3D validation, 2D feasibility, corrected and developed correlations for pure solid-gallium phase change modeling by enthalpy-porosity methodology

Influence of two- and three-dimensional simulations on bubble behavior in gas–solid fluidized beds with and without immersed horizontal tubes

In spite of the importance of a detailed description of the filamentary current constriction of the IGBT during the turn-off operation that could lead to the device’s failure, there are to date no quantitative 3D simulation results of the filament growth and dynamic that can be compared with experimental results. In this paper we present 3D numerical simulations on the failure mode in the Unclamped Inductance Switching (UIS) test operation, extended to the full device area, which will be usefully compared with detailed experimental results on a large number of trench IGBT test samples. For the first time extended 3D dynamic electrothermal simulations of the whole die are made, to take into account both the electric and thermal effects of the filamentary conduction in avalanche mode. The onset of a filament growth condition for a current level just above the turnover voltage evaluated by the 3D simulations, and the area of the filament, obtained for the first time, are well in agreement with the quantitative data extracted by the experimental evaluations. Moreover, the thermal heating due to the filament formation is found to be quite independent from the current level, because it depends on the current density in the filament, rather than on the injected current. The delay time between the filament formation and the final failure time seen in the experimental results is verified to be due to the movement of the filament all around the chip surface in search of a cooler spot. The movement of the filament along the whole die area is verified for the first time by full area 3D electrothermal dynamic simulations, with times in agreement with the experimental delay between filament formation and final failure seen in all the failure reports.

There have been remarkable advances in semiconductor industry but the miniaturization of magnetic devices is progressed very slowly. So many studies are carried out overcoming the gap. To develop small size devices, proper design and property simulation of the devices are requested to spare the efforts before fabrication processes. However, there is a few of simulation studies have been reported. In this work, we fabricated thin film toroidal inductors using permalloy as a core material and measured the properties to estimate 2D and 3D simulation in the magnetic devices. The 3D simulation shows more agreeable results than the 2D simulation. On the other hand, when we changed core materials, the inductor using Fe-Hf-C-N nanocrystalline alloys as core material shows the better properties than using permalloy and Fe-Zr-C-N alloys.

We used ultrasonic shear waves for nondestructive defect detection in a billet using transmitted waves. We utilized the deviation the time-of-flight (TOF) obtained by cross-correlation of transmitted waves of a defect-free reference plane and that of a measurement plane containing a defect. We compared the performance of longitudinal waves and shear waves at different wavelengths in detecting the diameter of a circular defect in two-dimensional (2D) simulation and the TOF for a cylindrical defect while changing the vibration direction of shear waves in three-dimensional (3D) simulation. Shear waves detected defects better than longitudinal waves in the 2D simulation, especially at wavelengths of 1.4–2.4 mm. In the 3D simulation, the maximum TOF was larger when the vibration direction was perpendicular to the defect’s major axis than when it was parallel in the measurement using shear waves. This suggests a defect’s shape can be estimated by measurement using shear waves.

In this study, the 2D and 3D cloud-resolving model simulations of the Tropical Rainfall Measuring Mission (TRMM) Kwajalein Experiment (KWAJEX) are compared to study the impact of dimensionality on barotropic processes during tropical convective development. Barotropic conversion of perturbation kinetic energy is associated with vertical transport of horizontal momentum under vertical shear of background horizontal winds. The similarities in both 2D and 3D model simulations show that 1) vertical wind shear is a necessary condition for barotropic conversion, but it does not control the barotropic conversion; 2) the evolution of barotropic conversion is related to that of the vertical transport of horizontal momentum; and 3) the tendency of vertical transport of horizontal momentum is mainly determined by the covariance between horizontal wind and the cloud hydrometeor component of buoyancy. The differences between the 2D and 3D model simulations reveal that 1) the barotropic conversion has shorter time scales and a larger contribution in the 2D model simulation than in the 3D model simulation and 2) kinetic energy is generally converted from the mean circulations to perturbation circulations in the 3D model simulation. In contrast, more kinetic energy is transferred from perturbation circulations to the mean circulations in the 2D model simulation. The same large-scale vertical velocity may account for the similarities, whereas the inclusion of meridional winds in the 3D model simulation may be responsible for the differences in barotropic conversion between the 2D and 3D model simulations.

Two- and three-dimensional Direct Numerical Simulation of particle-laden gravity currents

In this study, E-Scaffolding Enhance Learning (ESEL) using Web-based simulation has been designed and implemented. The scaffolding approach in this research is a conceptual scaffolding of the moment of inertia. Web-based simulation consists of 2D and 3D simulation. The 3D simulation was developed using unity software and 2D simulation was developed using scratch and articulate storyline software. All simulation was published as an Html file, and finally inserted into the website. The validation of the product was carried out by experts such as a physics lecturer and a physics teacher. The implementation phase was carried out through collaborative distance learning between one Senior High School in Bandung and one school in West Nusa Tenggara. The validation results show that ESEL using Web-based simulation on moment of inertia is deserved with an average score of 92% in the very good category. Nevertheless, there are several improvements still need to be made in terms of the appearance of the Web-based 3D simulation especially when it is accessed by phone cell. The appearance of the Web-based 3D simulation is still not responsive for smartphones. But based on the questionnaire result of students, ESEL using Web-based simulation on moment of inertia has a value 71% which means that ESEL has a good category of validation and is interesting for the students. ESEL using Web-based simulation also improves students’ activities in the distance learning of physics classroom.

