Two-dimensional Simulation Model Research Articles

Fracture Pattern of Overlying Strata in Multiple Coal Seam Mining in a Physical Model Vis-à-vis MATLAB Analysis and Geological Radar

To study the fracture evolution of overlying strata for ascending mining in a short-distance coal seam group, a two-dimensional physical simulation model was designed based on a specific geological condition. The fracture development zone was divided into the compaction zone and active zone by monitoring and analyzing the macro fracture evolution of the surrounding rock mass during the excavation of multiple coal seams. The secondary fracture development process of the overlying strata was demonstrated with a physical model. The quantity, length, and inclination of the fracture were calculated with MATLAB software, and the results were verified by geological radar. The total number of fractures between two coal seams increased with a “parabola” shape during the excavation of the lower coal seam, the crack angle was mainly vertical and horizontal, and the number of horizontal cracks first increased and subsequently decreased; the excavation of the upper coal seam caused the secondary fracture development process of the overlying strata, and the relief range and its extent increased. The mining-induced cracks from the lower and upper coal seams connected with each other, especially the permanent vertical fracture in the cutting room side and face side. Finally, the three-dimensional gas fissure was formed.

Numerical and analytical study for ultrasonic testing of internal delamination defects considering surface roughness

The improvement of detection accuracy and reliability of micro delamination defect is restricted by the rough surface. The flat bottom holes (FBHs) are frequently employed as reference targets to evaluate the sensitivity of ultrasonic testing for internal defects. A roughness-modified analytical model for ultrasonic testing of FBHs is established based on the principle of multi-Gaussian beam and phase-screen approximation. The signal of reference reflector is obtained from two-dimensional ultrasonic simulation model. The amplitude changes of echo signals and noises of FBHs with different diameters and depths under rough surfaces are presented. The analyses results indicate that the root-mean-square (rms) height plays a dominant role in the amplitude change of signals compared with the correlation length. The reflected wave amplitude of FBHs decreases nonlinearly with an increase of roughness whereas the amplitude of noise increases slightly. Subsequently, a method is proposed further combining the noise amplitude acquired from numerical simulation and the echo signal amplitude obtained by the analytical model, which is to predict and estimate the detection accuracy of internal defects under different surface roughness. The parallel experiments are performed on several samples with different roughness to validate the evaluation method.

CMOS 256-Pixel/480-Pixel Photovoltaic-Powered Subretinal Prosthetic Chips With Wide Image Dynamic Range and Bi/Four-Directional Sharing Electrodes and Their Ex Vivo Experimental Validations With Mice

CMOS photovoltaic-powered 256-pixel/480-pixel implantable chips with a wide image dynamic range and shared electrodes are proposed and fabricated in CIS technology for subretinal prostheses. The infra-red (IR) light is incident only on photovoltaic cells of the chip whereas the visible light is mainly incident on pixels. The proposed adaptive background cancellation circuit (ABCC) is adopted to increase the image dynamic range so that the subretinal chips can adapt for different surrounding illuminances. A two-dimensional equivalent electrode model for electric crosstalk simulation is proposed to analyze the crosstalk charges and enable the stimulation pattern design with minimum crosstalk for both chips. Moreover, the bi-directional sharing electrodes (BDSEs) are used in the 256-pixel chip to increase electrode size under the same chip area and boost the stimulation charges to 11.4 nC. The four-directional sharing electrodes (FDSEs) are used to share the electrodes in both vertical and horizontal directions and achieve 480 pixels with nearly the same electrode size under the same pixel array area. The maximum stimulation charge is 9.8 nC. The dynamic range of image light is increased to 31.65 dB (24.9 dB) in the fabricated 256-pixel (480-pixel) chip. The functions of the chip have been successfully validated by both electrical measurement and ex vivo patch clamp experiments with the retinas of mice.

