3D MHD Simulations of Spheromak Compression
Stuber, James E.; Woodruff, Simon; O'Bryan, John; Romero-Talamas, Carlos A.; Darpa Spheromak Team
2015-11-01
The adiabatic compression of compact tori could lead to a compact and hence low cost fusion energy system. The critical scientific issues in spheromak compression relate both to confinement properties and to the stability of the configuration undergoing compression. We present results from the NIMROD code modified with the addition of magnetic field coils that allow us to examine the role of rotation on the stability and confinement of the spheromak (extending prior work for the FRC). We present results from a scan in initial rotation, from 0 to 100km/s. We show that strong rotational shear (10km/s over 1cm) occurs. We compare the simulation results with analytic scaling relations for adiabatic compression. Work performed under DARPA grant N66001-14-1-4044.
3D MHD disruptions simulations of tokamaks plasmas
Paccagnella, Roberto; Strauss, Hank; Breslau, Joshua
2008-11-01
Tokamaks Vertical Displacement Events (VDEs) and disruptions simulations in toroidal geometry by means of a single fluid visco-resistive magneto-hydro-dynamic (MHD) model are presented in this paper. The plasma model, implemented in the M3D code [1], is completed with the presence of a 2D homogeneous wall with finite resistivity. This allows the study of the relatively slowly growing magneto-hydro-dynamical perturbation, the resistive wall mode (RWM), which is, in this work, the main drive of the disruptions. Amplitudes and asymmetries of the halo currents pattern at the wall are also calculated and comparisons with tokamak experimental databases and predictions for ITER are given. [1] W. Park, E.V. Belova, G.Y. Fu, X.Z. Tang, H.R. Strauss, L.E. Sugiyama, Phys. Plasmas 6 (1999) 1796.
Global 3D MHD Simulations of Waves in Accretion Discs
Directory of Open Access Journals (Sweden)
Romanova M.M.
2013-04-01
Full Text Available We discuss results of the first global 3D MHD simulations of warp and density waves in accretion disks excited by a rotating star with a misaligned dipole magnetic field. A wide range of cases are considered. We find for example that if the star’s magnetosphere corotates approximately with the inner disk, then a strong one-arm bending wave or warp forms. The warp corotates with the star and has a maximum amplitude (|zw|/r ~ 0.3 between the corotation radius and the radius of the vertical resonance. If the magnetosphere rotates more slowly than the inner disk, then a bending wave is excited at the disk-magnetosphere boundary, but it does not form a large-scale warp. In this case the angular rotation of the disk [Ω(r] has a maximum as a function of r so that there is an inner region where dΩ/dr > 0. In this region we observe radially trapped density waves in approximate agreement with the theoretical prediction of a Rossby wave instability in this region.
The MHD simulations of 3D magnetic reconnection near null point of magnetic configurations
Energy Technology Data Exchange (ETDEWEB)
Bulanov, S.V. [Institute of General Physics, Russian Academy of Sciences, Moscow (Russian Federation); Echkina, E.Yu; Inovenkov, I.N.; Pichushkin, V.V. [Moscow State University, Moscow (Russian Federation); Pegoraro, F. [Dipartimento di Fisica dell' Universit' a di Pisa and INFM (Italy)
2000-07-01
We investigate 3D plasma flow in the vicinities of critical points of magnetic configurations. The study is based on the analysis of exact self-similar solution of the MHD equations and 3D computer simulations. Both the analytical solution and 3D MHD simulations demonstrate appearance of singular distribution of the electric current density near the magnetic field separatrix surfaces of the form of the current and vortex sheets. (author)
3D MHD simulation of polarized emission in SN 1006
Schneiter, E M; Reynoso, E M; Esquivel, A; De Colle, F
2015-01-01
We use three dimensional magnetohydrodynamic (MHD) simulations to model the supernova remnant SN 1006. From our numerical results, we have carried out a polarization study, obtaining synthetic maps of the polarized intensity, the Stokes parameter $Q$, and the polar-referenced angle, which can be compared with observational results. Synthetic maps were computed considering two possible particle acceleration mechanisms: quasi-parallel and quasi-perpendicular. The comparison of synthetic maps of the Stokes parameter $Q$ maps with observations proves to be a valuable tool to discern unambiguously which mechanism is taking place in the remnant of SN 1006, giving strong support to the quasi-parallel model.
Current systems of coronal loops in 3D MHD simulations
Warnecke, Jörn; Bingert, Sven; Peter, Hardi
2016-01-01
We study the magnetic field and current structure associated with a coronal loop. Through this we investigate to what extent the assumptions of a force-free magnetic field break down. We analyse a three-dimensional MHD model of the solar corona in an emerging active region with the focus on the structure of the forming coronal loops. The lower boundary of this simulation is taken from a model of an emerging active region. As a consequence of the emerging magnetic flux a coronal loop formes self-consistently. We investigate the current density along magnetic field lines inside (and outside) this loop and study the magnetic and plasma properties in and around this loop. The loop is defined as the bundle of field lines that coincides with enhanced emission in extreme UV. We find that the total current along the emerging loop changes its sign from being antiparallel to parallel to the magnetic field. Around the loop the currents form a complex non-force-free helical structure. This is directly related to a bipola...
Photon Scattering in 3D Radiative MHD Simulations
Hayek, Wolfgang
2009-09-01
Recent results from 3D time-dependent radiative hydrodynamic simulations of stellar atmospheres are presented, which include the effects of coherent scattering in the radiative transfer treatment. Rayleigh scattering and electron scattering are accounted for in the source function, requiring an iterative solution of the transfer equation. Opacities and scattering coefficients are treated in the multigroup opacity approximation. The impact of scattering on the horizontal mean temperature structure is investigated, which is an important diagnostic for model atmospheres, with implications for line formation and stellar abundance measurements. We find that continuum scattering is not important for the atmosphere of a metal-poor Sun with metailicity [Fe/H] = -3.0, similar to the previously investigated photosphere at solar metallicity.
3-D Simulations of MHD Jets - The Stability Problem
Nakamura, M; Nakamura, Masanori; Meier, David L.
2003-01-01
Non-relativistic three-dimensional magnetohydrodynamic simulations of Poynting-flux-dominated (PFD) jets are presented. Our study focuses on the propagation of strongly magnetized hypersonic but sub-Alfv\\'enic flow ($C_{\\rm s}^2 1$), driven in large part by the radial component of the Lorentz force.
3D simulations of fluctuation spectra in the hall-MHD plasma.
Shaikh, Dastgeer; Shukla, P K
2009-01-30
Turbulent spectral cascades are investigated by means of fully three-dimensional (3D) simulations of a compressible Hall-magnetohydrodynamic (H-MHD) plasma in order to understand the observed spectral break in the solar wind turbulence spectra in the regime where the characteristic length scales associated with electromagnetic fluctuations are smaller than the ion gyroradius. In this regime, the results of our 3D simulations exhibit that turbulent spectral cascades in the presence of a mean magnetic field follow an omnidirectional anisotropic inertial-range spectrum close to k(-7/3). The latter is associated with the Hall current arising from nonequal electron and ion fluid velocities in our 3D H-MHD plasma model.
3D simulations of disc-winds extending radially self-similar MHD models
Stute, Matthias; Vlahakis, Nektarios; Tsinganos, Kanaris; Mignone, Andrea; Massaglia, Silvano
2014-01-01
Disc-winds originating from the inner parts of accretion discs are considered as the basic component of magnetically collimated outflows. The only available analytical MHD solutions to describe disc-driven jets are those characterized by the symmetry of radial self-similarity. However, radially self-similar MHD jet models, in general, have three geometrical shortcomings, (i) a singularity at the jet axis, (ii) the necessary assumption of axisymmetry, and (iii) the non-existence of an intrinsic radial scale, i.e. the jets formally extend to radial infinity. Hence, numerical simulations are necessary to extend the analytical solutions towards the axis, by solving the full three-dimensional equations of MHD and impose a termination radius at finite radial distance. We focus here on studying the effects of relaxing the (ii) assumption of axisymmetry, i.e. of performing full 3D numerical simulations of a disc-wind crossing all magnetohydrodynamic critical surfaces. We compare the results of these runs with previou...
3D-MHD simulations of the evolution of magnetic fields in FR II radio sources
Huarte-Espinosa, Martin; Alexander, Paul
2010-01-01
3D-MHD numerical simulations of bipolar, hypersonic, weakly magnetized jets and synthetic synchrotron observations are presented to study the structure and evolution of magnetic fields in FR II radio sources. The magnetic field setup in the jet is initially random. The power of the jets as well as the observational viewing angle are investigated. We find that synthetic polarization maps agree with observations and show that magnetic fields inside the sources are shaped by the jets' backflow. Polarimetry statistics correlates with time, the viewing angle and the jet-to-ambient density contrast. The magnetic structure inside thin elongated sources is more uniform than for ones with fatter cocoons. Jets increase the magnetic energy in cocoons, in proportion to the jet velocity. Both, filaments in synthetic emission maps and 3D magnetic power spectra suggest that turbulence develops in evolved sources.
Murphy, G C; Pelletier, Guy
2008-01-01
Magnetic reconnection plays a critical role in many astrophysical processes where high energy emission is observed, e.g. particle acceleration, relativistic accretion powered outflows, pulsar winds and probably in dissipation of Poynting flux in GRBs. The magnetic field acts as a reservoir of energy and can dissipate its energy to thermal and kinetic energy via the tearing mode instability. We have performed 3d nonlinear MHD simulations of the tearing mode instability in a current sheet. Results from a temporal stability analysis in both the linear regime and weakly nonlinear (Rutherford) regime are compared to the numerical simulations. We observe magnetic island formation, island merging and oscillation once the instability has saturated. The growth in the linear regime is exponential in agreement with linear theory. In the second, Rutherford regime the island width grows linearly with time. We find that thermal energy produced in the current sheet strongly dominates the kinetic energy. Finally preliminary ...
Hayek, W; Carlsson, M; Trampedach, R; Collet, R; Gudiksen, B V; Hansteen, V H; Leenaarts, J
2010-01-01
We present the implementation of a radiative transfer solver with coherent scattering in the new BIFROST code for radiative magneto-hydrodynamical (MHD) simulations of stellar surface convection. The code is fully parallelized using MPI domain decomposition, which allows for large grid sizes and improved resolution of hydrodynamical structures. We apply the code to simulate the surface granulation in a solar-type star, ignoring magnetic fields, and investigate the importance of coherent scattering for the atmospheric structure. A scattering term is added to the radiative transfer equation, requiring an iterative computation of the radiation field. We use a short-characteristics-based Gauss-Seidel acceleration scheme to compute radiative flux divergences for the energy equation. The effects of coherent scattering are tested by comparing the temperature stratification of three 3D time-dependent hydrodynamical atmosphere models of a solar-type star: without scattering, with continuum scattering only, and with bo...
Testa, Paola; Martinez-Sykora, Juan; Hansteen, Viggo; Carlsson, Mats
2012-01-01
Determining the temperature distribution of coronal plasmas can provide stringent constraints on coronal heating. Current observations with the Extreme ultraviolet Imaging Spectrograph onboard Hinode and the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory provide diagnostics of the emission measure distribution (EMD) of the coronal plasma. Here we test the reliability of temperature diagnostics using 3D radiative MHD simulations. We produce synthetic observables from the models, and apply the Monte Carlo Markov chain EMD diagnostic. By comparing the derived EMDs with the "true" distributions from the model we assess the limitations of the diagnostics, as a function of the plasma parameters and of the signal-to-noise of the data. We find that EMDs derived from EIS synthetic data reproduce some general characteristics of the true distributions, but usually show differences from the true EMDs that are much larger than the estimated uncertainties suggest, especially when structures with signif...
Unstable Disk Accretion to Magnetized Stars: First Global 3D MHD Simulations
Romanova, Marina M; Lovelace, Richard V E
2007-01-01
We report the first global three-dimensional (3D) MHD simulations of disk accretion onto a rotating magnetized star through the Rayleigh-Taylor instability. In this regime, the accreting matter typically forms 2 to 7 vertically elongated "tongues" which penetrate deep into the magnetosphere, until they are stopped by the strong field. Subsequently, the matter is channeled along the field lines to the surface of the star, forming hot spots. The number, position and shape of the hot spots vary with time, so that the light-curves associated with the hot spots are stochastic. A magnetized star may be in the stable (with funnel streams) or unstable (with random tongues) regime of accretion, and consequently have significantly different observational properties. A star may switch between these two regimes depending on the accretion rate.
Flux Emergence In The Solar Photosphere - Diagnostics Based On 3-D Rradiation-MHD Simulations
Yelles Chaouche, L.; Cheung, M.; Lagg, A.; Solanki, S.
2006-08-01
We investigate flux tube emergence in the solar photosphere using a diagnostic procedure based on analyzing Stokes signals from different spectral lines calculated in 3-D radiation-MHD simulations. The simulations include the effects of radiative transport and partial ionization and cover layers both above and below the solar surface. The simulations consider the emergence of a twisted magnetic flux tube through the solar surface. We consider different stages in the emergence process, starting from the early appearance of the flux tube at the solar surface, and following the emergence process until the emerged flux looks similar to a normal bipolar region. At every stage we compute line profiles by numerically solving the Unno-Rachkovsky equations at every horizontal grid point. Then, following observational practice, we apply Milne-Eddington-type inversions to the synthetic spectra in order to retrieve different atmospheric parameters. We include the influence of spatial smearing on the deduced atmospheric parameters to identify signatures of different stages of flux emergence in the solar photosphere.
3D MHD Simulations of Laser Plasma Guiding in Curved Magnetic Field
Roupassov, S.; Rankin, R.; Tsui, Y.; Capjack, C.; Fedosejevs, R.
1999-11-01
The guiding and confinement of laser produced plasma in a curved magnetic field has been investigated numerically. These studies were motivated by experiments on pulsed laser deposition of diamond-like films [1] in which a 1kG magnetic field in a curved solenoid geometry was utilized to steer a carbon plasma around a curved trajectory and thus to separate it from unwanted macroparticles produced by the laser ablation. The purpose of the modeling was to characterize the plasma dynamics during the propagation through the magnetic guide field and to investigate the effect of different magnetic field configurations. A 3D curvilinear ADI code developed on the basis of an existing Cartesian code [2] was employed to simulate the underlying resistive one-fluid MHD model. Issues such as large regions of low background density and nonreflective boundary conditions were addressed. Results of the simulations in a curved guide field will be presented and compared to experimental results. [1] Y.Y. Tsui, D. Vick and R. Fedosejevs, Appl. Phys. Lett. 70 (15), pp. 1953-57, 1997. [2] R. Rankin, and I. Voronkov, in "High Performance Computing Systems and Applications", pp. 59-69, Kluwer AP, 1998.
Spicule-like structures observed in 3D realistic MHD simulations
Martinez-Sykora, J; De Pontieu, B; Carlsson, M
2009-01-01
We analyze features that resemble type i spicules in two different 3D numerical simulations in which we include horizontal magnetic flux emergence in a computational domain spanning the upper layers of the convection zone to the lower corona. The two simulations differ mainly in the preexisting ambient magnetic field strength and in the properties of the inserted flux tube. We use the Oslo Staggered Code (OSC) to solve the full MHD equations with non-grey and non-LTE radiative transfer and thermal conduction along the magnetic field lines. We find a multitude of features that show a spatiotemporal evolution that is similar to that observed in type i spicules, which are characterized by parabolic height vs. time profiles, and are dominated by rapid upward motion at speeds of 10-30 km/s, followed by downward motion at similar velocities. We measured the parameters of the parabolic profile of the spicules and find similar correlations between the parameters as those found in observations. The values for height (...
A comparative study on 3-D solar wind structure observed by Ulysses and MHD simulation
Institute of Scientific and Technical Information of China (English)
FENG Xueshang; XIANG Changqing; ZHONG Dingkun; FAN Quanlin
2005-01-01
During Ulysses' first rapid pole-to-pole transit from September 1994 to June 1995, its observations showed that middle- or high-speed solar winds covered all latitudes except those between -20° and +20° near the ecliptic plane,where the velocity was 300-450 km/s. At poleward 40°,however, only fast solar winds at the speed of 700-870 km/s were observed. In addition, the transitions from low-speed wind to high-speed wind or vice versa were abrupt. In this paper, the large-scale structure of solar wind observed by Ulysses near solar minimum is simulated by using the three-dimensional numerical MHD model. The model combines TVD Lax-Friedrich scheme and MacCormack Ⅱ scheme and decomposes the calculation region into two regions: one from 1 to 22 Rs and the other from 18 Rs to 1 AU.Based on the observations of the solar photospheric magnetic field and an addition of the volumetric heating to MHD equations, the large-scale solar wind structure mentioned above is reproduced by using the three-dimensional MHD model and the numerical results are roughly consistent with Ulysses' observations. Our simulation shows that the initial magnetic field topology and the addition of volume heating may govern the bimodal structure of solar wind observed by Ulysses and also demonstrates that the three-dimensional MHD numerical model used here is efficient in modeling the large-scale solar wind structure.
3D MHD VDE and disruptions simulations of tokamaks plasmas including some ITER scenarios
Paccagnella, R.; Strauss, H. R.; Breslau, J.
2009-03-01
Tokamaks vertical displacement events (VDEs) and disruptions simulations in toroidal geometry by means of a single fluid visco-resistive magneto-hydro-dynamic (MHD) model are presented in this paper. The plasma model is completed with the presence of a 2D wall with finite resistivity which allows the study of the relatively slowly growing magnetic perturbation, the resistive wall mode (RWM), which is, in this paper, the main drive of the disruption evolution. Amplitudes and asymmetries of the halo currents pattern at the wall are also calculated and comparisons with tokamak experimental databases and predictions for ITER are given.
Energy Technology Data Exchange (ETDEWEB)
Malapaka, Shiva Kumar; Mueller, Wolf-Christian [Max-Planck Institute for Plasma Physics, Boltzmannstrasse 2, D-85748 Garching bei Muenchen (Germany)
2013-09-01
Statistical properties of the Sun's photospheric turbulent magnetic field, especially those of the active regions (ARs), have been studied using the line-of-sight data from magnetograms taken by the Solar and Heliospheric Observatory and several other instruments. This includes structure functions and their exponents, flatness curves, and correlation functions. In these works, the dependence of structure function exponents ({zeta}{sub p}) of the order of the structure functions (p) was modeled using a non-intermittent K41 model. It is now well known that the ARs are highly turbulent and are associated with strong intermittent events. In this paper, we compare some of the observations from Abramenko et al. with the log-Poisson model used for modeling intermittent MHD turbulent flows. Next, we analyze the structure function data obtained from the direct numerical simulations (DNS) of homogeneous, incompressible 3D-MHD turbulence in three cases: sustained by forcing, freely decaying, and a flow initially driven and later allowed to decay (case 3). The respective DNS replicate the properties seen in the plots of {zeta}{sub p} against p of ARs. We also reproduce the trends and changes observed in intermittency in flatness and correlation functions of ARs. It is suggested from this analysis that an AR in the onset phase of a flare can be treated as a forced 3D-MHD turbulent system in its simplest form and that the flaring stage is representative of decaying 3D-MHD turbulence. It is also inferred that significant changes in intermittency from the initial onset phase of a flare to its final peak flaring phase are related to the time taken by the system to reach the initial onset phase.
