The commonly numerical models with the conventional hydrostatic pressure and the standard isotropic k-epsilon turbulence model closure still remain the most widely used approach for the solution of practical engineering problems. However in the presence of complex flows, it is useful to resort to a more accurate model in which the non-linear turbulence model accounts for the encounter anisotropic of the flow, without hydrostatic pressure limitation. An efficient three-numerical model is developed for simulating free surface flows where the conventional hydrostatic pressure assumption is removed (presence of complex flows with short waves and/or strong bathymetry). The unsteady Reynolds-averaged Navier-Stokes equations are solved in the fixed strata system to providing the accurate resolution. Eddy coefficients are provided from the standard k epsilon turbulence using fractional step algorithm, and their modified algebraic expressions accounts for encounter anisotropic aspects in complex flows. The model is applied to simulate the 193° open channel flow for which the high quality three dimensional data set have been collected from a laboratory flume. The computed results are found to be in good agreement with experiments.