Influence of outlet geometry on strongly swirling turbulent flow through a circular tube

The results are reported for an extensive series of measurements (using laser Doppler anemometry) of the mean and fluctuating flow fields for swirling turbulent flow downstream of an orifice in a tube. The influence of a concentric outlet contraction is found to be negligible for low “supercritical” swirl. For high “subcritical” swirl, the outlet geometry is found to have a significant influence throughout the flow field and, in the case of an eccentric (i.e., offset) outlet, to lead to an asymmetric flow with a distorted core. In no case was the core found to precess or the flow to be periodic.