As an efficient and environmentally friendly method of delivering solid particles, the transport of liquid–solid slurry through a pipeline has attracted considerable attention. However, the flow characteristics of the slurry in large-diameter pipes, especially multi-sized slurry, are far from fully understood. In this study, an Eulerian multiphase model is applied to investigate single- and multi-sized slurry flows in horizontal pipes. The results show that the pipe diameter has a distinct effect on the particle distribution and that the flow properties of multi-sized slurry are different from those of single-sized slurry. In the 900-mm pipe, the variations in the solid concentration and velocity distributions of single-sized slurry are significantly affected by the particle size and efflux concentration but display weak dependence on the mixture velocity. The total particle concentration profile of the multi-sized slurry becomes relatively symmetric in the upper half of the pipe and highly asymmetric in the lower half with increasing mean particle size. The pressure drop per meter of the single-sized slurry first decreases and then increases with increasing particle size, and the pressure drop of the multi-sized slurry containing coarse particles is much higher than that of the single-sized slurry under the same working conditions.

Pulsed waterjets are widely used in exploitation of fossil fuels for their high efficiency. With the aim to further clarify the impact performance of Helmholtz self-excited oscillation waterjets (HSEOW), numerical and experimental studies were conducted. The morphological characteristics of the erosion surfaces between conical and HSEOW nozzles were compared and the cavitation evolution was obtained. Results show that the cavitation damage caused by the HSEOW nozzle on the specimen was mainly caused by the jet cavitation cloud under submerged conditions. The cavitation effect produced by the HSEOW nozzle had a much greater destructive effect than that of a conical nozzle. The mass loss caused by HSEOW nozzles increased first with the increase of standoff distance, then decreased rapidly after reaching the maximum value. Moreover, the density of holes and the damage intensity weakened with the increase of radial distance. A dimensionless cavity length of 2 and a dimensionless cavity diameter of 8 was the optimal structure that led to maximum mass loss. These results provide a further understanding of cavitation mechanism which leads to the impact performance of pulsed water jets and optimal working parameters in the field of energy exploitation.

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.

This study investigates the force and heat transfer characteristics of oblate spheroidal particles in gas–solid two-phase flows near walls, addressing the influence of particle orientation, shape, Reynolds number, and particle–wall distance. These factors are critical in industrial processes such as pneumatic transport and crop drying, as well as in natural phenomena. Utilizing the Euler–Lagrangian model and large eddy simulation (LES), we simulated flow fields and heat transfer under various conditions. The results indicate that at Re = 500, turbulence mitigates wall interference, leading to a 14.4% increase in the Nusselt number (Nu). Particle orientation plays a crucial role in heat transfer, with Nu decreasing by 20% at = 90° due to restricted interstitial flow. A higher aspect ratio (Ar = 0.8) enhances heat transfer by 25% compared to a lower aspect ratio (Ar = 0.1). Additionally, increasing the particle–wall distance from H = 0.25$d_v$ to H = 0.5$d_v$ reduces wall-induced drag by 30%. The findings enhance the understanding of particle–fluid interactions near walls, providing a foundation for optimizing computational fluid dynamics models and improving industrial applications. Future work should consider additional variables such as particle roughness to further refine predictive capabilities. This study contributes to advancing theoretical and practical insights into non-spherical particle behaviors in complex flow environments.

Ship oil spill accident will lead to enormous hazards in the Three Gorges Reservoir area. The risk mitigation of the ship oil spill is significant to the stakeholder of the maritime safety administration. To study the risk evolution of the ship oil spill in the Three Gorges Reservoir area, the framework of ship oil spill risk evolution was proposed according to the general definition of the risk; then, risk evolutions were analyzed from the perspectives of expected probability, system constraints of accident developing, and possible harmful consequences based on accidents analyses, simulation experiments, and structural equation model analysis. The results indicate that the system constraints of accident developing, such as the quantity of oil spills, free evolution time, and wind and flow conditions, have significant impacts on risk evolution of the ship oil spill after the occurrence of an accident in the Three Gorges Reservoir area.