An experimental study of turbulent flow through concentric annuli

Abstract

Results are presented of experiments carried out in fully developed unidirectional turbulent flow in three smooth concentric annuli. The radius ratios were 2.88, 5.62 and 9.37 and with air as the working fluid the Reynolds number range was from 6000 to 90,000.The hydrodynamic entrance length was found to be much the same as for round tubes. The friction factor was found to be independent of radius ratio within the limits of experimental accuracy. Velocity profiles were measured in detail. In particular, it was found that the radius of maximum velocity for turbulent flow is different from its value for laminar flow. The difference was found to be a function of both Reynolds number and radius ratio. It was not found possible to describe the non-dimensional velocity profiles by a logarithmic law except for the outer profile in the higher radius ratios with the higher Reynolds numbers. In this particular case excellent agreement was found with results for plain tubes. In all other cases there was a complicated but self-consistent variation of the non-dimensional velocity profile correlation with radius ratio and, especially, with Reynolds number.