Solid-liquid Two-phase Flow Model Research Articles

Study on Proppant Transport and Placement in Shale Gas Main Fractures

In this paper, based on the background of a deep shale reservoir, a solid–liquid two-phase flow model suitable for proppant and fracturing fluid flow was established based on the Euler method, and a large-scale fracture model was established. Based on field parameters, a proppant transport experiment was conducted. Then, on the basis of the experimental fracture model, proppant transport simulation under different influencing factors was carried out. The results show that the laboratory experiment was in good agreement with the simulated results. The process of proppant accumulation in fractures can be divided into three stages according to the characteristics of sand banks. The displacement mainly affects the sedimentation distance of the proppant in the first stage, and the viscosity of the fracturing fluid represents the strength of the fluid sand carrying performance. Compared with 40/70 mesh proppant, 70/140 mesh proppant is more easily fluidizable, the fracture width has less influence on proppant migration and placement, and the perforation location only affects the accumulation pattern at the fracture entrance, but has less influence on proppant placement in the remote well zone.

Study of solid-liquid two-phase flow model of drilling fluids for analyzing mud cake formation

Mud cake is formed by the accumulation of particles on the surface and inside of the well wall during the filtration of drilling fluids, which is multiply affected by reservoir types, composition of drilling fluids, and wellbore conditions. Numerical simulation can provide a more comprehensive study than experiments, but the usual single-phase models of drilling fluid is difficult to simulate the non-homogeneous characteristics of mud cake. In this paper, the calculation method of interactions between particles and the drag force on particles with different sphericity in non-Newtonian fluid are derived. Therefore, a solid-liquid two-phase flow model of drilling fluid that describes the motion of solid and liquid phases, respectively, is constructed to investigate the influences of their properties on the dynamic non-homogeneous formation of mud cake in the real pore space of cores. The results show that the flow volume and velocity of the liquid phase are affected by the tortuosity of the pore channel, which in turn affects the entering number of particles. The influences of particle parameters on the entering number are radius > morphology > release velocity > free energy of the surface > density > release concentration. The solid-liquid two-phase flow model can refine the analysis to formulate the most applicable drilling fluids, which will significantly reduce the exploration and validation work of plugging experiments.

Analysis of Sediment and Water Flow and Erosion Characteristics of Large Pelton Turbine Injector

Based on the solid–liquid two-phase flow model, SST k-ω model, and Lagrangian equation model of particle motion, numerical simulations of the sediment–water flow in the injector of a large Pelton turbine were conducted. The distribution rules of pressure, velocity, erosion rate, and erosion location of the injector were obtained by analyzing the sediment–water flow characteristics and sediment erosion distribution characteristics of the injector. The results revealed that the velocity distribution trend of the water inside the cylindrical jet exhibited a nonlinear distribution, and the phenomenon of “velocity deficit” occurred at the end of the needle guide and needle tip, resulting in a decrease in the jet quality of the injector. The sediment particle diameter affected the erosion rate of the needle and erosion location of the needle and nozzle port ring. This study provided guidance for sediment erosion analysis and the prediction of the utility of large Pelton turbines.

Numerical Simulation on Erosion Wear Law of Pressure-Controlled Injection Tool in Solid Fluidization Exploitation of the Deep-Water Natural Gas Hydrate

The pressure-controlled injection tool (PCIT) is the key equipment in the process of high-pressure water jet fragmentation in the solid fluidization exploitation of deep-sea natural gas hydrate (NGH). The internal flow field erosion wear numerical simulation model of PCIT is established through computational fluid dynamics software to study the influence law and main factors of the drilling fluid erosion wear of PCIT. The influence laws of different drilling fluid physical parameters and different structural parameters on PCIT erosion wear were analyzed based on the Euler–Lagrangian algorithm bidirectional coupled discrete phase model (DPM) and the solid–liquid two-phase flow model. The results show that the easily eroded areas are the cone of the sliding core, the plug transition section, the plug surface, and the axial flow passage. The sliding core inlet angle and solid particle size are the main factors affecting the PCIT erosion rate. When the inlet angle of the sliding core is 30°, the diameter of solid-phase particles in drilling fluid is less than 0.3 mm, and the erosion degree of the PCIT could be effectively reduced. The research results can provide guidance for the design and application of the PCIT and advance the early realization of the commercial exploitation of hydrate.