Two-dimensional numerical study of gap resonance coupling with motions of floating body moored close to a bottom-mounted wall

The piston mode fluid resonance in the narrow gap between a moored floating body and a bottom-mounted vertical wall is numerically investigated based on a two-dimensional potential flow model and viscous numerical simulations. This study focuses on understanding the effect of mooring stiffness on the coupling dynamics of the gap resonance and the sway or heave motion of the floating body in regular waves. Numerical studies show that the resonant wave amplitude in the gap is reduced by the sway and heave motions. The reduction is highly dependent on the mooring stiffness. Two resonant frequencies are confirmed, and both increase with the mooring stiffness. Different modes of motions are identified in terms of the phase difference between the oscillatory motions of the gap flow and the floating body. Higher harmonic components of responses are found for the specific mooring stiffness. The performance of potential flow models in predicting resonant responses is revisited based on the understanding that the overall damping effect consists of two parts: (1) radiation damping and (2) viscous dissipation. It is confirmed that a potential model is also able to produce reasonable predictions as radiation damping plays a dominant role, for example, at the second resonant frequencies of coupling the gap resonance with the sway motion. Otherwise, as viscous dissipation dominates radiation damping, noticeable over-predictions by a potential model occur as recognized before, for example, the present results at the second peak response of gap resonance with the heave motion. The relative viscous dissipation is quantified with the reflection coefficient of viscous numerical results, while the radiation damping is quantified based on a specially designed radiation potential model with inputs of viscous numerical solutions.

Acute and subacute effects of irreversible electroporation on normal common bile ducts in a rabbit model.

This study aimed to evaluate the acute and subacute effects of irreversible electroporation (IRE) on normal common bile ducts (CBDs). Cell susceptibility to IRE was assessed in vitro with cholangiocarcinoma and normal cell lines. The electric field and temperature distributions were evaluated with a two-dimensional simulation model of bile duct. In vivo bile duct IRE was performed in 28 adult rabbits. Different cells showed different susceptibility to the effect of IRE, cancer cell line HUCC-T1 was the least sensitive to IRE. Simulations predicted the distributions of electric field and temperature during the IRE process, and the maximum temperature of tissue was below 43℃. Complications were observed in 8/28 animals (biliary dilatation, n=4; biliary stricture, n=4) by postoperative days 7, 14, and 28. Histopathological analyses revealed complete cell death with bile duct wall integrity. Bile duct epithelial recovery was completed between post-IRE days 14-28. The normal CBD retains the lumen wall integrity following IRE with immediate periductal placement of the electrode. However, the risk of biliary dilatation and stricture is a reminder that the parameters of IRE need to be determined more precisely to ensure the treatment efficacy and reduce the risk of collateral damage.

The Alderney Race: general hydrodynamic and particular features.

This study presents an overview of the main hydrodynamic features of the Alderney Race strait based on in situ measurements and two-dimensional hydrodynamic model simulations. The strait encompasses a large amplitude of tidal properties (tidal range and tidal wave propagation) and particularly strong currents exceeding 5 m s−1 with associated counter currents and gyres. Variations in depth, sea bottom roughness, coastal topography and current orientation around the La Hague Cape provide access to a large variety of original hydrodynamic regimes. Some are revealed as locations with a 0.4 m drop in the mean sea level associated with strong average currents. A resonance effect associated with the offshore currents can also be observed close to the coasts. The ‘St Martin whistle’ occurs in a bay whose gyre centre oscillates with a reversal of the measured current every 5–7 min. The Alderney Race represents a particular area of interest for coastal hydrodynamic studies. The available in situ measurement datasets are rich with recordings of: sea levels; acoustic Doppler current profiler current profiles; surface radar currents; waves; dye experiments; surface and in-depth dissolved tracer surveys. Combined with hydrodynamic models, the complexity of this area can be further understood and knowledge of the hydrodynamic process and forcing parameters can be refined, which can be applied to other coastal areas.This article is part of the theme issue ‘New insights on tidal dynamics and tidal energy harvesting in the Alderney Race’.

Studies on thermal and interface optimization for CdZnTe crystals by unseeded Traveling Heater Method

A stable thermal field and a controlled convex growth interface are essential for the stable growth of large-size CdZnTe crystals by the Traveling Heater Method (THM). However, the crucible wall temperature always increases due to the deposition of CdZnTe crystals with low thermal conductivity at the bottom of the crucible. A comprehensive two-dimensional simulation model for THM growth of CdZnTe is developed and implemented to study the heat and mass transfer. The effect of increasing wall temperature on interface shape and concentration distribution is discussed. Experimental results show that a dummy crystal with a thermal conductivity similar to that of the CdZnTe crystal helps to stabilize the wall temperature. In a stable thermal field, low constant rotation is assumed to be sufficient to weaken natural convection flow and to make the interface convex in THM. Simulation results show that low constant rotation rates of 2.5 RPM for 2-in. crystal and of 1.25 RPM for 3-in. crystal are effective in interface optimization. Several ingots with a diameter of 2 in. and 3 in. were grown by unseeded THM. Convex interfaces were observed both in 2-in. and 3-in. crystals by applying simulated rotation rates after fast cooling.

