Secondary flows in ducts of square cross-section

Abstract

The paper presents the outcome of experimental research on turbulence-induced secondary flows in square-sectioned ducts. The main emphasis of the experiments has been on the measurement of the secondary flows in a duct with equally roughened surfaces. Here the secondary flow is a substantially larger proportion of the axial flow than is the case in smooth-walled ducts. With the secondary velocities normalized by the friction velocity, however, the resultant profiles for smooth and rough surfaces are the same, within the precision of the measurements.