基于固液两相流的有机肥固液混合施肥装置分析与设计

Organic fertilizer applicator currently has poor versatility toward different properties. A solid-liquid mixed fertilizer device is designed based on the numerical simulation method of solid-liquid two-phase flow. Based on the parameters analysis and viscosity measurement of different organic fertilizer particles, the ribbon-screw type agitator was selected as the basic structure. Using Box-Behnken, three test factors including agitator speed, the mixture ratio of fertilizer and water, agitator height were determined, the agitator was optimized with the test evaluation indexes, the density variation coefficient, and agitator shaft power on 10 mixing planes in the agitator. The result showed that the rotating speed was 80 r/min, the mixing ratio of fertilizer and water was 1.2, and the agitator height was 700 mm, the working parameter combination is optimal. A coarse particle solid-liquid two-phase flow model of the fertilizer discharge pump was established, to obtain the external characteristic curve of the fertilizer pump and analyse the influence of different mixing ratios of fertilizer and rotation speed on the fertilizer pump. In order to prevent the separation of fertilizer and water and achieve better effect, 1140 r/min was comprehensively determined as the working speed of the fertilizer pump. The strength of the agitator meets the working requirements. The solid-liquid deep fertilizer device text bench for organic fertilizer was set up under the optimal working parameters, the result shows that the research results can provide a reference for the design of organic fertilizer solid-liquid mixing fertilizer applicator.

Numerical Simulation of Fluid Flow Features of Mechanical Mixer with Automatic Variable Frequency Control

For many engineering fields, it is of practical significance to construct and reasonably simplify the solid-liquid two-phase flow model in the cylinder of mechanical mixer. However, the existing studies have not considered how the control technology affects the fluid features in the mixer. From the angle of automatic variable frequency control, this paper carries out a numerical simulation of the fluid flow features in mechanical mixer. Firstly, the authors constructed the system structure for the mixer with automatic variable frequency control, and summarized the basic devices and the number of input/output points of the system. Then, the relationship between the force energy and control frequency of the mixing cylinder was detailed. Afterwards, the Euler-Euler two fluid model was introduced to numerically simulate the solid-liquid two-phase flow in the cylinder of the mixer, which contains both solid particles and liquid, followed by the establishment of control equation, the drag model, and the turbulence model. The proposed model was proved effective through experiments. The research findings provide a reference for the relevant research and the optimal design of the drive module of mixers.

Study on hydraulic sand suction performance of suction cutter

The sand absorption performance of the suction cutter affects the sand removal effect of the oil-water separator to a great extent. The bottom flow field model of the separator tank with the suction cutter is established by means of numerical simulation, which includes the determination of the applicable solid-liquid two-phase flow model and the establishment of the basic fluid dynamics equation in line with the reality. After Gambit was used to divide the mesh, Fluent software was used to analyze the influence of sand suction cutter placement Angle, sand suction velocity, sand suction distance and other factors on sand suction performance. It is found that with the adjustment of many factors, the hydraulic sand absorption performance of the suction cutter changes obviously.

Numerical investigation of ripple in oscillating water tank by DEM-MPS coupled solid–liquid two-phase flow model

The height of ripples, representing roughness in the shallow-water area, is an important factor in the prediction of coastal processes. However, the characterization of ripples under violent flow conditions has proven challenging. For instance, in shallow water in the swash zone, significant water fluctuation occurs owing to interactions between the up-rush and down-rush of waves. Because such phenomena shows strong nonlinearity, sufficient knowledge of swash-ripple formation remains lacking. In this study, experiments generating ripples in an oscillating water tank are conducted. Furthermore, numerical simulation using the three-dimensional DEM-MPS coupled method is performed. By comparing numerical and experimental results, validation of the present numerical simulation is demonstrated, followed by an investigation of the mechanics of ripple formation. Numerical results show that not only the drag force but pressure gradient force resulting from the water surface gradient considerably affect sand-particle motion, revealing the need for accurate evaluation of the free surface flow. Moreover, pressure gradient force plays an important role in the ripple formation process, so it should be reflected in the numerical model for ripple simulations.

