Three-dimensional Numerical Simulation Study Research Articles

Three-dimensional numerical simulation study of pre-cracked shale based on CT technology

Due to the heterogeneity of rock media, it is difficult to truly reflect its internal three-dimensional microstructure in physical tests or numerical simulation. In this study, CT scanning technology and numerical image processing technology are used, and the finite element software RFPA-3D is used to establish a three-dimensional non-uniform numerical model that can reflect the meso structure of rock mass. In order to study the fracture mechanism of shale with prefabricated fractures, seven groups of three-dimensional numerical models with prefabricated fractures from different angles were constructed, and Brazilian fracturing numerical simulation tests were carried out. The results show that method of reconstructing 3D numerical models by CT scanning is feasible and provides a viable method for in-depth study of the micromechanics of shale. Prefabricated fractures and quartz minerals have significant effects on the tensile strength of shale, and both will weaken the destructive strength of shale specimens. The damage modes of Brazilian disc specimens containing prefabricated fissures can be divided into four categories. The damage process is divided into budding, plateauing and surge periods by acoustic emission. The crack initiation angle of the prefabricated fissure tip increases with increasing fissure angle, and the MTS criterion can be used as a basis for judging prefabricated fissure initiation. The results of the study are important guidance for the fracture initiation mechanism and fracture expansion law of the fractured layer containing natural fractures in the hydraulic fracturing process.

Study on the Horizontal Movement State of Suction Anchor Piles for Offshore Wind Power during Horizontal Pulling

The subsea anchor piles of offshore wind power floating platform structures are mainly subjected to uplift and horizontal loads, and this paper focuses on the case of horizontal loads. A three-dimensional numerical simulation study of the horizontal pullout characteristics of wind power suction anchor piles in clay layers was carried out to reveal the horizontal movement state of the anchor piles during horizontal pile pullout, the range of pile depth at the pullout point where the horizontal movement is achieved (referred to as the horizontal movement range), the relationship between the pullout load and the ultimate load during the horizontal movement, and the optimal location of the pullout point for the horizontal movement. The results show that at certain pull-out points, the anchor pile produces an overall horizontal movement state under suitable horizontal pull-out loads. The depth of the pile pull-out point for horizontal movement is in the middle and lower part of the pile, i.e. 14.2 m to 14.5 m. The horizontal pull-out load of 24,000 kN at a depth of 14.5 m within the pile horizontal movement range of 14.2m to 14.5 m is the maximum ultimate horizontal pull-out load; the optimum pull-out point depth is 14.5 m at 0.275 L (L is the pile length). For each pull-out point of the anchor pile in horizontal movement, the horizontal pull-out load in horizontal movement and the horizontal ultimate pull-out load existed and it was found that the two values were not exactly the same, the values were compared and it was found that at the optimum pull-out point the value of the ultimate horizontal pull-out load/horizontal pull-out load in horizontal movement tended to 1.

Calculation and Analysis of DC Magnetic Bias Current of Urban Main Transformer under the Action of Stray Current

The stray current generated by subway running into the ground makes the main transformer in the urban area in a direct current (DC) bias state. First, the mathematical model of the metro stray current field is established and the Galerkin finite element method is applied to calculate the model. Then, the dynamic model of the stray current-induced geoelectric field under different working conditions is established by using ANSYS software, and the three-dimensional numerical simulation study of the stray current-induced geoelectric field of the subway is carried out. Finally, taking the Urumqi subway in Xinjiang as an example, the stray current-induced geoelectric field is calculated and simulated, and the correctness of the model is verified by comparing with the measured data of DC magnetic bias in the urban substation. The research can provide useful reference for the calculation and treatment of DC bias of the main transformer in the urban area under the action of stray current.

Numerical Simulation of Surface Deformation in Goaf

Coal mine goaf is a hidden, complex, surface deformation of a large range and easy to cause geological disasters of the bad construction site, the surface engineering construction of great harm. The uneven subsidence, horizontal movement, deformation, collapse and other disasters of the goaf surface have serious potential safety hazards for the construction and operation of the project. At the same time, secondary disasters such as ground collapse and collapse caused by surface movement and deformation also occur from time to time, which seriously threaten the safety of construction projects. In this paper, Flac3D is used to conduct a three-dimensional numerical simulation study on the goaf of jinjie coal mine, and the surface deformation law of the goaf is obtained by analyzing the horizontal movement, vertical settlement, horizontal deformation and inclined deformation of the goaf, which provides a theoretical basis for the surface deformation management of the local goaf.

