Three-dimensional global fluid simulations of cylindrical magnetized plasmas
DEFF Research Database (Denmark)
Naulin, Volker; Windisch, T.; Grulke, O.
2008-01-01
. Thus, it is possible to assess the reproductive and predictive capabilities of plasma simulations in unprecedented detail. Here, three-dimensional global fluid simulations of a cylindrical magnetized plasma are presented. This plasma is characterized by the existence of spatially localized sources...... and sinks. The traditional scale separation paradigm is not applied in the simulation model to account for the important evolution of the background profiles due to the dynamics of turbulent fluctuations. Furthermore, the fluid modeling of sheath boundary conditions, which determine the plasma conditions...
Three-Dimensional Simulation of Plasma Jet and Particle Groups in Plasma Spraying
Institute of Scientific and Technical Information of China (English)
FAN Qun-bo; WANG Lu; WANG Fu-chi
2008-01-01
The temperature field, velocity field, as well as species distribution in three-dimensional space are successfully calculated by establishing three-dimensional geometry model and solving plasma jet-substrate interaction equations, optimized particle trajecory models, as well as particle-particle heat transfer equations in three-dimensionalal space. Under typical working conditions, the flying trajectories and distribution of ZrO2 ceramic particles and Ni metal particles are also simulated. Results show that, the plasma jet becomes wider near the substrate, and the stochastic trajectory model is preferable to simulate the turbulent diffusion effect of particles. In addition, Ni metal particles penetrate relatively more deeply than ZrO2 ceramic particles due to larger density.
Fully three-dimensional simulation and modeling of a dense plasma focus
Energy Technology Data Exchange (ETDEWEB)
Meehan, B. T.; Niederhaus, J. H. J.
2014-10-01
A dense plasma focus (DPF) is a pulsed-power machine that electromagnetically accelerates and cylindrically compresses a shocked plasma in a Z-pinch. The pinch results in a brief (~ 100 ns) pulse of X-rays, and, for some working gases, also a pulse of neutrons. A great deal of experimental research has been done into the physics of DPF reactions, and there exist mathematical models describing its behavior during the different time phases of the reaction. Two of the phases, known as the inverse pinch and the rundown, are approximately governed by magnetohydrodynamics, and there are a number of well-established codes for simulating these phases in two dimensions or in three dimensions under the assumption of axial symmetry. There has been little success, however, in developing fully three-dimensional simulations. In this work we present three-dimensional simulations of DPF reactions and demonstrate that three-dimensional simulations predict qualitatively and quantitatively different behavior than their two-dimensional counterparts. One of the most important quantities to predict is the time duration between the formation of the gas shock and Z-pinch, and the three-dimensional simulations more faithfully represent experimental results for this time duration and are essential for accurate prediction of future experiments.
Three-dimensional discharge simulation of inductively coupled plasma (ICP) etching reactor
Institute of Scientific and Technical Information of China (English)
2008-01-01
More and more importance has been attached to inductively coupled plasma (ICP) in semiconductor manufacture. For a deep understanding of the plasma discharge process in the etching reactor, this study made a three-dimensional simulation on the Ar plasma discharge process with the commercial software CFD-ACE, which is according to the real experiment conditions and data supplied by North Microelec-tronic Corporation. The error of the simulation results is in the range of ±20% with credibility. The numerical results show that the three-dimentional spatial distribu-tion of electron density is reduced from the chamber center to the wall. The distri-bution of electron density, electron temperature and power deposition is related to the shape and placement of the coil.
Three-Dimensional Numerical Simulation of Surface-Wave Plasma Source
Institute of Scientific and Technical Information of China (English)
LAN Chaohui; CHEN Zhaoquan; LIU Minghai; JIANG Zhonghe; HU Xiwei
2009-01-01
A three-dimensional model of a surface-wave plasma(SWP)source is built numerically using the finite-difference time-domain(FDTD)method to investigate the structure of the surface wave propagation along the plasma-dielectric interface and the distributions of electromagnetic fields in the whole system.A good-performance excitation source technique for the waveguide which is pivotal to the simulation is presented.The technique can avoid the dc distortions of magnetic fields caused by the forcing electric wall.An example of simulation is given to confirm the existence of the surface waves.The simulation also shows that the code developed is a useful tool in the computer-aided design of the antenna of the SWP source.
Fully Three-dimensional Simulation and Modeling of a Dense Plasma Focus
Meehan, B T
2014-01-01
A Dense Plasma Focus (DPF) is a pulsed-power machine that electromagnetically accelerates and cylindrically compresses a shocked plasma in a Z-pinch. The pinch results in a brief (about 100 nanosecond) pulse of X-rays, and, for some working gases, also a pulse of neutrons. A great deal of experimental research has been done into the physics of DPF reactions, and there exist mathematical models describing its behavior during the different time phases of the reaction. Two of the phases, known as the inverse pinch and the rundown, are approximately governed by magnetohydrodynamics, and there are a number of well-established codes for simulating these phases in two dimensions or in three dimensions under the assumption of axial symmetry. There has been little success, however, in developing fully three-dimensional simulations. In this work we present three-dimensional simulations of DPF reactions and demonstrate that 3D simulations predict qualitatively and quantitatively different behavior than their 2D counterp...
Three-dimensional simulation of laser–plasma-based electron acceleration
Indian Academy of Sciences (India)
A Upadhyay; K Patel; B S Rao; P A Naik; P D Gupta
2012-04-01
A sequential three-dimensional (3D) particle-in-cell simulation code PICPSI-3D with a user friendly graphical user interface (GUI) has been developed and used to study the interaction of plasma with ultrahigh intensity laser radiation. A case study of laser–plasma-based electron acceleration has been carried out to assess the performance of this code. Simulations have been performed for a Gaussian laser beam of peak intensity 5 × 1019 W/cm2 propagating through an underdense plasma of uniform density 1 × 1019 cm-3, and for a Gaussian laser beam of peak intensity 1.5 × 1019 W/cm2 propagating through an underdense plasma of uniform density 3.5 × 1019 cm-3. The electron energy spectrum has been evaluated at different time-steps during the propagation of the laser beam. When the plasma density is 1 × 1019 cm-3, simulations show that the electron energy spectrum forms a monoenergetic peak at ∼ 14 MeV, with an energy spread of ± 7 MeV. On the other hand, when the plasma density is 3.5 × 1019 cm-3, simulations show that the electron energy spectrum forms a monoenergetic peak at ∼ 23 MeV, with an energy spread of ± 7.5 MeV.
Magnetic nulls in three-dimensional kinetic simulations of space plasmas
Olshevsky, Vyacheslav; Deca, Jan; Divin, Andrey; Peng, Ivy Bo; Markidis, Stefano; Innocenti, Maria Elena; Cazzola, Emanuele; Lapenta, Giovanni
2016-04-01
We present a survey of magnetic nulls and associated energy dissipation in different three-dimensional kinetic particle-in-cell simulations of space plasmas. The configurations under study include: a traditional Harris current sheet and current sheets with asymmetric density distribution, dipolar and quadrupolar planetary magnetospheres, lunar magnetic anomalies, and decaying turbulence. Nulls are detected in the simulation snapshots by the topological degree method. In all runs except the quadrupolar magnetospere the dominating majority of nulls are of spiral topological type. When supported by strong currents, these nulls indicate the regions of strong energy dissipation. Dissipation, often accompanied by the changes in magnetic topology, is caused by plasma instabilities in the current channels or on their interfaces. Radial nulls show less activity, they can be created or destroyed in pairs, via topological bifurcations. Although such events demonstrate energy release, they are rather rare and short-living. An important implication of our study to observations is that magnetic topology should not be considered independently of other plasma properties such as currents.
Three-dimensional simulation study of compact toroid plasmoid injection into magnetized plasmas
Energy Technology Data Exchange (ETDEWEB)
Suzuki, Y.; Watanabe, T.-H.; Sato, T.; Hayashi, T. [National Inst. for Fusion Science, Toki, Gifu (Japan)
1999-04-01
Three-dimensional dynamics of a compact toroid (CT) plasmoid, which is injected into a magnetized target plasma region is investigated by using magnetohydrodynamic (MHD) numerical simulations. It is found that the process of the CT penetration into this region is much more complicated than what has been analyzed so far by using a conducting sphere (CS) model. The injected CT suffers from a tilting instability, which grows with the similar time scale as the CT penetration. The instability is accompanied by magnetic reconnection between the CT magnetic field and the target magnetic field, which disrupts the magnetic configuration of the CT. Magnetic reconnection plays a role to supply the high density plasma initially confined in the CT magnetic field into the target region. Also, the penetration depth of the CT high density plasma is examined. It is shown to be shorter than that estimated from the CS model. The CT high density plasma is decelerated mainly by the Lorentz force of the target magnetic field, which includes not only the magnetic pressure force but also the magnetic tension force. Furthermore, by comparing the CT plasmoid injection with the bare plasmoid injection, magnetic reconnection is considered to relax the magnetic tension force, that is the deceleration of the CT plasmoid. (author)
Energy Technology Data Exchange (ETDEWEB)
Horiuchi, Ritoku; Sato, Tetsuya [Theory and Computer Simulation Center, National Inst. for Fusion Science, Toki, Gifu (Japan)
1999-06-01
Generation of anomalous resistivity and dynamical development of collisionless reconnection in the vicinity of a magnetically neutral sheet are investigated by means of a three-dimensional particle simulation. For no external driving source, two different types of plasma instabilities are excited in the current layer. The lower hybrid drift instability (LHDI) is observed to grow in the periphery of current layer in an early period, while a drift kink instability (DKI) is triggered at the neutral sheet in a late period as a result of the nonlinear deformation of the current sheet by the LHDI. A reconnection electric field grows at the neutral sheet in accordance with the excitation of the DKI. When an external driving field exists, the convective electric field penetrates into the current layer through the particle kinetic effect and collisionless reconnection is triggered by the convective electric field earlier than the DKI is excited. It is also found that the anisotropic ion distribution is formed through the anomalous ion heating by the DKI. (author)
HIDENEK: An implicit particle simulation of kinetic-MHD phenomena in three-dimensional plasmas
Tanaka, Motohiko
1993-05-01
An advanced 'kinetic-MHD' simulation method and its applications to plasma physics are given in this lecture. This method is quite stable for studying strong nonlinear, kinetic processes associated with large space-scale, low-frequency electromagnetic phenomena of plasmas. A full set of the Maxwell equations, and the Newton-Lorentz equations of motion for particle ions and guiding-center electrons are adopted. In order to retain only the low-frquency waves and instabilities, implicit particle-field equations are derived. The present implicit-particle method is proved to reproduce the MHD eigenmodes such as Alfven, magnetosonic and kinetic Alfven waves in a thermally near-equilibrium plasma. In the second part of the lecture, several physics applications are shown. These include not only the growth of the instabilities of beam ions against the background plasmas and helical link of the current, but they also demonstrate nonlinear results such as pitch-angle scattering of the ions. Recent progress in the simulation of the Kelvin-Helmholtz instability is also presented with a special emphasis on the mixing of the plasma particles.
MHD simulations of three-dimensional Resistive Reconnection in a cylindrical plasma column
Striani, Edoardo; Vaidya, Bhargav; Bodo, Gianluigi; Ferrari, Attilio
2016-01-01
Magnetic reconnection is a plasma phenomenon where a topological rearrangement of magnetic field lines with opposite polarity results in dissipation of magnetic energy into heat, kinetic energy and particle acceleration. Such a phenomenon is considered as an efficient mechanism for energy release in laboratory and astrophysical plasmas. An important question is how to make the process fast enough to account for observed explosive energy releases. The classical model for steady state magnetic reconnection predicts reconnection times scaling as $S^{1/2}$ (where $S$ is the Lundquist number) and yields times scales several order of magnitude larger than the observed ones. Earlier two-dimensional MHD simulations showed that for large Lundquist number the reconnection time becomes independent of $S$ ("fast reconnection" regime) due to the presence of the secondary tearing instability that takes place for $S \\gtrsim 1 \\times 10^4$. We report on our 3D MHD simulations of magnetic reconnection in a magnetically confin...
MHD simulations of three-dimensional resistive reconnection in a cylindrical plasma column
Striani, E.; Mignone, A.; Vaidya, B.; Bodo, G.; Ferrari, A.
2016-11-01
Magnetic reconnection is a plasma phenomenon where a topological rearrangement of magnetic field lines with opposite polarity results in dissipation of magnetic energy into heat, kinetic energy and particle acceleration. Such a phenomenon is considered as an efficient mechanism for energy release in laboratory and astrophysical plasmas. An important question is how to make the process fast enough to account for observed explosive energy releases. The classical model for steady state magnetic reconnection predicts reconnection times scaling as S1/2 (where S is the Lundquist number) and yields time-scales several order of magnitude larger than the observed ones. Earlier two-dimensional MHD simulations showed that for large Lundquist number the reconnection time becomes independent of S (`fast reconnection' regime) due to the presence of the secondary tearing instability that takes place for S ≳ 1 × 104. We report on our 3D MHD simulations of magnetic reconnection in a magnetically confined cylindrical plasma column under either a pressure balanced or a force-free equilibrium and compare the results with 2D simulations of a circular current sheet. We find that the 3D instabilities acting on these configurations result in a fragmentation of the initial current sheet in small filaments, leading to enhanced dissipation rate that becomes independent of the Lundquist number already at S ≃ 1 × 103.
Institute of Scientific and Technical Information of China (English)
Lan Chao-Hui; Lan Chao-Zhen; Hu Xi-Wei; Chen Zhao-Quan; Liu Ming-Hai
2009-01-01
A self-consistent and three-dimensional (3D) model of argon discharge in a large-scale rectangular surface-wave plasma (SWP) source is presented in this paper, which is based on the finite-difference time-domain (FDTD) approximation to Maxwell's equations self-consistently coupled with a fluid model for plasma evolution. The discharge characteristics at an input microwave power of 1200 W and a filling gas pressure of 50 Pa in the SWP source are analyzed. The simulation shows the time evolution of deposited power density at different stages, and the 3D distributions of electron density and temperature in the chamber at steady state. In addition, the results show that there is a peak of plasma density approximately at a vertical distance of 3 cm from the quartz window.
Three dimensional Simulations of Self-Organization in a Driven Dissipative Plasma System
Shaikh, Dastgeer; Dasgupta, B.; Hu, Q.; Zank, G. P.
2009-11-01
We perform a fully self-consistent 3-D numerical simulation for a compressible, driven dissipative magneto-plasma driven by large-scale perturbations, that contain a fairly broader spectrum of characteristic modes, ranging from largest scales to intermediate scales and down to the smallest scales, where the energy of the system are dissipated by collisional (Ohmic) and viscous dissipations. Additionally, our simulation includes nonlinear interactions amongst a wide range of ?uctuations that are initialized with random spectral amplitudes, leading to the cascade of spectral energy in the inertial range spectrum, and takes into account large scale as well as small scale perturbation that may have been induced by the background plasma ?uctuations, also the non adiabatic exchange of energy leading to the migration of energy from the energy containing modes or randomly injected energy driven by perturbations and further dissipated by the smaller scales. Besides demonstrating the comparative decays of total energy and dissipation rate of energy, our results show the existence of a perpendicular component of current, thus clearly con?rming that the self-organized state is non-force free.
Beauvais, S.; Guipont, V.; Jeandin, M.; Jeulin, D.; Robisson, A.; Saenger, R.
2008-11-01
Porosity is a key feature of a thermally sprayed coating microstructure. Within ceramic coatings, porosity is made of pores and cracks of various shapes, dimensions, and orientations. Cracks can be intralamellar or interlamellar due to the buildup of the coating, which leads to piled-up lamellae from impinging and the additional rapid solidification of liquid droplets. Pores are interconnected with cracks, which results in a three-dimensional (3-D) porosity network. Direct observation of this network is an intricate task and current attempts remain somewhat limited. A 3-D simulation of this network was, therefore, developed in this work, based on a stochastic approach to the building up of simulated lamellae in the sprayed microstructure. A library of mathematical objects was achieved from morphological measurements, using confocal microscopy of actual isolated flattened lamellae, i.e., “splats” and scanning electron microscopy (SEM). This stochastic approach to the simulation of hundreds of lamellae also involves the random distribution of cracks and pores. Simulation fit parameters were selected according to the overall characteristics of porosity ( i.e., content, orientation, size, etc.) that were determined from the thorough quantitative image analysis (QIA) of cross-sectioned plasma-sprayed alumina coatings. Two plasma modes that varied the atmosphere in a controlled-atmosphere plasma spraying (CAPS) chamber were applied, to produce the microstructures of two different alumina coatings. The 3-D random modeling tool allowed the processing of a volume of digital material through a 3-D simulated binary image of a two-phased composite material. Using one 3-D image result of the simulation, finite element (FE) calculations were performed, in order to study the overall dielectric properties of a plasma-sprayed alumina as a function of porosity. The influence of anisotropy is discussed, in particular, and both analytical and numerical predicted values were
Three dimensional simulations of plasma filaments in the scrape off layer
DEFF Research Database (Denmark)
Easy, L.; Militello, F.; Omotani, J.
2014-01-01
This paper presents simulations of isolated 3D filaments in a slab geometry obtained using a newly developed 3D reduced fluid code, written using the BOUT++ framework. First, systematic scans were performed to investigate how the dynamics of a filament are affected by its amplitude, perpendicular...
Energy Technology Data Exchange (ETDEWEB)
Kuwabara, T. [Institute of Materials and Systems for Sustainability, Nagoya University, Nagoya (Japan); Tanaka, H.; Kobayashi, M. [National Institute for Fusion Science, Toki (Japan); SOKENDAI (The Graduate University For Advanced Studies), Toki (Japan); Kawamura, G. [National Institute for Fusion Science, Toki (Japan); Ohno, N.; Nishikata, H. [Graduate School of Engineering, Nagoya University, Nagoya (Japan); Feng, Y. [Max-Planck-Institut fuer Plasmaphysik, Euratom Association, Garching/Greifswald (Germany)
2016-08-15
We have adapted the EMC3-EIRENE code for modeling of a linear divertor plasma simulator in order to demonstrate plasma-wall interactions with three-dimensional (3D) effects. 3D distributions of hydrogen plasma and neutrals can be successfully calculated for four different types of target plates: a V-shaped target, inclined targets with open and closed structures, and a planer target. Hydrogen atoms and molecules are accumulated more effectively in the V-shaped target plate, leading to a higher electron density with lower electron temperature than the planar target plate. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Voitcu, Gabriel
2016-01-01
In this paper we use three-dimensional electromagnetic particle-in-cell simulations to investigate the interaction of a small-Larmor radius plasma cloud/jet with a transverse non-uniform magnetic field typical to a tangential discontinuity in a parallel geometry. The simulation setup corresponds to an idealized, yet relevant, magnetospheric configuration likely to be observed at the magnetopause during northward orientation of the interplanetary magnetic field. The numerical simulations are adapted to study the kinetic effects and their role on the transport and entry of localized plasma jets similar to those identified inside the Earth's magnetosheath propagating towards the magnetopause. The simulations reveal the formation of a polarization electric field inside the main bulk of the plasma cloud that enables its forward transport and entry across the transverse magnetic field. The jet is able to penetrate the transition region when the height of the magnetic barrier does not exceed a certain critical thres...
Zheng, Chun-Yang; Zhu, Shao-Ping; He, Xian-Tu
2002-07-01
The quasi-static magnetic fields created in the interaction of relativistic laser pulses with under-dense plasmas have been investigated by three-dimensional particle-in-cell simulation. The relativistic ponderomotive force can drive an intense electron current in the laser propagation direction, which is responsible for the generation of a helical magnetic field. The axial magnetic field results from a difference beat of wave-wave, which drives a solenoidal current. In particular, the physical significance of the kinetic model for the generation of the axial magnetic field is discussed.
Application of Simulated Three Dimensional CT Image in Orthognathic Surgery
Energy Technology Data Exchange (ETDEWEB)
Kim, Hyun Don; Park, Chang Seo [Dept. of Dental Radiology, College of Dentistry, Yensei University, Seoul (Korea, Republic of); Yoo, Sun Kook; Lee, Kyoung Sang [Dept. of Medical Engineering, College of Medicine, Yensei University, Seoul (Korea, Republic of)
1998-08-15
In orthodontics and orthognathic surgery, cephalogram has been routine practice in diagnosis and treatment evaluation of craniofacial deformity. But its inherent distortion of actual length and angles during projecting three dimensional object to two dimensional plane might cause errors in quantitative analysis of shape and size. Therefore, it is desirable that three dimensional object is diagnosed and evaluated three dimensionally and three dimensional CT image is best for three dimensional analysis. Development of clinic necessitates evaluation of result of treatment and comparison before and after surgery. It is desirable that patient that was diagnosed and planned by three dimensional computed tomography before surgery is evaluated by three dimensional computed tomography after surgery, too. But Because there is no standardized normal values in three dimension now and three dimensional Computed Tomography needs expensive equipment and because of its expenses and amount of exposure to radiation, limitations still remain to be solved in its application to routine practice. If postoperative three dimensional image is constructed by pre and postoperative lateral and postero-anterior cephalograms and preoperative three dimensional computed tomogram, pre and postoperative image will be compared and evaluated three dimensionally without three dimensional computed tomography after surgery and that will contribute to standardize normal values in three dimension. This study introduced new method that computer-simulated three dimensional image was constructed by preoperative three dimensional computed tomogram and pre and postoperative lateral and postero-anterior cephalograms, and for validation of new method, in four cases of dry skull that position of mandible was displaced and four patients of orthognathic surgery, computer-simulated three dimensional image and actual postoperative three dimensional image were compared. The results were as follows. 1. In four cases of
Three-dimensional simulations of resistance spot welding
DEFF Research Database (Denmark)
Nielsen, Chris Valentin; Zhang, Wenqi; Perret, William
2014-01-01
This paper draws from the fundamentals of electro-thermo-mechanical coupling to the main aspects of finite element implementation and three-dimensional modelling of resistance welding. A new simulation environment is proposed in order to perform three-dimensional simulations and optimization of r...
Three-dimensional simulation of a microplasma pump
Wang, Chin-Cheng; Roy, Subrata
2009-09-01
We present a three-dimensional simulation of dielectric barrier discharge (DBD) using the finite element based multiscale ionized gas (MIG) flow code. The two-species hydrodynamic plasma model coupled Poisson equation and Navier-Stokes equation are solved using MIG flow code to predict complicated flow structure inside a plasma induced micropump. The advantage of such a micropump is rapid on/off switching without any moving parts. Results show a reasonable distribution for ion and electron densities as well as an electric field. The key factors of microplasma pump design are the location of actuators and input voltage. The flow rate of the microplasma pump is on the order of ml min-1. Such a flow rate may be beneficial for micropropulsion in space.
Institute of Scientific and Technical Information of China (English)
郑春阳; 朱少平; 贺贤土
2002-01-01
The quasi-static magnetic fields created in the interaction of relativistic laser pulses with under-dense plasmashave been investigated by three-dimensional particle-in-cell simulation. The relativistic ponderomotive force candrive an intense electron current in the laser propagation direction, which is responsible for the generation ofa helical magnetic field. The axial magnetic field results from a difference beat of wave-wave, which drives asolenoidal current. In particular, the physical significance of the kinetic model for the generation of the axialmagnetic field is discussed.
Three dimensional filamentary structures of a relativistic electron beam in Fast Ignition plasmas
Karmakar, Anupam; Pukhov, Alexander
2008-01-01
The filamentary structures and associated electromagnetic fields of a relativistic electron beam have been studied by three dimensional particle-in-cell (PIC) simulations in the context of Fast Ignition fusion. The simulations explicitly include collisions in return plasma current and distinctly examine the effects of beam temperature and collisions on the growth of filamentary structures generated.
Three-dimensional conceptual model for service-oriented simulation
Institute of Scientific and Technical Information of China (English)
Wen-guang WANG; Wei-ping WANG; Justyna ZANDER; Yi-fan ZHU
2009-01-01
In this letter, we propose a novel three-dimensional conceptual model for an emerging service-oriented simulation paradigm. The model can be used as a guideline or an analytic means to find the potential and possible future directions of the current simulation frameworks, In particular, the model inspects the crossover between the disciplines of modeling and simulation,service-orientation, and software/systems engineering. Finally, two specific simulation frameworks are studied as examples.
Three-dimensional conceptual model for service-oriented simulation
Wang, Wenguang; Zander, Justyna; Zhu, Yifan; 10.1631/jzus.A0920258
2009-01-01
In this letter, we propose a novel three-dimensional conceptual model for an emerging service-oriented simulation paradigm. The model can be used as a guideline or an analytic means to find the potential and possible future directions of the current simulation frameworks. In particular, the model inspects the crossover between the disciplines of modeling and simulation, service-orientation, and software/systems engineering. Finally, two specific simulation frameworks are studied as examples.
Three-dimensional wake potential in a streaming dusty plasma
Indian Academy of Sciences (India)
M Salahuddin; M K Islam; A K Banerjee; M Salimullah; S K Ghosh
2003-09-01
The oscillatory wake potential for a slowly moving or static test dust particulate in a ﬁnite temperature, collisionless and unmagnetized dusty plasma with a continuous ﬂow of ions and dust particles has been studied. The collective resonant interaction of the moving test particle with the low-frequency and low-phase-velocity dust-acoustic mode is the origin of the periodic attractive force between the like polarity particulates along and perpendicular to the streaming ions and dust grains resulting into dust-Coulomb crystal formation. This wake potential can explain the three-dimensional dust-Coulomb crystal formation in the laboratory conditions.
Three-dimensional simulations of viscoelastic instability in polymeric filaments
DEFF Research Database (Denmark)
Rasmussen, Henrik Koblitz; Hassager, Ole
1999-01-01
The three-dimensional Langrangian integral method is used to simulate the elastic end-plate instability that occurs in the rapid extension of some polymeric filaments between parallel plates. It is demonstrated that the upper convected Maxwell model describes the essential features of the instabi...
THE SYSTEM SIMULATION OF THREE-DIMENSIONAL RADAR
Institute of Scientific and Technical Information of China (English)
Zhang Wei; Xiang Jingcheng; Wang Xuegang
2004-01-01
To provide a test platform for Electronic Warfare (EW) system, it is needed to simulate the radar received Intermediate Frequency (IF) signals and radar system functions.This letter gives a description of a radar system simulation software developed for frequencyphase scanning three-dimensional (3-D) radar. Experimental results prove that the software could be used for system evaluation and for training purposes as an attractive alternative to real EW system.
Energy Technology Data Exchange (ETDEWEB)
Kourtzanidis, K., E-mail: Konstantinos.Kourtzanidis@onera.fr; Boeuf, J. P. [LAPLACE (Laboratoire Plasma et Conversion d' Energie), Université de Toulouse, UPS, INPT, 118 route de Narbonne, F-31062 Toulouse Cedex 9 (France); Rogier, F. [ONERA - The French Aerospace Lab, 2 Avenue édouard Belin, 31000 Toulouse (France)
2014-12-15
Recent experiments have demonstrated that a freely localized 100 GHz microwave discharge can propagate towards the microwave source with high speed, forming a complex pattern of self-organized filaments. We present three-dimensional simulations of the formation and propagation of such patterns that reveal more information on their nature and interaction with the electromagnetic waves. The developed three-dimensional Maxwell-plasma solver permits the study of different forms of incident field polarization. Results for linear and circular polarization of the wave are presented and comparisons with recent experiments show a good overall agreement. The three dimensional simulations provide a quantitative analysis of the parameters controlling the time and length scales of the strongly non-linear plasma dynamics and could be useful for potential microwave plasma applications such as aerodynamic flow and combustion control.
Three-Dimensional Simulations of Deep-Water Breaking Waves
Brucker, Kyle A; Dommermuth, Douglas G; Adams, Paul
2014-01-01
The formulation of a canonical deep-water breaking wave problem is introduced, and the results of a set of three-dimensional numerical simulations for deep-water breaking waves are presented. In this paper fully nonlinear progressive waves are generated by applying a normal stress to the free surface. Precise control of the forcing allows for a systematic study of four types of deep-water breaking waves, characterized herein as weak plunging, plunging, strong plunging, and very strong plunging.
IF signals simulation of three-dimensional radar
Institute of Scientific and Technical Information of China (English)
Zhang Wei; Wang Xuegang; Zhu Zhaoda
2008-01-01
Based on the analysis of the principles of frequency-phase scanning 3-D (three-dimensional) radar and the scattering mechanism of 3-D radar, the target and clutter IF (intermediate frequency) signals model of frequencyphase scanning 3-D radar is presented. The IF signals model of different channels of 3-D radar is presented in one simple formula in which complex waveform effects are considered. The simulation results obtained during tests are also provided in the end.
Energy Technology Data Exchange (ETDEWEB)
Lore, J. D., E-mail: lorejd@ornl.gov [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Reinke, M. L.; Lipschultz, B. [York Plasma Institute, Department of Physics, University of York, Heslington, York YO10 5DD (United Kingdom); Brunner, D.; LaBombard, B.; Terry, J. [Plasma Science and Fusion Center, MIT, Cambridge, Massachusetts 02139 (United States); Pitts, R. A. [ITER Organization, Route de Vinon-sur-Verdon, CS 90046 - 13067 Saint Paul Lez Durance Cedex (France); Feng, Y. [Max Planck Institute for Plasma Physics, Greifswald (Germany)
2015-05-15
Experiments in Alcator C-Mod to assess the level of toroidal asymmetry in divertor conditions resulting from poloidally and toroidally localized extrinsic impurity gas seeding show a weak toroidal peaking (∼1.1) in divertor electron temperatures for high-power enhanced D-alpha H-mode plasmas. This is in contrast to similar experiments in Ohmically heated L-mode plasmas, which showed a clear toroidal modulation in the divertor electron temperature. Modeling of these experiments using the 3D edge transport code EMC3-EIRENE [Y. Feng et al., J. Nucl. Mater. 241, 930 (1997)] qualitatively reproduces these trends, and indicates that the different response in the simulations is due to the ionization location of the injected nitrogen. Low electron temperatures in the private flux region (PFR) in L-mode result in a PFR plasma that is nearly transparent to neutral nitrogen, while in H-mode the impurities are ionized in close proximity to the injection location, with this latter case yielding a largely axisymmetric radiation pattern in the scrape-off-layer. The consequences for the ITER gas injection system are discussed. Quantitative agreement with the experiment is lacking in some areas, suggesting potential areas for improving the physics model in EMC3-EIRENE.
Three-Dimensional Multiscale MHD Model of Cometary Plasma Environments
Gombosi, Tamas I.; DeZeeuw, Darren L.; Haberli, Roman M.; Powell, Kenneth G.
1996-01-01
First results of a three-dimensional multiscale MHD model of the interaction of an expanding cometary atmosphere with the magnetized solar wind are presented. The model starts with a supersonic and super-Alfvenic solar wind far upstream of the comet (25 Gm upstream of the nucleus) with arbitrary interplanetary magnetic field orientation. The solar wind is continuously mass loaded with cometary ions originating from a 10-km size nucleus. The effects of photoionization, electron impact ionization, recombination, and ion-neutral frictional drag are taken into account in the model. The governing equations are solved on an adaptively refined unstructured Cartesian grid using our new multiscale upwind scalar conservation laws-type numerical technique (MUSCL). We have named this the multiscale adaptive upwind scheme for MHD (MAUS-MHD). The combination of the adaptive refinement with the MUSCL-scheme allows the entire cometary atmosphere to be modeled, while still resolving both the shock and the diamagnetic cavity of the comet. The main findings are the following: (1) Mass loading decelerates the solar wind flow upstream of the weak cometary shock wave (M approximately equals 2, M(sub A) approximately equals 2), which forms at a subsolar standoff distance of about 0.35 Gm. (2) A cometary plasma cavity is formed at around 3 x 10(exp 3) km from the nucleus. Inside this cavity the plasma expands outward due to the frictional interaction between ions and neutrals. On the nightside this plasma cavity considerably narrows and a relatively fast and dense cometary plasma beam is ejected into the tail. (3) Inside the plasma cavity a teardrop-shaped inner shock is formed, which is terminated by a Mach disk on the nightside. Only the region inside the inner shock is the 'true' diamagnetic cavity. (4) The model predicts four distinct current systems in the inner coma: the density peak current, the cavity boundary current, the inner shock current, and finally the cross-tail current
Three-Dimensional Magnetohydrodynamic Simulation of Slapper Initiation Systems
Energy Technology Data Exchange (ETDEWEB)
Christensen, J S; Hrousis, C A
2010-03-09
Although useful information can be gleaned from 2D and even 1D simulations of slapper type initiation systems, these systems are inherently three-dimensional and therefore require full 3D representation to model all relevant details. Further, such representation provides additional insight into optimizing the design of such devices from a first-principles perspective and can thereby reduce experimental costs. We discuss in this paper several ongoing efforts in modeling these systems, our pursuit of validation, and extension of these methods to other systems. Our results show the substantial dependence upon highly accurate global equations of state and resistivity models in these analyses.
Three-dimensional simulation of polytropic accretion discs
Energy Technology Data Exchange (ETDEWEB)
Molteni, D. (Palermo Univ. (Italy). Ist. di Fisica); Belvedere, G.; Lanzafame, G. (Catania Univ. (Italy). Ist. di Astronomia)
1991-04-15
We carried out three-dimensional simulations of the formation and evolution of accretion discs in close binary systems, using the Smoothed Particle Hydrodynamics method to solve the fluid dynamic equations. Although the runs presented here refer to an ideal gas with different polytropic indexes, and constitute the first stage of more physically complex forthcoming simulations, they nevertheless give some interesting results; the disc structure and dynamics are in agreement with standard models only for small {gamma}-values; as a consequence of the z-resolution is found that disc formation is inhibited for {gamma} {ge} 1.2, which means that some 2D simulations of polytropic discs are meaningless; the disc is slightly asymmetric in the x-y plane and its profile is irregular and pulsating at the outer boundary. (Author).
Three-dimensional numerical simulation during laser processing of CFRP
Ohkubo, Tomomasa; Sato, Yuji; Matsunaga, Ei-ichi; Tsukamoto, Masahiro
2017-09-01
We performed three-dimensional numerical simulation about laser processing of carbon-fiber-reinforced plastic (CFRP) using OpenFOAM as libraries of finite volume method (FVM). Although a little theoretical or numerical studies about heat affected zone (HAZ) formation were performed, there is no research discussing how HAZ is generated considering time development about removal of each material. It is important to understand difference of removal speed of carbon fiber and resin in order to improve quality of cut surface of CFRP. We demonstrated how the carbon fiber and resin are removed by heat of ablation plume by our simulation. We found that carbon fiber is removed faster than resin at first stage because of the difference of thermal conductivity, and after that, the resin is removed faster because of its low combustion temperature. This result suggests the existence of optimal contacting time of the laser ablation and kerf of the target.
Three dimensional direct numerical simulation of complex jet flows
Shin, Seungwon; Kahouadji, Lyes; Juric, Damir; Chergui, Jalel; Craster, Richard; Matar, Omar
2016-11-01
We present three-dimensional simulations of two types of very challenging jet flow configurations. The first consists of a liquid jet surrounded by a faster coaxial air flow and the second consists of a global rotational motion. These computations require a high spatial resolution and are performed with a newly developed high performance parallel code, called BLUE, for the simulation of two-phase, multi-physics and multi-scale incompressible flows, tested on up to 131072 threads with excellent scalability performance. The method for the treatment of the fluid interfaces uses a hybrid Front Tracking/Level Set technique that defines the interface both by a discontinuous density field as well as by a local triangular Lagrangian mesh. Coriolis forces are taken into account and solved via an exact time-integration method that ensures numerical accuracy and stability. EPSRC UK Programme Grant EP/K003976/1.
Three-dimensional fracture simulations based on the SDA
Feist, C.; Hofstetter, G.
2007-02-01
A numerical model within the framework of a non-symmetric strong discontinuity approach (SDA) suitable for fracture simulations of plain concrete is presented. The model is based on the fixed crack concept and is formulated within the framework of elements with embedded discontinuities. Discontinuity segments of individual elements are considered to form a C0-continuous surface. Enforcement of continuity of the crack surface across adjacent elements is established by the so-called partial domain crack tracking algorithm (PDTA). Orientation of individual crack segments is derived from a non-local strain field. Within the present work emphasis is put on the formulation for the three-dimensional case. The implications on the respective algorithms are highlighted. The capabilities of the model are shown by means of numerical examples. Copyright
Lattice kinetic simulations in three-dimensional magnetohydrodynamics.
Breyiannis, G; Valougeorgis, D
2004-06-01
A lattice kinetic algorithm to simulate three-dimensional (3D) incompressible magnetohydrodynamics is presented. The fluid is monitored by a distribution function, which obeys a scalar kinetic equation, subject to an external force due to the imposed magnetic field. Following the work of J. Comput. Phys. 179, 95 (2002)], the magnetic field is represented by a different three-component vector distribution function, which obeys a corresponding vector kinetic equation. Discretization of the 3D phase space is based on a 19-bit scheme for the hydrodynamic part and on a 7-bit scheme for the magnetic part. Numerical results for magnetohydrodynamic (MHD) flow in a rectangular duct with insulating and conducting walls provide excellent agreement with corresponding analytical solutions. The scheme maintains in all cases tested the MHD constraint inverted Delta.B=0 within machine round-off error.
A Three Dimensional Simulation Method of the Gantry Crane
Directory of Open Access Journals (Sweden)
Jingsong LI
2013-04-01
Full Text Available Until now, many companies have developed lots of the port machinery remote monitoring systems. However, these monitoring systems usual display the operating status of the port machinery by the schematic diagram, Legend and data. The presentation of information is unable to describe the status of the large number of port machinery. In order to solve the problem, a three-dimensional simulation method of the gantry crane based on the WPF is proposed. This paper studies WPF technology and 3D modeling techniques, on this basis, proposes a kind of the gantry crane 3D simulation method based on WPF, establishes a new generation monitoring system based on 3D, immersive and interactive real-time simulation environment. This system could simulate the real-time 3D virtual scene of the gantry crane, and real-time 3D analog display port machinery running posture and operating environment. Experiments show that CPU and memory usage rate is low enough when the system is running.
Two- and Three-Dimensional Simulations of Asteroid Ocean Impacts
Gisler, G.; Weaver, R. P.; Mader, C. L.; Gittings, M. L.
2003-01-01
We have performed a series of two-dimensional and three-dimensional simulations of asteroid impacts into an ocean using the SAGE code from Los Alamos National Laboratory and Science Applications International Corporation. The SAGE code is a compressible Eulerian hydrodynamics code using continuous adaptive mesh refinement for following discontinuities with a fine grid while treating the bulk of the simulation more coarsely. We have used tabular equations of state for the atmosphere, water, the oceanic crust, and the mantle. In two dimensions, we simulated asteroid impactors moving at 20 km/s vertically through an exponential atmosphere into a 5 km deep ocean. The impactors were composed of mantle material (3.32 g/cc) or iron (7.8 g/cc) with diameters from 250m to 10 km. In our three-dimensional runs we simulated asteroids of 1 km diameter composed of iron moving at 20 km/s at angles of 45 and 60 degrees from the vertical. All impacts, including the oblique ones, produce large underwater cavities with nearly vertical walls followed by a collapse starting from the bottom and subsequent vertical jetting. Substantial amounts of water are vaporized and lofted high into the atmosphere. In the larger impacts, significant amounts of crustal and even mantle material are lofted as well. Tsunamis up to a kilometer in initial height are generated by the collapse of the vertical jet. These waves are initially complex in form, and interact strongly with shocks propagating through the water and the crust. The tsunami waves are followed out to 100 km from the point of impact. Their periods and wavelengths show them to be intermediate type waves, and not (in general) shallow-water waves. At great distances, the waves decay faster than the inverse of the distance from the impact point, ignoring sea-floor topography. For all impactors smaller than about 2 km diameter, the impacting body is highly fragmented and its remains lofted into the stratosphere with the water vapor and crustal
TWO- AND THREE-DIMENSIONAL SIMULATIONS OF ASTEROID OCEAN IMPACTS
Directory of Open Access Journals (Sweden)
Michael Gittings
2003-01-01
Full Text Available We have performed a series of two-dimensional and three-dimensional simulations of asteroid impacts into an ocean using the SAGE code from Los Alamos National Laboratory and Science Applications International Corporation. The SAGE code is a compressible Eulerian hydrodynamics code using continuous adaptive mesh refinement for following discontinuities with a fine grid while treating the bulk of the simulation more coarsely. We have used realistic equations of state for the atmosphere, sea water, the oceanic crust, and the mantle. In two dimensions, we simulated asteroid impactors moving at 20 km/s vertically through an exponential atmosphere into a 5 km deep ocean. The impactors were composed of mantle material (3.32 g/cc or iron (7.8 g/cc with diameters from 250m to 10 km. In our three-dimensional runs we simulated asteroids of 1 km diameter composed of iron moving at 20 km/s at angles of 45 and 60 degrees from the vertical. All impacts, including the oblique ones, produce a large underwater cavities with nearly vertical walls followed by a collapse starting from the bottom and subsequent vertical jetting. Substantial amounts of water are vaporized and lofted high into the atmosphere. In the larger impacts, significant amounts of crustal and even mantle material are lofted as well. Tsunamis up to a kilometer in initial height are generated by the collapse of the vertical jet. These waves are initially complex in form, and interact strongly with shocks propagating through the water and the crust. The tsunami waves are followed out to 100 km from the point of impact. Their periods and wavelengths show them to be intermediate type waves, and not (in general shallow-water waves. At great distances, the waves decay as the inverse of the distance from the impact point, ignoring sea-floor topography. For all impactors smaller than about 2 km diameter, the impacting body is highly fragmented and its remains lofted into the stratosphere with the water
Three dimensional simulations of viscous folding in diverging microchannels
Xu, Bingrui; Shin, Seungwon; Juric, Damir
2016-01-01
Three dimensional simulations on the viscous folding in diverging microchannels reported by Cubaud and Mason are performed using the parallel code BLUE for multi-phase flows. The more viscous liquid L_1 is injected into the channel from the center inlet, and the less viscous liquid L_2 from two side inlets. Liquid L_1 takes the form of a thin filament due to hydrodynamic focusing in the long channel that leads to the diverging region. The thread then becomes unstable to a folding instability, due to the longitudinal compressive stress applied to it by the diverging flow of liquid L_2. Given the long computation time, we were limited to a parameter study comprising five simulations in which the flow rate ratio, the viscosity ratio, the Reynolds number, and the shape of the channel were varied relative to a reference model. In our simulations, the cross section of the thread produced by focusing is elliptical rather than circular. The initial folding axis can be either parallel or perpendicular to the narrow di...
Flux canceling in three-dimensional radiative magnetohydrodynamic simulations
Thaler, Irina; Spruit, H. C.
2017-05-01
We aim to study the processes involved in the disappearance of magnetic flux between regions of opposite polarity on the solar surface using realistic three-dimensional (3D) magnetohydrodynamic (MHD) simulations. "Retraction" below the surface driven by magnetic forces is found to be a very effective mechanism of flux canceling of opposite polarities. The speed at which flux disappears increases strongly with initial mean flux density. In agreement with existing inferences from observations we suggest that this is a key process of flux disappearance within active complexes. Intrinsic kG strength concentrations connect the surface to deeper layers by magnetic forces, and therefore the influence of deeper layers on the flux canceling process is studied. We do this by comparing simulations extending to different depths. For average flux densities of 50 G, and on length scales on the order of 3 Mm in the horizontal and 10 Mm in depth, deeper layers appear to have only a mild influence on the effective rate of diffusion.
Three dimensional simulations of viscous folding in diverging microchannels
Xu, Bingrui; Chergui, Jalel; Shin, Seungwon; Juric, Damir
2016-11-01
Three dimensional simulations on the viscous folding in diverging microchannels reported by Cubaud and Mason are performed using the parallel code BLUE for multi-phase flows. The more viscous liquid L1 is injected into the channel from the center inlet, and the less viscous liquid L2 from two side inlets. Liquid L1 takes the form of a thin filament due to hydrodynamic focusing in the long channel that leads to the diverging region. The thread then becomes unstable to a folding instability, due to the longitudinal compressive stress applied to it by the diverging flow of liquid L2. We performed a parameter study in which the flow rate ratio, the viscosity ratio, the Reynolds number, and the shape of the channel were varied relative to a reference model. In our simulations, the cross section of the thread produced by focusing is elliptical rather than circular. The initial folding axis can be either parallel or perpendicular to the narrow dimension of the chamber. In the former case, the folding slowly transforms via twisting to perpendicular folding, or it may remain parallel. The direction of folding onset is determined by the velocity profile and the elliptical shape of the thread cross section in the channel that feeds the diverging part of the cell.
Three-dimensional hydrodynamic simulations of L2 Puppis
Chen, Zhuo; Frank, Adam; Blackman, Eric G
2016-01-01
Recent observations of the L2 Puppis system suggest that the Mira-like variable may be in the early stages of forming a bipolar planetary nebula (PN). As one of nearest and brightest AGB stars, and due to its status as a binary, L2 Puppis serves as a benchmark object for studying the late-stages of stellar evolution. We perform global, three-dimensional, adaptive-mesh-refinement hydrodynamic simulations of the L2 Puppis system with AstroBEAR. The broad-band spectral-energy-distribution (SED) and synthetic observational images are post-processed from our simulations using the radiative transfer code RADMC-3D. Given the reported binary parameters, we are able to reproduce the current observational data if a short pulse of dense material is released from the AGB star with a velocity sufficient to escape the primary but not the binary. Such a situation could emanate from a thermal pulse, be induced by a periastron passage of the secondary, or could be launched if the primary ingests a planet.
Three-dimensional hydrodynamic simulations of OMEGA implosions
Igumenshchev, I. V.; Michel, D. T.; Shah, R. C.; Campbell, E. M.; Epstein, R.; Forrest, C. J.; Glebov, V. Yu.; Goncharov, V. N.; Knauer, J. P.; Marshall, F. J.; McCrory, R. L.; Regan, S. P.; Sangster, T. C.; Stoeckl, C.; Schmitt, A. J.; Obenschain, S.
2017-05-01
The effects of large-scale (with Legendre modes ≲ 10) asymmetries in OMEGA direct-drive implosions caused by laser illumination nonuniformities (beam-power imbalance and beam mispointing and mistiming), target offset, and variation in target-layer thickness were investigated using the low-noise, three-dimensional Eulerian hydrodynamic code ASTER. Simulations indicate that these asymmetries can significantly degrade the implosion performance. The most important sources of the asymmetries are the target offsets ( ˜10 to 20 μm), beam-power imbalance ( σrms˜10 %), and variations ( ˜5 %) in target-layer thickness. Large-scale asymmetries distort implosion cores, resulting in a reduced hot-spot confinement and an increased residual kinetic energy of implosion targets. The ion temperature inferred from the width of simulated neutron spectra is influenced by bulk fuel motion in the distorted hot spot and can result in up to an ˜1 -keV increase in apparent temperature. Similar temperature variations along different lines of sight are observed. Demonstrating hydrodynamic equivalence to ignition designs on OMEGA requires a reduction in large-scale target and laser-imposed nonuniformities, minimizing target offset, and employing highly efficient mid-adiabat (α = 4) implosion designs, which mitigate cross-beam energy transfer and suppress short-wavelength Rayleigh-Taylor growth.
Institute of Scientific and Technical Information of China (English)
马传奇; 程党国; 陈丰秋; 詹晓力
2013-01-01
采用FLUENT对2 MW和5 MW等离子体裂解煤反应器内气固混合行为进行了三维数值模拟.结果表明,2 MW反应器内的煤粉颗粒能够射入气流中心,气固两相混合均匀,而5 MW反应器内的煤粉颗粒不能穿透射流,主要集中在壁面附近,反应器放大效应明显,所得模拟结果与热态试验结果吻合较好.进而应用此模型对不同粒径和入射速度进行了模拟计算,结果表明适当地增大粒径和颗粒入射速度都有利于提高气固两相的混合效率.%Three-dimensional simulations of gas-solid mixing behavior in thermal plasma reactor for coal pyrolysis with power of 2 MW and 5 MW are performed.The results show that in the 2 MW plasma reactor,coal particles can penetrate through the gas to the center of the reactor,and the two phases mixed well.While in the 5 MW plasma reactor coal particles fails to penetrate the gas,most of which concentrate on the wall.The evident scale-up effect can be observed.The simulation results agree well with experimental values.The simulations with different particle diameters and feeding rates are further carried out.It shows that appropriate increase in particle diameter and feeding rate can strengthen the contact of the two phrases.
Fan-shaped jets in three dimensional reconnection simulation as a model of ubiquitous solar jets
Jiang, Rong Lin; Isobe, Hiroaki; Fang, Cheng
2010-01-01
Magnetic reconnection is a fundamental process in space and astrophysical plasmas in which oppositely directed magnetic fields changes its connectivity and eventually converts its energy into kinetic and thermal energy of the plasma. Recently, ubiquitous jets (for example, chromospheric anemone jets, penumbral microjets, umbral light bridge jets) have been observed by Solar Optical Telescope on board the satellite Hinode. These tiny and frequently occurring jets are considered to be a possible evidence of small-scale ubiquitous reconnection in the solar atmosphere. However, the details of three dimensional magnetic configuration are still not very clear. Here we propose a new model based on three dimensional simulations of magnetic reconnection using a typical current sheet magnetic configuration with a strong guide field. The most interesting feature is that the jets produced by the reconnection eventually move along the guide field lines. This model provides a fresh understanding of newly discovered ubiquit...
Three-dimensional numerical simulations of three-phase flows
Pavlidis, Dimitrios; Xie, Zhizhua; Salinas, Pablo; Pain, Chris; Matar, Omar
2015-11-01
The objective of this study is to investigate the fluid dynamics of three-dimensional three-phase flow problems, such as droplet impact on a gas-liquid interface and bubble rising through a liquid-liquid interface. An adaptive unstructured mesh modelling framework is employed here to study three-phase flow problems, which can modify and adapt unstructured meshes to better represent the underlying physics of multiphase problems and reduce computational effort without sacrificing accuracy. The numerical framework consists of a mixed control volume and finite element formulation, a `volume of fluid' type method for the interface capturing based on a compressive control volume advection method and second-order finite element methods, and a force-balanced algorithm for the surface tension implementation, minimising the spurious velocities often found in such flow simulations. The surface tension coefficient decomposition method has been employed to deal with surface tension pairing between different phases via a compositional approach. Numerical examples of some benchmark tests and the dynamics of three-phase flows are presented to demonstrate the ability of this method. EPSRC Programme Grant, MEMPHIS, EP/K0039761/1.
Three-Dimensional PIC-MC Modeling for Relativistic Electron Beam Transport Through Dense Plasma
Institute of Scientific and Technical Information of China (English)
CAO Lihua; CHANG Tieqiang; PEI Wenbing; LIU Zhanjun; LI Meng; ZHENG Chunyang
2008-01-01
We have developed a three dimensional (3D) PIC (particle-in-cell)-MC (Monte Carlo) code in order to simulate an electron beam transported into the dense matter based on our previous two dimensional code. The relativistic motion of fast electrons is treated by the particle-in-cell method under the influence of both a self-generated transverse magnetic field and an axial electric field, as well as collisions. The electric field generated by return current is ex-pressed by Ohm's law and the magnetic field is calculated from Faraday's law. The slowing down of monoenergy electrons in DT plasma is calculated and discussed.
Dissipation via Landau Damping in Two- and Three-Dimensional Plasma Turbulence
Li, Tak Chu; Klein, Kristopher G; TenBarge, Jason M
2015-01-01
Plasma turbulence is ubiquitous in space and astrophysical plasmas, playing an important role in plasma energization, but the physical mechanisms that lead to dissipation of the turbulent energy remain to be definitively identified. This work addresses the fundamental physics of turbulent dissipation by examining the velocity-space structure that develops as a result of the collisionless interaction between the turbulent electromagnetic fluctuations and the particles in a low beta plasma. Both two- and three-dimensional (2D and 3D) nonlinear gyrokinetic simulations show an electron velocity-space signature qualitatively similar to that of the linear Landau damping of Alfv\\'en waves in a 3D linear simulation. This evidence strongly suggests that the turbulent energy is transferred by Landau damping to electrons in low beta plasmas in both 2D and 3D, making possible the ultimate irreversible heating of the plasma. Although, in the 2D case with no variation along the equilibrium magnetic field, it may be expecte...
Three-dimensional, computer simulated navigation in endoscopic neurosurgery
Directory of Open Access Journals (Sweden)
Roberta K. Sefcik, BHA
2017-06-01
Conclusion: Three-dimensional, frameless neuronavigation systems are useful in endoscopic neurosurgery to assist in the pre-operative planning of potential trajectories and to help localize the pathology of interest. Neuronavigation appears to be accurate to <1–2 mm without issues related to brain shift. Further work is necessary in the investigation of the effect of neuronavigation on operative time, cost, and patient-centered outcomes.
Three dimensional Monte Carlo simulations of ionized nebulae
Ercolano, Barbara
2002-12-01
The study of photoionized environments is fundamental to many astrophysical problems. Up to the present most photoionization codes have numerically solved the equations of radiative transfer by making the extreme simplifying assumption of spherical symmetry. Unfortunately very few real astronomical nebulae satisfy this requirement. To remedy these shortcomings, a self-consistent, three-dimensional radiative transfer code has been developed using Monte Carlo techniques. The code, Mocassin, is designed to build realistic models of photoionized nebulae having arbitrary geometries and density distributions with both the stellar and diffuse radiation fields treated self-consistently. In addition, the code is capable of treating one or more exciting stars located at non-central locations. The gaseous region is approximated by a cuboidal Cartesian grid composed of numerous cells. The physical conditions within each grid cell are determined by solving the thermal equilibrium and ionization balance equations. This requires a knowledge of the local primary and secondary radiation fields, which are calculated self-consistently by locally simulating the individual processes of ionization and recombination. The main structure and computational methods used in the Mocassin code are described in this thesis. Mocassin has been benchmarked against established one-dimensional spherically symmetric codes for a number of standard cases, as defined by the Lexington/Meudon photoionization workshops (Pequignot, 1986; Ferland et al., 1995; Pequignot et al., 2001). The results obtained for the benchmark cases are satisfactory and are presented in this work. A performance analysis has also been carried out and is discussed here. The code has been applied to construct a realistic model of the planetary nebula NGC 3918. Three different geometric models were tried, the first being the biconical density distribution already used by Clegg et al. (1987). In this model the nebula is approximated
The dust acoustic waves in three dimensional scalable complex plasma
Zhukhovitskii, D I
2015-01-01
Dust acoustic waves in the bulk of a dust cloud in complex plasma of low pressure gas discharge under microgravity conditions are considered. The dust component of complex plasma is assumed a scalable system that conforms to the ionization equation of state (IEOS) developed in our previous study. We find singular points of this IEOS that determine the behavior of the sound velocity in different regions of the cloud. The fluid approach is utilized to deduce the wave equation that includes the neutral drag term. It is shown that the sound velocity is fully defined by the particle compressibility, which is calculated on the basis of the scalable IEOS. The sound velocities and damping rates calculated for different 3D complex plasmas both in ac and dc discharges demonstrate a good correlation with experimental data that are within the limits of validity of the theory. The theory provides interpretation for the observed independence of the sound velocity on the coordinate and for a weak dependence on the particle ...
Energy Dissipation and Landau Damping in Two- and Three-dimensional Plasma Turbulence
Li, Tak Chu; Howes, Gregory G.; Klein, Kristopher G.; TenBarge, Jason M.
2016-12-01
Plasma turbulence is ubiquitous in space and astrophysical plasmas, playing an important role in plasma energization, but the physical mechanisms leading to dissipation of the turbulent energy remain to be definitively identified. Kinetic simulations in two dimensions (2D) have been extensively used to study the dissipation process. How the limitation to 2D affects energy dissipation remains unclear. This work provides a model of comparison between two- and three-dimensional (3D) plasma turbulence using gyrokinetic simulations; it also explores the dynamics of distribution functions during the dissipation process. It is found that both 2D and 3D nonlinear gyrokinetic simulations of a low-beta plasma generate electron velocity-space structures with the same characteristics as that of the linear Landau damping of Alfvén waves in a 3D linear simulation. The continual occurrence of the velocity-space structures throughout the turbulence simulations suggests that the action of Landau damping may be responsible for the turbulent energy transfer to electrons in both 2D and 3D, and makes possible the subsequent irreversible heating of the plasma through collisional smoothing of the velocity-space fluctuations. Although, in the 2D case where variation along the equilibrium magnetic field is absent, it may be expected that Landau damping is not possible, a common trigonometric factor appears in the 2D resonant denominator, leaving the resonance condition unchanged from the 3D case. The evolution of the 2D and 3D cases is qualitatively similar. However, quantitatively, the nonlinear energy cascade and subsequent dissipation is significantly slower in the 2D case.
Three-dimensional model and simulation of vacuum arcs under axial magnetic fields
Wang, Lijun; Jia, Shenli; Zhou, Xin; Wang, Haijing; Shi, Zongqian
2012-01-01
In this paper, a three-dimensional (3d) magneto-hydro-dynamic (MHD) model of axial magnetic field vacuum arcs (AMFVAs) is established. Based on this model, AMFVAs are simulated and analyzed. Three-dimensional spatial distributions of many important plasma parameters and electric characteristics in AMFVAs can be obtained, such as ion number density, ion temperature, electron temperature, plasma pressure, current densities along different directions (x, y, and z), ion velocities along different directions, electric fields strength along different directions, and so on. Simulation results show that there exist significant spiral-shaped rotational phenomena in the AMFVAs, this kind of rotational phenomenon also can be verified by the many related experiments (AMFVAs photographs, especially for stronger AMF strength). For current simulation results of AMFVAs, the maximal rotational velocity at anode side is about 1100 m/s. Radial electric field is increased from arc center to arc edge; axial electric field is decreased from cathode side to anode side. Radial electric field at arc edge can be larger than axial electric field. Azimuthal electric field in most regions is much smaller than radial and axial electric field, but it can reach about 1.19 kV/m. Radial magnetic field is the smallest one compared with other components, it reaches to maximum value at the position near to anode, it can influence arc characteristics.
Three dimensional simulation for bayou choctaw strategic petroleum reserve (SPR).
Energy Technology Data Exchange (ETDEWEB)
Ehgartner, Brian L. (Sandia National Laboratories, Albuquerque, NM); Park, Byoung Yoon; Lee, Moo Yul
2006-12-01
Three dimensional finite element analyses were performed to evaluate the structural integrity of the caverns located at the Bayou Choctaw (BC) site which is considered a candidate for expansion. Fifteen active and nine abandoned caverns exist at BC, with a total cavern volume of some 164 MMB. A 3D model allowing control of each cavern individually was constructed because the location and depth of caverns and the date of excavation are irregular. The total cavern volume has practical interest, as this void space affects total creep closure in the BC salt mass. Operations including both cavern workover, where wellhead pressures are temporarily reduced to atmospheric, and cavern enlargement due to leaching during oil drawdowns that use water to displace the oil from the caverns, were modeled to account for as many as the five future oil drawdowns in the six SPR caverns. The impacts on cavern stability, underground creep closure, surface subsidence, infrastructure, and well integrity were quantified.
Three-dimensional dynamics of collisionless magnetic reconnection in large-scale pair plasmas.
Yin, L; Daughton, W; Karimabadi, H; Albright, B J; Bowers, Kevin J; Margulies, J
2008-09-19
Using the largest three-dimensional particle-in-cell simulations to date, collisionless magnetic reconnection in large-scale electron-positron plasmas without a guide field is shown to involve complex interaction of tearing and kink modes. The reconnection onset is patchy and occurs at multiple sites which self-organize to form a single, large diffusion region. The diffusion region tends to elongate in the outflow direction and become unstable to secondary kinking and formation of "plasmoid-rope" structures with finite extent in the current direction. The secondary kink folds the reconnection current layer, while plasmoid ropes at times follow the folding of the current layer. The interplay between these secondary instabilities plays a key role in controlling the time-dependent reconnection rate in large-scale systems.
Exact scaling laws for helical three-dimensional two-fluid turbulent plasmas
Andrés, Nahuel; Sahraoui, Fouad
2016-01-01
We derive exact scaling laws for a three-dimensional incompressible helical two-fluid plasma, without the assumption of isotropy. For each ideal invariant of the two-fluid model, i.e. the total energy, the electron helicity and the proton helicity, we derive simple scaling laws in terms of two-point increments correlation functions expressed in terms of the velocity field of each species and the magnetic field. These variables are appropriate for comparison with \\textit{in-situ} measurements in the solar wind at different spatial ranges and data from numerical simulations. Finally, with the exact scaling laws and dimensional analysis we predict the magnetic energy and electron helicity spectra for different ranges of scales.
Parallel direct numerical simulation of three-dimensional spray formation
Chergui, Jalel; Juric, Damir; Shin, Seungwon; Kahouadji, Lyes; Matar, Omar
2015-11-01
We present numerical results for the breakup mechanism of a liquid jet surrounded by a fast coaxial flow of air with density ratio (water/air) ~ 1000 and kinematic viscosity ratio ~ 60. We use code BLUE, a three-dimensional, two-phase, high performance, parallel numerical code based on a hybrid Front-Tracking/Level Set algorithm for Lagrangian tracking of arbitrarily deformable phase interfaces and a precise treatment of surface tension forces. The parallelization of the code is based on the technique of domain decomposition where the velocity field is solved by a parallel GMRes method for the viscous terms and the pressure by a parallel multigrid/GMRes method. Communication is handled by MPI message passing procedures. The interface method is also parallelized and defines the interface both by a discontinuous density field as well as by a triangular Lagrangian mesh and allows the interface to undergo large deformations including the rupture and/or coalescence of interfaces. EPSRC Programme Grant, MEMPHIS, EP/K0039761/1.
Kinetic simulations of magnetic reconnection in three-dimensional null-points.
Olshevsky, Vyacheslav; Lapenta, Giovanni; Divin, Andrey; Markidis, Stefano
2015-04-01
We report kinetic particle-in-cell simulations of an essentially three-dimensional magnetized plasma configuration. Initially the evolution is governed by large-scale fluid modes excited by the pressure imbalance. At this phase current channels (pinches) are created along the sequences of spiral null-points. After ten ion gyroperiods the relaxation is over, and about half of magnetic energy is converted to ion currents, particle heating, and generation of suprathermal particles. At the next phase the evolution is dominated by volumetric magnetic reconnection, mainly associated with spiral null-points (pinches); non-spiral nulls don't play important role in the energy release. Such reconection is a possible mechanism of magnetic energy dissipation in turbulent space plasmas where currents and twisted field lines are ubiquitous.
Three-Dimensional Modeling of Laser-Plasma Interactions Near the Quarter-Critical Density in Plasmas
Wen, H.; Maximov, A. V.; Yan, R.; Ren, C.; Li, J.; Myatt, J. F.
2015-11-01
Three dimensional particle-in-cell simulations have been performed in the plasma region near quarter-critical density for the parameters typical for direct-drive inertial confinement fusion experiments. The laser-plasma instabilities of two-plasmon decay (TPD), stimulated Raman scattering (SRS), and stimulated Brillouin scattering have been identified in the time evolution of different electric- and magnetic-field components. A good agreement between the simulation results and the theories of TPD and SRS has been observed. In the nonlinear saturation regime, the field intensities and the fast-electron distributions are compared for plane-wave and speckled laser beams. The effects of collisions are studied. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.
Three-dimensional direct particle simulation on the Connection Machine
Dagum, Leonardo
1991-01-01
This paper presents the algorithms necessary for an efficient data parallel implementation of a 3D particle simulation. In particular, a general master/slave algorithm and a fast sorting algorithm are described and the use of these algorithms in a particle simulation is outlined. A particle simulation using these algorithms has been implemented on a 32768 processor Connection Machine that is capable of simulating over 30 million particles at an average rate of 2.4-microsec/particle/step. Results are presented from the simulation of flow over an Aeroassisted Flight Experiment geometry at 100 km altitude.
Validation of three-dimensional micro injection molding simulation accuracy
DEFF Research Database (Denmark)
Tosello, Guido; Costa, F.S.; Hansen, Hans Nørgaard
2011-01-01
length, injection pressure profile, molding mass and flow pattern. The importance of calibrated micro molding process monitoring for an accurate implementation strategy of the simulation and its validation has been demonstrated. In fact, inconsistencies and uncertainties in the experimental data must...... be minimized to avoid introducing uncertainties in the simulation calculations. Simulations of bulky sub-100 milligrams micro molded parts have been validated and a methodology for accurate micro molding simulations was established.......Data analysis and simulations on micro-molding experiments have been conducted. Micro molding simulations have been executed taking into account actual processing conditions implementation in the software. Various aspects of the simulation set-up have been considered in order to improve...
Fast magnetic twister and plasma perturbations in a three-dimensional coronal arcade
Energy Technology Data Exchange (ETDEWEB)
Murawski, K. [Group of Astrophysics, UMCS, ul. Radziszewskiego 10, 20-031 Lublin (Poland); Srivastava, A. K. [Department of Physics, Indian Institute of Technology (Banaras Hindu University), Varanasi-221005 (India); Musielak, Z. E., E-mail: kmur@kft.umcs.lublin.pl, E-mail: asrivastava.app@iitbhu.ac.in, E-mail: zmusielak@uta.edu, E-mail: musielak@kis.uni-freiburg.de [Department of Physics, University of Texas at Arlington, Arlington, TX 76019 (United States)
2014-06-10
We present results of three-dimensional (3D) numerical simulations of a fast magnetic twister excited above a foot-point of the potential solar coronal arcade that is embedded in the solar atmosphere with the initial VAL-IIIC temperature profile, which is smoothly extended into the solar corona. With the use of the FLASH code, we solve 3D ideal magnetohydrodynamic equations by specifying a twist in the azimuthal component of magnetic field in the solar chromosphere. The imposed perturbation generates torsional Alfvén waves as well as plasma swirls that reach the other foot-point of the arcade and partially reflect back from the transition region. The two vortex channels are evident in the generated twisted flux-tube with a fragmentation near its apex which results from the initial twist as well as from the morphology of the tube. The numerical results are compared to observational data of plasma motions in a solar prominence. The comparison shows that the numerical results and the data qualitatively agree even though the observed plasma motions occur over comparatively large spatio-temporal scales in the prominence.