Institute of Scientific and Technical Information of China (English)
ZHANG XianGuo; PU ZuYin; MA ZhiWei; ZHOU XuZhi
2008-01-01
A three-dimensional (3-D) Hall MHD simulation is carried out to study the roles of initial current carrier in the topology of magnetic field,the generation and distribuering the contribution of ions to the initial current,the topology of the obtained magnetic field turns to be more complex. In some cases,it is found that not only the traditional By quadrupole structure but also a reversal By quadrupole structure appears in the simulation box. This can explain the observational features near the diffusion region,which are inconsistent with the Hall MHD theory with the total initial current carried by electrons. Several other interesting features are also emerged. First,motions of electrons and ions are decoupled from each other in the small plasma region (Hall effect region) with a scale less than or comparable with the ion inertial length or ion skin depth di=c/ωp. In the non-Hall effect region,the global magnetic structure is shifted in +y direction under the influence of ions with initial y directional motion. However,in the Hall effect region,magnetic field lines are bent in -y direction,mainly controlled by the motion of electrons,then By is generated. Second,FACs emerge as a result of the appearance of By. Compared with the prior Hall MHD simulation results,the generated FACs shift in +y direction,
Institute of Scientific and Technical Information of China (English)
2008-01-01
A three-dimensional (3-D) Hall MHD simulation is carried out to study the roles of initial current carrier in the topology of magnetic field, the generation and distribu- tion of field aligned currents (FACs), and the appearance of Alfvén waves. Consid- ering the contribution of ions to the initial current, the topology of the obtained magnetic field turns to be more complex. In some cases, it is found that not only the traditional By quadrupole structure but also a reversal By quadrupole structure appears in the simulation box. This can explain the observational features near the diffusion region, which are inconsistent with the Hall MHD theory with the total ini- tial current carried by electrons. Several other interesting features are also emerged. First, motions of electrons and ions are decoupled from each other in the small plasma region (Hall effect region) with a scale less than or comparable with the ion inertial length or ion skin depth di=c/ωp. In the non-Hall effect region, the global magnetic structure is shifted in +y direction under the influence of ions with initial y directional motion. However, in the Hall effect region, magnetic field lines are bent in ?y direction, mainly controlled by the motion of electrons, then By is generated. Second, FACs emerge as a result of the appearance of By. Compared with the prior Hall MHD simulation results, the generated FACs shift in +y direction, and hence the dawn-dusk symmetry is broken. Third, the Walén relation in our simulations is consistent with the Walén relation in Hall plasma, thus the presence of Alfvén wave is confirmed.
Relativistic MHD simulations of core-collapse GRB jets: 3D instabilities and magnetic dissipation
Bromberg, Omer
2015-01-01
Relativistic jets naturally occur in astrophysical systems that involve accretion onto compact objects, such as core collapse of massive stars in gamma-ray bursts (GRBs) and accretion onto supermassive black holes in active galactic nuclei (AGN). It is generally accepted that these jets are powered electromagnetically, by the magnetised rotation of a central compact object. However, how they produce the observed emission and survive the propagation for many orders of magnitude in distance without being disrupted by current-driven non-axisymmetric instabilities is the subject of active debate. We carry out time-dependent 3D relativistic magnetohydrodynamic simulations of relativistic, Poynting flux dominated jets. The jets are launched self-consistently by the rotation of a strongly magnetised central compact object. This determines the natural degree of azimuthal magnetic field winding, a crucial factor that controls jet stability. We find that the jets are susceptible to two types of instability: (i) a globa...
3D MHD Simulations of accreting neutron stars: evidence of QPO emission from the surface
Bachetti, Matteo; Kulkarni, Akshay; Burderi, Luciano; di Salvo, Tiziana; .,
2009-01-01
3D Magnetohydrodynamic simulations show that when matter accretes onto neutron stars, in particular if the misalignment angle is small, it does not constantly fall at a fixed spot. Instead, the location at which matter reaches the star moves. These moving hot spots can be produced both during stable accretion, where matter falls near the magnetic poles of the star, and unstable accretion, characterized by the presence of several tongues of matter which fall on the star near the equator, due to Rayleigh-Taylor instabilities. Precise modeling with Monte Carlo simulations shows that those movements could be observed as high frequency Quasi Periodic Oscillations. We performed a number of new simulation runs with a much wider set of parameters, focusing on neutron stars with a small misalignment angle. In most cases we observe oscillations whose frequency is correlated with the mass accretion rate $\\dot{M}$. Moreover, in some cases double QPOs appear, each of them showing the same correlation with $\\dot{M}$.
3D MHD simulation of post--flare supra--arcade downflows in a turbulent current sheet medium
Cécere, M; Costa, A; Schneiter, M
2014-01-01
Supra--arcade downflows (SADs) are sunward, generally dark, plasma density depletions originated above posteruption flare arcades. In this paper using 3D MHD simulations we investigate if the SAD cavities can be produced by a direct combination of the tearing mode and Kelvin--Helmholtz instabilities leading to a turbulent current sheet (CS) medium or if the current sheet is merely the background where SADs are produced triggered by an impulsive deposition of energy. We find that to give account of the observational dark lane structures an addition of local energy provided by a reconnection event is required. This local reconnection can trigger a nonlinear internal wave dynamic, generated by the bouncing and interfering of shocks and expansion waves that compose relatively stable voids.
Morphology and dynamics of solar prominences from 3D MHD simulations
Terradas, J; Luna, M; Oliver, R; Ballester, J L
2014-01-01
In this paper we present a numerical study of the time evolution of solar prominences embedded in sheared magnetic arcades. The prominence is represented by a density enhancement in a background stratified atmosphere and is connected to the photosphere through the magnetic field. By solving the ideal magnetohydrodynamic (MHD) equations in three dimensions we study the dynamics for a range of parameters representative of real prominences. Depending on the parameters considered, we find prominences that are suspended above the photosphere, i.e., detached prominences, but also configurations resembling curtain or hedgerow prominences whose material continuously connects to the photosphere. The plasma$-\\beta$ is an important parameter that determines the shape of the structure. In many cases magnetic Rayleigh-Taylor (MRT) instabilities and oscillatory phenomena develop. Fingers and plumes are generated, affecting the whole prominence body and producing vertical structures in an essentially horizontal magnetic fie...
3-D MHD disk wind simulations of jets and outflows from high-mass protostars
Staff, Jan E.; Tanaka, Kei; Tan, Jonathan C.; Zhang, Yichen; Liu, Mengyao
2017-01-01
We present the results of a series of nested, large scale, three-dimensional magnetohydrodynamics simulations of disk winds with a Blandford-Payne like magnetic field configuration, resolving scales from the stellar surface to beyond the core. The goal is to understand the structure of massive protostellar cores at various stages of their formation as the protostellar mass grows from a massive core. At each stage of a given protostellar mass, first, we study how jets and winds develop from the inner accretion disk to ~100 AU scales. We use the results from these simulations to dictate the inner boundary condition of a set of simulation extending to the core boundary at ~10,000 AU of an initially 60 solar mass core. We run separate simulations where the protostellar mass is 1, 2, 4, 8, 12, 16, and 24 Msun, and we are working on making a small grid of models in the context of the Turbulent Core Model with three different core masses and three different core surface densities. The wind is blown into the simulation box with properties derived from the previous jet simulations. We examine the opening angle of the outflow cavity and thus the star formation efficiency from the core due to outflow feedback. We find that the opening angle increases as the protostellar mass grows, but it is always less than 10 degrees, which is surprisingly small compared with previous analytic models. This is caused by the core which confines the outflow. Finally, we use our simulation results as input to a radiative transfer calculation, to compare with observations made by the SOMA survey.
A 3D MHD simulation of SN 1006: a polarized emission study for the turbulent case
Velázquez, P. F.; Schneiter, E. M.; Reynoso, E. M.; Esquivel, A.; De Colle, F.; Toledo-Roy, J. C.; Gómez, D. O.; Sieyra, M. V.; Moranchel-Basurto, A.
2017-01-01
Three dimensional magnetohydrodynamical simulations were carried out in order to perform a new polarization study of the radio emission of the supernova remnant SN 1006. These simulations consider that the remnant expands into a turbulent interstellar medium (including both magnetic field and figuredensity perturbations). Based on the referenced-polar angle technique, a statistical study was done on observational and numerical magnetic field position-angle distributions. Our results show that a turbulent medium with an adiabatic index of 1.3 can reproduce the polarization properties of the SN 1006 remnant. This statistical study reveals itself as a useful tool for obtaining the orientation of the ambient magnetic field, previous to be swept up by the main supernova remnant shock.
First 3D radiative transfer with scattering for domain-decomposed MHD simulations
Energy Technology Data Exchange (ETDEWEB)
Hayek, W [Research School of Astronomy and Astrophysics, Australian National University, Cotter Road, Weston Creek ACT 2611 (Australia)], E-mail: hayek@mpa-garching.mpg.de
2008-12-15
This paper presents an implementation of the Gauss-Seidel solver for radiative transfer with scattering in the Oslo Stagger Code. It fully supports MPI parallelism through domain decomposition of the simulation box, enabling fast computation of radiative transfer at a high resolution. Continuum and line opacities are treated with either a multigroup method or opacity sampling. Line scattering probabilities are estimated using the van Regemorter approximation for de-excitation rates of electron collisions. A solar-type test simulation with continuum and line scattering exhibits a steeper temperature gradient due to decreased radiative heating above the optical surface when compared with the strict local thermodynamic equilibrium (LTE) case. The classical van Regemorter approximation may overestimate the importance of line scattering, implying that the true temperature structure will be in between the LTE case and the scattering case considered here. It is demonstrated that continuum scattering is unimportant in the case of the Sun.
First 3D radiative transfer with scattering for domain-decomposed MHD simulations
Hayek, W.
2008-12-01
This paper presents an implementation of the Gauss Seidel solver for radiative transfer with scattering in the Oslo Stagger Code. It fully supports MPI parallelism through domain decomposition of the simulation box, enabling fast computation of radiative transfer at a high resolution. Continuum and line opacities are treated with either a multigroup method or opacity sampling. Line scattering probabilities are estimated using the van Regemorter approximation for de-excitation rates of electron collisions. A solar-type test simulation with continuum and line scattering exhibits a steeper temperature gradient due to decreased radiative heating above the optical surface when compared with the strict local thermodynamic equilibrium (LTE) case. The classical van Regemorter approximation may overestimate the importance of line scattering, implying that the true temperature structure will be in between the LTE case and the scattering case considered here. It is demonstrated that continuum scattering is unimportant in the case of the Sun.
3D Relativistic MHD Simulation of a Tilted Accretion Disk Around a Rapidly Rotating Black Hole
Fragile, P Chris; Blaes, Omer M; Salmonson, Jay D
2016-01-01
We posit that accreting compact objects, including stellar mass black holes and neutron stars as well as supermassive black holes, may undergo extended periods of accretion during which the angular momentum of the disk at large scales is misaligned with that of the compact object. In such a scenario, Lense-Thirring precession caused by the rotating compact object can dramatically affect the disk. In this presentation we describe results from a three-dimensional relativistic magnetohydrodynamic simulation of an MRI turbulent disk accreting onto a tilted rapidly rotating black hole. For this case, the disk does not achieve the commonly described Bardeen-Petterson configuration; rather, it remains nearly planar, undergoing a slow global precession. Accretion from the disk onto the hole occurs predominantly through two opposing plunging streams that start from high latitudes with respect to both the black-hole and disk midplanes. This is a consequence of the non-sphericity of the gravitational spacetime of the bl...
3-D nonlinear evolution of MHD instabilities
Energy Technology Data Exchange (ETDEWEB)
Bateman, G.; Hicks, H. R.; Wooten, J. W.
1977-03-01
The nonlinear evolution of ideal MHD internal instabilities is investigated in straight cylindrical geometry by means of a 3-D initial-value computer code. These instabilities are characterized by pairs of velocity vortex cells rolling off each other and helically twisted down the plasma column. The cells persist until the poloidal velocity saturates at a few tenths of the Alfven velocity. The nonlinear phase is characterized by convection around these essentially fixed vortex cells. For example, the initially centrally peaked temperature profile is convected out and around to form an annulus of high temperature surrounding a small region of lower temperature. Weak, centrally localized instabilities do not alter the edge of the plasma. Strong, large-scale instabilities, resulting from a stronger longitudinal equilibrium current, drive the plasma against the wall. After three examples of instability are analyzed in detail, the numerical methods and their verification are discussed.
D'Avillez, M A; Breitschwerdt, Dieter
2005-01-01
State of the art models of the ISM use adaptive mesh refinement to capture small scale structures, by refining on the fly those regions of the grid where density and pressure gradients occur, keeping at the same time the existing resolution in the other regions. With this technique it became possible to study the ISM in star-forming galaxies in a global way by following matter circulation between stars and the interstellar gas, and, in particular the energy input by random and clustered supernova explosions, which determine the dynamical and chemical evolution of the ISM, and hence of the galaxy as a whole. In this paper we review the conditions for a self-consistent modelling of the ISM and present the results from the latest developments in the 3D HD/MHD global models of the ISM. Special emphasis is put on the effects of the magnetic field with respect to the volume and mass fractions of the different ISM ``phases'', the relative importance of ram, thermal and magnetic pressures, and whether the field can p...
Wu, C.; Chang, T.
2010-12-01
A new method in describing the multifractal characteristics of intermittent events was introduced by Cheng and Wu [Chang T. and Wu C.C., Physical Rev, E77, 045401(R), 2008]. The procedure provides a natural connection between the rank-ordered spectrum and the idea of one-parameter scaling for monofractals. This technique has been demonstrated using results obtained from a 2D MHD simulation. It has also been successfully applied to in-situ solar wind observations [Chang T., Wu, C.C. and Podesta, J., AIP Conf Proc. 1039, 75, 2008], and the broadband electric field oscillations from the auroral zone [Tam, S.W.Y. et al., Physical Rev, E81, 036414, 2010]. We take the next step in this procedure. By using the ROMA spectra and the scaled probability distribution functions (PDFs), raw PDFs can be calculated, which can be compared directly with PDFs from observations or simulation results. In addition to 2D MHD simulation results and in-situ solar wind observation, we show clearly using the ROMA analysis the multifractal character of the 3D fluid simulation data obtained from the JHU turbulence database cluster at http://turbulence.pha.jhu.edu. In particular, we show the scaling of the non-symmetrical PDF for the parallel-velocity fluctuations of this 3D fluid data.
3D MHD Flux emergence experiments
DEFF Research Database (Denmark)
Hood, A.W.; Archontis, V.; Mactaggart, David
2012-01-01
This paper reviews some of the many 3D numerical experiments of the emergence of magnetic fields from the solar interior and the subsequent interaction with the pre-existing coronal magnetic field. The models described here are idealised, in the sense that the internal energy equation only involves...
Directory of Open Access Journals (Sweden)
E. Adamson
2012-02-01
Full Text Available We present results from mesoscale simulations of the magnetospheric cusp region for both strongly northward and strongly southward interplanetary magnetic field (IMF. Simulation results indicate an extended region of depressed magnetic field and strongly enhanced plasma β which exhibits a strong dependence on IMF orientation. These structures correspond to the Cusp Diamagnetic Cavities (CDC's. The typical features of these CDC's are generally well reproduced by the simulation. The inner boundaries between the CDC and the magnetosphere are gradual transitions which form a clear funnel shape, regardless of IMF orientation. The outer CDC/magnetosheath boundary exhibits a clear indentation in both the x-z and y-z planes for southward IMF, while it is only indented in the x-z plane for northward, with a convex geometry in the y-z plane. The outer boundary represents an Alfvénic transition, mostly consistent with a slow-shock, indicating that reconnection plays an important role in structuring the high-altitude cusp region.
3D MHD Models of Active Region Loops
Ofman, Leon
2004-01-01
Present imaging and spectroscopic observations of active region loops allow to determine many physical parameters of the coronal loops, such as the density, temperature, velocity of flows in loops, and the magnetic field. However, due to projection effects many of these parameters remain ambiguous. Three dimensional imaging in EUV by the STEREO spacecraft will help to resolve the projection ambiguities, and the observations could be used to setup 3D MHD models of active region loops to study the dynamics and stability of active regions. Here the results of 3D MHD models of active region loops are presented, and the progress towards more realistic 3D MHD models of active regions. In particular the effects of impulsive events on the excitation of active region loop oscillations, and the generation, propagations and reflection of EIT waves are shown. It is shown how 3D MHD models together with 3D EUV observations can be used as a diagnostic tool for active region loop physical parameters, and to advance the science of the sources of solar coronal activity.
Cevidanes, Lucia; Tucker, Scott; Styner, Martin; Kim, Hyungmin; Chapuis, Jonas; Reyes, Mauricio; Proffit, William; Turvey, Timothy; Jaskolka, Michael
2009-01-01
This paper discusses the development of methods for computer-aided jaw surgery. Computer-aided jaw surgery allows us to incorporate the high level of precision necessary for transferring virtual plans into the operating room. We also present a complete computer-aided surgery (CAS) system developed in close collaboration with surgeons. Surgery planning and simulation include construction of 3D surface models from Cone-beam CT (CBCT), dynamic cephalometry, semi-automatic mirroring, interactive cutting of bone and bony segment repositioning. A virtual setup can be used to manufacture positioning splints for intra-operative guidance. The system provides further intra-operative assistance with the help of a computer display showing jaw positions and 3D positioning guides updated in real-time during the surgical procedure. The CAS system aids in dealing with complex cases with benefits for the patient, with surgical practice, and for orthodontic finishing. Advanced software tools for diagnosis and treatment planning allow preparation of detailed operative plans, osteotomy repositioning, bone reconstructions, surgical resident training and assessing the difficulties of the surgical procedures prior to the surgery. CAS has the potential to make the elaboration of the surgical plan a more flexible process, increase the level of detail and accuracy of the plan, yield higher operative precision and control, and enhance documentation of cases. Supported by NIDCR DE017727, and DE018962 PMID:20816308
M3D project for simulation studies of plasmas
Energy Technology Data Exchange (ETDEWEB)
Park, W.; Belova, E.V.; Fu, G.Y. [Princeton Univ., NJ (United States). Plasma Physics Lab.; Strauss, H.R. [New York Univ., NY (United States); Sugiyama, L.E. [Massachusetts Inst. of Tech., Cambridge, MA (United States)
1998-12-31
The M3D (Multi-level 3D) project carries out simulation studies of plasmas of various regimes using multi-levels of physics, geometry, and mesh schemes in one code package. This paper and papers by Strauss, Sugiyama, and Belova in this workshop describe the project, and present examples of current applications. The currently available physics models of the M3D project are MHD, two-fluids, gyrokinetic hot particle/MHD hybrid, and gyrokinetic particle ion/two-fluid hybrid models. The code can be run with both structured and unstructured meshes.
Intermittent heating in the solar corona employing a 3D MHD model
Bingert, Sven
2011-01-01
We investigate the spatial and temporal evolution of the heating of the corona of a cool star such as our Sun in a three-dimensional magneto-hydrodynamic (3D MHD) model. We solve the 3D MHD problem numerically in a box representing part of the (solar) corona. The energy balance includes Spitzer heat conduction along the magnetic field and optically thin radiative losses. The self-consistent heating mechanism is based on the braiding of magnetic field lines rooted in the convective photosphere. Magnetic stress induced by photospheric motions leads to currents in the atmosphere which heat the corona through Ohmic dissipation. While the horizontally averaged quantities, such as heating rate, temperature or density, are relatively constant in time, the simulated corona is highly variable and dynamic, on average reaching temperatures and densities as found in observations. The strongest heating per particle is found in the transition region from the chromosphere to the corona. The heating is concentrated in curren...
Directory of Open Access Journals (Sweden)
M. Schüssler
Full Text Available Two aspects of solar MHD are discussed in relation to the work of the MHD simulation group at KIS. Photospheric magneto-convection, the nonlinear interaction of magnetic field and convection in a strongly stratified, radiating fluid, is a key process of general astrophysical relevance. Comprehensive numerical simulations including radiative transfer have significantly improved our understanding of the processes and have become an important tool for the interpretation of observational data. Examples of field intensification in the solar photosphere ('convective collapse' are shown. The second line of research is concerned with the dynamics of flux tubes in the convection zone, which has far-reaching implications for our understanding of the solar dynamo. Simulations indicate that the field strength in the region where the flux is stored before erupting to form sunspot groups is of the order of 10^{5} G, an order of magnitude larger than previous estimates based on equipartition with the kinetic energy of convective flows.
