Turbulent characteristics of the flow in an axially rotating pipe

This study examines the effects of the swirl driven by a rotating pipe wall on turbulent flow characteristics. Velocity measurements were performed at Reynolds number Re=20000 using a single-component laser-Doppler velocimetry (LDV) operated in forward scatter. The test apparatus was refractive index matched, allowing measurement of the turbulent fluctuation velocities and Reynolds shear stresses of the flow in an axially rotating pipe. The results indicate that the intensity of turbulence in the rotating pipe decreases gradually with an increase in pipe rotation due to the stabilizing effect of the centrifugal force. The Reynolds shear stresses decrease markedly as compared with turbulence intensity, and momentum transfer by turbulence is suppressed strongly in the rotating pipe. Based on the experimental results, the relationship between the reduced mixing length and Richardson number is verified for the turbulent flow in the rotating pipe. Data on skewness and flatness factors, time records of velocity fluctuation, and their power spectra are also presented and show the change in turbulence structures.