The capability of Ansys CFX to predict the mixing phenomena in ROCOM test facility

This work consists of a Computational Fluid Dynamics (CFD) modeling of a reference experiment on boron dilution in the Rossendorf coolant mixing Model (ROCOM) as part of a coordinated research project of the International Atomic Energy Agency, namely, “Application of numerical codes of fluid dynamics to the design of nuclear power plants”. This coordinated project aims to address the application of CFD codes to the process of optimizing the design of nuclear power plants related to pressurized water reactors and to evaluate the performance and predictive capabilities of these codes and to contribute to their validation. In this context, a three-dimensional numerical simulation study was carried out using CFD code ANSYS CFX v14.5, to study the boron mixing phenomenon at the core inlet and the downcomer of the ROCOM test facility. The phenomenon of experimental mixing occurs by the injection of a tracer (sodium chloride) into one of the loops of the ROCOM installation mainly containing demineralized water in its primary circuit. The concentration field of the tracer is measured and simulated at the entrance of the heart and in the lowering. The SST-kω turbulence model used in this study could reasonably predict the distribution of the injected tracer in measurement locations within the test facility. The results of this numerical simulation were compared to the Benchmark data provided by the ROCOM experimental facility of the Helmholtz-Zentrum Dresden-Rossendorf Institute.

Thermo-Hydraulic Performance Enhancement of Finned Elliptical Tube Heat Exchangers by Utilizing Innovative Dimple Turbulators

As a new type of fin structure in finned tube heat exchangers, dimple turbulators exhibit excellent potential for thermo-hydraulic performance enhancement. A three-dimensional numerical simulation study was conducted to investigate the influences of five kinds of innovative concave dimple turbulators (CDTs), namely – elliptical dimple, conical frustum dimple, trapezoidal prism dimple, leeward triangular dimple and upward triangular dimple (UwTD) on the thermo-hydraulic performance enhancement in a plate fin-and-elliptical tube (PFET) heat exchanger, where CDTs are textured on the fin surface transversely between the elliptical tubes. The computational results are analyzed by considering the performance evaluation criterion for the PFET heat exchangers with different types of CDT shapes. The present investigation demonstrates that the heat transfer enhancement is intimately pertained to ejection with longitudinal counter-rotating flow, strengthened secondary flow and vortex structures at the downstream rim of CDT. A parametric study on the CDTs indicated that the UwTD vortex turbulators give better thermo-hydraulic performance under the present conditions. The numerical simulation results illustrated different secondary flow structures and heat transfer characteristics of the CDTs with various shapes, which disclosed the influential mechanisms of differently shaped dimple turbulators on the heat transfer augmentation in PFET heat exchangers.

Three-dimensional numerical analysis of Marangoni convection occurring during the growth process of SiC by the RF-TSSG method

A three-dimensional numerical simulation study has been carried for the Top-Seeded Solution Growth (TSSG) process of single crystal SiC. During growth, Marangoni and forced convections (flows) develop in the growth solution due to free surface tension gradient and seed rotation, respectively. Relative contributions of such flows were numerically examined. Since supersaturation in the growth solution near the crystal surface is a key factor affecting the stability of crystal morphology, our study has focused on the influence of these flows on the distributions of spatial and temporal flow velocity and solution supersaturation. Simulation results show that the contribution of Marangoni convection gives rise to the development of spoke-like flow patterns and a downward flow below the seed crystal that leads to a non-uniform supersaturation distribution at the center and at the edge near the seed crystal surface. Additionally, a characteristic frequency associated with the supersaturation oscillation appears to be due to the Marangoni instability. Results also show that, although the forced convection induced by seed rotation may weaken such supersaturation non-uniformity in the center and suppress the development of such spoke-like patterns, its effect near the edge is not significant.

