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The slurry pump, which forms the core equipment of the deep-sea mining (DSM) system, provides lifting power for the ore from the seabed to the sea level, which is crucial for the safety of coarse ore particle transportation. Velocity slip plays a significant role in revealing the migration of the pump particles. Therefore, this study analyzes the velocity slip in a slurry pump using the computational fluid dynamics–discrete element method (CFD-DEM) for the first time. The relationship between the pump head and velocity slip was proposed and verified in this study based on the velocity triangle and Euler equation of the solid-liquid two-phase flow in the impeller. The effects of different particle sizes on the velocity slip are compared in detail. According to the computational results, the head depends on the larger velocity slip of the impeller outlet and lower velocity slip at the inlet. The peak value of the velocity slip was significantly reduced, and the peak position of the velocity slip and zero-point position moved backward for particle sizes ranging between 5-15 mm. This study provides a reference for the problems of particle migration and velocity slip in slurry pumps.

Slurry transport pumps, the central equipment of deep-sea mining (DSM) systems, provide the lifting power required for lifting mineral ores from the seafloor to the surface. The current technical challenges are associated with transport security and the economic aspects of coarse ore particles in pumps and pipelines. This paper focuses on the transportation characteristics of slurry pumps and uses theoretical methods, numerical calculations, and experimental methods to identify a feasible working mode. The geometric parameters of impeller channels in pump hydraulics significantly influence the migration properties of particles which in turn affects the overall security and economy of the system. The ratio of the impeller cross-sectional area F2/F1 (F1: cross-sectional area of the impeller outlet; F2: cross-sectional area of the impeller inlet) affects the particle passing capacity but negatively impacts pump efficiency. The percent of particles in the excellent passage interval of 0.2 s to 0.25 s increases from 25 to 43% when the number increases from 1.57 to 2.51. The pump behavior increases of the head by 5–10 m, and the efficiency decreases by 5–10%. So, the recommended span of F2/F1 is 1.57–2.00, and satisfying particle passing ability and efficiency can be achieved in this range. This study can provide a reference for the commercial transportation of slurry ores for deep-sea mining systems.

Increasing rain levels can easily destabilize and destroy particulate matter in mountainous areas, which can cause natural disasters, such as debris flow and landslides. Constitutive equations and numerical simulation are the theoretical bases for understanding the behavior of these disasters. Thus, this study aimed to investigate the impact of the debris flow and its entrainment behavior on gully bed sediments. We adopted a coupled analysis method based on elastic–plastic constitutive equations by considering the elasto-plasticity of slurry and the elastic characteristics of debris materials. The coupled method consisted of smooth particle hydrodynamic (SPH), discrete element method (DEM), and finite element method (FEM) (SPH–DEM–FEM). SPH particles represented fluid, DEM particles denoted solid immersed in fluid, and FEM elements represented the terrain and structures. The coupling analysis model was used to simulate the coupling contact of solid, liquid, and structures and to describe the entrainment behavior between solid and liquid phases. The model feasibility was verified by comparing the basic simulation results with experimental values of the dam break model and the rotating cylindrical tank model. The coupled model was then combined with the data management and modeling of geographic information system to simulate the 2010 Yohutagawa debris flow event. Finally, we explored the influence of debris shape-related parameters on the debris flow erosion entrainment process.

Ground collapse is a common urban geological disaster mainly triggered by the leakage of underground drainage pipe. To reproduce the process of underground cavity formation and development and investigate the formation mechanism of ground collapse, physical model tests and CFD–DEM-coupled numerical simulations are conducted in this study. Based on the monitored data of the vertical displacement of the ground surface and the soil pressure variation near the leakage point, the process of ground collapse can be divided into three stages: initial stabilization stage, slow subsidence stage, and the collapse stage. It is observed that the plane shapes of the collapse pits are almost semicircle, and their sizes are closely related to groundwater level, defect size and buried depth of pipe. This study reproduces the process of ground collapse experimentally and numerically, and basically reveals the mechanism of ground collapse induced by underground drainage pipe leakage.

Since solid particles suspended in the fluid can cause wear in centrifugal pumps, intensive attention has been focused on the numerical prediction for the wear of flow parts in centrifugal pumps. However, most numerical studies have focused on only one wear model and a sphere particle model. The impact of particle shape on the wear of flow parts in centrifugal pumps is under-studied, particularly considering abrasive and impact wear simultaneously. In this work, the Computational Fluid Dynamics (CFD)-Discrete Element Method (DEM) coupling method with an abrasive and impact wear prediction model was adopted to study the wear characteristics of a centrifugal pump. Moreover, four regular polyhedron particles and a sphere particle with the same equivalent diameter but different sphericity were mainly analyzed. The results demonstrate that more particles move closer to the blade pressure side in the impeller passage, and particles tend to cluster in specific areas within the volute as sphericity increases. The volute suffers the principal wear erosion no matter what the shapes of particles and wear model are. Both the impact and abrasive wear within the impeller occur primarily on the blade leading edge. The pump’s overall impact wear rate decreases first and then increases with particle sphericity rising, while the pump’s overall abrasive wear rate grows steadily.

