Author(s): P. Prinos; A. Zeris
Abstract: The characteristics of turbulent flow in open channels with steep slopes are studied experimentally and numerically. Velocity measurements indicate that the von Karman constant K of the log law of the wall remains constant in both the subcritical and supercritical regimes while the constant A decreases with increasing Fr number. A modified Preston tube method is developed for estimating the boundary shear stress in flows with unknown constant of the log law of the wall and gives satisfactory results. Two low-Re turbulence models of the k-∊ type are used in the computational study and are found to reproduce satisfactorily the velocity distribution except in the case of very steep slopes (high Fr number). They also predict the reduction of the viscous sub-layer in supercritical flows but they fail to predict the reduction of the turbulence kinetic energy and turbulence intensities for such conditions due to their isotropic nature.