Incorporating infiltration in the two-dimensional ANUGA model for surface irrigation simulation

Improving irrigation efficiency on farms is crucial in securing a sustainable future for irrigators as well as the environment, especially in water scarce regions such as Australia. More efficient irrigation designs are increasingly being investigated using irrigation simulation models but there is a dearth of readily available two-dimensional (2D) models for investigating surface water flow within irrigation bays. This paper adapted the 2D ANUGA open source model to simulate border and basin irrigation by incorporating an infiltration algorithm based on the modified Kostiakov equation. The algorithm was successfully incorporated in ANUGA and the adapted model, ANUGA_MK, was tested using eight border and two basin irrigation events. ANUGA_MK performance was benchmarked against the one-dimensional (1D) SISCO irrigation model for border irrigation events, against the 2D B2D basin irrigation model for basin irrigation events and against observed data. ANUGA_MK adequately simulated surface water advance and depth. SISCO’s total infiltration was comparable to that of ANUGA_MK, but its spatio-temporal dynamics differed due to differences in representation of microtopography. For example, the 1D SISCO model did not account for surface depression water storage remaining long after cessation of runoff. Performance of ANUGA_MK was similar to that of B2D in simulating basin irrigation. ANUGA can represent surface water flow on complex surfaces with diverse boundary conditions, and with an appropriate infiltration algorithm, has been adapted as a surface irrigation model that can be used to investigate bay surfaces engineered to improve surface drainage.

Development of a reconstruction quality metric for optical three-dimensional measurement systems in use for hot-state measurement object

Optical three-dimensional (3-D) geometry measurements are state of the art when it comes to contactless quality control and maintenance of the shape of technical components that exclude tactile measurements due to filigree or internal structures. Optical inspection methods are also characterized by a fast and high-resolution 3-D inspection of complex geometries. And due to their noncontact principle, they can carry out measurements in places that would otherwise not be accessible due to harsh environmental conditions or specimens such as hot forged parts. However, there are currently no methods to estimate the reconstruction quality for the optical 3-D geometry measurements of hot objects. The mainly used geometric measurement standards cannot be used for the characterization of hot measurements since the calibrated geometrical values are not transferable to high temperatures. For the development of such a metric, we present the fundamentals of the concepts and algorithms for an estimation of the reconstruction quality are presented and evaluated using a two-dimensional simulation model. The generated findings were applied to the 3-D geometry measurement of a hot object in a laboratory environment. The results are compared with general state-of-the-art reconstruction quality metrics.

Current frequency effect on electromagnetic tube expansion

The frequency of capacitor discharge current is an important parameter in the electromagnetic forming process. In the present work, simulation and experimental study of electromagnetic expansion is carried out on aluminium tubes (Al 5052). The aim is to obtain the optimum frequency of discharge current that gives maximum tube expansion at constant discharge energy. A two-dimensional axisymmetric numerical simulation model is developed that couples electromagnetic and structural phenomenon sequentially. After validating experimental tube expansion results with numerical results, the simulation model is used to analyse the effect of variation in current frequency on the tube expansion. It is observed that maximum tube expansion and higher process efficiency occurred at 5 kHz, which is considered as the optimum frequency for the used experimental set-up. In contrast to sheet forming case observed in the literature, results of tube expansion show that maximum forming is obtained at a frequency where the ratio of skin depth to tube thickness is less than 1. It is also noticed that the optimum frequency depends on the inductance and resistance of the system.

Optimal mass of the arm segments in throwing: A two-dimensional computer simulation study

Producing a high release speed is important in throwing sports such as baseball and the javelin throw. Athletes in throwing sports might be able to achieve a greater throwing speed by improving the effectiveness of the kinetic chain. In this study a two-dimensional computer simulation model of overarm throwing was used to examine the effect of changes in forearm mass and upper arm mass on the release speed of a lightweight (58 g) projectile. The simulations showed that increasing the mass of the forearm decreases release speed, whereas increasing the mass of the upper arm initially increases release speed. For a given forearm mass there is an optimal upper arm mass that produces the greatest release speed. However, the optimal upper arm mass (5–6 kg) is substantially greater than that of an average adult (2.1 kg). These results suggest that athletes might be able to throw faster if they had a stronger tapering of segment mass along the length of their arm. A stronger taper could be readily achieved by attaching weights to the upper arm or by using hypertrophy training to increase the mass of the upper arm. High-speed overarm throwing is a complex three-dimensional movement and this study was a preliminary investigation into the effect of arm segment mass on throwing performance. Further simulation studies using three-dimensional throwing models are needed to generate more accurate insights, and the predictions of the simulation studies should be compared to data from experimental intervention studies of throwing sports.

