CFD study of free-surface flow in curved open-channel with velocity-pressure-free-surface correction

This paper presents a numerical study on free-surface flow in curved open-channel. A new improved SIMPLEC algorithm with velocity-pressure-free-surface coupled correction is developed and validated. Such algorithm differs from the traditional SIMPLEC algorithm and includes three correction equations which are named as the velocity correction equation, the free-surface correction equation derived from the continuity equation with the kinematic boundary conditions on the free-surface and the bottom bed, and the pressure correction equation taking the same formation as the traditional SIMPLEC algorithm does. The new improved method, in this study is used to solve the incompressible, three-dimensional, Reynolds-averaged Navier-Stokes equation set combined with the standard k-ε model and/or the low Reynolds number k-ε model for free-surface viscous flow in curved open-channels. The power law scheme (POW) is used to discretize the convection terms in these equations with a finite-volume method. The practical cases studied are free-surface flow through the 180° curved open-channel with different hydraulic discharge rates. The comparisons between computations and experiments reveal that the model is capable of predicting the detailed velocity field, including changes in secondary motion, the distribution of bed shear, and the variations of flow depth in both the transverse and the longitudinal directions. Based on the modeling results, the new improved SIMPLEC algorithm is feasible and effective for numerical study on free-surface viscous flow in curved open-channels.