A comparative study between two- and three-dimensional (2D and 3D) modeling is carried out on arc discharge phenomena inside a thermal plasma torch with hollow electrodes, in order to evaluate the effects of arc root configuration characterized by either 2D annular or 3D highly localized attachment on the electrode surface. For this purpose, a more precise 3D transient model has been developed by taking account of 3D arc current distribution and arc root rotation. The 3D simulation results apparently reveal that the 3D arc root attachment brings about the inherent 3D and turbulence nature of plasma fields inside the torch. It is also found that the constricted arc column near the vortex chamber plays an important role in heating and acceleration of injected arc gases by concentrating arc currents on the axis of the hollow electrodes. The inherent 3D nature of arc discharge is well preserved inside the cathode region, while these 3D features slowly diminish behind the vortex chamber where the turbulent flow begins to be developed in the anode region. Based on the present simulation results, it is noted that the mixing effects of the strong turbulent flow on the heat and mass transfer are mainly responsible for the gradual relaxation of the 3D structures of plasma fields into the 2D axisymmetric ones that eventually appear in the anode region near the torch exit. From a detailed comparison of the 3D results with the 2D ones, the arc root configuration seems to have a significant effect on the heat transfer to the electrode surfaces interacting with the turbulent plasma flow. That is, in the 2D simulation based on an axisymmetric stationary model, the turbulence phenomena are fairly underestimated and the amount of heat transferred to the cold anode wall is calculated to be smaller than that obtained in the 3D simulation. For the validation of the numerical simulations, calculated plasma temperatures and axial velocities are compared with experimentally measured ones, and the 3D simulation turns out to be more accurate than the 2D simulation as a result of a relatively precise description of the turbulent phenomena inside the torch using a more realistic model of arc root attachment. Finally, it is suggested that the 3D transient formulation is indeed required for describing the real arc discharge phenomena inside the torch, while the 2D stationary approach is sometimes useful for getting practical information about the time-averaged plasma characteristics outside the torch because of its simplicity and rapidness in computation.

Bed shear stress that is relevant for bed-load transport calculation is compared for a calibrated 1D and 2D numerical model for different channel geometries. With focus on the wall friction effect for different aspect ratios it is illustrated that for the prediction of cross-sectional averaged longitudinal bed-profiles a 2D model is not more precise per se than a 1D model. The 1D approach considers wall friction effects by the hydraulic bed radius for any aspect ratio. The 2D approach is capable to adequately consider wall roughness effects only by the use of a turbulence model. Otherwise bed shear stress will be overestimated in compact channels. Herein an algebraic turbulence model is applied that introduces additional uncertainties and unknown variables to be calibrated. Numerical 1D and 2D model simulations in compact channels are compared with flume data focusing on the lateral velocity and bed-shear stress distribution. Furthermore, the expansion of a narrow channel to a widened section is investigated. The results of the simulations using the algebraic turbulence model in combination with adjusted wall roughness are in good agreement with the results of the 1D simulation and experimental data.

Using computational fluid dynamics software, two-dimensional (2D) and three-dimensional (3D) simulation models for simulating the mosaic embedding iron ore sintering (MEBIOS) process were developed on the basis of the concept of the multiply shared space (MUSES) method. When one pellet (diameter: 15 mm) was placed at the centre of a sintering bed, the estimated time variations of temperature at the centre and surface of the pellet by both the 2D and 3D simulations were similar to the corresponding experimental results. The calculated cooling rate of the pellet was comparatively high; however, it could be improved further by introducing the fraction of closed pore in the bed in the simulation model. It was supposed that the 2D simulation of the MEBIOS process was quite effective in decreasing calculation cost; therefore, in the case that several pellets were distributed in lattice and staggered alignments throughout the bed, the 2D model was used for calculating the time variations of temperature at the centre of the pellets. The calculated results showed that the sintering process could not continue when the pellets were distributed in the staggered alignment and the distance between pellet centres was 30 mm. On the other hand, changing the distance between the pellets distributed in the lattice alignment had little effect on the sintering process, and the process accelerated by approximately 300 s due to the high gas velocity around the pellets.

The occurrence in SCM images of contrast reversal (CR) phenomena (i.e. a non-monotonic relationship between the amplitude of the SCM signal and the local carrier concentration) has been investigated theoretically by a three dimensional (3D) simulation model and experimentally by measurements of calibrated staircase structures. The CR effect is commonly ascribed to an improper DC bias voltage, far away from the flat band voltage, and this assumption has been supported in the past by two-dimensional (2D) simulations. Simulations with a 3D model show that CR phenomena are less likely to occur than foreseen by the 2D model. The experimental dC/dV curves are in better agreement with the 3D simulations. However, CR phenomena are observed sometimes in a sporadic way even when the DC bias voltage is correctly set at the experimental flat band voltage. A sudden degradation of the probe-tip is probably the cause of the sporadic occurrence of CR phenomena.