Numerical investigation for the effect of the liquid film volume on thermocapillary flow direction in a thin circular liquid film

NASA Astronaut Dr. Pettit carried out a thermocapillary flow experiment onboard the International Space Station in 2003. In this experiment a thin water film containing milk powder was formed in a stainless-steel wire ring. Heating a section of the ring by a soldering iron induced in the water film a thermocapillary flow towards the heated section of the ring (outward flow: cold to hot). This flow was in the opposite direction of the usually observed thermocapillary flows (inward flow: hot to cold). To shed light on this interesting phenomenon observed in the space experiment, we have conducted a three-dimensional numerical simulation study. Simulation results showed that the film geometry of the water film is a key factor determining flow direction and flow strength. When the liquid film free surfaces are convex, i.e., the water film volume is larger than that when the free surfaces are flat, an outward flow develops in the film as observed in the space experiment. However, when the free surfaces are concave, the simulation predicts an inward flow.

3D numerical simulations of the 110 GHz, 220 GHz coaxial cavity double-beam gyrotron

Since to break the limitation of traditional single anode magnetron injection electron gun can only produce a lower power, this paper, based on an independent research and development of particle simulation software CHIPIC, will take the 110 GHz, 220 GHz coaxial cavity double-beam gyrotron for full three-dimensional numerical simulation study. By theoretical analysis for the initial parameters of the coaxial double-beam electron gun and to optimize the design by CHIPIC, we obtain the high-performance electron beam with the horizontal and vertical velocity ratio of 1.0 and the maximum velocity spread of 5.4%, and use the optimized electron gun to replace the traditional gyrotron emission for numerical simulation of the 110 GHz, 220 GHz gyrotron system, as well as the four-process parallel MPI in computing. Finally we obtain that the double bands are 110 and 220 GHz respectively, a TE02 mode, and the average output power about 70 kW. The efficiency can reach 8.75% for the high performance double-beam gyrotron oscillating tube.

Numerical simulation of incompressible laminar flow in a three-dimensional channel with a cubical open cavity with a bottom wall heated

A three-dimensional numerical simulation study for both laminar steady and unsteady regimes has been carried out for the mixed convective flow over a three-dimensional cubical open cavity. The cavity is heated from below at constant temperature while the other walls are adiabatic. The numerical simulation has been done using a three-dimensional incompressible finite volume flow solver. The effects over the velocity and temperature distribution of the buoyancy forces acting perpendicular to the mainstream flow are studied for Reynolds numbers (Re) between 100 and 1500; Prandtl number (Pr) is set to 0.7 and Richardson number (Ri) between 10−3 to 101. The phenomenological description of the mixed convection inside and outside the cavity and the combined effects of the natural and forced convection have been obtained. For both high Re and Ri the flow becomes unsteady. The mixed convection effects dominate the flow transport mechanism and push the recirculation zone and the flow further upstream.

The three-dimensional numerical simulation study of H transmission and negative hydrogen ions production

The negative hydrogen ion source neutral particle transmission characteristics and the physical processes of the negative hydrogen ion extracted from plasma grid surface are analyzed. The influence of the extraction hole transfer rate which leads to hydrogen atom transmission is studied. A physical phenomenon of collision and reflection between H and different attribution conductor walls is explored. Then based on CHIPIC software platform, a full three-dimensional PIC-MCC simulation algorithm, in which the H transmission and the physical process of negative hydrogen ion production can be simulated, is successfully developed. It is verified by the simulation of JAEA 10A model. While the simulation reaches a steady state, the average energy of H is about 0.57 eV and H presents +Y drift. The non-uniform H beam bombarding the extraction wall leads to the spatial nonuniformity of negative hydrogen ions. These simulation results are consistent with those given in the literature, thereby verifying the reliability of the algorithm.

Numerical simulation study of the influence on stability of slope by underground mining under opencast coal mine slope

In view of the study on mining transferred from open-pit to underground, the research on the problem of the stability of slope is less. This article combined the actual situation of the Gaohai Coal Mine in Fuxin City and set up a three-dimensional model of the part of Huizhou open-pit slope by the finite difference software. Through the three-dimensional numerical simulation study of the influence on the stability of slope by underground mining, the basic characteristics of the open-pit slope deformation and the situation of basic stability were discussed. The simulation results of the mining slope of the displacement and deformation analysis of the state for mining provide a reference to the slope stability research.

