Turbulence Measurements in Smooth and Rough‐Walled Trapezoidal Ducts

Abstract

Experiments were performed in turbulent air flow in a trapezoidal duct with a mean aspect ratio of 3.5, corner angles of 64 and 116 degrees, and with both hydraulically smooth and partly roughened walls. Measurements in the fully developed flow region include wall shear stress and isocontours of the axial mean velocity, the normal and shearing turbulent stresses, and the turbulent kinetic energy. The formation of possibly symmetric secondary flows near smooth‐wall corners, and their suppression near smooth and rough‐wall corners, are documented. Finally, the inadequacy of gradient transport as a model of this flow is demonstrated.