Origin of gyrotropic/non gyrotropic ion populations in the earth's quasi-perpendicular ion foreshock: Full-particle 2D simulation results

2014 ◽  
Author(s):  
Philippe Savoini ◽  
Bertrand Lembege
Keyword(s):  
2D Simulation ◽  
Simulation Results

How Computational Grid Refinement in Three Dimensions Affects CFD-DEM Results for Psuedo-2D Fluidized Gas-Solid Beds

2017 ◽  
Author(s):  
Annette Volk ◽  
Urmila Ghia
Keyword(s):  
Three Dimensional ◽  
Computational Grid ◽  
Three Dimensions ◽  
Computational Grids ◽  
Grid Refinement ◽  
2D Simulation ◽  
Computational Fluid Dynamics Cfd ◽  
Bed Thickness ◽  
Simulation Results ◽  
Accuracy Of Results

Computational Fluid Dynamics (CFD)-Discrete Element Method (DEM) simulations are designed to model a pseudo-two-dimensional fluidized bed. Bed behavior and accuracy of results are shown to change as the simulations are conducted on increasingly refined computational grids. Trends of the results with grid refinement are reported for both three-dimensional, uniform refinement, and for grid refinement in only the direction of bed thickness. Pseudo-2D simulation results are examined against previously published experimental data to assess relative accuracy compared to fully 3D simulation results. Two drag laws are employed in the simulations, resulting in different trends of results with computational grid refinement. From these results, we present suggestions for accurate model design.

EULERIAN NUMERICAL METHOD FOR SIMULATION OF EXPLOSION PROBLEMS

2009 ◽  
Vol 23 (03) ◽  
pp. 497-500 ◽  
Author(s):  
TIANBAO MA ◽  
JIANGUO NING ◽  
CHENG WANG
Keyword(s):  
Numerical Method ◽  
Reconstruction Algorithm ◽  
Adaptive Grid ◽  
Simulation Software ◽  
Numerical Tests ◽  
2D Simulation ◽  
Eulerian Method ◽  
Interface Reconstruction ◽  
Subdivision Algorithm ◽  
Simulation Results

This paper presents an adaptive grid subdivision algorithm based on the Youngs' interface reconstruction algorithm to treat the advection of the mixed grids in the multi-material Eulerian method. The advantage of this algorithm is that it only needs to calculate the advection between pure grids, escaping the complexity encountered in the advection of mixed grids with two materials. In addition, this algorithm is a multi-dimensional advection algorithm, and it can decrease the error encountered in the direction-split advection algorithm. In order to verify the efficiency of the proposed adaptive grid subdivision algorithm in the actual physical field, it is added to the indigenously developed EXPLOSION-2D simulation software, and some numerical tests are performed to demonstrate the utility of this algorithm. The simulation results verify that the adaptive grid subdivision algorithm is simple and efficient.

Simulation of Acoustic Enhancement of Heat Transfer in a Droplet Heat Exchanger

2007 ◽  
Author(s):  
Melaku Habte ◽  
Savas Yavuzkurt
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Acoustic Field ◽  
High Intensity ◽  
Acoustic Fields ◽  
Single Droplet ◽  
Enhancement Of Heat Transfer ◽  
Nusselt Numbers ◽  
2D Simulation ◽  
Simulation Results