Zaliznyak, Yu A; Goedbloed, J P; Zaliznyak, Yu.
2003-01-01
We present a numerical study of an idealized magnetohydrodynamic (MHD) configuration consisting of a planar wake flow embedded into a three-dimensional (3D) sheared magnetic field. Our simulations investigate the possibility for in-situ development of large-scale compressive disturbances at cospatial current sheet -- velocity shear regions in the heliosphere. Using a linear MHD solver, we first systematically chart the destabilized wavenumbers, corresponding growth rates, and physical parameter ranges for dominant 3D sinuous-type instabilities in an equilibrium wake--current sheet system. Wakes bounded by sufficiently supersonic (Mach number $M_s > 2.6$) flow streams are found to support dominant fully 3D sinuous instabilities when the plasma beta is of order unity. Fully nonlinear, compressible 2.5D and 3D MHD simulations show the self-consistent formation of shock fronts of fast magnetosonic type. They carry density perturbations far away from the wake's center. Shock formation conditions are identified in ...
X-ray generation mechanisms in three-dimensional simulations of wire array Z-pinches
Chittenden, J. P.; Lebedev, S. V.; Jennings, C. A.; Bland, S. N.; Ciardi, A.
2004-12-01
Resistive magneto-hydrodynamic (MHD) simulations are used to evaluate the influence of three-dimensional inhomogeneities on x-ray power production in wire array Z-pinches. In particular, we concentrate on simulations of wire array Z-pinch experiments on the MAGPIE generator at Imperial College. An initial temperature perturbation is used to stimulate variations in wire core ablation rates that result in a highly non-uniform final implosion. Results indicate that x-ray power production is governed by the symmetry of the implosion surface and by the rate at which current can transfer to the axis through a three-dimensional debris field that trails behind the main implosion. The peak power is ultimately limited by the growth of MHD instabilities in the stagnated pinch. The individual contributions of the implosion kinetic energy, compression of the stagnated pinch, ohmic heating and MHD instabilities to the radiation yield are quantified. The onset of m = 1 instabilities is found to provide an efficient mechanism for dissipation of the magnetic energy surrounding the stagnated pinch. The formation of a helical plasma column not only allows the magnetic field to do work in driving an expansion of the helix but also enhances the ohmic heating by elongating the path of the current through the pinch. The effect of these energy sources combined is to increase the radiation yield to typically 3½ times the kinetic energy of the implosion. Simulations of arrays with different wire numbers, wire material and with nested arrays are used to examine the mechanisms that influence the peak soft x-ray power. In the simulations, peak power can be increased by: increasing the number of wires (which improves the implosion symmetry), by increasing the atomic number of the material (which increases the compressibility of the plasma) and by using a nested inner array (which brings the mass and the current to the axis more efficiently than a single array).
Three Dimensional Computer Graphics Federates for the 2012 Smackdown Simulation
Fordyce, Crystal; Govindaiah, Swetha; Muratet, Sean; O'Neil, Daniel A.; Schricker, Bradley C.
2012-01-01
The Simulation Interoperability Standards Organization (SISO) Smackdown is a two-year old annual event held at the 2012 Spring Simulation Interoperability Workshop (SIW). A primary objective of the Smackdown event is to provide college students with hands-on experience in developing distributed simulations using High Level Architecture (HLA). Participating for the second time, the University of Alabama in Huntsville (UAHuntsville) deployed four federates, two federates simulated a communications server and a lunar communications satellite with a radio. The other two federates generated 3D computer graphics displays for the communication satellite constellation and for the surface based lunar resupply mission. Using the Light-Weight Java Graphics Library, the satellite display federate presented a lunar-texture mapped sphere of the moon and four Telemetry Data Relay Satellites (TDRS), which received object attributes from the lunar communications satellite federate to drive their motion. The surface mission display federate was an enhanced version of the federate developed by ForwardSim, Inc. for the 2011 Smackdown simulation. Enhancements included a dead-reckoning algorithm and a visual indication of which communication satellite was in line of sight of Hadley Rille. This paper concentrates on these two federates by describing the functions, algorithms, HLA object attributes received from other federates, development experiences and recommendations for future, participating Smackdown teams.
Three-Dimensional Electro-Thermal Verilog-A Model of Power MOSFET for Circuit Simulation
Chvála, A.; Donoval, D.; Marek, J.; Príbytný, P.; Molnár, M.; Mikolášek, M.
2014-04-01
New original circuit model for the power device based on interactive coupling of electrical and thermal properties is described. The thermal equivalent network for a three-dimensional heat flow is presented. Designed electro-thermal MOSFET model for circuit simulations with distributed properties and three-dimensional thermal equivalent network is used for simulation of multipulse unclamped inductive switching (UIS) test of device robustness. The features and the limitations of the new model are analyzed and presented.
Li He Ping; Chen, X
2003-01-01
In this paper, physical/mathematical models for the three-dimensional, quasi-steady modelling of the plasma flow and heat transfer inside a non-transferred DC arc plasma torch are described in detail. The Steenbeck's minimum principle (Finkelnburg W and Maecker H 1956 Electric arcs and thermal plasmas Encyclopedia of Physics vol XXII (Berlin: Springer)) is employed to determine the axial position of the anode arc-root at the anode surface. This principle postulates a minimum arc voltage for a given arc current, working gas flow rate, and torch configuration. The modelling results show that the temperature and flow fields inside the DC non-transferred arc plasma torch show significant three-dimensional features. The predicted anode arc-root attachment position and the arc shape by employing Steenbeck's minimum principle are reasonably consistent with experimental observations. The thermal efficiency and the torch power distribution are also calculated in this paper. The results show that the thermal efficiency...
Three-dimensional Microstructure Simulation Model of Cement Based Materials,
Ye, G.; Van Breugel, K.
2003-01-01
This paper describes a computer-based numerical model for the simulation of the development of microstructure during cement hydration. Special emphasis is on the algorithm for characterizing the pores. This includes the porosity and the pore size distribution and the topological properties of the po
Understanding Accretion Disks through Three Dimensional Radiation MHD Simulations
Jiang, Yan-Fei
I study the structures and thermal properties of black hole accretion disks in the radiation pressure dominated regime. Angular momentum transfer in the disk is provided by the turbulence generated by the magneto-rotational instability (MRI), which is calculated self-consistently with a recently developed 3D radiation magneto-hydrodynamics (MHD) code based on Athena. This code, developed by my collaborators and myself, couples both the radiation momentum and energy source terms with the ideal MHD equations by modifying the standard Godunov method to handle the stiff radiation source terms. We solve the two momentum equations of the radiation transfer equations with a variable Eddington tensor (VET), which is calculated with a time independent short characteristic module. This code is well tested and accurate in both optically thin and optically thick regimes. It is also accurate for both radiation pressure and gas pressure dominated flows. With this code, I find that when photon viscosity becomes significant, the ratio between Maxwell stress and Reynolds stress from the MRI turbulence can increase significantly with radiation pressure. The thermal instability of the radiation pressure dominated disk is then studied with vertically stratified shearing box simulations. Unlike the previous results claiming that the radiation pressure dominated disk with MRI turbulence can reach a steady state without showing any unstable behavior, I find that the radiation pressure dominated disks always either collapse or expand until we have to stop the simulations. During the thermal runaway, the heating and cooling rates from the simulations are consistent with the general criterion of thermal instability. However, details of the thermal runaway are different from the predictions of the standard alpha disk model, as many assumptions in that model are not satisfied in the simulations. We also identify the key reasons why previous simulations do not find the instability. The thermal
Three-dimensional MHD simulation for the solar wind structure observed by Ulysses
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
Ulysses has been the first spacecraft to explore the high latitudinal regions of the heliosphere till now. During its first rapid pole-to-pole transit from September 1994to June 1995, Ulysses observed a fast speed flow with magnitude reaching 700-800 km/s at high latitudinal region except + 20° area near the ecliptic plane where the velocity is 300-400 km/s. The observations also showed a sudden jump of the velocity across the two regions. In this note,based on the characteristic and representative observations of the solar magnetic field and K-coronal polarized brightness, the large-scale solar wind structure mentioned above is reproduced by using a three-dimensional MHD model. The numerical results are basically consistent with those of Ulysses observations. Our results also show that the distributions of magnetic field and plasma number density on the solar source surface play an important role in governing this structure. Furthermore, the three-dimensional MHD model used here has a robust ability to simulate this kind of large-scale wind structure.
Comparison of two- and three-dimensional simulations of miscible Rayleigh-Taylor instability
Energy Technology Data Exchange (ETDEWEB)
Cabot, W
2006-02-23
A comparison of two-dimensional and three-dimensional high-resolution numerical large-eddy simulations of planar, miscible Rayleigh-Taylor instability flows are presented. The resolution of the three-dimensional simulation is sufficient to attain a fully turbulent state. A number of different statistics from the mixing region (e.g., growth rates, PDFs, mixedness measures, and spectra) are used to demonstrate that two-dimensional flow simulations differ substantially from the three-dimensional one. It is found that the two-dimensional flow grows more quickly than its three-dimensional counterpart at late times, develops larger structures, and is much less well mixed. These findings are consistent with the concept of inverse cascade in two-dimensional flow, as well as the influence of a reduced effective Atwood number on miscible flow.
Three-Dimensional Magnetohydrodynamic Simulations of the Crab Nebula
Porth, Oliver; Keppens, Rony
2013-01-01
In this paper we give a detailed account of the first 3D relativistic magnetohydrodynamic (MHD) simulations of Pulsar Wind Nebulae (PWN), with parameters most suitable for the Crab Nebula. In order to clarify the new features specific to 3D models, reference 2D simulations have been carried out as well. Compared to the previous 2D simulations, we considered pulsar winds with much stronger magnetisation, up to \\sigma=3, and accounted more accurately for the anticipated magnetic dissipation in the striped zone of these winds. While the 3D models preserve the separation of the post termination shock flow into the equatorial and polar components, their relative strength and significance differ. Whereas the highly magnetised 2D models produce highly coherent and well collimated polar jets capable of efficient "drilling" through the supernova shell, in the corresponding 3D models the jets are disrupted by the kink mode current driven instability and "dissolve" into the main body of PWN after propagation of several ...
Energy Technology Data Exchange (ETDEWEB)
Chang, Ouliang [Oracle Corporation, Redwood Shores, CA (United States); Gary, S. Peter [Space Science Institute, Boulder, CO (United States); Wang, Joseph, E-mail: ouliang@usc.edu, E-mail: pgary@lanl.gov, E-mail: josephjw@usc.edu [University of Southern California, Los Angeles, CA (United States)
2015-02-20
We present the results of the first fully three-dimensional particle-in-cell simulations of decaying whistler turbulence in a magnetized, homogeneous, collisionless plasma in which both forward cascades to shorter wavelengths, and inverse cascades to longer wavelengths are allowed to proceed. For the electron beta β {sub e} = 0.10 initial value considered here, the early-time rate of inverse cascade is very much smaller than the rate of forward cascade, so that at late times the fluctuation energy in the regime of the inverse cascade is much weaker than that in the forward cascade regime. Similarly, the wavevector anisotropy in the inverse cascade regime is much weaker than that in the forward cascade regime.
Three-dimensional nanoelectronic device simulation using spectral element methods
Cheng, Candong
The purpose of this thesis is to develop an efficient 3-Dimensional (3-D) nanoelectronic device simulator. Specifically, the self-consistent Schrodinger-Poisson model was implemented in this simulator to simulate band structures and quantum transport properties. Also, an efficient fast algorithm, spectral element method (SEM), was used in this simulator to achieve spectral accuracy where the error decreases exponentially with the increase of sampling densities and the basis order of the polynomial functions, thus significantly reducing the CPU time and memory usage. Moreover, within this simulator, a perfectly matched layer (PML) boundary condition method was used for the Schrodinger solver, which significantly simplifies the problem and reduces the computational time. Furthermore, the effective mass in semiconductor devices was treated as a full anisotropic mass tensor, which provides an excellent tool to study the anisotropy characteristics along arbitrary orientation of the device. Nanoelectronic devices usually involve the simulations of energy band and quantum transport properties. One of the models to perform these simulations is by solving a self-consistent Schrodinger-Poisson system. Two efficient fast algorithms, spectral grid method (SGM) and SEM, are investigated and implemented in this thesis. The spectral accuracy is achieved in both algorithms, whose errors decrease exponentially with the increase of the sampling density and basis orders. The spectral grid method is a pseudospectral method to achieve a high-accuracy result by choosing special nonuniform grid set and high-order Lagrange interpolants for a partial differential equation. Spectral element method is a high-order finite element method which uses the Gauss-Lobatto-Legendre (GLL) polynomials to represent the field variables in the Schrodinger-Poisson system and, therefore, to achieve spectral accuracy. We have implemented the SGM in the Schrodinger equation to solve the energy band structures
Null Points in Three-Dimensional Kinetic Simulations of Magnetic Reconnection
Deca, J.; Olshevsky, V.; Divin, A. V.; Innocenti, M. E.; Cazzola, E.; Peng, B.; Markidis, S.; Ormvråk, M.; Lapenta, G.
2015-12-01
Kinetic particle-in-cell simulations are the primary tool for studying magnetic reconnection in space plasmas. Magnetic null points are believed to be the preferred locations in space where magnetic reconnection is luckily to happen, and are in the focus of interest of space missions such as Cluster and MMS. Simulations of magnetic reconnection in various configurations performed with the implicit particle-in-cell code iPic3D revealed that nulls are ubiquitious in these models. We apply the Poincare index technique to locate and identify the topological characteristics of the magnetic null points in different three-dimensional simulations. We investigate the relevance of magnetic nulls to energy dissipation, turbulence and plasma instabilities. In particular, we found out that magnetic nulls of spiral type associated with magnetic islands and flux ropes play more important role in the energy release than the radial nulls. This finding is in accordance with some recent MHD simulations and in situ observations of Cluster spacecraft.
Magnetic field evolution in magnetar crusts through three dimensional simulations
Gourgouliatos, Konstantinos N; Hollerbach, Rainer
2016-01-01
Current models of magnetars require extremely strong magnetic fields to explain their observed quiescent and bursting emission, implying that the field strength within the star's outer crust is orders of magnitude larger than the dipole component inferred from spin-down measurements. This presents a serious challenge to theories of magnetic field generation in a proto-neutron star. Here, we present detailed modelling of the evolution of the magnetic field in the crust of a neutron star through 3-D simulations. We find that, in the plausible scenario of equipartition of energy between global-scale poloidal and toroidal magnetic components, magnetic instabilities transfer energy to non-axisymmetric, kilometre-sized magnetic features, in which the local field strength can greatly exceed that of the global-scale field. These intense small-scale magnetic features can induce high energy bursts through local crust yielding, and the localised enhancement of Ohmic heating can power the star's persistent emission. Thus...
Three dimensional simulation for Big Hill Strategic Petroleum Reserve (SPR).
Energy Technology Data Exchange (ETDEWEB)
Ehgartner, Brian L. (Sandia National Laboratories, Albuquerque, NM); Park, Byoung Yoon; Sobolik, Steven Ronald (Sandia National Laboratories, Albuquerque, NM); Lee, Moo Yul (Sandia National Laboratories, Albuquerque, NM)
2005-07-01
3-D finite element analyses were performed to evaluate the structural integrity of caverns located at the Strategic Petroleum Reserve's Big Hill site. State-of-art analyses simulated the current site configuration and considered additional caverns. The addition of 5 caverns to account for a full site and a full dome containing 31 caverns were modeled. Operations including both normal and cavern workover pressures and cavern enlargement due to leaching were modeled to account for as many as 5 future oil drawdowns. Under the modeled conditions, caverns were placed very close to the edge of the salt dome. The web of salt separating the caverns and the web of salt between the caverns and edge of the salt dome were reduced due to leaching. The impacts on cavern stability, underground creep closure, surface subsidence and infrastructure, and well integrity were quantified. The analyses included recently derived damage criterion obtained from testing of Big Hill salt cores. The results show that from a structural view point, many additional caverns can be safely added to Big Hill.
Three-dimensional simulations of radionuclide transport at Yucca Mountain
Energy Technology Data Exchange (ETDEWEB)
Birdsell, K.H.; Eggert, K.G.; Travis, B.J. [Los Alamos National Lab., NM (United States)
1994-12-31
This paper presents preliminary transport calculations for radionuclide movement at Yucca Mountain. The simulations were run with TRACRN using approximately 30 000 finite-difference zones to represent the unsaturated and saturated zones underlying the potential repository in three dimensions. The results are used to study the sensitivity of radionuclide migration to uncertainties in several factors that affect transport through porous media. These factors include recharge rate, dispersivity length scale, radionuclide species, and source term. The calculations show that the transport of weakly sorbing species like {sup 99}Tc and {sup 129}I is highly sensitive to all of these factors. The transport of strongly sorbing species like {sup 135}Cs is limited by retardation and is therefore fairly insensitive to these factors. In addition to showing the sensitivity of transport to physical processes, the results show that the calculations themselves are sensitive to problem dimensionality. The calculations indicate that modeling in three dimensions provides faster breakthrough than modeling in one or two dimensions. (author) 30 figs., 2 tabs., 13 refs.
Urhahne, Detlef; Nick, Sabine; Schanze, Sascha
2009-08-01
In a series of three experimental studies, the effectiveness of three-dimensional computer simulations to aid the understanding of chemical structures and their properties was investigated. Arguments for the usefulness of three-dimensional simulations were derived from Mayer’s generative theory of multimedia learning. Simulations might lead to a decrease in cognitive load and thus support active learning. In our studies, the learning effectiveness of three-dimensional simulations was compared to two-dimensional illustrations by use of different versions of a computer programme concerning the modifications of carbon. The first and third study with freshman students of chemistry and biochemistry show that no more knowledge was acquired when participants learnt with three-dimensional simulations than with two-dimensional figures. In the second study with 16-year old secondary school students, use of simulations facilitated the acquisition of conceptual knowledge. It was concluded that three-dimensional simulations are more effective for younger students who lack the experience of learning with different visual representation formats in chemistry. In all three studies, a significant relationship between spatial ability and conceptual knowledge about the modifications of carbon was detected.
A three-dimensional cellular automaton model for simulation of dendritic growth of magnesium alloy
Institute of Scientific and Technical Information of China (English)
Mengwu WU; Shoumei XIONG
2012-01-01
A numerical model based on the cellular automaton method for the three-dimensional simulation of dendritic growth of magnesium alloy was developed.The growth kinetics was calculated from the complete solution of the transport equations.By constructing a three-dimensional anisotropy model with the cubic CA cells,simulation of dendritic growth of magnesium alloy with six-fold symmetry in the basal plane was achieved.The model was applied to simulate the equiaxed dendritic growth and columnar dendritic growth under directional solidification,and its capability was addressed by comparing the simulated results to experimental results and those in the previously published works.Meanwhile,the three-dimensional simulated results were also compared with that of in two dimensions,offering a deep insight into the microstructure formation of magnesium alloy during solidification.
Three-Dimensional Dust-Acoustic Waves in a Collisional Dusty Plasma with Opposite Polarity Particles
Institute of Scientific and Technical Information of China (English)
LIN Mai-Mai; DUAN Wen-Shan
2005-01-01
The dispersion relation is derived for three-dimensional dust-acoustic waves in a current-driven dusty plasmas with both positively and negatively charged dust particles. The dependencies of the frequency and the growth rate on the wave number K, the intensity of magnetic field B, and the inclination angle θ have been numerically shown in this paper. The growth rate is negative for the laboratory dusty plasma, but it is positive for the cosmic dusty plasma.It is found that when the inclination angle θ = π/2, there is no instability. The effect of the electrostatic field E0 has also been studied in this paper.
Liebregts, J.H.; Timmermans, M.; Koning, M.J.J. de; Berge, S.J.; Maal, T.J.J.
2015-01-01
PURPOSE: Three-dimensional (3D) virtual planning of orthognathic surgery in combination with 3D soft tissue simulation allows the surgeon and the patient to assess the 3D soft tissue simulation. This study was conducted to validate the predictability of the mass tensor model soft tissue simulation
Liebregts, J.H.; Timmermans, M.; Koning, M.J.J. de; Berge, S.J.; Maal, T.J.J.
2015-01-01
PURPOSE: Three-dimensional (3D) virtual planning of orthognathic surgery in combination with 3D soft tissue simulation allows the surgeon and the patient to assess the 3D soft tissue simulation. This study was conducted to validate the predictability of the mass tensor model soft tissue simulation a
Nonlinear electron-magnetohydrodynamic simulations of three dimensional current shear instability
Energy Technology Data Exchange (ETDEWEB)
Jain, Neeraj [Max Planck Institute for Solar System Research, Max-Planck-Str. 2, 37191 Katlenburg-Lindau (Germany); Das, Amita; Sengupta, Sudip; Kaw, Predhiman [Institute for Plasma Research, Bhat, Gandhinagar 382428 (India)
2012-09-15
This paper deals with detailed nonlinear electron-magnetohydrodynamic simulations of a three dimensional current shear driven instability in slab geometry. The simulations show the development of the instability in the current shear layer in the linear regime leading to the generation of electromagnetic turbulence in the nonlinear regime. The electromagnetic turbulence is first generated in the unstable shear layer and then spreads into the stable regions. The turbulence spectrum shows a new kind of anisotropy in which power transfer towards shorter scales occurs preferentially in the direction perpendicular to the electron flow. Results of the present three dimensional simulations of the current shear instability are compared with those of our earlier two dimensional simulations of sausage instability. It is found that the flattening of the mean velocity profile and thus reduction in the electron current due to generation of electromagnetic turbulence in the three dimensional case is more effective as compared to that in the two dimensional case.
Three-dimensional particle simulation of back-sputtered carbon in electric propulsion test facility
Zheng, Hongru; Cai, Guobiao; Liu, Lihui; Shang, Shengfei; He, Bijiao
2017-03-01
The back-sputtering deposition on thruster surface caused by ion bombardment on chamber wall material affects the performance of thrusters during the ground based electric propulsion endurance tests. In order to decrease the back-sputtering deposition, most of vacuum chambers applied in electric propulsion experiments are equipped with anti-sputtering targets. In this paper, a three-dimensional model of plume experimental system (PES) including double layer anti-sputtering target is established. Simulation cases are made to simulate the plasma environment and sputtering effects when an ion thruster is working. The particle in cell (PIC) method and direct simulation Monte Carlo (DSMC) method is used to calculate the velocity and position of particles. Yamamura's model is used to simulate the sputtering process. The distribution of sputtered anti-sputtering target material is presented. The results show that the double layer anti-sputtering target can significantly reduce the deposition on thruster surface. The back-sputtering deposition rates on thruster exit surface for different cases are compared. The chevrons on the secondary target are rearranged to improve its performance. The position of secondary target has relation with the ion beam divergence angle, and the radius of the vacuum chamber. The back-sputtering deposition rate is lower when the secondary target covers the entire ion beam.
Three dimensional numerical simulation of welding temperature fields in stainless steel
Institute of Scientific and Technical Information of China (English)
董志波; 魏艳红; 刘仁培; 董祖珏
2004-01-01
Three kinds of mathematical models representing welding heat sources are presented. Among them, Gaussian model and double ellipsoidal model are used to analyze the thermal distributions with finite element method. At the same time, this paper analyzed the influences of the heat source models, the latent heat and the welding parameters on the temperature distributions. The comparisons between the simulated results and the experiments show double ellipsoidal model is good for three-dimensional numerical simulations. Furthermore, the adaptive mesh technique is applied in the three-dimensional model which greatly reduces the number of nodes and elements in the simulation.
Šimonka, Vito; Nawratil, Georg; Hössinger, Andreas; Weinbub, Josef; Selberherr, Siegfried
2017-02-01
We investigate anisotropical and geometrical aspects of hexagonal structures of Silicon Carbide and propose a direction dependent interpolation method for oxidation growth rates. We compute three-dimensional oxidation rates and perform one-, two-, and three-dimensional simulations for 4H- and 6H-Silicon Carbide thermal oxidation. The rates of oxidation are computed according to the four known growth rate values for the Si- (0 0 0 1) , a- (1 1 2 bar 0) , m- (1 1 bar 0 0) , and C-face (0 0 0 1 bar) . The simulations are based on the proposed interpolation method together with available thermal oxidation models. We additionally analyze the temperature dependence of Silicon Carbide oxidation rates for different crystal faces using Arrhenius plots. The proposed interpolation method is an essential step towards highly accurate three-dimensional oxide growth simulations which help to better understand the anisotropic nature and oxidation mechanism of Silicon Carbide.
Three-dimensional virtual simulation of alar width changes following bimaxillary osteotomies
Liebregts, J.; Xi, T.; Schreurs, R; Loon, B. van; Berge, S.; Maal, T.
2016-01-01
The aim of this study was to evaluate the accuracy of three-dimensional (3D) soft tissue simulation of nose width changes following bimaxillary osteotomies and to identify patient- and surgery-related factors that may affect the accuracy of simulation. Sixty patients (mean age 26 years) who
Three-dimensional virtual simulation of alar width changes following bimaxillary osteotomies
Liebregts, J.; Xi, T.; Schreurs, R; Loon, B. van; Berge, S.; Maal, T.
2016-01-01
The aim of this study was to evaluate the accuracy of three-dimensional (3D) soft tissue simulation of nose width changes following bimaxillary osteotomies and to identify patient- and surgery-related factors that may affect the accuracy of simulation. Sixty patients (mean age 26 years) who underwen
Three-dimensional geometric simulations of random anisotropic growth during transformation phenomena
DEFF Research Database (Denmark)
Godiksen, Rasmus Brauner; Rios, P.R.; Vandermeer, Roy Allen
2008-01-01
predict the results for random ellipsoids up to aspect ratios of at least four, making the effects of random anisotropic growth less pronounced than what has previously been predicted from two-dimensional simulations or other, more restrictive three-dimensional simulations. (c) 2007 Acta Materialia Inc....... Published by Elsevier Ltd. All rights reserved....
Yuan, Xingqiu; Trichtchenko, Larisa; Boteler, David
Propagation of coronal mass ejections from solar surface to the Earth magnetosphere is strongly influenced by the conditions in solar corona and ambient solar wind. Thus, reliable simulation of the background solar wind is the primary task toward the development of numerical model for the transient events. In this paper we introduce a new numerical model which has been specifically designed for numerical study of the solar corona and ambient solar wind. This model is based on our recently developed three-dimensional Spherical Coordinate Adaptive Magneto-Hydro-Dynamic (MHD) code (SCA-MHD-3D) [Yuan et al., 2009]. Modifications has been done to include the observed magnetic field at the photosphere as inner boundary conditions. The energy source term together with reduced plasma gamma are used in the nonlinear MHD equations in order to simulate the solar wind acceleration from subsonic speed at solar surface to supersonic speed at the inter-heliosphere region, and the absorbing boundary conditions are used at the solar surface. This model has been applied to simulate the background solar wind condition for several different solar rotations, and comparison between the observation and model output have shown that it reproduces many features of solar wind, including open and closed magnetic fields, fast and slow solar wind speed, sector boundaries, etc.
A temporal three-dimensional simulation of samarium release in the ionosphere
Zhao, Hai-Sheng; Feng, Jie; Xu, Zheng-Wen; Wu, Jian; Wu, Zhen-Sen; Xu, Bin; Xue, Kun; Xu, Tong; Hu, Yan-Li
2016-10-01
For understanding plasma processes of the ionosphere and magnetosphere, the alkali and alkaline-earth metals are usually released in space for artificially increasing the electron density. However, it is a limitation that these releases must be in sunlight where the photoionization can take place. In recent years, the lanthanide metals, such as samarium, have been released to produce electrons in reaction with atomic oxygen in the upper space. The reaction could proceed without sunlight so that the restriction on experimental periods is broken. Unfortunately, any sophisticated models even preliminary ones are unavailable yet in the literature. A temporal three-dimensional model is presented for the samarium release in detail with respect to various altitudes and mass. Especially, the plasma diffusion equation is remarkably extended from 2-D to 3-D by importing the influence of geomagnetic declination, which could be also useful for other chemical releases. The field-aligned terms are brought so as to the presented model can describe the diffusion along the geomagnetic field subtly. On the basis of the presented model, behaviors of radio waves propagating through the release area are simulated by using ray tracing. This model could be as the theoretical support for samarium releases, and it also helpful for the research on the generation and evolution of the ionosphere irregularities.
IBSIMU: A three-dimensional simulation software for charged particle opticsa)
Kalvas, T.; Tarvainen, O.; Ropponen, T.; Steczkiewicz, O.; ńrje, J.; Clark, H.
2010-02-01
A general-purpose three-dimensional (3D) simulation code IBSIMU for charged particle optics with space charge is under development at JYFL. The code was originally developed for designing a slit-beam plasma extraction and nanosecond scale chopping for pulsed neutron generator, but has been developed further and has been used for many applications. The code features a nonlinear FDM Poisson's equation solver based on fast stabilized biconjugate gradient method with ILU0 preconditioner for solving electrostatic fields. A generally accepted nonlinear plasma model is used for plasma extraction. Magnetic fields can be imported to the simulations from other programs. The particle trajectories are solved using adaptive Runge-Kutta method. Steady-state and time-dependent problems can be modeled in cylindrical coordinates, two-dimensional (slit) geometry, or full 3D. The code is used via C++ programming language for versatility but it features an interactive easy-to-use postprocessing tool for diagnosing fields and particle trajectories. The open source distribution and public documentation make the code well suited for scientific use. IBSIMU has been used for modeling the 14 GHz ECR ion source extraction and for designing a four-electrode extraction for a 2.45 GHz microwave ion source at Jyväskylä. A grid extraction has also been designed for producing large uniform beam for creating conditions similar to solar wind. The code has also been used to design a H- extraction with electron dumping for the Cyclotron Institute of Texas A&M University.
IBSIMU: A three-dimensional simulation software for charged particle optics
Energy Technology Data Exchange (ETDEWEB)
Kalvas, T.; Tarvainen, O.; Ropponen, T.; Steczkiewicz, O.; Aerje, J. [Department of Physics, University of Jyvaeskylae, Jyvaeskylae 40500 (Finland); Clark, H. [Cyclotron Institute, Texas A and M University, College Station, Texas 77843 (United States)
2010-02-15
A general-purpose three-dimensional (3D) simulation code IBSIMU for charged particle optics with space charge is under development at JYFL. The code was originally developed for designing a slit-beam plasma extraction and nanosecond scale chopping for pulsed neutron generator, but has been developed further and has been used for many applications. The code features a nonlinear FDM Poisson's equation solver based on fast stabilized biconjugate gradient method with ILU0 preconditioner for solving electrostatic fields. A generally accepted nonlinear plasma model is used for plasma extraction. Magnetic fields can be imported to the simulations from other programs. The particle trajectories are solved using adaptive Runge-Kutta method. Steady-state and time-dependent problems can be modeled in cylindrical coordinates, two-dimensional (slit) geometry, or full 3D. The code is used via C++ programming language for versatility but it features an interactive easy-to-use postprocessing tool for diagnosing fields and particle trajectories. The open source distribution and public documentation make the code well suited for scientific use. IBSIMU has been used for modeling the 14 GHz ECR ion source extraction and for designing a four-electrode extraction for a 2.45 GHz microwave ion source at Jyvaeskylae. A grid extraction has also been designed for producing large uniform beam for creating conditions similar to solar wind. The code has also been used to design a H{sup -} extraction with electron dumping for the Cyclotron Institute of Texas A and M University.
IBSIMU: a three-dimensional simulation software for charged particle optics.
Kalvas, T; Tarvainen, O; Ropponen, T; Steczkiewicz, O; Arje, J; Clark, H
2010-02-01
A general-purpose three-dimensional (3D) simulation code IBSIMU for charged particle optics with space charge is under development at JYFL. The code was originally developed for designing a slit-beam plasma extraction and nanosecond scale chopping for pulsed neutron generator, but has been developed further and has been used for many applications. The code features a nonlinear FDM Poisson's equation solver based on fast stabilized biconjugate gradient method with ILU0 preconditioner for solving electrostatic fields. A generally accepted nonlinear plasma model is used for plasma extraction. Magnetic fields can be imported to the simulations from other programs. The particle trajectories are solved using adaptive Runge-Kutta method. Steady-state and time-dependent problems can be modeled in cylindrical coordinates, two-dimensional (slit) geometry, or full 3D. The code is used via C++ programming language for versatility but it features an interactive easy-to-use postprocessing tool for diagnosing fields and particle trajectories. The open source distribution and public documentation make the code well suited for scientific use. IBSIMU has been used for modeling the 14 GHz ECR ion source extraction and for designing a four-electrode extraction for a 2.45 GHz microwave ion source at Jyväskylä. A grid extraction has also been designed for producing large uniform beam for creating conditions similar to solar wind. The code has also been used to design a H(-) extraction with electron dumping for the Cyclotron Institute of Texas A&M University.
Three dimensional simulation of the arc inside an insulator-arrester with a multichamber system
Guo, Zhiwei; Long, Xinping; Qian, Zhongdong; Qiu, Ning
2016-04-01
Based on the thermo-physical properties of plasma air, the temperature and flow fields of an insulator-arrester with a multi-chamber system are investigated using three-dimensional computational fluid dynamics. The plasma flow is assumed to be steady incompressible laminar flow and in local thermodynamic equilibrium. The results obtained show that the arc inside the chamber bends downwards, indicating that the Lorentz force induced is directed away from the exit and pushes plasma air down. The outlet also provides passage for plasma flow both in and out of the chamber.
Three dimensional simulation of the arc inside an insulator-arrester with a multichamber system
Directory of Open Access Journals (Sweden)
Zhiwei Guo
2016-04-01
Full Text Available Based on the thermo-physical properties of plasma air, the temperature and flow fields of an insulator–arrester with a multi-chamber system are investigated using three-dimensional computational fluid dynamics. The plasma flow is assumed to be steady incompressible laminar flow and in local thermodynamic equilibrium. The results obtained show that the arc inside the chamber bends downwards, indicating that the Lorentz force induced is directed away from the exit and pushes plasma air down. The outlet also provides passage for plasma flow both in and out of the chamber.
Mitic, S; Khrapak, S A; Morfill, G E; 10.1063/1.4798418
2013-01-01
We report on the first detailed analysis of large three dimensional (3D) complex plasma structures in experiments performed in pure rf and combined rf+dc discharge modes. Inductively coupled plasma (ICP) is generated by an rf coil wrapped around the vertically positioned cylindrical glass tube at a pressure of 0.3 mbar. In addition, dc plasma can be generated by applying voltage to the electrodes at the ends of the tube far from the rf coil. The injected monodisperse particles are levitated in the plasma below the coil. A scanning laser sheet and a high resolution camera are used to determine the 3D positions of about $10^5$ particles. The observed bowl-shaped particle clouds reveal coexistence of various structures, including well-distinguished solid-like, less ordered liquid-like, and pronounced string-like phases. New criteria to identify string-like structures are proposed.
Fisher, Ellen R
2013-10-09
Low-temperature plasmas offer a versatile method for delivering tailored functionality to a range of materials. Despite the vast array of choices offered by plasma processing techniques, there remain a significant number of hurdles that must be overcome to allow this methodology to realize its full potential in the area of biocompatible materials. Challenges include issues associated with analytical characterization, material structure, plasma processing, and uniform composition following treatment. Specific examples and solutions are presented utilizing results from analyses of three-dimensional (3D) poly(ε-caprolactone) scaffolds treated with different plasma surface modification strategies that illustrate these challenges well. Notably, many of these strategies result in 3D scaffolds that are extremely hydrophilic and that enhance human Saos-2 osteoblast cell growth and proliferation, which are promising results for applications including tissue engineering and advanced biomedical devices.
The core helium flash revisited. II. Two and three-dimensional hydrodynamic simulations
Mocák, M.; Müller, E.; Weiss, A.; Kifonidis, K.
2009-07-01
Context: We study turbulent convection during the core helium flash close to its peak by comparing the results of two and three-dimensional hydrodynamic simulations. Aims: In a previous study we found that the temporal evolution and the properties of the convection inferred from two-dimensional hydrodynamic studies are similar to those predicted by quasi-hydrostatic stellar evolutionary calculations. However, as vorticity is conserved in axisymmetric flows, two-dimensional simulations of convection are characterized by incorrect dominant spatial scales and exaggerated velocities. Here, we present three-dimensional simulations that eliminate the restrictions and flaws of two-dimensional models and that provide a geometrically unbiased insight into the hydrodynamics of the core helium flash. In particular, we study whether the assumptions and predictions of stellar evolutionary calculations based on the mixing-length theory can be confirmed by hydrodynamic simulations. Methods: We used a multidimensional Eulerian hydrodynamics code based on state-of-the-art numerical techniques to simulate the evolution of the helium core of a 1.25 M⊙ Pop I star. Results: Our three-dimensional hydrodynamic simulations of the evolution of a star during the peak of the core helium flash do not show any explosive behavior. The convective flow patterns developing in the three-dimensional models are structurally different from those of the corresponding two-dimensional models, and the typical convective velocities are lower than those found in their two-dimensional counterparts. Three-dimensional models also tend to agree more closely with the predictions of mixing length theory. Our hydrodynamic simulations show the turbulent entrainment that leads to a growth of the convection zone on a dynamic time scale. In contrast to mixing length theory, the outer part of the convection zone is characterized by a subadiabatic temperature gradient.
Large Eddy Simulations of the Flow in a Three-Dimensional Ventilated Room
DEFF Research Database (Denmark)
Davidson, Lars; Nielsen, Peter V.
We have done Large Eddy Simulations (LES) of the flow in a three-dimensional ventilated room. A finite volume method is used with a collocated grid arrangement. The momentum equations are solved with an explicit method using central differencing for all terms. The pressure is obtained from...
DEFF Research Database (Denmark)
Thornton, Katsuyo; Poulsen, Henning Friis
2008-01-01
. Combined with three-dimensional (3D) simulations and analyses that are capable of handling the complexity of these microstructures, 3D reconstruction, or tomography, has become a powerful tool that provides clear insights into materials processing and properties. This introductory article provides...... an overview of this emerging field of materials science, as well as brief descriptions of selected methods and their applicability....
Direct numerical simulation of three-dimensional coherent structure in plane mixing layer
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
The three-dimensional temporally evolving plane mixing layer is sinulated by directly solying the Navier-Stokes equations using pseudo-spectral method. The process of loss of stability, and the formation paring, and development of vortex are presented. The simulated result shows that the evolving characteristics of coherent structure are important mechanism of growing and entrainment of mixing layer.
The core helium flash revisited: II. Two and three-dimensional hydrodynamic simulations
Mocak, M; Weiss, A; Kifonidis, K
2008-01-01
We study turbulent convection during the core helium flash close to its peak by comparing the results of two and three-dimensional hydrodynamic simulations. We use a multidimensional Eulerian hydrodynamics code based on state-of-the-art numerical techniques to simulate the evolution of the helium core of a $1.25 M_{\\odot}$ Pop I star. Our three-dimensional hydrodynamic simulations of the evolution of a star during the peak of the core helium flash do not show any explosive behavior. The convective flow patterns developing in the three-dimensional models are structurally different from those of the corresponding two-dimensional models, and the typical convective velocities are smaller than those found in their two-dimensional counterparts. Three-dimensional models also tend to agree better with the predictions of mixing length theory. Our hydrodynamic simulations show the presence of turbulent entrainment that results in a growth of the convection zone on a dynamic time scale. Contrary to mixing length theory,...
Institute of Scientific and Technical Information of China (English)
Zhi-yue Zhang
2002-01-01
Both numerical simulation and theoretical analysis of seawater intrusion in coastal regions are of great theoretical importance in environmental sciences. The mathematical model can be described as a coupled system of three dimensional nonlinear partial differential equations with initial-boundary value problems. In this paper, according to the actual conditions of molecular and three-dimensional characteristic of the problem,we construct the characteristic finite element alternating-direction schemes which can be divided into three continuous one-dimensional problems. By making use of tensor product algorithm, and priori estimation theory and techniques, the optimal order estimates in H1 norm are derived for the error in the approximate solution.
Liang, Fayun; Chen, Haibing; Huang, Maosong
2017-07-01
To provide appropriate uses of nonlinear ground response analysis for engineering practice, a three-dimensional soil column with a distributed mass system and a time domain numerical analysis were implemented on the OpenSees simulation platform. The standard mesh of a three-dimensional soil column was suggested to be satisfied with the specified maximum frequency. The layered soil column was divided into multiple sub-soils with a different viscous damping matrix according to the shear velocities as the soil properties were significantly different. It was necessary to use a combination of other one-dimensional or three-dimensional nonlinear seismic ground analysis programs to confirm the applicability of nonlinear seismic ground motion response analysis procedures in soft soil or for strong earthquakes. The accuracy of the three-dimensional soil column finite element method was verified by dynamic centrifuge model testing under different peak accelerations of the earthquake. As a result, nonlinear seismic ground motion response analysis procedures were improved in this study. The accuracy and efficiency of the three-dimensional seismic ground response analysis can be adapted to the requirements of engineering practice.
Energy Technology Data Exchange (ETDEWEB)
Kaneko, Tsuyoshi; Kobayashi, Masahiro; Nakajima, Hideo; Fujino, Toyomi (Keio Univ., Tokyo (Japan). School of Medicine)
1992-12-01
The author's three surgical simulation systems are presented. First the computer graphics surgical simulation system has been developed which make the three dimensional skull image from CT scans and the arbitrary osteotomy, mobilization of bone segments and prediction of post-operative appearance is made possible. The second system is solid modeling of the skull using laser curable resin and it is concluded that life-sized skull model is useful not only for surgical simulation of major craniofacial surgery but also educational purposes. The third one is solid modeling of the ear using non-contact 3-D shape measurement with slit laser scanner. The mirror image life-sized wax model is made from the normal side of th ear and the autologous cartilage framework is assembled to simulate the wax model, thus the precise three dimensional reconstruction of the auricle is made possible. (author).
THREE-DIMENSIONAL WEB-BASED PHYSICS SIMULATION APPLICATION FOR PHYSICS LEARNING TOOL
Directory of Open Access Journals (Sweden)
William Salim
2012-10-01
Full Text Available The purpose of this research is to present a multimedia application for doing simulation in Physics. The application is a web based simulator that implementing HTML5, WebGL, and JavaScript. The objects and the environment will be in three dimensional views. This application is hoped will become the substitute for practicum activity. The current development is the application only covers Newtonian mechanics. Questionnaire and literature study is used as the data collecting method. While Waterfall Method used as the design method. The result is Three-DimensionalPhysics Simulator as online web application. Three-Dimensionaldesign and mentor-mentee relationship is the key features of this application. The conclusion made is Three-DimensionalPhysics Simulator already fulfilled in both design and functionality according to user. This application also helps them to understand Newtonian mechanics by simulation. Improvements are needed, because this application only covers Newtonian Mechanics. There is a lot possibility in the future that this simulation can also covers other Physics topic, such as optic, energy, or electricity.Keywords: Simulation, Physic, Learning Tool, HTML5, WebGL
Hyakutake, Toru; Nagai, Shinya
2015-01-01
We constructed three-dimensional microvascular bifurcation models using a parent vessel of diameter 10μm and investigated the flow behavior of the red blood cells (RBCs) through bifurcations. We considered symmetric and asymmetric model types. Two cases of equal daughter vessel diameter were employed for the asymmetric models, where the first was 10μm, which is the same as the parent vessel and the second was 7.94μm, which satisfies Murray's law. Simulated blood flow was computed using the lattice Boltzmann method in conjunction with the immersed boundary method for incorporating fluid-membrane interactions between the flow field and deformable RBCs. First, we investigated the flow behavior of a single RBC through microvascular bifurcations. In the case of the symmetric bifurcation, the turning point of the fractional plasma flow wherein the RBC flow changed from one daughter vessel to the other was 0.50. This turning point was however different for asymmetric bifurcations. Additionally, we varied the initial offset of RBCs from the centerline of the parent vessel. The simulation results indicated that the RBCs preferentially flow through the branch of a larger flow ratio. Next, we investigated the distribution characteristics of multiple RBCs. Simulations indicated that the results of the symmetric model were similar to those predicted by a previously published empirical model. On the other hand, results of asymmetric models deviated from those of the symmetric and empirical models. These results suggest that the distribution of RBCs varies according to the bifurcation angle and daughter vessel diameter in a microvascular bifurcation of the size considered.
Energy Technology Data Exchange (ETDEWEB)
Haines, Brian M.; Grim, Gary P.; Fincke, James R.; Shah, Rahul C.; Forrest, Chad J.; Silverstein, Kevin; Marshall, Frederic J.; Boswell, Melissa; Fowler, Malcolm M.; Gore, Robert A.; Hayes-Sterbenz, Anna C.; Jungman, Gerard; Klein, Andreas; Rundberg, Robert S.; Steinkamp, Michael J.; Wilhelmy, Jerry B.
2016-07-01
We present results from the comparison of high-resolution three-dimensional (3D) simulations with data from the implosions of inertial confinement fusion capsules with separated reactants performed on the OMEGA laser facility. Each capsule, referred to as a “CD Mixcap,” is filled with tritium and has a polystyrene (CH) shell with a deuterated polystyrene (CD) layer whose burial depth is varied. In these implosions, fusion reactions between deuterium and tritium ions can occur only in the presence of atomic mix between the gas fill and shell material. The simulations feature accurate models for all known experimental asymmetries and do not employ any adjustable parameters to improve agreement with experimental data. Simulations are performed with the RAGE radiation-hydrodynamics code using an Implicit Large Eddy Simulation (ILES) strategy for the hydrodynamics. We obtain good agreement with the experimental data, including the DT/TT neutron yield ratios used to diagnose mix, for all burial depths of the deuterated shell layer. Additionally, simulations demonstrate good agreement with converged simulations employing explicit models for plasma diffusion and viscosity, suggesting that the implicit sub-grid model used in ILES is sufficient to model these processes in these experiments. In our simulations, mixing is driven by short-wavelength asymmetries and longer-wavelength features are responsible for developing flows that transport mixed material towards the center of the hot spot. Mix material transported by this process is responsible for most of the mix (DT) yield even for the capsule with a CD layer adjacent to the tritium fuel. Consistent with our previous results, mix does not play a significant role in TT neutron yield degradation; instead, this is dominated by the displacement of fuel from the center of the implosion due to the development of turbulent instabilities seeded by long-wavelength asymmetries. Through these processes, the long
Energy Technology Data Exchange (ETDEWEB)
Haines, Brian M., E-mail: bmhaines@lanl.gov; Fincke, James R.; Shah, Rahul C.; Boswell, Melissa; Fowler, Malcolm M.; Gore, Robert A.; Hayes-Sterbenz, Anna C.; Jungman, Gerard; Klein, Andreas; Rundberg, Robert S.; Steinkamp, Michael J.; Wilhelmy, Jerry B. [Los Alamos National Laboratory, MS T087, Los Alamos, New Mexico 87545 (United States); Grim, Gary P. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Forrest, Chad J.; Silverstein, Kevin; Marshall, Frederic J. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States)
2016-07-15
We present results from the comparison of high-resolution three-dimensional (3D) simulations with data from the implosions of inertial confinement fusion capsules with separated reactants performed on the OMEGA laser facility. Each capsule, referred to as a “CD Mixcap,” is filled with tritium and has a polystyrene (CH) shell with a deuterated polystyrene (CD) layer whose burial depth is varied. In these implosions, fusion reactions between deuterium and tritium ions can occur only in the presence of atomic mix between the gas fill and shell material. The simulations feature accurate models for all known experimental asymmetries and do not employ any adjustable parameters to improve agreement with experimental data. Simulations are performed with the RAGE radiation-hydrodynamics code using an Implicit Large Eddy Simulation (ILES) strategy for the hydrodynamics. We obtain good agreement with the experimental data, including the DT/TT neutron yield ratios used to diagnose mix, for all burial depths of the deuterated shell layer. Additionally, simulations demonstrate good agreement with converged simulations employing explicit models for plasma diffusion and viscosity, suggesting that the implicit sub-grid model used in ILES is sufficient to model these processes in these experiments. In our simulations, mixing is driven by short-wavelength asymmetries and longer-wavelength features are responsible for developing flows that transport mixed material towards the center of the hot spot. Mix material transported by this process is responsible for most of the mix (DT) yield even for the capsule with a CD layer adjacent to the tritium fuel. Consistent with our previous results, mix does not play a significant role in TT neutron yield degradation; instead, this is dominated by the displacement of fuel from the center of the implosion due to the development of turbulent instabilities seeded by long-wavelength asymmetries. Through these processes, the long
Haines, Brian M.; Grim, Gary P.; Fincke, James R.; Shah, Rahul C.; Forrest, Chad J.; Silverstein, Kevin; Marshall, Frederic J.; Boswell, Melissa; Fowler, Malcolm M.; Gore, Robert A.; Hayes-Sterbenz, Anna C.; Jungman, Gerard; Klein, Andreas; Rundberg, Robert S.; Steinkamp, Michael J.; Wilhelmy, Jerry B.
2016-07-01
We present results from the comparison of high-resolution three-dimensional (3D) simulations with data from the implosions of inertial confinement fusion capsules with separated reactants performed on the OMEGA laser facility. Each capsule, referred to as a "CD Mixcap," is filled with tritium and has a polystyrene (CH) shell with a deuterated polystyrene (CD) layer whose burial depth is varied. In these implosions, fusion reactions between deuterium and tritium ions can occur only in the presence of atomic mix between the gas fill and shell material. The simulations feature accurate models for all known experimental asymmetries and do not employ any adjustable parameters to improve agreement with experimental data. Simulations are performed with the RAGE radiation-hydrodynamics code using an Implicit Large Eddy Simulation (ILES) strategy for the hydrodynamics. We obtain good agreement with the experimental data, including the DT/TT neutron yield ratios used to diagnose mix, for all burial depths of the deuterated shell layer. Additionally, simulations demonstrate good agreement with converged simulations employing explicit models for plasma diffusion and viscosity, suggesting that the implicit sub-grid model used in ILES is sufficient to model these processes in these experiments. In our simulations, mixing is driven by short-wavelength asymmetries and longer-wavelength features are responsible for developing flows that transport mixed material towards the center of the hot spot. Mix material transported by this process is responsible for most of the mix (DT) yield even for the capsule with a CD layer adjacent to the tritium fuel. Consistent with our previous results, mix does not play a significant role in TT neutron yield degradation; instead, this is dominated by the displacement of fuel from the center of the implosion due to the development of turbulent instabilities seeded by long-wavelength asymmetries. Through these processes, the long
Three-Dimensional Numerical Simulation of Plate Forming by Line Heating
DEFF Research Database (Denmark)
Clausen, Henrik Bisgaard
1999-01-01
addressed the problem of simulating the process, and although very few have been successful in gaining accurate results valuable information about the mechanics have been derived. However, the increasing power of computers now allows for numerical simulations of the forming process using a three......-dimensional thermo-mechanical model. Although very few have been successful in gaining accurate results valuable information about the mechanics has been derived. However, the increasing power of computers now allows for numerical simulations of the forming process using a three-dimensional thermo-mechanical model.......Line Heating is the process of forming (steel) plates into shape by means of localised heating often along a line. Though any focussed heat source will do, the inexpensive and widely available oxyacettylene gas torch is commonly applied in ship production.Over the years, many researchers have...
Three-dimensional antenna coupling to core plasma in fusion devices
Energy Technology Data Exchange (ETDEWEB)
Carter, M.D.; Jaeger, E.F.; Stallings, D.C.; Galambos, J.D.; Batchelor, D.B.; Wang, C.Y.
1995-09-01
A complete understanding of the RF physics from the launcher to the plasma core is required to fully analyze RF experiments and to evaluate the performance of RF antenna designs in ITER. This understanding requires a consistent model for the RF power launching system, propagation and absorption through the edge region, and the response of the core plasma to the RF power. As a first step toward such a model, the three-dimensional (3D) antenna modeling code, RANT3D, has been coupled with the reduced order full wave code, PICES. Preliminary results from this model are presented in this paper for parameters similar to those found in the DIII-D experiment.
CALCULATION OF VISCOUS FLOW AROUND CIRCULAR CYLINDER WITH THREE-DIMENSIONAL NUMERICAL SIMULATION
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
Three-dimensional numerical simulation of a uniform incompressible viscous flow around a stationary circular cylinder was conducted. The CFX-4 software was used to calculate the hydrodynamic characteristics of the flow and the finite volume method for incompressible Navier-Stokes equations was employed in the program. The simulation of the flow was performed for Re=103 and Re=104 respectively within the sub-critical region. In order to overcome numerical instability for the high Reynolds number flows, a quadratic upwind scheme was incorporated for the Navier-Stokes equations. The periodicity boundary condition was used at the ends of the cylinder. It was found that the evolution of the lift and drag coefficients in each plane along the cylinder span is different. Comparison between the predicted results based on the three-dimensional and the two-dimensional analysis was also given. It is concluded that at the high Reynolds number the effect of three-dimensionality of the flow around the circular cylinder is remarkable, and in addition hydrodynamic coefficients with of 3-D simulation are less than those given by 2-D simulation.
Mechanisms of Methylene Blue Degradation in Three-dimensionally Integrated Micro-solution Plasma
Nomura, Ayano; Hayashi, Yui; Tanaka, Kenji; Shirafuji, Tatsuru; Goto, Motonobu
2015-09-01
Plasma in aqueous solution has attracted much attention because they are expected to have possibilities to solve water-related environmental issues. In such application-oriented researches, degradation of methylene blue (MB) or other organic dyes has been widely used for investigating the effects of the plasma treatment on the water with organic contaminants. However, there are few reports on the detailed analysis of the products after the plasma treatment of MB aqueous solution for understanding mechanisms of the degradation processes. We have hence analyzed our degradation products using matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry. We have performed the MB degradation in three-dimensionally integrated micro-solution plasma, which has shown 16-fold higher performance in MB degradation than conventional solution plasma. The results of MALDI-TOF mass spectrometry have indicated the formation of sulfoxides in the first stage of the degradation. Then, the methyl groups on the sulfoxides are partially oxidized. The sulfoxides are separated to form two benzene derivatives after that. Finally, weak functional groups are removed from the benzene derivatives.
Energy Technology Data Exchange (ETDEWEB)
Nakamura, Naoki [Division of Physics and Astronomy, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502 (Japan); Shibata, Kazunari [Kwaan and Hida Observatories, Kyoto University, Yamashina, Kyoto 607-8471 (Japan); Isobe, Hiroaki, E-mail: nakamura@kwasan.kyoto-u.ac.jp, E-mail: shibata@kwasan.kyoto-u.ac.jp, E-mail: isobe@kwasan.kyoto-u.ac.jp [Unit of Synergetic Studies for Space, Kyoto University, Yamashina, Kyoto 607-8471 (Japan)
2012-12-20
Three-dimensional (3D) component reconnection, where reconnecting field lines are not perfectly anti-parallel, is studied with a 3D magnetohydrodynamic simulation. In particular, we consider the asymmetry of the field strength of the reconnecting field lines. As the asymmetry increases, the generated reconnection jet tends to be parallel to stronger field lines. This is because weaker field lines have higher gas pressure in the initial equilibrium, and hence the gas pressure gradient along the reconnected field lines is generated, which accelerates the field-aligned plasma flow. This mechanism may explain penumbral microjets and other types of jets that are parallel to magnetic field lines.
DEFF Research Database (Denmark)
Stamate, Eugen; Yamaguchi, Masahito
2015-01-01
Modal and discrete focusing effects associated with three-dimensional plasma-sheath-lenses show promising potential for applications in ion beam extraction, mass spectrometry, plasma diagnostics and for basic studies of plasma sheath. The ion focusing properties can be adjusted by controlling the...
Abe, Makito; Hasegawa, Kenji
2016-01-01
We explore the possibility of the formation of globular clusters under ultraviolet (UV) background radiation. One-dimensional spherical symmetric radiation hydrodynamics (RHD) simulations by Hasegawa et al. have demonstrated that the collapse of low-mass (10^6-10^7 solar masses) gas clouds exposed to intense UV radiation can lead to the formation of compact star clusters like globular clusters (GCs) if gas clouds contract with supersonic infall velocities. However, three-dimensional effects, such as the anisotropy of background radiation and the inhomogeneity in gas clouds, have not been studied so far. In this paper, we perform three-dimensional RHD simulations in a semi-cosmological context, and reconsider the formation of compact star clusters in strong UV radiation fields. As a result, we find that although anisotropic radiation fields bring an elongated shadow of neutral gas, almost spherical compact star clusters can be procreated from a "supersonic infall" cloud, since photo-dissociating radiation supp...
Three-dimensional simulations of phase separation in model binary alloy systems with elasticity
Energy Technology Data Exchange (ETDEWEB)
Orlikowski, D.; Roland, C. [North Carolina State Univ., Raleigh, NC (United States); Sagui, C. [McGill Univ., Montreal, Quebec (Canada). Dept. of Physics; Somoza, A.S. [Univ. de Murcia (Spain). Dept. de Fisica
1998-12-31
The authors report on large-scale three-dimensional simulations of phase separation in model binary alloy systems in the presence of elastic fields. The elastic field has several important effects on the morphology of the system: the ordered domains are subject to shape transformations, and spatial ordering. In contrast to two-dimensional system, no significant slowing down in the growth is observed. There is also no evidence of any reverse coarsening of the domains.
2011-01-01
Three-dimensional numerical simulation of SOFC anode polarization is conducted with a structure obtained by a focused ion beam and scanning electron microscope (FIB-SEM). Electronic, ionic and gaseous transports with electrochemical reaction are considered. A sub-grid scale model is newly developed and effectively used to evaluate the transport flux in the porous structure. The proposed SGS model shows its potential to reasonably evaluate the transport flux considering the microstructure smal...
Numerical simulation of three-dimensional turbulent flow in multistage axial compressor blade row
Institute of Scientific and Technical Information of China (English)
Jian JIANG; Bo LIU; Yangang WANG; Xiangyi NAN
2008-01-01
Numerical simulation of three-dimensional turbulent flow in a multistage axial compressor blade row is conducted. A high resolution, third-order ENN scheme is adopted to catch the shockwave and simulate the turbulent flow correctly, while an LU-SGS implicit method is chosen to improve computation rate. A detailed and highly efficient numerical simulation system is thus constructed. The investigation is focused on the grid con-necting methods between the rotor and the stator and the corresponding treatment of rotor-stator interactional sur-face. The final results of a three-stage axial compressor with inlet guide vanes conform well to the experimental data.
Shirafuji, Tatsuru; Ishida, Yodai; Nomura, Ayano; Hayashi, Yui; Goto, Motonobu
2017-06-01
We have performed matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) on methylene-blue aqueous solutions treated with three-dimensionally integrated micro-solution plasma, in which we have acquired the time evolution of mass spectra as a function of treatment time. The time evolution of mass spectral peak intensities for major detected species has clearly indicated that the parent methylene-blue molecules are degraded through consecutive reactions. The primary reaction is the oxidation of the parent molecules. The oxidized species still have two benzene rings in the parent molecules. The secondary reactions are the separation of the oxidized species and the formation of compounds with one benzene ring. We have also performed the numerical fitting of the time evolution of the mass spectral peak intensities, the results of which have indicated that we must assume additional primary reactions before the primary oxidation for better agreement with experimental results.
Lattice Boltzmann simulation of three-dimensional Rayleigh-Taylor instability
Liang, H.; Li, Q. X.; Shi, B. C.; Chai, Z. H.
2016-03-01
In this paper, the three-dimensional (3D) Rayleigh-Taylor instability (RTI) with low Atwood number (At=0.15 ) in a long square duct (12 W ×W ×W ) is studied by using a multiple-relaxation-time lattice Boltzmann (LB) multiphase model. The effect of the Reynolds number on the interfacial dynamics and bubble and spike amplitudes at late time is investigated in detail. The numerical results show that at sufficiently large Reynolds numbers, a sequence of stages in the 3D immiscible RTI can be observed, which includes the linear growth, terminal velocity growth, reacceleration, and chaotic development stages. At late stage, the RTI induces a very complicated topology structure of the interface, and an abundance of dissociative drops are also observed in the system. The bubble and spike velocities at late stage are unstable and their values have exceeded the predictions of the potential flow theory [V. N. Goncharov, Phys. Rev. Lett. 88, 134502 (2002), 10.1103/PhysRevLett.88.134502]. The acceleration of the bubble front is also measured and it is found that the normalized acceleration at late time fluctuates around a constant value of 0.16. When the Reynolds number is reduced to small values, some later stages cannot be reached sequentially. The interface becomes relatively smoothed and the bubble velocity at late time is approximate to a constant value, which coincides with the results of the extended Layzer model [S.-I. Sohn, Phys. Rev. E 80, 055302(R) (2009), 10.1103/PhysRevE.80.055302] and the modified potential theory [R. Banerjee, L. Mandal, S. Roy, M. Khan, and M. R. Guptae, Phys. Plasmas 18, 022109 (2011), 10.1063/1.3555523]. In our simulations, the Graphics Processing Unit (GPU) parallel computing is also used to relieve the massive computational cost.
Three-Dimensional Numerical Simulations of Magnetized Winds of Low-Mass Stars
Vidotto, A. A.
2009-11-01
The subject of this thesis is the mass loss of low-mass stars through magnetized coronal winds. Stellar winds have been a topic of extensive research in Astrophysics for a long time, and their first investigations focused on the solar wind. Nowadays, we know that the magnetic field plays a crucial role in the acceleration and heating of coronal winds. Despite of the knowledge of the fine structure of the solar magnetic field, much less information is known regarding the configuration of the magnetic field in other stars. In this thesis, we investigate the structure of the magnetic field in the coronae of solar-like stars and young stars by means of three-dimensional magnetohydrodynamical numerical simulations. We self-consistently take into consideration the interaction of the outflowing wind with the magnetic field and vice versa. Hence, from the interplay between magnetic forces and wind forces, we are able to determine the configuration of the magnetic field and the structure of the coronal winds. We investigate solar-like stellar winds and their dependence on the plasma-beta parameter (the ratio between thermal and magnetic energy densities). This is the first study to perform such analysis solving the fully ideal three-dimensional magnetohydrodynamics equations. We adopt in our simulations a heating parameter described by gamma, which is responsible for the thermal acceleration of the wind. We analyze winds with polar magnetic field intensities ranging from B0 = 1 to 20 G and we show that the wind structure presents characteristics that are similar to the solar coronal wind. The steady-state magnetic field topology for all cases is similar, presenting a configuration of helmet streamer-type, with zones of closed field lines and open field lines coexisting. Higher magnetic field intensities lead to faster and hotter winds. The increase of the field intensity generates a larger "dead zone" in the wind, i.e., the closed loops that inhibit matter to escape from
Simulations of Failure via Three-Dimensional Cracking in Fuel Cladding for Advanced Nuclear Fuels
Energy Technology Data Exchange (ETDEWEB)
Lu, Hongbing [Univ. of Texas, Austin, TX (United States); Bukkapatnam, Satish; Harimkar, Sandip; Singh, Raman; Bardenhagen, Scott
2014-01-09
Enhancing performance of fuel cladding and duct alloys is a key means of increasing fuel burnup. This project will address the failure of fuel cladding via three-dimensional cracking models. Researchers will develop a simulation code for the failure of the fuel cladding and validate the code through experiments. The objective is to develop an algorithm to determine the failure of fuel cladding in the form of three-dimensional cracking due to prolonged exposure under varying conditions of pressure, temperature, chemical environment, and irradiation. This project encompasses the following tasks: 1. Simulate 3D crack initiation and growth under instantaneous and/or fatigue loads using a new variant of the material point method (MPM); 2. Simulate debonding of the materials in the crack path using cohesive elements, considering normal and shear traction separation laws; 3. Determine the crack propagation path, considering damage of the materials incorporated in the cohesive elements to allow the energy release rate to be minimized; 4. Simulate the three-dimensional fatigue crack growth as a function of loading histories; 5. Verify the simulation code by comparing results to theoretical and numerical studies available in the literature; 6. Conduct experiments to observe the crack path and surface profile in unused fuel cladding and validate against simulation results; and 7. Expand the adaptive mesh refinement infrastructure parallel processing environment to allow adaptive mesh refinement at the 3D crack fronts and adaptive mesh merging in the wake of cracks. Fuel cladding is made of materials such as stainless steels and ferritic steels with added alloying elements, which increase stability and durability under irradiation. As fuel cladding is subjected to water, chemicals, fission gas, pressure, high temperatures, and irradiation while in service, understanding performance is essential. In the fast fuel used in advanced burner reactors, simulations of the nuclear
Institute of Scientific and Technical Information of China (English)
WU Wei; YAN Zhong-min; WU Long-hua
2006-01-01
Saline intrusion into marine sewage outfalls will greatly decrease the efficiency of sewage disposal. In order to investigate the mechanisms of this flow, in this paper, a three-dimensional numerical model based on FVM (Finite Volume Method) is established. The RNG k-ε model is selected for turbulence modeling. The time-averaged volume fraction equations are introduced to simulate the stratification and interfacial exchange of sewage and seawater in outfalls. Validity of the established three-dimensional numerical model is evaluated by comparisons of numerical results with experimental data. With this three-dimensional numerical model, the internal flow characteristics in outfalls for different sewage discharges are simulated. The results indicate that for a low sewage discharge, saline circulates in the outfall due to intrusion and both the inflowing momentum and the interfacial turbulent mixing are important mechanisms to extrude the saline. For a high sewage discharge, saline intrusion could be avoided. The inflow momentum is the main mechanism to extrude the saline and the interfacial turbulent mixing is not important relatively. Even at a high sewage discharge, the saline wedge would be retained in the main outfall pipe after the risers are purged. It takes a long time for this saline wedge to be extruded by interfacial turbulent mixing.
Numerical simulation of ac conduction in three-dimensional heterogeneous materials
Pazhoohesh, Elaheh; Hamzehpour, Hossein; Sahimi, Muhammad
2006-05-01
Three-dimensional wavelet transformations and a finite-volume method are combined to develop an efficient method for computing the effective frequency-dependent conductivity of three-dimensional (3D) disordered materials at low temperatures. Such computations have, in the past, been beset by numerical difficulties arising from the local conductivities g(r) varying over many orders of magnitude. A disordered matrerial is modeled by a 3D lattice, and it is assumed that conduction is thermally activated, so that g(r) is related to the activation energies which are distributed according to a probability distribution function (PDF). Five distinct PDF’s are used and, depending on the form of the PDF, the corresponding g(r) varies over 3-17 orders of magnitude. The ac conduction is simulated over 10 orders of magnitude variations in the frequency. The speedup in the computations is up to four orders of magnitude.
