Shallow turbulent flow simulation using two-length-scale model

Numerical simulations of the planar starting jets were conducted using a tw o-length-scale turbulence model and a hydraulic code to study the effect of friction on 2D turbulence in shallow open-channel how. The simulation resu lts were compared with the data of the starting jets obtained in a recent s eries of laboratory experiments conducted in a large tank of small thicknes s. Dividing the turbulence energies into large and small scales, and calcul ating the energies with separate models, the observed friction effects on t he 2D large-scale turbulent motion were correctly simulated by a two-length -scale turbulence model. To maintain the large-scale turbulence in the shal low shear flow, the production of turbulence energy by the transverse shear must be greater than the dissipation of the energy by friction. The critic al gradient bed-friction number obtained from the simulations of the starti ng jets was S-c similar or equal to 0.08, which is consistent with the expe rimental observations in other shallow turbulent flows.