Research on the Deposition Characteristics of Integrated Prefabricated Pumping Station

Based on the discrete phase model (DPM) solid–liquid two-phase flow model and MATLAB image processing technology, an integrated prefabricated pumping station was taken as the research object to study deposition characteristics under different flow rates, different particle diameters, and different liquid levels. Considering the incomplete symmetry of the internal flow of the prefabricated pumping station, deposition characteristics of the prefabricated pumping station under single/double pumps were also analyzed. Double pumps were symmetrically distributed in the integrated prefabricated pump station, and the movement trajectories of particles at the bottom of the pump pit under the closing inlet valve were measured through the use of a high-speed photography experiment. Results showed that with the increase of the flow rate, the deposition rate of the separated prefabricated pumping station decreased. With an increase of the particle diameter, the movement of particles was farther away from the vertical barrier weir. In the range of particle diameter of 6 to 10 mm, the deposition rate decreased with the increase of the particle diameter. With the increase of the liquid level, the deposition rate decreased, first, and then increased again. In the case of the single pump operation, the deposition rate of the right pump operation was smaller than that of the left pump operation. The variation of the deposition rate when the right pump operated was basically the same as that when the dual pumps operated. The movement path of particle N1 was longer. With the decrease of the flow rate and the increase of the particle diameter, the following feature of the particle decreased, and it was easier to impact the walls and edges, which caused long-term deposition. The research results could provide some suggestions for the design of anti-deposition performance of prefabricated pumping station.

Contribution of free iron particles to PD characteristics in flowing transformer oil at DC voltages

Partial discharge (PD) characteristics of the transformer oil contaminated by metallic particles are relevant to particle movement. The motion characteristics of the particles will change when the oil flows, and hence, the PD characteristics differ from that in stationary oil. In this study, the PD characteristics were investigated at direct current voltages, and the particle trajectories were observed simultaneously. It was found that the number of discharges obviously decreased, but the discharge magnitude slightly increased as the oil flow speed increased. To explain the changes in the PD characteristics, a solid-liquid two-phase flow model was established to simulate the trajectories and the electric field distribution around particles. The experimental observations partially verified the simulated trajectories, which includes two stages, namely sedimentation and the subsequent oscillation-collision stage. With the increase of the flow speed, the sedimentation particles decreased, and the horizontal spacing between two adjacent particle-electrode collisions elongated. Therefore, the total collisions became infrequent, which reduced the number of discharges. Moreover, the higher the flow speed was, the slower the particle approached an electrode. Considering the discharge time lag, the distance between the particle and the electrode at the instant of the PD would increase, which increased the discharge magnitude.

A unified transient solid-liquid two-phase flow model for cuttings transport- modelling part

A unified transient model is presented for predictions of flow pattern transitions, pressure gradient, solid particle concentration in solid-liquid two-phase flow. The transient mechanistic model is based on the conservation of mass and momentum and coupled with flow pattern prediction methods. Changes of flow patterns are reflected by assigning certain terms to zeros in the general equations and changing the number of equations. Thus, the model can be automatically adjusted for flow patterns in transient simulation.A semi-implicit approach is used to solve the model. The velocities and pressures are solved implicitly based on the momentum conservation equations and the solids concentrations are updated explicitly based on the mass conservation equations.The model is validated by conducting a series of experimental tests on a full scale flow loop (0.2 × 0.11 × 25 m). The validation of the transient simulation includes the validation of the transient build-up stage and the validation of the cuttings volumetric concentration at fully developed stage. Results found that increase of the flow rate significantly reduces the build-up time, and effects of pipe rotation vary at different inclined angles. The effect of inclination angle on solids profile build-up is similar to the effects of well inclination angle on steady state cuttings concentration. Below 60°, the build-up time increases significantly as the well inclination angle increases. When the well inclination angle goes to over 60°, the effects of well inclination angle become insignificant.