THREE-DIMENSIONAL NUMERICAL SIMULATION OF WAVE SLAMMING ON AN OPEN STRUCTURE
Institute of Scientific and Technical Information of China (English)
DING Zhao-qiang; WANG Guo-yu; REN Bing
2012-01-01
The three-dimensional numerical simulation of wave slamming on an open structure in the splash zone is carried out based upon the Volume Of Fluid (VOF) method.A wave basin is established by solving the continuity equation and the Navier-Stoke equations.The linear wave-maker is placed on the left side of the basin,and the numerical sponge layer and the SRC are placed on the right side of the basin to damp the incident waves.The three-dimensional wave slamming boundary condition is adopted to model waves in contact with and separated from the underside of the structure.The numerical results of wave slamming on a foursquare structure for various parametric cases are verified by the experimental results.Meanwhile,the characteristics of the wave impact forces on the undersides of the rectangular structures with various length-breadth ratios are discussed.
Multi-GPU accelerated three-dimensional FDTD method for electromagnetic simulation.
Nagaoka, Tomoaki; Watanabe, Soichi
2011-01-01
Numerical simulation with a numerical human model using the finite-difference time domain (FDTD) method has recently been performed in a number of fields in biomedical engineering. To improve the method's calculation speed and realize large-scale computing with the numerical human model, we adapt three-dimensional FDTD code to a multi-GPU environment using Compute Unified Device Architecture (CUDA). In this study, we used NVIDIA Tesla C2070 as GPGPU boards. The performance of multi-GPU is evaluated in comparison with that of a single GPU and vector supercomputer. The calculation speed with four GPUs was approximately 3.5 times faster than with a single GPU, and was slightly (approx. 1.3 times) slower than with the supercomputer. Calculation speed of the three-dimensional FDTD method using GPUs can significantly improve with an expanding number of GPUs.
Tamburini, M; Liseykina, T V; Pegoraro, F; Macchi, A
2012-01-01
Polarization and radiation reaction (RR) effects in the interaction of a superintense laser pulse (I>10(23) W cm-2) with a thin plasma foil are investigated with three dimensional particle-in-cell (PIC) simulations. For a linearly polarized laser pulse, strong anisotropies such as the formation of two high-energy clumps in the plane perpendicular to the propagation direction and significant radiation reactions effects are observed. On the contrary, neither anisotropies nor significant radiation reaction effects are observed using circularly polarized laser pulses, for which the maximum ion energy exceeds the value obtained in simulations of lower dimensionality. The dynamical bending of the initially flat plasma foil leads to the self-formation of a quasiparabolic shell that focuses the impinging laser pulse strongly increasing its energy and momentum densities.
Seal, S. K.; Cianciosa, M. R.; Hirshman, S. P.; Wingen, A.; Wilcox, R. S.; Unterberg, E. A.
2016-10-01
High-fidelity reconstruction of plasma equilibria in confinement devices like stellarators and tokamaks with external three dimensional (3D) fields is computationally very expensive and routinely requires days, even weeks, to complete using serial approaches. Here, we present the performance results of coupling the 3D plasma reconstruction code, V3FIT, with PARVMEC, the recently developed parallel version of VMEC. We present the parallel design of this coupled software along with a scalability analysis to identify its performance bottlenecks. Dependence of its scalability limits on model parameters is derived. These analyses are supported by scaling studies on over 6,000 processor cores of a Cray XC30 supercomputer. PARVMEC, which dominates the total runtime of the reconstruction procedure, is shown to deliver speedup improvements of over one to two orders of magnitude, depending on whether the equilibrium computations are carried out in a free or fixed boundary mode. The overall speedup of the coupled reconstruction code is shown to deliver over 40X improvement enabling fusion scientists to carry out high-fidelity 3D plasma reconstruction analyses in only a few hours instead of in days/weeks for the first time. This work was supported by the U.S. D.O.E. contract DE-AC05-00OR22725.
Algorithm for statistical noise reduction in three-dimensional ion implant simulations
Energy Technology Data Exchange (ETDEWEB)
Hernandez-Mangas, J.M. E-mail: jesman@ele.uva.es; Arias, J.; Jaraiz, M.; Bailon, L.; Barbolla, J
2001-05-01
As integrated circuit devices scale into the deep sub-micron regime, ion implantation will continue to be the primary means of introducing dopant atoms into silicon. Different types of impurity profiles such as ultra-shallow profiles and retrograde profiles are necessary for deep submicron devices in order to realize the desired device performance. A new algorithm to reduce the statistical noise in three-dimensional ion implant simulations both in the lateral and shallow/deep regions of the profile is presented. The computational effort in BCA Monte Carlo ion implant simulation is also reduced.
Three-dimensional hypersonic rarefied flow calculations using direct simulation Monte Carlo method
Celenligil, M. Cevdet; Moss, James N.
1993-01-01
A summary of three-dimensional simulations on the hypersonic rarefied flows in an effort to understand the highly nonequilibrium flows about space vehicles entering the Earth's atmosphere for a realistic estimation of the aerothermal loads is presented. Calculations are performed using the direct simulation Monte Carlo method with a five-species reacting gas model, which accounts for rotational and vibrational internal energies. Results are obtained for the external flows about various bodies in the transitional flow regime. For the cases considered, convective heating, flowfield structure and overall aerodynamic coefficients are presented and comparisons are made with the available experimental data. The agreement between the calculated and measured results are very good.
Three-dimensional Simulation and Pattern Making of Collar Using Geometric Model
Institute of Scientific and Technical Information of China (English)
Zhang Mingjie(张明杰); Hou Dongyu(侯东昱); Zhou Aiying(周爱英); Yoshio Shimizu
2001-01-01
An algorithm is presented for computationally simulating collars and drafting patterns. The collar shape was modeled by three-dimensional Bezier patch. Changing the position of consol points of the patch can interactively control the collar shape. Using triangular surface developing method, patterns of various styles of stand collar and separating collar were drafted. As the subsystem of 3D apparel design system, an interactive collar design system is constructed. To inspect the practical usage, we reproduced the collars using these patterns drafted by the interactive collar design system.Comparing with simulated collars, the system demonstrated well and we found it is more reliable and accurate than the method of handwork.
Combining cellular automata and Monte Carlo algorithm to simulate three-dimensional grain growth
Institute of Scientific and Technical Information of China (English)
WANG Wei; CHEN Ju-hua; GUO Pei-quan; ZHAO Ping
2006-01-01
A 3-D simulation of grain growth was conducted by utilizing cellular automata (CA) and Monte Carlo (MC) algorithm. In the simulating procedure, the three-dimensional space is divided into a large number of 2-D isometric planes. Then, each of the planes is divided into identical square cells. Finally, the cellular automata and Monte Carlo algorithm are combined together to simulate the grain growth. Through an evolutionary simulation, the recrystallized microstructure, the grain growth rate and the grain size distribution are acceptably predicted. The simulation routine can be used to simulate the real physical-metallurgy processes and to predict quantitative dynamic information of the evolution of microstructure. Further more, the method is also useful for optimization of materials properties by controlling the microstructure evolution.
RICHTER, DAVID
2010-03-29
The results from a numerical investigation of inertial viscoelastic flow past a circular cylinder are presented which illustrate the significant effect that dilute concentrations of polymer additives have on complex flows. In particular, effects of polymer extensibility are studied as well as the role of viscoelasticity during three-dimensional cylinder wake transition. Simulations at two distinct Reynolds numbers (Re = 100 and Re = 300) revealed dramatic differences based on the choice of the polymer extensibility (L2 in the FENE-P model), as well as a stabilizing tendency of viscoelasticity. For the Re = 100 case, attention was focused on the effects of increasing polymer extensibility, which included a lengthening of the recirculation region immediately behind the cylinder and a sharp increase in average drag when compared to both the low extensibility and Newtonian cases. For Re = 300, a suppression of the three-dimensional Newtonian mode B instability was observed. This effect is more pronounced for higher polymer extensibilities where all three-dimensional structure is eliminated, and mechanisms for this stabilization are described in the context of roll-up instability inhibition in a viscoelastic shear layer. © 2010 Cambridge University Press.
Three-dimensional quasistatic model for high brightness beam dynamics simulation
Qiang, Ji; Lidia, Steve; Ryne, Robert D.; Limborg-Deprey, Cecile
2006-04-01
In this paper, we present a three-dimensional quasistatic model for high brightness beam dynamics simulation in rf/dc photoinjectors, rf linacs, and similar devices on parallel computers. In this model, electrostatic space-charge forces within a charged particle beam are calculated self-consistently at each time step by solving the three-dimensional Poisson equation in the beam frame and then transforming back to the laboratory frame. When the beam has a large energy spread, it is divided into a number of energy bins or slices so that the space-charge forces are calculated from the contribution of each bin and summed together. Image-charge effects from conducting photocathode are also included efficiently using a shifted-Green function method. For a beam with large aspect ratio, e.g., during emission, an integrated Green function method is used to solve the three-dimensional Poisson equation. Using this model, we studied beam transport in one Linac Coherent Light Sources photoinjector design through the first traveling wave linac with initial misalignment with respect to the accelerating axis.
Liu, Jianjun; Song, Rui; Cui, Mengmeng
2014-01-01
A novel approach of simulating hydromechanical coupling in pore-scale models of porous media is presented in this paper. Parameters of the sandstone samples, such as the stress-strain curve, Poisson's ratio, and permeability under different pore pressure and confining pressure, are tested in laboratory scale. The micro-CT scanner is employed to scan the samples for three-dimensional images, as input to construct the model. Accordingly, four physical models possessing the same pore and rock matrix characteristics as the natural sandstones are developed. Based on the micro-CT images, the three-dimensional finite element models of both rock matrix and pore space are established by MIMICS and ICEM software platform. Navier-Stokes equation and elastic constitutive equation are used as the mathematical model for simulation. A hydromechanical coupling analysis in pore-scale finite element model of porous media is simulated by ANSYS and CFX software. Hereby, permeability of sandstone samples under different pore pressure and confining pressure has been predicted. The simulation results agree well with the benchmark data. Through reproducing its stress state underground, the prediction accuracy of the porous rock permeability in pore-scale simulation is promoted. Consequently, the effects of pore pressure and confining pressure on permeability are revealed from the microscopic view. PMID:24955384
Finite-Difference Time-Domain Simulation for Three-dimensional Polarized Light Imaging
Menzel, Miriam; De Raedt, Hans; Michielsen, Kristel
2016-01-01
Three-dimensional Polarized Light Imaging (3D-PLI) is a promising technique to reconstruct the nerve fiber architecture of human post-mortem brains from birefringence measurements of histological brain sections with micrometer resolution. To better understand how the reconstructed fiber orientations are related to the underlying fiber structure, numerical simulations are employed. Here, we present two complementary simulation approaches that reproduce the entire 3D-PLI analysis: First, we give a short review on a simulation approach that uses the Jones matrix calculus to model the birefringent myelin sheaths. Afterwards, we introduce a more sophisticated simulation tool: a 3D Maxwell solver based on a Finite-Difference Time-Domain algorithm that simulates the propagation of the electromagnetic light wave through the brain tissue. We demonstrate that the Maxwell solver is a valuable tool to better understand the interaction of polarized light with brain tissue and to enhance the accuracy of the fiber orientati...
Hawker, Morgan J; Pegalajar-Jurado, Adoracion; Fisher, Ellen R
2014-10-21
Bioresorbable polymers such as poly(ε-caprolactone) (PCL) have a multitude of potential biomaterial applications such as controlled-release drug delivery and regenerative tissue engineering. For such biological applications, the fabrication of porous three-dimensional bioresorbable materials with tunable surface chemistry is critical to maximize their surface-to-volume ratio, mimic the extracellular matrix, and increase drug-loading capacity. Here, two different fluorocarbon (FC) precursors (octofluoropropane (C3F8) and hexafluoropropylene oxide (HFPO)) were used to deposit FC films on PCL scaffolds using plasma-enhanced chemical vapor deposition (PECVD). These two coating systems were chosen with the intent of modifying the scaffold surfaces to be bio-nonreactive while maintaining desirable bulk properties of the scaffold. X-ray photoelectron spectroscopy showed high-CF2 content films were deposited on both the exterior and interior of PCL scaffolds and that deposition behavior is PECVD system specific. Scanning electron microscopy data confirmed that FC film deposition yielded conformal rather than blanket coatings as the porous scaffold structure was maintained after plasma treatment. Treated scaffolds seeded with human dermal fibroblasts (HDF) demonstrate that the cells do not attach after 72 h and that the scaffolds are noncytotoxic to HDF. This work demonstrates conformal FC coatings can be deposited on 3D polymeric scaffolds using PECVD to fabricate 3D bio-nonreactive materials.
Density distribution of a dust cloud in three-dimensional complex plasmas
Naumkin, V. N.; Zhukhovitskii, D. I.; Molotkov, V. I.; Lipaev, A. M.; Fortov, V. E.; Thomas, H. M.; Huber, P.; Morfill, G. E.
2016-09-01
We propose a method of determination of the dust particle spatial distribution in dust clouds that form in three-dimensional (3D) complex plasmas under microgravity conditions. The method utilizes the data obtained during the 3D scanning of a cloud, and it provides reasonably good accuracy. Based on this method, we investigate the particle density in a dust cloud realized in gas discharge plasma in the PK-3 Plus setup onboard the International Space Station. We find that the treated dust clouds are both anisotropic and inhomogeneous. One can isolate two regimes in which a stationary dust cloud can be observed. At low pressures, the particle density decreases monotonically with the increase of the distance from the discharge center; at higher pressures, the density distribution has a shallow minimum. Regardless of the regime, we detect a cusp of the distribution at the void boundary and a slowly varying density at larger distances (in the foot region). A theoretical interpretation of the obtained results is developed that leads to reasonable estimates of the densities for both the cusp and the foot. The modified ionization equation of state, which allows for violation of the local quasineutrality in the cusp region, predicts the spatial distributions of ion and electron densities to be measured in future experiments.
Density distribution of a dust cloud in three-dimensional complex plasmas
Naumkin, V N; Molotkov, V I; Lipaev, A M; Fortov, V E; Thomas, H M; Huber, P; Morfill, G E
2016-01-01
We propose a novel method of determination of the dust particle spatial distribution in dust clouds that form in three-dimensional (3D) complex plasmas under microgravity conditions. The method utilizes the data obtained during the 3D scanning of a cloud and provides a reasonably good accuracy. Based on this method, we investigate the particle density in a dust cloud realized in gas discharge plasma in the PK-3 Plus setup onboard the International Space Station. We find that the treated dust clouds are both anisotropic and inhomogeneous. One can isolate two regimes, in which a stationary dust cloud can be observed. At low pressures, the particle density decreases monotonically with the increase of the distance from the discharge center; at higher pressures, the density distribution has a shallow minimum. Regardless of the regime, we detect a cusp of the distribution at the void boundary and a slowly varying density at larger distances (in the foot region). A theoretical interpretation of obtained results is d...
Institute of Scientific and Technical Information of China (English)
JIN Yuzhen; LI Jun; ZHU Linhang; DU Jiayou; JIN Yingzi; LIN Peifeng
2014-01-01
For the large deformation of the flexible body may cause the fluid grid distortion,which will make the numerical calculation tedious,even to end,the numerical simulation of the flexible body coupling with the fluid is always a tough problem.In this paper,the flexible body is under two kinds of constrained conditions and the ratio of length-diameter is 1:30.The Reynolds number of the airflow is 513,belonging to the area of low Reynolds number.The control equations of the coupling of flexible body with airflow are built and the adaptive grid control method is adopted to conduct the three-dimensional numerical simulation of the movement of the flexible body.The numerical results show that it is possible to simulate the characteristics of the flexible body's movement in the low Reynolds number airflow when the appropriate control equations are modeled and suitable equation-solving method is adopted.Unconstrained flexible body would turn over forward along the airflow's diffusion direction,while constrained flexible body in the flow field will make periodic rotation motion along the axis of the flexible body,and the bending deformation is more obvious than that of unconstrained flexible body.The preliminary three-dimensional numerical simulation can provide references for further research on the characteristics of the yam movement in high Reynolds number airflow.
Three-Dimensional Viscous Numerical Simulation of Tip Clearance Flow in Axial-Flow Pump
Institute of Scientific and Technical Information of China (English)
Changming Yang; Cichang Chen; Jinnuo Wang; Quankai Ji
2003-01-01
The blade tip clearance flow in axial-flow pump is simulated based on three-dimensional N-S equations, RNG k-ε turbulence model, and SIMPLEC algorithm. It shows that numerical results agree well with experiment data measured by 5-hole probe through validation. Flow fields at the blade tip and velocity distribution at the exit of rotor are analyzed in detail. The numerical results show that the increase in tip clearance reduces hydro-head, especially at small flow rate. Experiment equipment is also introduced.
THREE-DIMENSIONAL NUMERICAL SIMULATION OF MULTIPLE JETS IN SHALLOW FLOWING RECEIVING WATERS
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
This paper is concerned with the simulation of the mixing mechanism of submerged multiport diffusers used to discharge heated water from thermal-electric power plants and households into shallow receiving waters. The three-dimensional turbulence model and hybrid finite analytic method are used to predict the behavior of near field for multiport buoyant jets in rivers. The predicted temperature dilution and velocity prove good by comparison with available laboratory measurements. An empirical formula for temperature dilution and velocity in near field for this kind of flow is given. The effect of parameters on the dilution behavior of multiple jets are also discussed.
Computer-assisted three-dimensional surgical planning and simulation: 3D virtual osteotomy.
Xia, J; Ip, H H; Samman, N; Wang, D; Kot, C S; Yeung, R W; Tideman, H
2000-02-01
A computer-assisted three-dimensional virtual osteotomy system for orthognathic surgery (CAVOS) is presented. The virtual reality workbench is used for surgical planning. The surgeon immerses in a virtual reality environment with stereo eyewear, holds a virtual "scalpel" (3D Mouse) and operates on a "real" patient (3D visualization) to obtain pre-surgical prediction (3D bony segment movements). Virtual surgery on a computer-generated 3D head model is simulated and can be visualized from any arbitrary viewing point in a personal computer system.
Three Dimensional Numerical Simulation for the Driving Force of Weld Solidification Cracking
Institute of Scientific and Technical Information of China (English)
Zhibo DONG; Yanhong WEI; Renpei LIU; Zujue DONG
2005-01-01
The double ellipsoidal model of heat source is used to analyze the thermal distributions with a three dimensional finite element method (FEM). In the mechanical model, solidification effects are treated by a dynamic element rebirth scheme. The driving force is obtained in the cracking susceptible temperature range. Moreover, this paper presents the effect of solidification shrinkage, external restraint, weld start locations and material properties on the driving force. The comparison between the simulated driving force and the experimental measurements of the material resistance predicts the susceptibility of weld metal solidification cracking.
High energy gain in three-dimensional simulations of light sail acceleration
Energy Technology Data Exchange (ETDEWEB)
Sgattoni, A., E-mail: andrea.sgattoni@polimi.it [Dipartimento di Energia, Politecnico di Milano, Milano (Italy); CNR, Istituto Nazionale di Ottica, u.o.s. “Adriano Gozzini,” Pisa (Italy); Sinigardi, S. [CNR, Istituto Nazionale di Ottica, u.o.s. “Adriano Gozzini,” Pisa (Italy); Dipartimento di Fisica e Astronomia, Università di Bologna, Bologna (Italy); INFN sezione di Bologna, Bologna (Italy); Macchi, A. [CNR, Istituto Nazionale di Ottica, u.o.s. “Adriano Gozzini,” Pisa (Italy); Dipartimento di Fisica “Enrico Fermi,” Università di Pisa, Pisa (Italy)
2014-08-25
The dynamics of radiation pressure acceleration in the relativistic light sail regime are analysed by means of large scale, three-dimensional (3D) particle-in-cell simulations. Differently to other mechanisms, the 3D dynamics leads to faster and higher energy gain than in 1D or 2D geometry. This effect is caused by the local decrease of the target density due to transverse expansion leading to a “lighter sail.” However, the rarefaction of the target leads to an earlier transition to transparency limiting the energy gain. A transverse instability leads to a structured and inhomogeneous ion distribution.
Burgess, David; Gingell, Peter W; Trávníček, Pavel M
2016-01-01
Supercritical collisionless perpendicular shocks have an average macrostructure determined primarily by the dynamics of ions specularly reflected at the magnetic ramp. Within the overall macrostructure, instabilities, both linear and nonlinear, generate fluctuations and microstructure. To identify the sources of such microstructure, high-resolution two- and three-dimensional simulations have been carried out using the hybrid method, wherein the ions are treated as particles and the electron response is modelled as a massless fluid. We confirm the results of earlier 2-D simulations showing both field-parallel aligned propagating fluctuations and fluctuations carried by the reflected-gyrating ions. In addition, it is shown that, for 2-D simulations of the shock coplanarity plane, the presence of short-wavelength fluctuations in all magnetic components is associated with the ion Weibel instability driven at the upstream edge of the foot by the reflected-gyrating ions. In 3-D simulations we show for the first tim...
Three-Dimensional Simulations of the Convective Urca Process in Pre-Supernova White Dwarfs
Willcox, Donald E.; Townsley, Dean; Zingale, Michael; Calder, Alan
2017-01-01
A significant source of uncertainty in modeling the progenitor systems of Type Ia supernovae is the dynamics of the convective Urca process in which beta decay and electron capture reactions remove energy from and decrease the buoyancy of carbon-fueled convection in the progenitor white dwarf. The details of the Urca process during this simmering phase have long remained computationally intractable in three-dimensional simulations because of the very low convective velocities and the associated timestep constraints of compressible hydrodynamics methods. We report on recent work simulating the A=23 (Ne/Na) Urca process in convecting white dwarfs in three dimensions using the low-Mach hydrodynamics code MAESTRO. We simulate white dwarf models inspired by one-dimensional stellar evolution calculations at the stage when the outer edge of the convection zone driven by core carbon burning reaches the A=23 Urca shell. We compare our methods and results to those of previous work in one and two dimensions, discussing the implications of three dimensional turbulence. We also comment on the prospect of our results informing one-dimensional stellar evolution calculations and the Type Ia supernovae progenitor problem.This work was supported in part by the Department of Energy under grant DE-FG02-87ER40317.
Evaluation of the three-dimensional clinostat as a simulator of weightlessness.
Hoson, T; Kamisaka, S; Masuda, Y; Yamashita, M; Buchen, B
1997-01-01
Concerns regarding the reliability of slow-and fast-rotating uni-axial clinostats in simulating weightlessness have induced the construction of devices considered to simulate weightlessness more adequately. A new three-dimensional (3-D) clinostat equipped with two rotation axes placed at right angles has been constructed. In the clinostat, the rotation achieved with two motors is computer-controlled and monitored with encoders attached to the motors. By rotating plants three-dimensionally at random rates on the clinostat, their dynamic stimulation by gravity in every direction can be eliminated. Some of the vegetative growth phases of plants dependent on the gravity vector, such as morphogenesis, are shown to be influenced by rotation on the 3-D clinostat. The validity of 3-D clinostatting has been evaluated by comparing structural parameters of cress roots and Chara rhizoids obtained under real microgravity with those obtained after 3-D clinostatting. The parameters analyzed up to now (organization of the root cap, integrity and polarity of statocytes, dislocation of statoliths, amount of starch and ER) demonstrate that the 3-D clinostat is a valuable device for simulating weightlessness.
Institute of Scientific and Technical Information of China (English)
LUO Zu-jiang; ZHANG Ying-ying; WU Yong-xia
2008-01-01
For deep foundation pit dewatering in the Yangtze River Delta, it is easy to make a dramatic decrease of the underground water level surrounding the dewatering area and cause land subsidence and geologic disasters. In this work, a three-dimensional finite element simulation method was applied in the forth subway of Dongjiadu tunnel repair foundation pit dewatering in Shanghai. In order to control the decrease of the underground water level around the foundation pit, the foundation pit dewatering method was used to design the optimization project of dewatering ,which was simulated under these conditions that the aquifers deposited layer by layer, the bottom of the aquifers went deep to 144.45 m, the retaining wall of foundation pit shield went deep to 65 m, the filters of the extraction wells were located between 44 m to 59 m, the water level in the deep foundation pit was decreased by 34 m, and the maximum decrease of water level outside the foundation pit was 3 m. It is shown that the optimization project and the practical case are consistent with each other. Accordingly, the three-dimensional finite element numerical simulation is the basic theory of optimization design of engineering structures of dewatering in deep foundation pit in such areas.
Effect of magnetic field on the wave dispersion relation in three-dimensional dusty plasma crystals
Energy Technology Data Exchange (ETDEWEB)
Yang Xuefeng [School of Mathematical Sciences, Dalian University of Technology, Dalian 116024 (China); Wang Zhengxiong [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China)
2012-07-15
Three-dimensional plasma crystals under microgravity condition are investigated by taking into account an external magnetic field. The wave dispersion relations of dust lattice modes in the body centered cubic (bcc) and the face centered cubic (fcc) plasma crystals are obtained explicitly when the magnetic field is perpendicular to the wave motion. The wave dispersion relations of dust lattice modes in the bcc and fcc plasma crystals are calculated numerically when the magnetic field is in an arbitrary direction. The numerical results show that one longitudinal mode and two transverse modes are coupled due to the Lorentz force in the magnetic field. Moreover, three wave modes, i.e., the high frequency phonon mode, the low frequency phonon mode, and the optical mode, are obtained. The optical mode and at least one phonon mode are hybrid modes. When the magnetic field is neither parallel nor perpendicular to the primitive wave motion, all the three wave modes are hybrid modes and do not have any intersection points. It is also found that with increasing the magnetic field strength, the frequency of the optical mode increases and has a cutoff at the cyclotron frequency of the dust particles in the limit of long wavelength, and the mode mixings for both the optical mode and the high frequency phonon mode increase. The acoustic velocity of the low frequency phonon mode is zero. In addition, the acoustic velocity of the high frequency phonon mode depends on the angle of the magnetic field and the wave motion but does not depend on the magnetic field strength.
Three-Dimensional Molecular Dynamics Simulation on Heat Propagation in Liquid Argon
Institute of Scientific and Technical Information of China (English)
郭英奎; 过增元; 梁新刚
2001-01-01
The propagation behaviour of an initial thermal perturbation in liquid argon is simulated by the molecular dynamics method. The 12-6 Lennard-Jones potential and mirror boundary conditions are employed in the 32768particle three-dimensional simulation. Macroscopic characteristics such as the kinetic temperature, pressure and momentum profiles are monitored during the simulation in order to examine the heat propagation behaviour under a timescale comparable with the relaxation time. The results show that the behaviour is still diffusionlike; no features predicted by the Cattaneo-Vernotte model have been found. The wave-like front of the local temperature may be caused by the adiabatic compression and expansion by the pressure wave generated by the thermal expansion.
THREE-DIMENSIONAL NUMERICAL SIMULATION OF INTAKE MODEL WITH CROSS FLOW
Institute of Scientific and Technical Information of China (English)
CHUANG Wei-Liang; HSIAO Shih-Chun
2011-01-01
The hydrodynamics of a pump sump consisting of a main channel, pump sump, and intake pipe is examined using Truchas,a three-dimensional Navier-Stokes solver, with a Large Eddy Simulation (LES) turbulence model. The numerical results of streamwise velocity profiles and flow patterns are discussed and compared with experimental data of Ansar and Nakato. Fairly good agreement is obtained. Furthermore, unlike Ansar et al.'s inviscid solution, the proposed numerical model includes the effect of fluid viscosity and considers more realistic simulation conditions. Simulation results show that viscosity affects the prediction of flow patterns and that the streamwise velocity can be better captured by including cross flow. The effects of the submergence Froude number on the free surface and streamwise velocity are also examined. The free surface significantly fluctuates at high submergence Froude number flows and the corresponding distribution of streamwise velocity profiles exhibits a trend different from that obtained for low submergence Froude number flows.
Bingham, Jill; Hinders, Mark
2009-07-01
The development of automatic guided wave interpretation for detecting corrosion in aluminum aircraft structural stringers is described. The dynamic wavelet fingerprint technique (DWFT) is used to render the guided wave mode information in two-dimensional binary images. Automatic algorithms then extract DWFT features that correspond to the distorted arrival times of the guided wave modes of interest, which give insight into changes of the structure in the propagation path. To better understand how the guided wave modes propagate through real structures, parallel-processing elastic wave simulations using the finite integration technique (EFIT) has been performed. Three-dimensional (3D) simulations are used to examine models too complex for analytical solutions. They produce informative visualizations of the guided wave modes in the structures and mimic the output from sensors placed in the simulation space. Using the previously developed mode extraction algorithms, the 3D EFIT results are compared directly to their experimental counterparts.
Three-dimensional Magnetohydrodynamic Simulations of Buoyant Bubbles in Galaxy Clusters
O'Neill, S M; Jones, T W
2009-01-01
We report results of 3D MHD simulations of the dynamics of buoyant bubbles in magnetized galaxy cluster media. The simulations are three dimensional extensions of two dimensional calculations reported by Jones & De Young (2005). Initially spherical bubbles and briefly inflated spherical bubbles all with radii a few times smaller than the intracluster medium (ICM) scale height were followed as they rose through several ICM scale heights. Such bubbles quickly evolve into a toroidal form that, in the absence of magnetic influences, is stable against fragmentation in our simulations. This ring formation results from (commonly used) initial conditions that cause ICM material below the bubbles to drive upwards through the bubble, creating a vortex ring; that is, hydrostatic bubbles develop into "smoke rings", if they are initially not very much smaller or very much larger than the ICM scale height. Even modest ICM magnetic fields with beta = P_gas/P_mag ~ 10^3 can influence the dynamics of the bubbles, provided...
Abe, Makito; Umemura, Masayuki; Hasegawa, Kenji
2016-12-01
We explore the possibility of the formation of globular clusters (GCs) under ultraviolet (UV) background radiation. One-dimensional spherical symmetric radiation hydrodynamics (RHD) simulations by Hasegawa et al. have demonstrated that the collapse of low-mass (106-7 M⊙) gas clouds exposed to intense UV radiation can lead to the formation of compact star clusters like GCs if gas clouds contract with supersonic infall velocities. However, three-dimensional effects, such as the anisotropy of background radiation and the inhomogeneity in gas clouds, have not been studied so far. In this paper, we perform three-dimensional RHD simulations in a semicosmological context, and reconsider the formation of compact star clusters in strong UV radiation fields. As a result, we find that although anisotropic radiation fields bring an elongated shadow of neutral gas, almost spherical compact star clusters can be procreated from a `supersonic infall' cloud, since photodissociating radiation suppresses the formation of hydrogen molecules in the shadowed regions and the regions are compressed by UV heated ambient gas. The properties of resultant star clusters match those of GCs. On the other hand, in weak UV radiation fields, dark-matter-dominated star clusters with low stellar density form due to the self-shielding effect as well as the positive feedback by ionizing photons. Thus, we conclude that the `supersonic infall' under a strong UV background is a potential mechanism to form GCs.
Virtual reality simulation: using three-dimensional technology to teach nursing students.
Jenson, Carole E; Forsyth, Diane McNally
2012-06-01
The use of computerized technology is rapidly growing in the classroom and in healthcare. An emerging computer technology strategy for nursing education is the use of virtual reality simulation. This computer-based three-dimensional educational tool simulates real-life patient experiences in a risk-free environment, allows for repeated practice sessions, requires clinical decision making, exposes students to diverse patient conditions, provides immediate feedback, and is portable. The purpose of this article was to review the importance of virtual reality simulation as a computerized teaching strategy. In addition, a project to explore readiness of nursing faculty at one major Midwestern university for the use of virtual reality simulation as a computerized teaching strategy is described where faculty thought virtual reality simulation would increase students' knowledge of an intravenous line insertion procedure. Faculty who practiced intravenous catheter insertion via virtual reality simulation expressed a wide range of learning experiences from using virtual reality simulation that is congruent with the literature regarding the barriers to student learning. Innovative teaching strategies, such as virtual reality simulation, address barriers of increasing patient acuity, high student-to-faculty ratio, patient safety concerns from faculty, and student anxiety and can offer rapid feedback to students.
Endeve, Eirik; Cardall, C.; Budiardja, R.; Beck, S.; Bejnood, A.; Mezzacappa, A.
2011-01-01
The stationary accretion shock instability (SASI) plays an important role in modern simulations of core-collapse supernovae. With the intent to study magnetic field generation and the possible impact of magnetic fields during the crucial nonlinear phase leading to the explosion of massive stars, we have carried out high-resolution, three-dimensional magnetohydrodynamic simulations of the SASI. Turbulent flows emerging from the operation of the spiral SASI mode result in exponential growth of the magnetic energy. From initial conditions in the range expected for slowly rotating progenitor stars, we find that saturation of the magnetic energy can occur within a typical explosion time scale. Implications for neutrino-powered supernovae and neutron star magnetization are considered.
Institute of Scientific and Technical Information of China (English)
郑金海; 严以新; 诸裕良
2002-01-01
For simulating fresh and salt water mixing in estuaries, a three dimensional nonlinear baroclinic numerical model isdeveloped, in which the gradients of horizontal pressure contain the gradient of barotropic pressure arising from the gradi-ent of tidal level and the gradient of baroclinic pressure due to the gradient of salinity. The Eulerian-Lagrangian method isemployed to descretize both the momentum equations of tidal motion and the equation of salt water diffusion so as to im-prove the computational stability and accuracy. The methods to provide the boundary conditions and the initial conditionsare proposed, and the criterion for computational stability of the salinity fields is presented. The present model is used formodeling fresh and salt water mixing in the Yangtze Estuary. Computations show that the salinity distribution has thecharacteristics of partial mixing pattern, and that the present model is suitable for simulation of fresh and salt water mixing in the Yangtze Estuary.
Kudoh, Takahiro; Ogata, Youichi; Yabe, Takashi
2007-01-01
We employ the first fully three-dimensional simulation to study the role of magnetic fields and ion-neutral friction in regulating gravitationally-driven fragmentation of molecular clouds. The cores in an initially subcritical cloud develop gradually over an ambipolar diffusion time while the cores in an initially supercritical cloud develop in a dynamical time. The infall speeds on to cores are subsonic in the case of an initially subcritical cloud, while an extended (\\ga 0.1 pc) region of supersonic infall exists in the case of an initially supercritical cloud. These results are consistent with previous two-dimensional simulations. We also found that a snapshot of the relation between density (rho) and the strength of the magnetic field (B) at different spatial points of the cloud coincides with the evolutionary track of an individual core. When the density becomes large, both relations tend to B \\propto \\rho^{0.5}.
Synergies between Asteroseismology and Three-dimensional Simulations of Stellar Turbulence
Arnett, W. David; Moravveji, E.
2017-02-01
Turbulent mixing of chemical elements by convection has fundamental effects on the evolution of stars. The standard algorithm at present, mixing-length theory (MLT), is intrinsically local, and must be supplemented by extensions with adjustable parameters. As a step toward reducing this arbitrariness, we compare asteroseismically inferred internal structures of two Kepler slowly pulsating B stars (SPBs; M∼ 3.25{M}ȯ ) to predictions of 321D turbulence theory, based upon well-resolved, truly turbulent three-dimensional simulations that include boundary physics absent from MLT. We find promising agreement between the steepness and shapes of the theoretically predicted composition profile outside the convective region in 3D simulations and in asteroseismically constrained composition profiles in the best 1D models of the two SPBs. The structure and motion of the boundary layer, and the generation of waves, are discussed.
Large Eddy Simulations of Three-Dimensional Flows Around a Spur Dike
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
Large eddy simulations were used to model the three-dimensional flows around a non-submerged spur dike. Based on the rigid lid assumption, all these vortex flows around the spur dike, which probably affected the whole flow field, were numerically simulated and analyzed. The largest circulating flow region caused by the spur dike behind it was weak, which would naturally lead to sedimentation for silt-laden two-phase flows. Based on the Smagorinsky model, the finite volume method was used to discretize the Navier-Stokes equations, and the SIMPLEC algorithm was used to solve them. Meanwhile, these flows were investigated experimentally in a 0.5-m wide flume with a dike placed as a barrier. The computational results are in a fairly good agreement with the experimental data.
Three-dimensional finite-element simulation of a turbulent push-pull ventilation system.
Flynn, M R; Ahn, K; Miller, C T
1995-10-01
A finite-element formulation with penalty approach to enforce continuity is employed here to simulate the three-dimensional velocity field resulting from a simple push-pull ventilation configuration. An analytic expression for the length scale and a transport equation for turbulent kinetic energy are coupled with the momentum equations. A coaxial square hood and jet are arranged with cross-draught perpendicular to the common centreline. Numerical predictions of the velocity and turbulence kinetic energy fields are evaluated in the plane of symmetry with hot film anemometry, and smoke-wire flow visualizations. The agreement of the simulated jet trajectories with flow visualizations is reasonable, as are velocities. Predictions of turbulence kinetic energy are not as good, particularly near the hood face. Despite the limitations the numerical approach is useful in assessing the impact of cross-draughts on the push-pull arrangement.
Three-dimensional point-cloud room model in room acoustics simulations
DEFF Research Database (Denmark)
Markovic, Milos; Olesen, Søren Krarup; Hammershøi, Dorte
2013-01-01
and rotated around the vertical axis while for the second one the device is moved within the room. Benefits of both approaches were analyzed. The device's depth sensor provides a set of points in a three-dimensional coordinate system which represents scanned surfaces of the room interior. These data are used...... to build a 3D point-cloud model of the room. Several models are created to meet requirements of different room acoustics simulation algorithms: plane fitting and uniform voxel grid for geometric methods and triangulation mesh for the numerical methods. Advantages of the proposed method over the traditional...... acquisition and its representation with a 3D point-cloud model, as well as utilization of such a model for the room acoustics simulations. A room is scanned with a commercially available input device (Kinect for Xbox360) in two different ways; the first one involves the device placed in the middle of the room...
Three-dimensional point-cloud room model for room acoustics simulations
DEFF Research Database (Denmark)
Markovic, Milos; Olesen, Søren Krarup; Hammershøi, Dorte
2013-01-01
and rotated around the vertical axis while for the second one the device is moved within the room. Benefits of both approaches were analyzed. The device's depth sensor provides a set of points in a three-dimensional coordinate system which represents scanned surfaces of the room interior. These data are used...... to build a 3D point-cloud model of the room. Several models are created to meet requirements of different room acoustics simulation algorithms: plane fitting and uniform voxel grid for geometric methods and triangulation mesh for the numerical methods. Advantages of the proposed method over the traditional...... acquisition and its representation with a 3D point-cloud model, as well as utilization of such a model for the room acoustics simulations. A room is scanned with a commercially available input device (Kinect for Xbox360) in two different ways; the first one involves the device placed in the middle of the room...
Energy Technology Data Exchange (ETDEWEB)
Yamada, T.
1978-01-01
Cooling ponds receive large amounts of waste heat from industrial sources and release the heat to the atmosphere. These large area sources of warm and moist air may have significant inadvertent effects. This paper is a preliminary step in the development of a method for estimating the perturbations in the atmosphere produced by a cooling pond. A three-dimensional numerical model based on turbulence second-moment closure equations and Gaussian cloud relations has been developed. A simplified version of the model, in which only turbulent energy and length-scale equations are solved prognostically, is used. Numerical simulations are conducted using as boundary conditions the data from a cooling pond study conducted in northern Illinois during the winter of 1976-1977. Preliminary analyses of these simulations indicate that formation of clouds over a cooling pond is sensitive to the moisture content in the ambient atmosphere.
Three-dimensional simulation of equatorial spread-F with meridional wind effects
Directory of Open Access Journals (Sweden)
J. Krall
2009-05-01
Full Text Available The NRL SAMI3 three-dimensional simulation code is used to examine the effect of meridional winds on the growth and suppression of equatorial spread F (ESF. The simulation geometry conforms to a dipole field geometry with field-line apex heights from 200 to 1600 km at the equator, but extends over only 4 degrees in longitude. The full SAMI3 ionosphere equations are included, providing ion dynamics both along and across the field. The potential is solved in two dimensions in the equatorial plane under a field-line equipotential approximation. By selectively including terms in the potential equation, the reduced growth predicted by Maruyama (1988 and the stabilization predicted by Zalesak and Huba (1991 are separately realized. We find that ESF is stabilized by a sufficiently large constant meridional wind (60 m/s in our example.
Direct Numerical Simulation of Three-Dimensional Richtmyer-Meshkov Instability
Institute of Scientific and Technical Information of China (English)
FU De-Xun; MA Yan-Wen; LI Xin-Liang
2008-01-01
Direct numerical simulation(DNS)is used to study flow characteristics after interaction of a planar shock with a spherical media interface in each side of which the density is different.This interfacial instability is known as the Richtmyer-Meshkov(R-M)instability.The compressible Nayier-Stoke equations are discretized with group velocity control(GVC)modified fourth order accurate compact difference scheme.Three-dimensional numerical simulations are performed for R-M instability installed passing a shock through a spherical interface.Based on numerical results the characteristics of 3D R-M instability are analysed.The evaluation for distortion of the interface.the deformation of the incident shock wave and effects of refraction,reflection and diffraction are Dresented.The effects of the interfacial instability on produced vorticity and mixing is discussed.
Simulating three-dimensional hydrodynamics on a cellular-automata machine
Adler, C; Margolus, N H; Rothman, D H; Adler, Christopher; Boghosian, Bruce M; Margolus, Norman; Rothman, Daniel H
1995-01-01
We demonstrate how three-dimensional fluid flow simulations can be carried out on the Cellular Automata Machine 8 (CAM-8), a special-purpose computer for cellular-automata computations. The principal algorithmic innovation is the use of a lattice-gas model with a 16-bit collision operator that is specially adapted to the machine architecture. It is shown how the collision rules can be optimized to obtain a low viscosity of the fluid. Predictions of the viscosity based on a Boltzmann approximation agree well with measurements of the viscosity made on CAM-8. Several test simulations of flows in simple geometries -- channels, pipes, and a cubic array of spheres -- are carried out. Measurements of average flux in these geometries compare well with theoretical predictions.
Three dimensional full-wave nonlinear acoustic simulations: Applications to ultrasound imaging
Energy Technology Data Exchange (ETDEWEB)
Pinton, Gianmarco [Joint Department of Biomedical Engineering, University of North Carolina - North Carolina State University, 348 Taylor Hall, Chapel Hill, NC 27599, USA gfp@unc.edu (United States)
2015-10-28
Characterization of acoustic waves that propagate nonlinearly in an inhomogeneous medium has significant applications to diagnostic and therapeutic ultrasound. The generation of an ultrasound image of human tissue is based on the complex physics of acoustic wave propagation: diffraction, reflection, scattering, frequency dependent attenuation, and nonlinearity. The nonlinearity of wave propagation is used to the advantage of diagnostic scanners that use the harmonic components of the ultrasonic signal to improve the resolution and penetration of clinical scanners. One approach to simulating ultrasound images is to make approximations that can reduce the physics to systems that have a low computational cost. Here a maximalist approach is taken and the full three dimensional wave physics is simulated with finite differences. This paper demonstrates how finite difference simulations for the nonlinear acoustic wave equation can be used to generate physically realistic two and three dimensional ultrasound images anywhere in the body. A specific intercostal liver imaging scenario for two cases: with the ribs in place, and with the ribs removed. This configuration provides an imaging scenario that cannot be performed in vivo but that can test the influence of the ribs on image quality. Several imaging properties are studied, in particular the beamplots, the spatial coherence at the transducer surface, the distributed phase aberration, and the lesion detectability for imaging at the fundamental and harmonic frequencies. The results indicate, counterintuitively, that at the fundamental frequency the beamplot improves due to the apodization effect of the ribs but at the same time there is more degradation from reverberation clutter. At the harmonic frequency there is significantly less improvement in the beamplot and also significantly less degradation from reverberation. It is shown that even though simulating the full propagation physics is computationally challenging it
Three Dimensional Simulation of the Steady Solar Wind in Carrington Rotation 1935
Institute of Scientific and Technical Information of China (English)
XIANG Changqing; FENG Xueshang; YAO Jiusheng
2006-01-01
A three-dimensional MHD simulation is conducted to study the steady solar wind in Carrington Rotation (CR) 1935 by using the three-dimensional numerical magnetohydrodynamic (MHD) model introduced by Feng et al. The numerical results demonstrate that the neutral current sheet has two peaks and two valleys, which is consistent with the result of PFSS model at Wilcox Solar Observatory (WSO). The obtained proton number density at 2.5 Rs is of the same order of magnitude as the result estimated from K-coronal brightness during the CRs 1733-1742 in 1983made by Wei et al. The radial velocity profile along heliocentric distance is consistent with that of low solar wind speed deduced by Sheeley and Wang et al. However, it is not able to reproduce the fast-speed flow in coronal holes and slow solar wind in streamers because of oversimplified energy equation adopted in our model. Future efforts must be made to remedy this deficiency.
Three-Dimensional Simulations of the Deceleration Phase of Inertial Fusion Implosions
Woo, K. M.; Betti, R.; Bose, A.; Epstein, R.; Delettrez, J. A.; Anderson, K. S.; Yan, R.; Chang, P.-Y.; Jonathan, D.; Charissis, M.
2015-11-01
The three-dimensional radiation-hydrodynamics code DEC3D has been developed to model the deceleration phase of direct-drive inertial confinement fusion implosions. The code uses the approximate Riemann solver on a moving mesh to achieve high resolution near discontinuities. The domain decomposition parallelization strategy is implemented to maintain high computation efficiency for the 3-D calculation through message passing interface. The implicit thermal diffusion is solved by the parallel successive-over-relaxation iteration. Results from 3-D simulations of low-mode Rayleigh-Taylor instability are presented and compared with 2-D results. A systematic comparison of yields, pressures, temperatures, and areal densities between 2-D and 3-D is carried out to determine the additional degradation in target performance caused by the three-dimensionality of the nonuniformities. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and DE-FC02-04ER54789 (Fusion Science Center).
Three dimensional neutronic/thermal-hydraulic coupled simulation of MSR in steady state condition
Energy Technology Data Exchange (ETDEWEB)
Zhou, Jianjun; Wang, Chenglong [School of Nuclear Science and Technology, Xi’an Jiaotong University, Xi’an, Shaanxi 710049 (China); An, Hongzhen [Nuclear and Radiation Safety Center, Ministry of Environmental Protection of the People' s Republic of China, Beijing 100082 (China); Zhang, Daling, E-mail: dlzhang@mail.xjtu.edu.cn [School of Nuclear Science and Technology, Xi’an Jiaotong University, Xi’an, Shaanxi 710049 (China); Qiu, Suizheng; Su, Guanghui; Tian, Wenxi; Wu, Yingwei [School of Nuclear Science and Technology, Xi’an Jiaotong University, Xi’an, Shaanxi 710049 (China)
2014-02-15
Highlights: • Developed a three dimensional coupled code for MSR. • Investigated the neutron distribution and thermal-hydraulic characters of the core under steady state condition. • Analyzed the influence of inlet temperature and inlet velocity to thermal-hydraulics characteristics of the reactor. - Abstract: MSR (molten salt reactor) uses liquid molten salt as the coolant and fuel solvent, making it the only liquid reactor among the six generation IV reactor types. As a liquid reactor the physical properties of the reactor are significantly influenced by the fuel salt flow therefore conventional analysis methods applied in solid fuel reactors are not applicable for this type of reactors. The present work developed a three dimensional neutronic/thermal-hydraulic coupled code and applied it to investigate the thermal-hydraulic characteristics of the core in steady state condition based on neutron diffusion theory and numerical heat transfer. The code consists of two group neutron diffusion equations for fast and thermal neutron fluxes and six group balance equations for delayed neutron precursors. The temperature distribution, neutron fluxes and delayed neutron precursors distribution of the core in steady state conditions was studied, and the result analyzed when inlet temperature and velocity were changed. From simulation it was found that the inlet temperature has little influence to neutron distribution however inlet velocity affects the delayed neutron distribution in steady state condition. The results provide some valuable information in design and research of this kind of reactor.
Prévost, Jean H.; Sukumar, N.
2016-01-01
Faults are geological entities with thicknesses several orders of magnitude smaller than the grid blocks typically used to discretize reservoir and/or over-under-burden geological formations. Introducing faults in a complex reservoir and/or geomechanical mesh therefore poses significant meshing difficulties. In this paper, we consider the strong-coupling of solid displacement and fluid pressure in a three-dimensional poro-mechanical (reservoir-geomechanical) model. We introduce faults in the mesh without meshing them explicitly, by using the extended finite element method (X-FEM) in which the nodes whose basis function support intersects the fault are enriched within the framework of partition of unity. For the geomechanics, the fault is treated as an internal displacement discontinuity that allows slipping to occur using a Mohr-Coulomb type criterion. For the reservoir, the fault is either an internal fluid flow conduit that allows fluid flow in the fault as well as to enter/leave the fault or is a barrier to flow (sealing fault). For internal fluid flow conduits, the continuous fluid pressure approximation admits a discontinuity in its normal derivative across the fault, whereas for an impermeable fault, the pressure approximation is discontinuous across the fault. Equal-order displacement and pressure approximations are used. Two- and three-dimensional benchmark computations are presented to verify the accuracy of the approach, and simulations are presented that reveal the influence of the rate of loading on the activation of faults.
Experiment and simulation study on construction of a three-dimensional network model
Institute of Scientific and Technical Information of China (English)
2008-01-01
The construction of a network model is one of the key techniques in organic com-bination of microscopic flow experiment and simulation. The construction method of a three-dimensional network model is presented on the basis of CT scanning images in this paper. A series of CT slice images describing microscopic pore structure and fluid distribution of actual rock is obtained with the help of the in-dustrial microfocus CT system. Based on the extraction of pore space skeleton, pore and throat information, the corresponding network model is established, and the conversion from three-dimensional CT image information to pore-throat size distribution and topological information is also achieved. The feature of this me-thod lies in the fact that complicated pore space of rock may be characterized by pores and throats with a simple shape while keeping the geometry and flow char-acteristics. It is indicated that the calculated results of porosity, permeability, rela-tive permeability curve and microscopic remaining oil distribution match very well the experimental results of water flooding and polymer flooding. This network model may fairly well characterize the rock microscopic pore-throat size and topo-logical characteristics.
Riaz, A.; Meiburg, E.
2003-11-01
High-accuracy three-dimensional numerical simulations of miscible displacements with gravity override in homogeneous porous media are carried out for the quarter five-spot configuration. Special emphasis is placed on describing the influence of viscous and gravitational effects on the overall displacement dynamics in terms of the vorticity variable. Even for neutrally buoyant displacements, three-dimensional effects are seen to change the character of the flow significantly, in contrast to earlier findings for rectilinear displacements. At least in part this can be attributed to the time dependence of the most dangerous vertical instability mode. Density differences influence the flow primarily by establishing a narrow gravity layer, in which the effective Péclet number is enhanced owing to the higher flow rate. However, buoyancy forces of a certain magnitude can lead to a pinch-off of the gravity layer, thereby slowing it down. Overall, an increase of the gravitational parameter is found to enhance mostly the vertical perturbations, while larger Pe values act towards amplifying horizontal disturbances. The asymptotic rate of growth of the mixing length varies only with Péclet number. For large Péclet numbers, an asymptotic value of 0.7 is observed. A scaling law for the thickness of the gravity layer is obtained as well. In contrast to immiscible flow displacements, it is found to increase with the gravity parameter.
Energy release and transfer in solar flares: simulations of three-dimensional reconnection
Energy Technology Data Exchange (ETDEWEB)
Birn, Joachim [Los Alamos National Laboratory; Fletches, L [UNIV OF GLASGOW; Hesse, M [HGSFC; Neukirch, T [UNIV OF ST. ANDREWS
2008-01-01
Using three-dimensional magnetohydrodynamic (MHD) simulations we investigate energy release and transfer in a three-dimensional extension of the standard two-ribbon flare picture. In this scenario reconnection is initiated in a thin current sheet (suggested to form below a departing coronal mass ejection) above a bipolar magnetic field. Two cases are contrasted: an initially force-free current sheet (low beta) and a finite-pressure current sheet (high beta). The energy conversion process from reconnect ion consists of incoming Poynting flux (from the release of magnetic energy) turned into up-and downgoing Poynting flux, enthalpy flux and bulk kinetic energy flux. In the low-beta case, the outgoing Poynting flux is the dominant contribution, whereas the outgoing enthalpy flux dominates in the high-beta case. The bulk kinetic energy flux is only a minor contribution, particularly in the downward direction. The dominance of the downgoing Poynting flux in the low-beta case is consistent with an alternative to the thick target electron beam model for solar flare energy transport, suggested recently by Fletcher and Hudson. For plausible characteristic parameters of the reconnecting field configuration, we obtain energy release time scales and and energy output rates that compare favorably with those inferred from observations for the impulsive phase of flares.
Ham, C J; Kirk, A; Saarelma, S
2013-01-01
It is known that magnetic perturbations can mitigate edge localized modes (ELMs) in experiments, for example MAST (Kirk et al 2013 Nucl. Fusion 53 043007). One hypothesis is that the magnetic perturbations cause a three dimensional corrugation of the plasma and this corrugated plasma has different stability properties to peeling-ballooning modes compared to an axisymmetric plasma. It has been shown in an up-down symmetric plasma that magnetic perturbations in tokamaks will break the usual axisymmetry of the plasma causing three dimensional displacements (Chapman et al 2012 Plasma Phys. Control. Fusion 54 105013). We produce a free boundary three-dimensional equilibrium of a lower single null MAST relevant plasma using VMEC (S P Hirshman and J C Whitson 1983 Phys. Fluids 26 3553). The current and pressure profiles used for the modelling are similar to those deduced from axisymmetric analysis of experimental data with ELMs. We focus on the effect of applying $n=3$ and $n=6$ magnetic perturbations using the RMP ...
Parallel Simulation of Three-Dimensional Free Surface Fluid Flow Problems
Energy Technology Data Exchange (ETDEWEB)
BAER,THOMAS A.; SACKINGER,PHILIP A.; SUBIA,SAMUEL R.
1999-10-14
Simulation of viscous three-dimensional fluid flow typically involves a large number of unknowns. When free surfaces are included, the number of unknowns increases dramatically. Consequently, this class of problem is an obvious application of parallel high performance computing. We describe parallel computation of viscous, incompressible, free surface, Newtonian fluid flow problems that include dynamic contact fines. The Galerkin finite element method was used to discretize the fully-coupled governing conservation equations and a ''pseudo-solid'' mesh mapping approach was used to determine the shape of the free surface. In this approach, the finite element mesh is allowed to deform to satisfy quasi-static solid mechanics equations subject to geometric or kinematic constraints on the boundaries. As a result, nodal displacements must be included in the set of unknowns. Other issues discussed are the proper constraints appearing along the dynamic contact line in three dimensions. Issues affecting efficient parallel simulations include problem decomposition to equally distribute computational work among a SPMD computer and determination of robust, scalable preconditioners for the distributed matrix systems that must be solved. Solution continuation strategies important for serial simulations have an enhanced relevance in a parallel coquting environment due to the difficulty of solving large scale systems. Parallel computations will be demonstrated on an example taken from the coating flow industry: flow in the vicinity of a slot coater edge. This is a three dimensional free surface problem possessing a contact line that advances at the web speed in one region but transitions to static behavior in another region. As such, a significant fraction of the computational time is devoted to processing boundary data. Discussion focuses on parallel speed ups for fixed problem size, a class of problems of immediate practical importance.
Three Dimensional Large Eddy Simulation Model of Turbulence in a Meandering Channel
Akahori, R.; Schmeeckle, M. W.
2002-12-01
Recent research has shown that intermittency caused by large-scale turbulence structures in rivers can be critical to accurate prediction of the sediment transport field. These large-scale turbulence structures are inherently three-dimensional. This is especially true in a river meander where strong secondary flows affect not only the three-dimensional, time-averaged flow structure, but also the process of large-scale turbulent eddy generation. It is very difficult to directly measure the turbulence field in a river except at the water surface or a few points in the interior of the flow. Numerical simulation of turbulence is a powerful tool, because it can provide information about the non-averaged flow at each grid point. Many previous researchers have calculated the time-averaged flow in a meandering channel, and obtained useful results. However, simulations of turbulence in meandering channels have been restricted to two dimensions. Therefore, they have a problem in accurately reproducing important features of the flow. We present a 3-dimenstional turbulent model for the numerical calculation of channel flow. The turbulence cannot be resolved at scales smaller than the channel grid, and we therefore parameterize the effects of small scale turbulence using standard Large Eddy Simulation (LES) assumptions. A Body Fitted Coordinate (BFC) system is employed to fit the irregular boundaries of natural channels. To solve the Navier-Stokes equations on the finite difference mesh, we employ the Cubic-Interpolated Propagation (CIP) method. The CIP method precisely solves the convective acceleration terms without numerical diffusion.
Dong, Erbao; Zhao, Zuhua; Wang, Minjie; Xie, Yanjun; Li, Shidi; Shao, Pengfei; Cheng, Liuquan; Xu, Ronald X.
2015-12-01
Biomedical optical devices are widely used for clinical detection of various tissue anomalies. However, optical measurements have limited accuracy and traceability, partially owing to the lack of effective calibration methods that simulate the actual tissue conditions. To facilitate standardized calibration and performance evaluation of medical optical devices, we develop a three-dimensional fuse deposition modeling (FDM) technique for freeform fabrication of tissue-simulating phantoms. The FDM system uses transparent gel wax as the base material, titanium dioxide (TiO2) powder as the scattering ingredient, and graphite powder as the absorption ingredient. The ingredients are preheated, mixed, and deposited at the designated ratios layer-by-layer to simulate tissue structural and optical heterogeneities. By printing the sections of human brain model based on magnetic resonance images, we demonstrate the capability for simulating tissue structural heterogeneities. By measuring optical properties of multilayered phantoms and comparing with numerical simulation, we demonstrate the feasibility for simulating tissue optical properties. By creating a rat head phantom with embedded vasculature, we demonstrate the potential for mimicking physiologic processes of a living system.
Three-dimensional virtual simulation of alar width changes following bimaxillary osteotomies.
Liebregts, J; Xi, T; Schreurs, R; van Loon, B; Bergé, S; Maal, T
2016-10-01
The aim of this study was to evaluate the accuracy of three-dimensional (3D) soft tissue simulation of nose width changes following bimaxillary osteotomies and to identify patient- and surgery-related factors that may affect the accuracy of simulation. Sixty patients (mean age 26 years) who underwent bimaxillary osteotomies participated in this study. Cone beam computed tomography scans were acquired preoperatively and at 1-year postoperative. The 3D hard and soft tissue rendered preoperative and postoperative virtual head models were superimposed, after which the maxilla and mandible were segmented and aligned to the postoperative position. The postoperative changes in alar width were simulated using a mass tensor model (MTM)-based algorithm and compared with the postoperative outcome. 3D cephalometric analyses were used to quantify the simulation error. The postoperative alar width was increased by 1.6±1.1mm and the mean error between the 3D simulation and the actual postoperative alar width was 1.0±0.9mm. The predictability was not correlated to factors such as age, sex, alar cinch suture, VY closure, maxillary advancement, or a history of surgically assisted rapid maxillary expansion. The MTM-based simulation model of postoperative alar width change was found to be reasonably accurate, although there is room for further improvement.
CODE BLUE: Three dimensional massively-parallel simulation of multi-scale configurations
Juric, Damir; Kahouadji, Lyes; Chergui, Jalel; Shin, Seungwon; Craster, Richard; Matar, Omar
2016-11-01
We present recent progress on BLUE, a solver for massively parallel simulations of fully three-dimensional multiphase flows which runs on a variety of computer architectures from laptops to supercomputers and on 131072 threads or more (limited only by the availability to us of more threads). The code is wholly written in Fortran 2003 and uses a domain decomposition strategy for parallelization with MPI. The fluid interface solver is based on a parallel implementation of a hybrid Front Tracking/Level Set method designed to handle highly deforming interfaces with complex topology changes. We developed parallel GMRES and multigrid iterative solvers suited to the linear systems arising from the implicit solution for the fluid velocities and pressure in the presence of strong density and viscosity discontinuities across fluid phases. Particular attention is drawn to the details and performance of the parallel Multigrid solver. EPSRC UK Programme Grant MEMPHIS (EP/K003976/1).
Experimental results and simulations from aperture synthesis three-dimensional radiometric imaging
Salmon, Neil A.
2016-10-01
This paper presents the theory and algorithm of how a three-dimensional (3D) image can be generated using crosscorrelations of radiometric emission from a source measured using antennas in the near field. An example of how the algorithm is used to create 3D images of emission measured from a noise source is presented, indicating the presence of Fresnel noise and aliasing in the experimental data when the source is moved away from the phase centre. Simulations are presented which reproduce the Fresnel noise as generated by a 3x3x3 array of point sources located at the centre of a 2 metre diameter array of antennas representing a security screening portal. Two methods of reducing the Fresnel noise are presented: 1) a software method which makes successive more accurate estimates of the locations and intensities of sources; 2) a hardware method which reduces the coherence length of the radiation by increasing the radiation bandwidth.
A SIMULATION OF CO2 UPTAKE IN A THREE DIMENSIONAL OCEAN CARBON CYCLE MODEL
Institute of Scientific and Technical Information of China (English)
金心; 石广玉
2001-01-01
A three-dimensional ocean carbon cycle model which is a general circulation model couple.d with simple biogeochemical processes is used to simulate CO2 uptake by the ocean. The OGCM used is a modified version of the Geophysical Fluid Dynamics Laboratory modular ocean model (MOM2). The ocean chemistry and a simple ocean biota model are included. Principal variables are .total CO2, alkalinity and phosphate. The vertical profile of POC flux observed by sediment traps is adopted, the rain ratio, a ratio of production rate of calcite against that of POC, and the bio-production efficiency should be 0. 06 and 2 per year, separately. The uptake of anthropogenicCO2 by the ocean is studied. Calculated oceanic uptake of anthropogenic CO2 during the 1980s is 2. 05× 10 15g (Pg) per year. The regional distributions of global oceanic CO2 are discussed.
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
A three-dimensional molecular dynamics simulation using the embedded atom method (EAM) potentials shows that for both pure Ni and Ni+H, dislocations are firstly emitted during loading and the crack propagates after enough disloca tions are emitted. In the case of hydrogen embrittlement, local plastic deformat ion is a precondition for crack propagation. For the crack along the (1 11) slip pla ne, one atom fraction in percent of hydrogen can decrease the critical stress in tensity for dislocation emission KIe from 0.42 to 0.36 MPam 1/2, and that for crack propagation KIp from 0.80 to 0.76 MPam1/2. Therefore, hydrogen enhances dislocation emission and crack pro pagation.
Simulated annealing for three-dimensional low-beta reduced MHD equilibria in cylindrical geometry
Furukawa, M
2016-01-01
Simulated annealing (SA) is applied for three-dimensional (3D) equilibrium calculation of ideal, low-beta reduced MHD in cylindrical geometry. The SA is based on the theory of Hamiltonian mechanics. The dynamical equation of the original system, low-beta reduced MHD in this study, is modified so that the energy changes monotonically while preserving the Casimir invariants in the artificial dynamics. An equilibrium of the system is given by an extremum of the energy, therefore SA can be used as a method for calculating ideal MHD equilibrium. Previous studies demonstrated that the SA succeeds to lead to various MHD equilibria in two dimensional rectangular domain. In this paper, the theory is applied to 3D equilibrium of ideal, low-beta reduced MHD. An example of equilibrium with magnetic islands, obtained as a lower energy state, is shown. Several versions of the artificial dynamics are developed that can effect smoothing.
Institute of Scientific and Technical Information of China (English)
Liu Dong; Wang Fei; Huang Qun-Xing; Yan Jian-Hua; Chi Yong; Cen Ke-Fa
2008-01-01
This paper presents a reconstruction model of three-dimensional temperature distribution in furnace based on radiative energy images captured by charge-coupled device (CCD) cameras within the visible wavelength range. Numerical simulation case was used in this study and a zigzag eccentric temperature distribution was assumed to verify the model. Least square QR-factorization (LSQR) method was introduced to deal with reconstruction equation. It is found that the reconstructed temperature distributions in low-temperature areas had some fluctuations and high-temperature areas were reconstructed well The whole reconstruction relative error was mainly due to errors in low-temperature areas and the relative error for highest-temperature reconstruction was quite small.
Numerical Filling Simulation of Injection Molding Using Three-Dimensional Model
Institute of Scientific and Technical Information of China (English)
GengTie; LiDequn; ZhouHuamin
2003-01-01
Most injection molded parts are three-dimensional, with complex geometrical configurations and thick/thin wall sections. A 3D simulation model will predict more accurately the filling process than a 2.5D model. This paper gives a mathematical model and numeric method based on 3D model, in which an equal-order velocity-pressure interpolation method is employed successfully. The relation between velocity and pressure is obtained from the discretized momentum equations in order to derive the pressure equation. A 3D control volume scheme is employed to track the flow front. The validity of the model has been tested through the analysis of the flow in cavity.
Resch, Janelle; Vanderkooy, John
2016-01-01
The length and bore geometry of musical instruments directly influences the quality of sound that can be produced. In brass instruments, nonlinear effects from finite-amplitude wave propagation can lead to wave distortion giving sounds a brassy timbre [3, 5, 14, 20, 26]. In this paper, we propose a three-dimensional model to describe nonlinear wave propagation in a trumpet and investigate the importance of the mouthpiece shank geometry. Time pressure waveforms corresponding to B_3(b) and B_4(b) notes were recorded at the mouthpiece shank and used as inputs for our model. To describe the motion of compressible inviscid fluid, we numerically solved the compressible Euler equations using the discontinuous Galerkin method. To validate our approach, the numerical results were compared to the recorded musical notes outside the bell of the trumpet. Simulations were performed on computational trumpets where different bore geometries were considered. Our results demonstrate that the shape of the narrow region near mou...
