Scott said:The trumpets do need to be rolled back further to smooth the flow out into them, but the area behind them will have no bearing on turbulence.
When a moving gas meets a surface that is opposite or not along the direction of the initial flow you will get a change of direction of the gas. When a gas reaches the corners of each trumpet, you will see turbulence, the gas will not sit there, the flow willl change to a pattern similar to a swirl.
Every read out of wind tunnel measurements (NOT CFD software predictions) show gas will behave that way when it is forced to change direction against acute angles such as corners or surface gradients exceeding 11-15% of the original direction of flow