Enhancement of heat transfer from a droplet exposed to acoustic fields is investigated. Investigation is part of a research project in enhancing the heat transfer in direct contact heat exchangers. Adding high intensity sound to Droplet Heat Exchanger (DHX) design produces relative gas motion around droplets otherwise entrained in the main flow field. Particles do not get fully entrained in the high frequency acoustic field giving rise to relative velocity. This enhances the heat transfer from droplets. Further benefits could be obtained by acoustic agglomeration of small droplets. DHXs have high contact area, no interface losses, low pressure drop and superior heat transfer characteristics compared to standard heat exchangers. With further enhancement of heat transfer by high intensity acoustic field application makes DHXs very attractive in many industrial applications such as droplet/particle reactors, humidifiers, gas scrubbers as well as ground based power generating gas turbines. In this paper, results of simulations of a single droplet exposed to acoustic fields of a range of sound intensity level (SPL) and frequency are presented. Spherical droplets are exposed to high intensity acoustic fields up to 175 dB with frequencies 25–2000Hz. Droplet size considered here is 100μm. Three dimensional (3-D) simulation of an oscillating flow field around a spherical droplet are carried out using FLUENT code. First, simulation results of space-averaged Nusselt numbers for steady flow around a single droplet are compared with available experimental data. Results were within 1–5% of each other. Simulations with acoustic field with and without steady velocity component were carried out and the results were compared with previous two dimensional studies as well as experimental and correlations of the same phenomena. The current simulation results are on average 22% higher than the 2D simulation results indicating the 3D nature of the flow. Space and time-averaged Nusselt numbers were more than 400% higher than the ones obtained without the acoustic field for acoustic Reynolds number 100 and frequency 50Hz and 30% higher than 2D simulation results. Finally, entrainment of droplets in the oscillating flow field was also considered. The result showed insignificant reduction (< 1%) in heat transfer rate compared to the case with no entrainment at all ranges of frequency (50–2000Hz).

Numerical Investigation of Scour Around Subsea Pipelines Near the Seabed

2019 ◽  
Author(s):  
Guang Yin ◽  
Zhen Cheng ◽  
Shengnan Liu ◽  
Muk Chen Ong
Keyword(s):  
Granular Flow ◽  
Present Model ◽  
Scour Depth ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Simulations ◽  
2D Simulation ◽  
Binary Collisions ◽  
Simulation Results ◽  
Subsea Pipelines

Abstract In the present study, two-phase flow simulations using SedFoam (an open-source multi-dimensional Eulerian two-phase solver based on OpenFOAM) are employed to investigate the scour phenomenon around pipelines in the vicinity of the seabed. A complete transport profile from the immobile bed, to slowly moving quasi-static bed and upper transport layers can be captured by the present model. The fluid Reynolds stress is modeled using the two-phase k-ε model. The particle stresses due to binary collisions and enduring contacts are modeled by kinetic theory for granular flow and a phenomenological frictional model, respectively. The model is first validated through a two-dimensional (2D) simulation of scour around a single pipeline near the seabed. The predicted time-dependent scour profiles as well as the scour depth are compared with the simulation results of Lee et al. (2016) and the experimental data reported by Mao (1986). A numerical experiment is then carried out to investigate the scour around the piggyback near the seabed. The effects of different locations of the small pipeline on the scour depth are studied.

scholarly journals HYSTERESIS OF PLANAR DOUBLE SLOT IMPINGING AIR JETS

2018 ◽  
Vol 180 ◽  
pp. 02109
Author(s):  
Tomáš Tisovský ◽  
Tomáš Vít
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Isothermal Flow ◽  
Field Pattern ◽  
Stagnation Flow ◽  
Slot Nozzle ◽  
Air Jets ◽  
2D Simulation ◽  
Field Patterns ◽  
Simulation Results

In present study, the bistability and hysteresis of the non-isothermal flow behind two slot nozzle is numerically investigated. Theoretical review of bistability of isothermal stagnation flow is presented and both flow field patterns that exist in the region of bistability are commented on. Hysteresis is found in number of conducted simulations and effects of various parameter changes are discussed. Moreover, the mechanism of transition from one flow field pattern to another is discussed for both transition directions. In conclusion, validity of 2D simulation results against real 3D problems is of concern and general contribution of this research is discussed. Throughout this work, emphasis is on applications regarding heat transfer.