Three-Dimensional Water-Quality Simulation for River Based on VOF Method
Institute of Scientific and Technical Information of China (English)
敖雪菲; 王晓玲; 宋明瑞; 邓韶辉; 李松敏
2016-01-01
In the present study, considering the transport and transformation processes of variables, a three-dimensional water quality model for the river system was established, which coupled the volume of fluid(VOF) method with thek-ε turbulence mathematical model. Then, the water hydrodynamic characteristics and transport processes for BOD5, NH3-N and TP were analyzed. The results showed that the water surface of convex bank was a little lower than that of concave bank due to the centrifugal force near the bend, and most concentrations were infe-rior to the typeⅤ standard indexes of surface water environmental quality. The model validation indicated that the errors between the simulated and monitored values were comparatively small, satisfying the application demands and providing scientific basis and decision support for the restoration and protection of water quality.
Detailed analysis of fan-shaped jets in three dimensional numerical simulation
Institute of Scientific and Technical Information of China (English)
Rong-Lin Jiang; K. Shibata; H. Isobe; Cheng Fang
2011-01-01
We performed three dimensional resistive magnetohydrodynamic simulations to study the magnetic reconnection using an initially shearing magnetic field configuration (force free field with a current sheet in the middle of the computational box). It is shown that there are two types of reconnection jets: the ordinary reconnection jets and fan-shaped jets, which are formed along the guide magnetic field. The fan-shaped jets are significantly different from the ordinary reconnection jets which are ejected by magnetic tension force. There are two driving forces for accelerating the fan-shaped jets. One is the Lorentz force which initially dominates the motion of fluid elements, and then the gas pressure gradient force accelerates the fluid elements in the later stage. The dependence on magnetic reconnection angle and resistivity value has also been studied. The formation and evolution of these jets provide a new understanding of dynamic magnetohydrodynamicjets.
Simulation of radiation effects on three-dimensional computer optical memories
Moscovitch, M.; Emfietzoglou, D.
1997-01-01
A model was developed to simulate the effects of heavy charged-particle (HCP) radiation on the information stored in three-dimensional computer optical memories. The model is based on (i) the HCP track radial dose distribution, (ii) the spatial and temporal distribution of temperature in the track, (iii) the matrix-specific radiation-induced changes that will affect the response, and (iv) the kinetics of transition of photochromic molecules from the colored to the colorless isomeric form (bit flip). It is shown that information stored in a volume of several nanometers radius around the particle's track axis may be lost. The magnitude of the effect is dependent on the particle's track structure.
Directory of Open Access Journals (Sweden)
Omid Mahabadi
2014-12-01
Full Text Available This study presents the first step of a research project that aims at using a three-dimensional (3D hybrid finite-discrete element method (FDEM to investigate the development of an excavation damaged zone (EDZ around tunnels in a clay shale formation known as Opalinus Clay. The 3D FDEM was first calibrated against standard laboratory experiments, including Brazilian disc test and uniaxial compression test. The effect of increasing confining pressure on the mechanical response and fracture propagation of the rock was quantified under triaxial compression tests. Polyaxial (or true triaxial simulations highlighted the effect of the intermediate principal stress (σ2 on fracture directions in the model: as the intermediate principal stress increased, fractures tended to align in the direction parallel to the plane defined by the major and intermediate principal stresses. The peak strength was also shown to vary with changing σ2.
THREE-DIMENSIONAL NUMERICAL SIMULATION OF TIDES AND CURRENTS IN FUSHAN BAY, QINGDAO
Institute of Scientific and Technical Information of China (English)
LI Ming-kui; HOU Yi-jun; WEI Ze-xun
2004-01-01
The three-dimensional Princeton Ocean Model(POM)was employed to simulate the tide and current simultanuously for the first time in the Fushan Bay,Qingdao,China.By adopting the elevation condition that was combined with the tides M2,S2,K1 and O1 at the open boundary and by choosing the proper value of bottom roughness,the horizontal and vertical distributions of the tidal current and water level variations in the bay were computed.The results agree well with the field observation data,indicating that this model can be used to predict accurately the variation of tides and currents in the Fushan Bay and other costal regions in the future.Our study also provides useful information and a data base for the Olympic Projects that will be conducted in the Fushan Bay in 2008.
Numerical simulations of three-dimensional magnetic swirls in a solar flux-tube
Chmielewski, Piotr; Murawski, Krzysztof; Solov'ev, Alexandr A.
2014-07-01
We aim to numerically study evolution of Alfvén waves that accompany short-lasting swirl events in a solar magnetic flux-tube that can be a simple model of a magnetic pore or a sunspot. With the use of the FLASH code we numerically solve three-dimensional ideal magnetohydrodynamic equations to simulate twists which are implemented at the top of the photosphere in magnetic field lines of the flux-tube. Our numerical results exhibit swirl events and Alfvén waves with associated clockwise and counterclockwise rotation of magnetic lines, with the largest values of vorticity at the bottom of the chromosphere, and a certain amount of energy flux.
A Solver for Massively Parallel Direct Numerical Simulation of Three-Dimensional Multiphase Flows
Shin, S; Juric, D
2014-01-01
We present a new solver for massively parallel simulations of fully three-dimensional multiphase flows. The solver runs on a variety of computer architectures from laptops to supercomputers and on 65536 threads or more (limited only by the availability to us of more threads). The code is wholly written by the authors in Fortran 2003 and uses a domain decomposition strategy for parallelization with MPI. The fluid interface solver is based on a parallel implementation of the LCRM hybrid Front Tracking/Level Set method designed to handle highly deforming interfaces with complex topology changes. We discuss the implementation of this interface method and its particular suitability to distributed processing where all operations are carried out locally on distributed subdomains. We have developed parallel GMRES and Multigrid iterative solvers suited to the linear systems arising from the implicit solution of the fluid velocities and pressure in the presence of strong density and viscosity discontinuities across flu...
Matrix Algorithm for Braiding Simulation of Three-Dimensional Four-Step Braided Composites
Directory of Open Access Journals (Sweden)
Xin Ma
2016-01-01
Full Text Available This paper proposes a new kind of computational approach of three-dimensional (3D braiding simulation based on matrix theory and symbol operation, which is suitable for batch integral calculation. The approach can be used to calculate braiding matrix at any step. Different braiding matrices fully reflect yarn carrier position changes. Using the braiding matrix calculation, the approach can provide data for storing yarn carrier paths, also termed braiding paths. The 3D braiding paths study was conducted to better visualization and thereby analyse the carrier’s movement characteristics and principles of operation. Finally, a program was designed to provide a reference for the mathematical model in further research.
Three-dimensional numerical simulation of a bird model in unsteady flight
Lin-Lin, Zhu; Hui, Guan; Chui-Jie, Wu
2016-07-01
In this paper, a type of numerical simulation of a three-dimensional (3D) bionic bird with flapping wings in a viscous flow is studied. The model is a self-propelled flying bird capable of free rotation and translation whose flying motion follows the laws of conservation of momentum and angular momentum. The bird is propelled and lifted through flapping and rotating wings and most of thrust force and lift force are exerted on both wings. Both the vortex structures and the flight characteristics are also presented. The relationship between both wings' movement and the vortex structures as well as that between both wings' movement and flight characteristics are also analyzed in this paper. The study uses a 3D computational fluid dynamics package that includes the combined immersed boundary method, volume of fluid method, adaptive multigrid finite volume method, and control strategy for swimming and flying.
Simulating three-dimensional nonthermal high-energy photon emission in colliding-wind binaries
Energy Technology Data Exchange (ETDEWEB)
Reitberger, K.; Kissmann, R.; Reimer, A.; Reimer, O., E-mail: klaus.reitberger@uibk.ac.at [Institut für Astro- und Teilchenphysik and Institut für Theoretische Physik, Leopold-Franzens-Universität Innsbruck, A-6020 Innsbruck (Austria)
2014-07-01
Massive stars in binary systems have long been regarded as potential sources of high-energy γ rays. The emission is principally thought to arise in the region where the stellar winds collide and accelerate relativistic particles which subsequently emit γ rays. On the basis of a three-dimensional distribution function of high-energy particles in the wind collision region—as obtained by a numerical hydrodynamics and particle transport model—we present the computation of the three-dimensional nonthermal photon emission for a given line of sight. Anisotropic inverse Compton emission is modeled using the target radiation field of both stars. Photons from relativistic bremsstrahlung and neutral pion decay are computed on the basis of local wind plasma densities. We also consider photon-photon opacity effects due to the dense radiation fields of the stars. Results are shown for different stellar separations of a given binary system comprising of a B star and a Wolf-Rayet star. The influence of orbital orientation with respect to the line of sight is also studied by using different orbital viewing angles. For the chosen electron-proton injection ratio of 10{sup –2}, we present the ensuing photon emission in terms of two-dimensional projections maps, spectral energy distributions, and integrated photon flux values in various energy bands. Here, we find a transition from hadron-dominated to lepton-dominated high-energy emission with increasing stellar separations. In addition, we confirm findings from previous analytic modeling that the spectral energy distribution varies significantly with orbital orientation.
FAST: a three-dimensional time-dependent FEL simulation code
Saldin, E L; Yurkov, M V
1999-01-01
In this report we briefly describe the three-dimensional, time-dependent FEL simulation code FAST. The equations of motion of the particles and Maxwell's equations are solved simultaneously taking into account the slippage effect. Radiation fields are calculated using an integral solution of Maxwell's equations. A special technique has been developed for fast calculations of the radiation field, drastically reducing the required CPU time. As a result, the developed code allows one to use a personal computer for time-dependent simulations. The code allows one to simulate the radiation from the electron bunch of any transverse and longitudinal bunch shape; to simulate simultaneously an external seed with superimposed noise in the electron beam; to take into account energy spread in the electron beam and the space charge fields; and to simulate a high-gain, high-efficiency FEL amplifier with a tapered undulator. It is important to note that there are no significant memory limitations in the developed code and an...
Lyons, B. C.; Ferraro, N. M.; Paz-Soldan, C.; Nazikian, R.; Wingen, A.
2017-04-01
In order to understand the effect of rotation on the response of a plasma to three-dimensional magnetic perturbations, we perform a systematic scan of the zero-crossing of the rotation profile in a DIII-D ITER-similar shape equilibrium using linear, time-independent modeling with the M3D-C1 extended magnetohydrodynamics code. We confirm that the local resonant magnetic field generally increases as the rotation decreases at a rational surface. Multiple peaks in the resonant field are observed near rational surfaces, however, and the maximum resonant field does not always correspond to zero rotation at the surface. Furthermore, we show that non-resonant current can be driven at zero-crossings not aligned with rational surfaces if there is sufficient shear in the rotation profile there, leading to amplification of near-resonant Fourier harmonics of the perturbed magnetic field and a decrease in the far-off-resonant harmonics. The quasilinear electromagnetic torque induced by this non-resonant plasma response provides drive to flatten the rotation, possibly allowing for increased transport in the pedestal by the destabilization of turbulent modes. In addition, this torque acts to drive the rotation zero-crossing to dynamically stable points near rational surfaces, which would allow for increased resonant penetration. By one or both of these mechanisms, this torque may play an important role in bifurcations into suppression of edge-localized modes. Finally, we discuss how these changes to the plasma response could be detected by tokamak diagnostics. In particular, we show that the changes to the resonant field discussed here have a significant impact on the external perturbed magnetic field, which should be observable by magnetic sensors on the high-field side of tokamaks but not on the low-field side. In addition, TRIP3D-MAFOT simulations show that none of the changes to the plasma response described here substantially affects the divertor footprint structure.
Xia, J; Samman, N; Yeung, R W; Wang, D; Shen, S G; Ip, H H; Tideman, H
2000-08-01
The purpose of this paper is to report a new technique for three-dimensional facial soft-tissue-change prediction after simulated orthognathic surgical planning. A scheme for soft tissue deformation, "Computer-assisted three-dimensional virtual reality soft tissue planning and prediction for orthognathic surgery (CASP)", is presented. The surgical planning was based on three-dimensional reconstructed CT visualization. Soft tissue changes were predicted by two newly devised algorithms: Surface Normal-based Model Deformation Algorithm and Ray Projection-based Model Deformation Algorithm. A three-dimensional color facial texture-mapping technique was also used for generating the color photo-realistic facial model. As a final result, a predicted and simulated patient's color facial model can be visualized from arbitrary viewing points.
Stein, Itai Y.; Wardle, Brian L.
2016-01-01
The promise of enhanced and tailored properties motivates the study of one-dimensional nanomaterials, especially aligned carbon nanotubes (A-CNTs), for the reinforcement of polymeric materials. While CNTs have remarkable theoretical properties, previous work on aligned CNT polymer matrix nanocomposites (A-PNCs) reported mechanical properties that are orders of magnitude lower than those predicted by rule of mixtures. This large difference primarily originates from the morphology of the CNTs, because the CNTs that comprise the A-PNCs have significant local curvature commonly referred to as waviness. Here we present a simulation framework capable of analyzing 105 wavy CNTs with realistic three-dimensional morphologies to quantify the impact of waviness on the effective elastic modulus contribution of wavy CNTs. The simulation results show that due to the low shear modulus of the reinforcing CNT ‘fibers’, and large (\\gt 50%) compliance contribution of the shear deformation mode, waviness reduces the effective stiffness contribution of the A-CNTs by two to three orders of magnitude. Also, the mechanical property predictions resulting from the simulation framework outperform those previously reported using finite element analysis since representative descriptions of the morphology are required to accurately predict properties of the A-PNCs. Further work to quantify the morphology of A-PNCs in three-dimensions, simulate their full non-isotropic constitutive relations, and predict their failure mechanisms is planned.
THREE-DIMENSIONAL TURBULENCE NUMERICAL SIMULATION OF A STEPPED SPILLWAY OVERFLOW
Institute of Scientific and Technical Information of China (English)
CHEN Qun; DAI Guang-qing; ZHU Fen-qing; YANG Qing
2004-01-01
In this paper, the k-ε two-equation turbulence model was used to simulate the three-dimensional turbulent flow of the stepped spillway at the Yubeishan reservoir. In order to solve the curved free water surface and to handle the complex boundary conditions, the fractional Volume Of Fluid (VOF) model that is applicable to the solution of the stratified two-phase flow was intorduced to the k-ε turbulence model and the unstructured grid was used for the discretization of the irregular simulation domain. By these methods, the turbulent flow field of the stepped spillway was simulated successfully. The location of the free surface along the spillway, the magnitude and distribution of the velocity, the pressure distribution on the step surface, the turbulence kinetic energy and turbulence dissipation rate were obtained by simulation. The changes and distributions of these characteristics along the width of the spillway were also obtained. The energy dissipation ratio of the stepped spillway was calculated according to the upstream and downstream water depth and velocities.
THREE-DIMENSIONAL TURBULENCE NUMERICAL SIMULATION OF A STEPPED SPILLWAY OVERFLOW
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
In this paper, the k-ε turbulence model is usedto simulate the three-dimensional turbulence flow over thestepped spillway at the Yubeishan reservoir. In order to solvethe curved free water surface and to handle the complexboundary conditions, the fractional Volume Of Fluid (VOF)model that is applicable to the solution of the stratified two-phase flow is introduced along with k-ε turbulence model and the unstructured grid is used for the discretization of the irreg-ular simulation domain. By these methods, the turbulenceflow field of the stepped spillway is simulated successfully.The location of the free surface along the spillway, the magni-tude and distribution of the velocity, the pressure on the stepsurface, the turbulence kinetic energy and turbulence dissipa-tion rate are obtained by simulation. The changes and distri-butions of these characteristics along the width of the spillwayare also obtained. The energy dissipation ratio of the steppedspillway is calculated according to the upstream and down-stream water depth and velocities.
Simulation of three-dimensional nonideal MHD flow at high magnetic Reynolds number
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
A conservative TVD scheme is adopted to solve the equations governing the three-dimensional flow of a nonideal compressible conducting fluid in a magnetic field.The eight-wave equations for magnetohydrodynamics(MHD) are proved to be a non-strict hyperbolic system,therefore it is difficult to develop its eigenstructure.Powell developed a new set of equations which cannot be numerically simulated by conservative TVD scheme directly due to its non-conservative form.A conservative TVD scheme augmented with a new set of eigenvectors is proposed in the paper.To validate this scheme,1-D MHD shock tube,unsteady MHD Rayleigh problem and steady MHD Hartmann problem for different flow conditions are simulated.The simulated results are in good agreement with the existing analytical results.So this scheme can be used to effectively simulate high-conductivity fluids such as cosmic MHD problem and hypersonic MHD flow over a blunt body,etc.
Atomic quantum simulation of a three-dimensional U(1) gauge-Higgs model
Kuno, Yoshihito; Kasamatsu, Kenichi; Ichinose, Ikuo; Matsui, Tetsuo
2016-01-01
In this paper, we study atomic quantum simulations of a U(1) gauge-Higgs model on a three-dimensional (3D) spatial lattice. We start from an extended 3D Bose-Hubbard model with nearest-neighbor repulsions and show that it can simulate a U(1) gauge-Higgs model with next nearest-neighbor Higgs couplings. Here the phase of the boson variable on each site of the optical lattice describes the vector potential on each link of the gauge-model lattice. To determine the phase diagram of the gauge-Higgs model at a zero temperature, we perform Monte-Carlo simulations of the corresponding 3+1-dimensional U(1) gauge-Higgs model, and obtain the three phases, i.e., the confinement, Coulomb and Higgs phases. To investigate the dynamical properties of the gauge-Higgs model, we apply the Gross-Pitaevskii equations to the extended Bose-Hubbard model. We simulate the time-evolution of an electric flux initially put on a straight line connecting two external point charges. We also calculate the potential energy between this pair ...
Simulation of three-dimensional nonideal MHD flow at low magnetic Reynolds number
Institute of Scientific and Technical Information of China (English)
LU HaoYu; LEE ChunHian
2009-01-01
A numerical procedure based on a five-wave model associated with non-ideal,low magnetic Reynolds number magnetohydrodynamic(MHD)flows was developed.It is composed of an entropy conditioned scheme for solving the non-homogeneous Navier-Stokes equations,in conjunction with an SOR method for solving the elliptic equation governing the electrical potential of flow field.To validate the developed procedure,two different test cases were used which included MHD Rayleigh problem and MHD Hartmann problem.The simulations were performed under the assumption of low magnetic Reynolds number.The simulated results were found to be in good agreement with the closed form analytical solutions deduced in the present study,showing that the present algorithm could simulate engineering MHD flow at low magnetic Reynolds number effectively.In the end,a flow field between a pair of segmented electrodes in a three dimensional MHD channel was simulated using the present algorithm with and without including Hall effects.Without the introduction of Hall effects,no distortion was observed in the current and potential lines.By taking the Hall effects into account,the potential lines distorted and clustered at the upstream and downstream edges of the cathode and anode,respectively.
Burgess, David; Hellinger, Petr; Gingell, Imogen; Trávníček, Pavel M.
2016-08-01
Supercritical collisionless perpendicular shocks have an average macrostructure determined primarily by the dynamics of ions specularly reflected at the magnetic ramp. Within the overall macrostructure, instabilities, both linear and nonlinear, generate fluctuations and microstructure. To identify the sources of such microstructure, high-resolution two- and three-dimensional simulations have been carried out using the hybrid method, wherein the ions are treated as particles and the electron response is modelled as a massless fluid. We confirm the results of earlier two-dimensional (2-D) simulations showing both field-parallel aligned propagating fluctuations and fluctuations carried by the reflected-gyrating ions. In addition, it is shown that, for 2-D simulations of the shock coplanarity plane, the presence of short-wavelength fluctuations in all magnetic components is associated with the ion Weibel instability driven at the upstream edge of the foot by the reflected-gyrating ions. In 3-D simulations we show for the first time that the dominant microstructure is due to a coupling between field-parallel propagating fluctuations in the ramp and the motion of the reflected ions. This results in a pattern of fluctuations counter-propagating across the surface of the shock at an angle inclined to the magnetic field direction, due to a combination of field-parallel motion at the Alfvén speed of the ramp and motion in the sense of gyration of the reflected ions.
Chan, Leon; MacDonald, Michael; Chung, Daniel; Hutchins, Nicholas; Ooi, Andrew
2014-11-01
Direct Numerical Simulations (DNS) are conducted at low to medium Reynolds numbers for a turbulent pipe flow with roughness. The roughness, which is comprised of three-dimensional sinusoidal elements, causes a downward shift in the mean velocity profile known as the Hama roughness function ΔU+ . In engineering applications, ΔU+ (which is related to the coefficient of drag Cf) is an important parameter as it is used to quantify the increase in drag and the decrease in efficiency. To have a better understanding of roughness and how it affects the flow, a range of numerical studies were conducted where the roughness height h+, wavelength λ+ and Reynolds number of the flow are varied. For the range of cases simulated, it is found that the roughness average height ka+ (which is proportional to h+) is strongly correlated to the roughness function ΔU+ whereas λ+ has a weaker influence on the flow. Results from simulations of more complicated surfaces comprised of two superimposed modes of different wavelength are also presented. Analysis of the turbulence statistics convincingly supports Townsend's outer-layer hypothesis for all of the cases simulated.
Three-Dimensional Simulations of Electron Beams Focused by Periodic Permanent Magnets
Kory, Carol L.
1999-01-01
A fully three-dimensional (3D) model of an electron beam focused by a periodic permanent magnet (PPM) stack has been developed. First, the simulation code MAFIA was used to model a PPM stack using the magnetostatic solver. The exact geometry of the magnetic focusing structure was modeled; thus, no approximations were made regarding the off-axis fields. The fields from the static solver were loaded into the 3D particle-in-cell (PIC) solver of MAFIA where fully 3D behavior of the beam was simulated in the magnetic focusing field. The PIC solver computes the time-integration of electromagnetic fields simultaneously with the time integration of the equations of motion of charged particles that move under the influence of those fields. Fields caused by those moving charges are also taken into account; thus, effects like space charge and magnetic forces between particles are fully simulated. The electron beam is simulated by a number of macro-particles. These macro-particles represent a given charge Q amounting to that of several million electrons in order to conserve computational time and memory. Particle motion is unrestricted, so particle trajectories can cross paths and move in three dimensions under the influence of 3D electric and magnetic fields. Correspondingly, there is no limit on the initial current density distribution of the electron beam, nor its density distribution at any time during the simulation. Simulation results including beam current density, percent ripple and percent transmission will be presented, and the effects current, magnetic focusing strength and thermal velocities have on beam behavior will be demonstrated using 3D movies showing the evolution of beam characteristics in time and space. Unlike typical beam optics models, this 3D model allows simulation of asymmetric designs such as non- circularly symmetric electrostatic or magnetic focusing as well as the inclusion of input/output couplers.
Yoshimitsu, Nana; Furumura, Takashi; Maeda, Takuto
2016-09-01
The coda part of a waveform transmitted through a laboratory sample should be examined for the high-resolution monitoring of the sample characteristics in detail. However, the origin and propagation process of the later phases in a finite-sized small sample are very complicated with the overlap of multiple unknown reflections and conversions. In this study, we investigated the three-dimensional (3D) geometric effect of a finite-sized cylindrical sample to understand the development of these later phases. This study used 3D finite difference method simulation employing a free-surface boundary condition over a curved model surface and a realistic circular shape of the source model. The simulated waveforms and the visualized 3D wavefield in a stainless steel sample clearly demonstrated the process of multiple reflections and the conversions of the P and S waves at the side surface as well as at the top and bottom of the sample. Rayleigh wave propagation along the curved side boundary was also confirmed, and these waves dominate in the later portion of the simulated waveform with much larger amplitudes than the P and S wave reflections. The feature of the simulated waveforms showed good agreement with laboratory observed waveforms. For the simulation, an introduction of an absorbing boundary condition at the top and bottom of the sample made it possible to efficiently separate the contribution of the vertical and horizontal boundary effects in the simulated wavefield. This procedure helped to confirm the additional finding of vertically propagating multiple surface waves and their conversion at the corner of the sample. This new laboratory-scale 3D simulation enabled the appearance of a variety of geometric effects that constitute the later phases of the transmitted waves.
Köllner, Thomas; Rossi, Maurice; Broer, Frauke; Boeck, Thomas
2014-11-01
A case of convection driven by chemical reactions is studied by linear stability theory and direct numerical simulations. In a plane aqueous layer of glucose, the methylene-blue-enabled catalytic oxidation of glucose produces heavier gluconic acid. As the oxygen is supplied through the top surface, the production of gluconic acid leads to an overturning instability. Our results complement earlier experimental and numerical work by Pons et al. First, we extend the model by including the top air layer with diffusive transport and Henry's law for the oxygen concentration at the interface to provide a more realistic oxygen boundary condition. Second, a linear stability analysis of the diffusive basic state in the layers is performed using an optimal perturbation approach. This method is appropriate for the unsteady basic state and determines the onset time of convection and the associated wavelength. Third, the nonlinear evolution is studied by the use of three-dimensional numerical simulations. Three typical parameters sets are explored in detail showing significant differences in pattern formation. One parameter set for which the flow is dominated by viscous forces, displays persistently growing convection cells. The other set with increased reaction rate displays a different flow regime marked by local chaotic plume emission. The simulated patterns are then compared to experimental observations.
Three dimensional simulation of fluid flow in X-ray CT images of porous media
Al-Omari, A.; Masad, E.
2004-11-01
A numerical scheme is developed in order to simulate fluid flow in three dimensional (3-D) microstructures. The governing equations for steady incompressible flow are solved using the semi-implicit method for pressure-linked equations (SIMPLE) finite difference scheme within a non-staggered grid system that represents the 3-D microstructure. This system allows solving the governing equations using only one computational cell. The numerical scheme is verified through simulating fluid flow in idealized 3-D microstructures with known closed form solutions for permeability. The numerical factors affecting the solution in terms of convergence and accuracy are also discussed. These factors include the resolution of the analysed microstructure and the truncation criterion. Fluid flow in 2-D X-ray computed tomography (CT) images of real porous media microstructure is also simulated using this numerical model. These real microstructures include field cores of asphalt mixes, laboratory linear kneading compactor (LKC) specimens, and laboratory Superpave gyratory compactor (SGC) specimens. The numerical results for the permeability of the real microstructures are compared with the results from closed form solutions. Copyright
Three-dimensional particle-in-cell simulation on gain saturation effect of microchannel plate.
Wang, Qiangqiang; Yuan, Zheng; Cao, Zhurong; Deng, Bo; Chen, Tao; Deng, Keli
2016-07-01
We present here the results of the simulation work, using the three-dimensional particle-in-cell method, on the performance of the lead glass microchannel plate under saturated state. We calculated the electron cascade process with different DC bias voltages under both self-consistent condition and non-self-consistent condition. The comparative results have demonstrated that the strong self-consistent field can suppress the cascade process and make the microchannel plate saturated. The simulation results were also compared to the experimental data and good agreement was obtained. The simulation results also show that the electron multiplication process in the channel is accompanied by the buildup process of positive charges in the channel wall. Though the interactions among the secondary electron cloud in the channel, the positive charges in the channel wall, and the external acceleration field can make the electron-surface collision more frequent, the collision energy will be inevitably reduced, thus the electron gain will also be reduced.
Isaacs, Kristin K; Schlesinger, R B; Martonen, Ted B
2006-01-01
Simulation of the dynamics and disposition of inhaled particles within human lungs is an invaluable tool in both the development of inhaled pharmacologic drugs and the risk assessment of environmental particulate matter (PM). The goal of the present focused study was to assess the utility of three-dimensional computational fluid dynamics (CFD) models in studying the local deposition patterns of PM in respiratory airways. CFD models were validated using data from published experimental studies in human lung casts. The ability of CFD to appropriately simulate trends in deposition patterns due to changing ventilatory conditions was specifically addressed. CFD simulations of airflow and particle motion were performed in a model of the trachea and main bronchi using Fluent Inc.'s FIDAP CFD software. Particle diameters of 8 microm were considered for input flow rates of 15 and 60 L/min. CFD was able to reproduce the observed spatial heterogeneities of deposition within the modeled bifurcations, and correctly predicted the "hot-spots" of particle deposition on carinal ridges. The CFD methods also predicted observed differences in deposition for high-versus-low flow rates. CFD models may provide an efficient means of studying the complex effects of airway geometry, particle characteristics, and ventilatory parameters on particle deposition and therefore aid in the design of human subject experiments.
Three-dimensional Simulations of Pure Deflagration Models for Thermonuclear Supernovae
Long, Min; van Rossum, Daniel R; Diemer, Benedikt; Graziani, Carlo; Kessler, Richard; Meyer, Bradley; Rich, Paul; Lamb, Don Q
2013-01-01
We present a systematic study of the pure deflagration model of Type Ia supernovae, using three-dimensional, high-resolution, full-star hydrodynamical simulations, nucleosynthetic yields calculated using Lagrangian tracer particles, light curves calculated using radiation transport, and evaluation the simulations through comparison of their predicted light curves with many observed SNe Ia using the SALT2 data-driven model. We explore the effect on the properties of the simulations of different initial conditions by varying the number of ignition points and the radius of the sphere in which they are confined. The number of ignition points ranges from 63 to 3500, and they are placed randomly within confining spheres with radii of 128 km, 256 km, and 384 km whose centers coincide with the center of the white dwarf. The nuclear energy released and the final products of the nuclear burning are diverse. We find that the nuclear energy released, the kinetic energy, and the distributions of the overall mass density a...
General-Relativistic Simulations of Three-Dimensional Core-Collapse Supernovae
Ott, C D; Moesta, P; Haas, R; Drasco, S; O'Connor, E; Reisswig, C; Meakin, C; Schnetter, E
2012-01-01
We study the three-dimensional (3D) hydrodynamics of the post-core-bounce phase of the collapse of a 27 solar-mass star and pay special attention to the development of the standing accretion shock instability (SASI) and neutrino-driven convection. To this end, we perform 3D general-relativistic simulations with a 3-species neutrino leakage scheme with neutrino heating. Unlike "light-bulb" heating/cooling schemes, the leakage scheme captures the essential aspects of neutrino cooling, heating, and lepton number exchange as predicted by radiation-hydrodynamics simulations. The 27 solar-mass progenitor was studied in 2D by B. Mueller et al. (2012; arXiv:1205.7078), who observed strong growth of the SASI while neutrino-driven convection was suppressed. In our 3D simulations, neutrino-driven convection grows from numerical perturbations imposed by our Cartesian grid. It becomes the dominant instability and leads to large-scale non-oscillatory deformations of the shock front. These will result in strongly aspherical...
Three-dimensional simulation of liquid flow on a sieve tray under different inclinations
Directory of Open Access Journals (Sweden)
Zhang Ping
2014-12-01
Full Text Available The fluid state on a sieve tray will change when the towers tilt under wind loads. A computational fluid dynamics (CFD model was used to predict the flow patters and hydraulics on the tray under different inclinations. The gas and liquid phases are modelled with the volume-of-fluid (VOF framework as two inmiscible phases. Several three-dimensional transient simulations were carried out for a 0.38m diameter tray with varying liquid weir loads and inclined angles. The clear liquid height determined from these simulations is in reasonable agreement with experimental measurements carried out for air-water in a round tray of the same dimensions. The simulation results show that, compared with the horizontal tray, the circulation area is bigger when the liquid flow and inclination direction of the tray are the same, but when they are opposite the circulation area is smaller. The percentage of circulation area to the tray area can obviously be decreased, along with increasing liquid weir loads. It is concluded that CFD can be used for the prediction of liquid flow on sieve trays under different inclinations
Beam model and three dimensional numerical simulations on suspended microchannel resonators
Directory of Open Access Journals (Sweden)
Kuan-Rong Huang
2012-12-01
Full Text Available At the microscale level, the vibrational characteristics of microstructures have been widely applied on biochemical microchips, especially for bio-molecules detection. The vibrational mechanics and mechanism of microcantilever beams immersed in the fluids for detecting target bio-molecules carried in the fluids have been widely studied and realized in recent years. However, it is not the case for microcantilever beams containing fluids inside (called suspended microchannel resonators, SMR. In this paper, an 1-D beam model for SMR is proposed and the formula for prediction of resonant frequency and resonant frequency shift are derived. For verification of validity of the 1-D beam model, three dimensional finite element simulations using ANSYS are performed. The effects of relevant parameters, such as density and viscosity of the fluids, on the frequency response are investigated. A link between numerical simulations and mathematical modeling is established through an equivalence relation. Subsequently, a useful formula of the resonant frequency shift as a function of the mass variation and the viscosity of the contained fluid is derived. Good agreement between the numerical simulations and the experimental data is obtained and the physical mechanism is elucidated.
Gastelum, Alfonso; Mata, Lucely; Brito-de-la-Fuente, Edmundo; Delmas, Patrice; Vicente, William; Salinas-Vázquez, Martín; Ascanio, Gabriel; Marquez, Jorge
2016-03-01
We aimed to provide realistic three-dimensional (3D) models to be used in numerical simulations of peristaltic flow in patients exhibiting difficulty in swallowing, also known as dysphagia. To this end, a 3D model of the upper gastrointestinal tract was built from the color cryosection images of the Visible Human Project dataset. Regional color heterogeneities were corrected by centering local histograms of the image difference between slices. A voxel-based model was generated by stacking contours from the color images. A triangle mesh was built, smoothed and simplified. Visualization tools were developed for browsing the model at different stages and for virtual endoscopy navigation. As result, a computer model of the esophagus and the stomach was obtained, mainly for modeling swallowing disorders. A central-axis curve was also obtained for virtual navigation and to replicate conditions relevant to swallowing disorders modeling. We show renderings of the model and discuss its use for simulating swallowing as a function of bolus rheological properties. The information obtained from simulation studies with our model could be useful for physicians in selecting the correct nutritional emulsions for patients with dysphagia.
Three-dimensional, global, radiative GRMHD simulations of a thermally unstable disc
Mishra, B.; Fragile, P. C.; Johnson, L. C.; Kluźniak, W.
2016-12-01
We present results of a set of three-dimensional, general relativistic radiation magnetohydrodynamics simulations of thin accretion discs around a non-rotating black hole to test their thermal stability. We consider two cases, one that is initially radiation-pressure-dominated and expected to be thermally unstable and another that is initially gas-pressure dominated and expected to remain stable. Indeed, we find that cooling dominates over heating in the radiation-pressure-dominated model, causing the disc to collapse vertically on roughly the local cooling time-scale. We also find that heating and cooling within the disc have a different dependence on the mid-plane pressure - a prerequisite of thermal instability. Comparison of our data with the relevant thin-disc thermal equilibrium curve suggests that our disc may be headed for the thermally stable, gas-pressure-dominated branch. However, because the disc collapses to the point that we are no longer able to resolve it, we had to terminate the simulation. On the other hand, the gas-pressure-dominated model, which was run for twice as long as the radiation-pressure-dominated one, remains stable, with heating and cooling roughly in balance. Finally, the radiation-pressure-dominated simulation shows some evidence of viscous instability. The strongest evidence is in plots of surface density, which show the disc breaking up into rings.
Three-dimensional Simulations of Pure Deflagration Models for Thermonuclear Supernovae
Long, Min; Jordan, George C., IV; van Rossum, Daniel R.; Diemer, Benedikt; Graziani, Carlo; Kessler, Richard; Meyer, Bradley; Rich, Paul; Lamb, Don Q.
2014-07-01
We present a systematic study of the pure deflagration model of Type Ia supernovae (SNe Ia) using three-dimensional, high-resolution, full-star hydrodynamical simulations, nucleosynthetic yields calculated using Lagrangian tracer particles, and light curves calculated using radiation transport. We evaluate the simulations by comparing their predicted light curves with many observed SNe Ia using the SALT2 data-driven model and find that the simulations may correspond to under-luminous SNe Iax. We explore the effects of the initial conditions on our results by varying the number of randomly selected ignition points from 63 to 3500, and the radius of the centered sphere they are confined in from 128 to 384 km. We find that the rate of nuclear burning depends on the number of ignition points at early times, the density of ignition points at intermediate times, and the radius of the confining sphere at late times. The results depend primarily on the number of ignition points, but we do not expect this to be the case in general. The simulations with few ignition points release more nuclear energy E nuc, have larger kinetic energies E K, and produce more 56Ni than those with many ignition points, and differ in the distribution of 56Ni, Si, and C/O in the ejecta. For these reasons, the simulations with few ignition points exhibit higher peak B-band absolute magnitudes M B and light curves that rise and decline more quickly; their M B and light curves resemble those of under-luminous SNe Iax, while those for simulations with many ignition points are not.
Update on three-dimensional image reconstruction for preoperative simulation in thoracic surgery
Chen-Yoshikawa, Toyofumi F.
2016-01-01
Background Three-dimensional computed tomography (3D-CT) technologies have been developed and refined over time. Recently, high-speed and high-quality 3D-CT technologies have also been introduced to the field of thoracic surgery. The purpose of this manuscript is to demonstrate several examples of these 3D-CT technologies in various scenarios in thoracic surgery. Methods A newly-developed high-speed and high-quality 3D image analysis software system was used in Kyoto University Hospital. Simulation and/or navigation were performed using this 3D-CT technology in various thoracic surgeries. Results Preoperative 3D-CT simulation was performed in most patients undergoing video-assisted thoracoscopic surgery (VATS). Anatomical variation was frequently detected preoperatively, which was useful in performing VATS procedures when using only a monitor for vision. In sublobar resection, 3D-CT simulation was more helpful. In small lung lesions, which were supposedly neither visible nor palpable, preoperative marking of the lesions was performed using 3D-CT simulation, and wedge resection or segmentectomy was successfully performed with confidence. This technique also enabled virtual-reality endobronchial ultrasonography (EBUS), which made the procedure more safe and reliable. Furthermore, in living-donor lobar lung transplantation (LDLLT), surgical procedures for donor lobectomy were simulated preoperatively by 3D-CT angiography, which also affected surgical procedures for recipient surgery. New surgical techniques such as right and left inverted LDLLT were also established using 3D models created with this technique. Conclusions After the introduction of 3D-CT technology to the field of thoracic surgery, preoperative simulation has been developed for various thoracic procedures. In the near future, this technique will become more common in thoracic surgery, and frequent use by thoracic surgeons will be seen in worldwide daily practice. PMID:27014477
Mooney, James J; Sarwani, Nabeel; Coleman, Melissa L; Fotos, Joseph S
2017-06-01
The use of three-dimensional (3D) printing allows for creation of custom models for clinical care, education, and simulation. Medical imaging, given the significant role it plays in both clinical diagnostics and procedures, remains an important area for such education and simulation. Unfortunately, the materials appropriate for use in simulation involving radiographic or ultrasound imaging remains poorly understood. Therefore, our study was intended to explore the characteristics of readily available 3D printing materials when visualized by computed tomography (CT) and ultrasound. Seven 3D printing materials were examined in standard shapes (cube, cylinder, triangular prism) with a selection of printing methods ("open," "whole," and "solid" forms). For CT imaging, these objects were suspended in a gelatin matrix molded to match a standard human CT phantom. For ultrasound imaging, the objects were placed in acrylic forms filled with a gelatin matrix. All images were examined using OsiriX software. Computed tomography imaging revealed marked variation in materials' Hounsfield units as well as patterning and artifact. The Hounsfield unit variations revealed a number of materials suitable for simulation various human tissues. Ultrasound imaging showed echogenicity in all materials, with some variability in shadowing and posterior wall visualization. We were able to demonstrate the potential utility for 3D printing in the creation of CT and ultrasound simulation models. The similar appearance of materials via ultrasound supports their broad utility for select tissue types, whereas the more variable appearance via CT suggests greater potential for simulating differing tissues but requiring multiple printer technologies to do so.
Energy Technology Data Exchange (ETDEWEB)
Nishida, Keisuke; Shibata, Kazunari [Kwasan and Hida Observatories, Kyoto University, Yamashina, Kyoto 607-8471 (Japan); Nishizuka, Naoto, E-mail: nishida@kwasan.kyoto-u.ac.jp [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)
2013-10-01
We investigated the dynamic evolution of a three-dimensional (3D) flux rope eruption and magnetic reconnection process in a solar flare by simply extending the two-dimensional (2D) resistive magnetohydrodynamic simulation model of solar flares with low β plasma to a 3D model. We succeeded in reproducing a current sheet and bi-directional reconnection outflows just below the flux rope during the eruption in our 3D simulations. We calculated four cases of a strongly twisted flux rope and a weakly twisted flux rope in 2D and 3D simulations. The time evolution of a weakly twisted flux rope in the 3D simulation shows behaviors similar to those of the 2D simulation, while a strongly twisted flux rope in the 3D simulation clearly shows a different time evolution from the 2D simulation except for the initial phase evolution. The ejection speeds of both strongly and weakly twisted flux ropes in 3D simulations are larger than in the 2D simulations, and the reconnection rates in 3D cases are also larger than in the 2D cases. This indicates positive feedback between the ejection speed of a flux rope and the reconnection rate even in the 3D simulation, and we conclude that the plasmoid-induced reconnection model can be applied to 3D. We also found that small-scale plasmoids are formed inside a current sheet and make it turbulent. These small-scale plasmoid ejections have a role in locally increasing the reconnection rate intermittently as observed in solar flares, coupled with a global eruption of a flux rope.
Atomic quantum simulation of a three-dimensional U(1) gauge-Higgs model
Kuno, Yoshihito; Sakane, Shinya; Kasamatsu, Kenichi; Ichinose, Ikuo; Matsui, Tetsuo
2016-12-01
In this paper, we study theoretically atomic quantum simulations of a U(1) gauge-Higgs model on a three-dimensional (3D) spatial lattice by using an extended Bose-Hubbard model with intersite repulsions on a 3D optical lattice. Here, the phase and density fluctuations of the boson variable on each site of the optical lattice describe the vector potential and the electric field on each link of the gauge-model lattice, respectively. The target gauge model is different from the standard Wilson-type U(1) gauge-Higgs model because it has plaquette and Higgs interactions with asymmetric couplings in the space-time directions. Nevertheless, the corresponding quantum simulation is still important as it provides us with a platform to study unexplored time-dependent phenomena characteristic of each phase in the general gauge-Higgs models. To determine the phase diagram of the gauge-Higgs model at zero temperature, we perform Monte Carlo simulations of the corresponding 3+1-dimensional U(1) gauge-Higgs model, and obtain the confinement and Higgs phases. To investigate the dynamical properties of the gauge-Higgs model, we apply the Gross-Pitaevskii equations to the extended Bose-Hubbard model. We simulate the time evolution of an electric flux that initially is put on a straight line connecting two external point charges. We also calculate the potential energy between this pair of charges and obtain the string tension in the confinement phase. Finally, we propose a feasible experimental setup for the atomic simulations of this quantum gauge-Higgs model on the 3D optical lattice. These results may serve as theoretical guides for future experiments.
Prediction of fiber orientation in injection-molded parts using three-dimensional simulations
Wang, Jin; Cook, Peter; Bakharev, Alex; Costa, Franco; Astbury, David
2016-03-01
The Folgar-Tucker (F-T) model is widely used in most commercial software packages and research programs to predict the fiber orientation distribution in injection-molded fiber-reinforced composites. However, experimental measurements reveal that the F-T model normally results in much higher fiber alignment than observed because it tends to over-predict the orientation kinetics. The Reduced Strain Closure (RSC) model was developed, based on the F-T model, to capture the slow orientation kinetics in an objective fashion. Previous studies demonstrate that t he RSC model yields good agreement of fiber orientation with experimental measurements in shell element simulations using the Hele-Shaw flow approximation. This paper focuses on the RSC model in three-dimensional finite element simulations. The fiber orientation predictions were compared to the orientation measurements in a number of injection-molded parts of various shapes and dimensions and molded with various injection speeds. The RSC model is able to capture the orientation distribution through the part thickness and the average orientation trends along the flow length without the need to tailor the inlet orientation condition to pre-existing data.
Two-and Three-Dimensional Simulations of Beetle Hind Wing Flapping during Free Forward Flight
Institute of Scientific and Technical Information of China (English)
Tuyen Quang Le; Tien Van Truong; Hieu Trung Tran; Soo Hyung Park; Jin Hwan Ko; Hoon Cheol Park; Kwang Joon Yoon
2013-01-01
Aerodynamic characteristic of the beetle,Trypoxylus dichotomus,which has a pair of elytra (forewings) and hind wings,is numerically investigated.Based on the experimental results of wing kinematics,two-dimensional (2D) and three-dimensional (3D) computational fluid dynamic simulations were carried out to reveal aerodynamic performance of the hind wing.The roles of the spiral Leading Edge Vortex (LEV) and the spanwise flow were clarified by comparing 2D and 3D simulations.Mainly due to pitching down of chord line during downstroke in highly inclined stroke plane,relatively high averaged thrust was produced in the free forward flight of the beetle.The effects of the local corrugation and the camber variation were also investigated for the beetle's hind wings.Our results show that the camber variation plays a significant role in improving both lift and thrust in the flapping.On the other hand,the local corrugation pattern has no significant effect on the aerodynamic force due to large angle of attack during flapping.
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
In order to study complicated interacting flow field over projectile with lateral jets. External interacting turbulence flow over projectile with lateral jets was numerically simulated firstly in supersonic speed and zero attack angle. The three dimensional Reynolds-averaged NavierStokes equations and implicit finite volume TVD scheme grid of single zone including projectile base was produced by algebraic arithmetic. Body-fitted grid was generated for the lateral nozzle exit successfully so that the nozzle exit can be simulated more accurately. The high Reynolds number two-equation κ-ε turbulence models were used.The main features of the complex flow are captured. The two kinds of flow field over projectile with and without lateral jets are compared from shock structure, pressure of body and base, etc. It shows that lateral jets not only can provide push force, but also change aerodynamics characteristic of projectile significantly. The results are very important for the study of projectile with lateral rocket boosters.``
A Jones matrix formalism for simulating three-dimensional polarized light imaging of brain tissue.
Menzel, M; Michielsen, K; De Raedt, H; Reckfort, J; Amunts, K; Axer, M
2015-10-06
The neuroimaging technique three-dimensional polarized light imaging (3D-PLI) provides a high-resolution reconstruction of nerve fibres in human post-mortem brains. The orientations of the fibres are derived from birefringence measurements of histological brain sections assuming that the nerve fibres—consisting of an axon and a surrounding myelin sheath—are uniaxial birefringent and that the measured optic axis is oriented in the direction of the nerve fibres (macroscopic model). Although experimental studies support this assumption, the molecular structure of the myelin sheath suggests that the birefringence of a nerve fibre can be described more precisely by multiple optic axes oriented radially around the fibre axis (microscopic model). In this paper, we compare the use of the macroscopic and the microscopic model for simulating 3D-PLI by means of the Jones matrix formalism. The simulations show that the macroscopic model ensures a reliable estimation of the fibre orientations as long as the polarimeter does not resolve structures smaller than the diameter of single fibres. In the case of fibre bundles, polarimeters with even higher resolutions can be used without losing reliability. When taking the myelin density into account, the derived fibre orientations are considerably improved. © 2015 The Author(s).
Three-dimensional simulations of nanopowder compaction processes by granular dynamics method
Boltachev, G. Sh.; Lukyashin, K. E.; Shitov, V. A.; Volkov, N. B.
2013-07-01
In order to describe and to study the processes of cold compaction within the discrete element method a three-dimensional model of nanosized powder is developed. The elastic forces of repulsion, the tangential forces of “friction” (Cattaneo-Mindlin), and the dispersion forces of attraction (van der Waals-Hamaker), as well as the formation and destruction of hard bonds between the individual particles are taken into account. The monosized powders with the size of particles in the range 10-40 nm are simulated. The simulation results are compared to the experimental data of the alumina nanopowders compaction. It is shown that the model allows us to reproduce experimental data reliably and, in particular, describes the size effect in the compaction processes. A number of different external loading conditions is used in order to perform the theoretical and experimental researches. The uniaxial compaction (the closed-die compaction), the biaxial (radial) compaction, and the isotropic compaction (the cold isostatic pressing) are studied. The real and computed results are in a good agreement with each other. They reveal a weak sensitivity of the oxide nanopowders to the loading condition (compaction geometry). The application of the continuum theory of the plastically hardening porous body, which is usually used for the description of powders, is discussed.
Simulating three dimensional wave run-up over breakwaters covered by antifer units
Directory of Open Access Journals (Sweden)
A. Najafi-Jilani
2014-06-01
Full Text Available The paper presents the numerical analysis of wave run-up over rubble-mound breakwaters covered by antifer units using a technique integrating Computer-Aided Design (CAD and Computational Fluid Dynamics (CFD software. Direct application of Navier-Stokes equations within armour blocks, is used to provide a more reliable approach to simulate wave run-up over breakwaters. A well-tested Reynolds-averaged Navier-Stokes (RANS Volume of Fluid (VOF code (Flow-3D was adopted for CFD computations. The computed results were compared with experimental data to check the validity of the model. Numerical results showed that the direct three dimensional (3D simulation method can deliver accurate results for wave run-up over rubble mound breakwaters. The results showed that the placement pattern of antifer units had a great impact on values of wave run-up so that by changing the placement pattern from regular to double pyramid can reduce the wave run-up by approximately 30%. Analysis was done to investigate the influences of surface roughness, energy dissipation in the pores of the armour layer and reduced wave run-up due to inflow into the armour and stone layer.
Three-dimensional (3D) printed endovascular simulation models: a feasibility study
Nesbitt, Craig; McCaslin, James; Bagnall, Alan; Davey, Philip; Bose, Pentop; Williams, Rob
2017-01-01
Background Three-dimensional (3D) printing is a manufacturing process in which an object is created by specialist printers designed to print in additive layers to create a 3D object. Whilst there are initial promising medical applications of 3D printing, a lack of evidence to support its use remains a barrier for larger scale adoption into clinical practice. Endovascular virtual reality (VR) simulation plays an important role in the safe training of future endovascular practitioners, but existing VR models have disadvantages including cost and accessibility which could be addressed with 3D printing. Methods This study sought to evaluate the feasibility of 3D printing an anatomically accurate human aorta for the purposes of endovascular training. Results A 3D printed model was successfully designed and printed and used for endovascular simulation. The stages of development and practical applications are described. Feedback from 96 physicians who answered a series of questions using a 5 point Likert scale is presented. Conclusions Initial data supports the value of 3D printed endovascular models although further educational validation is required. PMID:28251121
Mishra, B; Johnson, L C; Kluźniak, W
2016-01-01
We present results of a set of three-dimensional, general relativistic radiation magnetohydro- dynamics simulations of thin accretion discs to test their thermal stability. We consider two cases, one that is initially radiation-pressure dominated and expected to be thermally unstable and another that is initially gas-pressure dominated and expected to remain stable. Indeed, we find that cooling dominates over heating in the radiation-pressure-dominated case, causing the disc to collapse vertically on the local cooling timescale. On the other hand, the gas-pressure- dominated case, which was run for twice as long as the radiation-pressure-dominated case, remains stable, with heating and cooling roughly in balance. Because the radiation-pressure- dominated disc collapses to the point that we are no longer able to resolve it, we had to terminate the simulation. Thus, we do not know for sure whether it might find a much thinner, stable solution or if it will make a transition to unstable expansion and exhibit lim...
A Novel Microgravity Simulator Applicable for Three-Dimensional Cell Culturing
Wuest, Simon L.; Richard, Stéphane; Walther, Isabelle; Furrer, Reinhard; Anderegg, Roland; Sekler, Jörg; Egli, Marcel
2014-10-01
Random Positioning Machines (RPM) were introduced decades ago to simulate microgravity. Since then numerous experiments have been carried out to study its influence on biological samples. The machine is valued by the scientific community involved in space relevant topics as an excellent experimental tool to conduct pre-studies, for example, before sending samples into space. We have developed a novel version of the traditional RPM to broaden its operative range. This novel version has now become interesting to researchers who are working in the field of tissue engineering, particularly those interested in alternative methods for three-dimensional (3D) cell culturing. The main modifications concern the cell culture condition and the algorithm that controls the movement of the frames for the nullification of gravity. An incubator was integrated into the inner frame of the RPM allowing precise control over the cell culture environment. Furthermore, several feed-throughs now allow a permanent supply of gas like CO 2. All these modifications substantially improve conditions to culture cells; furthermore, the rewritten software responsible for controlling the movement of the frames enhances the quality of the generated microgravity. Cell culture experiments were carried out with human lymphocytes on the novel RPM model to compare the obtained response to the results gathered on an older well-established RPM as well as to data from space flights. The overall outcome of the tests validates this novel RPM for cell cultivation under simulated microgravity conditions.
Jiang, Yan-Fei; Stone, James M.; Davis, Shane W.
2014-12-01
We study super-Eddington accretion flows onto black holes using a global three-dimensional radiation magneto-hydrodynamical simulation. We solve the time-dependent radiative transfer equation for the specific intensities to accurately calculate the angular distribution of the emitted radiation. Turbulence generated by the magneto-rotational instability provides self-consistent angular momentum transfer. The simulation reaches inflow equilibrium with an accretion rate ~220 L Edd/c 2 and forms a radiation-driven outflow along the rotation axis. The mechanical energy flux carried by the outflow is ~20% of the radiative energy flux. The total mass flux lost in the outflow is about 29% of the net accretion rate. The radiative luminosity of this flow is ~10 L Edd. This yields a radiative efficiency ~4.5%, which is comparable to the value in a standard thin disk model. In our simulation, vertical advection of radiation caused by magnetic buoyancy transports energy faster than photon diffusion, allowing a significant fraction of the photons to escape from the surface of the disk before being advected into the black hole. We contrast our results with the lower radiative efficiencies inferred in most models, such as the slim disk model, which neglect vertical advection. Our inferred radiative efficiencies also exceed published results from previous global numerical simulations, which did not attribute a significant role to vertical advection. We briefly discuss the implications for the growth of supermassive black holes in the early universe and describe how these results provided a basis for explaining the spectrum and population statistics of ultraluminous X-ray sources.
Energy Technology Data Exchange (ETDEWEB)
Jiang, Yan-Fei [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Stone, James M. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Davis, Shane W. [Canadian Institute for Theoretical Astrophysics. Toronto, ON M5S3H4 (Canada)
2014-12-01
We study super-Eddington accretion flows onto black holes using a global three-dimensional radiation magneto-hydrodynamical simulation. We solve the time-dependent radiative transfer equation for the specific intensities to accurately calculate the angular distribution of the emitted radiation. Turbulence generated by the magneto-rotational instability provides self-consistent angular momentum transfer. The simulation reaches inflow equilibrium with an accretion rate ∼220 L {sub Edd}/c {sup 2} and forms a radiation-driven outflow along the rotation axis. The mechanical energy flux carried by the outflow is ∼20% of the radiative energy flux. The total mass flux lost in the outflow is about 29% of the net accretion rate. The radiative luminosity of this flow is ∼10 L {sub Edd}. This yields a radiative efficiency ∼4.5%, which is comparable to the value in a standard thin disk model. In our simulation, vertical advection of radiation caused by magnetic buoyancy transports energy faster than photon diffusion, allowing a significant fraction of the photons to escape from the surface of the disk before being advected into the black hole. We contrast our results with the lower radiative efficiencies inferred in most models, such as the slim disk model, which neglect vertical advection. Our inferred radiative efficiencies also exceed published results from previous global numerical simulations, which did not attribute a significant role to vertical advection. We briefly discuss the implications for the growth of supermassive black holes in the early universe and describe how these results provided a basis for explaining the spectrum and population statistics of ultraluminous X-ray sources.
Ray-tracing simulations of liquid-crystal gradient-index lenses for three-dimensional displays
Sluijter, M.; Herzog, A.; De Boer, D.K.G.; Krijn, M.P.C.M.; Urbach, P.H.
2009-01-01
For the first time, to our knowledge, we report ray-tracing simulations of an advanced liquid-crystal gradientindex lens structure for application in switchable two-dimensional/three-dimensional (3D) autostereoscopic displays. We present ray-tracing simulations of the angular-dependent lens action.
Lattice simulation of a center symmetric three dimensional effective theory for SU(2) Yang-Mills
Energy Technology Data Exchange (ETDEWEB)
Smith, Dominik
2010-11-17
We present lattice simulations of a center symmetric dimensionally reduced effective field theory for SU(2) Yang Mills which employ thermal Wilson lines and three-dimensional magnetic fields as fundamental degrees of freedom. The action is composed of a gauge invariant kinetic term, spatial gauge fields and a potential for theWilson line which includes a ''fuzzy'' bag term to generate non-perturbative fluctuations between Z(2) degenerate ground states. The model is studied in the limit where the gauge fields are set to zero as well as the full model with gauge fields. We confirm that, at moderately weak coupling, the ''fuzzy'' bag term leads to eigenvalue repulsion in a finite region above the deconfining phase transition which shrinks in the extreme weak-coupling limit. A non-trivial Z(N) symmetric vacuum arises in the confined phase. The effective potential for the Polyakov loop in the theory with gauge fields is extracted from the simulations including all modes of the loop as well as for cooled configurations where the hard modes have been averaged out. The former is found to exhibit a non-analytic contribution while the latter can be described by a mean-field like ansatz with quadratic and quartic terms, plus a Vandermonde potential which depends upon the location within the phase diagram. Other results include the exact location of the phase boundary in the plane spanned by the coupling parameters, correlation lengths of several operators in the magnetic and electric sectors and the spatial string tension. We also present results from simulations of the full 4D Yang-Mills theory and attempt to make a qualitative comparison to the 3D effective theory. (orig.)
Three-dimensional numerical simulation of the 20 June 1991, Orlando microburst
Proctor, Fred H.
1992-01-01
On 20 June 1991, NASA's Boeing 737, equipped with in-situ and look-ahead wind-shear detection systems, made direct low-level penetrations (300-350 m AGL) through a microburst during several stages of its evolution. This microburst was located roughly 20 km northeast of Orlando International Airport and was monitored by a Terminal Doppler Weather Radar (TDWR) located about 10 km south of the airport. The first NASA encounter with this microburst (Event 142), at approximately 2041 UTC, was during its intensification phase. At flight level, in-situ measurements indicated a peak 1-km (averaged) F-factor of approximately 0.1. The second NASA encounter (Event 143) occurred at approximately 2046 UTC, about the time of microburst peak intensity. It was during this penetration that a peak 1-km F-factor of approximately 17 was encountered, which was the largest in-situ measurement of the 1991 summer deployment. By the third encounter (Event 144), at approximately 2051 UTC, the microburst had expanded into a macroburst. During this phase of evolution, an in-situ 1-km F-factor of 0.08 was measured. The focus of this paper is to examine this microburst via numerical simulation from an unsteady, three-dimensional meteorological cloud model. The simulated high-resolution data fields of wind, temperature, radar reflectivity factor, and precipitation are closely examined so as to derive information not readily available from 'observations' and to enhance our understanding of the actual event. Characteristics of the simulated microburst evolution are compared with TDWR and in-situ measurements.
Three-dimensional simulations of turbulent convective mixing in ONe and CO classical nova explosions
Casanova, Jordi; José, Jordi; García-Berro, Enrique; Shore, Steven N.
2016-10-01
Classical novae are thermonuclear explosions that take place in the envelopes of accreting white dwarfs in binary systems. The material piles up under degenerate conditions, driving a thermonuclear runaway. The energy released by the suite of nuclear processes operating at the envelope heats the material up to peak temperatures of (1-4) × 108 K. During these events, about 10-3-10-7 M⊙, enriched in CNO and, sometimes, other intermediate-mass elements (e.g., Ne, Na, Mg, Al) are ejected into the interstellar medium. To account for the gross observational properties of classical novae (in particular, the high concentrations of metals spectroscopically inferred in the ejecta), models require mixing between the (solar-like) material transferred from the secondary and the outermost layers (CO- or ONe-rich) of the underlying white dwarf. Recent multidimensional simulations have demonstrated that Kelvin-Helmholtz instabilities can naturally produce self-enrichment of the accreted envelope with material from the underlying white dwarf at levels that agree with observations. However, the feasibility of this mechanism has been explored in the framework of CO white dwarfs, while mixing with different substrates still needs to be properly addressed. Three-dimensional simulations of mixing at the core-envelope interface during nova outbursts have been performed with the multidimensional code FLASH, for two types of substrates: CO- and ONe-rich. We show that the presence of an ONe-rich substrate, as in "neon novae", yields higher metallicity enhancements in the ejecta than CO-rich substrates (i.e., non-neon novae). A number of requirements and constraints for such 3D simulations (e.g., minimum resolution, size of the computational domain) are also outlined. Movies associated to Fig. 1 are available at http://www.aanda.org
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
A three-dimensional turbulent flow through an entire centrifugal pump is simulated using k-ε turbulence model modified by rotation and curvature, SIMPLEC method and body-fitted coordinate. The velocity and pressure fields are obtained for the pump under various working conditions, which is used to predict the head and hydraulic efficiency of the pump, and the results correspond well with the measured values. The calculation results indicate that the pressure is higher on the pressure side than that on the suction side of the blade; The relative velocity on the suction side gradually decreases from the impeller inlet to the outlet, while increases on the pressure side, it finally results in the lower relative velocity on the suction side and the higher one on the pressure side at the impeller outlet; The impeller flow field is asymmetric, i.e. the velocity and pressure fields are totally different among all channels in the impeller; In the volute, the static pressure gradually increases with the flow route, and a large pressure gratitude occurs in the tongue; Secondary flow exists in the rear part of the spiral.
Three dimensional simulation of giant magneto-impedance effect in thin film structures
Li, Bodong
2011-04-04
In this paper, a three dimensional model for the giant magneto-impedance (GMI) effect in thin film structures is developed using the finite element method(FEM) with a GMI permeability model embedded. One-layer, three-layer, and five-layer thin film structures are simulated. The GMI effect and the sensitivity are calculated as a function of the external magnetic field, driving frequency, and the thickness of the magnetic layers. The results show that the five-layer structure has the best performance, which is in accordance with experimental results. The GMI ratio and the sensitivity first improve with the increasing thickness of the magnetic layer but reach saturation at a certain value of the thickness. In a five-layer structure,saturation of the GMI effect becomes effective at about 3 μm thickness of the magnetic layers, where a GMI ratio of 1125% was obtained, with a corresponding sensitivity of 0.37%/A/m (29.6%/Oe).
a Three-Dimensional Simulation and Visualization System for Uav Photogrammetry
Liang, Y.; Qu, Y.; Cui, T.
2017-08-01
Nowadays UAVs has been widely used for large-scale surveying and mapping. Compared with manned aircraft, UAVs are more cost-effective and responsive. However, UAVs are usually more sensitive to wind condition, which greatly influences their positions and orientations. The flight height of a UAV is relative low, and the relief of the terrain may result in serious occlusions. Moreover, the observations acquired by the Position and Orientation System (POS) are usually less accurate than those acquired in manned aerial photogrammetry. All of these factors bring in uncertainties to UAV photogrammetry. To investigate these uncertainties, a three-dimensional simulation and visualization system has been developed. The system is demonstrated with flight plan evaluation, image matching, POS-supported direct georeferencing, and ortho-mosaicing. Experimental results show that the presented system is effective for flight plan evaluation. The generated image pairs are accurate and false matches can be effectively filtered. The presented system dynamically visualizes the results of direct georeferencing in three-dimensions, which is informative and effective for real-time target tracking and positioning. The dynamically generated orthomosaic can be used in emergency applications. The presented system has also been used for teaching theories and applications of UAV photogrammetry.
Nagaoka, Tomoaki; Watanabe, Soichi
2012-01-01
Electromagnetic simulation with anatomically realistic computational human model using the finite-difference time domain (FDTD) method has recently been performed in a number of fields in biomedical engineering. To improve the method's calculation speed and realize large-scale computing with the computational human model, we adapt three-dimensional FDTD code to a multi-GPU cluster environment with Compute Unified Device Architecture and Message Passing Interface. Our multi-GPU cluster system consists of three nodes. The seven GPU boards (NVIDIA Tesla C2070) are mounted on each node. We examined the performance of the FDTD calculation on multi-GPU cluster environment. We confirmed that the FDTD calculation on the multi-GPU clusters is faster than that on a multi-GPU (a single workstation), and we also found that the GPU cluster system calculate faster than a vector supercomputer. In addition, our GPU cluster system allowed us to perform the large-scale FDTD calculation because were able to use GPU memory of over 100 GB.
Humphries, Stanley; Johnson, Kristin; Rick, Kyle; Liu, Zheng-jun; Goldberg, S. Nahum
2005-04-01
ETherm3 is a finite-element software suite for simulations of electrosurgery and RF thermal ablation processes. Program components cover the complete calculation process from mesh generation to solution analysis. The solutions employ three-dimensional conformal meshes to handle cluster probes and other asymmetric assemblies. The conformal-mesh approach is essential for high-accuracy surface integrals of net electrode currents. ETherm3 performs coupled calculations of RF electric fields in conductive dielectrics and thermal transport via dynamic solutions of the bioheat equation. The boundary-value RF field solution is updated periodically to reflect changes in material properties. ETherm3 features advanced material models with the option for arbitrary temperature variations of thermal and electrical conductivity, perfusion rate, and other quantities. The code handles irreversible changes by switching the material reference of individual elements at specified transition temperatures. ETherm3 is controlled through a versatile interpreter language to enable complex run sequences. The code can automatically maintain constant current or power, switch to different states in response to temperature or impedance information, and adjust parameters on the basis of user-supplied control functions. In this paper, we discuss the physical basis and novel features of the code suite and review application examples.
Pore-scale simulation of fluid flow and solute dispersion in three-dimensional porous media
Icardi, Matteo
2014-07-31
In the present work fluid flow and solute transport through porous media are described by solving the governing equations at the pore scale with finite-volume discretization. Instead of solving the simplified Stokes equation (very often employed in this context) the full Navier-Stokes equation is used here. The realistic three-dimensional porous medium is created in this work by packing together, with standard ballistic physics, irregular and polydisperse objects. Emphasis is placed on numerical issues related to mesh generation and spatial discretization, which play an important role in determining the final accuracy of the finite-volume scheme and are often overlooked. The simulations performed are then analyzed in terms of velocity distributions and dispersion rates in a wider range of operating conditions, when compared with other works carried out by solving the Stokes equation. Results show that dispersion within the analyzed porous medium is adequately described by classical power laws obtained by analytic homogenization. Eventually the validity of Fickian diffusion to treat dispersion in porous media is also assessed. © 2014 American Physical Society.
