MODELING TURBULENCE MECHANISMS IN FLOWS OVER ABRUPT DROPS IN BED ELEVATION

Results are presented of a computational study of turbulent free surfa ce Bow over an abrupt drop in bed elevation. The Reynolds averaged Nav ier-Stokes equations are solved using an operator splitting technique. Different constitutive laws, both linear and a nonlinear, are employe d for the turbulent stress-strain relationship. A particular treatment of the troublesome Oldroyd derivative terms in the nonlinear constitu tive law is advocated. The model is applied to the problem of free sur face flow over an abrupt drop in bed elevation. The computational resu lts are compared with experimental measurements. Comparisons are drawn for the mean flow field velocities, the turbulence intensities, and t he Reynolds shear stresses. This technical note concludes that the use of nonlinear turbulent stress-strain relationships is an important ne w development in engineering fluid mechanics and advocates the future study of such constitutive laws.