Comparison between Berkovich, Vickers and conical indentation tests: A three-dimensional numerical simulation study

Three-dimensional numerical simulations of Berkovich, Vickers and conical indenter hardness tests were carried out to investigate the influence of indenter geometry on indentation test results of bulk and composite film/substrate materials. The strain distributions obtained from the three indenters tested were studied, in order to clarify the differences in the load–indentation depth curves and hardness values of both types of materials. For bulk materials, the differentiation between the results obtained with the three indenters is material sensitive. The indenter geometry shape factor, β, for evaluating Young’s modulus for each indenter, was also estimated. Depending on the indenter geometry, distinct mechanical behaviours are observed for composite materials, which are related to the size of the indentation region in the film. The indentation depth at which the substrate starts to deform plastically is sensitive to indenter geometry.

Ge<SUB align=right>0.98Si<SUB align=right>0.02 crystal grown by the travelling heating method using axial magnetic field and rotating crucible

A three-dimensional numerical simulation study was carried out for crystal growth of GeSi by the travelling heater method (THM). The effect of an axial magnetic field combined with crucible rotation was investigated. The effect of magnetic field intensity was studied first then the crucible rotation was added to the model. The full Navier-Stokes equations together with the energy, mass transport and continuity equations were numerically solved using the finite element technique. By increasing the magnetic field intensity, the intensity of the flow at the centre of the crucible decreased at a faster rate compared to the flow near the walls. This phenomenon created a stable and uniform silicon distribution in the horizontal plane and became relatively homocentric. The addition of a crucible rotation showed an improvement in the suppression of the flow intensity.

A numerical simulation study for the zone refining processes of cadmium and tellurium

This article presents the results of a three-dimensional numerical simulation study carried out for a three-zone refiner system. Firstly, an overall thermal analysis was performed to study the effects of changes in the size of the ZR system. A complete mass, heat, and momentum transport model was then developed for this system, and the fluid flow and impurity concentration distributions in a single molten zone were studied. A parametric study was also carried out to obtain the most favourable freezing interfaces and molten zone sizes. The flow field in the molten zone was studied to determine its effect on impurity transport.

Liquid phase electro epitaxy growth kinetics of GaAs—A three-dimensional numerical simulation study

A three-dimensional numerical simulation study for the liquid phase electro epitaxial growth kinetic of GaAs is presented. The kinetic model is constructed considering (i) the diffusive and convective mass transport, (ii) the heat transfer due to thermoelectric effects such as Peltier effect, Joule effect and Thomson effect, (iii) the electric current distribution with electromigration and (iv) the fluid flow coupled with concentration and temperature fields. The simulations are performed for two configurations namely (i) epitaxial growth from the arsenic saturated gallium rich growth solution, i.e., limited solution model and (ii) epitaxial growth from the arsenic saturated gallium rich growth solution with polycrystalline GaAs feed. The governing equations of liquid phase electro epitaxy are solved numerically with appropriate initial and boundary conditions using the central difference method. Simulations are performed to determine the following, a concentration profiles of solute atoms (As) in the Ga-rich growth solution, shape of the substrate evolution, the growth rate of the GaAs epitaxial film, the contributions of Peltier effect and electromigration of solute atoms to the growth with various experimental growth conditions. The growth rate is found to increase with increasing growth temperature and applied current density. The results are discussed in detail.

A Three-dimensional Numerical Simulation Study for the Cathode Side of a Fuel Cell

A Three-dimensional Numerical Simulation Study for the Cathode Side of a Fuel Cell

A three-dimensional numerical simulation study of the Marangoni convection occurring in the crystal growth of Si xGe 1− x by the float-zone technique in zero gravity

A numerical simulation study was carried out to examine the effect of solutal Marangoni convection during the Si x Ge 1− x crystal growth by the floating-zone (FZ) technique under zero gravity. In this study, a three-dimensional full-zone configuration for the FZ was considered. Computational results show that the contribution of the solutal Marangoni convection to the flow structure was significant although the strength of the solutal Marangoni convection is much weaker than that of the thermal Marangoni convection. Application of a crystal and feed rotation with an optimum rate induces a good mixing in the melt and leads to crystals with a uniform concentration distribution along the growth interface.