Three dimensional simulation of a DC free burning arc. Application to lightning physics
Chemartin, L.; Lalande, P.; Montreuil, E.; Delalondre, C.; Chéron, B. G.; Lago, F.
2009-02-01
One of the mechanisms assumed to be involved in the ignition channel cut off is associated with the development of instability. Like any other electric arc, lightning channels become unstable if the provided power is insufficient. In order to study this phenomenon, ONERA in collaboration with EDF has performed 3D simulations of a part of a lightning channel in order to compute the main characteristics of the arc and understand in the future the physical conditions for the ignition of instability. The model, based on the resistive magneto hydro dynamic equations, was adapted to the lightning channel context. In a first step, the results were compared to the experiment of Tanaka et al. [Tanaka, S., Sunabe, K., and Goda, Y., 2000. Three dimensional behaviour analysis of D.C. free arc column by image processing technique, XIII Int'l Conf on Gas Discharges and their applications, Glasgow.] on long electric arcs subjected to continuing current at mean sea level. A good agreement between computations and measurements was found for times greater than tens of millisecond. Results also showed that the internal resistance continuously decreases with time. Finally, this model was adapted to investigate the effects of altitude on the characteristics of the arc column. Results showed that the effects of altitudes are negligible for altitudes lower than 4 km.
Energy Technology Data Exchange (ETDEWEB)
Seppala, E T; Belak, J; Rudd, R E
2004-09-02
Void coalescence and interaction in dynamic fracture of ductile metals have been investigated using three-dimensional strain-controlled multi-million atom molecular dynamics simulations of copper. The correlated growth of two voids during the coalescence process leading to fracture is investigated, both in terms of its onset and the ensuing dynamical interactions. Void interactions are quantified through the rate of reduction of the distance between the voids, through the correlated directional growth of the voids, and through correlated shape evolution of the voids. The critical inter-void ligament distance marking the onset of coalescence is shown to be approximately one void radius based on the quantification measurements used, independent of the initial separation distance between the voids and the strain-rate of the expansion of the system. The interaction of the voids is not reflected in the volumetric asymptotic growth rate of the voids, as demonstrated here. Finally, the practice of using a single void and periodic boundary conditions to study coalescence is examined critically and shown to produce results markedly different than the coalescence of a pair of isolated voids.
Computational strategies for three-dimensional flow simulations on distributed computer systems
Sankar, Lakshmi N.; Weed, Richard A.
1995-08-01
This research effort is directed towards an examination of issues involved in porting large computational fluid dynamics codes in use within the industry to a distributed computing environment. This effort addresses strategies for implementing the distributed computing in a device independent fashion and load balancing. A flow solver called TEAM presently in use at Lockheed Aeronautical Systems Company was acquired to start this effort. The following tasks were completed: (1) The TEAM code was ported to a number of distributed computing platforms including a cluster of HP workstations located in the School of Aerospace Engineering at Georgia Tech; a cluster of DEC Alpha Workstations in the Graphics visualization lab located at Georgia Tech; a cluster of SGI workstations located at NASA Ames Research Center; and an IBM SP-2 system located at NASA ARC. (2) A number of communication strategies were implemented. Specifically, the manager-worker strategy and the worker-worker strategy were tested. (3) A variety of load balancing strategies were investigated. Specifically, the static load balancing, task queue balancing and the Crutchfield algorithm were coded and evaluated. (4) The classical explicit Runge-Kutta scheme in the TEAM solver was replaced with an LU implicit scheme. And (5) the implicit TEAM-PVM solver was extensively validated through studies of unsteady transonic flow over an F-5 wing, undergoing combined bending and torsional motion. These investigations are documented in extensive detail in the dissertation, 'Computational Strategies for Three-Dimensional Flow Simulations on Distributed Computing Systems', enclosed as an appendix.
Three-dimensional numerical simulation of M2 internal tides in the Luzon Strait
Institute of Scientific and Technical Information of China (English)
LI Bingtian; CAO Anzhou; LV Xianqing
2015-01-01
A three-dimensional isopycnic-coordinate internal tidal model is employed to investigate the generation, propagation, vertical structure and energy conversion of M2 internal tides in the Luzon Strait (LS) with mooring observations. Simulated results, especially the tidal current amplitudes, agree well with observations, demonstrating the reasonability and accuracy of the model. Results indicate that M2 internal tides mainly propagate into three directions horizontally, i.e., eastward towards the western Pacific Ocean, westward towards the Dongsha Island and southwestward towards the South China Sea Basin. In the horizontal direction, tidal current amplitudes decrease as distance increases away from the LS; in the vertical direction, they show an obvious decreasing tendency with depth. Between the double ridges of the LS, a clockwise gyre of M2 baroclinic energy flux appears, which is caused by reflections of M2 internal tides at supercritical topographies, and resonance of M2 internal tides happens along 19.5° and 21.5°N due to the heights and separation distance of the double ridges. The total energy conversion in the LS is about 14.20 GW.
The linear tearing instability in three dimensional, toroidal gyro-kinetic simulations
Energy Technology Data Exchange (ETDEWEB)
Hornsby, W. A., E-mail: william.hornsby@ipp.mpg.de; Migliano, P.; Buchholz, R.; Kroenert, L.; Weikl, A.; Peeters, A. G. [Theoretical Physics V, Department of Physics, Universitaet Bayreuth, Bayreuth D-95447 (Germany); Zarzoso, D.; Poli, E. [Max-Planck-Institut für Plasmaphysik, Boltzmannstrasse 2, D-85748 Garching bei München (Germany); Casson, F. J. [CCFE, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom)
2015-02-15
Linear gyro-kinetic simulations of the classical tearing mode in three-dimensional toroidal geometry were performed using the global gyro-kinetic turbulence code, GKW. The results were benchmarked against a cylindrical ideal MHD and analytical theory calculations. The stability, growth rate, and frequency of the mode were investigated by varying the current profile, collisionality, and the pressure gradients. Both collisionless and semi-collisional tearing modes were found with a smooth transition between the two. A residual, finite, rotation frequency of the mode even in the absence of a pressure gradient is observed, which is attributed to toroidal finite Larmor-radius effects. When a pressure gradient is present at low collisionality, the mode rotates at the expected electron diamagnetic frequency. However, the island rotation reverses direction at high collisionality. The growth rate is found to follow a η{sup 1∕7} scaling with collisional resistivity in the semi-collisional regime, closely following the semi-collisional scaling found by Fitzpatrick. The stability of the mode closely follows the stability analysis as performed by Hastie et al. using the same current and safety factor profiles but for cylindrical geometry, however, here a modification due to toroidal coupling and pressure effects is seen.
THREE-DIMENSIONAL NUMERICAL SIMULATION OF WIND-INDUCED CIRCULATION IN LAKE TAIHU
Institute of Scientific and Technical Information of China (English)
LUO Lian-cong; QIN Bo-qiang
2004-01-01
A three-dimensional (3-D) numerical circulation model for shallow-lake is presented and described in detail in this paper, which employs model-splitting technique in order to calculate water level, mean-depth velocities and horizontal and vertical velocities at different depth simultaneously. The results show the current circulation pattern features four eddies with two clockwise and two anticlockwise induced by prevailing wind. Opposite wind field will lead to opposite current pattern with phase shifted by 180°. The surface convergence zone is located in the upwind area and the surface divergence part in the downwind region, This results in drastic vertical movement in the two zones and the return currents at the bottom with phase shifted by 180°from the surface current vectors. Thus the water level decreases significantly at the leeward side and increases quickly at the windward part. Verification and calibration for the model were made based on the water-level and current data observed during the 9711 Storm in Lake Taihu. The predicted results are in satisfactory agreement with the observed data, which raises the possibility that this model can be used to decide the bottom current stress for sediment resuspension and also to simulate sediment transportation. It can provide a fundamental tool to study the nutrient release from bottom sediment in Lake Taihu.
SASI Activity in Three-Dimensional Neutrino-Hydrodynamics Simulations of Supernova Cores
Hanke, F; Wongwathanarat, A; Marek, A; Janka, H -Th
2013-01-01
The relevance of the standing accretion shock instability (SASI) compared to neutrino-driven convection in three-dimensional (3D) supernova-core environments is still highly controversial. Studying a 27 Msun progenitor, we demonstrate, for the first time, that violent SASI activity can develop in 3D simulations with detailed neutrino transport despite the presence of convection. This result was obtained with the Prometheus-Vertex code with the same sophisticated neutrino treatment so far used only in 1D and 2D models. While buoyant plumes initially determine the nonradial mass motions in the postshock layer, bipolar shock sloshing with growing amplitude sets in during a phase of shock retraction and turns into a violent spiral mode whose growth is only quenched when the infall of the Si/SiO interface leads to strong shock expansion in response to a dramatic decrease of the mass accretion rate. In the phase of large-amplitude SASI sloshing and spiral motions, the postshock layer exhibits nonradial deformation ...
Institute of Scientific and Technical Information of China (English)
Omid Mahabadi; Patrick Kaifosh; Paul Marschall; Tim Vietor
2014-01-01
This study presents the first step of a research project that aims at using a three-dimensional (3D) hybrid finite-discrete element method (FDEM) to investigate the development of an excavation damaged zone (EDZ) around tunnels in a clay shale formation known as Opalinus Clay. The 3D FDEM was first calibrated against standard laboratory experiments, including Brazilian disc test and uniaxial compression test. The effect of increasing confining pressure on the mechanical response and fracture propagation of the rock was quantified under triaxial compression tests. Polyaxial (or true triaxial) simulations highlighted the effect of the intermediate principal stress (s2) on fracture directions in the model: as the intermediate principal stress increased, fractures tended to align in the direction parallel to the plane defined by the major and intermediate principal stresses. The peak strength was also shown to vary with changing s2. ? 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. All rights reserved.
Computational strategies for three-dimensional flow simulations on distributed computer systems
Sankar, Lakshmi N.; Weed, Richard A.
1995-01-01
This research effort is directed towards an examination of issues involved in porting large computational fluid dynamics codes in use within the industry to a distributed computing environment. This effort addresses strategies for implementing the distributed computing in a device independent fashion and load balancing. A flow solver called TEAM presently in use at Lockheed Aeronautical Systems Company was acquired to start this effort. The following tasks were completed: (1) The TEAM code was ported to a number of distributed computing platforms including a cluster of HP workstations located in the School of Aerospace Engineering at Georgia Tech; a cluster of DEC Alpha Workstations in the Graphics visualization lab located at Georgia Tech; a cluster of SGI workstations located at NASA Ames Research Center; and an IBM SP-2 system located at NASA ARC. (2) A number of communication strategies were implemented. Specifically, the manager-worker strategy and the worker-worker strategy were tested. (3) A variety of load balancing strategies were investigated. Specifically, the static load balancing, task queue balancing and the Crutchfield algorithm were coded and evaluated. (4) The classical explicit Runge-Kutta scheme in the TEAM solver was replaced with an LU implicit scheme. And (5) the implicit TEAM-PVM solver was extensively validated through studies of unsteady transonic flow over an F-5 wing, undergoing combined bending and torsional motion. These investigations are documented in extensive detail in the dissertation, 'Computational Strategies for Three-Dimensional Flow Simulations on Distributed Computing Systems', enclosed as an appendix.
Three-Dimensional Hydrodynamic Simulations of Accretion in Short Period Algols
Raymer, Eric
2012-01-01
Recent observations have shown that the direct-impact Algol systems U CrB and RS Vul possess gas located outside of the orbital plane, including a tilted accretion disc in U CrB. Observations of circumstellar gas surrounding the mass donor in RS Vul suggest magnetic effects could be responsible for deflecting the accretion stream out of the orbital plane, resulting in a tilted disc. To determine whether a tilted disc is possible due to a deflected stream, we use three-dimensional hydrodynamic simulations of the mass transfer process in RS Vul. By deflecting the stream 45 degrees out of the orbital plane and boosting the magnitude of the stream's velocity to Mach 30, we mimic the effects of magnetic activity near L1. We find that the modified stream parameters change the direct-impact nature of the system. The stream misses the surface of the star, and a slightly warped accretion disc forms with no more than 3 degrees of disc tilt. The stream-disc interaction for the deflected stream forces a large degree of m...
Three-dimensional lattice Boltzmann model for immiscible two-phase flow simulations.
Liu, Haihu; Valocchi, Albert J; Kang, Qinjun
2012-04-01
We present an improved three-dimensional 19-velocity lattice Boltzmann model for immisicible binary fluids with variable viscosity and density ratios. This model uses a perturbation step to generate the interfacial tension and a recoloring step to promote phase segregation and maintain surfaces. A generalized perturbation operator is derived using the concept of a continuum surface force together with the constraints of mass and momentum conservation. A theoretical expression for the interfacial tension is determined directly without any additional analysis and assumptions. The recoloring algorithm proposed by Latva-Kokko and Rothman is applied for phase segregation, which minimizes the spurious velocities and removes lattice pinning. This model is first validated against the Laplace law for a stationary bubble. It is found that the interfacial tension is predicted well for density ratios up to 1000. The model is then used to simulate droplet deformation and breakup in simple shear flow. We compute droplet deformation at small capillary numbers in the Stokes regime and find excellent agreement with the theoretical Taylor relation for the segregation parameter β=0.7. In the limit of creeping flow, droplet breakup occurs at a critical capillary number 0.35Droplet breakup can also be promoted by increasing the Reynolds number. Finally, we numerically investigate a single bubble rising under buoyancy force in viscous fluids for a wide range of Eötvös and Morton numbers. Numerical results are compared with theoretical predictions and experimental results, and satisfactory agreement is shown.
CFD simulation of fluidization quality in the three-dimensional fluidized bed
Institute of Scientific and Technical Information of China (English)
Kai Zhang; Stefano Brandani; Jicheng Bi; Jianchun Jiang
2008-01-01
Multiphase computational fluid dynamics (CFD) has become an alternative method to experimental investigation for predicting the fluid dynamics in gas-solid fluidized beds. The model of Brandani and Zhang, which contains additional terms in both the gas-and solid-phase momentum equations, is employed to explore homogeneous fluidization of Geldart type A particles and bubbling fluidizatiou Of Geldart type B particles in three-dimensional gas-fluidized beds. In this model, only a correlation for drag force is necessary to close the governing equations. Two kinds of solids, i. e., fine alumina powder (dp=60μm and ρp=1500kg/m3) and sand (dp=610μm and ρp=2500kg/m3), are numerically simulated in a rectangular duct of 0.2m (long)×0.2m (wide) ×0.5m (high) size. The results show good agreement with the classic theory of Geldart.
Three-dimensional Simulation of Thermal Harmonic Lasing FEL with Detuning of the Fundamental
Salehi, Elham; Mirian, Najmeh Sadat
2016-01-01
Detuning of the fundamental is a way to enhance harmonic generation . By this method, the wiggler is composed of two segments in such a way that the fundamental resonance of the second segment to coincide with the third harmonic of the first segment of the wiggler to generate extreme ultraviolet radiation and x-ray emission. A set of coupled, nonlinear, and first-order differential equations in three dimensions describing the evolution of the electron trajectories and the radiation field with warm beam is solved numerically by CYRUS 3D code in the steady-state for two models (1) seeded free electron laser (FEL) and (2) shot noise on the electron beam (self-amplified spontaneous emission FEL). Thermal effects in the form of longitudinal velocity spread is considered. Three-dimensional simulation describes self-consistently the longitudinal spatial dependence of radiation waists, curvatures, and amplitudes together with the evaluation of the electron beam. The evolutions of the transverse modes are investigated...
Modeling and simulations of three-dimensional laser imaging based on space-variant structure
Cao, Jie; Hao, Qun; Peng, Yuxin; Cheng, Yang; Mu, Jiaxing; Wang, Peng; Yu, Haoyong
2016-04-01
A three-dimensional (3D) laser imaging system based on time of flight is proposed, based on the human retina structure. The system obtains 3D images with space-variant resolution, and we further establish mathematical models of the system and carried out simulative comparison between space-variant structure (SVS) and space-invariant structure (SIS). The system based on SVS produces significant improvements over traditional system based on SIS in the following aspects: (1) The system based on SVS uses less pixels than that based on SIS under the same field of view (FOV) and resolution. Therefore, this property is more suitable for uses in situations that require high speed and large volume data processing. (2) The system based on SVS has higher efficiency of utilization of photodiode array than that based on SIS. (3) 3D image based on SVS has the properties of rotation and scaling invariance. (4) The system based on SVS has higher echo power in outside ring of large photodiode array, which is more effective in detecting targets with low reflectance.
Three-dimensional, time-dependent simulation of a regenerative amplifier free-electron laser
Freund, H. P.; Nguyen, D. C.; Sprangle, P. A.; van der Slot, P. J. M.
2013-01-01
Free-electron lasers have been designed to operate over virtually the entire electromagnetic spectrum from microwaves through x rays and in a variety of configurations including amplifiers and oscillators. Oscillators typically operate in the low-gain regime where the full spectral width is (Δω/ω)≈1/Nw and the efficiency η≈1/(2.4Nw). Further, since a low-gain oscillator saturates when the gain compensates for losses in the resonator G=L/(1-L), this implies that the losses must be relatively small and the cavity Q must be relatively large. This imposes problems for high power oscillators because the high Q can result in mirror loading above the damage threshold, and in short-wavelength oscillators because sufficiently low loss resonators may not be possible at x-ray wavelengths. In contrast, regenerative amplifier FELs (RAFELs) employ high-gain wigglers that reach exponential gain and can operate with high loss (i.e., low Q) resonators. As such, RAFELs may be able to function at either high power levels or short wavelengths. In this paper, we describe a three-dimensional, time-dependent simulation of a RAFEL operating at a 2.2-μm wavelength, and show that its behavior differs substantially from that of low-gain oscillators, and is closer to that of self-amplified spontaneous radiation FELs in regard to spectral linewidth and extraction efficiency.
Three-dimensional numerical simulations of three-phase slug flows in horizontal pipes
Wang, Yan; Yang, Junfeng; Matar, Omar
2015-11-01
One of the most common flow regimes in pipelines is that of slug flow: slug bodies corresponding to alternating blocks of aerated liquid which bridge the pipe, separated by elongated bubbles; the latter ride atop a liquid layer. The slugs travel at velocities that exceed the mixture superficial velocity; this can potentially cause structural damage, particularly at pipe bends and junctions. Two-phase slug flows have received considerable attention in the literature both experimentally and computationally but there has been very little work carried out on three-phase slugging. In the present work, the evolution of oil-water-air three-phase slug flow in a horizontal cylindrical pipe is investigated using two-dimensional and three-dimensional computational fluid dynamics simulations. The parameters characterising three-phase slug flow, e.g. slug length, propagation velocity, and slug formation frequency, are determined for various gas and liquid superficial velocities for a given pipe geometry. The results of this work are compared to available experimental data and numerical solutions based on approximate, one-dimensional models relying on the use of empirical correlations. EPSRC Programme Grant, MEMPHIS, EP/K0039761/1.
Clark, D. S.; Weber, C. R.; Milovich, J. L.; Salmonson, J. D.; Kritcher, A. L.; Haan, S. W.; Hammel, B. A.; Hinkel, D. E.; Hurricane, O. A.; Jones, O. S.; Marinak, M. M.; Patel, P. K.; Robey, H. F.; Sepke, S. M.; Edwards, M. J.
2016-05-01
In order to achieve the several hundred Gbar stagnation pressures necessary for inertial confinement fusion ignition, implosion experiments on the National Ignition Facility (NIF) [E. I. Moses et al., Phys. Plasmas 16, 041006 (2009)] require the compression of deuterium-tritium fuel layers by a convergence ratio as high as forty. Such high convergence implosions are subject to degradation by a range of perturbations, including the growth of small-scale defects due to hydrodynamic instabilities, as well as longer scale modulations due to radiation flux asymmetries in the enclosing hohlraum. Due to the broad range of scales involved, and also the genuinely three-dimensional (3D) character of the flow, accurately modeling NIF implosions remains at the edge of current simulation capabilities. This paper describes the current state of progress of 3D capsule-only simulations of NIF implosions aimed at accurately describing the performance of specific NIF experiments. Current simulations include the effects of hohlraum radiation asymmetries, capsule surface defects, the capsule support tent and fill tube, and use a grid resolution shown to be converged in companion two-dimensional simulations. The results of detailed simulations of low foot implosions from the National Ignition Campaign are contrasted against results for more recent high foot implosions. While the simulations suggest that low foot performance was dominated by ablation front instability growth, especially the defect seeded by the capsule support tent, high foot implosions appear to be dominated by hohlraum flux asymmetries, although the support tent still plays a significant role. For both implosion types, the simulations show reasonable, though not perfect, agreement with the data and suggest that a reliable predictive capability is developing to guide future implosions toward ignition.
A New Three-Dimensional Code for Simulation of Ion Beam Extraction: Ion Optics Simulator
Institute of Scientific and Technical Information of China (English)
JIN Dazhi; HUANG Tao; HU Quan; YANG Zhonghai
2008-01-01
A new thee-dimensional code, ion optics simulator (IOS), to simulate ion beam extraction is developed in visual C++ language. The theoretical model, the flowchart of code, and the results of calculation as an example are presented.
SASI ACTIVITY IN THREE-DIMENSIONAL NEUTRINO-HYDRODYNAMICS SIMULATIONS OF SUPERNOVA CORES
Energy Technology Data Exchange (ETDEWEB)
Hanke, Florian; Mueller, Bernhard; Wongwathanarat, Annop; Marek, Andreas; Janka, Hans-Thomas, E-mail: fhanke@mpa-garching.mpg.de, E-mail: bjmuellr@mpa-garching.mpg.de, E-mail: annop@mpa-garching.mpg.de, E-mail: amarek@mpa-garching.mpg.de, E-mail: thj@mpa-garching.mpg.de [Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Str. 1, D-85748 Garching (Germany)
2013-06-10
The relevance of the standing accretion shock instability (SASI) compared to neutrino-driven convection in three-dimensional (3D) supernova-core environments is still highly controversial. Studying a 27 M{sub Sun} progenitor, we demonstrate, for the first time, that violent SASI activity can develop in 3D simulations with detailed neutrino transport despite the presence of convection. This result was obtained with the PROMETHEUS-VERTEX code with the same sophisticated neutrino treatment so far used only in one-dimensional and two-dimensional (2D) models. While buoyant plumes initially determine the nonradial mass motions in the postshock layer, bipolar shock sloshing with growing amplitude sets in during a phase of shock retraction and turns into a violent spiral mode whose growth is only quenched when the infall of the Si/SiO interface leads to strong shock expansion in response to a dramatic decrease of the mass accretion rate. In the phase of large-amplitude SASI sloshing and spiral motions, the postshock layer exhibits nonradial deformation dominated by the lowest-order spherical harmonics (l = 1, m = 0, {+-}1) in distinct contrast to the higher multipole structures associated with neutrino-driven convection. We find that the SASI amplitudes, shock asymmetry, and nonradial kinetic energy in three dimensions can exceed those of the corresponding 2D case during extended periods of the evolution. We also perform parameterized 3D simulations of a 25 M{sub Sun} progenitor, using a simplified, gray neutrino transport scheme, an axis-free Yin-Yang grid, and different amplitudes of random seed perturbations. They confirm the importance of the SASI for another progenitor, its independence of the choice of spherical grid, and its preferred growth for fast accretion flows connected to small shock radii and compact proto-neutron stars as previously found in 2D setups.
Xie, Lianghai; Li, Lei; Zhang, Yiteng; Feng, Yongyong; Wang, Xinyue; Zhang, Aibing; Kong, Linggao
2015-08-01
Lunar minimagnetosphere formed by the interaction between the solar wind and a local crustal field often has a scale size comparable to the ion inertia length, in which the Hall effect is very important. In this paper, the general characteristics of lunar minimagnetosphere are investigated by three-dimensional Hall MHD simulations. It is found that the solar wind ions can penetrate across the magnetopause to reduce the density depletion and cause the merging of the shock and magnetopause, but the electrons are still blocked at the boundary. Besides, asymmetric convection occurs, resulting in the magnetic field piles up on one side while the plasma gathers on the other side. The size of the minimagnetosphere is determined by both the solar zenith angle and the magnetosonic Mach number, while the Hall effect is determined by the ratio of the pressure balance distance to the ion inertia length. When the ratio gets small, the shock may disappear. Finally, we present a global Hall MHD simulation for comparison with the observation from Chang'E-2 satellite on 11 October 2010 and confirm that Chang'E-2 flew across compression regions of two separate minimagnetospheres.
Three-dimensional NDE of VHTR core components via simulation-based testing. Final report
Energy Technology Data Exchange (ETDEWEB)
Guzina, Bojan [Univ. of Minnesota, Minneapolis, MN (United States); Kunerth, Dennis [Idaho National Lab. (INL), Idaho Falls, ID (United States)
2014-09-30
A next generation, simulation-driven-and-enabled testing platform is developed for the 3D detection and characterization of defects and damage in nuclear graphite and composite structures in Very High Temperature Reactors (VHTRs). The proposed work addresses the critical need for the development of high-fidelity Non-Destructive Examination (NDE) technologies for as-manufactured and replaceable in-service VHTR components. Centered around the novel use of elastic (sonic and ultrasonic) waves, this project deploys a robust, non-iterative inverse solution for the 3D defect reconstruction together with a non-contact, laser-based approach to the measurement of experimental waveforms in VHTR core components. In particular, this research (1) deploys three-dimensional Scanning Laser Doppler Vibrometry (3D SLDV) as a means to accurately and remotely measure 3D displacement waveforms over the accessible surface of a VHTR core component excited by mechanical vibratory source; (2) implements a powerful new inverse technique, based on the concept of Topological Sensitivity (TS), for non-iterative elastic waveform tomography of internal defects - that permits robust 3D detection, reconstruction and characterization of discrete damage (e.g. holes and fractures) in nuclear graphite from limited-aperture NDE measurements; (3) implements state-of-the art computational (finite element) model that caters for accurately simulating elastic wave propagation in 3D blocks of nuclear graphite; (4) integrates the SLDV testing methodology with the TS imaging algorithm into a non-contact, high-fidelity NDE platform for the 3D reconstruction and characterization of defects and damage in VHTR core components; and (5) applies the proposed methodology to VHTR core component samples (both two- and three-dimensional) with a priori induced, discrete damage in the form of holes and fractures. Overall, the newly established SLDV-TS testing platform represents a next-generation NDE tool that surpasses
Three dimensional computer simulation for NO{sub x} emission in Oestrand recovery boiler
Energy Technology Data Exchange (ETDEWEB)
Tao Lixin [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Metallurgy
2000-05-01
This report presents the results achieved in a research project (no. 663021) financed by NUTEK and AAFORSK. The objective of this project is to develop and validate a proper NO{sub x} model for black liquor recovery boilers. The project has been carried out through a close co-operation between the division of Heat and Furnace Technology at KTH, the combustion chemistry research group at Aabo Akademi University in Finland and AaF Energikonsult Stockholm AB. As a result from this project, a NO{sub x} model is developed as a new component in the general framework of the recovery boiler model: STAR-RBM. STAR-RBM is a fundamental three-dimensional computer model for the simulation of the flow, heat transfer, combustion and NO{sub x} emission in a black liquor recovery boiler. It is constructed around a general-purpose Computational Fluid Dynamics (CFD) package: STAR-CD. In this report, a three-dimensional numerical simulation for NO{sub x} emission in Oestrand recovery boiler is described and discussed. The NO{sub x} model developed in this project considers the NO formation from fuel-NO and thermal-NO mechanisms. The fuel-NO mechanism is proposed by Aabo Akademi University. It is assumed that the fuel nitrogen in black liquor is released via either devolatilization or char combustion. It has been found by laboratory studies that approximately 70% of the fuel nitrogen is released during devolatilization, mainly as NH{sub 3} and N{sub 2}. The overall gas phase reactions for fuel-NO chemistry is based on that of Mitchell and Tarbell. It has been found in this work that the kinetic rates of the fuel-NO reactions are generally higher than the rate of turbulence mixing. Thus, the eddy dissipation concept proposed by Magnussen and Hjertager is applied to calculate the rate of fuel-NO formation. The thermal-NO mechanism is based on an extended Zeldovich mechanism. Invoking a steady-state approximation for N-atom and assuming that the O-atom concentration may be calculated from
Effective simulation of flexible lateral boundaries in two-and three-dimensional DEM simulations
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
Discrete element method (DEM) models to simulate laboratory element tests play an important role in advancing our understanding of the mechanics of granular material response, including bonded or cemented, particulate materials.Comparisons of the macro-scale response observed in a real physical test and a "virtual" DEM-simulated test can calibrate or validate DEM models.The detailed, particle scale information provided in the DEM simulation can then be used to develop our understanding of the material behaviour.It is important to accurately model the physical test boundary conditions in these DEM simulations.This paper specifically considers triaxial tests as these tests are commonly used in soil mechanics.In a triaxial test,the test specimen of granular material is enclosed within a flexible latex membrane that allows the material to deform freely during testing, while maintaining a specified stress condition. Triaxial tests can only be realistically simulated in 3D DEM codes, however analogue,2D, biaxial DEM simulations are also often considered as it is easier to visualize particle interactions in two dimensions. This paper describes algorithms to simulate the lateral boundary conditions imposed by the latex membrane used in physical triaxial tests in both 2D and 3D DEM simulations.The importance of carefully considering the lateral boundary conditions in DEM simulations is illustrated by considering a 2D biaxial test on a specimen of frictional unbonded disks and a 3D triaxial test on a bonded (cemented) specimen of spheres. The comparisons indicate that the lateral boundary conditions have a more significant influence on the local,particle-scale response in comparison with the overall macro-scale observations.
Zheng, Yuan-Fang
A three-dimensional, five link biped system is established. Newton-Euler state space formulation is employed to derive the equations of the system. The constraint forces involved in the equations can be eliminated by projection onto a smaller state space system for deriving advanced control laws. A model-referenced adaptive control scheme is developed to control the system. Digital computer simulations of point to point movement are carried out to show that the model-referenced adaptive control increases the dynamic range and speeds up the response of the system in comparison with linear and nonlinear feedback control. Further, the implementation of the controller is simpler. Impact effects of biped contact with the environment are modeled and studied. The instant velocity change at the moment of impact is derived as a function of the biped state and contact speed. The effects of impact on the state, as well as constraints are studied in biped landing on heels and toes simultaneously or on toes first. Rate and nonlinear position feedback are employed for stability of the biped after the impact. The complex structure of the foot is properly modeled. A spring and dashpot pair is suggested to represent the action of plantar fascia during the impact. This action prevents the arch of the foot from collapsing. A mathematical model of the skeletal muscle is discussed. A direct relationship between the stimulus rate and the active state is established. A piecewise linear relation between the length of the contractile element and the isometric force is considered. Hill's characteristic equation is maintained for determining the actual output force during different shortening velocities. A physical threshold model is proposed for recruitment which encompasses the size principle, its manifestations and exceptions to the size principle. Finally the role of spindle feedback in stability of the model is demonstrated by study of a pair of muscles.
Hall effect control of magnetotail dawn-dusk asymmetry: A three-dimensional global hybrid simulation
Lu, San; Lin, Y.; Angelopoulos, V.; Artemyev, A. V.; Pritchett, P. L.; Lu, Quanming; Wang, X. Y.
2016-12-01
Magnetotail reconnection and related phenomena (e.g., flux ropes, dipolarizing flux bundles, flow bursts, and particle injections) occur more frequently on the duskside than on the dawnside. Because this asymmetry can directly result in dawn-dusk asymmetric space weather effects, uncovering its physical origin is important for better understanding, modeling, and prediction of the space weather phenomena. However, the cause of this pervasive asymmetry is unclear. Using three-dimensional global hybrid simulations, we demonstrate that the Hall physics in the magnetotail current sheet is responsible for the asymmetry. The current sheet thins progressively under enhanced global convection; when its thickness reaches ion kinetic scales, some ions are decoupled from the magnetized electrons (the Hall effect). The resultant Hall electric field Ez is directed toward the neutral plane. The Hall effect is stronger (grows faster) on the duskside; i.e., more ions become unmagnetized there and do not comove with the magnetized dawnward Ez × Bx drifting electrons, thus creating a larger additional cross-tail current intensity jy (in addition to the diamagnetic current) on the duskside, compared to the dawnside. The stronger Hall effect strength on the duskside is controlled by the higher ion temperature, thinner current sheet, and smaller normal magnetic field Bz there. These asymmetric current sheet properties are in turn controlled by two competing processes that correspond to the Hall effect: (1) the dawnward E × B drift of the magnetic flux and magnetized ions and electrons and (2) the transient motion of the unmagnetized ions which do not execute E × B drift.
Three-dimensional ground-motion simulations of earthquakes for the Hanford area, Washington
Frankel, Arthur; Thorne, Paul; Rohay, Alan
2014-01-01
This report describes the results of ground-motion simulations of earthquakes using three-dimensional (3D) and one-dimensional (1D) crustal models conducted for the probabilistic seismic hazard assessment (PSHA) of the Hanford facility, Washington, under the Senior Seismic Hazard Analysis Committee (SSHAC) guidelines. The first portion of this report demonstrates that the 3D seismic velocity model for the area produces synthetic seismograms with characteristics (spectral response values, duration) that better match those of the observed recordings of local earthquakes, compared to a 1D model with horizontal layers. The second part of the report compares the response spectra of synthetics from 3D and 1D models for moment magnitude (M) 6.6–6.8 earthquakes on three nearby faults and for a dipping plane wave source meant to approximate regional S-waves from a Cascadia great earthquake. The 1D models are specific to each site used for the PSHA. The use of the 3D model produces spectral response accelerations at periods of 0.5–2.0 seconds as much as a factor of 4.5 greater than those from the 1D models for the crustal fault sources. The spectral accelerations of the 3D synthetics for the Cascadia plane-wave source are as much as a factor of 9 greater than those from the 1D models. The differences between the spectral accelerations for the 3D and 1D models are most pronounced for sites with thicker supra-basalt sediments and for stations with earthquakes on the Rattlesnake Hills fault and for the Cascadia plane-wave source.
Energy Technology Data Exchange (ETDEWEB)
Weitzman, Morley
1992-07-15
A three-dimensional finite-element code was developed and used to simulate the flow of groundwater towards an excavation in a saturated porous medium, allowing for seepage faces. An iterative procedure was used to predict the movement of the water table and the seepage flux. The numerical solution agreed well with experimental results from a sandbox experiment. (auth)
Xiang, G.L.; Vire, A.; Pavlidis, D.; Pain, C.
2015-01-01
A three-dimensional fracture model developed in the context of the combined finite-discrete element method is incorporated into a two-way fluid-solid coupling model. The fracture model is capable of simulating the whole fracturing process. It includes pre-peak hardening deformation, post-peak strain
Xu, X L; An, W; Yu, P; Lu, W; Joshi, C; Mori, W B
2016-01-01
The generation of very high quality electron bunches (high brightness and low energy spread) from a plasma-based accelerator in the three-dimensional blowout regime using self-injection in tailored plasma density profiles is analyzed theoretically and with particle-in-cell simulations. The underlying physical mechanism that leads to the generation of high quality electrons is uncovered by tracking the trajectories of the electrons as they cross the sheath and are trapped by the wake. Details on how the intensity of the driver and the density scale-length of the plasma control the ultimate beam quality are described. Three-dimensional particle-in-cell simulations indicate that this concept has the potential to produce beams with peak brightnesses between $10^{20}$ and $10^{21}$ $\\mathrm{A}/\\mathrm{m}^2/\\mathrm{rad}^2$and with absolute projected energy spreads of $\\sim 0.3~\\mathrm{MeV}$ using existing lasers or electron beams to drive nonlinear wakefields.
Seitenzahl, Ivo R.; Kromer, Markus; Ohlmann, Sebastian T.; Ciaraldi-Schoolmann, Franco; Marquardt, Kai; Fink, Michael; Hillebrandt, Wolfgang; Pakmor, Rüdiger; Röpke, Friedrich K.; Ruiter, Ashley J.; Sim, Stuart A.; Taubenberger, Stefan
2016-07-01
The gravitationally confined detonation (GCD) model has been proposed as a possible explosion mechanism for Type Ia supernovae in the single-degenerate evolution channel. It starts with ignition of a deflagration in a single off-centre bubble in a near-Chandrasekhar-mass white dwarf. Driven by buoyancy, the deflagration flame rises in a narrow cone towards the surface. For the most part, the main component of the flow of the expanding ashes remains radial, but upon reaching the outer, low-pressure layers of the white dwarf, an additional lateral component develops. This causes the deflagration ashes to converge again at the opposite side, where the compression heats fuel and a detonation may be launched. We first performed five three-dimensional hydrodynamic simulations of the deflagration phase in 1.4 M⊙ carbon/oxygen white dwarfs at intermediate-resolution (2563 computational zones). We confirm that the closer the initial deflagration is ignited to the centre, the slower the buoyant rise and the longer the deflagration ashes takes to break out and close in on the opposite pole to collide. To test the GCD explosion model, we then performed a high-resolution (5123 computational zones) simulation for a model with an ignition spot offset near the upper limit of what is still justifiable, 200 km. This high-resolution simulation met our deliberately optimistic detonation criteria, and we initiated a detonation. The detonation burned through the white dwarf and led to its complete disruption. For this model, we determined detailed nucleosynthetic yields by post-processing 106 tracer particles with a 384 nuclide reaction network, and we present multi-band light curves and time-dependent optical spectra. We find that our synthetic observables show a prominent viewing-angle sensitivity in ultraviolet and blue wavelength bands, which contradicts observed SNe Ia. The strong dependence on the viewing angle is caused by the asymmetric distribution of the deflagration ashes
Energy Technology Data Exchange (ETDEWEB)
Ham, C. J., E-mail: christopher.ham@ccfe.ac.uk; Chapman, I. T.; Kirk, A.; Saarelma, S. [CCFE, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom)
2014-10-15
It is known that magnetic perturbations can mitigate edge localized modes (ELMs) in experiments, for example, MAST [Kirk et al., Nucl. Fusion 53, 043007 (2013)]. One hypothesis is that the magnetic perturbations cause a three dimensional corrugation of the plasma and this corrugated plasma has different stability properties to peeling-ballooning modes compared to an axisymmetric plasma. It has been shown in an up-down symmetric plasma that magnetic perturbations in tokamaks will break the usual axisymmetry of the plasma causing three dimensional displacements [Chapman et al., Plasma Phys. Controlled Fusion 54, 105013 (2012)]. We produce a free boundary three-dimensional equilibrium of a lower single null MAST relevant plasma using VMEC [S. P. Hirshman and J. C. Whitson, Phys. Fluids 26, 3553 (1983)]. The safety factor and pressure profiles used for the modelling are similar to those deduced from axisymmetric analysis of experimental data with ELMs. We focus on the effect of applying n = 3 and n = 6 magnetic perturbations using the resonant magnetic perturbation (RMP) coils. A midplane displacement of over ±1 cm is seen when the full current is applied. The current in the coils is scanned and a linear relationship between coil current and midplane displacement is found. The pressure gradient in real space in different toroidal locations is shown to change when RMPs are applied. This effect should be taken into account when diagnosing plasmas with RMPs applied. The helical Pfirsch-Schlüter currents which arise as a result of the assumption of nested flux surfaces are estimated for this equilibrium. The effect of this non-axisymmetric equilibrium on infinite n ballooning stability is investigated using COBRA [Sanchez et al., J. Comput. Phys. 161, 576–588 (2000)]. The infinite n ballooning stability is analysed for two reasons; it may give an indication of the effect of non-axisymmetry on finite n peeling-ballooning modes, responsible for ELMs; and
Three-dimensional relativistic pair plasma reconnection with radiative feedback in the Crab Nebula
Energy Technology Data Exchange (ETDEWEB)
Cerutti, B. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Werner, G. R.; Uzdensky, D. A. [Center for Integrated Plasma Studies, Physics Department, University of Colorado, UCB 390, Boulder, CO 80309-0390 (United States); Begelman, M. C., E-mail: bcerutti@astro.princeton.edu, E-mail: greg.werner@colorado.edu, E-mail: uzdensky@colorado.edu, E-mail: mitch@jila.colorado.edu [JILA, University of Colorado and National Institute of Standards and Technology, UCB 440, Boulder, CO 80309-0440 (United States)
2014-02-20
The discovery of rapid synchrotron gamma-ray flares above 100 MeV from the Crab Nebula has attracted new interest in alternative particle acceleration mechanisms in pulsar wind nebulae. Diffuse shock-acceleration fails to explain the flares because particle acceleration and emission occur during a single or even sub-Larmor timescale. In this regime, the synchrotron energy losses induce a drag force on the particle motion that balances the electric acceleration and prevents the emission of synchrotron radiation above 160 MeV. Previous analytical studies and two-dimensional (2D) particle-in-cell (PIC) simulations indicate that relativistic reconnection is a viable mechanism to circumvent the above difficulties. The reconnection electric field localized at X-points linearly accelerates particles with little radiative energy losses. In this paper, we check whether this mechanism survives in three dimension (3D), using a set of large PIC simulations with radiation reaction force and with a guide field. In agreement with earlier works, we find that the relativistic drift kink instability deforms and then disrupts the layer, resulting in significant plasma heating but few non-thermal particles. A moderate guide field stabilizes the layer and enables particle acceleration. We report that 3D magnetic reconnection can accelerate particles above the standard radiation reaction limit, although the effect is less pronounced than in 2D with no guide field. We confirm that the highest-energy particles form compact bunches within magnetic flux ropes, and a beam tightly confined within the reconnection layer, which could result in the observed Crab flares when, by chance, the beam crosses our line of sight.
Three-dimensional Relativistic Pair Plasma Reconnection with Radiative Feedback in the Crab Nebula
Cerutti, B.; Werner, G. R.; Uzdensky, D. A.; Begelman, M. C.
2014-02-01
The discovery of rapid synchrotron gamma-ray flares above 100 MeV from the Crab Nebula has attracted new interest in alternative particle acceleration mechanisms in pulsar wind nebulae. Diffuse shock-acceleration fails to explain the flares because particle acceleration and emission occur during a single or even sub-Larmor timescale. In this regime, the synchrotron energy losses induce a drag force on the particle motion that balances the electric acceleration and prevents the emission of synchrotron radiation above 160 MeV. Previous analytical studies and two-dimensional (2D) particle-in-cell (PIC) simulations indicate that relativistic reconnection is a viable mechanism to circumvent the above difficulties. The reconnection electric field localized at X-points linearly accelerates particles with little radiative energy losses. In this paper, we check whether this mechanism survives in three dimension (3D), using a set of large PIC simulations with radiation reaction force and with a guide field. In agreement with earlier works, we find that the relativistic drift kink instability deforms and then disrupts the layer, resulting in significant plasma heating but few non-thermal particles. A moderate guide field stabilizes the layer and enables particle acceleration. We report that 3D magnetic reconnection can accelerate particles above the standard radiation reaction limit, although the effect is less pronounced than in 2D with no guide field. We confirm that the highest-energy particles form compact bunches within magnetic flux ropes, and a beam tightly confined within the reconnection layer, which could result in the observed Crab flares when, by chance, the beam crosses our line of sight.
Institute of Scientific and Technical Information of China (English)
LIU Hong-min; WANG Ying-rui
2004-01-01
A new method, the stream surface strip element method, for simulating the three-dimensional deformation of plate and strip rolling process was proposed. The rolling deformation zone was divided into a number of stream surface (curved surface) strip elements along metal flow traces, and the stream surface strip elements were mapped into the corresponding plane strip elements for analysis and computation. The longitudinal distributions of the lateral displacement and the altitudinal displacement of metal were respectively constructed to be a quartic curve and a quadratic curve, of which the lateral distributions were expressed as the third-power spline function, and the altitudinal distributions were fitted in the quadratic curve. From the flow theory of plastic mechanics, the mathematical models of the three-dimensional deformations and stresses of the deformation zone were constructed. Compared with the streamline strip element method proposed by the first author of this paper, the stream surface strip element method takes into account the uneven distributions of stresses and deformations along altitudinal direction, and realizes the precise three-dimensional analysis and computation. The simulation example of continuous hot rolled strip indicates that the method and the model accord with facts and provide a new reliable engineering-computation method for the three-dimensional mechanics simulation of plate and strip rolling process.
Montessori, A; Falcucci, G; Prestininzi, P; La Rocca, M; Succi, S
2014-05-01
We investigate the accuracy and performance of the regularized version of the single-relaxation-time lattice Boltzmann equation for the case of two- and three-dimensional lid-driven cavities. The regularized version is shown to provide a significant gain in stability over the standard single-relaxation time, at a moderate computational overhead.
A Jones matrix formalism for simulating three-dimensional polarized light imaging of brain tissue
Menzel, M.; Michielsen, K.; De Raedt, H.; Reckfort, J.; Amunts, K.; Axer, M.
2015-01-01
The neuroimaging technique three-dimensional polarized light imaging (3D-PLI) provides a high-resolution reconstruction of nerve fibres in human post-mortem brains. The orientations of the fibres are derived from birefringence measurements of histological brain sections assuming that the nerve
Schmitz, O.; Becoulet, M.; Cahyna, P.; Evans, T. E.; Feng, Y.; Frerichs, H.; Loarte, A.; Pitts, R. A.; Reiser, D.; Fenstermacher, M. E.; Harting, D.; Kirschner, A.; Kukushkin, A.; Lunt, T.; Saibene, G.; Reiter, D.; Samm, U.; Wiesen, S.
2016-06-01
Results from three-dimensional modeling of plasma edge transport and plasma-wall interactions during application of resonant magnetic perturbation (RMP) fields for control of edge-localized modes in the ITER standard 15 MA Q = 10 H-mode are presented. The full 3D plasma fluid and kinetic neutral transport code EMC3-EIRENE is used for the modeling. Four characteristic perturbed magnetic topologies are considered and discussed with reference to the axisymmetric case without RMP fields. Two perturbation field amplitudes at full and half of the ITER ELM control coil current capability using the vacuum approximation are compared to a case including a strongly screening plasma response. In addition, a vacuum field case at high q 95 = 4.2 featuring increased magnetic shear has been modeled. Formation of a three-dimensional plasma boundary is seen for all four perturbed magnetic topologies. The resonant field amplitudes and the effective radial magnetic field at the separatrix define the shape and extension of the 3D plasma boundary. Opening of the magnetic field lines from inside the separatrix establishes scrape-off layer-like channels of direct parallel particle and heat flux towards the divertor yielding a reduction of the main plasma thermal and particle confinement. This impact on confinement is most accentuated at full RMP current and is strongly reduced when screened RMP fields are considered, as well as for the reduced coil current cases. The divertor fluxes are redirected into a three-dimensional pattern of helical magnetic footprints on the divertor target tiles. At maximum perturbation strength, these fingers stretch out as far as 60 cm across the divertor targets, yielding heat flux spreading and the reduction of peak heat fluxes by 30%. However, at the same time substantial and highly localized heat fluxes reach divertor areas well outside of the axisymmetric heat flux decay profile. Reduced RMP amplitudes due to screening or reduced RMP
Bozkurt, Ozgur; Pennell, Kelly G.; Suuberg, Eric M.
2009-01-01
This paper presents model simulation results of vapor intrusion into structures built atop sites contaminated with volatile or semi-volatile chemicals of concern. A three-dimensional finite element model was used to investigate the importance of factors that could influence vapor intrusion when the site is characterized by non-homogeneous soils. Model simulations were performed to examine how soil layers of differing properties alter soil gas concentration profiles and vapor intrusion rates i...
Stil, J M; Ouyed, R; Taylor, A R
2008-01-01
We present three-dimensional magnetohydrodynamic (MHD) simulations of superbubbles, to study the importance of MHD effects in the interpretation of images from recent surveys of the Galactic plane. These simulations focus mainly on atmospheres defined by an exponential density distribution and the Dickey & Lockman (1990) density distribution. In each case, the magnetic field is parallel to the Galactic plane and we investigate cases with either infinite scale height (constant magnetic field) or a constant ratio of gas pressure to magnetic pressure. The three-dimensional structure of superbubbles in these simulations is discussed with emphasis on the axial ratio of the cavity as a function of magnetic field strength and the age of the bubble. We investigate systematic errors in the age of the bubble and scale height of the surrounding medium that may be introduced by modeling the data with purely hydrodynamic models. Age estimates derived with symmetric hydrodynamic models fitted to an asymmetric magnetize...
Three-dimensional finite element simulation of intermingled-fiber hybrid composite behavior
Mital, Subodh K.; Chamis, Christos C.
1992-01-01
Three-dimensional finite element methods and the intraply hybrid micromechanics equations are used to predict composite properties for a unidirectional graphite-epoxy primary composite with S-glass fibers used as hybridizing fibers. The micromechanics equations are embedded in a computer code ICAN (Integrated Composites Analyzer). The three-dimensional finite element model consists of three-by-three unit cell array, with a total fiber volume ratio of 0.54. There is a good agreement between the composite properties and microstresses obtained from both methods. The results indicate that the finite element methods and micromechanics equations can be used to obtain the properties of intermingled hybrid composites needed for analysis/design of hybrid composite structures.
PARALLEL ALGORITHM FOR THREE-DIMENSIONAL STOKES FLOW SIMULATION USING BOUNDARY ELEMENT METHOD
Directory of Open Access Journals (Sweden)
D. G. Pribytok
2016-01-01
Full Text Available Parallel computing technique for modeling three-dimensional viscous flow (Stokes flow using direct boundary element method is presented. The problem is solved in three phases: sampling and construction of system of linear algebraic equations (SLAE, its decision and finding the velocity of liquid at predetermined points. For construction of the system and finding the velocity, the parallel algorithms using graphics CUDA cards programming technology have been developed and implemented. To solve the system of linear algebraic equations the implemented software libraries are used. A comparison of time consumption for three main algorithms on the example of calculation of viscous fluid motion in three-dimensional cavity is performed.
Coupled Models and Parallel Simulations for Three-Dimensional Full-Stokes Ice Sheet Modeling
Energy Technology Data Exchange (ETDEWEB)
Zhang, Huai; Ju, Lili
2011-01-01
A three-dimensional full-Stokes computational model is considered for determining the dynamics, temperature, and thickness of ice sheets. The governing thermomechanical equations consist of the three-dimensional full-Stokes system with nonlinear rheology for the momentum, an advective-diffusion energy equation for temperature evolution, and a mass conservation equation for icethickness changes. Here, we discuss the variable resolution meshes, the finite element discretizations, and the parallel algorithms employed by the model components. The solvers are integrated through a well-designed coupler for the exchange of parametric data between components. The discretization utilizes high-quality, variable-resolution centroidal Voronoi Delaunay triangulation meshing and existing parallel solvers. We demonstrate the gridding technology, discretization schemes, and the efficiency and scalability of the parallel solvers through computational experiments using both simplified geometries arising from benchmark test problems and a realistic Greenland ice sheet geometry.
Three-dimensional modeling of the neutral gas depletion effect in a helicon discharge plasma
Kollasch, Jeffrey; Schmitz, Oliver; Norval, Ryan; Reiter, Detlev; Sovinec, Carl
2016-10-01
Helicon discharges provide an attractive radio-frequency driven regime for plasma, but neutral-particle dynamics present a challenge to extending performance. A neutral gas depletion effect occurs when neutrals in the plasma core are not replenished at a sufficient rate to sustain a higher plasma density. The Monte Carlo neutral particle tracking code EIRENE was setup for the MARIA helicon experiment at UW Madison to study its neutral particle dynamics. Prescribed plasma temperature and density profiles similar to those in the MARIA device are used in EIRENE to investigate the main causes of the neutral gas depletion effect. The most dominant plasma-neutral interactions are included so far, namely electron impact ionization of neutrals, charge exchange interactions of neutrals with plasma ions, and recycling at the wall. Parameter scans show how the neutral depletion effect depends on parameters such as Knudsen number, plasma density and temperature, and gas-surface interaction accommodation coefficients. Results are compared to similar analytic studies in the low Knudsen number limit. Plans to incorporate a similar Monte Carlo neutral model into a larger helicon modeling framework are discussed. This work is funded by the NSF CAREER Award PHY-1455210.
An Inexpensive Real-Time Interactive Three Dimensional Flight Simulation System.
1987-06-01
8yatern matriz . The system matrix is a global data structure that is used to transforin coordinates from the three-dimensional world space into the two...15.0; parray [S3111 = 2.0; pearray[31121 = -5.0; lightorient(parray,points,0.0,0.0,0.0, bc ,ly,ls,cmin,cmax,&cl); color(c1); polf(point3,purray
Documentation of finite-difference model for simulation of three-dimensional ground-water flow
Trescott, Peter C.; Larson, S.P.
1976-01-01
User experience has indicated that the documentation of the model of three-dimensional ground-water flow (Trescott and Larson, 1975) should be expanded. This supplement is intended to fulfill that need. The original report emphasized the theory of the strongly implicit procedure, instructions for using the groundwater-flow model, and practical considerations for application. (See also W76-02962 and W76-13085) (Woodard-USGS)
Three-dimensional structures behind Glauert-Goldschmied profile under control of plasma actuation
Prochazka, P.; Uruba, V.
2016-10-01
The effect of plasma dielectric barrier discharge (DBD) to developed boundary layer was investigated previously. It has been shown that plasma actuation can stabilize the flow near to the surface. In the case of streamlined profile, the plasma actuation is able to shift the point of separation and hence to suppress the extent of separation area. This should lead to decrease of the form drag and increasing the total efficiency. An experimental approach is suggested for investigation and time-resolved Particle Image Velocimetry (PIV) is considered as a main measurement technique.
Energy Technology Data Exchange (ETDEWEB)
Fredrich, J.T. [SPE, Richardson, TX (United States); Argueello, J.G.; Thorne, B.J.; Wawersik, W.R. [SPE, Richardson, TX (United States)]|[Sandia National Lab., Albuquerque, NM (United States)] [and others
1996-11-01
This paper describes an integrated geomechanics analysis of well casing damage induced by compaction of the diatomite reservoir at the Belridge Field, California. Historical data from the five field operators were compiled and analyzed to determine correlations between production, injection, subsidence, and well failures. The results of this analysis were used to develop a three-dimensional geomechanical model of South Belridge, Section 33 to examine the diatomite reservoir and overburden response to production and injection at the interwell scale and to evaluate potential well failure mechanisms. The time-dependent reservoir pressure field was derived from a three-dimensional finite difference reservoir simulation and used as input to three-dimensional non-linear finite element geomechanical simulations. The reservoir simulation included -200 wells and covered 18 years of production and injection. The geomechanical simulation contained 437,100 nodes and 374,130 elements with the overburden and reservoir discretized into 13 layers with independent material properties. The results reveal the evolution of the subsurface stress and displacement fields with production and injection and suggest strategies for reducing the occurrence of well casing damage.
Hase, Kazunori; Yokoi, Takashi
In the present study, the computer simulation technique to autonomously generate running motion from walking was developed using a three-dimensional entire-body neuro-musculo-skeletal model. When maximizing locomotive speed was employed as the evaluative criterion, the initial walking pattern could not transition to a valid running motion. When minimizing the period of foot-ground contact was added to this evaluative criterion, the simulation model autonomously produced appropriate three-dimensional running. Changes in the neuronal system showed the fatigue coefficient of the neural oscillators to reduce as locomotion patterns transitioned from walking to running. Then, when the running speed increased, the amplitude of the non-specific stimulus from the higher center increased. These two changes indicate mean that the improvement in responsiveness of the neuronal system is important for the transition process from walking to running, and that the comprehensive activation level of the neuronal system is essential in the process of increasing running speed.
Song, P. P.; Wei, M. S.; Shi, L.; Ma, C. C.
2013-12-01
Three-dimensional numerical simulations of a scroll expander were performed with dynamic mesh technology. R245fa was selected as the working fluid in the simulations. The PISO algorithm was applied to solve the governing equations with RNG k-ε turbulent model. The distribution and variation of three-dimensional flow field inside the scroll expander were obtained. The research indicates that the flow field is nonuniform and asymmetrical distributions exist inside the expander. Vortex flows also exist in some working chambers. Dynamic clearance leakage flows and inlet orifice throttling have great effects on the flow field distribution. Transient output torque and the mass flux have periodic fluctuations during the working cycles.
Energy Technology Data Exchange (ETDEWEB)
Kuboi, Nobuyuki, E-mail: Nobuyuki.Kuboi@jp.sony.com; Tatsumi, Tetsuya; Kinoshita, Takashi; Shigetoshi, Takushi; Fukasawa, Masanaga; Komachi, Jun; Ansai, Hisahiro [Device and Material Research Group, RDS Platform, Sony Corporation, 4-14-1 Asahi-cho, Atsugi, Kanagawa 243-0014 (Japan)
2015-11-15
The authors modeled SiN film etching with hydrofluorocarbon (CH{sub x}F{sub y}/Ar/O{sub 2}) plasma considering physical (ion bombardment) and chemical reactions in detail, including the reactivity of radicals (C, F, O, N, and H), the area ratio of Si dangling bonds, the outflux of N and H, the dependence of the H/N ratio on the polymer layer, and generation of by-products (HCN, C{sub 2}N{sub 2}, NH, HF, OH, and CH, in addition to CO, CF{sub 2}, SiF{sub 2}, and SiF{sub 4}) as ion assistance process parameters for the first time. The model was consistent with the measured C-F polymer layer thickness, etch rate, and selectivity dependence on process variation for SiN, SiO{sub 2}, and Si film etching. To analyze the three-dimensional (3D) damage distribution affected by the etched profile, the authors developed an advanced 3D voxel model that can predict the time-evolution of the etched profile and damage distribution. The model includes some new concepts for gas transportation in the pattern using a fluid model and the property of voxels called “smart voxels,” which contain details of the history of the etching situation. Using this 3D model, the authors demonstrated metal–oxide–semiconductor field-effect transistor SiN side-wall etching that consisted of the main-etch step with CF{sub 4}/Ar/O{sub 2} plasma and an over-etch step with CH{sub 3}F/Ar/O{sub 2} plasma under the assumption of a realistic process and pattern size. A large amount of Si damage induced by irradiated hydrogen occurred in the source/drain region, a Si recess depth of 5 nm was generated, and the dislocated Si was distributed in a 10 nm deeper region than the Si recess, which was consistent with experimental data for a capacitively coupled plasma. An especially large amount of Si damage was also found at the bottom edge region of the metal–oxide–semiconductor field-effect transistors. Furthermore, our simulation results for bulk fin-type field-effect transistor side-wall etching
Borgia, Andrea; Rutqvist, Jonny; Oldenburg, Curt M.; Hutchings, Lawrence; Garcia, Julio; Walters, Mark; Hartline, Craig; Jeanne, Pierre; Dobson, Patrick; Boyle, Katie
2013-04-01
The Enhanced Geothermal System (EGS) Demonstration Project, currently underway at the Northwest Geysers, California, aims to demonstrate the feasibility of stimulating a deep high-temperature reservoir (up to 400 °C) through water injection over a 2-year period. On October 6, 2011, injection of 25 l/s started from the Prati 32 well at a depth interval of 1850-2699 m below sea level. After a period of almost 2 months, the injection rate was raised to 63 l/s. The flow rate was then decreased to 44 l/s after an additional 3.5 months and maintained at 25 l/s up to August 20, 2012. Significant well-head pressure changes were recorded at Prati State 31 well, which is separated from Prati 32 by about 500 m at reservoir level. More subdued pressure increases occur at greater distances. The water injection caused induced seismicity in the reservoir in the vicinity of the well. Microseismic monitoring and interpretation shows that the cloud of seismic events is mainly located in the granitic intrusion below the injection zone, forming a cluster elongated SSE-NNW (azimuth 170°) that dips steeply to the west. In general, the magnitude of the events increases with depth and the hypocenter depth increases with time. This seismic cloud is hypothesized to correlate with enhanced permeability in the high-temperature reservoir and its variation with time. Based on the existing borehole data, we use the GMS™ GUI to construct a realistic three-dimensional (3D) geologic model of the Northwest Geysers geothermal field. This model includes, from the top down, a low permeability graywacke layer that forms the caprock for the reservoir, an isothermal steam zone (known as the normal temperature reservoir) within metagraywacke, a hornfels zone (where the high-temperature reservoir is located), and a felsite layer that is assumed to extend downward to the magmatic heat source. We then map this model onto a rectangular grid for use with the TOUGH2 multiphase, multicomponent, non
Kulkarni, Akshay K
2008-01-01
We present results of 3D simulations of MHD instabilities at the accretion disk-magnetosphere boundary. The instability is Rayleigh-Taylor, and develops for a fairly broad range of accretion rates and stellar rotation rates and magnetic fields. It produces tall, thin tongues of plasma that penetrate the magnetosphere in the equatorial plane. The shape and number of the tongues changes with time on the inner-disk dynamical timescale. In contrast with funnel flows, which deposit matter mainly in the polar region, the tongues deposit matter much closer to the stellar equator. The instability appears for relatively small misalignment angles, $\\Theta\\lesssim30^\\circ$, between the star's rotation and magnetic axes, and is associated with higher accretion rates. The hot spots and light curves during accretion through instability are generally much more chaotic than during stable accretion. The unstable state of accretion has possible implications for quasi-periodic oscillations and intermittent pulsations from accre...
Kulkarni, Akshay K
2008-01-01
We present results of 3D simulations of MHD instabilities at the accretion disk-magnetosphere boundary. The instability is Rayleigh-Taylor, and develops for a fairly broad range of accretion rates and stellar rotation rates and magnetic fields. It manifests itself in the form of tall, thin tongues of plasma that penetrate the magnetosphere in the equatorial plane. The shape and number of the tongues changes with time on the inner-disk dynamical timescale. In contrast with funnel flows, which deposit matter mainly in the polar region, the tongues deposit matter much closer to the stellar equator. The instability appears for relatively small misalignment angles, $\\Theta\\lesssim30^\\circ$, between the star's rotation and magnetic axes, and is associated with higher accretion rates. The hot spots and light curves during accretion through instability are generally much more chaotic than during stable accretion. The unstable state of accretion has possible implications for quasi-periodic oscillations and intermitten...
Easy, Luke; Omotani, John; Walkden, Nick; Dudson, Benjamin
2015-01-01
The propagation of filaments in the Scrape Off Layer (SOL) of tokamaks largely determine the plasma profiles in the region. In a conduction limited SOL, parallel temperature gradients are expected, such that the resistance to parallel currents is greater at the target than further upstream. Since the perpendicular motion of an isolated filament is largely determined by balance of currents that flow through it, this may be expected to affect filament transport. 3D simulations have thus been used to study the influence of enhanced parallel resistivity on the dynamics of filaments. Filaments with the smallest perpendicular length scales, which were inertially limited at low resistivity (meaning that polarization rather than parallel currents determine their radial velocities), were unaffected by resistivity. For larger filaments, faster velocities were produced at higher resistivities, due to two mechanisms. Firstly parallel currents were reduced and polarization currents were enhanced, meaning that the inertial...
Three-dimensional gyrokinetic simulation of the relaxation of a magnetized temperature filament
Sydora, R. D.; Morales, G. J.; Maggs, J. E.; Van Compernolle, B.
2015-10-01
An electromagnetic, 3D gyrokinetic particle code is used to study the relaxation of a magnetized electron temperature filament embedded in a large, uniform plasma of lower temperature. The study provides insight into the role played by unstable drift-Alfvén waves observed in a basic electron heat transport experiment [D. C. Pace et al., Phys. Plasmas 15, 122304 (2008)] in which anomalous cross-field transport has been documented. The simulation exhibits the early growth of temperature-gradient-driven, drift-Alfvén fluctuations that closely match the eigenmodes predicted by linear theory. At the onset of saturation, the unstable fluctuations display a spiral spatial pattern, similar to that observed in the laboratory, which causes the rearrangement of the temperature profile. After saturation of the linear instability, the system exhibits a markedly different behavior depending on the inclusion in the computation of modes without variation along the magnetic field, i.e., kz = 0. In their absence, the initial filament evolves into a broadened temperature profile, self-consistent with undamped, finite amplitude drift-Alfvén waves. But the inclusion of kz = 0 modes causes the destruction of the filament and damping of the drift-Alfvén modes leading to a final state consisting of undamped convective cells and multiple, smaller-scale filaments.
Three-dimensional nonlinear theory of travelling wave tubes and simulation
Institute of Scientific and Technical Information of China (English)
李斌; 杨中海
2003-01-01
A three-dimensional (3D) nonlinear theory of travelling wave tubes (TWTs) is developed, which includes a fundamental radio frequency (RF) and harmonics. When the instantaneous bandwidth exceeds an octave, the harmonic is generated and the mutual coupling between the harmonic and the fundamental RF can be observed in TWTs due to nonlinear interaction between the electron beam and the RF. At low frequencies the harmonic has an obvious effect.Based upon Tien's disc model, a plastic 3D super-particle model is proposed to improve the nonlinear analysis of TWTs.Numerical results employing a periodic magnetic focusing field are presented.
Yucesoy, Burcu; Machta, Jonathan; Katzgraber, Helmut G.
2012-02-01
We present the results of a large-scale numerical study of the equilibrium three-dimensional Ising spin glass with Gaussian disorder. Using replica exchange (parallel tempering) Monte Carlo, we measure various static, as well as dynamical quantities, such as the autocorrelation times and round-trip times for the replica exchange Monte Carlo method. The correlation between static and dynamic observables for 5000 disorder realizations (N <=10^3 spins) down to very low temperatures (T 0.2Tc) is examined. Our results show that autocorrelation times are directly correlated with the roughness of the free energy landscape. We also discuss the size dependence of several static quantities.
Three-dimensional numerical simulation of the basic pulse tube refrigerator
Institute of Scientific and Technical Information of China (English)
Wenjing DING; Liang GONG; Yaling HE; Wenquan TAO
2008-01-01
A three-dimensional physical and numerical model of the basic pulse tube refrigerator (PTR) was developed. The compressible and oscillating fluid flow and heat transfer phenomenon in the pulse tube were numerically investigated using a self-developed code. Some cross-section average parameter variations such as velocity, temperature and pressure wave during one cycle were revealed. The variations of velocity and temperature distributions in the pulse tube were also analyzed in detail for further understanding of the working process and refrigeration mechanism of PTRs.
