摘要

A procedure based on the discrete element method has been developed and validated to compute Fanning friction factors and Nusselt numbers for fully-developed turbulent flow in tubes artificially roughened with two-dimensional, rectangular rib-type roughness elements spaced such that flow separation and reattachment occurs between ribs. The development is presented, and computed results are compared with appropriate experimental data sets from the literature. The method captures the salient features of flow in the hydraulically-smooth, transitionally-rough, and fully-rough flow regimes with no a priori specification of the flow regime. These comparisons indicate that the discrete element roughness method is consistently valid over the following range of rectangular rib geometries: rib-height to hydraulic-diameter ratios from k/D = 0.01 to 0.0625, rib width-to-height ratios from w/k = 1 to 0.254, and rib pitch-to-height ratios from L/k = 10 to 40.