Effects of fins arrangement and parameters on the consecutive melting and solidification of PCM in a latent heat storage unit

Abstract This study is to investigate the characteristics of consecutive melting and solidification of a phase change material (PCM) in a horizontal double tube LHS unit. Fins is used to improve the heat transfer rate on the PCM due to its low thermal conductivity. A two-dimensional symmetric simulation model with considering natural convection is established. Enthalpy-porosity technique is used for modeling the phase change process. The effects of fins arrangements, number (N) and length (L) on the heat storage performance were studied. In addition, the effect of outer shell material of the finned LHS unit was studied. Moreover, the interactions among N, L, outer shell material and fins arrangement are considered. Results show that the fins of straight design shows a higher heat transfer enhancement than other arrangements, especially for the cases with small fins number (N

The effects of beam proportion on electromagnetic proton/proton instability and associated ion heating: 2D hybrid simulation

In this paper, the effects of beam proportion on the electromagnetic proton/proton instability and involved proton dynamics have been investigated with a two-dimensional hybrid simulation model. The beam proportion is defined as the number density ratio between the beam and all protons. The simulation results show that the saturation amplitude of excited oblique Alfvén waves becomes larger with the increasing proportion of beam protons. Besides, the polarization of oblique Alfvén waves generated by beam protons with a higher proportion tends to be more linear. Moreover, with the increase in the beam proportion, the peak frequencies of excited waves will move toward higher values even exceed the proton gyrofrequency. This will result in more efficient heating of core protons in the perpendicular direction through the cyclotron resonance with Alfvén waves. Our study may provide some new insights into the heating mechanism of the solar wind.

A simple and efficient two-dimensional hydrodynamic model for unsteady flow simulation in undulating bathymetry

A simple and efficient two-dimensional hydrodynamic model for unsteady flow simulation in undulating bathymetry

Prediction of Ventilation Effects on Reducing Moisture Damage in Tishun Tang in the Palace Museum in Beijing, China

The Palace Museum in Beijing is World Cultural Heritage and representative of Chinese traditional brick buildings, but has been suffering deterioration for centuries. Environment monitoring showed that the special construction of foundation resulted in the humid micro-environment and moisture damage near wall bottom and floor in buildings. In order to make clear the effects of ventilation on reducing moisture damage, we took Tishun Tang as example and built a two-dimensional hygrothermal simulation model. There are two ventilation plans. One is direct ventilation, letting the outdoor air go into indoor space directly through the flue under floor. The other is to add air temperature and humidity control during that produce, called controlled ventilation. In those two plans, ventilation rate is raised to 1 time per hour from 0.4 times (current state). The results show that compared with direct ventilation, controlled ventilation is more efficient for reducing moisture damage. In controlled ventilation plan, heating outdoor air before the air exchange in winter benefits to raising indoor surface temperature by one degree and reducing area of freezing-thawing damage. Dehumidifying the outdoor air during ventilation in summer is the most important point of decreasing the high mould risk from 22 ~ 25 days to 7 ~ 10 days.

Modulation of millimetre-wave and THz properties of IMPATT sources via external magnetic field

The modulation of millimetre-wave (mm-wave) and terahertz (THz) properties of impact avalanche transit time (IMPATT) sources under external steady magnetic field has been studied in this paper. The arrangement of magnetic field tuning of IMPATT oscillators by using external transverse steady magnetic field is referred to as magnetic field tunable avalanche transit time (MAGTATT) oscillators. The sensitivities of various static, large-signal and noise characteristics of silicon-based MAGTATT sources operating at mm-wave atmospheric window frequencies (94, 140 and 220 GHz) and two different THz frequencies (0.3 and 0.5 THz) have been studied. Comprehensive two-dimensional simulation models developed by the authors for evaluating static, large-signal and noise characteristics of MATATT diodes have been used for this purpose. The simulation results show that the above-mentioned magnetic field sensitivities of the device properties are significantly reduced with the increase of the operating frequency.

