Explore the vast range of titles available.

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.

Existing cleaning devices for edible sunflower have a low cleaning efficiency, high cleaning loss rate, and high impurity rate; therefore, a wind-sieve-type cleaning device for edible sunflower harvesting was designed. According to the characteristics of dislodged objects, a vibrating screen for the device was designed, and the dislodged edible sunflower objects in the device were used for a mechanical analysis of the force conditions to determine the displacement of the different edible sunflower objects dislodged by the action of airflow. Using FLUENT-DEM gas–solid coupling simulation technology, the velocity of the flow field, the velocity vector, and the trajectory of the dislodged objects inside the cleaning device were analyzed, and the law of motion applied to the airflow and the dislodged objects inside the device was clarified. According to the results of the coupled simulation analysis, the key factors affecting the operation of the cleaning device were wind speed, vibration frequency, and amplitude. Based on the key factors of wind speed, vibration frequency, and amplitude, an orthogonal rotary combination test was carried out with the loss rate and impurity rate of cleaned grains as the evaluation indexes, and the test parameters were optimized to obtain the optimal combination of operating parameters of the device, which were as follows: wind speed: 30 m·s−1; vibration frequency: 8.44 Hz; and amplitude: 41.35 mm. With this combination of parameters, the seed loss rate and impurity rate reached 3.47% and 6.17%, respectively. Based on the optimal combination of operating parameters, a validation test was performed, and the results of this test were compared with the results of the test bench using this combination of parameters. The results show that the relative errors of the loss rate and impurity rate between the bench test and the simulation test were 3.45% and 3.07%, respectively, which are less than 5%, proving the reliability of the simulation analysis and the reasonableness of the design of the test bench.

The transmission effect refers to the migration of eroded fine particles between the neighboring gap-graded soil matrix, and its influence on suffusion is rarely investigated. A supplemental flow with incremental quantities of transmitted fine particles is implemented into a series of CFD-DEM coupling cases to simulate the different levels of transmission effect during the suffusion process. Macroscopic and microscopic impacts of the transmission effect on suffusion are analyzed in detail, including the percentage of eroded fine mass, the spatial distribution of residual particles, the evolution of velocity field & particle movements, and added fine particle migrations. Additionally, analysis of the force-chain network and anisotropic characteristics of specimens are examined from the micromechanical aspect. The numerical results indicate that the transmission effect has both enhancing and inhibitory impacts on suffusion. This work provides a novel perspective considering the suffusion process as a whole interactive system where the eroded fines of each soil matrix would exert an influence on its downstream matrix along the seepage path and contributes to further development of the phenomenological and micromechanical constitutive models of multifield and multiphase media.

Landslide-induced tsunami is a complex fluid–solid coupling process that plays a crucial role in the study of a disaster chain. To simulate the coupling behaviors between the fluid and solid, a graphics processing unit-based coupled smoothed particle hydrodynamics (SPH)-discrete element method (DEM) code is developed. A series of numerical tests, which are based on the laboratory test by Koshizuka et al. (Particle method for calculating splashing of incompressible viscous fluid, 1995) and Kleefsman et al. (J Comput Phys 206:363–393, 2005), are carried out to study the influence of the parameters, and to verify the accuracy of the developed SPH code. To ensure accurate results of the SPH simulation, the values for the diffusion term, particle resolution (1/25 characteristic length), and smoothing length (1.2 times of particle interval) are suggested. The ratio of the SPH particle size and the DEM particle’s diameter influences the accuracy of the coupling simulation between solid particles and water. For the coupling simulation of a single particle or a loose particle assembly (not contact each other) with fluid, this ratio should be smaller than 1/20; for a dense particle assembly, a ratio of smaller than 1/6 will be good.

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.

