In order to accurately simulate strong three-dimensional (3-D) free surface flows and sediment transport, the fully 3-D non-hydrostatic pressure models are developed based on the incompressible Navier-Stokes equations and convection–diffusion equation of sediment concentration with the mixing triangle and quadrilateral grids. The governing equations are discretized with the unstructured finite volume method in order to provide conservation properties of mass and momentum, and flexibility with practical application. It is shown that it is first-order accurate on nonuniform plane two-dimensional (2-D) grids and second-order accurate on uniform plane grids. A third-order approximation of the vertical velocity at the top-layer is applied. In such a way, free surface zero stress boundary condition is satisfied maturely, and very few vertical layers are needed to give an accurate solution even for complex discontinuous flow and short wave simulation. The model is applied to four examples to simulate strong 3-D free surface flows and sediment transport where non-hydrostatic pressures have a considerable effect on the velocity field. The newly developed model is verified against analytical solutions with an excellent agreement.

A tunable surface tension pseudo-potential lattice Boltzmann method (LBM) is applied to study a droplet splashing on a thin film over a rough surface. Our study focuses on the crown evolution processes influenced by various roughness parameters, including the protrusion height and the distance between two protrusions. The total kinetic energy of the crown is introduced to study the evolution process. The results indicate that more kinetic energy is consumed in the collision process and that the crown has a shorter dimensionless height in the case of a rough surface than with a flat surface. A threshold dimensionless protrusion height exists at which the energy consumption is minimized and the crown height is maximized. The dimensionless distance between two protrusions may affect the symmetry of the liquid crown but does not influence the kinetic energy consumed in the impact process. Neither the protrusion height nor the distance between two protrusions has a significant effect on the crown radius evolution process. This study shows that the proposed LBM pseudo-potential model is an effective tool for predicting the process of a droplet impacting a thin film in the presence of complex boundaries.

The water level is a critical hydraulic parameter for inland ship safe navigation, as well as an important variable in inland waterway transport minoring and assistant systems. As a basic and traditional method, the one-dimensional (1D) hydrodynamic model is adapted to simulate river sections/waterway segments to obtain water levels numerically. However, the friction factor, i.e., Manning’s coefficient n, is a sensitive parameter for the traditional 1D hydrodynamic model. Its calibration or identification is not only very time-consuming but also unpractical. Due to its sensitivity to the simulation results, usually, one identified parameter cannot be adopted into other flow scenarios. It has been concluded that the unfitness of the traditional empirical quasi-steady friction formulae leads to these consequences/phenomena. Besides finding advanced parameter calibration algorithms and updating friction parameters dynamically, employing a true unsteady friction formula to replace the quasi-steady friction formula is a thorough solution to the problem. In this study, we introduced a newly proposed 1D unsteady friction formula to the momentum equation of the Saint-Venant Equations, thus a modified 1D hydrodynamic model was developed. To validate its capability in simulating water levels, the modified model was adopted into the Xia-la-xian – La-he-lian section of Daying River; and compared with the traditional model with the Manning formula. Results showed that the modified hydrodynamic model performs better in both water level and cross-sectional average velocity simulation. The research results can be used to support the construction of intelligent water level warning systems, intelligent shipping, and digital waterway transportation platforms.

The fluctuation of water level caused by the unsteady flow of lock discharge, where the key problem is the relationships between the hydraulic factors in the restricted middle navigable channel and the transformation of unsteady flow and the corresponding scales are investigated. Based on the restricted middle navigable channel of the Baise navigation project, the relationship between the unsteady flow discharge process of lock and the water surface fluctuation process in the restricted middle channel is studied through systematic experiments, and the conclusion is drawn as follows. The main reason caused the flow fluctuation is attributed to the insufficient energy dissipation and rapid increase of discharge during the lock discharge process. And the sectional discharge method which reduces the peak value of the discharge process can reduce the fluctuation of upstream and downstream water level effectively. By reducing the peak value of the time-discharge curve, the energy dissipation along with restricted middle navigable channel increases, with the fluctuation amplitude of upstream and downstream flow reduces, and the attenuation rate of the energy dissipation increases. Furthermore, a fixed phase lag is formed between the reflection wave formed by the downstream ship lift gate and the discharge wave formed by the upstream ship lock discharge, which has little relationship with the discharge curve.

The velocity evolution process caused by the unsteady flow of lock discharge, where the key problem is the relationships between the hydraulic factors in the restricted middle navigable channel and the transformation of unsteady flow and the corresponding scales are investigated. Based on the restricted middle navigable channel of the Baise navigation project, the relationship between the unsteady flow discharge process of lock and the velocity evolution process in the restricted middle channel is studied through systematic experiments, and the conclusion is drawn as follows. The main reason caused the flow fluctuation is attributed to insufficient energy dissipation, the rapid increase of discharge during the lock discharge process, and the limited boundaries. By reducing the peak value of the time-discharge curve, the maximum velocity and maximum inverse velocity decrease in the upper restricted middle navigable channel. In the long restricted middle navigable channel, due to the energy consumption, the velocity fluctuation in the downstream is much smaller than that in the upstream, which still exists after the flow pattern reaches a steady state. This study can provide a theoretical basis for the middle channel layout design.