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Granular flows of 200 μm particles and the pile formation in a flat-bottomed hopper and bin in the presence of air and in a vacuum were predicted based on three-dimensional numerically empirical constitutive relations using Smoothed Particle Hydrodynamics and Computational Fluid Dynamics methods. The constitutive relations for the strain rate independent stress have been obtained as the functions of the Almansi strain including the large deformation by the same method as Yuu et al. [1]. The constitutive relations cover the elastic and the plastic regions including the flow state and represent the friction mechanism of granular material. We considered the effect of air on the granular flow and pile by the two-way coupling method. The granular flow patterns, the shapes of piles and the granular flow rates in the evolution are compared with experimental data measured under the same conditions. There was good agreement between these results, which suggests that the constitutive relations and the simulation method would be applicable for predicting granular flows and pile formation with complex geometry including free surface geometry. We describe the mechanisms by which the air decreases the granular flow rate and forms the convergence granular flow below the hopper outlet.

With the development of urbanization and the application of renewable energy, wind turbine is becoming an important approach for wind energy reservation and utilization. This study provides a numerical investigation on understanding the surface pressure distribution, flow characteristics and dynamic responses of a parked straight‐bladed vertical axis wind turbine (VAWT), which is helpful for its design. Together with the two‐way coupling method between simulation platforms such as STAR‐CCM+ and ABAQUS, the SST k‐ω turbulence model is used to obtain the surface pressure and surrounding flow of the VAWT, and the finite element method is used to obtain the dynamic responses of its structural components. The results show that the contours of the pressure distribution on the windward surface of the VAWT are similar even under a few different conditions, and the deformation of the VAWT can lead to changes in surface pressure; the turbulent flow characteristics and the wake effect become more obvious as the wind velocity increases; the blades and support arms of the VAWT need to be reinforced during the design, and the effect of the parked condition on the dynamic responses of the VAWT can be neglected. The two‐way coupling method as well as the numerical simulation results is expected to provide references for the design of VAWTs subjected to coming wind action. This study provides a numerical investigation on understanding the surface pressure distribution, flow characteristics, and dynamic responses of a parked straight‐bladed vertical axis wind turbine with the two‐way coupling method between STAR‐CCM+ and ABAQUS. The research methods as well as the simulation results are expected to provide references for the design of vertical axis wind turbines subjected to coming wind action.

A new method for two-way fluid-particle coupling on an unstructured mesoscopically coarse mesh is presented. In this approach, we combine a (higher order) finite-element method (FEM) on the moving mesh for the fluid with a soft sphere discrete-element method for the particles. The novel feature of the proposed scheme is that the FEM mesh is a dynamic Delaunay triangulation based on the positions of the moving particles. Thus, the mesh can be multi-purpose: it provides (i) a framework for the discretization of the Navier-Stokes equations, (ii) a simple tool for detecting contacts between moving particles, (iii) a basis for coarse-graining or upscaling, and (iv) coupling with other physical fields (temperature, electromagnetic, etc.). This approach is suitable for a wide range of dilute and dense particulate flows, because the mesh resolution adapts with particle density in a given region. Two-way momentum exchange is implemented using semi-empirical drag laws akin to other popular approaches; for example, the discrete particle method, where a finite-volume solver on a coarser, fixed grid is used. We validate the methodology with several basic test cases, including single- and double-particle settling with analytical and empirical expectations, and flow through ordered and random porous media, when compared against finely resolved FEM simulations of flow through fixed arrays of particles.

In this paper, we propose a reduced-order modeling strategy for two-way Dirichlet–Neumann parametric coupled problems solved with domain-decomposition (DD) sub-structuring methods. We split the original coupled differential problem into two sub-problems with Dirichlet and Neumann interface conditions, respectively. After discretization by, e.g., the finite element method, the full-order model (FOM) is solved by Dirichlet–Neumann iterations between the two sub-problems until interface convergence is reached. We then apply the reduced basis (RB) method to obtain a low-dimensional representation of the solution of each sub-problem. Furthermore, we apply the discrete empirical interpolation method (DEIM) at the interface level to achieve a fully reduced-order representation of the DD techniques implemented. To deal with non-conforming FE interface discretizations, we employ the INTERNODES method combined with the interface DEIM reduction. The reduced-order model (ROM) is then solved by sub-iterating between the two reduced-order sub-problems until the convergence of the approximated high-fidelity interface solutions. The ROM scheme is numerically verified on both steady and unsteady coupled problems, in the case of non-conforming FE interfaces.

Purpose This study aims to investigate the influence mechanism of thermal-mechanical deformations on the CO2 mixture gases dry gas seal (DGS) flow field and compare the deformation characteristics and sealing performance between two-way and one-way thermal-fluid-solid coupling models. Design/methodology/approach The authors established a two-way thermal-fluid-solid coupling model by using gas film thickness as the transfer parameter between the fluid and solid domain, and the model was solved using the finite difference method and finite element method. The thermal-mechanical deformations of the sealing rings, the influence of face deformation on the flow field and sealing performance were obtained. Findings Thermal-mechanical deformations cause a convergent gap between the two sealing end faces, resulting in an increase in the gas film thickness, but a decrease in the gas film temperature and sealing ring temperature. The axial relative deformations of rotating and stationary ring end faces caused by mechanical and thermal loads in the two-way coupling model are less than those in the one-way coupling (OWC) model, and the gas film thickness and leakage rate are larger than those in the OWC model, whereas the gas film stiffness is the opposite. Originality/value This paper provides a theoretical support and reference for the operational stability and structural optimization design of CO2 mixture gases DGS under high-pressure and high-speed operation conditions.