In this paper, a predictive model for simulating temporal behaviors of clayey sand during seepage-induced erosion has been developed by coupling discrete element method (DEM) with computational fluid dynamics (CFD). In this model, the particle–fluid coupling simulation is solved by a “fixed coarse-grid” scheme in 3D particle flow code (PFC3D), and the suffusion of clay matrix in the initiation of erosion is converted to a degradation process of bonding strength between particles according to a degradation law. The law is derived from the well-known shear stress threshold law dealing with soil internal erosion, which is based on two erosion parameters—the critical shear stress and the erosion coefficient. Then the degradation law is implemented in the CFD–DEM model via developing customized code using the Python language. The ability of the model to predict the interfacial erosion of soils is confirmed by two numerical tests. The results are seen to match the empirical criteria, such as revealing a clearly defined critical tangential shear stress, beyond which erosion occurs, and a positive correlation between the rate of erosion and the pressure gradient. It is believed that the numerical model is able to reproduce the time-dependent evolution process of seepage-induced erosion in clayey sand.

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.

Based on CFD-DEM (Computational Fluid Dynamics-Discrete Element Method) coupling method, the numerical simulation of solid-liquid two-phase flow in disc pump is carried out. After grid independence verification and simulation accuracy verification, the working condition of 1500rpm and 40m3/h is selected for calculation. It is found that with the increase of particle volume fraction, the total pressure difference between the inlet and outlet of the disc pump increases, the pressurization capacity of the impeller increases first and then decreases, and the volute bears more pressure energy conversion. The particles in the inlet pipe section of the disc pump sink under the influence of gravity. With the increase of particle volume fraction, the high-speed moving particles in the impeller and volute increase, and the particles carry more kinetic energy, which increases the total pressure difference between the impeller and volute of the disc pump, but the effect gradually weakens with the increase of particle volume fraction. The particles have various motion states in the pump, and show different motion trajectories due to various factors.

Landslide tsunamis are complex fluid–solid coupling processes that often cause enormous catastrophes. In this study, the smooth particle hydrodynamics (SPH) and discrete element method (DEM) coupling algorithms are used to simulate the tsunami which was induced by the 1963 Vajont landslide, Italy. In order to simulate the failure process of the landslide, a DEM numerical model is constructed based on the geological structure of the landslide, and contact parameters for the DEM particles are inverted according to the laboratory tests. Based on the numerical results, the whole process of the tsunami by the Vajont landslide is reproduced in detail. Comparisons show that the simulated motion and accumulating characteristics of the landslide, the climb-up and peak overtopping flow of the tsunamis, and the load on the dam by the tsunamis agree well with the published results. The simulation also indicates that the right bank slope of Vajont Dam is the major spillway of the flood, thereby significantly reducing the flow directly over the dam, which is helpful to stabilize the dam; and the concrete of the left abutment is damaged by the mixture flow of water and geomaterials with a higher velocity (approx. 35 m/s at the max.). The overtopping depth decreases from the north bank to the south bank. The maximum depth on the right abutment and the left abutment is approximately 80 and 65 m, respectively, lower than the reported estimation of ~ 150 m. This study shows that the coupled SPH–DEM method and the developed code—CoSim—work well for the analysis and research on landslide tsunami.

Overtopping failure of earthfill dams is a complex process that involves strong soil–water coupling and structural failure. Physically based numerical models are essential for characterizing the breach mechanism and the failure process. In this study, a dam-break model that considers the combined effects of seepage and overflow is proposed. This model simultaneously solves the governing equations for solid and fluid phases in two different sets of Lagrangian particles. The coupling between water and soil are, respectively, modelled with SPH and DEM particles by considering their interactions, including drag force, buoyancy and particle adhesion. The capillary force caused by the meniscus between soil particles is incorporated to characterize the saturation degree of the soil. The dam-break model is validated by simulating seepage through an earth dam, a small-scale dam-break test, and dam erosion progress. Finally, the proposed model is employed to simulate the overtopping failure of an earthfill dam. Numerical simulations show that the proposed numerical model is capable for capturing the salient features of dam breach. Moreover, some other soil–water coupling processes, such as reservoir water infiltration, dam slope erosion and collapse, breach development, and dam failure, can be predicted by this model as well.