Key words. Solar physics · astrophysics and astronomy (photosphere and chromosphere; stellar interiors and dynamo theory; numerical simulation studies.
3D MHD Jet in a Non-Uniform Magnetic Field
Institute of Scientific and Technical Information of China (English)
Huang Hulin; Han Dong
2005-01-01
The purpose of this paper is to present a two-phase 3D magnetohydrodynamics (MHD) flow model that combines the volume of fluid (VOF) method with the technique derived from induced-magnetic-field equations for liquid metal free surface MHD-jet-flow. Analogy between the induced-magnetic-filed equation and the conventional computational fluid dynamics (CFD) equation is made, so that the equation can be conveniently accounted for by CFD. A penalty factor numerical method is introduced in order to force the local divergence-free condition of the magnetic fields and an extension of the void insulating calculation domain is applied to ensure that the induced-magnetic field at its boundaries is null. These simulation results for lithium liquid metal jets under magnetic field configurations of Magnetic Torus (Mtor) and National Spherical Torus Experiment (NSTX) outboard divertor have shown that three dimensional jet can not be annihilated by magnetic braking and its cross-section will deform in such a way that the momentum flux of the jet is conserved. 3D MHD effects from a magnetic field gradient cause return currents to interact with applied magnetic fields and produce unfavorable Lorentz forces.Under 3D applied non-uniform magnetic fields of the divertor, unfavorable Lorentz forces lead to a substantial change in flow pattern and a reduction in flow velocity, with the jet cross-section moving to one side of the jet space. These critical phenomena can not be revealed by 2D models.
FARGO3D: A new GPU-oriented MHD code
Benítez-Llambay, Pablo
2016-01-01
We present the FARGO3D code, recently publicly released. It is a magnetohydrodynamics code developed with special emphasis on protoplanetary disks physics and planet-disk interactions, and parallelized with MPI. The hydrodynamics algorithms are based on finite difference upwind, dimensionally split methods. The magnetohydrodynamics algorithms consist of the constrained transport method to preserve the divergence-free property of the magnetic field to machine accuracy, coupled to a method of characteristics for the evaluation of electromotive forces and Lorentz forces. Orbital advection is implemented, and an N-body solver is included to simulate planets or stars interacting with the gas. We present our implementation in detail and present a number of widely known tests for comparison purposes. One strength of FARGO3D is that it can run on both "Graphical Processing Units" (GPUs) or "Central Processing unit" (CPUs), achieving large speed up with respect to CPU cores. We describe our implementation choices, whi...
Sawtooth mitigation in 3D MHD tokamak modelling with applied magnetic perturbations
Bonfiglio, D.; Veranda, M.; Cappello, S.; Chacón, L.; Escande, D. F.
2017-01-01
The effect of magnetic perturbations (MPs) on the sawtoothing dynamics of the internal kink mode in the tokamak is discussed in the framework of nonlinear 3D MHD modelling. Numerical simulations are performed with the pixie3d code (Chacón 2008 Phys. Plasmas 15 056103) based on a D-shaped configuration in toroidal geometry. MPs are applied as produced by two sets of coils distributed along the toroidal direction, one set located above and the other set below the outboard midplane, like in experimental devices such as DIII-D and ASDEX Upgrade. The capability of n = 1 MPs to affect quasi-periodic sawteeth is shown to depend on the toroidal phase difference Δ φ between the perturbations produced by the two sets of coils. In particular, sawtooth mitigation is obtained for the Δ φ =π phasing, whereas no significant effect is observed for Δ φ =0 . Numerical findings are explained by the interplay between different poloidal harmonics in the spectrum of applied MPs, and appear to be consistent with experiments performed in the DIII-D device. Sawtooth mitigation and stimulation of self-organized helical states by applied MPs have been previously demonstrated in both circular tokamak and reversed-field pinch (RFP) experiments in the RFX-mod device, and in related 3D MHD modelling.
FARGO3D: A NEW GPU-ORIENTED MHD CODE
Energy Technology Data Exchange (ETDEWEB)
Benitez-Llambay, Pablo [Instituto de Astronomía Teórica y Experimental, Observatorio Astronónomico, Universidad Nacional de Córdoba. Laprida 854, X5000BGR, Córdoba (Argentina); Masset, Frédéric S., E-mail: pbllambay@oac.unc.edu.ar, E-mail: masset@icf.unam.mx [Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México (UNAM), Apdo. Postal 48-3,62251-Cuernavaca, Morelos (Mexico)
2016-03-15
We present the FARGO3D code, recently publicly released. It is a magnetohydrodynamics code developed with special emphasis on the physics of protoplanetary disks and planet–disk interactions, and parallelized with MPI. The hydrodynamics algorithms are based on finite-difference upwind, dimensionally split methods. The magnetohydrodynamics algorithms consist of the constrained transport method to preserve the divergence-free property of the magnetic field to machine accuracy, coupled to a method of characteristics for the evaluation of electromotive forces and Lorentz forces. Orbital advection is implemented, and an N-body solver is included to simulate planets or stars interacting with the gas. We present our implementation in detail and present a number of widely known tests for comparison purposes. One strength of FARGO3D is that it can run on either graphical processing units (GPUs) or central processing units (CPUs), achieving large speed-up with respect to CPU cores. We describe our implementation choices, which allow a user with no prior knowledge of GPU programming to develop new routines for CPUs, and have them translated automatically for GPUs.
Large-scale Magnetic Structure Formation in 3D-MHD Turbulence
Malapaka, Shiva Kumar
2013-01-01
The inverse cascade of magnetic helicity in 3D-MHD turbulence is believed to be one of the processes responsible for large scale magnetic structure formation in astrophysical systems. In this work we present an exhaustive set of high resolution direct numerical simulations (DNS) of both forced and decaying 3D-MHD turbulence, to understand this structure formation process. It is first shown that an inverse cascade of magnetic helicity in small-scale driven turbulence does not necessarily generate coherent large-scale magnetic structures. The observed large-scale magnetic field, in this case, is severely perturbed by magnetic fluctuations generated by the small-scale forcing. In the decaying case, coherent large-scale structure form similar to those observed astronomically. Based on the numerical results the formation of large-scale magnetic structures in some astrophysical systems, is suggested to be the consequence of an initial forcing which imparts the necessary turbulent energy into the system, which, afte...
Observationally driven 3D MHD model of the solar corona above an active region
Bourdin, Ph -A; Peter, H
2013-01-01
Aims. The goal is to employ a 3D magnetohydrodynamics (MHD) model including spectral synthesis to model the corona in an observed solar active region. This will allow us to judge the merits of the coronal heating mechanism built into the 3D model. Methods. Photospheric observations of the magnetic field and horizontal velocities in an active region are used to drive our coronal simulation from the bottom. The currents induced by this heat the corona through Ohmic dissipation. Heat conduction redistributes the energy that is lost in the end through optically thin radiation. Based on the MHD model, we synthesized profiles of coronal emission lines which can be directly compared to actual coronal observations of the very same active region. Results. In the synthesized model data we find hot coronal loops which host siphon flows or which expand and lose mass through draining. These synthesized loops are at the same location as and show similar dynamics in terms of Doppler shifts to the observed structures. This m...
Non-local thermodynamic equilibrium inversions from a 3D MHD chromospheric model
Rodríguez, Jaime de la Cruz; Carlsson, Mats; Leenaarts, Jorrit
2012-01-01
The structure of the solar chromosphere is believed to be governed by magnetic fields, even in quiet-Sun regions that have a relatively weak photospheric field. During the past decade inversion methods have emerged as powerful tools for analyzing the chromosphere of active regions. The applicability of inversions to infer the stratification of the physical conditions in a dynamic 3D solar chromosphere has not yet been studied in detail. This study aims to establish the diagnostic capabilities of non-local thermodynamical equilibrium (NLTE) inversion techniques of Stokes profiles induced by the Zeeman effect in the Ca II 8542 line. We computed the Ca II atomic level populations in a snapshot from a 3D radiation-MHD simulation of the quiet solar atmosphere in non-LTE using the 3D radiative transfer code Multi3d. These populations were used to compute synthetic full-Stokes profiles in the Ca II 8542 line using 1.5D radiative transfer and the inversion code Nicole. The profiles were then spectrally degraded to ac...
Hayek, W.; Asplund, M.; Carlsson, M.; Trampedach, R.; Collet, R.; Gudiksen, B. V.; Hansteen, V. H.; Leenaarts, J.
2010-07-01
Aims: We present the implementation of a radiative transfer solver with coherent scattering in the new BIFROST code for radiative magneto-hydrodynamical (MHD) simulations of stellar surface convection. The code is fully parallelized using MPI domain decomposition, which allows for large grid sizes and improved resolution of hydrodynamical structures. We apply the code to simulate the surface granulation in a solar-type star, ignoring magnetic fields, and investigate the importance of coherent scattering for the atmospheric structure. Methods: A scattering term is added to the radiative transfer equation, requiring an iterative computation of the radiation field. We use a short-characteristics-based Gauss-Seidel acceleration scheme to compute radiative flux divergences for the energy equation. The effects of coherent scattering are tested by comparing the temperature stratification of three 3D time-dependent hydrodynamical atmosphere models of a solar-type star: without scattering, with continuum scattering only, and with both continuum and line scattering. Results: We show that continuum scattering does not have a significant impact on the photospheric temperature structure for a star like the Sun. Including scattering in line-blanketing, however, leads to a decrease of temperatures by about 350 K below log10 τ5000 ⪉ -4. The effect is opposite to that of 1D hydrostatic models in radiative equilibrium, where scattering reduces the cooling effect of strong LTE lines in the higher layers of the photosphere. Coherent line scattering also changes the temperature distribution in the high atmosphere, where we observe stronger fluctuations compared to a treatment of lines as true absorbers.
A global 3-D MHD model of the solar wind with Alfven waves
Usmanov, A. V.
1995-01-01
A fully three-dimensional solar wind model that incorporates momentum and heat addition from Alfven waves is developed. The proposed model upgrades the previous one by considering self-consistently the total system consisting of Alfven waves propagating outward from the Sun and the mean polytropic solar wind flow. The simulation region extends from the coronal base (1 R(sub s) out to beyond 1 AU. The fully 3-D MHD equations written in spherical coordinates are solved in the frame of reference corotating with the Sun. At the inner boundary, the photospheric magnetic field observations are taken as boundary condition and wave energy influx is prescribed to be proportional to the magnetic field strength. The results of the model application for several time intervals are presented.
MHD simulations on an unstructured mesh
Energy Technology Data Exchange (ETDEWEB)
Strauss, H.R. [New York Univ., NY (United States); Park, W.; Belova, E.; Fu, G.Y. [Princeton Univ., NJ (United States). Plasma Physics Lab.; Longcope, D.W. [Univ. of Montana, Missoula, MT (United States); Sugiyama, L.E. [Massachusetts Inst. of Tech., Cambridge, MA (United States)
1998-12-31
Two reasons for using an unstructured computational mesh are adaptivity, and alignment with arbitrarily shaped boundaries. Two codes which use finite element discretization on an unstructured mesh are described. FEM3D solves 2D and 3D RMHD using an adaptive grid. MH3D++, which incorporates methods of FEM3D into the MH3D generalized MHD code, can be used with shaped boundaries, which might be 3D.
3D MHD modeling of twisted coronal loops
Reale, F; Guarrasi, M; Mignone, A; Peres, G; Hood, A W; Priest, E R
2016-01-01
We perform MHD modeling of a single bright coronal loop to include the interaction with a non-uniform magnetic field. The field is stressed by random footpoint rotation in the central region and its energy is dissipated into heating by growing currents through anomalous magnetic diffusivity that switches on in the corona above a current density threshold. We model an entire single magnetic flux tube, in the solar atmosphere extending from the high-beta chromosphere to the low-beta corona through the steep transition region. The magnetic field expands from the chromosphere to the corona. The maximum resolution is ~30 km. We obtain an overall evolution typical of loop models and realistic loop emission in the EUV and X-ray bands. The plasma confined in the flux tube is heated to active region temperatures (~3 MK) after ~2/3 hr. Upflows from the chromosphere up to ~100 km/s fill the core of the flux tube to densities above 10^9 cm^-3. More heating is released in the low corona than the high corona and is finely ...
3D MHD modeling of twisted coronal loops
Reale, F.; Orlando, S.; Guarrasi, M.; Mignone, A.; Peres, G.; Hood, A. W.; Priest, E. R.
2016-10-01
We perform MHD modeling of a single bright coronal loop to include the interaction with a non-uniform magnetic field. The field is stressed by random footpoint rotation in the central region and its energy is dissipated into heating by growing currents through anomalous magnetic diffusivity that switches on in the corona above a current density threshold. We model an entire single magnetic flux tube in the solar atmosphere extending from the high-β chromosphere to the low-β corona through the steep transition region. The magnetic field expands from the chromosphere to the corona. The maximum resolution is ∼30 km. We obtain an overall evolution typical of loop models and realistic loop emission in the EUV and X-ray bands. The plasma confined in the flux tube is heated to active region temperatures (∼3 MK) after ∼2/3 hr. Upflows from the chromosphere up to ∼100 km s‑1 fill the core of the flux tube to densities above 109 cm‑3. More heating is released in the low corona than the high corona and is finely structured both in space and time.
A novel code for numerical 3-D MHD studies of CME expansion
Directory of Open Access Journals (Sweden)
J. Kleimann
2009-03-01
Full Text Available A recent third-order, essentially non-oscillatory central scheme to advance the equations of single-fluid magnetohydrodynamics (MHD in time has been implemented into a new numerical code. This code operates on a 3-D Cartesian, non-staggered grid, and is able to handle shock-like gradients without producing spurious oscillations.
To demonstrate the suitability of our code for the simulation of coronal mass ejections (CMEs and similar heliospheric transients, we present selected results from test cases and perform studies of the solar wind expansion during phases of minimum solar activity. We can demonstrate convergence of the system into a stable Parker-like steady state for both hydrodynamic and MHD winds. The model is subsequently applied to expansion studies of CME-like plasma bubbles, and their evolution is monitored until a stationary state similar to the initial one is achieved. In spite of the model's (current simplicity, we can confirm the CME's nearly self-similar evolution close to the Sun, thus highlighting the importance of detailed modelling especially at small heliospheric radii.
Additionally, alternative methods to implement boundary conditions at the coronal base, as well as strategies to ensure a solenoidal magnetic field, are discussed and evaluated.
Modeling Statistical Properties of Solar Active Regions through DNS of 3D-MHD Turbulence
Malapaka, Shiva Kumar
2013-01-01
Statistical properties of the Sun's photospheric turbulent magnetic field, especially those of the Active Regions (ARs), have been studied using the line-of-sight data from magnetograms taken by SOHO and several other instruments (see e.g. Abramenko et al (2002, 2003),Abramenko and Yurchyshyn (2010)). This includes structure functions and their exponents, flatness curves and correlation functions. In these works, the dependence of structure function exponents ($\\zeta_p$) of the order of the structure functions ($\\it{p}$) was modeled using a non-intermittent K41 model. It is now well known that the ARs are highly turbulent and are associated with strong intermittent events. In this paper we compare some of the observations from Abramenko et al (2003) with the log-Poisson model (Biskamp 2003) used for modeling intermittent MHD turbulent flows. Next, we analyze the structure function data obtained from the direct numerical simulations (DNS) of homogeneous, incompressible 3D-MHD turbulence in three cases: sustain...
Scaling laws of coronal loops compared to a 3D MHD model of an Active Region
Bourdin, Philippe-A; Peter, Hardi
2016-01-01
Context. The structure and heating of coronal loops are investigated since decades. Established scaling laws relate fundamental quantities like the loop apex temperature, pressure, length, and the coronal heating. Aims. We test such scaling laws against a large-scale 3D MHD model of the Solar corona, which became feasible with nowadays high-performance computing. Methods. We drive an active region simulation a with photospheric observations and found strong similarities to the observed coronal loops in X-rays and EUV wavelength. A 3D reconstruction of stereoscopic observations showed that our model loops have a realistic spatial structure. We compare scaling laws to our model data extracted along an ensemble of field lines. Finally, we fit a new scaling law that represents well hot loops and also cooler structures, which was not possible before only based on observations. Results. Our model data gives some support for scaling laws that were established for hot and EUV-emissive coronal loops. For the RTV scali...
Toward 3D MHD modeling of neoclassical tearing mode suppression by ECCD
Directory of Open Access Journals (Sweden)
Westerhof E.
2012-09-01
Full Text Available We propose a framework to extend the magnetohydrodynamic (MHD equations to include electron cyclotron current drive (ECCD and discuss previous models proposed by Giruzzi et al. [2] and by Hegna and Callen [3]. To model neoclassical tearing mode (NTM instabilities and study the growth of magnetic islands as NTMs evolve, we employ the nonlinear reduced-MHD simulation JOREK. We present tearing-mode growth-rate calculations from JOREK simulations.
Coronal energy input and dissipation in a solar active region 3D MHD model
Bourdin, Philippe-A; Peter, Hardi
2015-01-01
Context. We have conducted a 3D MHD simulation of the solar corona above an active region in full scale and high resolution, which shows coronal loops, and plasma flows within them, similar to observations. Aims. We want to find the connection between the photospheric energy input by field-line braiding with the coronal energy conversion by Ohmic dissipation of induced currents. Methods. To this end we compare the coronal energy input and dissipation within our simulation domain above different fields of view, e.g. for a small loops system in the active region (AR) core. We also choose an ensemble of field lines to compare, e.g., the magnetic energy input to the heating per particle along these field lines. Results. We find an enhanced Ohmic dissipation of currents in the corona above areas that also have enhanced upwards-directed Poynting flux. These regions coincide with the regions where hot coronal loops within the AR core are observed. The coronal density plays a role in estimating the coronal temperatur...
Expected IPS variations due to a disturbance described by a 3-D MHD model
Tappin, S. J.; Dryer, M.; Han, S. M.; Wu, S. T.
1988-01-01
The variations of interplanetary scintillation due to a disturbance described by a three-dimensional, time-dependent, MHD model of the interplanetary medium are calculated. The resulting simulated IPS maps are compared with observations of real disturbances and it is found that there is some qualitative agreement. It is concluded that the MHD model with a more realistic choice of input conditions would probably provide a useful description of many interplanetary disturbances.
Progress on accelerated calculation of 3D MHD equilibrium with the PIES code
Raburn, Daniel; Reiman, Allan; Monticello, Donald
2016-10-01
Continuing progress has been made in accelerating the 3D MHD equilibrium code, PIES, using an external numerical wrapper. The PIES code (Princeton Iterative Equilibrium Solver) is capable of calculating 3D MHD equilibria with islands. The numerical wrapper has been demonstrated to greatly improve the rate of convergence in numerous cases corresponding to equilibria in the TFTR device where magnetic islands are present; the numerical wrapper makes use of a Jacobian-free Newton-Krylov solver along with adaptive preconditioning and a sophisticated subspace-restricted Levenberg backtracking algorithm. The wrapper has recently been improved by automation which combines the preexisting backtracking algorithm with insights gained from the stability of the Picard algorithm traditionally used with PIES. Improved progress logging and stopping criteria have also been incorporated in to the numerical wrapper.