Numerical simulation of electrokinetic desalination using microporous permselective membranes

A new scheme for parallelization of microchannels for ion concentration polarization-based seawater desalination is proposed. In the proposed system, microchannels/micropores are paralleled only in ion-selective membrane region and all other parts are simply merged. A two-dimensional simulation model is developed to study performances of such a system, by calculating the salt removal ratio (SRR) and the average velocity of fluid, under varied working conditions. Our results show that SRR >98% for seawater salinity (realizing drinkable water) is achievable. It is found that a stronger cross membrane voltage strengthens electrokinetic flow of the second kind (EOF2) and increases both SRR and flow velocity. Increasing pressure promotes fluid flow but decrease SRR and EOF2 significantly when the ion depletion zone is destroyed. Volumetric energy consumption and energy per ion removal (EPIR) were also characterized under varied electric field and pressure conditions. Energy consumption as low as 12.82 kWh/m3 was realized to convert seawater (salinity ~500 mM) to the desalinated water (salinity ~10 mM) at a flow speed of 0.56 mm/s. The overall cost of water for such a process was estimated as 2.08 $/m3, which is competitive for small-scale desalination applications.

Effects of the die parameters on the self-piercing riveting process

To facilitate the die selection for new self-piercing riveting (SPR) joint configurations, it is necessary to find out how the critical die geometric parameters influence the SPR process. In this study, a two-dimensional (2D) axisymmetric simulation model was developed to numerically study the riveting process. The influences of the die type, the die diameter, the die depth, and the die pip height on the deformation behaviour of the rivet and sheets were systematically studied. Moreover, the flared rivet shank radius and the thickness at the centre of the bottom sheet during the SPR process were first monitored using the developed simulation model. The simulation results revealed that these die parameters have significant influences on the deformation behaviour of the rivet and sheets. The flared rivet shank radius showed an increasing trend with the increment of the die diameter and the die pip height, while it decreased with the increment of the die depth. Furthermore, it was also found that the flaring speed of the rivet shank depended heavily on the filling condition of the die cavity underneath the rivet cavity. A rapid flare of the rivet shank was observed when this space was fully filled.

Finite element analysis of ultrasonic assisted milling of SiCp/Al composites

SiCp/Al composites have a poor machinability due to the inclusion of the SiC hard particles. Ultrasonic vibration-assisted processing technology has great advantages in processing hard and brittle materials; however, the process of rupture of particles cannot be effectively observed during the test processing, and a large number of tests increase the cost of the test. Using ABAQUS finite element software, a two-dimensional simulation model of single particle, multi-particle, and homogeneous materials was established to investigate the particle rupture process and the temperature variation during the processing of high volume SiCp/Al composites under different processing parameters. The results show that the application of ultrasound improved the particle rupture effect. Furthermore, an appropriate ultrasonic amplitude inhibited the particle breakage and slowed the crack growth. A smoother particle breaking phenomena was observed with the application of a higher frequency. The temperature of ultrasonic assisted milling was found to be lower than that of traditional milling. The conclusions of the milling test were basically consistent with the simulation results, which prove the correctness and feasibility of the simulation results.

Study of Voltage Distribution and Radial Electric Field under Different Pollution Conditions of 500kV MOA

The surface of the porcelain sleeve will be polluted by local environmental pollution and weather factors such as frost, rain and snow, because of the 500kV MOA is generally arranged outdoors. The surface flashover problem of the porcelain sleeve surface caused by contamination is similar to that of the insulator surface. It is a resistor column with three sections connected in series inside the arrester. The influence of surface contamination on the voltage distribution of the internal resistor and the radial electric field between the resistor and the porcelain sleeve remains to be studied. In this paper, ANSYS is used to establish a two-dimensional axisymmetric simulation model for the surface contamination of 500kV zinc oxide arrester. The electric field distribution of the surface of the arrester is cleaned, evenly polluted and the local drying zone appears. The results show that the uniform contamination is inside the arrester. The electric field has little influence, and the local drying zone will form a locally excessively high radial electric field between the resistor and the porcelain sleeve. Under the reference voltage, the radial electric field exceeds the corona starting field and causes corona discharge, and the acceleration resistor Deterioration of the sheet and the dielectric; the voltage of the resistor piece near the local drying zone is increased to a certain extent, which also accelerates the aging of the resistor chip and jeopardizes the safe and stable operation of the arrester