Turbulence Kinetic Energy in Turbulent Flow through Square Ducts with Riblike Roughness Elements

Abstract

Production and convection of turbulence kinetic energy have been examined in detail for turbulent flow through square ducts with rough walls. Three kinds of ducts- a smooth-walled duct, a duct with one rough wall, and one with two facing rough walls-have been used for the experiment. Repeating-rib-type roughness elements have been used to roughen the walls. It was found that the turbulent shear stresses play the most important part in the production of the turbulence kinetic energy. Contribution of the turbulent normal stresses also has great influences on the energy production near the rough walls, although the sign of their contribution changes depending on the relative location to the roughness elements. The turbulence energy convection by secondary currents is considerably smaller than the energy production and does not affect the balance of turbulence kinetic energy in the ducts.