A blowup criterion for the 3D generalized MHD system with zero magnetic diffusivity
Directory of Open Access Journals (Sweden)
Jishan Fan
2014-10-01
Full Text Available This paper proves a new regularity criterion ω: = rotu∈L¹(0，T;Bº ∞，∞ for the 3D generalized MHD system with fractional diffusion terms ( － Δαu with α ＞ 8/9 and zero magnetic diffusivity． Here u is the fluid velocity，ω is the vorticity and Bº∞，∞ is the homogeneous Besov space．
Buttery, Richard
2011-08-01
This annual workshop on MHD Stability Control has been held since 1996 with a focus on understanding and developing control of MHD instabilities for future fusion reactors. The workshop generally covers a wide range of stability topics: from disruptions, to tearing modes, error fields, ELMs, resistive wall modes (RWMs) and ideal MHD. It spans many device types, particularly tokamaks, stellarators and reversed field pinches, to pull out commonalities in the physics and improve understanding. In 2010 the workshop was held on 15-17 November at the University of Wisconsin in Madison and was combined with the annual US-Japan MHD Workshop. The theme was `3D Magnetic Field Effects in MHD Control', with a focus on multidisciplinary sessions exploring issues of plasma response to 3D fields, the manifestation of such fields in the plasma, and how they influence stability. This has been a topic of renewed interest, with utilisation of 3D fields for ELM control now planned in ITER, and a focus on the application of such fields for error field correction, disruption avoidance, and RWM control. Key issues included the physics of the interaction, types of coils and harmonic spectra needed to control instabilities, and subsidiary effects such as braking (or rotating) the plasma. More generally, a wider range of issues were discussed including RWM physics, tearing mode physics, disruption mitigation, ballooning stability, the snowflake divertor concept, and the line tied pinch! A novel innovation to the meeting was a panel discussion session, this year on Neoclassical Toroidal Viscosity, which ran well; more will be tried next year. In this special section of Plasma Physics and Controlled Fusion we present several of the invited and contributed papers from the 2010 workshop, which have been subject to the normal refereeing procedures of the journal. These papers give a sense of the exceptional quality of the presentations at this workshop, all of which may be found at http://fusion.gat.com/conferences/mhd
On the 2D behavior of 3D MHD with a strong guiding field
Alexakis, Alexandros
2011-01-01
The Magneto-hydrodynamic (MHD) equations in the presence of a guiding magnetic field are investigated by means of direct numerical simulations. The basis of the investigation consists of 9 runs forced at the small scales. The results demonstrate that for a large enough uniform magnetic field the large scale flow behaves as a two dimensional (non-MHD) fluid exhibiting an inverse cascade of energy in the direction perpendicular to the magnetic field, while the small scales behave like a three dimensional MHD-fluid cascading the energy forwards. The amplitude of the inverse cascade is sensitive to the magnetic field amplitude, the domain size, the forcing mechanism, and the forcing scale. All these dependencies are demonstrated by the varying parameters of simulations. Furthermore, in the case that the system is forced anisotropically in the small parallel scales an inverse cascade in the parallel direction is observed that is feeding the 2D modes.
INCORPORATING DYNAMIC 3D SIMULATION INTO PRA
Energy Technology Data Exchange (ETDEWEB)
Steven R Prescott; Curtis Smith
2011-07-01
Through continued advancement in computational resources, development that was previously done by trial and error production is now performed through computer simulation. These virtual physical representations have the potential to provide accurate and valid modeling results and are being used in many different technical fields. Risk assessment now has the opportunity to use 3D simulation to improve analysis results and insights, especially for external event analysis. By using simulations, the modeler only has to determine the likelihood of an event without having to also predict the results of that event. The 3D simulation automatically determines not only the outcome of the event, but when those failures occur. How can we effectively incorporate 3D simulation into traditional PRA? Most PRA plant modeling is made up of components with different failure modes, probabilities, and rates. Typically, these components are grouped into various systems and then are modeled together (in different combinations) as a “system” with logic structures to form fault trees. Applicable fault trees are combined through scenarios, typically represented by event tree models. Though this method gives us failure results for a given model, it has limitations when it comes to time-based dependencies or dependencies that are coupled to physical processes which may themselves be space- or time-dependent. Since, failures from a 3D simulation are naturally time related, they should be used in that manner. In our simulation approach, traditional static models are converted into an equivalent state diagram representation with start states, probabilistic driven movements between states and terminal states. As the state model is run repeatedly, it converges to the same results as the PRA model in cases where time-related factors are not important. In cases where timing considerations are important (e.g., when events are dependent upon each other), then the simulation approach will typically
Simulation of 3D diamond detectors
Forcolin, G. T.; Oh, A.; Murphy, S. A.
2017-02-01
3D diamond detectors present an interesting prospect for future Particle Physics experiments. They have been studied in detail at beam tests with 120 GeV protons and 4 MeV protons. To understand the observations that have been made, simulations have been carried out using Synopsys TCAD in order to explain the movement of charge carriers within the sample, as well as the effects of charge sharing. Reasonable agreement has been observed between simulation and experiment.
Numerical Simulation of 3-D Wave Crests
Institute of Scientific and Technical Information of China (English)
YU Dingyong; ZHANG Hanyuan
2003-01-01
A clear definition of 3-D wave crest and a description of the procedures to detect the boundary of wave crest are presented in the paper. By using random wave theory and directional wave spectrum, a MATLAB-platformed program is designed to simulate random wave crests for various directional spectral conditions in deep water. Statistics of wave crests with different directional spreading parameters and different directional functions are obtained and discussed.
Existence of two MHD reconnection modes in a solar 3D magnetic null point topology
Pariat, Etienne; Antiochos, Spiro; DeVore, C. Richard; Dalmasse, Kévin
2012-07-01
Magnetic topologies with a 3D magnetic null point are common in the solar atmosphere and occur at different spatial scales: such structures can be associated with some solar eruptions, with the so-called pseudo-streamers, and with numerous coronal jets. We have recently developed a series of numerical experiments that model magnetic reconnection in such configurations in order to study and explain the properties of jet-like features. Our model uses our state-of-the-art adaptive-mesh MHD solver ARMS. Energy is injected in the system by line-tied motion of the magnetic field lines in a corona-like configuration. We observe that, in the MHD framework, two reconnection modes eventually appear in the course of the evolution of the system. A very impulsive one, associated with a highly dynamic and fully 3D current sheet, is associated with the energetic generation of a jet. Before and after the generation of the jet, a quasi-steady reconnection mode, more similar to the standard 2D Sweet-Parker model, presents a lower global reconnection rate. We show that the geometry of the magnetic configuration influences the trigger of one or the other mode. We argue that this result carries important implications for the observed link between observational features such as solar jets, solar plumes, and the emission of coronal bright points.
A Novel High-Order, Entropy Stable, 3D AMR MHD Solver with Guaranteed Positive Pressure
Derigs, Dominik; Gassner, Gregor J; Walch, Stefanie
2016-01-01
We describe a high-order numerical magnetohydrodynamics (MHD) solver built upon a novel non-linear entropy stable numerical flux function that supports eight travelling wave solutions. By construction the solver conserves mass, momentum, and energy and is entropy stable. The method is designed to treat the divergence-free constraint on the magnetic field in a similar fashion to a hyperbolic divergence cleaning technique. The solver described herein is especially well-suited for flows involving strong discontinuities. Furthermore, we present a new formulation to guarantee positivity of the pressure. We present the underlying theory and implementation of the new solver into the multi-physics, multi-scale adaptive mesh refinement (AMR) simulation code $\\texttt{FLASH}$ (http://flash.uchicago.edu). The accuracy, robustness and computational efficiency is demonstrated with a number of tests, including comparisons to available MHD implementations in $\\texttt{FLASH}$.
Resistive MHD jet simulations with large resistivity
Cemeljic, Miljenko; Vlahakis, Nektarios; Tsinganos, Kanaris
2009-01-01
Axisymmetric resistive MHD simulations for radially self-similar initial conditions are performed, using the NIRVANA code. The magnetic diffusivity could occur in outflows above an accretion disk, being transferred from the underlying disk into the disk corona by MHD turbulence (anomalous turbulent diffusivity), or as a result of ambipolar diffusion in partially ionized flows. We introduce, in addition to the classical magnetic Reynolds number Rm, which measures the importance of resistive effects in the induction equation, a new number Rb, which measures the importance of the resistive effects in the energy equation. We find two distinct regimes of solutions in our simulations. One is the low-resistivity regime, in which results do not differ much from ideal-MHD solutions. In the high-resistivity regime, results seem to show some periodicity in time-evolution, and depart significantly from the ideal-MHD case. Whether this departure is caused by numerical or physical reasons is of considerable interest for nu...
Quasi 3D ECE imaging system for study of MHD instabilities in KSTAR
Energy Technology Data Exchange (ETDEWEB)
Yun, G. S., E-mail: gunsu@postech.ac.kr; Choi, M. J.; Lee, J.; Kim, M.; Leem, J.; Nam, Y.; Choe, G. H. [Department of Physics, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Lee, W.; Park, H. K. [Ulsan National Institute of Science and Technology, Ulsan 689-798 (Korea, Republic of); Park, H.; Woo, D. S.; Kim, K. W. [School of Electrical Engineering, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Domier, C. W.; Luhmann, N. C. [Department of Electrical and Computer Engineering, University of California, Davis, California 95616 (United States); Ito, N. [KASTEC, Kyushu University, Kasuga-shi, Fukuoka 812-8581 (Japan); Mase, A. [Ube National College of Technology, Ube-shi, Yamaguchi 755-8555 (Japan); Lee, S. G. [National Fusion Research Institute, Daejeon 305-333 (Korea, Republic of)
2014-11-15
A second electron cyclotron emission imaging (ECEI) system has been installed on the KSTAR tokamak, toroidally separated by 1/16th of the torus from the first ECEI system. For the first time, the dynamical evolutions of MHD instabilities from the plasma core to the edge have been visualized in quasi-3D for a wide range of the KSTAR operation (B{sub 0} = 1.7∼3.5 T). This flexible diagnostic capability has been realized by substantial improvements in large-aperture quasi-optical microwave components including the development of broad-band polarization rotators for imaging of the fundamental ordinary ECE as well as the usual 2nd harmonic extraordinary ECE.
Radiative Transfer in 3D Numerical Simulations
Stein, R; Stein, Robert; Nordlund, Aake
2002-01-01
We simulate convection near the solar surface, where the continuum optical depth is of order unity. Hence, to determine the radiative heating and cooling in the energy conservation equation, we must solve the radiative transfer equation (instead of using the diffusion or optically thin cooling approximations). A method efficient enough to calculate the radiation for thousands of time steps is needed. We assume LTE and a non-gray opacity grouped into 4 bins according to strength. We perform a formal solution of the Feautrier equation along a vertical and four straight, slanted, rays (at four azimuthal angles which are rotated 15 deg. every time step). We present details of our method. We also give some results: comparing simulated and observed line profiles for the Sun, showing the importance of 3D transfer for the structure of the mean atmosphere and the eigenfrequencies of p-modes, illustrating Stokes profiles for micropores, and analyzing the effect of radiation on p-mode asymmetries.
The 3D MHD code GOEMHD3 for large-Reynolds-number astrophysical plasmas
Skála, J; Büchner, J; Rampp, M
2014-01-01
The numerical simulation of turbulence and flows in almost ideal, large-Reynolds-number astrophysical plasmas motivates the implementation of almost conservative MHD computer codes. They should efficiently calculate, use highly parallelized schemes scaling well with large numbers of CPU cores, allows to obtain a high grid resolution over large simulation domains and which can easily be adapted to new computer architectures as well as to new initial and boundary conditions, allow modular extensions. The new massively parallel simulation code GOEMHD3 enables efficient and fast simulations of almost ideal, large-Reynolds-number astrophysical plasma flows, well resolved and on huge grids covering large domains. Its abilities are validated by major tests of ideal and weakly dissipative plasma phenomena. The high resolution ($2048^3$ grid points) simulation of a large part of the solar corona above an observed active region proved the excellent parallel scalability of the code using more than 30.000 processor cores...
3D MHD Coronal Oscillations About a Magnetic Null Point: Application of WKB Theory
McLaughlin, J A; Hood, A W
2007-01-01
This paper is a demonstration of how the WKB approximation can be used to help solve the linearised 3D MHD equations. Using Charpit's Method and a Runge-Kutta numerical scheme, we have demonstrated this technique for a potential 3D magnetic null point, ${\\bf{B}}=(x,\\epsilon y -(\\epsilon +1)z)$. Under our cold plasma assumption, we have considered two types of wave propagation: fast magnetoacoustic and Alfv\\'en waves. We find that the fast magnetoacoustic wave experiences refraction towards the magnetic null point, and that the effect of this refraction depends upon the Alfv\\'en speed profile. The wave, and thus the wave energy, accumulates at the null point. We have found that current build up is exponential and the exponent is dependent upon $\\epsilon$. Thus, for the fast wave there is preferential heating at the null point. For the Alfv\\'en wave, we find that the wave propagates along the fieldlines. For an Alfv\\'en wave generated along the fan-plane, the wave accumulates along the spine. For an Alfv\\'en wa...
Non-isothermal 3D SDPD Simulations
Yang, Jun; Potami, Raffaele; Gatsonis, Nikolaos
2012-11-01
The study of fluids at micro and nanoscale requires new modeling and computational approaches. Smooth Particle Dissipative Dynamics (SDPD) is a mesh-free method that provides a bridge between the continuum equations of hydrodynamics embedded in the Smooth Particle Hydrodynamics approach and the molecular nature embedded in the DPD approach. SDPD is thermodynamically consistent, does not rely on arbitrary coefficients for its thermostat, involves realistic transport coefficients, and includes fluctuation terms. SDPD is implemented in our work for arbitrary 3D geometries with a methodology to model solid wall boundary conditions. We present simulations for isothermal flows for verification of our approach. The entropy equation is implemented with a velocity-entropy Verlet integration algorithm Flows with heat transfer are simulated for verification of the SDPD. We present also the self-diffusion coefficient derived from SDPD simulations for gases and liquids. Results show the scale dependence of self-diffusion coefficient on SDPD particle size. Computational Mathematics Program of the Air Force Office of Scientific Research under grant/contract number FA9550-06-1-0236.
Spicules and Jets: 3D flux emergence simulations
Martínez-Sykora, Juan; Moreno-Insertis, Fernando
2010-01-01
Recent high temporal and spatial resolution observations of the chromosphere have forced the definition of a new type of spicule, ``type II's", that are characterized by rising rapidly, having short lives, and by fading away at the end of their lifetimes. Here, we report on features found in realistic 3D simulations of the outer solar atmosphere that resemble the observed type II spicules. These features evolve naturally from the simulations as a consequence of the magnetohydrodynamical evolution of the model atmosphere. The simulations span from the upper layer of the convection zone to the lower corona and include the emergence of horizontal magnetic flux. The state-of-art Oslo Staggered Code (OSC) is used to solve the full MHD equations with non-grey and non-LTE radiative transfer and thermal conduction along the magnetic field lines. We describe in detail the physics involved in a process which we consider a possible candidate as a driver mechanism to produce type II spicules. The model spicule is compose...
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.
A remark on the Beale-Kato-Majda criterion for the 3D MHD equations with zero magnetic diffusivity
Gala, Sadek; Ragusa, Maria Alessandra
2016-06-01
In this work, we show that a smooth solution of the 3D MHD equations with zero magnetic diffusivity in the whole space ℝ3 breaks down if and only if a certain norm of the magnetic field blows up at the same time.
FOI-PERFECT code: 3D relaxation MHD modeling and Applications
Wang, Gang-Hua; Duan, Shu-Chao; Comutational Physics Team Team
2016-10-01
One of the challenges in numerical simulations of electromagnetically driven high energy density (HED) systems is the existence of vacuum region. FOI-PERFECT code adopts a full relaxation magnetohydrodynamic (MHD) model. The electromagnetic part of the conventional model adopts the magnetic diffusion approximation. The vacuum region is approximated by artificially increasing the resistivity. On one hand the phase/group velocity is superluminal and hence non-physical in the vacuum region, on the other hand a diffusion equation with large diffusion coefficient can only be solved by implicit scheme which is difficult to be parallelized and converge. A better alternative is to solve the full electromagnetic equations. Maxwell's equations coupled with the constitutive equation, generalized Ohm's law, constitute a relaxation model. The dispersion relation is given to show its transition from electromagnetic propagation in vacuum to resistive MHD in plasma in a natural way. The phase and group velocities are finite for this system. A better time stepping is adopted to give a 3rd full order convergence in time domain without the stiff relaxation term restriction. Therefore it is convenient for explicit & parallel computations. Some numerical results of FOI-PERFECT code are also given. Project supported by the National Natural Science Foundation of China (Grant No. 11571293) And Foundation of China Academy of Engineering Physics (Grant No. 2015B0201023).
Skála, J.; Baruffa, F.; Büchner, J.; Rampp, M.
2015-08-01
Context. The numerical simulation of turbulence and flows in almost ideal astrophysical plasmas with large Reynolds numbers motivates the implementation of magnetohydrodynamical (MHD) computer codes with low resistivity. They need to be computationally efficient and scale well with large numbers of CPU cores, allow obtaining a high grid resolution over large simulation domains, and be easily and modularly extensible, for instance, to new initial and boundary conditions. Aims: Our aims are the implementation, optimization, and verification of a computationally efficient, highly scalable, and easily extensible low-dissipative MHD simulation code for the numerical investigation of the dynamics of astrophysical plasmas with large Reynolds numbers in three dimensions (3D). Methods: The new GOEMHD3 code discretizes the ideal part of the MHD equations using a fast and efficient leap-frog scheme that is second-order accurate in space and time and whose initial and boundary conditions can easily be modified. For the investigation of diffusive and dissipative processes the corresponding terms are discretized by a DuFort-Frankel scheme. To always fulfill the Courant-Friedrichs-Lewy stability criterion, the time step of the code is adapted dynamically. Numerically induced local oscillations are suppressed by explicit, externally controlled diffusion terms. Non-equidistant grids are implemented, which enhance the spatial resolution, where needed. GOEMHD3 is parallelized based on the hybrid MPI-OpenMP programing paradigm, adopting a standard two-dimensional domain-decomposition approach. Results: The ideal part of the equation solver is verified by performing numerical tests of the evolution of the well-understood Kelvin-Helmholtz instability and of Orszag-Tang vortices. The accuracy of solving the (resistive) induction equation is tested by simulating the decay of a cylindrical current column. Furthermore, we show that the computational performance of the code scales very
3D Tomography of MHD Fluctuations in the H-1NF Heliac
Haskey, S R; Seiwald, B; Howard, J
2014-01-01
A 3D tomographic reconstruction technique which does not rely on a set of radial basis functions is described for inversion of a set of limited-angle high-resolution 2D visible light emission projections (extended in the vertical and toroidal directions) of global MHD eigenmodes in the H-1NF heliac. This paper deals with some of the features and challenges that will arise in the application of tomographic imaging systems to fusion reactors, especially the strong shaping of optimised stellarator/heliotron configurations, and limited access in all types. The fluctuations are represented as a finite sum of Fourier modes characterised by toroidal and poloidal mode numbers having fixed amplitude and phase in a set of nested cylindrical flux volumes in Boozer space. The amplitudes and phases are calculated using iterative tomographic inversion techniques such as ART, SIRT and standard linear least-squares methods. The tomography is applied to synchronous camera images of singly charged carbon impurity ion emission ...
Pseudo-reconnection in MHD numerical simulation
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
A class of pseudo-reconnections caused by a shifted mesh in magnetohydrodynamics (MHD) simulations is reported. In terms of this mesh system, some non-physical results may be obtained in certain circumstances, e.g. magnetic reconnection occurs without resistivity. After comparison, another kind of mesh is strongly recommended.
Nardon, E.; Fil, A.; Hoelzl, M.; Huijsmans, G.; contributors, JET
2017-01-01
3D non-linear MHD simulations of a D 2 massive gas injection (MGI) triggered disruption in JET with the JOREK code provide results which are qualitatively consistent with experimental observations and shed light on the physics at play. In particular, it is observed that the gas destabilizes a large m/n = 2/1 tearing mode, with the island O-point coinciding with the gas deposition region, by enhancing the plasma resistivity via cooling. When the 2/1 island gets so large that its inner side reaches the q = 3/2 surface, a 3/2 tearing mode grows. Simulations suggest that this is due to a steepening of the current profile right inside q = 3/2. Magnetic field stochastization over a large fraction of the minor radius as well as the growth of higher n modes ensue rapidly, leading to the thermal quench (TQ). The role of the 1/1 internal kink mode is discussed. An I p spike at the TQ is obtained in the simulations but with a smaller amplitude than in the experiment. Possible reasons are discussed.