CASE STUDIES OF THREE-DIMENSIONAL NUMERICAL SIMULATION FOR TOTAL SEDIMENT TRANSPORT
Institute of Scientific and Technical Information of China (English)
Hongwei FANG
2003-01-01
The calculation of flow and sediment transport is one of the most important tasks in river engineering. The task is particularly difficult because of the many complex and interacting physical phenomena that need to be accounted for realistically in a model that has predictive power. This paper presents two study cases of three-dimensional calculation, respectively, of suspended sediment transport for the Three Gorges Project on the Yangtze River, China, and of bed load transport on the Elbe River, Germany. The suspended sediment transport calculation and bed load transport calculation are compared with experimental data whenever possible.
Multi-GPU three dimensional Stokes solver for simulating glacier flow
Licul, Aleksandar; Herman, Frédéric; Podladchikov, Yuri; Räss, Ludovic; Omlin, Samuel
2016-04-01
Here we present how we have recently developed a three-dimensional Stokes solver on the GPUs and apply it to a glacier flow. We numerically solve the Stokes momentum balance equations together with the incompressibility equation, while also taking into account strong nonlinearities for ice rheology. We have developed a fully three-dimensional numerical MATLAB application based on an iterative finite difference scheme with preconditioning of residuals. Differential equations are discretized on a regular staggered grid. We have ported it to C-CUDA to run it on GPU's in parallel, using MPI. We demonstrate the accuracy and efficiency of our developed model by manufactured analytical solution test for three-dimensional Stokes ice sheet models (Leng et al.,2013) and by comparison with other well-established ice sheet models on diagnostic ISMIP-HOM benchmark experiments (Pattyn et al., 2008). The results show that our developed model is capable to accurately and efficiently solve Stokes system of equations in a variety of different test scenarios, while preserving good parallel efficiency on up to 80 GPU's. For example, in 3D test scenarios with 250000 grid points our solver converges in around 3 minutes for single precision computations and around 10 minutes for double precision computations. We have also optimized the developed code to efficiently run on our newly acquired state-of-the-art GPU cluster octopus. This allows us to solve our problem on more than 20 million grid points, by just increasing the number of GPU used, while keeping the computation time the same. In future work we will apply our solver to real world applications and implement the free surface evolution capabilities. REFERENCES Leng,W.,Ju,L.,Gunzburger,M. & Price,S., 2013. Manufactured solutions and the verification of three-dimensional stokes ice-sheet models. Cryosphere 7,19-29. Pattyn, F., Perichon, L., Aschwanden, A., Breuer, B., de Smedt, B., Gagliardini, O., Gudmundsson,G.H., Hindmarsh, R
Three-dimensional simulations of ablative hydrodynamic instabilities in indirectly driven targets
Energy Technology Data Exchange (ETDEWEB)
Marinak, M.M.; Tipton, R.E.; Remington, B.A. [and others
1996-06-01
To model ignition in a National Ignition Facility (NIF) capsule implosion, the authors must understand the behavior of instabilities that can cause breakup of the pellet shell. During a capsule implosion, shocks that transit the shell cause growth of perturbations at the surface or at an interface because of a Richtmyer-Meshkov type of instability. Following shock breakout, or earlier for a shaped pulse, the low-density ablated plasma accelerates the pusher, and the ablation front is Rayleigh-Taylor (RT) unstable. Ablation and finite density gradients have the effect of stabilizing the short wavelength modes. Unstable modes present on the outer surface grow and feed through to the inner surface. Once the shell encounters the rebounding shock from the capsule center, it decelerates and the inner surface becomes RT unstable. If perturbations grow large enough, pusher material mixes into the core, degrading implosion performance. Capsule designs for the NIF depend on ablative stabilization and saturation to prevent perturbations initially present on the capsule surface from growing large enough to quench ignition. Here, the authors examine the first simulations and experiments to study the effect of 3-D perturbation shape on instability growth and saturation in indirectly driven targets. The first section discusses HYDRA, the radiation hydrodynamics code developed for these simulations. The subsequent section examines 3-D shape effects in single-mode perturbations in planar foil simulations and experiments. A discussion of the evolution of multimode perturbations on planar foils is followed by a discussion of 3-D simulations of instability growth in Nova capsule implosions.
Institute of Scientific and Technical Information of China (English)
无
2005-01-01
Three-dimensional transient numerical simulation of gas exchange process in a four-stroke motorcycle engine with a semi-spherical combustion chamber with two tilt valves was studied. Combination of the grid re-meshing method and the snapper technique made the valves move smoothly. The flow structure and pattern in a complete engine cycle were described in detail. Tumble ratios around the x-axis and y-axis were analyzed. Comparison of computed pressure with experimental pressure under motored condition revealed that the simulation had high calculation precision; CFD simulation can be regarded as an important tool for resolving the complex aerodynamic behavior in motorcycle engines.
Semi-relativistic hydrodynamics of three-dimensional and low-dimensional quantum plasma
Andreev, Pavel; Kuz'menkov, Leonid
2014-01-01
Contributions of the current-current and Darwin interactions and weak-relativistic addition to kinetic energy in the quantum hydrodynamic equations are considered. Features of hydrodynamic equations for two-dimensional layer of plasma (two-dimensional electron gas for instance) are described. It is shown that the force fields caused by the Darwin interaction and weak-relativistic addition to kinetic energy are partially reduced. Dispersion of three- and two-dimensional semi-relativistic Langmuir waves is calculated.
Three dimensional MHD Modeling of Vertical Kink Oscillations in an Active Region Plasma Curtain
Ofman, Leon; Srivastava, Abhishek K
2015-01-01
Observations on 2011 August 9 of an X6.9-class flare in active region (AR) 11263 by the Atmospheric Imaging Assembly (AIA) on-board the Solar Dynamics Observatory (SDO), were followed by a rare detection of vertical kink oscillations in a large-scale coronal active region plasma curtain in EUV coronal lines. The damped oscillations with periods in the range 8.8-14.9 min were detected and analyzed recently. Our aim is to study the generation and propagation of the MHD oscillations in the plasma curtain taking into account realistic 3D magnetic and density structure of the curtain. We also aim at testing and improving coronal seismology for more accurate determination of the magnetic field than with standard method. We use the observed morphological and dynamical conditions, as well as plasma properties of the coronal curtain based on Differential Emission Measure (DEM) analysis to initialize a 3D MHD model of its vertical and transverse oscillations by implementing the impulsively excited velocity pulse mimick...
Three dimensional neutronic/thermal-hydraulic coupled simulation of MSR in transient state condition
Energy Technology Data Exchange (ETDEWEB)
Zhou, Jianjun [School of Nuclear Science and Technology, Xi’an Jiaotong University, Xianning Road, 28, Xi’an 710049, Shaanxi (China); College of Mechanical and Power Engineering, China Three Gorges University, No 8, Daxue road, Yichang, Hubei 443002 (China); Zhang, Daling, E-mail: dlzhang@mail.xjtu.edu.cn [School of Nuclear Science and Technology, Xi’an Jiaotong University, Xianning Road, 28, Xi’an 710049, Shaanxi (China); Qiu, Suizheng; Su, Guanghui; Tian, Wenxi; Wu, Yingwei [School of Nuclear Science and Technology, Xi’an Jiaotong University, Xianning Road, 28, Xi’an 710049, Shaanxi (China)
2015-02-15
Highlights: • Developed a three dimensional neutronic/thermal-hydraulic coupled transient analysis code for MSR. • Investigated the neutron distribution and thermal-hydraulic characters of the core under transient condition. • Analyzed three different transient conditions of inlet temperature drop, reactivity jump and pump coastdown. - Abstract: MSR (molten salt reactor) use liquid molten salt as coolant and fuel solvent, which was the only one liquid reactor of six Generation IV reactor types. As a liquid reactor the physical property of reactor was significantly influenced by fuel salt flow and the conventional analysis methods applied in solid fuel reactors are not applicable for this type of reactors. The present work developed a three dimensional neutronic/thermal-hydraulic coupled code investigated the neutronics and thermo-hydraulics characteristics of the core in transient condition based on neutron diffusion theory and numerical heat transfer. The code consists of two group neutron diffusion equations for fast and thermal neutron fluxes and six group balance equations for delayed neutron precursors. The code was separately validated by neutron benchmark and flow and heat transfer benchmark. Three different transient conditions was analyzed with inlet temperature drop, reactivity jump and pump coastdown. The results provide some valuable information in design and research this kind of reactor.
CFD-DEM simulation of three-dimensional aeolian sand movement
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
A three-dimensional CFD-DEM model is proposed to investigate the aeolian sand movement.The results show that the mean particle horizontal velocity can be expressed by a power function of heights.The probability distribution of the impact and lift-off velocities of particles can be described by a log-normal function,and that of the impact and lift-off angles can be expressed by an exponential function.The probability distribution of particle horizontal velocity at different heights can be described as a lognormal function,while the probability distribution of longitudinal and vertical velocity can be described as a normal function.The comparison with previous two-dimensional calculations shows that the variations of mean particle horizontal velocity along the heights in two-dimensional and three-dimensional models are similar.However,the mean particle density of the two-dimensional model is larger than that in reality,which will result in the overestimation of sand transportation rate in the two-dimensional calculation.The study also shows that the predicted probability distributions of particle velocities are in good agreement with the experimental results.
A method for the three-dimensional numerical simulation of superfluid helium
Bottura, L; Patankar, N A; Van Sciver, S W
2009-01-01
Transport phenomena in superfluid helium can be described using the two-fluid Landau-Khalatnikov model and the Gorter-Mellink mutual friction. Here we discuss a mathematical formulation of the two-fluid model that uses macroscopic conservation balances of mass, momentum and energy of each species, and assumes local thermodynamic equilibrium. A particularity of this model is that it describes the state of He II as well as that of each of the two-fluid components in terms of pressure p and temperature T, which is convenient for stable numerical solution. The equations of the model form a system of partial differential equations (PDE) that can be written in matrix form for convenience. On this base, a three-dimensional numerical model using a complete and consistent, while still practical, system of PDEs was developed. In the form described, the PDE can be solved using three-dimensional Lagrangian finite element in space supplemented by a Beam-Warming time-marching algorithm. Once validated, this solver will all...
Three-dimensional Numerical Simulations of Magnetized Winds of Solar-Like Stars
Vidotto, A A; Jatenco-Pereira, V; Gombosi, T I
2009-01-01
By means of self-consistent 3D MHD numerical simulations, we analyze magnetized solar-like stellar winds and their dependence on the plasma-beta parameter. We adopt in our simulations a heating parameter described by gamma, which is responsible for the thermal acceleration of the wind. We analyze winds with polar magnetic field intensities ranging from 1 to 20G. We show that the wind structure presents characteristics that are similar to the solar coronal wind. The steady-state magnetic field topology for all cases is similar, presenting a configuration of helmet streamer-type, with zones of closed field lines and open field lines coexisting. Higher magnetic field intensities lead to faster and hotter winds. The increase of the field intensity generates a larger dead zone in the wind, i. e., the closed loops that inhibit matter to escape from latitudes lower than ~45 degrees extend farther away from the star. The Lorentz force leads naturally to a latitude-dependent wind. We show that by increasing the densit...
Three-dimensional MHD modeling of vertical kink oscillations in an active region plasma curtain
Ofman, L.; Parisi, M.; Srivastava, A. K.
2015-10-01
Context. Observations on 2011 August 9 of an X 6.9-class flare in active region (AR) 11263 by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO), were followed by a rare detection of vertical kink oscillations in a large-scale coronal active region plasma curtain in extreme UV coronal lines with periods in the range 8.8-14.9 min. Aims: Our aim is to study the generation and propagation of the magnetohydrodynamic (MHD) oscillations in the plasma curtain taking the realistic 3D magnetic and the density structure of the curtain into account. We also aim to test and improve coronal seismology for a more accurate determination of the magnetic field than with the standard method. Methods: We use the observed morphological and dynamical conditions, as well as plasma properties of the coronal curtain, to initialize a 3D MHD model of the observed vertical and transverse oscillations. To accomplish this, we implemented the impulsively excited velocity pulse mimicking the flare-generated nonlinear fast magnetosonic propagating disturbance interacting obliquely with the curtain. The model is simplified by utilizing an initial dipole magnetic field, isothermal energy equation, and gravitationally stratified density guided by observational parameters. Results: Using the 3D MHD model, we are able to reproduce the details of the vertical oscillations and study the process of their excitation by a nonlinear fast magnetosonic pulse, propagation, and damping, finding agreement with the observations. Conclusions: We estimate the accuracy of simplified slab-based coronal seismology by comparing the determined magnetic field strength to actual values from the 3D MHD modeling results, and demonstrate the importance of taking more realistic magnetic geometry and density for improving coronal seismology into account. A movie associated to Fig. 1 is available in electronic form at http://www.aanda.org
Three-dimensional photonic crystals created by single-step multi-directional plasma etching.
Suzuki, Katsuyoshi; Kitano, Keisuke; Ishizaki, Kenji; Noda, Susumu
2014-07-14
We fabricate 3D photonic nanostructures by simultaneous multi-directional plasma etching. This simple and flexible method is enabled by controlling the ion-sheath in reactive-ion-etching equipment. We realize 3D photonic crystals on single-crystalline silicon wafers and show high reflectance (>95%) and low transmittance (<-15dB) at optical communication wavelengths, suggesting the formation of a complete photonic bandgap. Moreover, our method simply demonstrates Si-based 3D photonic crystals that show the photonic bandgap effect in a shorter wavelength range around 0.6 μm, where further fine structures are required.
Institute of Scientific and Technical Information of China (English)
Su Xiao-hui; Li C. W.; Chen Bi-hong
2003-01-01
A three-dimensional Large Eddy Simulation (LES) has been performed of hydrodynamic behavior of turbulent flow in open channel that the lower part of the domain is occupied by a drag force layer to represent vegetation.One equation model is used to closing the resolvable scale equations.The turbulent characteristic length is parameterized by a k-l model.A phenomenal model is employed to express the performance of vegetation in the open channel.The result reveals that the present model has the capacity of describing three-dimensional structure of large eddy appearing in turbulent flow in open channel with vegetation region and has the capacity of tracing the development of large eddies.
Finite element simulation of three-dimensional temperature field in underwater welding
Institute of Scientific and Technical Information of China (English)
Liu Xiwen; Wang Guorong; Shi Yonghua; Zhong Jiguang
2007-01-01
Mathematical models of three-dimensional temperature fields in underwater welding with moving heat sources are built. Double ellipsoid Gauss model is proposed as heat sources models. Several factors which affect the temperature fields of underwater welding are analyzed. Water has little influence on thermal efficiency. Water convection coefficient varies with the temperature difference between the water and the workpiece, and water convection makes molten pool freeze quickly. With the increase of water depth, the dimensions of heat sources model should be reduced as arc shrinks. Finite element technology is used to solve mathematical models. ANSYS software is used as finite element tool, and ANSYS Parametric Design Language is used to develop subprograms for loading the moving heat sources and the various convection coefficients. Experiment results show that computational results by using double ellipsoid Gauss heat sources model accord well with the experimental results.
Parallelised direct numerical simulation of three-dimensional wavy falling films
Juric, Damir; Chergui, Jalel; Kahouadji, Lyes; Matar, Omar; Shin, Seungwon
2015-11-01
We present a computational study of falling liquid films in a three-dimensional inclined rectangular domain using the new massively parallel code, BLUE. Calculations are carried out in order to obtain several wave patterns such as occasional solitary waves, which travel downstream at a constant velocity, or less coherent structures. BLUE uses parallelization algorithms based on MPI and algebraic domain decomposition. The velocity field is solved by a parallel GMRES method for the viscous terms and the pressure by a parallel multigrid method. The method for the treatment of the fluid interfaces and capillary forces uses a parallelized Front Tracking/Level Set technique which defines the interface both by a discontinuous density field as well as by a local triangular Lagrangian mesh. This structure allows the interface to undergo large deformations including the rupture and/or coalescence of fluid interfaces. EPSRC Programme Grant, MEMPHIS, EP/K0039761/1.
Application of three-dimensional simulation at lecturing on descriptive geometry
Directory of Open Access Journals (Sweden)
Tel'noy Viktor Ivanovich
2014-05-01
Full Text Available Teaching descriptive geometry has its own characteristics. Need not only to inform students of a certain amount of knowledge on the subject, but also to develop their spatial imagination as well as the right to develop the skills of logical thinking. Practice of teaching the discipline showed that students face serious difficulties in the process of its study. This is due to the relatively low level of their schooling in geometry and technical drawing, and lacking in high spatial imagination. They find it difficult to imagine the geometrical image of the object of study and mentally convert it on the plane. Because of this, there is a need to find ways to effectively teach the discipline «Descriptive Geometry» at university. In the context of global informatization and computerization of the educational process, implementation of graphically programs for the development of design documentation and 3D modeling is one of the most promising applications of information technology in the process of solving these problems. With the help of three-dimensional models the best visibility in the classroom is achieved. When conducting lectures on descriptive geometry it is requested to use three-dimensional modeling not only as didactic means (demonstrativeness means, but also as a method of teaching (learning tool to deal with various graphics tasks. Bearing this in mind, the essence of the implementation of 3D modeling is revealed with the aim of better understanding of the algorithms for solving both positional and metric tasks using spatial representation of graphic constructions. It is shown that the possibility to consider the built model from different angles is of particular importance, as well as the use of transparency properties for illustrating the results of solving geometric problems. Using 3D models together with their display on the plane, as well as text information promotes better assimilation and more lasting memorization of the
Institute of Scientific and Technical Information of China (English)
YUAN YiRang; LIANG Dong; RUI HongXing
2009-01-01
For the three-dimensional seawater intrusion and protection system, the model of dynamics of fluids in porous media and the modified upwind finite difference fractional steps schemes are put forward. Based on the numerical simulation of the practical situation in the Laizhou Bay Area of Shandong Province, predictive numerical simulation and analysis of the consequence of protection projects, un-derground dams, tidal barrage projects and the applied modular form of project adjustment have been finished. By using the theory and techniques of differential equation prior estimates, the convergence results have been got.
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
For the three-dimensional seawater intrusion and protection system, the model of dynamics of fluids in porous media and the modified upwind finite difference fractional steps schemes are put forward. Based on the numerical simulation of the practical situation in the Laizhou Bay Area of Shandong Province, predictive numerical simulation and analysis of the consequence of protection projects, underground dams, tidal barrage projects and the applied modular form of project adjustment have been finished. By using the theory and techniques of differential equation prior estimates, the convergence results have been got.
Three-dimensional photovoltaics
Myers, Bryan; Bernardi, Marco; Grossman, Jeffrey C.
2010-03-01
The concept of three-dimensional (3D) photovoltaics is explored computationally using a genetic algorithm to optimize the energy production in a day for arbitrarily shaped 3D solar cells confined to a given area footprint and total volume. Our simulations demonstrate that the performance of 3D photovoltaic structures scales linearly with height, leading to volumetric energy conversion, and provides power fairly evenly throughout the day. Furthermore, we show that optimal 3D shapes are not simple box-like shapes, and that design attributes such as reflectivity can be optimized in new ways using three-dimensionality.
Tang, Jie; Han, Zhiqiang; Wang, Feifan; Sun, Jue; Xu, Shanxin
A coupled thermo-mechanical simulation method for three-dimensional squeeze casting components has been developed. The simulation was achieved by using ANSYS Parametric Design Language (APDL). The effect of volume shrinkage due to cooling and solidification, the effect of pressure on the latent heat release, the mutual dependence of interfacial heat transfer and casting deformation, and materials behavior under elevated temperatures were taken into account in the simulation. A step-shaped trial casting was simulated, which demonstrates the ability of the method to simulate the pressure transmission and decline inside the casting as well as the distribution and evolution of the interfacial heat transfer coefficient. Finally, the method was applied to simulate the solidification of an automotive sub-frame component, based on which the squeeze casting process of the component was optimized.
Three-dimensional relativistic pair plasma reconnection with radiative feedback in the Crab Nebula
Cerutti, Benoit; Uzdensky, Dmitri A; Begelman, Mitchell C
2013-01-01
The discovery of rapid synchrotron gamma-ray flares above 100 MeV from the Crab Nebula has attracted new interest in alternative particle acceleration mechanisms in pulsar wind nebulae. Diffuse shock-acceleration fails to explain the flares because particle acceleration and emission occur during a single or even sub-Larmor timescale. In this regime, the synchrotron energy losses induce a drag force on the particle motion that balances the electric acceleration and prevents the emission of synchrotron radiation above 160 MeV. Previous analytical studies and 2D particle-in-cell (PIC) simulations indicate that relativistic reconnection is a viable mechanism to circumvent the above difficulties. The reconnection electric field localized at X-points linearly accelerates particles with little radiative energy losses. In this paper, we check whether this mechanism survives in 3D, using a set of large PIC simulations with radiation reaction force and with a guide field. In agreement with earlier works, we find that t...
Vörtler, Horst L; Schäfer, Katja; Smith, William R
2008-04-17
We study the simulation cell size dependence of chemical potential isotherms in subcritical square-well fluids by means of series of canonical ensemble Monte Carlo simulations with increasing numbers of particles, for both three-dimensional bulk systems and two-dimensional planar layers, using Widom-like particle insertion methods. By estimating the corresponding vapor/liquid coexistence densities using a Maxwell-like equal area rule for the subcritical chemical potential isotherms, we are able to study the influence of system size not only on chemical potentials but also on the coexistence properties. The chemical potential versus density isotherms show van der Waals-like loops in the subcritical vapor/liquid coexistence range that exhibit distinct finite size effects for both two- and three-dimensional fluids. Generally, in agreement with recent findings for related studies of Lennard-Jones fluids, the loops shrink with increasing number of particles. In contrast to the subcritical isotherms themselves, the equilibrium vapor/liquid densities show only a weak system size dependence and agree quantitatively with the best-known literature values for three-dimensional fluids. This allows our approach to be used to accurately predict the phase coexistence properties. Our resulting phase equilibrium results for two-dimensional square-well fluids are new. Knowledge concerning finite size effects of square-well systems is important not only for the simulation of thermodynamic properties of simple fluids, but also for the simulation of models of more complex fluids (such as aqueous or polymer fluids) involving square-well interactions.
Institute of Scientific and Technical Information of China (English)
无
1996-01-01
A numerical study of natural convection beat transfer in an inclined cylindrical annulus has been conducted.The inner cylinder of the annulus is maintained at uniform heat flux and the outer cylinder at constant temperature.the two end walls are assumed to be insulated.A numerical code has been developed to calculate the steady state three-dimensional natural convection in an inclined cylindrical annulus,and the research emphasis is placed on the influences of inclination angle α and modified Rayleigh number Ra on the natural convection heat transfer in the annulus.Computations were carried out in the ranges of 0°≤α≤90*,2.5×105≤Ra*≤7and Pr=0.7 with fixed aspect ratio of H=28.97 and radius ratio of K=3.33,The numerical results are compared with the experimental correlations from the literature and the inclination angle effect on heat transfer is found to be insignificant.Detailed results of heat transfer rate,temperature,and velocity fields are presented for the case of α=45° and discussion is also made concerning the comparison between the numerical and experimental results for the specific case of α=90°。
Three-dimensional simulations of thin ferro-fluid films and drops in magnetic fields
Conroy, Devin; Wray, Alex; Matar, Omar
2016-11-01
We consider the interfacial dynamics of a thin, ferrofluidic film flowing down an inclined substrate, under the action of a magnetic field, bounded above by an inviscid gas. The fluid is assumed to be weakly-conducting. Its dynamics are governed by a coupled system of the steady Maxwell's, the Navier-Stokes, and continuity equations. The magnetisation of the film is a function of the magnetic field, and is prescribed by a Langevin function. We make use of a long-wave reduction in order to solve for the dynamics of the pressure, velocity, and magnetic fields inside the film. The potential in the gas phase is solved with the use of Fourier Transforms. Imposition of appropriate interfacial conditions allows for the construction of an evolution equation for the interfacial shape, via use of the kinematic condition, and the magnetic field. We consider the three-dimensional evolution of the film to spawise perturbations by solving the non-linear equations numerically. The constant flux configuration is considered, which corresponds to a thin film and drop flowing down an incline, and a parametric study is performed to understand the effect of a magnetic field on the stability and structure of the formed drops. EPSRC UK platform Grant MACIPh (EP/L020564/1) and programme Grant MEMPHIS (EP/K003976/1).
Three-dimensional numerical simulation of wave interaction with perforated quasi-ellipse caisson
Directory of Open Access Journals (Sweden)
Yong-xue WANG
2011-03-01
Full Text Available The finite difference method and the VOF method have been used to develop a three dimensional numerical model to study wave interaction with a perforated caisson. And the partial cell method is also adopted to this type of problems for the first time. The validity of the present model, with and without the presence of structures, is examined by comparing the model results with experimental data. Then, the numerical model is used to investigate the effects of various wave and structure parameters on the wave forces and the wave runup of the perforated quasi-ellipse caisson. Compared with the solid quasi-ellipse caisson, the wave force of the perforated quasi-ellipse caisson is significantly reduced with the increasing of porosity on the perforated quasi-ellipse caisson. Furthermore, the perforated quasi-ellipse caisson can reduce the wave runup compared with the solid quasi-ellipse caisson. This reduction tends to increase as the porosity of the perforated quasi-ellipse caisson and relative wave height increase.
Lee, Daryl Yao-Wah
A computational fluid dynamics (CFD) procedure has been developed to predict the three-dimensional unsteady flow through a multi-stage axial turbine including the effects of heat transfer. This procedure simultaneously solves the unsteady Reynold's-averaged Navier-Stokes equations for the flow along with the heat conduction equation for the solid. Solution time is minimized through the use of multiple central processing units (CPUs). The blades of the multi-stage turbine move in time and the flow interacts with adjacent vane (stationary) passages through the use of a parallel, sliding-grid, inter-blade-row treatment. Described are the techniques used to solve the governing equations, the inter-blade-row treatment, and the parallelization of the overall approach. The uniqueness of this prediction method lies in the unsteady, multi-stage conjugate solution and the use of multiple combined cores. The approach is validated for the High Impact Technology Turbine designed and tested at the Air Force Research Laboratory.
Temperature Distribution of Three-Dimensional Photovoltaic Panel by Using Finite Element Simulation
Directory of Open Access Journals (Sweden)
Leow Wai Zhe
2016-10-01
Full Text Available The low electricity performance of a photovoltaic (PV panel has been concerned in the PV application system. The effect of environmental and operating condition was affected the performance of the PV panel. In this research work, the main objective is to perform a three-dimensional geometry model of monocrystalline silicon PV panel with and without cooling system by using finite element method. In the case of a cooling system, the effect of the Direct Current (DC fan flow rate on the temperature distribution of PV panel was investigated. The electrical behaviour of this PV panel is obtained based on the average temperature of the PV panel obtained and average solar irradiance from site location. According to the experimental results, PV panel with cooling system can be significant to provide better performance than the PV panel without cooling system in the same environmental condition. For the effect of flow rate of DC fan in the PV panel with cooling system, the performance of this PV panel has been improved as increasing in flow rate of DC fan.
Three-dimensional interpretation of MT data in volcanic environments (computer simulation
Directory of Open Access Journals (Sweden)
V. Spichak
2001-06-01
Full Text Available The research is aimed, first, to find components of MT-fields and their transforms, which facilitate the imaging of the internal structure of volcanoes and, second, to study the detectability of conductivity variations in a magma chamber due to alterations of other physical parameters. The resolving power of MT data with respect to the electric structure of volcanic zones is studied using software developed by the author for three-dimensional (3D numerical modeling, analysis and imaging. A set of 3D volcano models are constructed and synthetic MT data on the relief Earth's surface are analysed. It is found that impedance phases as well as in-phase and quadrature parts of the electric field type transforms enable the best imaging of the volcanic interior. The impedance determinant is, however, the most suitable for adequate interpretation of measurements carried out for the purpose of monitoring conductivity variations in a magma chamber. The way of removing the geological noise from the MT data by means of its upward analytical continuation to the artificial reference plane is discussed. Interpretation methodologies are suggested aimed at 3D imaging and monitoring volcanic interiors by MT data.
Joshi, Shrikrishna Nandkishor; Bolar, Gururaj
2017-06-01
Control of part deflection and deformation during machining of low rigidity thin-wall components is an important aspect in the manufacture of desired quality products. This paper presents a comparative study on the effect of geometry constraints on the product quality during machining of thin-wall components made of an aerospace alloy aluminum 2024-T351. Three-dimensional nonlinear finite element (FE) based simulations of machining of thin-wall parts were carried out by considering three variations in the wall constraint viz. free wall, wall constrained at one end, and wall with constraints at both the ends. Lagrangian formulation based transient FE model has been developed to simulate the interaction between the workpiece and helical milling cutter. Johnson-Cook material and damage model were adopted to account for material behavior during machining process; damage initiation and chip separation. A modified Coulomb friction model was employed to define the contact between the cutting tool and the workpiece. The numerical model was validated with experimental results and found to be in good agreement. Based on the simulation results it was noted that deflection and deformation were maximum in the thin-wall constrained at one end in comparison with those obtained in other cases. It was noted that three dimensional finite element simulations help in a better way to predict the product quality during precision manufacturing of thin-wall components.
Payan, A. P.; Paty, C. S.; Retherford, K. D.
2015-01-01
investigate local magnetospheric processes governing the morphology and variability of Ganymede's aurora depending on its position with respect to the center of the Jovian plasma sheet. We couple an existing three-dimensional multifluid simulation to a new aurora brightness model developed for this study. With this, we are able to qualitatively and quantitatively show that the short- and long-period variabilities observed in Ganymede's auroral footprint at Jupiter are also predicted to be present in the brightness and morphology of the aurora at Ganymede. We also examine the relationship between acceleration structures and precipitation of electrons in Ganymede's neutral atmosphere by looking at the component of the electric field parallel to Ganymede's magnetic field. Our results confirm that regions of electron accelerations coincide with regions of brightest auroral emissions, as expected. Finally, we identify the likely source regions of electrons generating the aurora at Ganymede and discuss the plasma dynamic mechanisms likely responsible for these accelerations.
He, Hui; Cai, Weiping; Lin, Yongxing; Dai, Zhengfei
2011-03-01
A facile and high-throughput strategy is presented to fabricate three-dimensional (3D) hierarchically porous Ag films, with clean surfaces, via plasma etching Ag-coated electrospun nanofiber template. The films are built of Ag porous nanotubes and are homogeneous in macro-size but rough and porous in nanoscale. Each nanotube-block is micro/nanostructured with evenly distributed nanopores on the tube walls. The film architecture (or the shape, arrangement, and distribution density of porous nanotubes; the number and size of nanopores) can be easily controlled by the nanofiber-template configuration, Ag coating, and plasma etching conditions. Such hierarchically porous films could be very useful, such as in catalysis, sensors, and nanodevices. They have exhibited significantly structurally enhanced surface-enhanced Raman scattering performance with good stability and reproduction, and shown the possibility of molecule-level detection. Also, the strategy is universal for fabricating other hierarchically structured 3D metal porous films, such as porous Ag hollow sphere arrays.
A Multi-Bunch, Three-Dimensional, Strong-Strong Beam-Beam Simulation Code for Parallel Computers
Energy Technology Data Exchange (ETDEWEB)
Cai, Y.; Kabel, A.C.; /SLAC
2005-05-11
For simulating the strong-strong beam-beam effect, using Particle-In-Cell codes has become one of the methods of choice. While the two-dimensional problem is readily treatable using PC-class machines, the three-dimensional problem, i.e., a problem encompassing hourglass and phase-averaging effects, requires the use of parallel processors. In this paper, we introduce a strong-strong code NIMZOVICH, which was specifically designed for parallel processors and which is optimally used for many bunches and parasitic crossings. We describe the parallelization scheme and give some benchmarking results.
Energy Technology Data Exchange (ETDEWEB)
Yuri, Yosuke, E-mail: yuri.yosuke@jaea.go.jp [Takasaki Advanced Radiation Research Institute, Japan Atomic Energy Agency, 1233 Watanuki-machi Takasaki, Gunma 370-1292 Japan (Japan)
2015-06-29
Three-dimensional (3D) ordering of a charged-particle beams circulating in a storage ring is systematically studied with a molecular-dynamics simulation code. An ion beam can exhibit a 3D ordered configuration at ultralow temperature as a result of powerful 3D laser cooling. Various unique characteristics of the ordered beams, different from those of crystalline beams, are revealed in detail, such as the single-particle motion in the transverse and longitudinal directions, and the dependence of the tune depression and the Coulomb coupling constant on the operating points.
Pranger, C. C.; Le Pourhiet, L.; May, D.; van Dinther, Y.; Gerya, T.
2016-12-01
Subduction zones evolve over millions of years. The state of stress, the distribution of materials, and the strength and structure of the interface between the two plates is intricately tied to a host of time-dependent physical processes, such as damage, friction, (nonlinear) viscous relaxation, and fluid migration. In addition, the subduction interface has a complex three-dimensional geometry that evolves with time and can adjust in response to a changing stress environment or in response to impinging topographical features, and can even branch off as a splay fault. All in all, the behaviour of (large) earthquakes at the millisecond to minute timescale is heavily dependent on the pattern of stress accumulation during the 100 year inter-seismic period, the events occurring on or near the interface in the past thousands of years, as well as the extended geological history of the region. We address the aforementioned modeling requirements by developing a self-consistent 3D staggered grid finite difference continuum description of motion, thermal advection-diffusion, and poro-visco-elastic two-phase flow. Faults are modelled as plastic shear bands that can develop and evolve in response to a changing stress environment without having a prescribed geometry. They obey a Mohr-Coulomb or Drucker-Prager yield criterion and a rate-and-state friction law. For a sound treatment of plasticity, we borrow elements from mechanical engineering, and extend these with high-quality nonlinear iteration schemes and adaptive time-stepping to resolve the rupture process at all time scales. We will present these techniques together with proof-of-concept examples of self-consistently developing seismic cycles in 2D and 3D, including phases of stress accumulation, fault nucleation, dynamic rupture, and healing.
Large-eddy simulation of formation of three-dimensional aeolian sand ripples in a turbulent field
Institute of Scientific and Technical Information of China (English)
2008-01-01
With the method of large-eddy simulation,the equation of spherule motion and the method of immersed boundary condition,numerical simulations of three-dimen-sional turbulent aeolian motion and the formation of sand ripples under three-di-mensional turbulent wind and the mutual actions of saltation and creeping motion were carried out. The resulting sand ripples have the form that is flat on the upwind side and steep on the leeward,which is identical to the sand ripples in nature. We also realized the self-restoration process of three-dimensional sand ripples,which shows the correctness of the method of numerical simulation and the models of saltation and creeping. Finally,We analyzed the influence of sand ripples on the three-dimensional turbulent wind field,and found that due to the appearance and development of sand ripples,in the normal direction of ground there exists stronger energy exchange,and moreover,there is close correspondence between the forms of sand ripples and the vorticity close to the ground surface.
Concept verification of three dimensional free motion simulator for space robot
Okamoto, Osamu; Nakaya, Teruomi; Pokines, Brett
1994-01-01
In the development of automatic assembling technologies for space structures, it is an indispensable matter to investigate and simulate the movements of robot satellites concerned with mission operation. The movement investigation and simulation on the ground will be effectively realized by a free motion simulator. Various types of ground systems for simulating free motion have been proposed and utilized. Some of these methods are a neutral buoyancy system, an air or magnetic suspension system, a passive suspension balance system, and a free flying aircraft or drop tower system. In addition, systems can be simulated by computers using an analytical model. Each free motion simulation method has limitations and well known problems, specifically, disturbance by water viscosity, limited number of degrees-of-freedom, complex dynamics induced by the attachment of the simulation system, short experiment time, and the lack of high speed super-computer simulation systems, respectively. The basic idea presented here is to realize 3-dimensional free motion. This is achieved by combining a spherical air bearing, a cylindrical air bearing, and a flat air bearing. A conventional air bearing system has difficulty realizing free vertical motion suspension. The idea of free vertical suspension is that a cylindrical air bearing and counter balance weight realize vertical free motion. This paper presents a design concept, configuration, and basic performance characteristics of an innovative free motion simulator. A prototype simulator verifies the feasibility of 3-dimensional free motion simulation.
Energy Technology Data Exchange (ETDEWEB)
Zhang, Hai-Feng, E-mail: hanlor@163.com, E-mail: lsb@nuaa.edu.cn [Key Laboratory of Radar Imaging and Microwave Photonics (Nanjing Univ. Aeronaut. Astronaut.), Ministry of Education, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Nanjing Artillery Academy, Nanjing 211132 (China); Liu, Shao-Bin, E-mail: hanlor@163.com, E-mail: lsb@nuaa.edu.cn; Tang, Yi-Jun [Key Laboratory of Radar Imaging and Microwave Photonics (Nanjing Univ. Aeronaut. Astronaut.), Ministry of Education, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China)
2014-06-15
In this paper, the properties of the extraordinary mode and surface plasmon modes in the three-dimensional (3D) magnetized plasma photonic crystals (MPPCs) with face-centered-cubic lattices that are composed of the core tellurium (Te) spheres with surrounded by the homogeneous magnetized plasma shells inserted in the air, are theoretically investigated in detail by the plane wave expansion method, as the magneto-optical Voigt effects of magnetized plasma are considered (the incidence electromagnetic wave vector is perpendicular to the external magnetic field at any time). The optical switching or wavelength division multiplexer can be realized by the proposed 3D MPPCs. Our analyses demonstrate that the complete photonic band gaps (PBGs) and two flatbands regions for the extraordinary mode can be observed obviously. PBGs can be tuned by the radius of core Te sphere, the plasma density and the external magnetic field. The flatbands regions are determined by the existence of surface plasmon modes. Numerical simulations also show that if the thickness of magnetized plasma shell is larger than a threshold value, the band structures of the extraordinary mode will be similar to those obtained from the same structure containing the pure magnetized plasma spheres. In this case, the band structures also will not be affected by the inserted core spheres. It is also provided that the upper edges of two flatbands regions will not depend on the topology of lattice. However, the frequencies of lower edges of two flatbands regions will be convergent to the different constants for different lattices, as the thickness of magnetized plasma shell is close to zero.
Directory of Open Access Journals (Sweden)
Liu Bing
2014-10-01
Full Text Available Earthquake action is the main external factor which influences long-term safe operation of civil construction, especially of the high-rise building. Applying time-history method to simulate earthquake response process of civil construction foundation surrounding rock is an effective method for the anti-knock study of civil buildings. Therefore, this paper develops a civil building earthquake disaster three-dimensional dynamic finite element numerical simulation system. The system adopts the explicit central difference method. Strengthening characteristics of materials under high strain rate and damage characteristics of surrounding rock under the action of cyclic loading are considered. Then, dynamic constitutive model of rock mass suitable for civil building aseismic analysis is put forward. At the same time, through the earthquake disaster of time-history simulation of Shenzhen Children’s Palace, reliability and practicability of system program is verified in the analysis of practical engineering problems.
Nakahata, K; Sugahara, H; Barth, M; Köhler, B; Schubert, F
2016-04-01
When modeling ultrasonic wave propagation in metals, it is important to introduce mesoscopic crystalline structures because the anisotropy of the crystal structure and the heterogeneity of grains disturb ultrasonic waves. In this paper, a three-dimensional (3D) polycrystalline structure generated by multiphase-field modeling was introduced to ultrasonic simulation for nondestructive testing. 3D finite-element simulations of ultrasonic waves were validated and compared with visualization results obtained from laser Doppler vibrometer measurements. The simulation results and measurements showed good agreement with respect to the velocity and front shape of the pressure wave, as well as multiple scattering due to grains. This paper discussed the applicability of a transversely isotropic approach to ultrasonic wave propagation in a polycrystalline metal with columnar structures.
DEFF Research Database (Denmark)
Poulsen, Stefan Othmar; Voorhees, P.W.; Lauridsen, Erik Mejdal
2013-01-01
The microstructural evolution of a polycrystalline dual-phase material with a constant volume fraction of the phases was investigated using large-scale three-dimensional phase-field simulations. All materials parameters are taken to be isotropic, and microstructures with volume fractions of 50....../50 and 40/60 were examined. After an initial transient, the number of grains decrease from ∼2600 to ∼500. It was found that the mean grain size of grains of both phases obeyed a power law with an exponent of 3, and the microstructural evolution was found to be controlled by diffusion. Steady...... with the topology of single-phase grain structures as determined by experiment and simulation. The evolution of size and number of faces for the minority and majority phase grains in the 40/60 volume fraction simulation is presented and discussed. Non-constant curvature across some interphase boundaries...
High Accuracy Three-dimensional Simulation of Micro Injection Moulded Parts
DEFF Research Database (Denmark)
Tosello, Guido; Costa, F. S.; Hansen, Hans Nørgaard
2011-01-01
Micro injection moulding (μIM) is the key replication technology for high precision manufacturing of polymer micro products. Data analysis and simulations on micro-moulding experiments have been conducted during the present validation study. Detailed information about the μIM process was gathered...... and used to establish a reliable simulation methodology suitable for μIM parts. Various Simulation set-up parameters that have been considered in order to improve the simulation accuracy: injection speed profile, melt and mould temperatures, 3D mesh, material rheology, inertia effect and shrinkage...
Three-dimensional numerical simulation of the exhaust stroke of a single-cylinder four-stroke ICE
Energy Technology Data Exchange (ETDEWEB)
Ogorevc, T.; Sekavcnik, M. [Ljubljana Univ. (Slovenia). Lab. for Heat and Power; Katrasnik, T. [Ljubljana Univ. (Slovenia). Lab. for Internal Combustion Engines; Zun, I. [Ljubljana Univ. (Slovenia). Lab. for Fluid Dynamics and Thermodynamics
2009-09-15
In this paper an extensive CFD simulation of the exhaust stroke of a single-cylinder fourstroke ICE, including the entire exhaust manifold is described. Guidelines for the implementation of the full threedimensional model of the discussed process are included. The simulation involves the time-dependent flow of exhaust gases through the exhaust valve and the flow dynamics within the 2.2-m-long, straight exhaust pipe during the period when the valve is closed. Also the intake port with the intake valve is being coupled during the valves' overlap period. The model geometry corresponds exactly to the actual engine geometry. The movement of the mesh follows the measured kinematics of the piston and the valves. The data obtained from the experimental environment was used for both the initialization and the validation of the computations. It was found that the phenomena affecting the dynamics of the exhaust flow are extremely three-dimensional and should be treated as such. In particular, the flow through the exhaust valve and the heat transfer along the exhaust pipe were influenced greatly by the effects of cold, fresh air breaking into the exhaust pipe in the period after the EVC. The presented study is the basis for future three-dimensional investigations of the entropy-generation rate along the exhaust system, including the exhaust valve. (orig.)
Directory of Open Access Journals (Sweden)
Jinbiao Chen
2014-06-01
Full Text Available The risk level of the Aids to Navigation (AtoNs can reflect the ship navigation safety level in the channel to some extent. In order to appreciate the risk level of the aids to navigation (AtoNs in a navigation channel and to provide some decision-making suggestions for the AtoNs Maintenance and Management Department, the risk assessment index system of the AtoNs was built considering the advanced experience of IALA. Under the Formal Safety Assessment frame, taking the advantages of the fuzzy comprehensive evaluation method, the fuzzy-FSA model of risk assessment for aids to navigation was established. The model was implemented for the assessment of aids to navigation in Shanghai area based on the aids to navigation three-dimensional simulation system. The real-time data were extracted from the existing information system of aids to navigation, and the real-time risk assessment for aids to navigation of the chosen channel was performed on platform of the three-dimensional simulation system, with the risk assessment software. Specifically, the deep-water channel of the Yangtze River estuary was taken as an example to illustrate the general assessment procedure. The method proposed presents practical significance and application prospect on the maintenance and management of the aids to navigation.
Accuracy of three-dimensional soft tissue simulation in bimaxillary osteotomies
Liebregts, J.; Xi, T.; Timmermans, M.; Koning, M.J.J. de; Berge, S.J.; Hoppenreijs, T.J.M.; Maal, T.J.
2015-01-01
The purpose of this study was to evaluate the accuracy of an algorithm based on the mass tensor model (MTM) for computerized 3D simulation of soft-tissue changes following bimaxillary osteotomy, and to identify patient and surgery-related factors that may affect the accuracy of the simulation. Sixty
Accuracy of three-dimensional soft tissue simulation in bimaxillary osteotomies
Liebregts, J.; Xi, T.; Timmermans, M.; Koning, M.J.J. de; Berge, S.J.; Hoppenreijs, T.J.M.; Maal, T.J.
2015-01-01
The purpose of this study was to evaluate the accuracy of an algorithm based on the mass tensor model (MTM) for computerized 3D simulation of soft-tissue changes following bimaxillary osteotomy, and to identify patient and surgery-related factors that may affect the accuracy of the simulation. Sixty
Chen, L H; Chen, W H
1999-01-01
The purpose of this study was to use a 3-dimensional (3D) computer-aided design (CAD) simulation system to plan surgical procedures and predict postoperative changes in orthognathic surgery patients. A computer-generated imaging model was developed by combining a 3D reconstructed cephalometric skeletal image and a laser-scanned facial surface image. Moreover, postoperative data were studied and linked to the simulator model for programming and executing simulated surgical procedures. Interactive editing capabilities allow surgeons to operate CAD surgical simulation, and predicted results can be presented graphically and numerically. The results indicate that the integration of 3D images and CAD techniques have a potential for simulating surgery and providing graphic information to patients in obtaining an informed consent.
Three-dimensional simulations of multiple protoplanets embedded in a protostellar disc
Cresswell, Paul; 10.1051/0004-6361:20079178
2008-01-01
Protoplanet eccentricities of e >~ H/r can slow or reverse migration, but previous 2D studies have shown that gravitational scattering cannot maintain significant planet eccentricities against disc-induced damping. We simulate the evolution of low-mass protoplanetary swarms in three dimensions. The aim is to examine both protoplanet survival rates and the dynamical structure of the resulting planetary systems, and to compare them with 2D simulations. We present results from a 3D hydrodynamic simulation of eight protoplanets embedded in a protoplanetary disc. We also present a suite of simulations performed using an N-body code, modified to include prescriptions for planetary migration and for eccentricity and inclination damping. These prescriptions were obtained by fitting analytic formulae to hydrodynamic simulations of planets embedded in discs with initially eccentric and/or inclined orbits. As was found in two dimensions, differential migration produces groups of protoplanets in stable, multiple mean-mot...
Institute of Scientific and Technical Information of China (English)
WANG Cui; ZHANG Xue-qing; SUN Ying-lan
2009-01-01
Based on theory of three-dimensional hydrodynamics,an Euler-Lagrangian particle model is established to study the transport and water exchange capability in the Jiaozhou Bay.The three-dimensional hydrodynamic model,driven by tide and wind,is used to study the effects of wetting and drying of eatuarine intertidal flats by the dry-wet grid technology based on the Estuarine,Coastal and Ocean Model (ECOM).The particle model includes the advection and the diffusion processes,of which the advection process is simulated with a certain method,and the diffusion process is simulated with the random walk method.The effect of the intertidal zone,the turbulent diffusion and the timescales of the water exchange are also discussed.The results show that a moving boundary model can simulate the transport process of the particle in the intertidal zone,where the particles are transported for a longer distance than that of the stationary result.Simulations with and without the turbulent random walk show that the effect of turbulent diffusion is very effective at spreading particles throughout the estuary and speeding up the particle movement.The spatial distribution of residence time is given to quantify the water exchange capability that has very important ramifications to water quality.The effect of wind on the water exchange is also examined and the southeasterly wind in summer tends to block the water exchange near the northeast coast,while the northerly wind in winter speeds up the transport process.These results indicate that the Lagrangian particle model is applicable and has a large potential to help understanding the water exchange capability in estuaries,which can also he useful to simulate the transport process of contaminant.
Directory of Open Access Journals (Sweden)
Tobias Siebert
Full Text Available The vastly increasing number of neuro-muscular simulation studies (with increasing numbers of muscles used per simulation is in sharp contrast to a narrow database of necessary muscle parameters. Simulation results depend heavily on rough parameter estimates often obtained by scaling of one muscle parameter set. However, in vivo muscles differ in their individual properties and architecture. Here we provide a comprehensive dataset of dynamic (n = 6 per muscle and geometric (three-dimensional architecture, n = 3 per muscle muscle properties of the rabbit calf muscles gastrocnemius, plantaris, and soleus. For completeness we provide the dynamic muscle properties for further important shank muscles (flexor digitorum longus, extensor digitorum longus, and tibialis anterior; n = 1 per muscle. Maximum shortening velocity (normalized to optimal fiber length of the gastrocnemius is about twice that of soleus, while plantaris showed an intermediate value. The force-velocity relation is similar for gastrocnemius and plantaris but is much more bent for the soleus. Although the muscles vary greatly in their three-dimensional architecture their mean pennation angle and normalized force-length relationships are almost similar. Forces of the muscles were enhanced in the isometric phase following stretching and were depressed following shortening compared to the corresponding isometric forces. While the enhancement was independent of the ramp velocity, the depression was inversely related to the ramp velocity. The lowest effect strength for soleus supports the idea that these effects adapt to muscle function. The careful acquisition of typical dynamical parameters (e.g. force-length and force-velocity relations, force elongation relations of passive components, enhancement and depression effects, and 3D muscle architecture of calf muscles provides valuable comprehensive datasets for e.g. simulations with neuro-muscular models, development of more realistic
Eriguchi, Koji
2014-10-01
An increasing demand for high performance field-effect transistors (FETs) leads to the aggressive critical dimension shrinkage and the currently-emerging three dimensional (3D) geometry. Plasma processing is widely used also in the scaled- and 3D-FET (e.g. FinFET) manufacturing, where precise control of the reaction on the (sidewall) surfaces is a prime issue. In this study, damage creation mechanism during plasma etching--plasma-induced physical damage (PPD)--was investigated in such structures on the basis of the PPD range theory, atomistic simulations, and experiments. Compared to PPD in planar FETs (e.g. Si recess [2,3]), a stochastic modeling and atomistic simulations predicted that, during etching of ``fins'' in a 3D-FET, the following two mechanisms are responsible for damage creation in addition to an ion impact on the sidewall at an oblique incident angle: 1) incoming ions penetrate into the Si substrate and undergo scattering by Si atoms in the lateral direction even if the incident angle is normal to the surface and 2) some of Si atoms and ions sputtered at the surface being etched impact on the sidewall with energies sufficient to break Si-Si bonds. These straggling and sputtering processes are stochastic and fundamental, thus, result in 3D structure damage (``fin-damage''). The ``fin-damage'' induced by straggling was modeled by the PPD range theory. Molecular dynamics simulations clarified the mechanisms under the various plasma conditions. Quantum mechanical calculations showed that created defect structures play the role of a carrier trap site, which was experimentally verified by an electrical measurement. Since they are intrinsic natures of etching, both straggling and sputtering noted here should be implemented to design a low-damage etching process. This work was supported in part by Grant-in-Aid for Scientific Research (B) 23360321 from JSPS and STARC project.
Accuracy of three-dimensional soft tissue simulation in bimaxillary osteotomies.
Liebregts, Jeroen; Xi, Tong; Timmermans, Maarten; de Koning, Martien; Bergé, Stefaan; Hoppenreijs, Theo; Maal, Thomas
2015-04-01
The purpose of this study was to evaluate the accuracy of an algorithm based on the mass tensor model (MTM) for computerized 3D simulation of soft-tissue changes following bimaxillary osteotomy, and to identify patient and surgery-related factors that may affect the accuracy of the simulation. Sixty patients (mean age 26.0 years) who had undergone bimaxillary osteotomy, participated in this study. Cone beam CT scans were acquired pre- and one year postoperatively. The 3D rendered pre- and postoperative scans were matched. The maxilla and mandible were segmented and aligned to the postoperative position. 3D distance maps and cephalometric analyses were used to quantify the simulation error. The mean absolute error between the 3D simulation and the actual postoperative facial profile was 0.81 ± 0.22 mm for the face as a whole. The accuracy of the simulation (average absolute error ≤2 mm) for the whole face and for the upper lip, lower lip and chin subregions were 100%, 93%, 90% and 95%, respectively. The predictability was correlated with the magnitude of the maxillary and mandibular advancement, age and V-Y closure. It was concluded that the MTM-based soft tissue simulation for bimaxillary surgery was accurate for clinical use, though patients should be informed of possible variation in the predicted lip position. Copyright © 2014 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Schäfer, Dirk; Schäfer, Wolfgang; Kinzelbach, Wolfgang
1998-05-01
The reactive transport model TBC (transport, biochemistry, and chemistry) numerically solves the equations for reactive transport in three-dimensional saturated groundwater flow. A finite element approximation and a standard Galerkin method are used. Solute transport is coupled to microbially mediated organic carbon degradation. Microbial growth is assumed to follow Monod-type kinetics. Substrate consumption and release of metabolic products is coupled to microbial growth via yield coefficients and stoichiometric relations. Additionally, the effects of microbial activity on selected inorganic chemical species in the aquifer can be considered. TBC allows the user to specify a wide range of possible biochemical and chemical reactions in the input file. This makes TBC a powerful and flexible simulation tool. It was developed to simulate reactive processes related to in situ bioremediation, but further fields of application are laboratory column studies on redox processes coupled to organic carbon degradation, field cases of intrinsic biodegradation, and early diagenetic processes in sediments.
Hase, Kazunori; Obinata, Goro
It is essential for the biomechanical study of human walking motion to consider not only in vivo mechanical load and energy efficiency but also aspects of motor control such as walking stability. In this study, walking stability was investigated using a three-dimensional entire-body neuro-musculo-skeletal model in the computer simulation. In the computational experiments, imaginary constraints, such as no muscular system, were set in the neuro-musculo-skeletal model to investigate their influence on walking stability. The neuronal parameters were adjusted using numerical search techniques in order to adapt walking patterns to constraints on the neuro-musculo-skeletal system. Simulation results revealed that the model of the normal neuro-musculo-skeletal system yielded a higher stability than the imaginary models. Unstable walking by a model with a time delay in the neuronal system suggested significant unknown mechanisms which stabilized walking patterns that have been neglected in previous studies.
Farhaoui, Asma; Kahouadji, Lyes; Chergui, Jalel; Juric, Damir; Shin, Seungwon; Craster, Richard; Matar, Omar
2016-11-01
We carry out three-dimensional numerical simulations of co/counter current Gas-Liquid annular flows using the parallel code, BLUE, based on a projection method for the resolution of the Navier-Stokes equations and a hybrid Front-Tracking/Level-Set method for the interface advection. Gas-Liquid annular flows and falling films in a pipe are present in a broad range of industrial processes. This configuration consists of an important multiphase flow regime where the liquid occupies the area adjacent to the internal circumference of the pipe and the gas flows in the pipe core. Experimentally, four distinctive flow regimes were identified ('dual-wave', 'thick ripple', 'disturbance wave' and 'regular wave' regimes), that we attempt to simulate. In order to visualize these different regimes, various liquid (water) and gas (air) flow-rates are investigated. EPSRC UK Programme Grant EP/K003976/1.
Three-dimensional long-period groundmotion simulations in the upper Mississippi embayment
Macpherson, K.A.; Woolery, E.W.; Wang, Z.; Liu, P.
2010-01-01
We employed a 3D velocity model and 3D wave propagation code to simulate long-period ground motions in the upper Mississippi embayment. This region is at risk from large earthquakes in the New Madrid seismic zone (NMSZ) and observational data are sparse, making simulation a valuable tool for predicting the effects of large events. We undertook these simulations to estimate the magnitude of shaking likely to occur and to investigate the influence of the 3D embayment structure and finite-fault mechanics on ground motions. There exist three primary fault zones in the NMSZ, each of which was likely associated with one of the main shocks of the 1811-12 earthquake triplet. For this study, three simulations have been conducted on each major segment, exploring the impact of different epicentral locations and rupture directions on ground motions. The full wave field up to a frequency of 0.5 Hz is computed on a 200 ?? 200 ?? 50-km 3 volume using a staggered-grid finite-difference code. Peak horizontal velocity and bracketed durations were calculated at the free surface. The NMSZ simulations indicate that for the considered bandwidth, finite-fault mechanics such as fault proximity, directivity effect, and slip distribution exert the most control on ground motions. The 3D geologic structure of the upper Mississippi embayment also influences ground motion with indications that amplification is induced by the sharp velocity contrast at the basin edge.
Xia, J; Samman, N; Yeung, R W; Shen, S G; Wang, D; Ip, H H; Tideman, H
2000-01-01
A new integrated computer system, the 3-dimensional (3D) virtual reality surgical planning and simulation workbench for orthognathic surgery (VRSP), is presented. Five major functions are implemented in this system: post-processing and reconstruction of computed tomographic (CT) data, transformation of 3D unique coordinate system geometry, generation of 3D color facial soft tissue models, virtual surgical planning and simulation, and presurgical prediction of soft tissue changes. The basic mensuration functions, such as linear and spatial measurements, are also included. The surgical planning and simulation are based on 3D CT reconstructions, whereas soft tissue prediction is based on an individualized, texture-mapped, color facial soft tissue model. The surgeon "enters" the virtual operatory with virtual reality equipment, "holds" a virtual scalpel, and "operates" on a virtual patient to accomplish actual surgical planning, simulation of the surgical procedure, and prediction of soft tissue changes before surgery. As a final result, a quantitative osteotomy-simulated bone model and predicted color facial model with photorealistic quality can be visualized from any arbitrary viewing point in a personal computer system. This system can be installed in any hospital for daily use.
Directory of Open Access Journals (Sweden)
Hong Qin
2000-08-01
Full Text Available Collective processes in intense charged particle beams described self-consistently by the Vlasov-Maxwell equations are studied using a 3D multispecies nonlinear perturbative particle simulation method. The newly developed beam equilibrium, stability, and transport (BEST code is used to simulate the nonlinear stability properties of intense beam propagation, surface eigenmodes in a high-intensity beam, and the electron-proton (e-p two-stream instability observed in the Proton Storage Ring (PSR experiment. Detailed simulations in a parameter regime characteristic of the PSR experiment show that the dipole-mode two-stream instability is stabilized by a modest spread (about 0.1% in axial momentum of the beam particles.
Directory of Open Access Journals (Sweden)
Fukushima Kensuke
2017-01-01
Full Text Available Introduction: Periacetabular osteotomy (PAO is an effective joint-preserving procedure for young adults with developmental dysplasia of the hip. Although PAO provides excellent radiographic and clinical results, it is a technically demanding procedure with a distinct learning curve that requires careful 3D planning and, above all, has a number of potential complications. We therefore developed a pre-operative simulation method for PAO via creation of a new full-scale model. Methods: The model was prepared from the patient’s Digital Imaging and Communications in Medicine (DICOM formatted data from computed tomography (CT, for construction and assembly using 3D printing technology. A major feature of our model is that it is constructed from salt. In contrast to conventional models, our model provides a more accurate representation, at a lower manufacturing cost, and requires a shorter production time. Furthermore, our model realized simulated operation normally with using a chisel and drill without easy breakage or fissure. We were able to easily simulate the line of osteotomy and confirm acetabular version and coverage after moving to the osteotomized fragment. Additionally, this model allowed a dynamic assessment that avoided anterior impingement following the osteotomy. Results: Our models clearly reflected the anatomical shape of the patient’s hip. Our models allowed for surgical simulation, making realistic use of the chisel and drill. Our method of pre-operative simulation for PAO allowed for the assessment of accurate osteotomy line, determination of the position of the osteotomized fragment, and prevented anterior impingement after the operation. Conclusion: Our method of pre-operative simulation might improve the safety, accuracy, and results of PAO.
Fukushima, Kensuke; Takahira, Naonobu; Uchiyama, Katsufumi; Moriya, Mitsutoshi; Takaso, Masashi
2017-01-01
Introduction: Periacetabular osteotomy (PAO) is an effective joint-preserving procedure for young adults with developmental dysplasia of the hip. Although PAO provides excellent radiographic and clinical results, it is a technically demanding procedure with a distinct learning curve that requires careful 3D planning and, above all, has a number of potential complications. We therefore developed a pre-operative simulation method for PAO via creation of a new full-scale model. Methods: The model was prepared from the patient’s Digital Imaging and Communications in Medicine (DICOM) formatted data from computed tomography (CT), for construction and assembly using 3D printing technology. A major feature of our model is that it is constructed from salt. In contrast to conventional models, our model provides a more accurate representation, at a lower manufacturing cost, and requires a shorter production time. Furthermore, our model realized simulated operation normally with using a chisel and drill without easy breakage or fissure. We were able to easily simulate the line of osteotomy and confirm acetabular version and coverage after moving to the osteotomized fragment. Additionally, this model allowed a dynamic assessment that avoided anterior impingement following the osteotomy. Results: Our models clearly reflected the anatomical shape of the patient’s hip. Our models allowed for surgical simulation, making realistic use of the chisel and drill. Our method of pre-operative simulation for PAO allowed for the assessment of accurate osteotomy line, determination of the position of the osteotomized fragment, and prevented anterior impingement after the operation. Conclusion: Our method of pre-operative simulation might improve the safety, accuracy, and results of PAO. PMID:28186873
Simulation of three-dimensional viscous flow within a multistage turbine
Adamczyk, John J.; Celestina, Mark L.; Beach, Tim A.; Barnett, Mark
1989-01-01
This work outlines a procedure for simulating the flow field within multistage turbomachinery which includes the effects of unsteadiness, compressibility, and viscosity. The associated modeling equations are the average passage equation system which governs the time-averaged flow field within a typical passage of a blade row embedded within a multistage configuration. The results from a simulation of a low aspect ratio stage and a one-half turbine will be presented and compared with experimental measurements. It will be shown that the secondary flow field generated by the rotor causes the aerodynamic performance of the downstream vane to be significantly different from that of an isolated blade row.
Three dimensional simulations of Richtmyer-Meshkov instabilities in shock-tube experiments
Energy Technology Data Exchange (ETDEWEB)
Gowardhan, Akshay A [Los Alamos National Laboratory; Grinstein, Fernando F [Los Alamos National Laboratory; Wachtor, Adam J [Los Alamos National Laboratory
2010-01-01
In the large eddy simulation (LES) approach large-scale energy-containing structures are resolved, smaller (presumably) more isotropic structures are filtered out, and unresolved subgrid effects are modeled. Extensive recent work has demonstrated that predictive simulations of turbulent velocity fields are possible based on subgrid scale modeling implicitly provided by a class of high-resolution finite-volume algorithms. This strategy is called implicit LES. The extension of the approach to the substantially more difficult problem of material mixing IS addressed, and progress in representative shock-driven turbulent mixing studies is reported.
Peng, Shiqiu; Zeng, Xuezhi; Li, Zhijin
2016-05-01
A three-dimensional variational data assimilation (3DVAR) system based on the Regional Ocean Modeling System (ROMS) is established for the South China Sea (SCS). A set of Observing System Simulation Experiments (OSSEs) are performed to evaluate the performance of this data assimilation system and investigate the impacts of different types of observations on representation of three-dimensional large-scale circulations and meso-scale eddies in the SCS. The pseudo-observations that are examined include sea surface temperatures (SSTs), sea surface heights (SSHs), sparse temperature/salinity (T/S) profiles, sea surface velocities (SSVs), and sea surface salinities (SSSs). The results show that SSHs can extend their impacts into the subsurface or even the deep ocean while other surface observations only have impacts within surface mixed layer. SSVs have similar impacts though confined to their spatial coverage, suggesting that SSVs could be a substitute of SSHs nearshore where SSHs are of poor quality. Despite their sparseness, the T/S profiles improve the representation of the temperature and salinity structures below the mixed layer, and a combination of T/S profiles with surface observations leads to a better representation of the meso-scale eddies. Based on the OSSE results, an affordable observing network for the SCS in the near future is proposed.
Hase, Kazunori; Yamazaki, Nobutoshi
A model having a three-dimensional entire-body structure and consisting of both the neuronal system and the musculo-skeletal system was proposed to precisely simulate human walking motion. The dynamics of the human body was represented by a 14-rigid-link system and 60 muscular models. The neuronal system was represented by three sub-systems: the rhythm generator system consisting of 32 neural oscillators, the sensory feedback system, and the peripheral system expressed by static optimization. Unknown neuronal parameters were adjusted by a numerical search method using the evaluative criterion for locomotion that was defined by a hybrid between the locomotive energy efficiency and the smoothness of the muscular tensions. The model could successfully generate continuous and three-dimensional walking patterns and stabilized walking against mechanical perturbation. The walking pattern was more stable than that of the model based on dynamic optimization, and more precise than that of the previous model based on a similar neuronal system.
Energy Technology Data Exchange (ETDEWEB)
Hu, Rui
2017-09-03
Mixing, thermal-stratification, and mass transport phenomena in large pools or enclosures play major roles for the safety of reactor systems. Depending on the fidelity requirement and computational resources, various modeling methods, from the 0-D perfect mixing model to 3-D Computational Fluid Dynamics (CFD) models, are available. Each is associated with its own advantages and shortcomings. It is very desirable to develop an advanced and efficient thermal mixing and stratification modeling capability embedded in a modern system analysis code to improve the accuracy of reactor safety analyses and to reduce modeling uncertainties. An advanced system analysis tool, SAM, is being developed at Argonne National Laboratory for advanced non-LWR reactor safety analysis. While SAM is being developed as a system-level modeling and simulation tool, a reduced-order three-dimensional module is under development to model the multi-dimensional flow and thermal mixing and stratification in large enclosures of reactor systems. This paper provides an overview of the three-dimensional finite element flow model in SAM, including the governing equations, stabilization scheme, and solution methods. Additionally, several verification and validation tests are presented, including lid-driven cavity flow, natural convection inside a cavity, laminar flow in a channel of parallel plates. Based on the comparisons with the analytical solutions and experimental results, it is demonstrated that the developed 3-D fluid model can perform very well for a wide range of flow problems.
Ling, C; Connor, K A; Demers, D R; Radke, R J; Schoch, P M
2007-11-01
A magnetic field mapping technique via heavy ion beam trajectory imaging is being developed on the Madison Symmetric Torus reversed field pinch. This paper describes the computational tools created to model camera images of the light emitted from a simulated ion beam, reconstruct a three-dimensional trajectory, and estimate the accuracy of the reconstruction. First, a computer model is used to create images of the torus interior from any candidate camera location. It is used to explore the visual field of the camera and thus to guide camera parameters and placement. Second, it is shown that a three-dimensional ion beam trajectory can be recovered from a pair of perspectively projected trajectory images. The reconstruction considers effects due to finite beam size, nonuniform beam current density, and image background noise. Third, it is demonstrated that the trajectory reconstructed from camera images can help compute magnetic field profiles, and might be used as an additional constraint to an equilibrium reconstruction code, such as MSTFit.