The presence of particles with a small but finite size, suspended in viscous fluids with low volumetric concentrations, is observed in many applications. The present study focuses on the tridimensional and incompressible lid-driven flow of Newtonian fluids through the application of the immersed boundary method and the Euler–Lagrange approach. These methods are used to numerically predict three-dimensional particle motion by considering nearly neutrally buoyant conditions as well as all relevant elementary processes (drag and lift forces, particle rotation, particle–wall interactions, and coupling between phases). Considering the current stage of the numerical platform, two coupling approaches between phases are considered: one-way and two-way coupling. A single particle is inserted in the cavity after steady-state conditions are achieved. Its three-dimensional motion is obtained from numerical simulations and compared with research data, considering the same conditions, evidently showing that the particle trajectory follows the experimental data until the first collision with a solid surface. After this first contact, there is a deviation between the results, with the two-way coupling results better representing the experimental data than the one-way coupling results. The dimensionless forces’ peaks acting on the particles are associated with the relative velocity of the particle near the wall–particle collision position. In terms of magnitude, in general, the drag force has shown greater influence on the particle’s motion, followed by the rotation-induced and shear-induced lift forces. Finally, a special application is presented, in which 4225 particles are released into the domain and their dynamic is evaluated throughout dimensionless time, showing similar behavior for both couplings between phases, with variations in local concentrations observed in certain regions. The mean square displacement used to quantify the dispersion evolution of the particles showed that the particulate flow reaches an approximately homogeneous distribution from the moment of dimensionless time tU/S = 130.

In this research, a two-way coupling of discrete phase model is developed in order to track the discrete nature of aluminum oxide particles in an obstructed duct with two side-by-side obstacles. Finite volume method and trajectory analysis are simultaneously utilized to solve the equations for liquid and solid phases, respectively. The interactions between two phases are fully taken into account in the simulation by considering the Brownian, drag, gravity, and thermophoresis forces. The effects of space ratios between two obstacles and particle diameters on different parameters containing concentration and deposition of particles and Nusselt number are studied for the constant values of Reynolds number (Re = 100) and volume fractions of nanoparticles (Φ = 0.01). The obtained results indicate that the particles with smaller diameter (dp = 30 nm) are not affected by the flow streamline and they diffuse through the streamlines. Moreover, the particle deposition enhances as the value of space ratio increases. A comparison between the experimental and numerical results is also provided with the existing literature as a limiting case of the reported problem and found in good agreement.

Hydraulic pre-fracturing is a rock-weakening technique applied in hard-rock excavation. To investigate the effects of hydraulic pre-fracturing on crack propagation in excavation roadwalls and on the cutting loads experienced by excavation machine picks when cutting precracked rock, a two-way fluid–solid couplinproach (CFD–DEM) was employed to simulate the three-dimensional crack propagation process of a rock face under hydraulic fracturing. The results indicate that crack propagation under hydraulic fracturing evolves through four stages: (1) initiation of the primary crack; (2) further development of the primary crack, accompanied by the emergence of fine subsidiary cracks; (3) retardation of the primary crack growth, concurrent with propagation of secondary cracks; and (4) further expansion of secondary cracks. The influences of borehole aperture and injection pressure on crack propagation were analyzed; within the investigated ranges, increasing either aperture or injection pressure produced a nonlinear increase in crack development. When the hydraulic-fracture borehole diameter increased from 85 mm to 100 mm, the number of broken bonds increased by 56.2%; when the injection pressure increased from 25 MPa to 40 MPa, the number of broken bonds increased by 153.9%. The cutting force experienced by picks when cutting precracked rock decreased by 9.05% compared with cutting intact (non-precracked) rock; after precracking, the mean forces in the Z and Y directions decreased by 11.46% and 7.20%, respectively, whereas the mean force in the X direction increased by 5.49%. The findings provide reference data for the practical implementation of hydraulic pre-fracturing in hard-rock excavation.

Purpose Bulk material-handling equipment development can be accelerated and is less expensive when testing of virtual prototypes can be adopted. However, often the complexity of the interaction between particulate material and handling equipment cannot be handled by a single computational solver. This paper aims to establish a framework for the development, verification and application of a co-simulation of discrete element method (DEM) and multibody dynamics (MBD). Design/methodology/approach The two methods have been coupled in two directions, which consists of coupling the load data on the geometry from DEM to MBD and the position data from MBD to DEM. The coupling has been validated thoroughly in several scenarios, and the stability and robustness have been investigated. Findings All tests clearly demonstrated that the co-simulation is successful in predicting particle–equipment interaction. Examples are provided describing the effects of a coupling that is too tight, as well as a coupling that is too loose. A guideline has been developed for achieving stable and efficient co-simulations. Originality/value This framework shows how to achieve realistic co-simulations of particulate material and equipment interaction of a dynamic nature.

The slurry pump is one of the most important pieces of equipment in mineral transportation and separation systems, and it has complex two-phase flow characteristics and wear mechanisms. By employing numerical and experimental methods, the solid–liquid two-phase flow characteristics and wear patterns were investigated in this study. A two-way coupling discrete phase model (DPM) method was used to predict the flow pattern and the wear location and shows good agreement with the experimental observations. The pump performance characteristics of numerical results under pure water conditions were consistent with the experimental results. The effects of particle parameters and operating conditions on the internal flow field and wear were compared and discussed. The results show that the wear degree increased with the increase in volume flow rate and solid volume fraction. With the increase in particle size, the wear range at the impeller inlet became significantly smaller, but the wear degree became obviously larger. This study provides a basis for reducing the wear and improving the hydraulic performance of slurry pumps.