Measurement of Fully Developed Turbulent Flow through Rectangular Duct with Roughened Short-Side Walls.

Abstract

A fully developed turbulent flow in a rectangular duct with rib-roughened short-side walls has been measured by hot-wire anemometers. Detailed results obtained in two cross sections, the midpoint between two ribs and on top of a rib, are presented for quantities such as coefficient of flow resistance, local wall shear stress, primary and secondary flow velocities, turbulence kinetic energy, and turbulent shear stresses. It has been found that only one large longitudinal vortex appears in a quadrant cross section of the present rough duct, which causes strong distortions in the contours of the primary flow velocity. The turbulent shear stress that is normal to the rough wall becomes much larger than that of the smooth duct, but that parallel to the rough wall shows almost the same distribution as the smooth duct, qualitatively and quantitatively. The distribution of the secondary flow vectors changes depending on the distance between the rib and the measuring cross section. However, the distributions of the turbulent stresses are independent of the streamwise location of the measuring cross section.