The turbulent destruction of clouds - III. Three dimensional adiabatic shock-cloud simulations
Pittard, J M
2015-01-01
We present 3D hydrodynamic simulations of the adiabatic interaction of a shock with a dense, spherical cloud. We compare how the nature of the interaction changes with the Mach number of the shock, M, and the density contrast of the cloud, chi. We also examine the differences with 2D axisymmetric calculations, perform detailed resolution tests, and compare ``inviscid'' results to those obtained with the inclusion of a k-epsilon subgrid turbulence model. We find that resolutions of 32-64 cells per cloud radius are the minimum necessary to capture the dominant dynamical processes in 3D simulations. In contrast to our earlier 2D work, we find that 3D inviscid and k-epsilon simulations typically show very good agreement. As such, there does not appear to be any compelling reason for using the k-epsilon subgrid model in 3D calculations, though it remains very useful for 2D calculations. Clouds accelerate and mix up to 5 times faster when they are poorly resolved. This has implications for numerical simulations of ...
Santosh, R.; Das, S. K.; Das, G.; Korody, J.; Kumar, S.; Singh, P. K.; Ghosh, M.
2016-07-01
Dissimilar material weld joints, consisting of low-alloy steel and 304LN austenitic stainless steel (SS), have critical application in boiling water reactors in the nuclear industry. It was predicted that phase transformation adjacent to the fusion boundary and stress distribution across the transition joint play a key role in the structural degeneration of these welds. Quantitatively, to evaluate their contribution, two different joints were considered. One was fabricated with buttering material 309L SS (M/S Mishra Dhatu Nigam Limited, Hyderabad, India), and the other was produced with buttering material IN182 (M/S Mishra Dhatu Nigam Limited, Hyderabad, India). Base materials remained the same for both. Thermomechanical simulation on dissimilar material welds was performed using finite-element modeling to predict the thermal effect and stress prone area. Temperature-dependent thermal and structural properties were considered for simulation. Simulation results were compared with microstructural characteristics, and data were obtained from the in-situ tensile test. Simulation results exhibited that stress was at maximum in the buttering material and made the zone weaker with respect to adjacent areas. During the validation of results, it was observed that failure occurred through buttering material and endorsed the inference. The variation in mechanical properties of the two welds was explained considering the effect of thermal state and stress distribution.
Three-Dimensional DSMC Simulations of the Rayleigh-Taylor Instability in Gases
Koehler, T. P.; Gallis, M. A.; Torczynski, J. R.; Plimpton, S. J.
2016-11-01
The Direct Simulation Monte Carlo (DSMC) method of molecular gas dynamics is applied to simulate the Rayleigh-Taylor instability (RTI) in atmospheric-pressure monatomic gases (e.g., argon and helium). The computational domain is a 1-mm by 1-mm by 4-mm cuboid uniformly divided into 62.5 billion cubical cells. A total of 1 trillion computational molecules are used, and time steps of 0.1 ns are used. Simulations are performed to quantify the growth of perturbations on an initially flat interface as a function of the Atwood number. The DSMC results reproduce many features of the RTI and are in reasonable agreement with theoretical and empirical models. Consistent with previous work, the DSMC simulations indicate that the growth of the RTI follows a universal behavior. The numbers of bubble-spike pairs that eventually appear agree with theoretical values based on the most unstable wavelength and are independent of the statistical representation of the gas. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
Shibata, M; Shibata, Masaru; Sekiguchi, Yu-ichirou
2005-01-01
We perform fully general relativistic simulations of rotating stellar core collapse in three spatial dimension. A parametric equation of state is adopted following Dimmelmeier et al. The early stage of the collapse is followed by an axisymmetric code. When the stellar core becomes compact enough, we start a 3-dimensional simulation adding a bar-mode nonaxisymmetric density perturbation. In the axisymmetric simulations, it is clarified that the maximum value of $\\beta \\equiv T/W$ achieved during the stellar collapse and depends sensitively on the velocity profile and total mass of the initial core, and equations of state. It is also found that for all the models with high degree of differential rotation, a funnel structure is formed around the rotational axis after the formation of neutron stars. For selected models in which the maximum value of $\\beta$ is larger than $\\sim 0.27$, 3-dimensional simulations are performed. It is found that the bar-mode dynamical instability sets in for the case that the followin...
THREE-DIMENSIONAL CORE-COLLAPSE SUPERNOVA SIMULATED USING A 15 M{sub ⊙} PROGENITOR
Energy Technology Data Exchange (ETDEWEB)
Lentz, Eric J.; Mezzacappa, Anthony; Harris, J. Austin; Yakunin, Konstantin N. [Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996-1200 (United States); Bruenn, Stephen W. [Department of Physics, Florida Atlantic University, 777 Glades Road, Boca Raton, FL 33431-0991 (United States); Hix, W. Raphael [Physics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6354 (United States); Messer, O. E. Bronson [National Center for Computational Sciences, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6164 (United States); Endeve, Eirik [Computer Science and Mathematics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6164 (United States); Blondin, John M. [Department of Physics, North Carolina State University, Raleigh, NC 27695-8202 (United States); Marronetti, Pedro, E-mail: elentz@utk.edu [Physics Division, National Science Foundation, Arlington, VA 22207 (United States)
2015-07-10
We have performed ab initio neutrino radiation hydrodynamics simulations in three and two spatial dimensions (3D and 2D) of core-collapse supernovae from the same 15 M{sub ☉} progenitor through 440 ms after core bounce. Both 3D and 2D models achieve explosions; however, the onset of explosion (shock revival) is delayed by ∼100 ms in 3D relative to the 2D counterpart and the growth of the diagnostic explosion energy is slower. This is consistent with previously reported 3D simulations utilizing iron-core progenitors with dense mantles. In the ∼100 ms before the onset of explosion, diagnostics of neutrino heating and turbulent kinetic energy favor earlier explosion in 2D. During the delay, the angular scale of convective plumes reaching the shock surface grows and explosion in 3D is ultimately lead by a single, large-angle plume, giving the expanding shock a directional orientation not dissimilar from those imposed by axial symmetry in 2D simulations. We posit that shock revival and explosion in the 3D simulation may be delayed until sufficiently large plumes form, whereas such plumes form more rapidly in 2D, permitting earlier explosions.
Daoud, Mohammad I; Lacefield, James C
2009-09-07
Computational modeling is an important tool in ultrasound imaging research, but realistic three-dimensional (3D) simulations can exceed the capabilities of serial computers. This paper uses a 3D simulator based on a k-space method that incorporates relaxation absorption and nonreflecting boundary conditions. The simulator, which runs on computer clusters, computes the propagation of a single wavefront. In this paper, an allocation algorithm is introduced to assign each scan line to a group of nodes and use multiple groups to compute independent lines concurrently. The computational complexity required for realistic simulations is analyzed using example calculations of ultrasonic propagation and attenuation in the 30-50 MHz band. Parallel efficiency for B-mode imaging simulations is evaluated for various numbers of scan lines and cluster nodes. An aperture-projection technique is introduced to simulate imaging with a focused transducer using reduced computation grids. This technique is employed to synthesize B-mode images that show realistic 3D refraction artifacts. Parallel computing using 20 nodes to compute groups of ten scan lines concurrently reduced the execution time for each image to 18.6 h, compared to a serial execution time of 357.5 h. The results demonstrate that fully 3D imaging simulations are practical using contemporary computing technology.
Bulyha, Alena
2011-01-01
In this work, a Monte-Carlo algorithm in the constant-voltage ensemble for the calculation of 3d charge concentrations at charged surfaces functionalized with biomolecules is presented. The motivation for this work is the theoretical understanding of biofunctionalized surfaces in nanowire field-effect biosensors (BioFETs). This work provides the simulation capability for the boundary layer that is crucial in the detection mechanism of these sensors; slight changes in the charge concentration in the boundary layer upon binding of analyte molecules modulate the conductance of nanowire transducers. The simulation of biofunctionalized surfaces poses special requirements on the Monte-Carlo simulations and these are addressed by the algorithm. The constant-voltage ensemble enables us to include the right boundary conditions; the dna strands can be rotated with respect to the surface; and several molecules can be placed in a single simulation box to achieve good statistics in the case of low ionic concentrations relevant in experiments. Simulation results are presented for the leading example of surfaces functionalized with pna and with single- and double-stranded dna in a sodium-chloride electrolyte. These quantitative results make it possible to quantify the screening of the biomolecule charge due to the counter-ions around the biomolecules and the electrical double layer. The resulting concentration profiles show a three-layer structure and non-trivial interactions between the electric double layer and the counter-ions. The numerical results are also important as a reference for the development of simpler screening models. © 2011 The Royal Society of Chemistry.
Three Dimensional MHD Simulation of Circumbinary Accretion Disks -2. Net Accretion Rate
Shi, Ji-Ming
2015-01-01
When an accretion disk surrounds a binary rotating in the same sense, the binary exerts strong torques on the gas. Analytic work in the 1D approximation indicated that these torques sharply diminish or even eliminate accretion from the disk onto the binary. However, recent 2D and 3D simulational work has shown at most modest diminution. We present new MHD simulations demonstrating that for binaries with mass ratios of 1 and 0.1 there is essentially no difference between the accretion rate at large radius in the disk and the accretion rate onto the binary. To resolve the discrepancy with earlier analytic estimates, we identify the small subset of gas trajectories traveling from the inner edge of the disk to the binary and show how the full accretion rate is concentrated onto them.
Kuznetsova, M.M.; Sibeck, D.; Hesse, M.; Rastatter, L.; Toth, G.
2008-01-01
We performed high resolution global MHD simulations of THEMIS dayside crossings events in May -June 2007. We found that magnetopause surface is not in steady-state even during extended periods of steady solar wind conditions. The so-called tilted reconnection lines become unstable due to formation of pressure bubbles, strong core field flux tubes, vortices, and traveling magnetic field cavities. The topology of FTEs differ from that in two dimension cartoons representing obliquely oriented quasi-2D flux rope. The structure of FTE is changing at spatial scales of 1 -2 Re. Closely located space probes can observe completely different signatures. Branches of bent flux rope can move in opposite directions. THEMIS and Cluster observations are consistent with signatures predicted by simulations.
Two- and three-dimensional simulations of core-collapse supernovae with CHIMERA
Energy Technology Data Exchange (ETDEWEB)
Lentz, Eric J [ORNL; Bruenn, S. W. [Florida Atlantic University, Boca Raton; Harris, James A [ORNL; Chertkow, Merek A [ORNL; Hix, William Raphael [ORNL; Mezzacappa, Anthony [ORNL; Messer, Bronson [ORNL; Blondin, J. M. [North Carolina State University; Marronetti, Pedro [Florida Atlantic University, Boca Raton; Mauney, Christopher M [ORNL; Yakunin, Konstantin [Florida Atlantic University, Boca Raton
2012-01-01
Ascertaining the core-collapse supernova mechanism is a complex, and yet unsolved, problem dependent on the interaction of general relativity, hydrodynamics, neutrino transport, neutrino-matter interactions, and nuclear equations of state and reaction kinetics. Ab initio modeling of core-collapse supernovae and their nucleosynthetic outcomes requires care in the coupling and approximations of the physical components. We have built our multi-physics CHIMERA code for supernova modeling in 1-, 2-, and 3-D, using ray-by-ray neutrino transport, approximate general relativity, and detailed neutrino and nuclear physics. We discuss some early results from our current series of exploding 2D simulations and our work to perform computationally tractable simulations in 3D using the ``Yin--Yang'' grid.
Three-Dimensional Smoothed Particle Hydrodynamics Simulation for Liquid Droplet with Surface Tension
Terissa, Hanifa; Naa, Christian Fredy
2013-01-01
We provide a basic method of Smoothed Particle Hydrodynamics (SPH) to simulate liquid droplet with surface tension in three dimensions. Liquid droplet is a simple case for surface tension modeling. Surface tension works only on fluid surface. In SPH method, we simply apply the surface tension on the boundary particles of liquid. The particle on the 3D boundary was detected dynamically using Free-Surface Detection algorithm. The normal vector and curvature of the boundary surface were calculated simultaneously with 3D boundary surface reconstruction using Moving Least-Squares (MLS) method. Before the reconstruction, the coordinate system was transformed into a local coordinate system. Afterwards, the surface tension force which depends on curvature of the surface, was calculated and applied on the boundary particles of the droplet. We present the simulation result of droplet motion with gravity force. By using the basic method of SPH for fluid modeling, and a combination of 3D Free-Surface Detection algorithm ...
Directory of Open Access Journals (Sweden)
Bing He
2015-01-01
Full Text Available Using parallel computation can enhance the performance of numerical simulation of electromagnetic radiation and get great runtime reduction. We simulate the electromagnetic radiation calculation based on the multicore CPU and GPU Parallel Architecture Clusters by using MPI-OpenMP and MPI-CUDA hybrid parallel algorithm. This is an effective solution comparing to the traditional finite-difference time-domain method which has a shortage in the calculation of the electromagnetic radiation on the problem of inadequate large data space and time. What is more, we use regional segmentation, subregional data communications, consolidation, and other methods to improve procedures nested parallelism and finally verify the correctness of the calculation results. Studying these two hybrid models of parallel algorithms run on the high-performance cluster computer, we draw the conclusion that both models are suitable for large-scale numerical calculations, and MPI-CUDA hybrid model can achieve higher speedup.
Large-scale Monte Carlo simulations of the isotropic three-dimensional Heisenberg spin glass
Lee, L W; Young, A. P.
2007-01-01
We study the Heisenberg spin glass by large-scale Monte Carlo simulations for sizes up to 32^3, down to temperatures below the transition temperature claimed in earlier work. The data for the larger sizes show more marginal behavior than that for the smaller sizes, indicating the lower critical dimension is close to, and possibly equal to three. We find that the spins and chiralities behave in a quite similar manner.
Energy Technology Data Exchange (ETDEWEB)
Chet Nieter
2010-12-01
Superconducting radio frequency (SRF) cavities are a popular choice among researchers designing new accelerators because of the reduced power losses due to surface resistance. However, SRF cavities still have unresolved problems, including the loss of power to stray electrons. Sources of these electrons are field emission from the walls and ionization of background gas, but the predominant source is secondary emission yield (SEY) from electron impact. When the electron motion is in resonance with the cavity fields the electrons strike the cavity surface repeatedly creating a resonant build up of electrons referred to as multipacting. Cavity shaping has successfully reduced multipacting for cavities used in very high energy accelerators. However, multipacting is still a concern for the cavity power couplers, where shaping is not possible, and for cavities used to accelerate particles at moderate velocities. This Phase II project built upon existing models in the VORPAL simulation framework to allow for simulations of multipacting behavior in SRF cavities and their associated structures. The technical work involved allowed existing models of secondary electron generation to work with the complex boundary conditions needed to model the cavity structures. The types of data produced by VORPAL were also expanded to include data common used by cavity designers to evaluate cavity performance. Post-processing tools were also modified to provide information directly related to the conditions that produce multipacting. These new methods were demonstrated by running simulations of a cavity design being developed by researchers at Jefferson National Laboratory to attempt to identify the multipacting that would be an issue for the cavity design being considered. These simulations demonstrate that VORPAL now has the capabilities to assist researchers working with SRF cavities to understand and identify possible multipacting issues with their cavity designs.
Three-Dimensional Smoothed Particle Hydrodynamics Simulation for Liquid Droplet with Surface Tension
Terissa, Hanifa; Barecasco, Agra; Naa, Christian Fredy
2013-01-01
We provide a basic method of Smoothed Particle Hydrodynamics (SPH) to simulate liquid droplet with surface tension in three dimensions. Liquid droplet is a simple case for surface tension modeling. Surface tension works only on fluid surface. In SPH method, we simply apply the surface tension on the boundary particles of liquid. The particle on the 3D boundary was detected dynamically using Free-Surface Detection algorithm. The normal vector and curvature of the boundary surface were calculat...
High Intensity Pressure Noise Transmission in Human Ear: A Three Dimensional Simulation Study
Hawa, Takumi; Gan, Rong; Leckness, Kegan
2015-03-01
High intensity pressure noise generated by explosions and jet engines causes auditory damage and hearing loss of the military service personals, which are the most common disabilities in the veterans. Authors have investigated the high intensity pressure noise transmission from the ear canal to middle ear cavity. A fluid-structure interaction with a viscoelastic model for the tympanic membrane (TM) as well as the ossicular chain has been considered in the study. For the high intensity pressure simulation the geometry of the ear was based on a 3D finite element (FE) model of the human ear reported by Gan et al. (Ann Biomed Eng 2004). The model consists of the ear canal, TM, ossicular chain, and the middle ear cavity. The numerical approach includes two steps: 1) FE based finite-volume method simulation to compute pressure distributions in the ear canal and the middle ear cavity using CFX; and 2) FE modeling of TM and middle ear ossicles in response to high intensity sound using multi-physics analysis in ANSYS. The simulations provide the displacement of the TM/ossicular chain and the pressure fields in the ear canal and the middle ear cavity. These results are compared with human temporal bone experimental data obtained in our group. This work was supported by DOD W81XWH-14-1-0228.
Three-dimensional core-collapse supernova simulated using a 15 $M_\\odot$ progenitor
Lentz, Eric J; Hix, W Raphael; Mezzacappa, Anthony; Messer, O E Bronson; Endeve, Eirik; Blondin, John M; Harris, J Austin; Marronetti, Pedro; Yakunin, Konstantin N
2015-01-01
We have performed \\emph{ab initio} neutrino radiation hydrodynamics simulations in three and two spatial dimensions (3D and 2D) of core-collapse supernovae from the same 15 $M_\\odot$ progenitor through 440 ms after core bounce. Both 3D and 2D models achieve explosions, however, the onset of explosion (shock revival) is delayed by $\\sim$100 ms in 3D relative to the 2D counterpart and the growth of the diagnostic explosion energy is slower. This is consistent with previously reported 3D simulations utilizing iron-core progenitors with dense mantles. In the $\\sim$100 ms before the onset of explosion, diagnostics of neutrino heating and turbulent kinetic energy favor earlier explosion in 2D. During the delay, the angular scale of convective plumes reaching the shock surface grows and explosion in 3D is ultimately lead by a single, large-angle plume, giving the expanding shock a directional orientation not dissimilar from those imposed by axial symmetry in 2D simulations. We posit that shock revival and explosion ...
Three Dimensional Simulation Method in Early Process of Division and Growth for Tumour Cells
Institute of Scientific and Technical Information of China (English)
XIA Zhi-qiu; ZHAO Ting-ting
2014-01-01
The process of division, growth and death for tumour cell mass in the early is simulated. An integrated GUI is provided for users to set the value of each parameters, which are cell growth rates, cell mass division rates, cell mass death rates, simulate type, maximum running time, polarity and cell colour. It can display the growth process of each cell on result GUI. Also, it can display the values of each parameters for observing and analysing in current life cycle on result GUI, which are cell mass division times, cell mass death rate, cell mass division rate and cell mass growth rate. In the process of simulation, The cell growth rate is described by the approach to combine the exponential model with the linear model. In addition, a linked list data structure to store the tumour cells is used by the cellular automata for a reference to determine the position of each cell. It sets up two linked list to store the cells, one of them save the new small division cells and the other one save the big cell. That can make the painting process of cells on result GUI clearer and more organized. At last, the polarity of tumour growth is described for determining the growth direction of cells.
McKinney, Jonathan C; Sadowski, Aleksander; Narayan, Ramesh
2013-01-01
Black hole (BH) accretion flows and jets are dynamic hot relativistic magnetized plasma flows whose radiative opacity can significantly affect flow structure and behavior. We describe a numerical scheme, tests, and an astrophysically relevant application using the M1 radiation closure within a new three-dimensional (3D) general relativistic (GR) radiation (R) magnetohydrodynamics (MHD) massively parallel code called HARMRAD. Our 3D GRRMHD simulation of super-Eddington accretion (about $20$ times Eddington) onto a rapidly rotating BH (dimensionless spin $j=0.9375$) shows sustained non-axisymmemtric disk turbulence, a persistent electromagnetic jet driven by the Blandford-Znajek effect, and a total radiative output consistently near the Eddington rate. The total accretion efficiency is of order $20\\%$, the large-scale electromagnetic jet efficiency is of order $10\\%$, and the total radiative efficiency that reaches large distances remains low at only order $1\\%$. However, the radiation jet and the electromagnet...
Directory of Open Access Journals (Sweden)
D. V. Rose
2010-09-01
Full Text Available A 3D fully electromagnetic (EM model of the principal pulsed-power components of a high-current linear transformer driver (LTD has been developed. LTD systems are a relatively new modular and compact pulsed-power technology based on high-energy density capacitors and low-inductance switches located within a linear-induction cavity. We model 1-MA, 100-kV, 100-ns rise-time LTD cavities [A. A. Kim et al., Phys. Rev. ST Accel. Beams 12, 050402 (2009PRABFM1098-440210.1103/PhysRevSTAB.12.050402] which can be used to drive z-pinch and material dynamics experiments. The model simulates the generation and propagation of electromagnetic power from individual capacitors and triggered gas switches to a radially symmetric output line. Multiple cavities, combined to provide voltage addition, drive a water-filled coaxial transmission line. A 3D fully EM model of a single 1-MA 100-kV LTD cavity driving a simple resistive load is presented and compared to electrical measurements. A new model of the current loss through the ferromagnetic cores is developed for use both in circuit representations of an LTD cavity and in the 3D EM simulations. Good agreement between the measured core current, a simple circuit model, and the 3D simulation model is obtained. A 3D EM model of an idealized ten-cavity LTD accelerator is also developed. The model results demonstrate efficient voltage addition when driving a matched impedance load, in good agreement with an idealized circuit model.
LARGE-EDDY SIMULATION OF THREE-DIMENSIONAL TURBULENT FLOW AROUND A CIRCULAR PIER
Institute of Scientific and Technical Information of China (English)
ZHAO Wei; Huhe Aode
2006-01-01
In this article, the turbulent flow field and the scouring mechanism around a circular pier were numerically investigated using the Large Eddy Simulation (LES) method for three scouring holes. The effects of the bottom topographies on the flow structure were studied in detail. The results show that at the downstream of the pier, as the scouring depth increases, the bed shear stress decreases and approaches to the undisturbed shear stress, however, the turbulent intensity, the fluctuating pressure, and the vertical pressure gradient increase gradually.
Three-dimensional Numerical Simulation of Combustion Field in the Combustion Chamber
Institute of Scientific and Technical Information of China (English)
YAN Ping; QIAN Zhi-bo; YANG Jie; ZHANG Jin-jun
2006-01-01
In order to study the effect of rotation on the combustion in the underwater vehicle, a two-phase turbulent combustion process is described with Reynolds stress turbulence model, eddy-dissipation turbulent combustion model, P-1 radiation model and particle tracking model of liquid. The flow in the rotating combustion chamber is simulated at two different working speeds, 0 r/min and 1 000 r/min by Fluent software. The temperature, gas velocity, static pressure of wall and fuel concentration are computed and compared. The results show that the combustion in rotating combustor is faster and more effective.
A THREE-DIMENSIONAL MODEL OF ACTIVE REGION 7986: COMPARISON OF SIMULATIONS WITH OBSERVATIONS
Energy Technology Data Exchange (ETDEWEB)
Mok, Yung [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Mikić, Zoran; Lionello, Roberto; Downs, Cooper; Linker, Jon A., E-mail: ymok@uci.edu [Predictive Science, Inc., San Diego, CA 92121 (United States)
2016-01-20
In the present study, we use a forward modeling method to construct a 3D thermal structure encompassing active region 7986 of 1996 August. The extreme ultraviolet (EUV) emissions are then computed and compared with observations. The heating mechanism is inspired by a theory on Alfvén wave turbulence dissipation. The magnetic structure is built from a Solar and Heliospheric Observatory (SOHO)/MDI magnetogram and an estimated torsion parameter deduced from observations. We found that the solution to the equations in some locations is in a thermal nonequilibrium state. The time variation of the density and temperature profiles leads to time dependent emissions, which appear as thin, loop-like structures with uniform cross-section. Their timescale is consistent with the lifetime of observed coronal loops. The dynamic nature of the solution also leads to plasma flows that resemble observed coronal rain. The computed EUV emissions from the coronal part of the fan loops and the high loops compare favorably with SOHO/EIT observations in a quantitative comparison. However, the computed emission from the lower atmosphere is excessive compared to observations, a symptom common to many models. Some factors for this discrepancy are suggested, including the use of coronal abundances to compute the emissions and the neglect of atmospheric opacity effects.
Seitenzahl, Ivo R; Ohlmann, Sebastian T; Ciaraldi-Schoolmann, Franco; Marquardt, Kai; Fink, Michael; Hillebrandt, Wolfgang; Pakmor, Ruediger; Roepke, Friedrich K; Ruiter, Ashley J; Sim, Stuart A; Taubenberger, Stefan
2016-01-01
The gravitationally confined detonation (GCD) model has been proposed as a possible explosion mechanism for Type Ia supernovae in the single-degenerate evolution channel. Driven by buoyancy, a deflagration flame rises in a narrow cone towards the surface. For the most part, the flow of the expanding ashes remains radial, but upon reaching the outer, low-pressure layers of the white dwarf, an additional lateral component develops. This makes the deflagration ashes converge again at the opposite side, where the compression heats fuel and a detonation may be launched. To test the GCD explosion model, we perform a 3D simulation for a model with an ignition spot offset near the upper limit of what is still justifiable, 200 km. This simulation meets our deliberately optimistic detonation criteria and we initiate a detonation. The detonation burns through the white dwarf and leads to its complete disruption. We determine nucleosynthetic yields by post-processing 10^6 tracer particles with a 384 nuclide reaction netw...
López-Cámara, D.; Lazzati, Davide; Morsony, Brian J.
2016-08-01
Gamma-ray burst (GRB) light curves are characterized by marked variability, each showing unique properties. The origin of this variability, at least for a fraction of long GRBs, may be the result of an unsteady central engine. It is thus important to study the effects that an episodic central engine has on the jet propagation and, eventually, on the prompt emission within the collapsar scenario. Thus, in this study we follow the interaction of pulsed outflows with their progenitor stars with hydrodynamic numerical simulations in both two and three dimensions. We show that the propagation of unsteady jets is affected by the interaction with the progenitor material well after the break-out time, especially for jets with long quiescent times comparable to or larger than a second. We also show that this interaction can lead to an asymmetric behavior in which pulse durations and quiescent periods are systematically different. After the pulsed jets drill through the progenitor and the interstellar medium, we find that, on average, the quiescent epochs last longer than the pulses (even in simulations with symmetrical active and quiescent engine times). This could explain the asymmetry detected in the light curves of long quiescent time GRBs.
Three-dimensional simulation of liquid injection, film formation and transport, in fluidized beds
Institute of Scientific and Technical Information of China (English)
Paul (Pinghua) Zhao; Peter J. O'Rourke; Dale Snider
2009-01-01
Liquid injection, and film formation and transport in dense-phase gas-solids fluidized beds are numerically simulated in three dimensions using a collisional exchange model that is based on the mechanism that collisions cause transfer of liquid mass, momentum, and energy between particles. In the model, each of the particles is represented by a solid core and a liquid film surrounding the core. The model is incorporated in the framework of the commercial code Barracuda developed by CPFD Software. The commercial software is an advanced CFD-based computational tool where the particles are treated as discrete entities, calculated by the MP-PIC method, and tracked using the Lagrangian method.Details of the collisional liquid transfer model have been previously presented in O'Rourke, Zhao, and Snider (2009); this paper presents new capabilities and proof-testing of the collision model and a new method to better quantify the penetration length. Example calculations of a fluidized bed without liquid injection show the expected effect of collisions on the reduction of granular temperature (fluctuational kinetic energy) of the bed. When applied to liquid injection into a dense-phase fluidized bed under different conditions, the model predicts liquid penetration lengths comparable to the experiments. In addition, the simulation reveals for the first time the dynamic mixing of the liquid droplets with the bed particles and the transient distribution of the droplets inside the bed.
Simulating the three-dimensional deformation of in vivo facial skin.
Flynn, Cormac; Taberner, Andrew J; Nielsen, Poul M F; Fels, Sidney
2013-12-01
Characterising the mechanical properties of human facial skin is a challenging but important endeavour with applications in biomedicine, surgery simulation, forensics, and animation. Many existing computer models of the face are not based on in vivo facial skin deformation data but rather on experiments using in vitro facial skin or other soft tissues. The facial skin of five volunteers was subjected to a rich set of deformations using a micro-robotic device. The force-displacement response was recorded for each deformation. All volunteers' facial skin exhibited a non-linear, anisotropic, and viscoelastic force-displacement response. We propose a finite element model that simulated the experimental deformations with error-of-fits ranging from 11% to 23%. The skin was represented by an Ogden strain energy function and a quasi-linear viscoelastic law. From non-linear optimisation procedures, we determined material parameters and in vivo pre-stresses for the central cheek area of five volunteers and five other facial points on one volunteer. Pre-stresses ranged from 15.9kPa to 89.4kPa.
Validation of Three-Dimensional Simulation of Flow through Hypersonic Air-breathing Engine
Directory of Open Access Journals (Sweden)
Thangadurai Murugan
2015-07-01
Full Text Available The flow path of a conceptual hypersonic air-breathing scramjet engine integrated with the vehicle (without combustion has been simulated numerically using ANSYS CFX software with the SST turbulence model. The computations were performed for the free stream Mach number of 6 and angle-of-attack of 5°. A strong separation bubble was observed on the bodyside wall in the internal compression region where the reflected cowl shock impinges on body which in turn increases the static pressure substantially. The external-internal flow field of the hypersonic mixed compression intake, shock-boundary layer interactions, and the shock-shock interactions present in the internal compression region have qualitatively been obtained and analysed. The variation of centreline pressure along the bodyside wall close to the symmetry plane obtained from numerical simulation centreline has been compared with the experimentally measured data. It has been observed that the computed wall pressure matches fairly well with the measured values in the external ramp compression region, internal compression region and in the combustion chamber. The flow patterns and the pressure variations near the middle wall and the fuel injecting strut locations have also been analysed.Defence Science Journal, Vol. 65, No. 4, July 2015, pp. 272-278, DOI: http://dx.doi.org/10.14429/dsj.65.6979
Barth, N.; George, D.; Ahzi, S.; Rémond, Y.; Joulaee, N.; Khaleel, M. A.; Bouyer, F.
2014-02-01
The modeling of the viscoelastic stress evolution and specific volume relaxation of a bulky glass cast is presented in this article and is applied to the experimental cooling process of an inactive nuclear waste vitrification process. The concerned borosilicate glass is solidified and cooled down to ambient temperature in a stainless steel canister, and the thermomechanical response of the package is simulated. There exists a deviant compression of the liquid core due to the large glass package compared to standard tempered glass plates. The stress load development of the glass cast is finally studied for different thermal load scenarios, where the cooling process parameters or the final cooldown rates were changed, and we found a great influence of the studied cooldown rates on the maximum stress build-up at ambient temperature.
Ryu, Jaeyoung; Cho, Jinyong; Kim, Hyeon Min
2016-07-01
The dental occlusion is the important reference for replacement of the temporomandibular joint. If a patient does not have normal occlusion, few considerations are needed for temporomandibular joint replacement. The custom-made prosthesis, typically fabricated with a stereolithographic model, is probably the optimized solution currently available. However the ready-made stock from Biomet Microfixation System (Jacksonville, FL) is the only available product, which is authorized by the government ministry in South Korea, for replacement of the temporomandibular joint. This report presents a patient with the problems that were retrognathic "bird face" profile subsequent to severe bilateral condylar resorption and temporomandibular joint ankylosis without enough natural teeth for occlusion. Bilateral temporomandibular joint replacement using the ready-made prosthesis was done by reestablishing the mandibular position with new occlusion and improved facial profile via the virtual surgical planning and stereolithographic model simulation.
Three-Dimensional Simulations of Tearing and Intermittency in Coronal Jets
Wyper, P F; Karpen, J T; Lynch, B J
2016-01-01
Observations of coronal jets increasingly suggest that local fragmentation and intermittency play an important role in the dynamics of these events. In this work we investigate this fragmentation in high-resolution simulations of jets in the closed-field corona. We study two realizations of the embedded-bipole model, whereby impulsive helical outflows are driven by reconnection between twisted and untwisted field across the domed fan plane of a magnetic null. We find that the reconnection region fragments following the onset of a tearing-like instability, producing multiple magnetic null points and flux-rope structures within the current layer. The flux ropes formed within the weak-field region in the center of the current layer are associated with "blobs" of density enhancement that become filamentary threads as the flux ropes are ejected from the layer, whereupon new flux ropes form behind them. This repeated formation and ejection of flux ropes provides a natural explanation for the intermittent outflows, ...
Three-dimensional numerical simulation on plastic damage in small punch specimen of Zirconium
Energy Technology Data Exchange (ETDEWEB)
Hu Ruomei, E-mail: huruomei2008@sina.co [School of Mechanical and Power Engineering, Nanjing University of Technology, Nanjing 210009 (China); Ling Xiang, E-mail: xling@njut.edu.c [School of Mechanical and Power Engineering, Nanjing University of Technology, Nanjing 210009 (China)
2009-12-15
Small punch test (SPT) technique was used to evaluate the mechanical properties of Zirconium in this paper. The dimension of the disc specimen is phi 10 x 0.5 mm. Plastic damage in small punch specimen of Zirconium was investigated both experimentally and numerically, because it has great influence on small punch specimen. In order to simulate the plastic damage in the small punch specimen of Zirconium, the 3D finite element model incorporated with Gurson-Tvergaard-Needleman (GTN) plastic damage constitutive equation was established. Void growth and initiation of ductile crack of the small punch specimen were predicted. Results show that damage occurs on the bottom side of the specimen and grows across the specimen until complete failure, which has good agreement with the observation in the experiment.
Numerical Simulation of the Scalar Mixing Characteristics in Three-dimensional Microchannels
Institute of Scientific and Technical Information of China (English)
刘演华; 林建忠; 包福兵; 石兴
2005-01-01
Based on the transport phenomena theory, the passive mixing of water and ethanol in different threedimensional microchannels is simulated numerically. The average variance of water volume fraction is used to index the mixing efficiency in the cases with different Reynolds number and different fabricated mixers. The results show that the efficiency of liquid mixing is progressively dependent on the convective transport as the Reynolds number increases. The efficiency of serpentine microchannel decreases with the increasing Reynolds number in the laminar regime. Altering the aspect ratio of channel inlet section has no significant effect on the mixing efficiency. Increasing the area of channel inlet section will cause the decrease of the mixing efficiency. The mixing in serpentine channels is the most efficient among three different mixers because of the existence of second flow introduced by its special structure.
Three-Dimensional Simulations of SASI- and Convection-Dominated Core-Collapse Supernovae
Fernández, Rodrigo
2015-01-01
We investigate the effect of dimensionality on the transition to explosion in neutrino-driven core-collapse supernovae. Using parameterized hydrodynamic simulations of the stalled supernova shock in one-, two- (2D), and three spatial dimensions (3D), we systematically probe the extent to which hydrodynamic instabilities alone can tip the balance in favor of explosion. In particular, we focus on systems that are well into the regimes where the Standing Accretion Shock Instability (SASI) or neutrino-driven convection dominate the dynamics, and characterize the difference between them. We find that SASI-dominated models can explode with up to ~20% lower neutrino luminosity in 3D than in 2D, with the magnitude of this difference decreasing with increasing resolution. This improvement in explosion conditions originates in the ability of spiral modes to generate more non-radial kinetic energy than a single sloshing mode, increasing the size of the average shock radius, and hence generating better conditions for the...
Numerical simulation of flow characteristic in three-dimensional bend pipes
Wang, T.; Tu, S.; Dong, D.
2010-03-01
Variety of pipes with different types of layout is widely used in enterprise. Flow resistance and turbulence is increased by irrational layout of the pipes and flow conditions, and even the pipe system vibration will occur induced probably by fluid disturbance. In this paper, three typical bend pipes in three-dimension are analyzed from pressure loss and streamline by numerical simulation. The straight and bend section of the pipe is generated and meshed by the hexahedral elements. The quality of meshes is good, and the grid cells are about 300,000. Calculation shows that the first type with the inlet and outlet in opposite direction in one plane has the least resistance coefficient. Therefore, adopting plain layout may be the best choice of the three types mentioned in the paper.
Three-dimensional simulations of turbulent convective mixing in ONe and CO classical nova explosions
Casanova, Jordi; Garcia-Berro, Enrique; Shore, Steven N
2016-01-01
Classical novae are thermonuclear explosions that take place in the envelopes of accreting white dwarfs in binary systems. The material piles up under degenerate conditions, driving a thermonuclear runaway. The energy released by the suite of nuclear processes operating at the envelope heats the material up to peak temperatures about 100 - 400 MK. During these events, about 10-3 - 10-7 Msun, enriched in CNO and, sometimes, other intermediate-mass elements (e.g., Ne, Na, Mg, Al) are ejected into the interstellar medium. To account for the gross observational properties of classical novae (in particular, the large concentrations of metals spectroscopically inferred in the ejecta), models require mixing between the (solar-like) material transferred from the secondary and the outermost layers (CO- or ONe-rich) of the underlying white dwarf. Recent multidimensional simulations have demonstrated that Kelvin-Helmholtz instabilities can naturally produce self-enrichment of the accreted envelope with material from the...
Three-dimensional simulation of heat and moisture transfer in wood
Energy Technology Data Exchange (ETDEWEB)
Younsi, R.; Kocaefe, D.; Kocaefe, Y. [Department of Applied Sciences, University of Quebec at Chicoutimi, 555, boul. de l' Universite, Chicoutimi, Quebec (Canada)
2006-08-15
This paper deals with the numerical simulation of 3D heat and moisture transfer in wood. The mathematical model is based on a set of coupled, heat and mass transfer equations proposed by Luikov (1976). Numerous series of calculations were carried out over the range of 0.01
NUMERICAL SIMULATION OF THREE DIMENSIONAL GAS-PARTICLE FLOW IN A SPIRAL CYCLONE
Institute of Scientific and Technical Information of China (English)
WANG Can-xing; YI Lin
2006-01-01
The three-dimension gas-particle flow in a spiral cyclone is simulated numerically in this paper. The gas flow field was obtained by solving the three-dimension Navier-Stokes equations with Reynolds Stress Model (RSM). It is shown that there are two regions in the cyclone, the steadily tangential flow in the spiral channel and the combined vortex flow in the centre. Numerical results for particles trajectories show that the initial position of the particle at the inlet plane substantially affects its trajectory in the cyclone. The particle collection efficiency curves at different inlet velocities were obtained and the effects of inlet flow rate on the performance of the spiral cyclone were presented.Numerical results also show that the increase of flow rate leads to the increase of particles collection efficiency, but the pressure drop increases sharply.
Energy Technology Data Exchange (ETDEWEB)
Labourdette, Richard; Poncet, Jerome; Seguin, Julien; Temple, Francois [Total, Geoscience Technologies, Pau, 64 (France); Hegre, JoAnn; Irving, Alan [Total E and P UK plc, Geoscience Research Centre, Aberdeen (United Kingdom)
2006-07-01
The examination of production history from hydrocarbon fields composed of turbidite deposits indicates that fluid flow behaviour is often more complex than expected. The cause is commonly linked to the presence of fine-scale sedimentary heterogeneities, which complicate the reservoir. This is especially true in the case of turbiditic submarine channel complexes with final channel-filling stages composed of lateral migration deposits. These fine-scale heterogeneities are usually below seismic resolution and are rarely represented in initial reservoir models designed for such fields. Thus, it is difficult to match the production history or identify methods to improve production and reduce associated risks. The various depositional patterns recognized in channel migration and aggradation packages from the Oligocene Malembo Formation of the Congo Basin, offshore Angola, exhibit different dynamic responses when modelled in a reservoir simulator. These dynamic differences are related to the different preservation rates of bank collapse sediments within isolated channel bodies, hereafter referred to as 'elementary channels'. According to these preservation differences, the vertical stacking pattern of channels results in better connectivity than the true lateral migration. This effect has been incorporated into a full-field simulation model by applying petrophysical upscaling methods. The recognition and modelling of detailed sedimentological heterogeneities, and their distribution along full-field models produces a better history match when the inherent uncertainties have been taken into account. Incorporating all available data and concepts to define reservoir architecture is essential in understanding the impact that fine-scale heterogeneities have on reservoir management. As the lateral extent and areal distribution of heterogeneities is still unknown, our modelling workflow incorporates uncertainty in the form of multiple realizations to identify and
Wang, Hsiang-Hsu; Shang, Hsien; Gu, Pin-Gao
2014-01-01
The regular satellites found around Neptune ($\\approx 17~M_{\\Earth}$) and Uranus ($\\approx 14.5~M_{\\Earth}$) suggest that past gaseous circumplanetary disks may have co-existed with solids around sub-Neptune-mass protoplanets ($< 17~M_{\\Earth}$). These disks have been shown to be cool, optically thin, quiescent, with low surface density and low viscosity. Numerical studies of the formation are difficult and technically challenging. As an introductory attempt, three-dimensional global simulations are performed to explore the formation of circumplanetary disks around sub-Neptune-mass protoplanets embedded within an isothermal protoplanetary disk at the inviscid limit of the fluid in the absence of self-gravity. Under such conditions, a sub-Neptune-mass protoplanet can reasonably have a rotationally supported circumplanetary disk. The size of the circumplanetary disk is found to be roughly one-tenth of the corresponding Hill radius, which is consistent with the orbital radii of irregular satellites found for ...
Institute of Scientific and Technical Information of China (English)
陈普庆; 夏伟; 周照耀; 朱权利; 李元元
2004-01-01
The application of a combined finite-discrete element modeling approach to simulate the three-dimensional microscopic compaction behavior of single-layer metal powder system was described. The process was treated as a static problem, with kinematical component being neglected. Due to ill condition, Cholesky's method failed to solve the system equations, while conjugate gradient method was tried and yielded good results. Deformation of the particles was examined and compared with the results of physical modeling experiments. In both cases, the inner particles were deformed from sphere to polygonal column, with the edges turning from arc to straight line. The edge number of a particle was equal to the number of particles surrounding it. And the experiments show that the ductile metal particles can be densified only by their plastic deformation without the occurrence of rearrangement phenomenon.
Shen, Fang; Wang, Yuming; Feng, Xueshang; Xiang, Changqing
2014-01-01
Though coronal mass ejections (CMEs) are magnetized fully-ionized gases, a recent observational study of a CME collision event in 2008 November has suggested that their behavior in the heliosphere is like elastic balls, and their collision is probably super-elastic \\citep{Shen_etal_2012}. If this is true, this finding has an obvious impact on the space weather forecasting because the direction and veliocity of CMEs may change. To verify it, we numerically study the event through three-dimensional MHD simulations. The nature of CMEs' collision is examined by comparing two cases. In one case the two CMEs collide as observed, but in the other, they do not. Results show that the collision leads to extra kinetic energy gain by 3%--4% of the initial kinetic energy of the two CMEs. It firmly proves that the collision of CMEs could be super-elastic.
Zhang, Yanxiang; Ni, Meng; Yan, Mufu; Chen, Fanglin
2015-12-01
Nanostructured electrodes are widely used for low temperature solid oxide fuel cells, due to their remarkably high activity. However, the industrial applications of the infiltrated electrodes are hindered by the durability issues, such as the microstructure stability against thermal aging. Few strategies are available to overcome this challenge due to the limited knowledge about the coarsening kinetics of the infiltrated electrodes and how the potentially important factors affect the stability. In this work, the generic thermal aging kinetics of the three-dimensional microstructures of the infiltrate electrodes is investigated by a kinetic Monte Carlo simulation model considering surface diffusion mechanism. Effects of temperature, infiltration loading, wettability, and electrode configuration are studied and the key geometric parameters are calculated such as the infiltrate particle size, the total and percolated quantities of three-phase boundary length and infiltrate surface area, and the tortuosity factor of infiltrate network. Through parametric study, several strategies to improve the thermal aging stability are proposed.
Kim, Chang-Goo; Kim, Woong-Tae
2013-01-01
The energy and momentum feedback from young stars has a profound impact on the interstellar medium (ISM), including heating and driving turbulence in the neutral gas that fuels future star formation. Recent theory has argued that this leads to a quasi-equilibrium self-regulated state, and for outer atomic-dominated disks results in the surface density of star formation $\\Sigma_{SFR}$ varying approximately linearly with the weight of the ISM (or midplane turbulent + thermal pressure). We use three-dimensional numerical hydrodynamic simulations to test the theoretical predictions for thermal, turbulent, and vertical dynamical equilibrium, and the implied functional dependence of $\\Sigma_{SFR}$ on local disk properties. Our models demonstrate that all equilibria are established rapidly, and that the expected proportionalities between mean thermal and turbulent pressures and $\\Sigma_{SFR}$ apply. For outer disk regions, this results in $\\Sigma_{SFR} \\propto \\Sigma \\sqrt{\\rho_{sd}}$, where $\\Sigma$ is the total ga...
Institute of Scientific and Technical Information of China (English)
罗马吉; 陈国华; 马元镐
2003-01-01
This paper presents a KIVA-3 code based numerical model for three-dimensional transient intake flow in the intake port-valve-cylinder system of internal combustion engine using body-fitted technique, which can be used in numerical study on internal combustion engine with vertical and inclined valves, and has higher calculation precision. A numerical simulation (on the intake process of a two-valve engine with a semi-sphere combustion chamber and a radial intake port) is provided for analysis of the velocity field and pressure field of different plane at different crank angles. The results revealed the formation of the tumble motion, the evolution of flow field parameters and the variation of tumble ratios as important information for the design of engine intake system.
Carmona Torres, José A; Cangas, Adolfo J; García, Gustavo R; Langer, Alvaro I; Zárate, Roberto
2012-01-01
The current study analyzes the psychometric properties of an innovative three-dimensional (3D) simulation program, entitled Mii-School (MS), designed for the early detection of drug use and bullying in Secondary School children. This computer program showed adequate reliability and construct validity. The factorial structure, as well as the explanatory weight of the different factors, is presented. In addition, the results of a parallel version in paper and pencil format are also presented and compared with those of the computerized version (i.e., MS). There was a statistically significant difference between the two formats in the total (i.e., combined) sore of risk. When drug use and bullying were separately analyzed, differences were found only with regard to drug use. The relevance of these results as well as the suitability of this type of 3D instrument for the early detection of risky behaviors in young people are discussed.
Institute of Scientific and Technical Information of China (English)
罗马吉; 陈国华; 马元镐
2003-01-01
This paper presents a KIVA-3 code based numerical model for three-dimensional transient intake flow in the intake port-valve-cylinder system of internal combustion engine using body-fitted technique, which can be used in numerical study on internal combustion engine with vertical and inclined valves, and has higher calculation precision. A numerical simulation (on the intake process of a two-valve engine with a semi-sphere combustion chamber and a radial intake port) is provided for analysis of the velocity field and pressure field of different plane at different crank angles. The results revealed the formation of the tumble motion, the evolution of flow field parameters and the variation of tumble ratios as important information for the design of engine in-take system.
Reisswig, C; Ott, C D; Abdikamalov, E; Moesta, P; Pollney, D; Schnetter, E
2013-01-01
We present a new three-dimensional general-relativistic hydrodynamic evolution scheme coupled to dynamical spacetime evolutions which is capable of efficiently simulating stellar collapse, isolated neutron stars, black hole formation, and binary neutron star coalescence. We make use of a set of adapted curvi-linear grids (multipatches) coupled with flux-conservative cell-centered adaptive mesh refinement. This allows us to significantly enlarge our computational domains while still maintaining high resolution in the gravitational-wave extraction zone, the exterior layers of a star, or the region of mass ejection in merging neutron stars. The fluid is evolved with a high-resolution shock capturing finite volume scheme, while the spacetime geometry is evolved using fourth-order finite differences. We employ a multi-rate Runge-Kutta time integration scheme for efficiency, evolving the fluid with second-order and the spacetime geometry with fourth-order integration, respectively. We validate our code by a number ...
Zhang, Weiqun; Wang, Peng
2008-01-01
Magnetic field strengths inferred for relativistic outflows including gamma-ray bursts (GRB) and active galactic nuclei (AGN) are larger than naively expected by orders of magnitude. We present three-dimensional relativistic magnetohydrodynamics (MHD) simulations demonstrating amplification and saturation of magnetic field by a macroscopic turbulent dynamo triggered by the Kelvin-Helmholtz shear instability. We find rapid growth of electromagnetic energy due to the stretching and folding of field lines in the turbulent velocity field resulting from non-linear development of the instability. Using conditions relevant for GRB internal shocks and late phases of GRB afterglow, we obtain amplification of the electromagnetic energy fraction to $\\epsilon_B \\sim 5 \\times 10^{-3}$. This value decays slowly after the shear is dissipated and appears to be largely independent of the initial field strength. The conditions required for operation of the dynamo are the presence of velocity shear and some seed magnetization b...
Lee, C. H.; Yang, D. Y.; Lee, S. R.; Chang, I. G.; Lee, T. W.
2011-08-01
The shielded slot plate, which has a sheared corrugated trapezoidal pattern, is a component of the metallic bipolar plate for the molten carbonate fuel cell (MCFC). In order to increase the efficiency of the fuel cell, the unit cell of the shielded slot plate should have a relatively large upper area. Additionally, defects from the forming process should be minimized. In order to simulate the slitting process, whereby sheared corrugated patterns are formed, ductile fracture criteria based on the histories of stress and strain are employed. The user material subroutine VUMAT is employed for implementation of the material and ductile fracture criteria in the commercial FEM software ABAQUS. The variables of the ductile fracture criteria were determined by comparing the simulation results and the experimental results of the tension test and the shearing test. Parametric studies were conducted to determine the critical value of the ductile fracture criterion. Employing these ductile fracture criteria, the three dimensional forming process of the shielded slot plate was numerically simulated. The effects of the slitting process in the forming process of the shielded slot plate were analyzed through a FEM simulation and experimental studies. Finally, experiments involving microscopic and macroscopic observations were conducted to verify the numerical simulations of the 3-step forming process.
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
Packing of spherical particles in a three-dimensional cylindrical container is simulated by using Discrete Element Method.The packed bed of spheres is also subjected to vertical compression which results in a dense compact.Microstructures of the packing during compaction are examined in detail in terms of the contact number,deviator fabric,and radial distribution function.Furthermore,contact force distributions are measured at different locations in the pack,i.e.the centre,the side wall,and the base(or bottom wall) of the container.The simulations show that random close packing(RCP) tends to exist in the centre of the pack,while ordered packing structures exist near the container’s walls.The uniaxial compression doesn’t seem to alter the packing structure in the pack centre remarkably,but to reduce the structural anisotropy of the packing close to the container’s base.The simulated results have also helped to establish the correlations between packing structures and contact force distributions.Further,it is shown that small contact force distributions are sensitive to local packing structures.The simulated results are shown to be consistent with the recent experimental and simulation findings.
Freund, H. P.; van der Slot, P. J. M.; Grimminck, D. L. A. G.; Setija, I. D.; Falgari, P.
2017-02-01
Free-electron lasers (FELs) have been built ranging in wavelength from long-wavelength oscillators using partial wave guiding through ultraviolet through hard x-ray that are either seeded or start from noise. In addition, FELs that produce different polarizations of the output radiation ranging from linear through elliptic to circular polarization are currently under study. In this paper, we develop a three-dimensional, time-dependent formulation that is capable of modeling this large variety of FEL configurations including different polarizations. We employ a modal expansion for the optical field, i.e., a Gaussian expansion with variable polarization for free-space propagation. This formulation uses the full Newton–Lorentz force equations to track the particles through the optical and magnetostatic fields. As a result, arbitrary three-dimensional representations for different undulator configurations are implemented, including planar, helical, and elliptical undulators. In particular, we present an analytic model of an APPLE-II undulator to treat arbitrary elliptical polarizations, which is used to treat general elliptical polarizations. To model oscillator configurations, and allow propagation of the optical field outside the undulator and interact with optical elements, we link the FEL simulation with the optical propagation code OPC. We present simulations using the APPLE-II undulator model to produce elliptically polarized output radiation, and present a detailed comparison with recent experiments using a tapered undulator configuration at the Linac Coherent Light Source. Validation of the nonlinear formation is also shown by comparison with experimental results obtained in the Sorgente Pulsata Auto-amplificata di Radiazione Coerente SASE FEL experiment at ENEA Frascati, a seeded tapered amplifier experiment at Brookhaven National Laboratory, and the 10 kW upgrade oscillator experiment at the Thomas Jefferson National Accelerator Facility.
Pelties, Christian
2012-02-18
Accurate and efficient numerical methods to simulate dynamic earthquake rupture and wave propagation in complex media and complex fault geometries are needed to address fundamental questions in earthquake dynamics, to integrate seismic and geodetic data into emerging approaches for dynamic source inversion, and to generate realistic physics-based earthquake scenarios for hazard assessment. Modeling of spontaneous earthquake rupture and seismic wave propagation by a high-order discontinuous Galerkin (DG) method combined with an arbitrarily high-order derivatives (ADER) time integration method was introduced in two dimensions by de la Puente et al. (2009). The ADER-DG method enables high accuracy in space and time and discretization by unstructured meshes. Here we extend this method to three-dimensional dynamic rupture problems. The high geometrical flexibility provided by the usage of tetrahedral elements and the lack of spurious mesh reflections in the ADER-DG method allows the refinement of the mesh close to the fault to model the rupture dynamics adequately while concentrating computational resources only where needed. Moreover, ADER-DG does not generate spurious high-frequency perturbations on the fault and hence does not require artificial Kelvin-Voigt damping. We verify our three-dimensional implementation by comparing results of the SCEC TPV3 test problem with two well-established numerical methods, finite differences, and spectral boundary integral. Furthermore, a convergence study is presented to demonstrate the systematic consistency of the method. To illustrate the capabilities of the high-order accurate ADER-DG scheme on unstructured meshes, we simulate an earthquake scenario, inspired by the 1992 Landers earthquake, that includes curved faults, fault branches, and surface topography. Copyright 2012 by the American Geophysical Union.
Lu, Rong; Turco, Richard P.
The: air quality problems in the Los Angeles basin are related to the local climate. A strong temperature inversion and stagnant synoptic conditions associated with the Pacific high-pressure system favor the generation of severe air pollution episodes. Sea-breezes and mountain-induced flows play an important role: in controlling pollutant transport over the basin. The distributions of pollutants over the basin display complicated three-dimensional patterns, including distinct elevated layers. A three-dimensional meteorological model is used to simulate air flow patterns and pollutant transport in the Los Angeles basin under such conditions. The complex simulated flows are analyzed to explain the origin of the observed pollution layers. Pollutants found in the afternoon mixed layer may be dispersed to three different regions: the high desert to the east and north of the Los Angeles basin; the free troposphere above the temperature inversion; and within the temperature inversion layer itself. Several mechanisms transfer pollution into the inversion layer. Convergence zones in the San Fernando Valley and near Lake Elsinore lift polluted air into the inversion. A coupled sea-bree~eymountain-flow circulation along the southwest flank of the Santa Ana Mts creates pollution layers that extend westward over the coastal plain and offshore. The afternoon pollution layers frequently observed in the western Los Angeles basin are caused by the sea-breeze circulation or the coupled sea-breeze/mountain-flow circulation over the south slope of the San Gabriel Nlts. As the boundary layer stabilizes during the early evening, layers of polluted air are left suspended over the eastern basin. Pollutants trapped in the inversion layer act as a reservoir of poor-quality air for the basin, and may contribute to extreme pollutant concentrations seen after several days of stagnant air.
Le Guennec, Yves; Savin, Éric
2011-12-01
The theory of microlocal analysis shows that the energy density associated with the high-frequency vibrations of a three-dimensional Timoshenko beam satisfies a Liouville-type transport equation. In the present application, the material of the beam is assumed to be isotropic. Its parameters are allowed to vary along the beam axis at length scales much larger than the wavelength of the high-frequency waves traveling in it. Moreover, the curvature and torsion of the beam are accounted for. The first part of the paper focuses on the derivation of the transport model for a single three-dimensional beam. In order to extend this model to beam trusses, the reflection/transmission phenomena of the energy fluxes at junctions of beams are described by power flow reflection/transmission operators in a subsequent part. For numerical simulations, a discontinuous Galerkin finite element method is used on account of the discontinuities of the energy density field at the junctions. Thus, a complete mechanical-numerical modeling of the linear transient dynamics of beam trusses is proposed. It is illustrated by numerical examples highlighting some remarkable features of high-frequency vibrations: The onset of a diffusive regime characterized by energy equipartition rules at late times. Energy diffusion is prompted by the multiple reflection/transmission of waves at the junctions, with possible mode (polarization) conversions. This is the regime applicable to the statistical energy analysis of structural acoustics systems. The main purpose of this research is to develop an effective strategy to simulate and predict the transient response of beam trusses impacted by acoustic or mechanical shocks.
Deplano, V.; Pelissier, R.; Rieu, R.; Bontoux, P.
1994-01-01
Bifurcations are vascular singularities of interest because they are the privileged sites of atherosclerosis deposits, particularly the sites corresponding to wall shear stress extrema. The purpose of this paper is to compare the two- and three-dimensional characteristics of the velocity fields, the shear stress distributions and the secondary flows in a symmetrical aortic bifurcation. The branching angle is equal to 60^{circ} and the branch-to-trunk area ratio to 0.8. The numerical simulations are performed using the FIDAP programme. Although restrictive by the hypotheses of steady flow and rigid channel, with rectangular cross-sections, this study shows the importance of the three-dimensional effects in particular as far as concerned the wall shear stress behaviours. Les bifurcations sont des singularités vasculaires présentant un intérêt particulier car elles sont le site privilégié de dépôts athéromateux ; la localisation de ces dépôts dépendant des valeurs maximum du cisaillement en paroi. L'objectif de cette étude est de comparer les caractéristiques bidimensionnels et tridimensionnels des champs de vitesse, de la distribution du cisaillement pariétal et des écoulements secondaires dans un modèle de bifurcation aortique. L'angle de bifurcation est de 60^{circ} et le rapport des sections branche fille branche mère est de 0,8. Les simulations numériques sont effectuées sur la base du logiciel FIDAP. Bien que restrictifs de part certaines hypothèses, écoulement permanent dans un modèle de bifurcation rigide avec des sections rectangulaires, ces travaux montrent l'importance des effets tridimensionnels notamment au niveau du cisaillement pariétal.
Three-dimensional simulation of pseudopod-driven swimming of amoeboid cells
Campbell, Eric; Bagchi, Prosenjit
2016-11-01
Pseudopod-driven locomotion is common in eukaryotic cells, such as amoeba, neutrophils, and cancer cells. Pseudopods are protrusions of the cell body that grow, bifurcate, and retract. Due to the dynamic nature of pseudopods, the shape of a motile cell constantly changes. The actin-myosin protein dynamics is a likely mechanism for pseudopod growth. Existing theoretical models often focus on the acto-myosin dynamics, and not the whole cell shape dynamics. Here we present a full 3D simulation of pseudopod-driven motility by coupling a surface-bound reaction-diffusion (RD) model for the acto-myosin dynamics, a continuum model for the cell membrane deformation, and flow of the cytoplasmic and extracellular fluids. The whole cell is represented as a viscous fluid surrounded by a membrane. A finite-element method is used to solve the membrane deformation, and the RD model on the deforming membrane, while a finite-difference/spectral method is used to solve the flow fields inside and outside the cell. The fluid flow and cell deformation are coupled by the immersed-boundary method. The model predicts pseudopod growth, bifurcation, and retraction as observed for a swimming amoeba. The work provides insights on the role of membrane stiffness and cytoplasmic viscosity on amoeboid swimming. Funded by NSF CBET 1438255.
Three-dimensional simulation of slip-streaming in vehicle aerodynamics
Mitra, Saurav
2013-11-01
Simulation of slip-streaming in vehicle aerodynamics is computationally challenging. To resolve turbulent wakes, and estimate drag between two co-linear vehicles with less number of computational cells requires advanced techniques. In this study, the variation of drag reduction and increase arising due to different inter-spacing between two Ahmed vehicles bodies (canonical vehicle geometry with 30° slant back angle) are presented. The computational fluid dynamics solver CONVERGE was used, for its automatic mesh refinement (AMR) capabilities. AMR is based on the second derivative of shear and normal components of velocity gradients and was used to resolve the flow around geometric features such as the frontal area, the slant back, etc. Steady-state density-based solver is used where each cell has its own pseudo time-step based on the local numerical stability criterion. The RNG k- ɛ turbulence model was used to model turbulence. The non-dimensional inter-spacing based on vehicle length, was varied from 0.1 to 2.0. The largest grid size used here was 0.04 m and the smallest was 0.005 m to resolve the turbulent wake which is characterized by a strong vortex system, longitudinal counter-rotating vortices arising from the slant back.
Three-dimensional simulations of a rising bubble in a self-rewetting fluid
Premlata, Amarnath; Tripathi, Manoj; Sahu, Kirti; Karapetsas, George; Sefiane, Khellil; Matar, Omar
2015-11-01
The motion of a gas bubble in a square channel with linearly increasing temperature in the vertical direction is investigated via 3D numerical simulations. The channel contains a so-called ``self-rewetting'' fluid whose surface tension exhibits a parabolic dependence on temperature with a well-defined minimum. An open-source finite-volume fluid flow solver, Gerris, is used with a dynamic adaptive grid refinement technique, based on the vorticity magnitude and position of the interface. We find that in self-rewetting fluids, the buoyancy-induced upward motion of the bubble is retarded by a thermocapillary-driven flow, which occurs as the bubble crosses the location at which the surface tension is minimum. The bubble then migrates downwards when thermocapillarity exceeds buoyancy. In its downward path, the bubble encounters regions of horizontal temperature gradients, which lead to bubble motion towards one of the channel walls. These phenomena are observed at sufficiently small Bond numbers and have no analogue for fluids whose surface tension decreases linearly with temperature. The mechanisms underlying these phenomena are elucidated by considering how the surface tension dependence on temperature affects the thermocapillary stresses in the flow. EPSRC Programme Grant, MEMPHIS, EP/K0039761/1.
The physical structure of radio galaxies explored with three-dimensional simulations
Donohoe, Justin
2016-01-01
We present a large systematic study of hydrodynamic simulations of supersonic adiabatic jets in three dimensions to provide a definitive set of results on exploring jet density, Mach number and precession angle as variables. We restrict the set-up to non-relativistic pressure-equilibrium flows into a homogeneous environment. We first focus on the distribution and evolution of physical parameters associated with radio galaxies. We find that the jet density has limited influence on the structure for a given jet Mach number. The speed of advance varies by a small factor for jet densities between 0.1 and 0.0001 of the ambient density while the cocoon and cavity evolution change from narrow pressure balanced to wide over-pressure as the ratio falls. We also find that the fraction of energy transferred to the ambient medium increases with decreasing jet-ambient density ratio, reaching approx 80%. This energy is predominantly in thermal energy with almost all the remainder in ambient kinetic form. The total energy r...
Magnetic field evolution in magnetar crusts through three-dimensional simulations
Gourgouliatos, Konstantinos N.; Wood, Toby S.; Hollerbach, Rainer
2016-04-01
Current models of magnetars require extremely strong magnetic fields to explain their observed quiescent and bursting emission, implying that the field strength within the star’s outer crust is orders of magnitude larger than the dipole component inferred from spin-down measurements. This presents a serious challenge to theories of magnetic field generation in a proto-neutron star. Here, we present detailed modeling of the evolution of the magnetic field in the crust of a neutron star through 3D simulations. We find that, in the plausible scenario of equipartition of energy between global-scale poloidal and toroidal magnetic components, magnetic instabilities transfer energy to nonaxisymmetric, kilometer-sized magnetic features, in which the local field strength can greatly exceed that of the global-scale field. These intense small-scale magnetic features can induce high-energy bursts through local crust yielding, and the localized enhancement of Ohmic heating can power the star’s persistent emission. Thus, the observed diversity in magnetar behavior can be explained with mixed poloidal-toroidal fields of comparable energies.
Three-dimensional Hybrid Continuum-Atomistic Simulations for Multiscale Hydrodynamics
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Wijesinghe, S; Hornung, R; Garcia, A; Hadjiconstantinou, N
2004-04-15
We present an adaptive mesh and algorithmic refinement (AMAR) scheme for modeling multi-scale hydrodynamics. The AMAR approach extends standard conservative adaptive mesh refinement (AMR) algorithms by providing a robust flux-based method for coupling an atomistic fluid representation to a continuum model. The atomistic model is applied locally in regions where the continuum description is invalid or inaccurate, such as near strong flow gradients and at fluid interfaces, or when the continuum grid is refined to the molecular scale. The need for such ''hybrid'' methods arises from the fact that hydrodynamics modeled by continuum representations are often under-resolved or inaccurate while solutions generated using molecular resolution globally are not feasible. In the implementation described herein, Direct Simulation Monte Carlo (DSMC) provides an atomistic description of the flow and the compressible two-fluid Euler equations serve as our continuum-scale model. The AMR methodology provides local grid refinement while the algorithm refinement feature allows the transition to DSMC where needed. The continuum and atomistic representations are coupled by matching fluxes at the continuum-atomistic interfaces and by proper averaging and interpolation of data between scales. Our AMAR application code is implemented in C++ and is built upon the SAMRAI (Structured Adaptive Mesh Refinement Application Infrastructure) framework developed at Lawrence Livermore National Laboratory. SAMRAI provides the parallel adaptive gridding algorithm and enables the coupling between the continuum and atomistic methods.
