Pulsed waterjet can break rocks effectively by taking advantage of the water hammer effect, and is thus widely used in mining, petroleum, and natural gas fields. With the aim to further clarify the flow field characteristics of pulsed jets induced by a Helmholtz oscillator, large eddy simulation was conducted under different operating pressures. The velocity distribution, mean flow field, and the coherent structure were examined using the oscillators of different cavity lengths and diameters. The results clearly showed that the major frequency of jet pulsation gradually increased with the increase of operating pressure. A stable periodic velocity core was formed at the outlet of the Helmholtz oscillator, while the external flow field was subjected to periodic impact. As a result, the ambient fluid was strongly entrained into the jet beam. With the increase of the cavity length, the length of the core segment decreased while the energy loss caused by the cavity increased, which was also accompanied by a rapid attenuation of the axial velocity at the jet outlet. The coherent structure of the jet in the oscillator with small cavity diameter was more disordered near the nozzle outlet, and the vortex scale was larger. The effect of cavity diameter can be reflected in the feedback modulation of the jet in the cavity. Compared with the conical nozzle, the length of the core section of the jet was shorter, but the jet had better bunching, a smaller diffusion angle, and better mixing performance. These results provide a further understanding of the characteristics of pulsed water jet for better utilizations in the fields of energy exploitation.

The mud pump water sealing system (MPWSS) is important in the efficient operation and prolonged service life of the cutter suction dredger’s (CSD) mud pump. Considering that the underwater pump operates underwater and the shaft seal water pressure sensor is prone to failure, a hybrid deep learning model MCNN transformer is proposed to predict the underwater pump shaft seal water pressure in the event of sensor failure. This paper uses big data from the dredging project to deeply excavate the relationship between the shaft end sealing water pressure and other construction data by combining experience and artificial intelligence, and then uses multi-scale convolutional neural network (MCNN) to reconstruct the data, highlighting the time series characteristics of the multi-scale data were then input into the transformer model for prediction, and compared with a single MCNN, transformer model and four other neural networks. Finally, the cutter suction dredger “Hua An Long” was selected as an application research case; experimental comparisons were conducted on seven different models to verify the accuracy and applicability of the MCNN-transformer model.

The water-lubricated bearing plays a crucial role in the ship propulsion system, significantly impacting vessel safety. However, under the harsh working conditions of low-speed and heavy-load, the lubrication state of water-lubricated bearings is usually poor, leading to serious friction and wear. To improve the tribological performance of composites and reduce friction, three short fibers (ultra-high-molecular-weight polyethylene fibers, basalt fibers, and bamboo fibers) with the same mass fraction (5%) were added into the melted thermoplastic polyurethane (TPU). The tribological behavior of these three composites under different loads and rotation speeds was investigated using the CBZ-1 friction and wear tester. Through the comprehensive analysis of the friction coefficient, the wear mass loss, and the surface morphology, it was confirmed that the filled fiber positively affected the tribological performance of thermoplastic polyurethane materials. The experimental results indicated that basalt fiber significantly improved the tribological performance of TPU, and the friction coefficient of the sample was only 0.088 under the working conditions of 0.5 MPa and 250 r/min, which was 70.57% lower than that of pure TPU material. And in all the tests, the minimum wear of the basalt fiber-reinforced composite is only 0.4 mg, which is also the smallest of all the materials under all conditions, and a decrease of 98.69% compared to TPU. Under high loads, ultra-high-molecular-weight polyethylene fiber and bamboo fiber-reinforced composites have smoother surfaces and exhibit better tribological properties. This study provides an experimental foundation for tribological performance enhancement for environmentally friendly, water-lubricated bearing composites.

In dredging operations, the efficient transportation of dredged materials presents a significant and intricate challenge. This study focuses on the motion and resistance characteristics of coarse-grained dredged materials during pipeline conveyance. A specialized simulation experiment platform was developed to investigate the horizontal pipeline transport of coarse-grained materials. The experimental design encompassed varying particle diameters, material volume concentrations, and mixed average flow rates to analyze the motion and resistance characteristics of these materials in horizontal pipelines. Three distinct particle beds were identified based on different coarse particle motion states. This study statistically analyzed the impact of the particle diameter and material volume concentration on the transport efficiency of coarse particle populations. The key findings indicate that the mixed mean flow rate significantly influences the transportation efficiency of coarse particle groups, whereas the particle diameter and material volume concentration have a minimal effect. Specifically, coarse particles with a diameter of 0.9 mm demonstrated optimal water flow following, and higher mixed mean flow rates correlated with increased transportation efficiency of the coarse particle group. The transition speed of the coarse particle group flow type was notably affected by the material volume concentration and particle diameter, exhibiting a linear relationship. Therefore, when the particle size of the dredged material increases or the concentration increases, the average flow rate of the mixture is appropriately increased to ensure that the flow pattern of the dredged material in the pipeline remains in a non-homogeneous suspended flow pattern, thereby improving the efficiency and stability of the transportation system. By optimizing the conveying characteristics of coarse-grained materials, the pipeline conveying efficiency can be improved and the risk of pipeline wear and clogging can be reduced, thus lowering engineering costs and energy consumption and promoting technological innovation in related industries. In addition, this research can enhance engineering safety, reduce resource waste and environmental pollution, promote sustainable development, and provide important theoretical support and practical guidance for emerging fields such as deep-sea mining and environmental engineering.

With the continuous development of the shipping industry, suction dredgers play a crucial role as functional vessels for channel dredging. The reamer, as the core component of a cutter suction dredger, significantly impacts the energy consumption of the entire vessel. Most suction dredger reamers are powered by three-phase asynchronous motors. To fully utilize the motor’s output power, there is an urgent need to design a constant power control system to ensure stable and consistent power output despite variations in system parameters. This paper proposes a fuzzy PID control algorithm to address the limitations of traditional PID control, such as slow and insufficient response times, in order to achieve smoother and faster reamer power regulation. The proposed control strategy is validated through both simulations and experiments. Results show that the fuzzy PID algorithm reduces overshoot by an average of 9.85%, rise time by 38.58%, and regulation time by 42%, compared to traditional PID control. Additionally, the fuzzy PID control demonstrates superior robustness in dynamic responses to system changes. Overall, the fuzzy PID control system outperforms traditional PID in maintaining constant power control of the reamer.