2D Simulation of the Gas-Solid Two Phase Flow inside the Abrasive Jet (AJ) Nozzle

2008 ◽  
Vol 53-54 ◽  
pp. 369-373
Author(s):  
Rong Guo Hou ◽  
Chuan Zhen Huang ◽  
Y.S. Feng ◽  
Y.Y. Liu
Keyword(s):  
Flow Field ◽  
Two Phase Flow ◽  
Cone Angle ◽  
Multiphase Model ◽  
Phase Flow ◽  
Fatigue Wear ◽  
Two Phase ◽  
2D Simulation ◽  
Jet Nozzle ◽  
Simulation Results

The simulation of the gas-solid two phase flow inside the abrasive jet nozzle is studied by the computed dynamic software (CFD)-FLUENT, the velocity field of the two phase flow and the trajectory of the abrasive inside the nozzle are obtained. The Eulerian multiphase model and the DPM model have been used to compute the two-phase flow field. The simulation results express that the velocity of the jet is slow at the inlet, while it will be increased with the area of the section decreasing, the cone angle of the nozzle affects the flow field very much, the flow has low turbulence and the gradient of the velocity is small when the cone angle is small, while the velocity of the flow increased rapidly and the gradient of the velocity is big when the cone angle increasing. The simulation results also express that the arc radius affects the flow field greatly, the flow will move more smoothly when the arc radius is large. The pressure field of the wall expresses that the nozzle will wear rapidly at the corner of the nozzle, the reason is that the pressure is big or changed greatly, the fatigue wear and the blast wear will happen at those place.

scholarly journals Simulation Study of 4H-SiC Trench Insulated Gate Bipolar Transistor with Low Turn-Off Loss

Micromachines ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 815
Author(s):  
Hong-kai Mao ◽  
Ying Wang ◽  
Xue Wu ◽  
Fang-wen Su
Keyword(s):  
Doping Concentration ◽  
Bipolar Transistor ◽  
Simulation Tool ◽  
Electrical Characteristics ◽  
Insulated Gate Bipolar Transistor ◽  
2D Simulation ◽  
Traditional Structure ◽  
Design Idea ◽  
Simulation Results ◽  
Silvaco Atlas

In this work, an insulated gate bipolar transistor (IGBT) is proposed that introduces a portion of the p-polySi/p-SiC heterojunction on the collector side to reduce the tail current during device turn-offs. By adjusting the doping concentration on both sides of the heterojunction, the turn-off loss is further reduced without sacrificing other characteristics of the device. The electrical characteristics of the device were simulated through the Silvaco ATLAS 2D simulation tool and compared with the traditional structure to verify the design idea. The simulation results show that, compared with the traditional structure, the turn-off loss of the proposed structure was reduced by 58.4%, the breakdown voltage increased by 13.3%, and the forward characteristics sacrificed 8.3%.

A 2D Simulation of Grain Boundary Geometry for Normal Grain Growth

2010 ◽  
Vol 663-665 ◽  
pp. 990-994
Author(s):  
Xun Luo ◽  
Wei Zhao
Keyword(s):  
Grain Growth ◽  
Single Phase ◽  
Polycrystalline Materials ◽  
Two Phase ◽  
2D Simulation ◽  
Key Factor ◽  
Current Point ◽  
Phase Systems ◽  
Simulation Results ◽  
Grain Core

This paper proposed a new 2D method to simulate the microstructure for normal grain growth of polycrystalline materials. In this method, the sample was discretized into geometry points and a straightforward geometric construction was implemented to estimate whether the current point was located at the interior of a certain grown grain. The ceramics material was assumed isotropic; furthermore, the single-phase and two-phase systems without pores were discussed respectively. So each grain core would grow up at the same velocity in all directions until it met another growing core in single-phase systems, while in two-phase systems, there would be two sorts of cores with different growing velocities. The ratio of these different velocities was the key factor of the sample microstructures after sintering. The simulation results and the analysis showed that the proposed method agree well with the experimental observation.

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