Three-dimensional CFD simulation of solid-liquid two-phase flow in the pumping station forebay with sills

Sills have been used in the forebay of pumping station in order to eliminate the circulation and vortex of diffusing flow which impact on pump performance and sediment. In the paper, three-dimensional method is used to simulate the sill flow in the forebay of pumping station based on Eulerian solid-liquid two-phase flow model. Research focuses on that sill with different section, dip and position makes important impact to flow pattern and sediment movement. The numerical results show that the attempts of adopting discontinuous bottom sills is the most effective way to eliminate the surface backflow and make the cross-section velocity distribution tend to uniform. The velocity at the bottom of the forebay and suction bay and near the pump inlet decrease significantly. Sediment accumulations in the forebay and behind the bottom sills are avoided or decreased. Compared with the literature and experimental results, it can be confirmed that CFD simulation results are credible. The further analysis can provide theoretical basis for improving the flow pattern and avoiding sediment deposition in the forebay.

NUMERICAL SIMULATION OF FLOW FIELD AND OPTIMIZATION OF STRUCTURE PARAMETERS OF VORTEX GRIT CHAMBER FOR SANDSTONE WASTEWATER TREATMENT

The problem of high concentration solid-liquid two-phase flow is difficult to overcome because the flow is complex in the vortex grit chamber. It leads to poor engineering design and operation. Eulerian - Eulerian solid-liquid two-phase flow model with the consideration of collision between particles is presented in this paper. The model is gained from the perspective of microscopic interaction between liquid and solid through the molecular kinetic theory and the computational fluid dynamics. Sliding mesh technology is used to simulate the vortex grit chamber in a hydropower sandstone wastewater treatment, Southwest China. The influences of the four factors including rotate speed, distance between the propeller and the base, number of propeller blades and angle of the propeller on the efficiency of the grit removal efficiency are studied. According to the single factor test, the optimal condition for the novel vortex grit chamber is that, the rotate speed of propeller is 105 rap/min, the distance between the propeller and the base is 592mm, the number of propeller blades is 4 and the angle of the propeller is 45?

Causes and Conditions for Reamer Blade Balling During Hole Enlargement While Drilling

In an effort to figure out the causes of reamer blade balling which occurs during hole enlargement while drilling, a solid-liquid two-phase flow model was built to simulate the cutting movement, and the simulation data were analysed. The results demonstrated that there were three dominating factors for balling: high speed vortex, high speed fluid regions which do not cover the whole reamer blade and the backflow, as well as eddy and stagnation regions appearing in the top and bottom fluid channels. In addition, further research studied three specific aspects: drilling parameters, drilling fluid parameters and the reamer-fluid structure. Then, the “dredge path, broaden region” anti-balling design principle was examined along with three evaluation criteria for flow characteristics. The optimum reamer-fluid structure and applicable field conditions were determined. The results obtained from our research will contribute to the design of reamers and the efficiency of drilling.

Numerical Simulation on Tsunami due to Sector Collapse by Solid-Liquid Two-Phase Flow Model Based on Accurate Particle Method

Numerical Simulation on Tsunami due to Sector Collapse by Solid-Liquid Two-Phase Flow Model Based on Accurate Particle Method

Numerical Simulation for Settlement Process of Blocks by Particle-Laden Turbulence Flow Model

A solver of a high accuracy and a high resolution for a solid-liquid two-phase flow model is required to predict a settlement process of dumped blocks in a construction of a block mound. Because, a settlement of blocks leads to a sediment cloud composed by suspended sediment due to turbulence near sea bottom, and a sediment cloud brings a problem of turbidity water. In the present study, numerical simulation for a settlement process of blocks in a still water has been performed by using the newly developed solid-liquid two-phase flow model including LES, which can calculate turbulent flow in detail. A flow structure around settling blocks has been shown computationally.