Experimental investigation of confined swirling flow and its interaction with a bluff body

Detailed laser Doppler velocimetry (LDV) measurements of profiles of mean axial and tangential velocities and their corresponding root-mean-square (RMS) components in confined turbulent swirling pipe flow with and without the presence of a conical bluff body have been conducted. The working fluid was water and the Reynolds number based on the bulk velocity inside the pipe was equal to 40,850. The main focus of the study was to document the interaction between turbulent swirling flow inside a pipe and in the presence of a conical bluff body. The flow structure was found in all cases to be composed of a forced-free vortex. The swirl decay was exponential for Reynolds numbers of 40,850 and 14,450. The effect of the presence of the bluff body on the flow is limited to a short region upstream of it; so that the effect on the flow structure and strength of swirl upstream can be considered negligible. The flow around the bluff body adopts a different structure where the mean axial and tangential velocities tend to assume uniform profiles with turbulence activity limited to the region close to the surface of the bluff body.