In the process of oil and gas drilling, the blowout preventer (BOP) serves as the last line of defense before wellhead loss of control, and its sealing reliability is of critical importance. However, under the erosion of high-pressure sand-containing fluids, the sealing components of the BOP are prone to failure, resulting in long-slit-type leakage ports, which seriously threaten well control safety. In response to the current lack of theoretical guidance for emergency plugging process parameters, this paper adopts the coupled computational fluid dynamics and discrete element method (CFD-DEM) to establish a numerical model for the plugging of long-slit-type gaps with particles under blowout conditions. The migration and bridging plugging behaviors of three typical shaped particles, namely spherical, cylindrical, and square, under different sizes, concentrations, and pump injection rates are systematically studied. The results indicate that particle transport within the wellbore can be divided into an initial transport stage dominated by jet diffusion and a plugging-structure formation stage dominated by bridging and particle accumulation. When the particle size exceeds the slit width, cylindrical particles exhibit comparatively better plugging performance under the conditions considered in this study. For a long-slit leakage channel with a width of 5 mm, the combination of cylindrical particles with an equivalent diameter of 6 mm, a particle volume concentration of 20%, and a pumping rate of 2.4 m3/min demonstrated relatively favorable overall plugging performance. The particle concentration mainly affects the bridging time, and the bridging time tends to stabilize when the concentration reaches 20%. The higher the pump injection rate, the earlier the particles reach the gap opening, but it has little impact on the final plugging effect. This study provides a scientific basis for the optimization of emergency plugging process parameters after BOP sealing failure, filling the gap in the research on the plugging mechanism of equipment leakage under blowout conditions.

Since various foreign bodies can cause clogging and wear in single-channel pumps, considerable attention has been focused on the numerical study of solid-liquid flows in the single-channel pump. However, conventional numerical simulation cannot responsibly assess the significant effect of the particle material properties, inter-particle collision, and size on the pump. In consideration of the particle features and behaviors, the Computational Fluid Dynamics (CFD)-Discrete Element Method (DEM) coupling method was applied for the first time to simulate the solid-liquid flows in a single-channel pump. The results showed that the smaller particles possessed a wider velocity distribution range and velocity peak, while the larger particles exerted a greater contact force. Additionally, the pie-shaped particles had the most severe collisions, and spherical particles had the least in total. Furthermore, the hub and shroud wall suffered a minor contact force, but the blade and volute wall both sustained a considerable contact force. This paper could present some supply data for future research on the optimization of a single-channel pump.

The coupling of the finite element method and the discrete element method is one of the powerful approaches for simulating tire-sand interaction dynamics. However, the computational cost is significantly heavy for the models with a huge number of sand particles and fine meshes of the tire for the accurate contact detection. In this study, by introducing the arbitrary Lagrange–Euler (ALE) formulation, an efficient GPU-based ALE-DEM coupling method is proposed for simulating tire-sand interaction dynamics. Firstly, based on the ALE method and absolute nodal coordinate formulation (ANCF), the tire is discretized by the ALE-ANCF shell elements, and an incompressibility Mooney-Rivlin constitutive model is employed. A kinematic constraint equation with a material flow velocity is established to describe the relationship between the rigid rim and the flexible tire tread. By utilizing the ALE method, fine meshes of the tire tread are used on the contact region to obtain a detailed distribution of contact stress and strain, while coarse meshes are used on the other non-contact region to save computational time. Secondly, the sand particles are modeled by the DEM. Thirdly, for contact detection between finite elements and particles, an efficient global search algorithm based on the ALE method and an improved local search algorithm are proposed. Finally, the computational framework of the ALE-DEM coupling method based on GPU parallelization is established for the tire-sand system. Three numerical examples are presented to validate this method and the tire-sand interaction dynamics is simulated and comparatively studied.

To address the challenge of suppressing low-frequency vibrations in offshore wind turbine towers under complex environmental loads, this paper innovatively proposes a pendulum-tuned particle damper (PTPD). This design combines the high space utilization efficiency of pendulum structures with the broadband energy dissipation advantages of particle damping. A four-degree-of-freedom coupled tower-PTPD model and its Lagrangian equations of motion were established. Using the Finite Element-Discrete Element (FEM-DEM) coupling method, the effects of pendulum length and particle diameter on vibration suppression performance were systematically studied under three wind load conditions. Simulation results show that under Condition 1, a PTPD with a 3.50 m pendulum length filled with 200 mm iron-based particles achieves a peak vibration reduction rate of 58.1%, significantly reducing the tower’s vibration acceleration amplitude. A 1:65 scaled model was designed and tested, demonstrating that a combination of 625 mm pendulum length and 10 mm particles achieved a 58.0% vibration reduction rate. This validates the parameter optimization principles derived from simulations and provides an effective solution for anti-fatigue design of offshore wind turbines.

A multiphase model of hydrothermal liquefaction (HTL) using the computational fluid dynamics coupling discrete element method (CFD-DEM) is used to simulate biocrude oil production from sludge flocs in a continuous stirred tank reactor (CSTR). Additionally, the influence of the agitator speed and the slurry flow rate on dynamic biocrude oil production is investigated through full transient CFD analysis in a scaled-up CSTR study. The kinetics of the HTL mechanism as a function of temperature, pressure, and residence time distribution were employed in the model through a user-defined function (UDF). The multiphysics simulation of the HTL process in a stirred tank reactor using the Lagrangian–Eulerian (LE) approach, along with a standard k-ε turbulence model, integrated HTL kinetics. The simulation accounts for particle–fluid interactions by coupling CFD-derived hydrodynamic fields with discrete particle motion, enabling prediction of individual particle trajectories based on drag, buoyancy, and interphase momentum exchange. The three-phase flow using a compressible non-ideal gas model and multiphase interaction as design requirements increased process efficiency in high-pressure and high-temperature model conditions.