In implementing ship channels in mountainous rivers with complex topography, navigation safety has become paramount for facilitating efficient tunnel operations. The security of large vessels in tunnels has recently been the focus of a considerable amount of research in the inevitable trend of vessel upsizing. This study analyzes the characteristics of unpowered coasting distance for ten-thousand-ton bulk carriers through ship simulations. The study discovered a positive correlation between coasting length and variables including tunnel width, water depth, and sectional coefficient. Moreover, it explores the maneuvering characteristics throughout the tunnel traversal process. It proposes a vessel-following model based on car-following theory and defines different types of following distances to determine the transportation capacity of the tunnel. The research findings greatly enhance tunnel navigable safety and optimize ship tunnel operations.

With the widespread use of sector gates in tidal river locks, there is a growing interest in the operating force during the gate operation. This study investigates the characteristics of operating forces in a sector gate hydraulic cylinder system using prototype testing and focuses on the effects of different heads and flow velocities under the operating forces. The results reveal significant differences in the opening processes between normal and reverse heads, with head differentials and direction playing crucial roles in determining the operating force under flowing conditions. In still water, both gate opening and closing processes are divided into four and three stages, respectively, with the operating force remaining stable during the low-force operation stage. In particular, during gate closure under flowing conditions, flow velocity emerges as a key factor influencing the operating force, with the force during the small gate opening stage exhibiting a parabolic relationship with flow velocity. These findings provide valuable insights for the design and selection of hydraulic gate control systems, contributing to the safe operation of gates and efficient navigation of waterways.

In this study, the effects of the different conveyance modes of the intermediate channel in decentralized cascade locks on navigation flow conditions were investigated. A new hybrid numerical simulation method was established to evaluate navigable flow conditions in intermediate channels at different water conveyance modes. This hybrid numerical simulation method was reliably compared by physical modeling tests. We used the 33.73 m class high-head intermediate channel filled with water as a study case. The study used the maximum water surface slope and maximum flow velocity as evaluation indexes for navigable flow conditions. The results showed that the navigable flow conditions of the centralized water conveyance mode were worse compared to the decentralized water conveyance mode in the intermediate channel. Especially in the upstream region of the intermediate channel with a centralized outflow, the navigable flow conditions were exceptionally harsh. We recommend the decentralized outflow mode in the high-head intermediate channel. This study provides an effective numerical simulation method for optimizing the water conveyance mode of the high-head intermediate channel of decentralized cascade locks and saving project investment.

Strong transverse flows and fluctuations often occur in the downstream approach channel and entrance area during flood discharge at high dam hubs. This study takes a power station as a research sample. Flow velocities, transverse flow intensities, fluctuation characteristics and ship navigation status are analyzed and studied through field observations. The results show that during flood discharge the entrance area experiences transverse short-wave fluctuations and significant transverse currents. The oscillation of hydraulic jumps is the direct factor causing fluctuations in the downstream entrance area. The fluctuation amplitude of the center and edge of the entrance area was generally large, and the fluctuation spread to the approach channel and continuous attenuation. The main fluctuation attenuation occurs at the transition from the broad riverway to the downstream restricted approach channel. As the flood discharge increases, the lateral rolling of the ships becomes more pronounced. The change in power station discharge has a relatively small effect on the ships’ heeling and trim.

This study aims to provide a deeper analysis of the mechanical effects induced by turbulent flow characteristics in the gate recess on the sector gate during dynamic water closure. A full-scale three-dimensional geometric model focusing on the gate body was constructed using actual dimensional data. The third-generation Liutex-Omega vortex identification criterion was employed to clarify the evolution of vortex structures and quantify vortex intensity. The temporal variation of forces acting on the nose and skin plate was systematically analyzed through shear effects and stagnation pressure characteristics, revealing the interaction mechanisms between the gate and the flow during closure. The results demonstrate that the absolute vortex intensity near the central nose and side noses alternates in dominance, with two instances of equal intensity. The vortex evolution within the gate recess progresses through eight distinct stages. During the primary vortex attenuation and dissipation stage, transient peak operating forces arise due to a short moment arm, strong shear forces, and a resultant force near the side nose that tends to open the gate. The force peak occurs at gate openings ranging from 0.20 to 0.25, and exhibits an exponential relationship with the chamber flow velocity. This study offers novel insights into the force behavior characterization of sector gates under hydrodynamic operating conditions.

Flood control, power generation and agricultural irrigation are the primary functions of reservoirs. The main reason for the serious deposition in the Yellow River reservoir is the high concentration of sediment in the water flow. Due to the establishment of the Yellow River cascade reservoir and the joint scheduling among reservoirs, the flow rate of the downstream reservoir decreases in flood season, which reduces the hydrodynamic flushing efficiency in the reservoir area. Wanjiazhai Reservoir is selected as the research sample in the present study, which is a first-level cascade reservoir in the connecting area of the upper and middle reaches of the Yellow River. In this study, a numerical model was built to analyze factors that influenced the operation and flushing of the upstream reservoir. And a formula was recommended to apply to the Wanjiazhai Reservoir on the basis of the sediment deposition pattern discrimination formula. Besides, various flushing methods and methods reducing the sediment deposition were carried out and analyzed. Results indicated that when the inflow rate increased, the maximum particle diameter of the incipient sediment was larger. When the inflow rate reached 1200 m³/s, the diameter of the initial the incipient sediment varied from 0.015 mm to 0.094 mm. And the diameter range of the initial the incipient sediment was 0.014 mm–0.094 mm, when the inflow rate was 1800 m³/s. When the inflow rate reached 2500 m³/s, the diameter of the initial the incipient sediment varied from 0.010 mm to 0.094 mm. Notably, all sediment were discharged from the reservoir. Moreover, the sediment of the reservoir was flushed at a flow rate of 1200 m³/s–1800 m³/s under the premise of meeting the upstream water storage.