Water‐exit is a hydraulic phenomenon induced when an object exists in a body of water. In the case of ship lifts, the hydrodynamic forces induced by the water‐exit of the chamber’s support beam may result in unsafe and unstable operating conditions and may even cause a loss of structural integrity. In this study, the water‐exit process of a simplified beam was investigated using an experimental–numerical approach. The experimental results revealed that three major stages occur during water‐exit: start‐up, flow‐around, and exit‐moment. Moreover, the maximum additional hydrodynamic load exerted on the beam during water‐exit occurred in the exit‐moment phase. Based on these results, a calibrated numerical method was employed to analyse the main factors affecting the maximum additional hydrodynamic load. The numerical results indicated that the additional load can be accurately predicted using two dimensionless parameters. These results may help evaluate the negative impacts of suction on a ship lift chamber and improve the technical support and operation of ship lifts.

Objects entering water, characterized by brief and high-peak impact forces, have been extensively investigated in scientific research. However, the specific water entry process during docking downstream of the launching ship lift chamber involves T-shaped beams entering the water at a constant velocity with a deadrise angle of zero degrees. The hydrodynamic load mechanisms during this process remain not well understood. This research investigated the hydrodynamic loads generated as T-shaped beams from ship lift chambers enter water. Physical model experiments delineated the water entry process into three distinct phases: the entry impact phase, the cavity phase, and the braking phase. Furthermore, numerical simulations, validated by physical models, were employed to explore the factors influencing impact and cavity forces during the water entry process. These findings led to the derivation of empirical formulas to calculate the impact and cavity forces. These results support the assessment of structural forces on ship lift chambers, thereby enhancing the technical support and operational efficiency of ship lifts.

Launching-type ship lifts are commonly used in navigational mountain rivers to realize river channelization and communicate different water systems. However, the complicated water–gas–solid coupling process incurred during the water exit of cavities beneath a ship chamber can strongly affect the stability of the chamber and even affect the ship lift operation. In this study, the water exit behavior of a generalized cavity model was investigated using an experimental–numerical approach. Both the air pressure and flow patterns during the water exit process were analyzed. The results demonstrate three different types of air pressure process in cavity exits. Based on the results, a series of relationships are proposed to predict the maximum negative pressure incurred in the water exit process. Moreover, a method was developed to determine the optimum ported area of the cavity regarding the absence of additional hydrodynamic loads. Furthermore, a classification system to typify the flow patterns manifesting in the cavity is proposed. It was found that the transition from a slug flow to a drop flow could be determined as a transition coefficient K equal to 1.

The propagation of secondary surges can lead to unexpected interaction events with navigation ships and downstream hydraulic structures; hence, they may cause navigation accidents and structural damage. In the present study, physical experiments were performed in a long water wave tank to study the evolution of breaking undular and breaking surges advancing in still water. Both free-surface and velocity measurements were conducted. It was observed that the transition from a breaking undular surge to a breaking surge occurred as the ratio of the mean water depth behind the surge to the still water depth equal to 1.68–1.71. Empirical expressions based on the experimental data were proposed to predict the wave amplitude and wave steepness of breaking undular surges. The unsteady flow results demonstrated that the normalized longitudinal velocity component beneath the surge front was governed mainly by the normalized free-surface elevation, independently of the surge type. Moreover, the maximum vertical velocity component during the surge front passage had a linear dependence on the vertical location. The present result provided new quantitative information on breaking undular and breaking surges advancing in still water.

The water saving lock layout plays a key role in addressing the navigation hydraulic problems with high dams. However, the study of the propagation and development of nonlinear long waves induced by ship-lock operation in a water saving basin has received less attention so far. Specially, the mechanisms governing the formation of secondary waves and the impact of these waves on the impoundments of the basin are still not fully understood. In the present study the entire evolution of a nonlinear long wave in a water saving basin was numerically simulated. The wave shape, wave celerity and wave force were analyzed. It was found that the leading edge of a long wave propagated along the water saving basin with a celerity which varied with time and space. Two distinct stages could be recognized and defined: a rapid acceleration phase characterized by a sharp increase in the celerity with propagation distance and a gentle acceleration phase where the long wave propagated in a more gradual manner. Moreover, the water surface slop of a long wave front equal to 0.045 could be used as an estimate of the occurrence of secondary waves. Furthermore, the present results highlighted the wave force on the impoundments of a water saving basin was controlled by wave nonlinearity. These results may provide theoretical guidance and technical support for the hydraulic design and operation of water saving locks.