A novel high-order, entropy stable, 3D AMR MHD solver with guaranteed positive pressure
Derigs, Dominik; Winters, Andrew R.; Gassner, Gregor J.; Walch, Stefanie
2016-07-01
We describe a high-order numerical magnetohydrodynamics (MHD) solver built upon a novel non-linear entropy stable numerical flux function that supports eight travelling wave solutions. By construction the solver conserves mass, momentum, and energy and is entropy stable. The method is designed to treat the divergence-free constraint on the magnetic field in a similar fashion to a hyperbolic divergence cleaning technique. The solver described herein is especially well-suited for flows involving strong discontinuities. Furthermore, we present a new formulation to guarantee positivity of the pressure. We present the underlying theory and implementation of the new solver into the multi-physics, multi-scale adaptive mesh refinement (AMR) simulation code FLASH (http://flash.uchicago.edu)
Zhilkin, A G; Mason, P A; 10.1134/S1063772912040087
2012-01-01
We performed 3D MHD calculations of stream accretion in cataclysmic variable stars for which the white dwarf primary star possesses a strong and complex magnetic field. These calculations are motivated by observations of polars; cataclysmic variables containing white dwarfs with magnetic fields sufficiently strong to prevent the formation of an accretion disk. So an accretion stream flows from the L1 point and impacts directly onto one or more spots on the surface of the white dwarf. Observations indicate that the white dwarf, in some binaries, possesses a complex (non-dipolar) magnetic field. We perform simulations of 10 polars or equivalently one asynchronous polar at 10 different beat phases. Our models have an aligned dipole plus quadrupole magnetic field centered on the white dwarf primary. We find that for a sufficiently strong quadrupole component an accretion spot occurs near the magnetic equator for slightly less than half of our simulations while a polar accretion zone is active for most of the rest...
Intensity contrast from MHD simulations and from HINODE observations
Afram, N; Solanki, S K; Schuessler, M; Lagg, A; Voegler, A
2010-01-01
Changes in the solar surface area covered by small-scale magnetic elements are thought to cause long-term changes in the solar spectral irradiance, which are important for determining the impact on Earth's climate. To study the effect of small-scale magnetic elements on total and spectral irradiance, we derive their contrasts from 3-D MHD simulations of the solar atmosphere. Such calculations are necessary since measurements of small-scale flux tube contrasts are confined to a few wavelengths and suffer from scattered light and instrument defocus, even for space observations. To test the contrast calculations, we compare rms contrasts from simulations with those obtained with the broad-band filter imager mounted on the Solar Optical Telescope (SOT) onboard the Hinode satellite and also analyse centre-to-limb variations (CLV). The 3-D MHD simulations include the interaction between convection and magnetic flux tubes. They have been run with non-grey radiative transfer using the MURaM code. Simulations have an ...
3D Convection-pulsation Simulations with the HERACLES Code
Felix, S.; Audit, E.; Dintrans, B.
2015-10-01
We present 3D simulations of the coupling between surface convection and pulsations due to the κ-mechanism in classical Cepheids of the red edge of Hertzsprung-Russell diagram's instability strip. We show that 3D convection is less powerful than 2D convection and does not quench the radiative pulsations, leading to an efficient 3D κ-mechanism. Thus, the 3D instability strip is closer to the observed one than the 1D or 2D were.
Inductive ionospheric solver for magnetospheric MHD simulations
Directory of Open Access Journals (Sweden)
H. Vanhamäki
2011-01-01
Full Text Available We present a new scheme for solving the ionospheric boundary conditions required in magnetospheric MHD simulations. In contrast to the electrostatic ionospheric solvers currently in use, the new solver takes ionospheric induction into account by solving Faraday's law simultaneously with Ohm's law and current continuity. From the viewpoint of an MHD simulation, the new inductive solver is similar to the electrostatic solvers, as the same input data is used (field-aligned current [FAC] and ionospheric conductances and similar output is produced (ionospheric electric field. The inductive solver is tested using realistic, databased models of an omega-band and westward traveling surge. Although the tests were performed with local models and MHD simulations require a global ionospheric solution, we may nevertheless conclude that the new solution scheme is feasible also in practice. In the test cases the difference between static and electrodynamic solutions is up to ~10 V km^{−1} in certain locations, or up to 20-40% of the total electric field. This is in agreement with previous estimates. It should also be noted that if FAC is replaced by the ground magnetic field (or ionospheric equivalent current in the input data set, exactly the same formalism can be used to construct an inductive version of the KRM method originally developed by Kamide et al. (1981.
Thurgood, J. O.; McLaughlin, J. A.
2012-09-01
Context. Coronal magnetic null points have been implicated as possible locations for localised heating events in 2D models. We investigate this possibility about fully 3D null points. Aims: We investigate the nature of the fast magnetoacoustic wave about a fully 3D magnetic null point, with a specific interest in its propagation, and we look for evidence of MHD mode coupling and/or conversion to the Alfvén mode. Methods: A special fieldline and flux-based coordinate system was constructed to permit the introduction of a pure fast magnetoacoustic wave in the vicinity of proper and improper 3D null points. We considered the ideal, β = 0, MHD equations, which are solved using the LARE3D numerical code. The constituent modes of the resulting wave were isolated and identified using the special coordinate system. Numerical results were supported by analytical work derived from perturbation theory and a linear implementation of the WKB method. Results: An initially pure fast wave is found to be permanently decoupled from the Alfvén mode both linearly and nonlinearly for both proper and improper 3D null points. The pure fast mode also generates and sustains a nonlinear disturbance aligned along the equilibrium magnetic field. The resulting pure fast magnetoacoustic pulse has transient behaviour, which is found to be governed by the (equilibrium) Alfvén-speed profile, and a refraction effect focuses all the wave energy towards the null point. Conclusions: Thus, the main results from previous 2D work do indeed carry over to the fully 3D magnetic null points and so we conclude that 3D null points are locations for preferential heating in the corona by 3D fast magnetoacoustic waves.
Charge collection characterization of a 3D silicon radiation detector by using 3D simulations
Kalliopuska, J; Orava, R
2007-01-01
In 3D detectors, the electrodes are processed within the bulk of the sensor material. Therefore, the signal charge is collected independently of the wafer thickness and the collection process is faster due to shorter distances between the charge collection electrodes as compared to a planar detector structure. In this paper, 3D simulations are used to assess the performance of a 3D detector structure in terms of charge sharing, efficiency and speed of charge collection, surface charge, location of the primary interaction and the bias voltage. The measured current pulse is proposed to be delayed due to the resistance–capacitance (RC) product induced by the variation of the serial resistance of the pixel electrode depending on the depth of the primary interaction. Extensive simulations are carried out to characterize the 3D detector structures and to verify the proposed explanation for the delay of the current pulse. A method for testing the hypothesis experimentally is suggested.
Jauer, P. R.; Gonzalez, W. D.; de Souza Costa, C. L.; Souza, V. M.
2013-12-01
The interaction, transport and conversion of energy between the solar wind and Earth's magnetosphere have been studied for decades through in situ measurements and Magnetohydrodynamics simulation, (MHD). Nevertheless, due to the vast regions of space and nonlinearities of the physical processes there are many questions that still remain without conclusive answers. Currently, the MHD simulation is a powerful tool that helps other means of already existing research, even within its theoretical limitation; it provides information of the space regions where in situ measurements are rare or nonexistent. The aim of this work is the study of energy transfer from the solar wind through the calculation of the divergence of the Poynting vector for the inner regions of the Earth's magnetosphere, especially the magneto tail using 3D global MHD numerical code Space Weather Modelling Framework (SWMF) / (Block Adaptive Tree Solar wind Roe Upwind Scheme) (BATS-R-US), developed by the University of Michigan. We conducted a simulation study for the event that occurred on September 21-27, 1999, for which the peak value of the interplanetary magnetic field was -22 nT, and gave rise to an intense magnetic storm with peak Dst of -160 nT. Furthermore, we compare the results of the power estimated by the model - through the integration of the Poynting vector in rectangular region of the tail, with a domain -130 powerful tool to reproduce the observations with a good degree of reliability.
BUSICO 3D: building simulation and control in unity 3D
DEFF Research Database (Denmark)
Fürst, Jonathan; Fierro, Gabe; Bonnet, Philippe;
2014-01-01
with simulations and easier transferring of schedules and configurations from the simulated virtual environment to a real-world deployment. We provide an implementation using a widely used game engine (Unity 3D) and sMAP (Simple Measurement and Actuation Profile), a developed time series database and metadata...
Thurgood, J O; 10.1051/0004-6361/201219850
2012-01-01
Context: Coronal magnetic null points have been implicated as possible locations for localised heating events in 2D models. We investigate this possibility about fully 3D null points. Aims: We investigate the nature of the fast magnetoacoustic wave about a fully 3D magnetic null point, with a specific interest in its propagation, and we look for evidence of MHD mode coupling and/or conversion to the Alfv\\'en mode. Methods: A special fieldline and flux-based coordinate system was constructed to permit the introduction of a pure fast magnetoacoustic wave in the vicinity of proper and improper 3D null points. We considered the ideal, {\\beta} = 0, MHD equations, which are solved using the LARE3D numerical code. The constituent modes of the resulting wave were isolated and identified using the special coordinate system. Numerical results were supported by analytical work derived from perturbation theory and a linear implementation of the WKB method. Results: An initially pure fast wave is found to be permanently d...
Simulation of bootstrap current in 2D and 3D ideal magnetic fields in tokamaks
Raghunathan, M.; Graves, J. P.; Cooper, W. A.; Pedro, M.; Sauter, O.
2016-09-01
We aim to simulate the bootstrap current for a MAST-like spherical tokamak using two approaches for magnetic equilibria including externally caused 3D effects such as resonant magnetic perturbations (RMPs), the effect of toroidal ripple, and intrinsic 3D effects such as non-resonant internal kink modes. The first approach relies on known neoclassical coefficients in ideal MHD equilibria, using the Sauter (Sauter et al 1999 Phys. Plasmas 6 2834) expression valid for all collisionalities in axisymmetry, and the second approach being the quasi-analytic Shaing-Callen (Shaing and Callen 1983 Phys. Fluids 26 3315) model in the collisionless regime for 3D. Using the ideal free-boundary magnetohydrodynamic code VMEC, we compute the flux-surface averaged bootstrap current density, with the Sauter and Shaing-Callen expressions for 2D and 3D ideal MHD equilibria including an edge pressure barrier with the application of resonant magnetic perturbations, and equilibria possessing a saturated non-resonant 1/1 internal kink mode with a weak internal pressure barrier. We compare the applicability of the self-consistent iterative model on the 3D applications and discuss the limitations and advantages of each bootstrap current model for each type of equilibrium.
3D visualization of port simulation.
Energy Technology Data Exchange (ETDEWEB)
Horsthemke, W. H.; Macal, C. M.; Nevins, M. R.
1999-06-14
Affordable and realistic three dimensional visualization technology can be applied to large scale constructive simulations such as the port simulation model, PORTSIM. These visualization tools enhance the experienced planner's ability to form mental models of how seaport operations will unfold when the simulation model is implemented and executed. They also offer unique opportunities to train new planners not only in the use of the simulation model but on the layout and design of seaports. Simulation visualization capabilities are enhanced by borrowing from work on interface design, camera control, and data presentation. Using selective fidelity, the designers of these visualization systems can reduce their time and efforts by concentrating on those features which yield the most value for their simulation. Offering the user various observational tools allows the freedom to simply watch or engage in the simulation without getting lost. Identifying the underlying infrastructure or cargo items with labels can provide useful information at the risk of some visual clutter. The PortVis visualization expands the PORTSIM user base which can benefit from the results provided by this capability, especially in strategic planning, mission rehearsal, and training. Strategic planners will immediately reap the benefits of seeing the impact of increased throughput visually without keeping track of statistical data. Mission rehearsal and training users will have an effective training tool to supplement their operational training exercises which are limited in number because of their high costs. Having another effective training modality in this visualization system allows more training to take place and more personnel to gain an understanding of seaport operations. This simulation and visualization training can be accomplished at lower cost than would be possible for the operational training exercises alone. The application of PORTSIM and PortVis will lead to more efficient
Interactive 3D display simulator for autostereoscopic smart pad
Choe, Yeong-Seon; Lee, Ho-Dong; Park, Min-Chul; Son, Jung-Young; Park, Gwi-Tae
2012-06-01
There is growing interest of displaying 3D images on a smart pad for entertainments and information services. Designing and realizing various types of 3D displays on the smart pad is not easy for costs and given time. Software simulation can be an alternative method to save and shorten the development. In this paper, we propose a 3D display simulator for autostereoscopic smart pad. It simulates light intensity of each view and crosstalk for smart pad display panels. Designers of 3D display for smart pad can interactively simulate many kinds of autostereoscopic displays interactively by changing parameters required for panel design. Crosstalk to reduce leakage of one eye's image into the image of the other eye, and light intensity for computing visual comfort zone are important factors in designing autostereoscopic display for smart pad. Interaction enables intuitive designs. This paper describes an interactive 3D display simulator for autostereoscopic smart pad.
3D MHD simulations of subsurface convection in OB stars
Cantiello, Matteo; Brandenburg, Axel; Del Sordo, Fabio; Käpylä, Petri; Langer, Norbert
2010-01-01
During their main sequence evolution, massive stars can develop convective regions very close to their surface. These regions are caused by an opacity peak associated with iron ionization. Cantiello et al. (2009) found a possible connection between the presence of sub-photospheric convective motions and small scale stochastic velocities in the photosphere of early-type stars. This supports a physical mechanism where microturbulence is caused by waves that are triggered by subsurface convection zones. They further suggest that clumping in the inner parts of the winds of OB stars could be related to subsurface convection, and that the convective layers may also be responsible for stochastic excitation of non-radial pulsations. Furthermore, magnetic fields produced in the iron convection zone could appear at the surface of such massive stars. Therefore subsurface convection could be responsible for the occurrence of observable phenomena such as line profile variability and discrete absorption components. These p...
A STUDY ON USING 3D VISUALIZATION AND SIMULATION PROGRAM (OPTITEX 3D ON LEATHER APPAREL
Directory of Open Access Journals (Sweden)
Ork Nilay
2016-05-01
Full Text Available Leather is a luxury garment. Design, material, labor, fitting and time costs are very effective on the production cost of the consumer leather good. 3D visualization and simulation programs which are getting popular in textile industry can be used for material, labor and time saving in leather apparel. However these programs have a very limited use in leather industry because leather material databases are not sufficient as in textile industry. In this research, firstly material properties of leather and textile fabric were determined by using both textile and leather physical test methods, and interpreted and introduced in the program. Detailed measures of an experimental human body were measured from a 3D body scanner. An avatar was designed according to these measurements. Then a prototype dress was made by using Computer Aided Design-CAD program for designing the patterns. After the pattern making, OptiTex 3D visualization and simulation program was used to visualize and simulate the dresses. Additionally the leather and cotton fabric dresses were sewn in real life. Then the visual and real life dresses were compared and discussed. 3D virtual prototyping seems a promising potential in future manufacturing technologies by evaluating the fitting of garments in a simple and quick way, filling the gap between 3D pattern design and manufacturing, providing virtual demonstrations to customers.
Willensdorfer, M; Strumberger, E; Suttrop, W; Vanovac, B; Brida, D; Cavedon, M; Classen, I; Dunne, M; Fietz, S; Fischer, R; Kirk, A; Laggner, F M; Liu, Y Q; Odstrcil, T; Ryan, D A; Viezzer, E; Zohm, H; Luhmann, I C
2016-01-01
The plasma response from an external n = 2 magnetic perturbation field in ASDEX Upgrade has been measured using mainly electron cyclotron emission (ECE) diagnostics and a rigid rotating field. To interpret ECE and ECE-imaging (ECE-I) measurements accurately, forward modeling of the radiation transport has been combined with ray tracing. The measured data is compared to synthetic ECE data generated from a 3D ideal magnetohydrodynamics (MHD) equilibrium calculated by VMEC. The measured amplitudes of the helical displacement in the midplane are in reasonable agreement with the one from the synthetic VMEC diagnostics. Both exceed the vacuum field calculations and indicate the presence of an amplified kink response at the edge. Although the calculated magnetic structure of this edge kink peaks at poloidal mode numbers larger than the resonant components |m| > |nq|, the displacement measured by ECE-I is almost resonant |m| ~ |nq|. This is expected from ideal MHD in the proximity of rational surfaces. VMEC and MARS-...
The intensity contrast of solar granulation: comparing Hinode SP results with MHD simulations
Danilovic, S.; Gandorfer, A.; Lagg, A.; SchÜssler, M.; Solanki, S.K.; Vögler, A.; Katsukawa, Y.; Tsuneta, S.
2008-01-01
Context. The contrast of granulation is an important quantity characterizing solar surface convection. Aims. We compare the intensity contrast at 630 nm, observed using the Spectro-Polarimeter (SP) aboard the Hinode satellite, with the 3D radiative MHD simulations of Vögler & Schüssler (2007, A&A, 4
MHD simulation studies of z-pinch shear flow stabilization
Paraschiv, I.; Bauer, B. S.; Sotnikov, V. I.; Makhin, V.; Siemon, R. E.
2003-10-01
The development of the m=0 instability in a z-pinch in the presence of sheared plasma flows is investigated with the aid of a two-dimensional magnetohydrodynamic (MHD) simulation code (MHRDR). The linear growth rates are compared to the results obtained by solving the ideal MHD linearized equations [1] and to the results obtained using a 3D hybrid simulation code [2]. The instability development is followed into the nonlinear regime where its growth and saturation are examined. [1] V.I. Sotnikov, I. Paraschiv, V. Makhin, B.S. Bauer, J.-N. Leboeuf, and J.M. Dawson, "Linear analysis of sheared flow stabilization of global magnetohydrodynamic instabilities based on the Hall fluid mode", Phys. Plasmas 9, 913 (2002). [2] V.I. Sotnikov, V. Makhin, B.S. Bauer, P. Hellinger, P. Travnicek, V. Fiala, J.-N. Leboeuf, "Hybrid Simulations of Current-Carrying Instabilities in Z-pinch Plasmas with Sheared Axial Flow", AIP Conference Proceedings, Volume 651, Dense Z-Pinches: 5th International Conference on Dense Z-Pinches, edited by J. Davis et al., page 396, June 2002.
Surviving sepsis--a 3D integrative educational simulator.
Ježek, Filip; Tribula, Martin; Kulhánek, Tomáš; Mateják, Marek; Privitzer, Pavol; Šilar, Jan; Kofránek, Jiří; Lhotská, Lenka
2015-08-01
Computer technology offers greater educational possibilities, notably simulation and virtual reality. This paper presents a technology which serves to integrate multiple modalities, namely 3D virtual reality, node-based simulator, Physiomodel explorer and explanatory physiological simulators employing Modelica language and Unity3D platform. This emerging tool chain should allow the authors to concentrate more on educational content instead of application development. The technology is demonstrated through Surviving sepsis educational scenario, targeted on Microsoft Windows Store platform.
Zhai, Xiaoping; Yin, Zhaoyang
2017-02-01
The present paper is dedicated to the global well-posedness for the 3D inhomogeneous incompressible Navier-Stokes equations, in critical Besov spaces without smallness assumption on the variation of the density. We aim at extending the work by Abidi, Gui and Zhang (2012) [2], and (2013) [3] to a lower regularity index about the initial velocity. The key to that improvement is a new a priori estimate for an elliptic equation with nonconstant coefficients in Besov spaces which have the same degree as L2 in R3. Finally, we also generalize our well-posedness result to the inhomogeneous incompressible MHD equations.