In this paper, the basic principle of Optical Voltage Transformer (OVT) based on Pockels effect is introduced. A comparison is made between transverse Pockels effect and longitudinal Pockels effect. And OVT is unable to present the distribution of internal field directly. Therefore, it is necessary to simulate its electric filed, and the accuracy of the simulation results is important for OVT's design. For the axisymmetric model, in order to improve the efficiency of calculation a three-dimensional (3D) structure is usually simplified as a two-dimensional (2D) model. To compare and analyze the differences between the calculated results obtained by using OVT's voltage sensor head with 2D and 3D models, different shapes of BGO crystal in voltage sensor head are constructed respectively, and the finite element simulation software Ansoft Maxwell is used. The simulation results indicate that the maximum electric field intensity is quite different between 2D and 3D models of sensor head. And in the 3D simulation, different shapes of BGO crystal have different maximum electric field intensity of the sensor head. Compared with 2D simulation, 3D simulation is more real. So in an actual operation situation, it should analyze the OVT with 3D model.

Highlights Bin filler design and bin dimensions determine apple distribution Performance of new apple distribution systems was estimated with 3D simulations Simulated lemniscate scattering path demonstrated improved apple distribution in rectangular bins 3D simulation provides an efficient, informed design decision tool before going into production Abstract. Mechanical harvest platform systems equipped with conveyors were meant to replace the traditional apple-picking ladder and bucket; however, their feasibility has not yet been exhausted. The conveyor belts transport the apples to the bin filler, whose role is to distribute the fruit into the bins. Commercial mechanical harvest platforms are designed to perform well with square bins; however, Israeli apple industry bins are rectangular. This results in a non-uniform apple distribution, which requires human intervention and contributes to apple bruising and economic loss. In the present study, a 3D simulation was used to quantitatively evaluate the performance of three novel bin filler designs (back-and-forth, double disk, and lemniscate) and compare them to commercial bin fillers. The bin filler models were tested for the uniformity of the apples distributed into square and rectangular bins. The angle of repose and the standard deviation of the height of the top layer of apples were calculated. The commercial bin filler model performed better when filling square bins (angle = 12°, SD height = 31 mm) than rectangular bins (angle = 18°, SD height = 71 mm). The lemniscate model (angle = 10°, SD height = 41 mm) outperformed the two others as well as the commercial bin filler model (collapsed: angle = 18°, height = 67 mm). A machine design for the lemniscate model is proposed. The quantitative methods described in this study point to the potential benefit of 3D simulation as an inexpensive means to explore the feasibility of new harvest devices.

Large progress has been realized in modeling conduction heat transfer problems over the past decade by the introduction of high performance compact thermal models (CTMs) mainly developed for thermal design of complicated electronic systems. The objective of this paper is to generalize these advances to convective heat transfer. A new convective CTM is proposed, which offers many advantages over the traditional approach using the heat transfer coefficient (HTC). The latter is simply a zeroth order CTM. The HTC is quite handy and simple, but with unpredictable errors. It can be suitable for hand calculations of simple systems giving rather crude estimates. For a higher precision, users have no other option than time consuming 3D simulations. For large systems, in terms of number of components, 3D simulations can be rapidly impractical. The CTM bridges the gap between both approaches going gradually from “HTC” levels (low precision and calculations time) at the zeroth order, to 3D simulation precision and computing time levels at large orders. Fortunately, like for conduction, a CTM of order of few tens quickly approaches 3D simulation precision levels, while keeping computation time significantly lower than 3D simulation. Moreover, the CTM approach solves conjugate heat transfer problems in a quite elegant way. A “black box” model, developed for fluid domain alone, can be easily combined with classical CTM conduction models to generate good precision predictions for any combination of fluid/solid domains.

Wind induced ovalling vibrations were observed during a storm in October 2002 on several empty silos of a closely spaced group consisting of 8 by 5 thin-walled silos in the port of Antwerp (Belgium). To clarify the cause and location of the observed silo vibrations, a thorough analysis of the aerodynamic pressures on the silo surfaces is required. There- fore, both 2D and 3D computational fluid dynamics (CFD) simulations have been performed. While the 2D simulations mainly aim at studying the influence of the angle of incidence of the wind flow on the location where ovalling vibrations can be observed, the 3D simulations are performed to incorporate 3D flow effects into the analysis and to assess the validity of the conclusions of the 2D simulations. The 3D pressure distribution on the silo walls is applied as an external time dependent load on a 3D finite element model of a silo to determine the structural response. Afterwards, modal projection of the load is performed to determine the contribution of each ovalling mode shape to the dynamic structural response. For the 2D simulations, a similar technique of harmonic decomposition is derived and validated with the 3D one-way coupling approach. The results of both approaches yield evidence of the onset of ovalling vibrations, corresponding to the observed pattern of oscillations in the Antwerp silo group.