Three-Dimensional Simulations of Jets from Keplerian Disks Self--Regulatory Stability
Ouyed, R; Pudritz, R E
2002-01-01
We present the extension of previous two-dimensional simulations of the time-dependent evolution of non-relativistic outflows from the surface of Keplerian accretion disks, to three dimensions. The accretion disk itself is taken to provide a set of fixed boundary conditions for the problem. The 3-D results are consistent with the theory of steady, axisymmetric, centrifugally driven disk winds up to the Alfv\\'en surface of the outflow. Beyond the Alfv\\'en surface however, the jet in 3-D becomes unstable to non-axisymmetric, Kelvin-Helmholtz instabilities. We show that jets maintain their long-term stability through a self-limiting process wherein the average Alfv\\'enic Mach number within the jet is maintained to order unity. This is accomplished in at least two ways. First, poloidal magnetic field is concentrated along the central axis of the jet forming a ``backbone'' in which the Alfv\\'en speed is sufficiently high to reduce the average jet Alfv\\'enic Mach number to unity. Second, the onset of higher order K...
Three-dimensional numerical simulation of red blood cell motion in Poiseuille flows
Shi, Lingling; Pan, Tsorng-Whay; Glowinski, Roland
2014-11-01
An immersed boundary method based on a finite element method has been successfully combined with an elastic spring network model for simulating the dynamical behavior of a red blood cell (RBC) in Poiseuille flows. This elastic spring network preserves the biconcave shape of the RBC in the sense that after the removal of the body force for driving the Poiseuille flow, a RBC with its typical parachute shape in a tube does restore its biconcave resting shape. As a benchmark test, the relationship between the deformation index and the capillary number of the RBCs flowing through a narrow cylindrical tube has been validated. For the migration properties of a single cell in a slit Poiseuille flow, a slipper shape accompanied by a cell membrane tank-treading motion is obtained for Re >= 0 . 03 and the cell mass center is away from the center line of the channel due to its asymmetric slipper shape. For the lower Re wheel during the migration. The lower Reynolds number is, the longer the rolling motion lasts. This work is supported by an NSF Grant No. DMS-0914788.
Larwood, J D; Papaloizou, J C B; Terquem, C
1996-01-01
We present the results of non linear, hydrodynamic simulations, in three dimensions, of the tidal perturbation of accretion discs in binary systems where the orbit is circular and not necessarily coplanar with the disc mid-plane. The accretion discs are assumed to be geometrically thin, and of low mass relative to the stellar mass so that they are governed by thermal pressure and viscosity, but not self-gravity. The parameters that we consider in our models are the ratio of the orbital distance to the disc radius, D/R, the binary mass ratio, the initial inclination angle between the orbit and disc planes and the Mach number in the outer parts of the unperturbed disc. For binary mass ratios of around unity and D/R in the range 3 to 4, we find that the global evolution of the discs is governed primarily by the value of the Mach number. For relatively low Mach numbers (i.e. 10 to 20) we find that the discs develop a mildly warped structure, are tidally truncated, and undergo a near rigid body precession at a rat...
Three-Dimensional Simulations of Core-Collapse Supernovae: From Shock Revival to Shock Breakout
Wongwathanarat, Annop; Janka, H -Thomas
2014-01-01
We present 3D simulations of core-collapse supernovae from blast-wave initiation by the neutrino-driven mechanism to shock breakout from the stellar surface, considering two 15 Msun red supergiants (RSG) and two blue supergiants (BSG) of 15 Msun and 20 Msun. We demonstrate that the metal-rich ejecta in homologous expansion still carry fingerprints of asymmetries at the beginning of the explosion, but the final metal distribution is massively affected by the detailed progenitor structure. The most extended and fastest metal fingers and clumps are correlated with the biggest and fastest-rising plumes of neutrino-heated matter, because these plumes most effectively seed the growth of Rayleigh-Taylor (RT) instabilities at the C+O/He and He/H composition-shell interfaces after the passage of the SN shock. The extent of radial mixing, global asymmetry of the metal-rich ejecta, RT-induced fragmentation of initial plumes to smaller-scale fingers, and maximal Ni and minimal H velocities do not only depend on the initi...
Delorey, A. A.; Frankel, A. D.; Stephenson, W. J.; Liu, P.
2011-12-01
Using a finite-fault rupture model, we ran a finite difference code to simulate a variety of Mw 8 and larger events on the Cascadia subduction zone using a 3D regional velocity model and two different 3D velocity models for the Seattle basin. Our results reveal the magnitude and duration of shaking that should be expected in the built environment for a megathrust event with a rupture length less than the entire length of the subduction zone. In the next step we will consider events that rupture the entire length of the subduction zone, similar in scope to the 1700 event, and compare our results to those considered for the national seismic hazard maps. In order to make predictions on the strength and duration of shaking in Cascadia due to a large megathrust event, we developed a kinematic fault rupture model based on a k-2 decay in final slip spectrum that has a scale-dependent rise time. This produces a ω-2 decay in the radiated displacement spectrum above the corner frequency, which is then modified by rupture directivity. In order to produce a k-2 decay in the final slip spectrum, we modeled the final slip as the sum of asperities with various wave numbers produced by calculating normal modes for a membrane, then shifting the phase of the standing waves to randomize the pattern. In this way, slip naturally decays towards the edges of the rupture without having to use a taper, we can produce a final slip model with any spectrum we choose, and each wave number can be assigned a unique rise time. The slip on each individual asperity initiates in time according to its closest distance to the hypocenter and the rupture velocity. The Cascadia subduction zone off the coast of northwestern United States and southwestern Canada is capable of producing megathrust earthquakes with magnitudes up to Mw 9.0 for margin-wide events and magnitudes greater than Mw 8.0 if only part of the subduction zone ruptures. The average recurrence interval for margin-wide megathrust
Directory of Open Access Journals (Sweden)
Bittner James
2008-01-01
Full Text Available Laparoscopy requires the development of technical skills distinct from those used in open procedures. Several factors extending the learning curve of laparoscopy include ergonomic and technical difficulties, such as the fulcrum effect and limited degrees of freedom. This study aimed to establish the impact of four variables on performance of two simulated laparoscopic tasks. Methods: Six subjects including novice (n=2, intermediate (n=2 and expert surgeons completed two tasks: 1 four running sutures, 2 simple suture followed by surgeon′s knot plus four square knots. Task variables were suturing angle (left/right, needle holder type (standard/articulating and visualisation (2D/3D. Each task with a given set of variables was completed twice in random order. The endpoints included suturing task completion time, average and maximum distance from marks and knot tying task completion time. Results: Suturing task completion time was prolonged by 45-degree right angle suturing, articulating needle holder use and lower skill levels (all P < 0.0001. Accuracy also decreased with articulating needle holder use (both P < 0.0001. 3D vision affected only maximum distance ( P =0.0108. For the knot tying task, completion time was greater with 45-degree right angle suturing ( P =0.0015, articulating needle holder use ( P < 0.0001, 3D vision ( P =0.0014 and novice skill level ( P =0.0003. Participants felt that 3D visualisation offered subjective advantages during training. Conclusions: Results suggest construct validity. A 3D personal head display and articulating needle holder do not immediately improve task completion times or accuracy and may increase the training burden of laparoscopic suturing and knot tying.
Zhang, Gong; Yuan, Hai; Chen, Xianshuai; Wang, Weijun; Chen, Jianyu; Liang, Jimin; Zhang, Peng
2016-01-01
Background/Purpose. This three-dimensional finite element study observed the stress distribution characteristics of 12 types of dental implants and their surrounding bone tissues with various structured abutments, implant threads, and healing methods under different amounts of concentrated loading. Materials and Methods. A three-dimensional geometrical model of a dental implant and its surrounding bone tissue was created; the model simulated a screw applied with a preload of 200 N or a torque...
Simulação tridimensional da laringe Three-dimensional simulation of the larynx
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Marcelo de Oliveira Rosa
2003-01-01
Full Text Available FORMA DE ESTUDO: Experimental. MÉTODO: Um modelo matemático das equações aerodinâmicas e viscoelásticas da laringe, reproduzindo suas características anatômicos e fisiológicos, é proposto para simular a laringe durante a fonação. OBJETIVO: Fornecer uma ferramenta nova para a disciplina de otorrinolaringologia de maneira a compreender melhor os fenômenos físicos presentes na fonação, tanto em casos normais quanto em patológicos. RESULTADO: Os resultados obtidos mostram que diversos fenômenos físicos como a diferença de fase horizontal e vertical entre os movimentos da superfície das pregas vocais, a formação de pressão negativa sobre a porção superior da glote e a formação de torvelinhos após a constrição glotal são reproduzidos pelo modelo. Adicionalmente, estudos teóricos sobre algumas doenças da laringe são apresentados e discutidos, sugerindo que avaliações prévias e "virtuais" de intervenções cirúrgicas serão passíveis de realização.STUDY DESIGN: Experimental. METHOD: A mathematical model of the aerodynamic and viscoelastic equations of the larynx, reproducing its anatomic and physiologic characteristics, is proposed to simulate the organ during phonation. AIM: Its objective is to provide a new tool to the discipline of otorhinolaryngology in order to better understand the physical phenomena present in phonation, both in normal and pathologic cases. RESULTS: The obtained results showed several physical phenomena, such as the horizontal and vertical phase difference among the vocal fold surface movements, the formation of negative pressure over the superior portion of the glottis, and vortex formation after the glottal constriction are reproduced by the model. Additionally, theoretical studies about some laryngeal diseases are presented and discussed, suggesting that previous and "virtual" evaluations of surgical interventions will be feasible in the future.
Shen, Fang; Zhang, Jie; Hess, Phillip; Wang, Yuming; Feng, Xueshang; Cheng, Hongze; Yang, Yi
2015-01-01
The dynamic process of coronal mass ejections (CMEs) in the heliosphere provides us the key information for evaluating CMEs' geo-effectiveness and improving the accurate prediction of CME induced Shock Arrival Time (SAT) at the Earth. We present a data constrained three dimensional (3D) magnetohydrodynamic (MHD) simulation of the evolution of the CME in a realistic ambient solar wind for the July 12-16, 2012 event by using the 3D COIN-TVD MHD code. A detailed comparison of the kinematic evolution of the CME between the observations and the simulation is carried out, including the usage of the time-elongation maps from the perspectives of both Stereo A and Stereo B. In this case study, we find that our 3D COIN-TVD MHD model, with the magnetized plasma blob as the driver, is able to re-produce relatively well the real 3D nature of the CME in morphology and their evolution from the Sun to Earth. The simulation also provides a relatively satisfactory comparison with the in-situ plasma data from the Wind spacecraf...
Mehdipour, R.; Baniamerian, Z.; Delauré, Y.
2016-05-01
An accurate knowledge of heat transfer and temperature distribution in vehicle engines is essential to have a good management of heat transfer performance in combustion engines. This may be achieved by numerical simulation of flow through the engine cooling passages; but the task becomes particularly challenging when boiling occurs. Neglecting two phase flow processes in the simulation would however result in significant inaccuracy in the predictions. In this study a three dimensional numerical model is proposed using Fluent 6.3 to simulate heat transfer of fluid flowing through channels of conventional size. Results of the present theoretical and numerical model are then compared with some empirical results. For high fluid flow velocities, departure between experimental and numerical results is about 9 %, while for lower velocity conditions, the model inaccuracy increases to 18 %. One of the outstanding capabilities of the present model, beside its ability to simulate two phase fluid flow and heat transfer in three dimensions, is the prediction of the location of bubble formation and condensation which can be a key issue in the evaluation of the engine performance and thermal stresses.
Abe, H; Wako, H
2006-07-01
Folding and unfolding simulations of three-dimensional lattice proteins were analyzed using a simplified statistical mechanical model in which their amino acid sequences and native conformations were incorporated explicitly. Using this statistical mechanical model, under the assumption that only interactions between amino acid residues within a local structure in a native state are considered, the partition function of the system can be calculated for a given native conformation without any adjustable parameter. The simulations were carried out for two different native conformations, for each of which two foldable amino acid sequences were considered. The native and non-native contacts between amino acid residues occurring in the simulations were examined in detail and compared with the results derived from the theoretical model. The equilibrium thermodynamic quantities (free energy, enthalpy, entropy, and the probability of each amino acid residue being in the native state) at various temperatures obtained from the simulations and the theoretical model were also examined in order to characterize the folding processes that depend on the native conformations and the amino acid sequences. Finally, the free energy landscapes were discussed based on these analyses.
Fang, Ye; Feng, Sheng; Tam, Ka-Ming; Yun, Zhifeng; Moreno, Juana; Ramanujam, J.; Jarrell, Mark
2014-10-01
Monte Carlo simulations of the Ising model play an important role in the field of computational statistical physics, and they have revealed many properties of the model over the past few decades. However, the effect of frustration due to random disorder, in particular the possible spin glass phase, remains a crucial but poorly understood problem. One of the obstacles in the Monte Carlo simulation of random frustrated systems is their long relaxation time making an efficient parallel implementation on state-of-the-art computation platforms highly desirable. The Graphics Processing Unit (GPU) is such a platform that provides an opportunity to significantly enhance the computational performance and thus gain new insight into this problem. In this paper, we present optimization and tuning approaches for the CUDA implementation of the spin glass simulation on GPUs. We discuss the integration of various design alternatives, such as GPU kernel construction with minimal communication, memory tiling, and look-up tables. We present a binary data format, Compact Asynchronous Multispin Coding (CAMSC), which provides an additional 28.4% speedup compared with the traditionally used Asynchronous Multispin Coding (AMSC). Our overall design sustains a performance of 33.5 ps per spin flip attempt for simulating the three-dimensional Edwards-Anderson model with parallel tempering, which significantly improves the performance over existing GPU implementations.
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Panagiotis K. Siogkas
2015-01-01
Full Text Available Pressure measurements using finite element computations without the need of a wire could be valuable in clinical practice. Our aim was to compare the computed distal coronary pressure values with the measured values using a pressure wire, while testing the effect of different boundary conditions for the simulation. Eight coronary arteries (lumen and outer vessel wall from six patients were reconstructed in three-dimensional (3D space using intravascular ultrasound and biplane angiographic images. Pressure values at the distal and proximal end of the vessel and flow velocity values at the distal end were acquired with the use of a combo pressure-flow wire. The 3D lumen and wall models were discretized into finite elements; fluid structure interaction (FSI and rigid wall simulations were performed for one cardiac cycle both with pulsatile and steady flow in separate simulations. The results showed a high correlation between the measured and the computed coronary pressure values (coefficient of determination [r2] ranging between 0.8902 and 0.9961, while the less demanding simulations using steady flow and rigid walls resulted in very small relative error. Our study demonstrates that computational assessment of coronary pressure is feasible and seems to be accurate compared to the wire-based measurements.
Bauer, S; Röder, G; Bär, M
2007-03-01
Cardiac propagation is investigated by simulations using a realistic three-dimensional (3D) geometry including muscle fiber orientation of the ventricles of a rabbit heart and the modified Beeler-Reuter ionic model. Electrical excitation is introduced by a periodic pacing of the lower septum. Depending on the pacing frequency, qualitatively different dynamics are observed, namely, normal heart beat, T-wave alternans, and 2:1 conduction block at small, intermediate, and large pacing frequencies, respectively. In a second step, we performed a numerical stability and bifurcation analysis of a pulse propagating in a one-dimensional (1D) ring of cardiac tissue. The precise onset of the alternans instability is obtained from computer-assisted linear stability analysis of the pulse and computation of the associated spectrum. The critical frequency at the onset of alternans and the profiles of the membrane potential agree well with the ones obtained in the 3D simulations. Next, we computed changes in the wave profiles and in the onset of alternans for the Beeler-Reuter model with modifications of the sodium, calcium, and potassium channels, respectively. For this purpose, we employ the method of numerical bifurcation and stability analysis. While blocking of calcium channels has a stabilizing effect, blocked sodium or potassium channels lead to the occurrence of alternans at lower pacing frequencies. The findings regarding channel blocking are verified within three-dimensional simulations. Altogether, we have found T-wave alternans and conduction block in 3D simulations of a realistic rabbit heart geometry. The onset of alternans has been analyzed by numerical bifurcation and stability analysis of 1D wave trains. By comparing the results of the two approaches, we find that alternans is not strongly influenced by ingredients such as 3D geometry and propagation anisotropy, but depends mostly on the frequency of pacing (frequency of subsequent action potentials). In addition
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Doroshenko Sergey Aleksandrovich
2012-10-01
Full Text Available The authors discuss wind loads applied to a set of two buildings. The wind load is simulated with the help of the wind tunnel. In the Russian Federation, special attention is driven to the aerodynamics of high-rise buildings and structures. According to the Russian norms, identification of aerodynamic coefficients for high-rise buildings, as well as the influence of adjacent buildings and structures, is performed on the basis of models of structures exposed to wind impacts simulated in the wind tunnel. This article deals with the results of the wind tunnel test of buildings. The simulation was carried out with the involvement of a model of two twenty-three storied buildings. The experiment was held in a wind tunnel of the closed type at in the Institute of Mechanics of Moscow State University. Data were compared at the zero speed before and after the experiment. LabView software was used to process the output data. Graphs and tables were developed in the Microsoft Excel package. GoogleSketchUp software was used as a visualization tool. The three-dimensional flow formed in the wind tunnel can't be adequately described by solving the two-dimensional problem. The aerodynamic experiment technique is used to analyze the results for eighteen angles of the wind attack.
Chiavassa, A; Faurobert, M; Ricort, G; Tanga, P; Magic, Z; Collet, R; Asplund, M
2015-01-01
Stellar activity and, in particular, convection-related surface structures, potentially cause fluctuations that can affect the transit light curves. Surface convection simulations can help the interpretation of ToV. We used realistic three-dimensional radiative hydrodynamical simulation of the Sun from the Stagger-grid and synthetic images computed with the radiative transfer code Optim3D to provide predictions for the transit of Venus in 2004 observed by the satellite ACRIMSAT. We computed intensity maps from RHD simulation of the Sun and produced synthetic stellar disk image. We computed the light curve and compared it to the ACRIMSAT observations and also to the light curves obtained with solar surface representations carried out using radial profiles with different limb-darkening laws. We also applied the same spherical tile imaging method to the observations of center-to-limb Sun granulation with HINODE. We managed to explain ACRIMSAT observations of 2004 ToV and showed that the granulation pattern cause...
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
An asynchronous and parallel time-marching method for three-dimensional (3D) time-dependent magnetohydrodynamic (MHD) simulation is used for large-scale solar wind simulation. It uses different local time steps in the corona and the heliosphere according to the local Courant-Friedrichs-Levy (CFL) conditions. The solar wind background with observed solar photospheric magnetic field as input is first presented. The simulation time for the background solar wind by using the asynchronous method is <1/6 of that by using the normal synchronous time-marching method with the same computation precision. Then, we choose the coronal mass ejection (CME) event of 13 November, 2003 as a test case. The time-dependent variations of the pressure and the velocity configured from a CME model at the inner boundary are applied to generate transient structures in order to study the dynamical interaction of a CME with the background solar wind flow between 1 and 230 Rs. This time-marching method is very effective in terms of computation time for large-scale 3D time-dependent numerical MHD problem. In this validation study, we find that this 3D MHD model, with the asynchronous and parallel time-marching method, provides a relatively satisfactory comparison with the ACE spacecraft obser- vations at L1 point.
Huang, Yan-Hua; Yang, Sheng-Qi; Zhao, Jian
2016-12-01
A three-dimensional particle flow code (PFC3D) was used for a systematic numerical simulation of the strength failure and cracking behavior of rock-like material specimens containing two unparallel fissures under conventional triaxial compression. The micro-parameters of the parallel bond model were first calibrated using the laboratory results of intact specimens and then validated from the experimental results of pre-fissured specimens under triaxial compression. Numerically simulated stress-strain curves, strength and deformation parameters and macro-failure modes of pre-fissured specimens were all in good agreement with the experimental results. The relationship between stress and the micro-crack numbers was summarized. Crack initiation, propagation and coalescence process of pre-fissured specimens were analyzed in detail. Finally, horizontal and vertical cross sections of numerical specimens were derived from PFC3D. A detailed analysis to reveal the internal damage behavior of rock under triaxial compression was carried out. The experimental and simulated results are expected to improve the understanding of the strength failure and cracking behavior of fractured rock under triaxial compression.
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Hassan Badreddine
2017-01-01
Full Text Available The current work focuses on the development and application of a new finite volume immersed boundary method (IBM to simulate three-dimensional fluid flows and heat transfer around complex geometries. First, the discretization of the governing equations based on the second-order finite volume method on Cartesian, structured, staggered grid is outlined, followed by the description of modifications which have to be applied to the discretized system once a body is immersed into the grid. To validate the new approach, the heat conduction equation with a source term is solved inside a cavity with an immersed body. The approach is then tested for a natural convection flow in a square cavity with and without circular cylinder for different Rayleigh numbers. The results computed with the present approach compare very well with the benchmark solutions. As a next step in the validation procedure, the method is tested for Direct Numerical Simulation (DNS of a turbulent flow around a surface-mounted matrix of cubes. The results computed with the present method compare very well with Laser Doppler Anemometry (LDA measurements of the same case, showing that the method can be used for scale-resolving simulations of turbulence as well.
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Rodgers, Arthur J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Univ. of California, Berkeley, CA (United States); Dreger, Douglas S. [Univ. of California, Berkeley, CA (United States); Pitarka, Arben [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2015-06-15
We performed three-dimensional (3D) anelastic ground motion simulations of the South Napa earthquake to investigate the performance of different finite rupture models and the effects of 3D structure on the observed wavefield. We considered rupture models reported by Dreger et al. (2015), Ji et al., (2015), Wei et al. (2015) and Melgar et al. (2015). We used the SW4 anelastic finite difference code developed at Lawrence Livermore National Laboratory (Petersson and Sjogreen, 2013) and distributed by the Computational Infrastructure for Geodynamics. This code can compute the seismic response for fully 3D sub-surface models, including surface topography and linear anelasticity. We use the 3D geologic/seismic model of the San Francisco Bay Area developed by the United States Geological Survey (Aagaard et al., 2008, 2010). Evaluation of earlier versions of this model indicated that the structure can reproduce main features of observed waveforms from moderate earthquakes (Rodgers et al., 2008; Kim et al., 2010). Simulations were performed for a domain covering local distances (< 25 km) and resolution providing simulated ground motions valid to 1 Hz.
Li, Lei-Ting; Lin, Y. C.; Li, Ling; Shen, Lu-Ming; Wen, Dong-Xu
2015-03-01
Three-dimensional crystal plasticity finite element (CPFE) method is used to investigate the hot compressive deformation behaviors of 7075 aluminum alloy. Based on the grain morphology and crystallographic texture of 7075 aluminum alloy, the microstructure-based representative volume element (RVE) model was established by the pole figure inversion approach. In order to study the macroscopic stress-strain response and microstructural evolution, the CPFE simulations are performed on the established microstructure-based RVE model. It is found that the simulated stress-strain curves and deformation texture well agree with the measured results of 7075 aluminum alloy. With the increasing deformation degree, the remained initial weak Goss texture component tends to be strong and stable, which may result in the steady flow stress. The grain orientation and grain misorientation have significant effects on the deformation heterogeneity during hot compressive deformation. In the rolling-normal plane, the continuity of strain and misorientation can maintain across the low-angle grain boundaries, while the discontinuity of strain and misorientation is observed at the high-angle grain boundaries. The simulated results demonstrate that the developed CPFE model can well describe the hot compressive deformation behaviors of 7075 aluminum alloy under elevated temperatures.
Okonogi, Shinichi; Kondo, Kosuke; Harada, Naoyuki; Masuda, Hiroyuki; Nemoto, Masaaki; Sugo, Nobuo
2017-05-15
As the anatomical three-dimensional (3D) positional relationship around the anterior clinoid process (ACP) is complex, experience of many surgeries is necessary to understand anterior clinoidectomy (AC). We prepared a 3D synthetic image from computed tomographic angiography (CTA) and magnetic resonance imaging (MRI) data and a rapid prototyping (RP) model from the imaging data using a 3D printer. The objective of this study was to evaluate anatomical reproduction of the 3D synthetic image and intraosseous region after AC in the RP model. In addition, the usefulness of the RP model for operative simulation was investigated. The subjects were 51 patients who were examined by CTA and MRI before surgery. The size of the ACP, thickness and length of the optic nerve and artery, and intraosseous length after AC were measured in the 3D synthetic image and RP model, and reproducibility in the RP model was evaluated. In addition, 10 neurosurgeons performed AC in the completed RP models to investigate their usefulness for operative simulation. The RP model reproduced the region in the vicinity of the ACP in the 3D synthetic image, including the intraosseous region, at a high accuracy. In addition, drilling of the RP model was a useful operative simulation method of AC. The RP model of the vicinity of ACP, prepared using a 3D printer, showed favorable anatomical reproducibility, including reproduction of the intraosseous region. In addition, it was concluded that this RP model is useful as a surgical education tool for drilling.
Roy, N.; Molson, J.; Lemieux, J.-M.; Van Stempvoort, D.; Nowamooz, A.
2016-07-01
Three-dimensional numerical simulations are used to provide insight into the behavior of methane as it migrates from a leaky decommissioned hydrocarbon well into a shallow aquifer. The conceptual model includes gas-phase migration from a leaky well, dissolution into groundwater, advective-dispersive transport and biodegradation of the dissolved methane plume. Gas-phase migration is simulated using the DuMux multiphase simulator, while transport and fate of the dissolved phase is simulated using the BIONAPL/3D reactive transport model. Methane behavior is simulated for two conceptual models: first in a shallow confined aquifer containing a decommissioned leaky well based on a monitored field site near Lindbergh, Alberta, Canada, and secondly on a representative unconfined aquifer based loosely on the Borden, Ontario, field site. The simulations show that the Lindbergh site confined aquifer data are generally consistent with a 2 year methane leak of 2-20 m3/d, assuming anaerobic (sulfate-reducing) methane oxidation and with maximum oxidation rates of 1 × 10-5 to 1 × 10-3 kg/m3/d. Under the highest oxidation rate, dissolved methane decreased from solubility (110 mg/L) to the threshold concentration of 10 mg/L within 5 years. In the unconfined case with the same leakage rate, including both aerobic and anaerobic methane oxidation, the methane plume was less extensive compared to the confined aquifer scenarios. Unconfined aquifers may therefore be less vulnerable to impacts from methane leaks along decommissioned wells. At other potential leakage sites, site-specific data on the natural background geochemistry would be necessary to make reliable predictions on the fate of methane in groundwater.
Ruith, Michael Rudolf
Vortex breakdown of nominally axisymmetric, swirling incompressible jets and wakes issuing into a semi-infinite domain is studied by means of direct numerical simulations, as well as local and global linear stability analyses. From the point of view of specifying conditions at the open boundaries, this class of flows is particularly challenging due to its ability to support traveling waves. Several boundary conditions, ranging from free-slip and various homogeneous Neumann conditions to radiation conditions, are implemented in a staggered grid, finite difference algorithm that solves the unsteady Navier-Stokes equations in cylindrical coordinates by means of a fractional step method. Their advantages and shortcomings are evaluated in detail, and the question of the proper implementation of intermediate step boundary conditions is addressed. The data obtained from a large variety of test simulations points to the radiation condition as the most suitable lateral and outflow boundary condition for both high and low entrainment jets and wakes. A two-parameterc low entrainment velocity profile for which the steady, axisymmetric breakdown is well studied is selected for further investigation. Hence, issues regarding the role of three-dimensionality and unsteadiness with respect to the existence, mode selection, and internal structure of vortex breakdown can be addressed in terms of the two governing parameters and the Reynolds number. Low Reynolds numbers are found to yield flow fields lacking breakdown bubbles or helical breakdown modes even for high swirl. In contrast, highly swirling flows at large Reynolds numbers exhibit bubble, helical or double helical breakdown modes, where the axisymmetric mode is promoted by a jet-like axial velocity profile, while a wake-like profile renders the flow helically unstable and ultimately yields non-axisymmetric breakdown modes. It is shown that a transition from super- to subcritical flow, accurately predicts the parameter
Cool, Derek W; Connolly, Michael J; Sherebrin, Shi; Eagleson, Roy; Izawa, Jonathan I; Amann, Justin; Romagnoli, Cesare; Romano, Walter M; Fenster, Aaron
2010-02-01
To compare the accuracy of biopsy with two-dimensional (2D) transrectal ultrasonography (US) with that of biopsy with conventional three-dimensional (3D) transrectal US and biopsy with guided 3D transrectal US in the guidance of repeat prostate biopsy procedures in a prostate biopsy simulator. The institutional review board approved this retrospective study. Five residents and five experts performed repeat biopsies with a biopsy simulator that contained the transrectal US prostate images of 10 patients who had undergone biopsy. Simulated repeat biopsies were performed with 2D transrectal US, conventional 3D transrectal US, and guided 3D transrectal US (an extension of 3D transrectal US that enables active display of biopsy targets). The modalities were compared on the basis of time per biopsy and how accurately simulated repeat biopsies could be guided to specific targets. The probability for successful biopsy of a repeat target was calculated for each modality. Guided 3D transrectal US was significantly (P < .01) more accurate for simulated biopsy of repeat targets than was 2D or 3D transrectal US, with a biopsy accuracy of 0.86 mm +/- 0.47 (standard deviation), 3.68 mm +/- 2.60, and 3.60 mm +/- 2.57, respectively. Experts had a 70% probability of sampling a prior biopsy target volume of 0.5 cm(3) with 2D transrectal US; however, the probability approached 100% with guided 3D transrectal US. Biopsy accuracy was not significantly different between experts and residents for any modality; however, experts were significantly (P < .05) faster than residents with each modality. Repeat biopsy of the prostate with 2D transrectal US has limited accuracy. Compared with 2D transrectal US, the biopsy accuracy of both experts and residents improved with guided 3D transrectal US but did not improve with conventional 3D transrectal US.
Kim, Chang-Goo; Kim, Woong-Tae
2014-01-01
We use three-dimensional numerical hydrodynamic simulations of the turbulent, multiphase atomic interstellar medium (ISM) to construct and analyze synthetic HI 21 cm emission and absorption lines. Our analysis provides detailed tests of 21 cm observables as physical diagnostics of the atomic ISM. In particular, we construct (1) the "observed" spin temperature, $T_{s,obs}(v_{ch})\\equiv T_B(v_{ch})/[1-e^{-{\\tau}(v_{ch})}]$, and its optical-depth weighted mean T_s,obs; (2) the absorption-corrected "observed" column density, $N_{H,obs}\\propto \\int dv_{ch} T_B(v_{ch}){\\tau}(v_{ch})/[[1-e^{-{\\tau}(v_{ch})}]$; and (3) the "observed" fraction of cold neutral medium (CNM), $f_{c,obs}\\equiv T_c/T_{s,obs}$ for T_c the CNM temperature; we compare each observed parameter with true values obtained from line-of-sight (LOS) averages in the simulation. Within individual velocity channels, T_s,obs(v_ch) is within a factor 1.5 of the true value up to ${\\tau}(v_{ch})\\approx10$. As a consequence, N_H,obs and T_s,obs are respectiv...
Directory of Open Access Journals (Sweden)
Lei Li
2013-01-01
Full Text Available This study of a lee wave event over three-dimensional (3D mountainous terrain in Lantau Island, Hong Kong, using a simulation combining mesoscale model and computational fluid dynamics (CFD model has shown that (1 3D steep mountainous terrain can trigger small scale lee waves under strong wind condition, and the horizontal extent of the wave structure is in a dimension of few kilometers and corresponds to the dimension of the horizontal cross-section of the mountain; (2 the life cycle of the lee wave is short, and the wave structures will continuously form roughly in the same location, then gradually move downstream, and dissipate over time; (3 the lee wave triggered by the mountainous terrain in this case can be categorized into “nonsymmetric vortex shedding” or “turbulent wake,” as defined before based on water tank experiments; (4 the magnitude of the wave is related to strength of wind shear. This study also shows that a simulation combining mesoscale model and CFD can capture complex wave structure in the boundary layer over realistic 3D steep terrain, and have a potential value for operational jobs on air traffic warning, wind energy utilization, and atmospheric environmental assessment.
Li, Hongli; Xu, Xiangde
2017-04-01
Various types of radars with different horizontal and vertical detection ranges are deployed in China, particularly over complex terrain where radar blind zones are common. In this study, a new variational method is developed to correct three-dimensional radar reflectivity data based on hourly ground precipitation observations. The aim of this method is to improve the quality of observations of various types of radar and effectively assimilate operational Doppler radar observations. A mudslide-inducing local rainstorm is simulated by the WRF model with assimilation of radar reflectivity and radial velocity data using LAPS (Local Analysis and Prediction System). Experiments with different radar data assimilated by LAPS are performed. It is found that when radar reflectivity data are corrected using this variational method and assimilated by LAPS, the atmospheric conditions and cloud physics processes are reasonably described. The temporal evolution of radar reflectivity corrected by the variational method corresponds well to observed rainfall. It can better describe the cloud water distribution over the rainfall area and improve the cloud water analysis results over the central rainfall region. The LAPS cloud analysis system can update cloud microphysical variables and represent the hydrometeors associated with strong convective activities over the rainfall area well. Model performance is improved and the simulation of the dynamical processes and moisture transport is more consistent with observation.
Bozkurt, Ozgur; Pennell, Kelly G; Suuberg, Eric M
2009-01-01
This paper presents model simulation results of vapor intrusion into structures built atop sites contaminated with volatile or semi-volatile chemicals of concern. A three-dimensional finite element model was used to investigate the importance of factors that could influence vapor intrusion when the site is characterized by non-homogeneous soils. Model simulations were performed to examine how soil layers of differing properties alter soil gas concentration profiles and vapor intrusion rates into structures. The results illustrate difference in soil gas concentration profiles and vapor intrusion rates between homogeneous and layered soils. The findings support the need for site conceptual models to adequately represent the site's geology when conducting site characterizations, interpreting field data and assessing the risk of vapor intrusion at a given site. For instance, in layered geologies, a lower permeability and diffusivity soil layer between the source and building often limits vapor intrusion rates, even if a higher permeability layer near the foundation permits increased soil gas flow rates into the building. In addition, the presence of water-saturated clay layers can considerably influence soil gas concentration profiles. Therefore, interpreting field data without accounting for clay layers in the site conceptual model could result in inaccurate risk calculations. Important considerations for developing more accurate conceptual site models are discussed in light of the findings.
Miyamoto, K; Oka, M; Ueda, J; Hoson, T; Kamisaka, S
1995-12-01
Plants have evolved on the earth, indicating the morphology, growth and development, and life cycle of plants are highly influenced by gravity as well as other environmental stimuli. Indeed, simulated microgravity on a clinostat or hypergravity on a centrifuge has recently been reported to change the growth and development of plants (Hoson et al. 1992, 1993, 1995, Rasmussen et al. 1994, Kasahara et al. 1995). Senescence is a final drastic phenomenon in life cycle of plants, which is characterized by the loss of total chlorophyll and protein, and/or the formation of the abscission (Osborne 1973, Thimann 1977, Addicott 1982). Many environmental stimuli as well as the qualitative and quantitative changes of plant hormones have been reported to affect plant senescence. Among those stimuli, light is the most important factor to regulate plant senescence (Leopold 1964). Dark condition promotes leaf senescence due to the decrease in endogenous level of cytokinin and/or the increase in that of abscisic acid or ethylene (Tetley and Thimann 1974, Gepstein and Thimann 1980). However, there are few reports concerning the effect of gravity on leaf senescence. Strenuous effort to learn leaf senescence under microgravity condition has been done using a three-dimensional (3-D) clinostat. In this paper, we report that simulated microgravity condition on a 3-D clinostat promoted the senescence of oat leaf segments in the dark. A possible mechanism of microgravity condition on promoting the senescence is also discussed.
Institute of Scientific and Technical Information of China (English)
F.Jafari Bahman; B.Maraghechi
2013-01-01
A three-dimensional simulation of a steady-state amplifier model of a long-wavelength free-electron laser (FEL) with realizable helical wiggler and ion-channel guiding is presented.The set of coupled nonlinear differential equations for electron orbits and fields of TE11 mode in a cylindrical waveguide are solved numerically by the Runge-Kutta algorithm with averages calculated by the Gaussian quadrature technique.Self-fields and space-charge effects are neglected,and the electron beam is assumed to be cold and slippage is ignored.The parameters correspond to the Compton regime.Evolution of the radiation power and growth rate along the wiggler is studied.Ion-channel density is chosen to obtain optimum efficiency.Simulations are preformed for the FEL operating in the neighborhood of 35 GHz and 16.5 GHz for the electron beam energies of 250 keV and 400 keV,respectively.The result of the saturated efficiency was found to be in good agreement with the simple estimation based on the phase-trapping model.
Chromium poisoning in (La,Sr)MnO3 cathode: Three-dimensional simulation of a solid oxide fuel cell
Miyoshi, Kota; Iwai, Hiroshi; Kishimoto, Masashi; Saito, Motohiro; Yoshida, Hideo
2016-09-01
A three-dimensional numerical model of a single solid oxide fuel cell (SOFC) considering chromium poisoning on the cathode side has been developed to investigate the evolution of the SOFC performance over long-term operation. The degradation model applied in the simulation describes the loss of the cathode electrochemical activity as a decrease in the active triple-phase boundary (TPB) length. The calculations are conducted for two types of cell: lanthanum strontium manganite (LSM)/yttria-stabilized zirconia (YSZ)/Ni-YSZ and LSM-YSZ/YSZ/Ni-YSZ. Their electrode microstructures are acquired by imaging with a focused ion beam scanning-electron microscope (FIB-SEM). The simulation results qualitatively reproduce the trends of chromium poisoning reported in the literature. It has been revealed that the performance degradation by chromium is primarily due to an increase in the cathode activation overpotential. In addition, in the LSM-YSZ composite cathode, TPBs in the vicinity of the cathode-electrolyte interface preferentially deteriorate, shifting the active reaction site towards the cathode surface. This also results in an increase in the cathode ohmic loss associated with oxide ion conduction through the YSZ phase. The effects of the cell temperature, the partial pressure of steam at the chromium source, the cathode microstructure, and the cathode thickness on chromium poisoning are also discussed.
Liu, Z W; Roepke, F K; Edelmann, P; Wang, B; Kromer, M; Hillebrandt, W; Han, Z W
2012-01-01
The identity of the progenitor systems of SNe Ia is still uncertain. In the single-degenerate (SD) scenario, the interaction between the SN blast wave and the outer layers of a main sequence (MS) companion star strips off H-rich material which is then mixed into the ejecta. Strong contamination of the SN ejecta with stripped material could lead to a conflict with observations of SNe Ia. This constrains the SD progenitor model. In this work, our previous simulations based on simplified progenitor donor stars have been updated by adopting more realistic progenitor-system models that result from fully detailed, state-of-the-art binary evolution calculations. We use Eggleton's stellar evolution code including the optically thick accretion wind model and the possibility of the effects of accretion disk instabilities to obtain realistic models of companions for different progenitor systems. The impact of the SN blast wave on these companion stars is followed in three-dimensional hydrodynamic simulations employing t...
Furuichi, M.; Kameyama, M.; Kageyama, A.
2007-12-01
Reproducing a realistic plate tectonics with mantle convection simulation is one of the greatest challenges in computational geophysics. We have developed a three dimensional Eulerian numerical procedure toward plate-mantle simulation, which includes a finite deformation of the plate in the mantle convection. Our method, combined with CIP-CSLR (Constrained Interpolation Profile method-Conservative Semi-Lagrangian advection scheme with Rational function) and ACuTE method, enables us to solve advection and force balance equations even with a large and sharp viscosity jump, which marks the interface between the plates and surrounding upper mantle materials. One of the typical phenomena represented by our method is a fluid rope coiling event, where a stream of viscous fluid is poured onto the bottom plane from a certain height. This coiling motion is due to delicate balances between bending, twisting and stretching motions of fluid rope. In the framework of the Eulerian scheme, the fluid rope and surrounding air are treated as a viscosity profile which differs by several orders of magnitude. Our method solves the complex force balances of the fluid rope and air, by a multigrid iteration technique of ACuTE algorithm. In addition, the CIP-CSLR advection scheme allows us to obtain a deforming shape of the fluid rope, as a low diffusive solution in the Eulerian frame of reference. In this presentation, we will show the simulation result of the fluid rope coiling as an accuracy test for our simulation scheme, by comparing with the simplified numerical solution for thin viscous jet.
Seshadri, Banavara R.; Smith, Stephen W.
2007-01-01
Variation in constraint through the thickness of a specimen effects the cyclic crack-tip-opening displacement (DELTA CTOD). DELTA CTOD is a valuable measure of crack growth behavior, indicating closure development, constraint variations and load history effects. Fatigue loading with a continual load reduction was used to simulate the load history associated with fatigue crack growth threshold measurements. The constraint effect on the estimated DELTA CTOD is studied by carrying out three-dimensional elastic-plastic finite element simulations. The analysis involves numerical simulation of different standard fatigue threshold test schemes to determine how each test scheme affects DELTA CTOD. The American Society for Testing and Materials (ASTM) prescribes standard load reduction procedures for threshold testing using either the constant stress ratio (R) or constant maximum stress intensity (K(sub max)) methods. Different specimen types defined in the standard, namely the compact tension, C(T), and middle cracked tension, M(T), specimens were used in this simulation. The threshold simulations were conducted with different initial K(sub max) values to study its effect on estimated DELTA CTOD. During each simulation, the DELTA CTOD was estimated at every load increment during the load reduction procedure. Previous numerical simulation results indicate that the constant R load reduction method generates a plastic wake resulting in remote crack closure during unloading. Upon reloading, this remote contact location was observed to remain in contact well after the crack tip was fully open. The final region to open is located at the point at which the load reduction was initiated and at the free surface of the specimen. However, simulations carried out using the constant Kmax load reduction procedure did not indicate remote crack closure. Previous analysis results using various starting K(sub max) values and different load reduction rates have indicated DELTA CTOD is
Global Non-spherical Oscillations in Three-dimensional 4π Simulations of the H-ingestion Flash
Herwig, Falk; Woodward, Paul R.; Lin, Pei-Hung; Knox, Mike; Fryer, Chris
2014-09-01
We performed three-dimensional simulations of proton-rich material entrainment into 12C-rich He-shell flash convection and the subsequent H-ingestion flash that took place in the post-asymptotic giant branch star Sakurai's object. Observations of the transient nature and anomalous abundance features are available to validate our method and assumptions, with the aim of applying them to very low-metallicity stars in the future. We include nuclear energy feedback from H burning and cover the full 4π geometry of the shell. Runs on 7683 and 15363 grids agree well with each other and have been followed for 1500 minutes and 1200 minutes. After an 850 minute long quiescent entrainment phase, the simulations enter into a global non-spherical oscillation that is launched and sustained by individual ignition events of H-rich fluid pockets. Fast circumferential flows collide at the antipode and cause the formation and localized ignition of the next H-overabundant pocket. The cycle repeats for more than a dozen times while its amplitude decreases. During the global oscillation, the entrainment rate increases temporarily by a factor of ≈100. Entrained entropy quenches convective motions in the upper layer until the burning of entrained H establishes a separate convection zone. The lower-resolution run hints at the possibility that another global oscillation, perhaps even more violent, will follow. The location of the H-burning convection zone agrees with a one-dimensional model in which the mixing efficiency is calibrated to reproduce the light curve. The simulations have been performed at the NSF Blue Waters supercomputer at NCSA.
Ott, Lesley E.
2010-02-18
A three-dimensional (3-D) cloud-scale chemical transport model that includes a parameterized source of lightning NOx on the basis of observed flash rates has been used to simulate six midlatitude and subtropical thunderstorms observed during four field projects. Production per intracloud (PIC) and cloud-to-ground (PCG) flash is estimated by assuming various values of PIC and PCG for each storm and determining which production scenario yields NOx mixing ratios that compare most favorably with in-cloud aircraft observations. We obtain a mean PCG value of 500 moles NO (7 kg N) per flash. The results of this analysis also suggest that on average, PIC may be nearly equal to PCG, which is contrary to the common assumption that intracloud flashes are significantly less productive of NO than are cloud-to-ground flashes. This study also presents vertical profiles of the mass of lightning NOx after convection based on 3-D cloud-scale model simulations. The results suggest that following convection, a large percentage of lightning NOx remains in the middle and upper troposphere where it originated, while only a small percentage is found near the surface. The results of this work differ from profiles calculated from 2-D cloud-scale model simulations with a simpler lightning parameterization that were peaked near the surface and in the upper troposphere (referred to as a “C-shaped” profile). The new model results (a backward C-shaped profile) suggest that chemical transport models that assume a C-shaped vertical profile of lightning NOx mass may place too much mass near the surface and too little in the middle troposphere.
Ge, Yang; Fan, L.-S.
2005-02-01
The hydrodynamics and heat transfer phenomena of a liquid droplet impacting upon a hot flat surface are analyzed based on three-dimensional (3D) numerical simulation considering film-boiling behavior. The 3D level-set method is employed to portray the droplet surface variation during its deformation. The governing equations for the droplet and the surrounding gas phase are solved utilizing the finite-volume method with the arbitrary Lagrangian Eulerian technique. To account for the lubrication resistant effects of the vapor cushion formed by the film-boiling evaporation, a separate vapor flow model is developed to simulate the pressure and velocity distribution along the vapor layer between the droplet and the surface. The temperature fields in all phases and the local evaporation rate on the droplet surface are determined by using a full field heat transfer model. Both the water and n-heptane droplets impacting on the solid wall with different Weber numbers are investigated. The comparisons of the simulation results with the experimental results reported in the literatures are made to substantiate the model presented in this study. Specially, the spreading and recoiling motions of the impacting droplets are reproduced accurately for a wide range of the Weber number. The oscillation of the thickness of the vapor layer and the temperature distribution across the interface are also calculated and compared favorably with the experimental results. As the Weber number increases, the extent of the droplet spreading increases, but the residence time of the droplet on the surface is almost unchanged. Compared to the saturated impacts, the subcooled impact yields a thinner vapor layer and a higher heat transfer rate.
Institute of Scientific and Technical Information of China (English)
吴波; 汪西力; 徐海良
2015-01-01
Based on RNGk-ε turbulence model and sliding grid technique, solid−liquid two-phase three-dimensional (3-D) unsteady turbulence of full passage in slurry pump was simulated by means of Fluent software. The effects of unsteady flow characteristics on solid−liquid two-phase flow and pump performance were researched under design condition. The results show that clocking effect has a significant influence on the flow in pump, and the fluctuation of flow velocity and pressure is obvious, particularly near the volute tongue, at the position of small sections of volute and within diffuser. Clocking effect has a more influence on liquid-phase than on solid-phase, and the wake-jet structure of relative velocity of solid-phase is less obvious than liquid-phase near the volute tongue and the impeller passage outlet. The fluctuation of relative velocity of solid-phase flow is 7.6% smaller than liquid-phase flow at the impeller outlet on circular path. Head and radial forces of the impeller are 8.1% and 85.7% of fluctuation, respectively. The results provide a theoretical basis for further research for turbulence, improving efficient, reducing the hydraulic losses and wear. Finally, field tests were carried out to verify the operation and wear of slurry pump.
Three-dimensional simulation studies of 10 MeV, 352.2 MHz drift tube Linac
Indian Academy of Sciences (India)
Nita S Kulkarni
2013-06-01
It is proposed to build a drift tube Linac (DTL) at Raja Ramanna Centre for Advanced Technology, Indore, India, that will form a part of the future Spallation Neutron Source. This DTL will accelerate 30 mA H-ion beam from 3 MeV to 10 MeV. The DTL is designed to operate at 352.2 MHz with a maximum duty cycle of 3%. The DTL tank will consist of three sections, each about 1.2 m in length having 60 cells. The DTL has a ramped accelerating field, which is ramped in the first section of DTL from 1.8 to 2.2 MV/m and remains constant over the rest of the length of DTL. The field in DTL will be stabilized using post-couplers. The three-dimensional (3D) design of the DTL is done using CST microwave studio (CST MWS) incorporating the various nonaxisymmetric components such as tuners, post-couplers and vacuum ports. The frequency shifts due to these components have been evaluated. This paper presents the details of the studies and analysis of 3D simulations of post-couplers, tuners and vacuum ports.
Lin, Hsiu-Hsia; Lo, Lun-Jou
2015-04-01
By incorporating three-dimensional (3D) imaging and computer-aided design and manufacturing techniques, 3D computer-assisted technology has been applied widely to provide accurate guidance for assessment and treatment planning in clinical practice. This technology has recently been used in orthognathic surgery to improve surgical planning and outcome. The modality will gradually become popular. This study reviewed the literature concerning the use of computer-assisted techniques in orthognathic surgery including surgical planning, simulation, intraoperative translation of the virtual surgery, and postoperative evaluation. A Medline, PubMed, ProQuest, and ScienceDirect search was performed to find relevant articles with regard to 3D computer-assisted orthognathic surgery in the past 10 years. A total of 460 articles were revealed, out of which 174 were publications addressed the topic of this study. The purpose of this article is to present an overview of the state-of-art methods for 3D computer-assisted technology in orthognathic surgery. From the review we can conclude that the use of computer-assisted technique in orthognathic surgery provides the benefit of optimal functional and aesthetic results, patient satisfaction, precise translation of the treatment plan, and facilitating intraoperative manipulation.
Watari, Minoru
2009-06-01
Two problems exist in the current studies on the application of the lattice Boltzmann method (LBM) to rarefied gas dynamics. First, most studies so far are applications of two-dimensional models. The numbers of velocity particles are small. Consequently, the boundary-condition methods of these studies are not directly applicable to a multispeed finite-difference lattice Boltzmann method (FDLBM) that has many velocity particles. Second, the LBM and FDLBM share their origins with the Boltzmann equation. Therefore, the results of LBM and FDLBM studies should be verified by the results of the continuous Boltzmann equation. In my review to date on the LBM studies, it appears that such verifications were seldom done. In this study, velocity slip and temperature jump simulations in the slip-flow regime were conducted using a three-dimensional FDLBM model. The results were compared with preceding theoretical studies based on the continuous Boltzmann equation. The results agreed with the theory with errors of a few percent. To further improve the accuracy of the FDLBM, it seems necessary to increase the number of velocity particles.
Energy Technology Data Exchange (ETDEWEB)
Wang, Hsiang-Hsu; Shang, Hsien; Gu, Pin-Gao [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China); Bu, Defu, E-mail: hhwang@asiaa.sinica.edu.tw [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatories, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China)
2014-07-20
The regular satellites found around Neptune (≈17 M{sub ⊕}) and Uranus (≈14.5 M{sub ⊕}) suggest that past gaseous circumplanetary disks may have co-existed with solids around sub-Neptune-mass protoplanets (<17 M{sub ⊕}). These disks have been shown to be cool, optically thin, and quiescent, with low surface densities and low viscosities. Numerical studies of the formation are difficult and technically challenging. As an introductory attempt, three-dimensional global simulations are performed to explore the formation of circumplanetary disks around sub-Neptune-mass protoplanets embedded within an isothermal protoplanetary disk at the inviscid limit of the fluid in the absence of self-gravity. Under such conditions, a sub-Neptune-mass protoplanet can reasonably have a rotationally supported circumplanetary disk. The size of the circumplanetary disk is found to be roughly one-tenth of the corresponding Hill radius, which is consistent with the orbital radii of irregular satellites found for Uranus. The protoplanetary gas accretes onto the circumplanetary disk vertically from high altitude and returns to the protoplanetary disk again near the midplane. This implies an open system in which the circumplanetary disk constantly exchanges angular momentum and material with its surrounding prenatal protoplanetary gas.
Wang, Yue; Wang, Jianguo; Chen, Zaigao; Cheng, Guoxin; Wang, Pan
2016-08-01
To overcome the staircase error in the traditional particle-in-cell (PIC) method, a three dimensional (3D) simple conformal (SC) symplectic PIC method is presented in this paper. The SC symplectic finite integration technique (FIT) scheme is used to advance the electromagnetic fields without reduction of the time step. Particles are emitted from conformal boundaries with the charge conserving emission scheme and moved by using the relativistic Newton-Lorentz force equation. The symplectic formulas of auxiliary-differential equation, complex frequency shifted perfectly matched layer (ADE-CFS-PML) are given for truncating the open boundaries, numerical results show that the maximum relative error of truncation is less than 90 dB. Based on the surface equivalence theorem, the computing algorithms of conformal signals' injection are given, numerical results show that the algorithms can give the right mode patterns and the errors of cutoff frequencies could be as low as 0.1%. To verify the conformal algorithms, a magnetically insulated line oscillator is simulated, and the results are compared to those provided by using the 2.5D UNIPIC code, which show that they agree well. The results also show that the high order symplectic integration method can suppress the numerical Cherenkov radiation.
Takahashi, Hiroyuki R; Kawashima, Tomohisa; Sekiguchi, Yuichiro
2016-01-01
Using three-dimensional general relativistic radiation magnetohydrodynamics simulations of accretion flows around stellar mass black holes, we report that the relatively cold disk ($\\gtrsim 10^{7}$K) is truncated near the black hole. Hot and less-dense regions, of which the gas temperature is $ \\gtrsim 10^9$K and more than ten times higher than the radiation temperature (overheated regions), appear within the truncation radius. The overheated regions also appear above as well as below the disk, and sandwich the cold disk, leading to the effective Compton upscattering. The truncation radius is $\\sim 30 r_{\\rm g}$ for $\\dot{M} \\sim L_{\\rm Edd}/c^2$, where $r_{\\rm g}, \\dot M, L_\\mathrm{Edd}, c$ are the gravitational radius, mass accretion rate, Eddington luminosity, and light speed. Our results are consistent with observations of very high state, whereby the truncated disk is thought to be embedded in the hot rarefied regions. The truncation radius shifts inward to $\\sim 10 r_{\\rm g}$ with increasing mass accret...
Li, Cheng Gong; P-Y Maa, Jerome
2017-04-01
Numerical study on three-dimensional (3D), incompressible, four-sided lid (FSL) driven cavity flows has been conducted to show the effects of the transverse aspect ratio, K, on the flow field by using a multiple relaxation time lattice Boltzmann equation. The top wall is driven from left to right, the left wall is moved downward, whereas the right wall is driven upward, and the bottom wall is moved from right to left, all the four moving walls have the same speed and the others boundaries are fixed. Numerical computations are performed for several Reynolds numbers for laminar flows, up to 1000, with various transverse aspect ratios. The flow can reach a steady state and the flow pattern is symmetric with respect to the two cavity diagonals (i.e., the center of the cavity). At Reynolds number = 300, the flow structures of the 3D FSL cavity flow at steady state with various transverse aspect ratio, i.e., 3, 2, 1, 0.75, 0.5 and 0.25 only show the unstable symmetrical flow pattern. The stable asymmetrical flow pattern could be reproduced only by increasing the Reynolds number that is above a critical value which is dependent on the aspect ratio. It is found that an aspect ratio of more than 5 is needed to reproduce flow patterns, both symmetric and asymmetric flows, simulated by using 2D numerical models.
Takiwaki, Tomoya; Suwa, Yudai
2013-01-01
We present numerical results on two- (2D) and three-dimensional (3D) hydrodynamic core-collapse simulations of an 11.2$M_\\odot$ star. By changing numerical resolutions and seed perturbations systematically, we study how the postbounce dynamics is different in 2D and 3D. The calculations were performed with an energy-dependent treatment of the neutrino transport based on the isotropic diffusion source approximation scheme, which we have updated to achieve a very high computational efficiency. All the computed models in this work including nine 3D models and fifteen 2D models exhibit the revival of the stalled bounce shock, leading to the possibility of explosion. All of them are driven by the neutrino-heating mechanism, which is fostered by neutrino-driven convection and the standing-accretion-shock instability (SASI). Reflecting the stochastic nature of multi-dimensional (multi-D) neutrino-driven explosions, the blast morphology changes from models to models. However, we find that the final fate of the multi-...
Institute of Scientific and Technical Information of China (English)
蔡树群; 甘子钧; 苏纪兰; 刘秦玉
2002-01-01
A three-dimensional baroclinic shelf sea model's numerical simulation of the South China Sea (SCS) middle and deep layer circulation structure showed that: 1. In the SCS middle and deep layer, a southward boundary current exists along the east shore of the Indo-China Peninsula all year long. A cyclonic eddy (gyre) is formed by the current in the above sea areas except in the middle layer in spring, when an anticyclonic eddy exists on the eastern side of the current. In the deep layer, a large-scale anticyclonic eddy often exists in the sea areas between the Zhongsha Islands and west shore of southern Luzon Island. 2. In the middle layer in summer and autumn, and in the deep layer in autumn and winter, there is an anticyclonic eddy (gyre) in the northeastern SCS, while in the middle layer in winter and spring, and in the deep layer in spring and summer, there is a cyclonic one. 3. In the middle layer, there is a weak northeastward current in the Nansha Trough in spring and summer, while in autumn and winter it evolves into an anticyclonic eddy (gyre), which then spreads westward to the whole western Nansha Islands sea areas.
Institute of Scientific and Technical Information of China (English)
崔永章; 田茂诚; 张林华; 李广鹏; 朱建宾
2012-01-01
A three-dimensional numerical model is presented for studying the convection-condensation of mixture with vapor in a tube with edgefold-twisted-tape inserts under transition flow.According to the diffusion layer theory and laminar species transport,a condensation model with user defined function is proposed and compared with heat and mass transfer analogy and experimental test.With the condensation model,the influences of gap width and op-erating parameters on thermal-hydrodynamics performance are simulated.As the gap width increases,convection and condensation heat transfer increase initially and then decrease,while convection heat transfer increases sharply and then decreases slightly.Increasing vapor fraction has a significant effect on condensation heat transfer but it has little effect on convective heat transfer.With the increase of inner wall temperature both convection and condensa-tion heat transfer all decrease and the ratio of condensation to total heat decrease dramatically.Increases inlet tem-perature mainly affects convection heat transfer.
Zhang, Hong-Na; Li, Feng-Chen; Li, Xiao-Bin; Li, Dong-Yang; Cai, Wei-Hua; Yu, Bo
2016-09-01
Direct numerical simulations (DNSs) of purely elastic turbulence in rectilinear shear flows in a three-dimensional (3D) parallel plate channel were carried out, by which numerical databases were established. Based on the numerical databases, the present paper analyzed the structural and statistical characteristics of the elastic turbulence including flow patterns, the wall effect on the turbulent kinetic energy spectrum, and the local relationship between the flow motion and the microstructures’ behavior. Moreover, to address the underlying physical mechanism of elastic turbulence, its generation was presented in terms of the global energy budget. The results showed that the flow structures in elastic turbulence were 3D with spatial scales on the order of the geometrical characteristic length, and vortex tubes were more likely to be embedded in the regions where the polymers were strongly stretched. In addition, the patterns of microstructures’ elongation behave like a filament. From the results of the turbulent kinetic energy budget, it was found that the continuous energy releasing from the polymers into the main flow was the main source of the generation and maintenance of the elastic turbulent status. Project supported by the National Natural Science Foundation of China (Grant Nos. 51276046 and 51506037), the Foundation for Innovative Research Groups of the National Natural Science Foundation of China (Grant No. 51421063), the China Postdoctoral Science Foundation (Grant No. 2016M591526), the Heilongjiang Postdoctoral Fund, China (Grant No. LBH-Z15063), and the China Postdoctoral International Exchange Program.
Three Dimensional Simulation of Liquid Flow on Distillation Tray%精馏塔板液相流场三维模拟
Institute of Scientific and Technical Information of China (English)
刘伯潭; 刘春江
2002-01-01
The liquid flow on a single-pass sieve distillation tray is simulated with a three-dimensional computational fluid dynamics (CFD) program with the K-ε turbulence model. In the model, a source term SMi is formulatedin the Navier-Stokes equations to represent the interfacial momentum transfer and another term Sc is added to themass transfer equation as the source of interfacial mass transfer. The simulation provides the detailed informationof the three-dimensional distribution of liquid velocity on the tray, the circulation area and the concentration profilealong the height of liquid layer.
Lardeau, Sylvain; Ferrari, Simone; Rossi, Lionel
2008-12-01
Three-dimensional (3D) direct numerical simulations of a flow driven by multiscale electromagnetic forcing are performed in order to reproduce with maximum accuracy the quasi-two-dimensional (2D) flow generated by the same multiscale forcing in the laboratory. The method presented is based on a 3D description of the flow and the electromagnetic forcing. Very good agreements between our simulations and the experiments are found both on velocity and acceleration field, this last comparison being, to our knowledge, done for the first time. Such agreement requires that both experiments and simulations are carefully performed and, more importantly, that the underlying simplification to model the experiments and the multiscale electromagnetic forcing do not introduce significant errors. The results presented in this paper differ significantly from previous 2D direct numerical simulation in which a classical linear Rayleigh friction modeling term was used to mimic the effect of the wall-normal friction. Indeed, purely 2D simulations are found to underestimate the Reynolds number and, due to the dominance of nonhomogeneous bottom friction, lead to the wrong physical mechanism. For the range of conditions presented in this paper, the Reynolds number, defined by the ratio between acceleration and viscous terms, remains the order of unity, and the Hartmann number, defined by the ratio between electromagnetic force terms and viscous terms, is about 2. The main conclusion is that 3D simulations are required to model the (3D) electromagnetic forces and the wall-normal shear. Indeed, even if the flow is quasi-2D in terms of energy, a full 3D approach is required to simulate these shallow layer flows driven by multiscale electromagnetic forcing. In the range of forcing intensity investigated in this paper, these multiscale flows remain quasi-2D, with negligible energy in the wall-normal velocity component. It is also shown that the driving terms are the electromagnetic forcing and
Institute of Scientific and Technical Information of China (English)
LU Tao; WANG Kuisheng
2009-01-01
In order to predict the pressure drop, collection efficiency, velocity, temperature and mole fraction of vapor in an industrial venturi scrubber with water spraying for converter gas cooling, a three-dimensional model of heat and mass transfer with phase change is established. The gas flow and liquid droplets are treated as a continuous phase with a Eulerian approach and as a discrete phase with a Lagrangian approach, respectively. The coupled problem of heat, force, and mass transfers between gas flow and liquid droplets is solved by a commercial computational fluid dynamics(CFD) package, FLUENT. The numerical results show that the water injections have an important influence on the distributions of pressure, velocity, temperature, and mole fraction of vapor, especially for the spraying region in the throat. In the spraying region, the pressure drop is higher and the velocity is lower than in other regions due to the gas-droplet drag, while the temperature is lower because the droplet absorbs large amounts of heat from the high temperature gas and the mole fraction of vapor is higher due to the phase change of the liquid droplet. A number of cases with different water-to-gas volume flow ratios and baffle openings were simulated. The dependence of pressure drop, velocity, temperature, mole fraction of vapor, and collection efficiency on both the water-to-gas volume flow ratio and baffle opening are analyzed. The good agreements between simulation results and experiment data of pressure drop, temperature, and collection efficiency validate the model. The model should facilitate optimization of the venturi scrubber design in order to give better performance with lower pressure drops and higher collection efficiency.
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
Water is a primary controlling factor for economic development and ecological environmental protection in the inland river basins of arid western China. And it is groundwater, as the most important component of total water resources, that plays a dominant role in the development of western China. In recent years, the use-ratio of surface water has been raised, the groundwater recharge rate from surface water has been reduced, and groundwater has been exploited on a large scale. This has led to the decline of ground-water levels and the degradation of eco-environments in the Heihe watershed. Therefore, the study on the change in groundwater levels in recent years, as well as simulating and predicting groundwater levels in the future, have become very significant for im-proving the ecological environment of the Heihe River Basin, to coordinate the water contradiction among upper, middle and lower reaches of Heihe River Basin and to allocate the water resources. The purpose of this study is to analyze the groundwa-ter-level variations of the Ejina region based on a large scale, to develop and evaluate a conceptual groundwater model in Ejina Basin, to establish the groundwater flow model using the experimental observation data and combining Modular Three-Dimensional Groundwater Flow Model (MODFLOW) and GIS software, to simulate the regional hydrologic regime in re-cent 10 years and compare various water-delivery scenarios from midstream, and to determine which one would be the best plan for maintaining and recovering the groundwater levels and increasing the area of Ejina oasis. Finally this paper discusses the pos-sible vegetation changes of Ejina Basin in the future.
Wang, Weiling; Luo, Sen; Zhu, Miaoyong
2016-03-01
To improve the computational efficiency of the three-dimensional (3D) cellular-automaton-finite-volume-method (CA-FVM) model for describing the dendritic growth of alloy, the block-correction technique (BCT) and the parallel computation approach are introduced. Accordingly, a serial of investigations on the efficiency of the optimized codes in dealing with the designed cases for the melt flow and the heat transfer problems is carried out. Moreover, the accuracy of the present codes is evaluated by the comparisons between the solution to the melt flow and the heat transfer problems and the results from analytical equations and the commercial software. Additionally, the capability of the present CA model is evaluated by comparing the steady growth parameters of the equiaxed dendritic tip and the morphology and the secondary dendrite arm spacing (SDAS) of columnar dendrites with the LGK analytical model and the experimental results of the unidirectional solidification of high-carbon steels. The results show that with the introduction of the 3D BCT, the iteration process of the serial tri-diagonal matrix algorithm (TDMA) code changes from the fluctuation type to the smooth one, and thus, the computational cost is reduced significantly. Moreover, the parallel Jacobi code with one two-dimensional (2D) iteration in 3D BCT is proved to be the most efficient one among the codes compiled in the present work, and therefore, accordingly it is employed to simulate the 3D dendritic growth of alloys. The calculated velocity distribution and temperature variation agree well with the results from the analytical equations and the commercial software. The predicted steady tip velocities agree with the LGK analytical model as the undercooling is 6 K to 7 K. Moreover, the predicted columnar dendritic morphology and SDAS of high-carbon Fe-C alloys during the unidirectional solidification agree with the experimental results.
Perez Beaupuits, J.P.; Wada, K.; Spaans, M.
2011-01-01
Several attempts have been made to model the mass distribution and dynamical evolution of the circumnuclear gas in active galactic nuclei (AGNs). However, chemical evolution is not included in detail in three-dimensional (3D) hydrodynamic simulations. The X-ray radiation from the AGN can drive the g
Pérez-Beaupuits, J. P.; Wada, K.; Spaans, M.
2011-01-01
Several attempts have been made to model the mass distribution and dynamical evolution of the circumnuclear gas in active galactic nuclei (AGNs). However, chemical evolution is not included in detail in three-dimensional (3D) hydrodynamic simulations. The X-ray radiation from the AGN can drive the g