3D simulation for solitons used in optical fibers
Vasile, F.; Tebeica, C. M.; Schiopu, P.; Vladescu, M.
2016-12-01
In this paper is described 3D simulation for solitions used in optical fibers. In the scientific works is started from nonlinear propagation equation and the solitons represents its solutions. This paper presents the simulation of the fundamental soliton in 3D together with simulation of the second order soliton in 3D. These simulations help in the study of the optical fibers for long distances and in the interactions between the solitons. This study helps the understanding of the nonlinear propagation equation and for nonlinear waves. These 3D simulations are obtained using MATLAB programming language, and we can observe fundamental difference between the soliton and the second order/higher order soliton and in their evolution.
Coupled simulation of kinetic pedestal growth and MHD ELM crash
Energy Technology Data Exchange (ETDEWEB)
Park, G [Courant Institute of Mathematical Sciences, New York University (United States); Cummings, J [California Institute of Technology (United States); Chang, C S [Courant Institute of Mathematical Sciences, New York University (United States); Podhorszki, N [Univ. California at Davis (United States); Klasky, S [ORNL (United States); Ku, S [Courant Institute of Mathematical Sciences, New York University (United States); Pankin, A [Lehigh Univ. (United States); Samtaney, R [Princeton Plasma Physics Laboratory (United States); Shoshani, A [LBNL (United States); Snyder, P [General Atomics (United States); Strauss, H [Courant Institute of Mathematical Sciences, New York University (United States); Sugiyama, L [MIT (United States)
2007-07-15
Edge pedestal height and the accompanying ELM crash are critical elements of ITER physics yet to be understood and predicted through high performance computing. An entirely self-consistent first principles simulation is being pursued as a long term research goal, and the plan is planned for completion in time for ITER operation. However, a proof-of-principle work has already been established using a computational tool that employs the best first principles physics available at the present time. A kinetic edge equilibrium code XGC0, which can simulate the neoclassically dominant pedestal growth from neutral ionization (using a phenomenological residual turbulence diffusion motion superposed upon the neoclassical particle motion) is coupled to an extended MHD code M3D, which can perform the nonlinear ELM crash. The stability boundary of the pedestal is checked by an ideal MHD linear peeling-ballooning code, which has been validated against many experimental data sets for the large scale (type I) ELMs onset boundary. The coupling workflow and scientific results to be enabled by it are described.
Simulations on 3D shape tracking with fibre Bragg gratings
Hooft 't, G.W.; Tirard-Gâtel, A.
2010-01-01
This report deals with the development of a reconstruction algorithm of 3D optical shape sensing. The theoretical frame work is established and simulations are performed for a multicore fiber system without torque.
Numerical Relativity Towards Simulations of 3D Black Hole Coalescence
Seidel, E
1998-01-01
I review recent developments in numerical relativity, focussing on progress made in 3D black hole evolution. Progress in development of black hole initial data, apparent horizon boundary conditions, adaptive mesh refinement, and characteristic evolution is highlighted, as well as full 3D simulations of colliding and distorted black holes. For true 3D distorted holes, with Cauchy evolution techniques, it is now possible to extract highly accurate, nonaxisymmetric waveforms from fully nonlinear simulations, which are verified by comparison to pertubration theory, and with characteristic techniques extremely long term evolutions of 3D black holes are now possible. I also discuss a new code designed for 3D numerical relativity, called Cactus, that will be made public.
Design of 3D simulation engine for oilfield safety training
Li, Hua-Ming; Kang, Bao-Sheng
2015-03-01
Aiming at the demand for rapid custom development of 3D simulation system for oilfield safety training, this paper designs and implements a 3D simulation engine based on script-driven method, multi-layer structure, pre-defined entity objects and high-level tools such as scene editor, script editor, program loader. A scripting language been defined to control the system's progress, events and operating results. Training teacher can use this engine to edit 3D virtual scenes, set the properties of entity objects, define the logic script of task, and produce a 3D simulation training system without any skills of programming. Through expanding entity class, this engine can be quickly applied to other virtual training areas.
An Arbitrary Lagrangian-Eulerian Discretization of MHD on 3D Unstructured Grids
Energy Technology Data Exchange (ETDEWEB)
Rieben, R N; White, D A; Wallin, B K; Solberg, J M
2006-06-12
We present an arbitrary Lagrangian-Eulerian (ALE) discretization of the equations of resistive magnetohydrodynamics (MHD) on unstructured hexahedral grids. The method is formulated using an operator-split approach with three distinct phases: electromagnetic diffusion, Lagrangian motion, and Eulerian advection. The resistive magnetic dynamo equation is discretized using a compatible mixed finite element method with a 2nd order accurate implicit time differencing scheme which preserves the divergence-free nature of the magnetic field. At each discrete time step, electromagnetic force and heat terms are calculated and coupled to the hydrodynamic equations to compute the Lagrangian motion of the conducting materials. By virtue of the compatible discretization method used, the invariants of Lagrangian MHD motion are preserved in a discrete sense. When the Lagrangian motion of the mesh causes significant distortion, that distortion is corrected with a relaxation of the mesh, followed by a 2nd order monotonic remap of the electromagnetic state variables. The remap is equivalent to Eulerian advection of the magnetic flux density with a fictitious mesh relaxation velocity. The magnetic advection is performed using a novel variant of constrained transport (CT) that is valid for unstructured hexahedral grids with arbitrary mesh velocities. The advection method maintains the divergence free nature of the magnetic field and is second order accurate in regions where the solution is sufficiently smooth. For regions in which the magnetic field is discontinuous (e.g. MHD shocks) the method is limited using a novel variant of algebraic flux correction (AFC) which is local extremum diminishing (LED) and divergence preserving. Finally, we verify each stage of the discretization via a set of numerical experiments.
An Evaluative Review of Simulated Dynamic Smart 3d Objects
Romeijn, H.; Sheth, F.; Pettit, C. J.
2012-07-01
Three-dimensional (3D) modelling of plants can be an asset for creating agricultural based visualisation products. The continuum of 3D plants models ranges from static to dynamic objects, also known as smart 3D objects. There is an increasing requirement for smarter simulated 3D objects that are attributed mathematically and/or from biological inputs. A systematic approach to plant simulation offers significant advantages to applications in agricultural research, particularly in simulating plant behaviour and the influences of external environmental factors. This approach of 3D plant object visualisation is primarily evident from the visualisation of plants using photographed billboarded images, to more advanced procedural models that come closer to simulating realistic virtual plants. However, few programs model physical reactions of plants to external factors and even fewer are able to grow plants based on mathematical and/or biological parameters. In this paper, we undertake an evaluation of plant-based object simulation programs currently available, with a focus upon the components and techniques involved in producing these objects. Through an analytical review process we consider the strengths and weaknesses of several program packages, the features and use of these programs and the possible opportunities in deploying these for creating smart 3D plant-based objects to support agricultural research and natural resource management. In creating smart 3D objects the model needs to be informed by both plant physiology and phenology. Expert knowledge will frame the parameters and procedures that will attribute the object and allow the simulation of dynamic virtual plants. Ultimately, biologically smart 3D virtual plants that react to changes within an environment could be an effective medium to visually represent landscapes and communicate land management scenarios and practices to planners and decision-makers.
Global MHD simulations of Neptune's magnetosphere
Mejnertsen, L.; Eastwood, J. P.; Chittenden, J. P.; Masters, A.
2016-08-01
A global magnetohydrodynamic (MHD) simulation has been performed in order to investigate the outer boundaries of Neptune's magnetosphere at the time of Voyager 2's flyby in 1989 and to better understand the dynamics of magnetospheres formed by highly inclined planetary dipoles. Using the MHD code Gorgon, we have implemented a precessing dipole to mimic Neptune's tilted magnetic field and rotation axes. By using the solar wind parameters measured by Voyager 2, the simulation is verified by finding good agreement with Voyager 2 magnetometer observations. Overall, there is a large-scale reconfiguration of magnetic topology and plasma distribution. During the "pole-on" magnetospheric configuration, there only exists one tail current sheet, contained between a rarefied lobe region which extends outward from the dayside cusp, and a lobe region attached to the nightside cusp. It is found that the tail current always closes to the magnetopause current system, rather than closing in on itself, as suggested by other models. The bow shock position and shape is found to be dependent on Neptune's daily rotation, with maximum standoff being during the pole-on case. Reconnection is found on the magnetopause but is highly modulated by the interplanetary magnetic field (IMF) and time of day, turning "off" and "on" when the magnetic shear between the IMF and planetary fields is large enough. The simulation shows that the most likely location for reconnection to occur during Voyager 2's flyby was far from the spacecraft trajectory, which may explain the relative lack of associated signatures in the observations.
Sunspot Modeling: From Simplified Models to Radiative MHD Simulations
Directory of Open Access Journals (Sweden)
Rolf Schlichenmaier
2011-09-01
Full Text Available We review our current understanding of sunspots from the scales of their fine structure to their large scale (global structure including the processes of their formation and decay. Recently, sunspot models have undergone a dramatic change. In the past, several aspects of sunspot structure have been addressed by static MHD models with parametrized energy transport. Models of sunspot fine structure have been relying heavily on strong assumptions about flow and field geometry (e.g., flux-tubes, "gaps", convective rolls, which were motivated in part by the observed filamentary structure of penumbrae or the necessity of explaining the substantial energy transport required to maintain the penumbral brightness. However, none of these models could self-consistently explain all aspects of penumbral structure (energy transport, filamentation, Evershed flow. In recent years, 3D radiative MHD simulations have been advanced dramatically to the point at which models of complete sunspots with sufficient resolution to capture sunspot fine structure are feasible. Here overturning convection is the central element responsible for energy transport, filamentation leading to fine-structure and the driving of strong outflows. On the larger scale these models are also in the progress of addressing the subsurface structure of sunspots as well as sunspot formation. With this shift in modeling capabilities and the recent advances in high resolution observations, the future research will be guided by comparing observation and theory.
Preliminary investigations on 3D PIC simulation of DPHC structure using NEPTUNE3D code
Zhao, Hailong; Dong, Ye; Zhou, Haijing; Zou, Wenkang; Wang, Qiang
2016-10-01
Cubic region (34cm × 34cm × 18cm) including the double post-hole convolute (DPHC) structure was chosen to perform a series of fully 3D PIC simulations using NEPTUNE3D codes, massive data ( 200GB) could be acquired and solved in less than 5 hours. Cold-chamber tests were performed during which only cathode electron emission was considered without temperature rise or ion emission, current loss efficiency was estimated by comparisons between output magnetic field profiles with or without electron emission. PIC simulation results showed three stages of current transforming process with election emission in DPHC structure, the maximum ( 20%) current loss was 437kA at 15ns, while only 0.46% 0.48% was lost when driving current reached its peak. DPHC structure proved valuable functions during energy transform process in PTS facility, and NEPTUNE3D provided tools to explore this sophisticated physics. Project supported by the National Natural Science Foundation of China, Grant No. 11571293, 11505172.
Magnetic fields in protoplanetary disks: from MHD simulations to ALMA observations
Bertrang, Gesa H -M; Wolf, Sebastian
2016-01-01
Magnetic fields significantly influence the evolution of protoplanetary disks and the formation of planets, following the predictions of numerous magnetohydrodynamic (MHD) simulations. However, these predictions are yet observationally unconstrained. To validate the predictions on the influence of magnetic fields on protoplanetary disks, we apply 3D radiative transfer simulations of the polarized emission of aligned aspherical dust grains that directly link 3D global non-ideal MHD simulations to ALMA observations. Our simulations show that it is feasible to observe the predicted toroidal large-scale magnetic field structures, not only in the ideal observations but also with high-angular resolution ALMA observations. Our results show further that high angular resolution observations by ALMA are able to identify vortices embedded in outer magnetized disk regions.
Magnetic fields in protoplanetary discs: from MHD simulations to ALMA observations
Bertrang, G. H.-M.; Flock, M.; Wolf, S.
2017-01-01
Magnetic fields significantly influence the evolution of protoplanetary discs and the formation of planets, following the predictions of numerous magnetohydrodynamic (MHD) simulations. However, these predictions are yet observationally unconstrained. To validate the predictions on the influence of magnetic fields on protoplanetary discs, we apply 3D radiative transfer simulations of the polarized emission of aligned aspherical dust grains that directly link 3D global non-ideal MHD simulations to Atacama Large Millimeter/submillimeter Array (ALMA) observations. Our simulations show that it is feasible to observe the predicted toroidal large-scale magnetic field structures, not only in the ideal observations but also with high-angular resolution ALMA observations. Our results show further that high-angular resolution observations by ALMA are able to identify vortices embedded in outer magnetized disc regions.
Comparison of solar photospheric bright points between SUNRISE observations and MHD simulations
Riethmüller, T L; Berdyugina, S V; Schüssler, M; Pillet, V Mart\\'\\inez; Feller, A; Gandorfer, A; Hirzberger, J
2014-01-01
Bright points (BPs) in the solar photosphere are radiative signatures of magnetic elements described by slender flux tubes located in the darker intergranular lanes. They contribute to the ultraviolet (UV) flux variations over the solar cycle and hence may influence the Earth's climate. Here we combine high-resolution UV and spectro-polarimetric observations of BPs by the SUNRISE observatory with 3D radiation MHD simulations. Full spectral line syntheses are performed with the MHD data and a careful degradation is applied to take into account all relevant instrumental effects of the observations. It is demonstrated that the MHD simulations reproduce the measured distributions of intensity at multiple wavelengths, line-of-sight velocity, spectral line width, and polarization degree rather well. Furthermore, the properties of observed BPs are compared with synthetic ones. These match also relatively well, except that the observations display a tail of large and strongly polarized BPs not found in the simulation...
3D Ultrasonic Wave Simulations for Structural Health Monitoring
Campbell, Leckey Cara A/; Miler, Corey A.; Hinders, Mark K.
2011-01-01
Structural health monitoring (SHM) for the detection of damage in aerospace materials is an important area of research at NASA. Ultrasonic guided Lamb waves are a promising SHM damage detection technique since the waves can propagate long distances. For complicated flaw geometries experimental signals can be difficult to interpret. High performance computing can now handle full 3-dimensional (3D) simulations of elastic wave propagation in materials. We have developed and implemented parallel 3D elastodynamic finite integration technique (3D EFIT) code to investigate ultrasound scattering from flaws in materials. EFIT results have been compared to experimental data and the simulations provide unique insight into details of the wave behavior. This type of insight is useful for developing optimized experimental SHM techniques. 3D EFIT can also be expanded to model wave propagation and scattering in anisotropic composite materials.
Simulation and test of 3D silicon radiation detectors
Energy Technology Data Exchange (ETDEWEB)
Fleta, C. [Department of Physics and Astronomy, University of Glasgow, Glasgow, Scotland (United Kingdom)], E-mail: c.fleta@physics.gla.ac.uk; Pennicard, D.; Bates, R.; Parkes, C. [Department of Physics and Astronomy, University of Glasgow, Glasgow, Scotland (United Kingdom); Pellegrini, G.; Lozano, M. [Centro Nacional de Microelectronica, (CNM-IMB, CSIC), Barcelona (Spain); Wright, V. [Diamond Light Source, Oxfordshire (United Kingdom); Boscardin, M.; Dalla Betta, G.-F.; Piemonte, C.; Pozza, A.; Ronchin, S.; Zorzi, N. [ITC-IRST, Trento (Italy)
2007-09-01
The work presented here is the result of the collaborative effort between the University of Glasgow, ITC-IRST (Trento) and IMB-CNM (Barcelona) in the framework of the CERN-RD50 Collaboration to produce 3D silicon radiation detectors and study their performance. This paper reports on two sets of 3D devices. IRST and CNM have fabricated a set of single-type column 3D detectors, which have columnar electrodes of the same doping type and an ohmic contact located at the backplane. Simulations of the device behaviour and electrical test results are presented. In particular, current-voltage, capacitance-voltage and charge collection efficiency measurements are reported. Other types of structures called double-sided 3D detectors are currently being fabricated at CNM. In these detectors the sets of n and p columns are made on opposite sides of the device. Electrical and technological simulations and first processing results are presented.
Statistical 3D damage accumulation model for ion implant simulators
Energy Technology Data Exchange (ETDEWEB)
Hernandez-Mangas, J.M. E-mail: jesman@ele.uva.es; Lazaro, J.; Enriquez, L.; Bailon, L.; Barbolla, J.; Jaraiz, M
2003-04-01
A statistical 3D damage accumulation model, based on the modified Kinchin-Pease formula, for ion implant simulation has been included in our physically based ion implantation code. It has only one fitting parameter for electronic stopping and uses 3D electron density distributions for different types of targets including compound semiconductors. Also, a statistical noise reduction mechanism based on the dose division is used. The model has been adapted to be run under parallel execution in order to speed up the calculation in 3D structures. Sequential ion implantation has been modelled including previous damage profiles. It can also simulate the implantation of molecular and cluster projectiles. Comparisons of simulated doping profiles with experimental SIMS profiles are presented. Also comparisons between simulated amorphization and experimental RBS profiles are shown. An analysis of sequential versus parallel processing is provided.
Statistical 3D damage accumulation model for ion implant simulators
Hernandez-Mangas, J M; Enriquez, L E; Bailon, L; Barbolla, J; Jaraiz, M
2003-01-01
A statistical 3D damage accumulation model, based on the modified Kinchin-Pease formula, for ion implant simulation has been included in our physically based ion implantation code. It has only one fitting parameter for electronic stopping and uses 3D electron density distributions for different types of targets including compound semiconductors. Also, a statistical noise reduction mechanism based on the dose division is used. The model has been adapted to be run under parallel execution in order to speed up the calculation in 3D structures. Sequential ion implantation has been modelled including previous damage profiles. It can also simulate the implantation of molecular and cluster projectiles. Comparisons of simulated doping profiles with experimental SIMS profiles are presented. Also comparisons between simulated amorphization and experimental RBS profiles are shown. An analysis of sequential versus parallel processing is provided.
Čillo, Vladimír
2015-01-01
Tato bakalářská práce se zabýva návrhem a implementací simulátoru 3D tiskárny v jazyce C++ s využitím knihovny Qt. Simulátor předpokládá tiskárnu založenou na nejrozšířenější metodě 3D tisku - Fused Deposition Modeling. Vstupem simulátoru je 3D model ve formátu STL. Pro daný 3D model simulátor poskytuje odhad celkové doby tisku. Součástí simulace je také vizualizace procesu 3D tisku. Výsledkem práce je přenositelný program testovaný pod operačními systémy Linux a Windows. Funkčnost simulátoru...
3d visualization of atomistic simulations on every desktop
Peled, Dan; Silverman, Amihai; Adler, Joan
2013-08-01
Once upon a time, after making simulations, one had to go to a visualization center with fancy SGI machines to run a GL visualization and make a movie. More recently, OpenGL and its mesa clone have let us create 3D on simple desktops (or laptops), whether or not a Z-buffer card is present. Today, 3D a la Avatar is a commodity technique, presented in cinemas and sold for home TV. However, only a few special research centers have systems large enough for entire classes to view 3D, or special immersive facilities like visualization CAVEs or walls, and not everyone finds 3D immersion easy to view. For maximum physics with minimum effort a 3D system must come to each researcher and student. So how do we create 3D visualization cheaply on every desktop for atomistic simulations? After several months of attempts to select commodity equipment for a whole room system, we selected an approach that goes back a long time, even predating GL. The old concept of anaglyphic stereo relies on two images, slightly displaced, and viewed through colored glasses, or two squares of cellophane from a regular screen/projector or poster. We have added this capability to our AViz atomistic visualization code in its new, 6.1 version, which is RedHat, CentOS and Ubuntu compatible. Examples using data from our own research and that of other groups will be given.
Non-twist map bifurcation of drift-lines and drift-island formation in saturated 3D MHD equilibria
Pfefferle, David; Cooper, Wilfred A.; Graves, Jonathan P.
2015-11-01
Based on non-canonical perturbation theory, guiding-centre drift equations are identified as perturbed magnetic field-line equations. The topology of passing-particle orbits, called drift-lines, is completely determined by the magnetic configuration. In axisymmetric tokamak fields, drift-lines lie on shifted flux-surfaces, called drift-surfaces. Field-lines and drift-lines are subject to island structures at rational surfaces only when a non-axisymmetric component is added. The picture is different in the case of 3D saturated MHD equilibrium like the helical core associated with a non-resonant internal kink mode. In assuming nested flux-surfaces, these bifurcated states, expected for a reversed q-profile with qmin close yet above unity and conveniently obtained in VMEC, feature integrable field-lines. The helical drift-lines however become resonant with the axisymmetric component in the region of qmin and spontaneously generate drift-islands. Due to the locally reversed sheared q-profile, the drift-island structure follows the bifurcation/reconnection mechanism of non-twist maps. This result provides a theoretical interpretation of NBI fast ion helical hot-spots in Long-Lived Modes as well as snake-like impurity density accumulation in internal MHD activity.
3-D numerical simulations of coronal loops oscillations
Directory of Open Access Journals (Sweden)
M. Selwa
2009-10-01
Full Text Available We present numerical results of 3-D MHD model of a dipole active region field containing a loop with a higher density than its surroundings. We study different ways of excitation of vertical kink oscillations by velocity perturbation: as an initial condition, and as an impulsive excitation with a pulse of a given position, duration, and amplitude. These properties are varied in the parametric studies. We find that the amplitude of vertical kink oscillations is significantly amplified in comparison to horizontal kink oscillations for exciters located centrally (symmetrically below the loop, but not if the exciter is located a significant distance to the side of the loop. This explains why the pure vertical kink mode is so rarely observed in comparison to the horizontally polarized one. We discuss the role of curved magnetic field lines and the pulse overlapping at one of the loop's footpoints in 3-D active regions (AR's on the excitation and the damping of slow standing waves. We find that footpoint excitation becomes more efficient in 3-D curved loops than in 2-D curved arcades and that slow waves can be excited within an interval of time that is comparable to the observed one wave-period due to the combined effect of the pulse inside and outside the loop. Additionally, we study the effect of AR topology on the excitation and trapping of loop oscillations. We find that a perturbation acting directly on a single loop excites oscillations, but results in an increased leakage compared to excitation of oscillations in an AR field by an external source.
Nakamizo, A.; Tanaka, T.
2006-12-01
Existing global models of the solar-wind/IMF expanding to the Earth's orbit are basically grounded in the idea of "source surface." It is widely accepted that the sector structure and the solar wind speed are primarily controlled by the magnetic field at the source surface and the so-called "expansion factor." On the other hand, 3-D MHD model is still off from practical use because both of scientific and technical problems. One of the former problems is the reproduction of supersonic solar-wind. From the viewpoint of the physics of the solar wind, coronal heating and outward acceleration mechanisms are invoked to explain the supersonic evolution of the solar wind. Since the mechanism responsible for the heating/acceleration is still one of the primary subjects of the physics of the solar wind, many MHD models have taken into account their effects by incorporating additional source terms corresponding to promising candidates such as thermal conductions, radiation losses and wave pressures. However there are few MHD models considering the effect of the expansion factor, which determines the solar-wind speed in the series of source surface models. In this study we newly incorporate the flux tube expansion rate into the MHD equation system including heat source function in the energy equation. Appling the unstructured grid system, we achieved the dense grid spacing at the inner boundary, which enable us to adopt realistic solar magnetic fields, and a size of simulation space of 1AU. Photospheric magnetic field data is used as the inner boundary condition.The simulation results are summarized as: (1) The variation of solar wind speed is well controlled by the structure of magnetic fields at and little above the solar surface and (2) Far above the solar surface, the interface between high and low speed flows evolves to a structure suggestive of CIRs. Comparing the data from simulation with the actual solar wind data obtained by spacecrafts, we will discuss the future
Simulation of MHD collimation from differential rotation
Carey, Christopher
2005-10-01
Recent observations indicate that astrophysical outflows from active galactic nuclei are permeated with helical magnetic fields[1]. The most promising theory for the formation of the magnetic configurations in these magnetically driven jets is the coiling of an initial seed field by the differential rotation of the accretion disk surrounding the central object. We have begun simulations that are relevant to these Poynting jets using the NIMROD code[2]. To simulate dynamics on length scales that are significantly larger than the accretion disk, the non-relativistic MHD equations are evolved on a hemispherical logarithmic mesh. The accretion disk is treated as a condition on the lower boundary by applying a Keplerian velocity to the azimuthal component of the fluid velocity and a prescribed flux of mass through the boundary. The magnetic field configuration is initialized to a dipole like field. Formation of a jet outflow is observed later in time. The initial field is coiled up and collimated, driving a large current density on the axis of symmetry. Slipping of magnetic field lines due to non-ideal effects has been investigated. 1. Asada K. et. al., Pub. of the Astr. Soc. of Japan, 54, L39-L43, 2002 2. Sovinec C. et. al., J. Comp. Phys., 195, 355-386, 2004
3D numerical simulation of transient processes in hydraulic turbines
Energy Technology Data Exchange (ETDEWEB)
Cherny, S; Chirkov, D; Lapin, V; Eshkunova, I [Institute of Computational Technologies SB RAS Acad. Lavrentjev avenue 6, Novosibirsk, 630090 (Russian Federation); Bannikov, D; Avdushenko, A [Department of Mechanics and Mathematics, Novosibirsk State University Pirogov st. 2, Novosibirsk, 630090 (Russian Federation); Skorospelov, V, E-mail: chirkov@ict.nsc.r [Institute of Mathematics SB RAS Acad. Koptug avenue 4, Novosibirsk, 630090 (Russian Federation)
2010-08-15
An approach for numerical simulation of 3D hydraulic turbine flows in transient operating regimes is presented. The method is based on a coupled solution of incompressible RANS equations, runner rotation equation, and water hammer equations. The issue of setting appropriate boundary conditions is considered in detail. As an illustration, the simulation results for runaway process are presented. The evolution of vortex structure and its effect on computed runaway traces are analyzed.
3D numerical simulation of transient processes in hydraulic turbines
Cherny, S.; Chirkov, D.; Bannikov, D.; Lapin, V.; Skorospelov, V.; Eshkunova, I.; Avdushenko, A.
2010-08-01
An approach for numerical simulation of 3D hydraulic turbine flows in transient operating regimes is presented. The method is based on a coupled solution of incompressible RANS equations, runner rotation equation, and water hammer equations. The issue of setting appropriate boundary conditions is considered in detail. As an illustration, the simulation results for runaway process are presented. The evolution of vortex structure and its effect on computed runaway traces are analyzed.
3D Field Simulation of Magnetic Thin Film Inductor
FUJIWARA, Toshiyasu; CHOI, Kyung-Ku; SATO, SHIGEKI
2006-01-01
The 3D magnetic field simulations with FEM (finite element method) have been performed to predictand understand the performance of Magnetic Thin Film Inductor (MTFl). Inductor structures of planar electroplated Cu spiralcoil, which are sandwiched and underlaid with magnetic thin films, are considered as the simulation models. The inductance increment of 300% compared to air-core inductor was predicted when the sandwiched 5μm thickness magnetic thin film with relative permeability of 600 was a...
VISRAD, 3-D Target Design and Radiation Simulation Code
Golovkin, Igor; Macfarlane, Joseph; Golovkina, Viktoriya
2016-10-01
The 3-D view factor code VISRAD is widely used in designing HEDP experiments at major laser and pulsed-power facilities, including NIF, OMEGA, OMEGA-EP, ORION, LMJ, Z, and PLX. It simulates target designs by generating a 3-D grid of surface elements, utilizing a variety of 3-D primitives and surface removal algorithms, and can be used to compute the radiation flux throughout the surface element grid by computing element-to-element view factors and solving power balance equations. Target set-up and beam pointing are facilitated by allowing users to specify positions and angular orientations using a variety of coordinates systems (e.g., that of any laser beam, target component, or diagnostic port). Analytic modeling for laser beam spatial profiles for OMEGA DPPs and NIF CPPs is used to compute laser intensity profiles throughout the grid of surface elements. We will discuss recent improvements to the software package and plans for future developments.
Chromospheric heating and structure as determined from high resolution 3D simulations
Carlsson, Mats; Gudiksen, Boris V
2010-01-01
We have performed 3D radiation MHD simulations extending from the convection zone to the corona covering a box 16 Mm$^3$ at 32 km spatial resolution. The simulations show very fine structure in the chromosphere with acoustic shocks interacting with the magnetic field. Magnetic flux concentrations have a temperature lower than the surroundings in the photosphere but higher in the low chromosphere. The heating is there mostly through ohmic dissipation preferentially at the edges of the flux concentrations. The magnetic field is often wound up around the flux concentrations. When acoustic waves travel up along the field this topology leads to swirling motions seen in chromospheric diagnostic lines such as the calcium infrared triplet.
3-D Simulation of Vertical-Axial Tidal Current Turbine
Directory of Open Access Journals (Sweden)
Zhiyang Zhang
2016-12-01
Full Text Available Vertical-axial tidal current turbine is the key for the energy converter, which has the advantages of simple structure, adaptability to flow and uncomplex convection device. It has become the hot point for research and application recently. At present, the study on the hydrodynamic performance of vertical-axial tidal current turbine is almost on 2-D numerical simulation, without the consideration of 3-D effect. CFD (Computational Fluid Dynamics method and blade optimal control technique are used to improve accuracy in the prediction of tidal current turbine hydrodynamic performance. Numerical simulation of vertical-axial tidal current turbine is validated. Fixed and variable deflection angle turbine are comparatively studied to analysis the influence of 3-D effect and the character of fluid field and pressure field. The method, put the plate on the end of blade, of reduce the energy loss caused by 3-D effect is proposed. The 3-D CFD numerical model of vertical-axial tidal current turbine hydrodynamic performance in this study may provide theoretical, methodical and technical reference for the optimal design of turbine.
A FLOSS Visual EM Simulator for 3D Antennas
Koutsos, Christos A; Zimourtopoulos, Petros E
2010-01-01
This paper introduces the FLOSS Free Libre Open Source Software [VEMSA3D], a contraction of "Visual Electromagnetic Simulator for 3D Antennas", which are geometrically modeled, either exactly or approximately, as thin wire polygonal structures; presents its GUI Graphical User Interface capabilities, in interactive mode and/or in handling suitable formed antenna data files; demonstrates the effectiveness of its use in a number of practical antenna applications, with direct comparison to experimental measurements and other freeware results; and provides the inexperienced user with a specific list of instructions to successfully build the given source code by using only freely available IDE Integrated Development Environment tools-including a cross-platform one. The unrestricted access to source code, beyond the ability for immediate software improvement, offers to independent users and volunteer groups an expandable, in any way, visual antenna simulator, for a genuine research and development work in the field ...
Comparative visual analysis of 3D urban wind simulations
Röber, Niklas; Salim, Mohamed; Grawe, David; Leitl, Bernd; Böttinger, Michael; Schlünzen, Heinke
2016-04-01
Climate simulations are conducted in large quantity for a variety of different applications. Many of these simulations focus on global developments and study the Earth's climate system using a coupled atmosphere ocean model. Other simulations are performed on much smaller regional scales, to study very small fine grained climatic effects. These microscale climate simulations pose similar, yet also different, challenges for the visualization and the analysis of the simulation data. Modern interactive visualization and data analysis techniques are very powerful tools to assist the researcher in answering and communicating complex research questions. This presentation discusses comparative visualization for several different wind simulations, which were created using the microscale climate model MITRAS. The simulations differ in wind direction and speed, but are all centered on the same simulation domain: An area of Hamburg-Wilhelmsburg that hosted the IGA/IBA exhibition in 2013. The experiments contain a scenario case to analyze the effects of single buildings, as well as examine the impact of the Coriolis force within the simulation. The scenario case is additionally compared with real measurements from a wind tunnel experiment to ascertain the accuracy of the simulation and the model itself. We also compare different approaches for tree modeling and evaluate the stability of the model. In this presentation, we describe not only our workflow to efficiently and effectively visualize microscale climate simulation data using common 3D visualization and data analysis techniques, but also discuss how to compare variations of a simulation and how to highlight the subtle differences in between them. For the visualizations we use a range of different 3D tools that feature techniques for statistical data analysis, data selection, as well as linking and brushing.
Advances in the numerical simulation of 3D FSW processes
Agelet de Saracibar Bosch, Carlos; Chiumenti, Michèle; Cervera Ruiz, Miguel; Dialami, Narges; Santiago, Diego de; Lombera, Guillermo
2011-01-01
This work deals with the computational modeling and numerical simulation of 3D Friction Stir Welding (FSW) processes. Eulerian and ALE formulations have been used to solve the quasi-static thermal transient governing equations. Mixed P2/P1/P2+SUPG and subgrid-scale stabilized P1/P1/P1 velocity/pressure/temperature elements have been implemented. Norton-Hoff and Sheppard-Wright rigid thermoplastic material models have been considered. Computational visualization techniques using tracers have b...
Junk, S.
2016-08-01
Today the methods of numerical simulation of sheet metal forming offer a great diversity of possibilities for optimization in product development and in process design. However, the results from simulation are only available as virtual models. Because there are any forming tools available during the early stages of product development, physical models that could serve to represent the virtual results are therefore lacking. Physical 3D-models can be created using 3D-printing and serve as an illustration and present a better understanding of the simulation results. In this way, the results from the simulation can be made more “comprehensible” within a development team. This paper presents the possibilities of 3D-colour printing with particular consideration of the requirements regarding the implementation of sheet metal forming simulation. Using concrete examples of sheet metal forming, the manufacturing of 3D colour models will be expounded upon on the basis of simulation results.
Simulation of human ischemic stroke in realistic 3D geometry
Dumont, Thierry; Duarte, Max; Descombes, Stéphane; Dronne, Marie-Aimée; Massot, Marc; Louvet, Violaine
2013-06-01
In silico research in medicine is thought to reduce the need for expensive clinical trials under the condition of reliable mathematical models and accurate and efficient numerical methods. In the present work, we tackle the numerical simulation of reaction-diffusion equations modeling human ischemic stroke. This problem induces peculiar difficulties like potentially large stiffness which stems from the broad spectrum of temporal scales in the nonlinear chemical source term as well as from the presence of steep spatial gradients in the reaction fronts, spatially very localized. Furthermore, simulations on realistic 3D geometries are mandatory in order to describe correctly this type of phenomenon. The main goal of this article is to obtain, for the first time, 3D simulations on realistic geometries and to show that the simulation results are consistent with those obtain in experimental studies or observed on MRI images in stroke patients. For this purpose, we introduce a new resolution strategy based mainly on time operator splitting that takes into account complex geometry coupled with a well-conceived parallelization strategy for shared memory architectures. We consider then a high order implicit time integration for the reaction and an explicit one for the diffusion term in order to build a time operator splitting scheme that exploits efficiently the special features of each problem. Thus, we aim at solving complete and realistic models including all time and space scales with conventional computing resources, that is on a reasonably powerful workstation. Consequently and as expected, 2D and also fully 3D numerical simulations of ischemic strokes for a realistic brain geometry, are conducted for the first time and shown to reproduce the dynamics observed on MRI images in stroke patients. Beyond this major step, in order to improve accuracy and computational efficiency of the simulations, we indicate how the present numerical strategy can be coupled with spatial
Fisher, Dustin; Zhang, Yue; Wallace, Ben; Gilmore, Mark; Manchester, Ward; Arge, C. Nick
2016-10-01
The Plasma Bubble Expansion Experiment (PBEX) at the University of New Mexico uses a coaxial plasma gun to launch jet and spheromak magnetic plasma configurations into the Helicon-Cathode (HelCat) plasma device. Plasma structures launched from the gun drag frozen-in magnetic flux into the background magnetic field of the chamber providing a rich set of dynamics to study magnetic turbulence, force-free magnetic spheromaks, and shocks. Preliminary modeling is presented using the highly-developed 3-D, MHD, BATS-R-US code developed at the University of Michigan. BATS-R-US employs an adaptive mesh refinement grid that enables the capture and resolution of shock structures and current sheets, and is particularly suited to model the parameter regime under investigation. CCD images and magnetic field data from the experiment suggest the stabilization of an m =1 kink mode trailing a plasma jet launched into a background magnetic field. Results from a linear stability code investigating the effect of shear-flow as a cause of this stabilization from magnetic tension forces on the jet will be presented. Initial analyses of a possible magnetic Rayleigh Taylor instability seen at the interface between launched spheromaks and their entraining background magnetic field will also be presented. Work supported by the Army Research Office Award No. W911NF1510480.
Optimization of a fully 3D single scatter simulation algorithm for 3D PET
Energy Technology Data Exchange (ETDEWEB)
Accorsi, Roberto [Division of Nuclear Medicine, Department of Radiology, Children' s Hospital of Philadelphia, 34th and Civic Center Blvd, Philadelphia, PA 19104 (United States); Adam, Lars-Eric [Department of Radiology, University of Pennsylvania School of Medicine, 423 Guardian Dr, Philadelphia, PA 19104 (United States); Werner, Matthew E [Philips Medical Systems, 3619 Market St, Philadelphia, PA 19104 (United States); Karp, Joel S [Department of Radiology, University of Pennsylvania School of Medicine, 423 Guardian Dr, Philadelphia, PA 19104 (United States)
2004-06-21
We describe a new implementation of a single scatter simulation (SSS) algorithm for the prediction and correction of scatter in 3D PET. In this implementation, out of field of view (FoV) scatter and activity, side shields and oblique tilts are explicitly modelled. Comparison of SSS predictions with Monte Carlo simulations and experimental data from uniform, line and cold-bar phantoms showed that the code is accurate for uniform as well as asymmetric objects and can model different energy resolution crystals and low level discriminator (LLD) settings. Absolute quantitation studies show that for most applications, the code provides a better scatter estimate than the tail-fitting scatter correction method currently in use at our institution. Several parameters such as the density of scatter points, the number of scatter distribution sampling points and the axial extent of the FoV were optimized to minimize execution time, with particular emphasis on patient studies. Development and optimization were carried out in the case of GSO-based scanners, which enjoy relatively good energy resolution. SSS estimates for scanners with lower energy resolution may result in different agreement, especially because of a higher fraction of multiple scatter events. The algorithm was applied to a brain phantom as well as to clinical whole-body studies. It proved robust in the case of large patients, where the scatter fraction increases. The execution time, inclusive of interpolation, is typically under 5 min for a whole-body study (axial FoV: 81 cm) of a 100 kg patient.
Simulation of AIMS measurements using rigorous mask 3D modeling
Chou, Chih-Shiang; Huang, Hsu-Ting; Chu, Fu-Sheng; Chu, Yuan-Chih; Huang, Wen-Chun; Liu, Ru-Gun; Gau, Tsai-Sheng
2015-03-01
Aerial image measurement system (AIMSTM) has been widely used for wafer level inspection of mask defects. Reported inspection flows include die-to-die (D2D) and die-to-database (D2DB) methods. For patterns that do not repeat in another die, only the D2DB approach is applicable. The D2DB method requires accurate simulation of AIMS measurements for a mask pattern. An optical vectorial model is needed to depict the mask diffraction effect in this simulation. To accurately simulate the imaging results, a rigorous electro-magnetic field (EMF) model is essential to correctly take account of the EMF scattering induced by the mask topography, which is usually called the mask 3D effect. In this study, the mask 3D model we use is rigorous coupled-wave analysis (RCWA), which calculates the diffraction fields from a single plane wave incidence. A hybrid Hopkins-Abbe method with RCWA is used to calculate the EMF diffraction at a desired accuracy level while keeping the computation time practical. We will compare the speed of the hybrid Hopkins-Abbe method to the rigorous Abbe method. The matching between simulation and experiment is more challenging for AIMS than CD-SEM because its measurements provide full intensity information. Parameters in the mask 3D model such as film stack thickness or film optical properties, is optimized during the fitting process. We will report the fitting results of AIMS images for twodimensional structures with various pitches. By accurately simulating the AIMS measurements, it provides a necessary tool to perform the mask inspection using the D2DB approach and to accurately predict the mask defects.
Using 3D Voronoi grids in radiative transfer simulations
Camps, Peter; Saftly, Waad
2013-01-01
Probing the structure of complex astrophysical objects requires effective three-dimensional (3D) numerical simulation of the relevant radiative transfer (RT) processes. As with any numerical simulation code, the choice of an appropriate discretization is crucial. Adaptive grids with cuboidal cells such as octrees have proven very popular, however several recently introduced hydrodynamical and RT codes are based on a Voronoi tessellation of the spatial domain. Such an unstructured grid poses new challenges in laying down the rays (straight paths) needed in RT codes. We show that it is straightforward to implement accurate and efficient RT on 3D Voronoi grids. We present a method for computing straight paths between two arbitrary points through a 3D Voronoi grid in the context of a RT code. We implement such a grid in our RT code SKIRT, using the open source library Voro++ to obtain the relevant properties of the Voronoi grid cells based solely on the generating points. We compare the results obtained through t...
Application of ADER Scheme in MHD Simulation
Institute of Scientific and Technical Information of China (English)
ZHANG Yanyan; FENG Xueshang; JIANG Chaowei; ZHOU Yufen
2012-01-01
The Arbitrary accuracy Derivatives Riemann problem method（ADER） scheme is a new high order numerical scheme based on the concept of finite volume integration,and it is very easy to be extended up to any order of space and time accuracy by using a Taylor time expansion at the cell interface position.So far the approach has been applied successfully to flow mechanics problems.Our objective here is to carry out the extension of multidimensional ADER schemes to multidimensional MHD systems of conservation laws by calculating several MHD problems in one and two dimensions： （ⅰ） Brio-Wu shock tube problem,（ⅱ） Dai-Woodward shock tube problem,（ⅲ） Orszag-Tang MHD vortex problem.The numerical results prove that the ADER scheme possesses the ability to solve MHD problem,remains high order accuracy both in space and time,keeps precise in capturing the shock.Meanwhile,the compared tests show that the ADER scheme can restrain the oscillation and obtain the high order non-oscillatory result.
3D Simulation of Nano-Imprint Lithography
DEFF Research Database (Denmark)
Román Marín, José Manuel; Rasmussen, Henrik K.; Hassager, Ole
2010-01-01
A proof of concept study of the feasibility of fully three-dimensional (3D) time-dependent simulation of nano-imprint lithography of polymer melt, where the polymer is treated as a structured liquid, has been presented. Considering the flow physics of the polymer as a structured liquid, we have...... followed the line initiated by de Gennes, using a Molecular Stress Function model of the Doi and Edwards type. We have used a 3D Lagrangian Galerkin finite element methods implemented on a parallel computer architecture. In a Lagrangian techniques, the node point follows the particle movement, allowing...... for the movement of free surfaces or interfaces. We have extended the method to handle the dynamic movement of the contact line between the polymer melt and stamp during mold filling....
Relativistic MHD Simulations of Poynting Flux-Driven Jets
Guan, Xiaoyue; Li, Shengtai
2013-01-01
Relativistic, magnetized jets are observed to propagate to very large distances in many Active Galactic Nuclei (AGN). We use 3D relativistic MHD (RMHD) simulations to study the propagation of Poynting flux-driven jets in AGN. These jets are assumed already being launched from the vicinity ($\\sim 10^3$ gravitational radii) of supermassive black holes. Jet injections are characterized by a model described in Li et al. (2006) and we follow the propagation of these jets to ~ parsec scales. We find that these current-carrying jets are always collimated and mildly relativistic. When $\\alpha$, the ratio of toroidal-to-poloidal magnetic flux injection, is large the jet is subject to non-axisymmetric current-driven instabilities (CDI) which lead to substantial dissipation and reduced jet speed. However, even with the presence of instabilities, the jet is not disrupted and will continue to propagate to large distances. We suggest that the relatively weak impact by the instability is due to the nature of the instability...
Acoustic simulation in realistic 3D virtual scenes
Gozard, Patrick; Le Goff, Alain; Naz, Pierre; Cathala, Thierry; Latger, Jean
2003-09-01
The simulation workshop CHORALE developed in collaboration with OKTAL SE company for the French MoD is used by government services and industrial companies for weapon system validation and qualification trials in the infrared domain. The main operational reference for CHORALE is the assessment of the infrared guidance system of the Storm Shadow missile French version, called Scalp. The use of CHORALE workshop is now extended to the acoustic domain. The main objective is the simulation of the detection of moving vehicles in realistic 3D virtual scenes. This article briefly describes the acoustic model in CHORALE. The 3D scene is described by a set of polygons. Each polygon is characterized by its acoustic resistivity or its complex impedance. Sound sources are associated with moving vehicles and are characterized by their spectra and directivities. A microphone sensor is defined by its position, its frequency band and its sensitivity. The purpose of the acoustic simulation is to calculate the incoming acoustic pressure on microphone sensors. CHORALE is based on a generic ray tracing kernel. This kernel possesses original capabilities: computation time is nearly independent on the scene complexity, especially the number of polygons, databases are enhanced with precise physical data, special mechanisms of antialiasing have been developed that enable to manage very accurate details. The ray tracer takes into account the wave geometrical divergence and the atmospheric transmission. The sound wave refraction is simulated and rays cast in the 3D scene are curved according to air temperature gradient. Finally, sound diffraction by edges (hill, wall,...) is also taken into account.
Simulations of Gyrosynchrotron Microwave Emission from an Oscillating 3D Magnetic Loop
Kuznetsov, Alexey; Reznikova, Veronika
2015-01-01
Radio observations of solar flares often reveal various periodic or quasi-periodic oscillations. Most likely, these oscillations are caused by magnetohydrodynamic (MHD) oscillations of flaring loops which modulate the emission. Interpretation of the observations requires comparing them with simulations. We simulate the gyrosynchrotron radio emission from a semi-circular (toroidal-shaped) magnetic loop containing sausage-mode MHD oscillations. The aim is to detect the observable signatures specific to the considered MHD mode and to study their dependence on the various source parameters. The MHD waves are simulated using a linear three-dimensional model of a magnetized plasma cylinder; both standing and propagating waves are considered. The curved loop is formed by replicating the MHD solutions along the plasma cylinder and bending the cylinder; this model allows us to study the effect of varying the viewing angle along the loop. The radio emission is simulated using a three-dimensional model and its spatial a...
Broderick, Avery E
2010-01-01
For the first time it has become possible to compare global 3D general relativistic magnetohydrodynamic (GRMHD) jet formation simulations directly to very-long baseline interferometric multi-frequency polarization observations of the pc-scale structure of active galactic nucleus (AGN) jets. Unlike the jet emission, which requires post hoc modeling of the non-thermal electrons, the Faraday rotation measures (RMs) depend primarily upon simulated quantities and thus provide a robust way in which to confront simulations with observations. We compute RM distributions of 3D global GRMHD jet formation simulations, with which we explore the dependence upon model and observational parameters, emphasizing the signatures of structures generic to the theory of MHD jets. With typical parameters, we find that it is possible to reproduce the observed magnitudes and many of the structures found in AGN jet RMs, including the presence of transverse RM gradients. In our simulations the RMs are generated within a smooth extensio...
Development of Advanced Models for 3D Photocathode PIC Simulations
Dimitrov, Dimitre; Cary, John R; Feldman, Donald; Jensen, Kevin; Messmer, Peter; Stoltz, Peter
2005-01-01
Codes for simulating photocathode electron guns invariably assume the emission of an idealized electron distribution from the cathode, regardless of the particular particle emission model that is implemented. The output of such simulations, a relatively clean and smooth distribution with very little variation as a function of the azimuthal angle, is inconsistent with the highly irregular and asymmetric electron bunches seen in experimental diagnostics. To address this problem, we have implemented a recently proposed theoretical model* that takes into account detailed solid-state physics of photocathode materials in the VORPAL particle-in-cell code.** Initial results from 3D simulations with this model and future research directions will be presented and discussed.
Simulation of current generation in a 3-D plasma model
Energy Technology Data Exchange (ETDEWEB)
Tsung, F.S.; Dawson, J.M. [Univ. of California, Los Angeles, CA (United States)
1996-12-31
Two wires carrying current in the same direction will attract each other, and two wires carrying current in the opposite direction will repel each other. Now, consider a test charge in a plasma. If the test charge carries current parallel to the plasma, then it will be pulled toward the plasma core, and if the test charge carries current anti-parallel to the plasma, then it will be pushed to the edge. The electromagnetic coupling between the plasma and a test charge (i.e., the A{sub {parallel}} {circ} v{sub {parallel}} term in the test charge`s Hamiltonian) breaks the symmetry in the parallel direction, and gives rise to a diffusion coefficient which is dependent on the particle`s parallel velocity. This is the basis for the {open_quotes}preferential loss{close_quotes} mechanism described in the work by Nunan et al. In our previous 2+{1/2}D work, in both cylindrical and toroidal geometries, showed that if the plasma column is centrally fueled, then an initial current increases steadily. The results in straight, cylindrical plasmas showed that self generated parallel current arises without trapped particle or neoclassical diffusion, as assumed by the bootstrap theory. It suggests that the fundamental mechanism seems to be the conservation of particles canonical momenta in the direction of the ignorable coordinate. We have extended the simulation to 3D to verify the model put forth. A scalable 3D EM-PIC code, with a localized field-solver, has been implemented to run on a large class of parallel computers. On the 512-node SP2 at Cornell Theory Center, we have benchmarked the 2+{1/2}D calculations using 32 grids in the previously ignored direction, and a 100-fold increase in the number of particles. Our preliminary results show good agreements between the 2+{1/2}D and the 3D calculations. We will present our 3D results at the meeting.
Monserrat, Carlos; Alcaniz-Raya, Mariano L.; Juan, M. Carmen; Grau Colomer, Vincente; Albalat, Salvador E.
1997-05-01
This paper describes a new method for 3D orthodontics treatment simulation developed for an orthodontics planning system (MAGALLANES). We develop an original system for 3D capturing and reconstruction of dental anatomy that avoid use of dental casts in orthodontic treatments. Two original techniques are presented, one direct in which data are acquired directly form patient's mouth by mean of low cost 3D digitizers, and one mixed in which data are obtained by 3D digitizing of hydrocollids molds. FOr this purpose we have designed and manufactured an optimized optical measuring system based on laser structured light. We apply these 3D dental models to simulate 3D movement of teeth, including rotations, during orthodontic treatment. The proposed algorithms enable to quantify the effect of orthodontic appliance on tooth movement. The developed techniques has been integrated in a system named MAGALLANES. This original system present several tools for 3D simulation and planning of orthodontic treatments. The prototype system has been tested in several orthodontic clinic with very good results.
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...
Composite manufacturing: Simulation of 3-D resin transfer molding
Tan, Cheng Ping
1998-10-01
A technique was developed for simulating the resin transfer molding (RTM) process. The major feature of the technique is a computational steering system that enables the user to make changes during the simulation. Specifically, at any instance, the user can inspect the progress of the resin front. On the basis of the observed resin front position, the user can, as needed, change the port and vent locations, open and close ports and vents, adjust the inlet and exit pressures or flow rates, and reorient the mold with respect to the gravitational field. Additionally, the user can "rewind" the simulator to any previous time in the mold filling process, make any of the above changes and then continue the simulation. The technique is augmented by a computer code which has three main components, the Simulator, the Graphics User Interface (GUI), and the Global Data Storage. The Simulator is a finite element code that calculates the resin flow inside the fiber preform. The GUI serves as the interface between the user and the Simulator; it provides the commands to the Simulator and displays the results. The Global Data Storage is the module that manages the exchange of data between the GUI and the Simulator. The computer code (designated as SUPERTMsb-3D) is suitable for simulating the resin flow inside two-dimensional as well as three-dimensional fiber preforms of arbitrary shapes. The use of this computer code is illustrated through sample problems. These problems demonstrate how (with this code) the designer can establish the port and vent locations, opening and closing sequences of ports and vents such that the fiber preform is filled completely in the shortest time with the fewest number of vents.
3D TCAD Simulation for Semiconductor Processes, Devices and Optoelectronics
Li, Simon
2012-01-01
Technology computer-aided design, or TCAD, is critical to today’s semiconductor technology and anybody working in this industry needs to know something about TCAD. This book is about how to use computer software to manufacture and test virtually semiconductor devices in 3D. It brings to life the topic of semiconductor device physics, with a hands-on, tutorial approach that de-emphasizes abstract physics and equations and emphasizes real practice and extensive illustrations. Coverage includes a comprehensive library of devices, representing the state of the art technology, such as SuperJunction LDMOS, GaN LED devices, etc. Provides a vivid, internal view of semiconductor devices, through 3D TCAD simulation; Includes comprehensive coverage of TCAD simulations for both optic and electronic devices, from nano-scale to high-voltage high-power devices; Presents material in a hands-on, tutorial fashion so that industry practitioners will find maximum utility; Includes a comprehensive library of devices, re...
Reconciling measured scattering response of 3D metamaterials with simulation
Directory of Open Access Journals (Sweden)
Adomanis Bryan M.
2015-01-01
Full Text Available Membrane projection lithography is used to create 3-dimensional unit cells in a silicon matrix decorated with metallic inclusions. The structures show pronounced resonances in the 4–16 µm wavelength range and demonstrate direct coupling to the magnetic field of a normally incident transverse electromagnetic (TEM wave, a behavior only possible for vertically oriented resonators. Qualitative agreement between rigorous coupled wave analysis (RCWA simulation and measured scattering response is shown. COMSOL simulations show that slight variations in both metallic inclusion and silicon unit cell physical dimensions can have large impact in the scattering response, so that design for manufacture of 3D metamaterial structures for applications should be done with care.
3D numerical simulation and analysis of railgun gouging mechanism
Institute of Scientific and Technical Information of China (English)
Jin-guo WU; Bo TANG; Qing-hua LIN; Hai-yuan LI; Bao-ming LI
2016-01-01
A gouging phenomenon with a hypervelocity sliding electrical contact in railgun not only shortens the rail lifetime but also affects the interior ballistic performance. In this paper, a 3-D numerical model was introduced to simulate and analyze the generation mechanism and evolution of the rail gouging phenomenon. The results show that a rail surface bulge is an important factor to induce gouging. High density and high pressure material flow on the contact surface, obliquely extruded into the rail when accelerating the armature to a high velocity, can produce gouging. Both controlling the bulge size to a certain range and selecting suitable materials for rail surface coating will suppress the formation of gouging. The numerical simulation had a good agreement with experiments, which validated the computing model and methodology are reliable.
3-D hydrodynamic simulations of convection in A stars
Kochukhov, O; Piskunov, N; Steffen, M
2006-01-01
Broadening and asymmetry of spectral lines in slowly rotating late A-type stars provide evidence for high-amplitude convective motions. The properties of turbulence observed in the A-star atmospheres are not understood theoretically and contradict results of previous numerical simulations of convection. Here we describe an ongoing effort to understand the puzzling convection signatures of A stars with the help of 3-D hydrodynamic simulations. Our approach combines realistic spectrum synthesis and non-grey hydrodynamic models computed with the CO5BOLD code. We discuss these theoretical predictions and confront them with high-resolution spectra of A stars. Our models have, for the first time, succeeded in reproducing the observed profiles of weak spectral lines without introducing fudge broadening parameters.
3D numerical simulation and analysis of railgun gouging mechanism
Directory of Open Access Journals (Sweden)
Jin-guo Wu
2016-04-01
Full Text Available A gouging phenomenon with a hypervelocity sliding electrical contact in railgun not only shortens the rail lifetime but also affects the interior ballistic performance. In this paper, a 3-D numerical model was introduced to simulate and analyze the generation mechanism and evolution of the rail gouging phenomenon. The results show that a rail surface bulge is an important factor to induce gouging. High density and high pressure material flow on the contact surface, obliquely extruded into the rail when accelerating the armature to a high velocity, can produce gouging. Both controlling the bulge size to a certain range and selecting suitable materials for rail surface coating will suppress the formation of gouging. The numerical simulation had a good agreement with experiments, which validated the computing model and methodology are reliable.
PROPERTIES OF UMBRAL DOTS AS MEASURED FROM THE NEW SOLAR TELESCOPE DATA AND MHD SIMULATIONS
Energy Technology Data Exchange (ETDEWEB)
Kilcik, A.; Yurchyshyn, V. B.; Abramenko, V.; Goode, P. R.; Cao, W. [Big Bear Solar Observatory, Big Bear City, CA 92314 (United States); Rempel, M. [High Altitude Observatory, NCAR, Boulder, CO 80307-3000 (United States); Kitai, R.; Watanabe, H. [Kwasan and Hida Observatories, Kyoto University, Kyoto 607-8417 (Japan)
2012-02-01
We studied bright umbral dots (UDs) detected in a moderate size sunspot and compared their statistical properties to recent MHD models. The study is based on high-resolution data recorded by the New Solar Telescope at the Big Bear Solar Observatory and three-dimensional (3D) MHD simulations of sunspots. Observed UDs, living longer than 150 s, were detected and tracked in a 46 minute long data set, using an automatic detection code. A total of 1553 (620) UDs were detected in the photospheric (low chromospheric) data. Our main findings are (1) none of the analyzed UDs is precisely circular, (2) the diameter-intensity relationship only holds in bright umbral areas, and (3) UD velocities are inversely related to their lifetime. While nearly all photospheric UDs can be identified in the low chromospheric images, some small closely spaced UDs appear in the low chromosphere as a single cluster. Slow-moving and long-living UDs seem to exist in both the low chromosphere and photosphere, while fast-moving and short-living UDs are mainly detected in the photospheric images. Comparison to the 3D MHD simulations showed that both types of UDs display, on average, very similar statistical characteristics. However, (1) the average number of observed UDs per unit area is smaller than that of the model UDs, and (2) on average, the diameter of model UDs is slightly larger than that of observed ones.
Study, simulation and design of a 3D clinostat
Pavone, Valentina; Guarnieri, Vincenzo; Lobascio, Cesare; Soma, Aurelio; Bosso, Nicola; Lamantea, Matteo Maria
High cost and limited number of physically executable experiments in space have introduced the need for ground simulation systems that enable preparing experiments to be carried out on board, identifying phenomena associated with the altered gravity conditions, and taking advantage of these conditions, as in Biotechnology. Among systems developed to simulate microgravity, especially for life sciences experiments, different types of clinostats were realized. This work deals with mechanical design of a three-dimensional clinostat and simulation of the dynamic behavior of the system by varying the operating parameters. The design and simulation phase was preceded by a careful analysis of the state of art and by the review of the most recent results, in particular from the major investigators of Life Sciences in Space. The mechanical design is quite innovative by adoption of a structure entirely in aluminum, which allows robustness while reducing the overall weight. The transmission system of motion has been optimized by means of brushless DC micro motors, light and compact, which helped to reduce weight, dimensions, power consumption and increase the reliability and durability of the system. The study of the dynamic behavior using SIMPACK, a multibody simulation software, led to results in line with those found in the most important and recent scientific publications. This model was also appropriately configured to represent any desired operating condition, and for eventual system scalability. It would be interesting to generate simulated hypogravity - e.g.: 0.38-g (Mars) or 0.17-g (Moon). This would allow to investigate how terrestrial life forms can grow in other planetary habitats, or to determine the gravity threshold response of different organisms. At the moment, such a system can only be achieved by centrifuges in real microgravity. We are confident that simulation and associated tests with our 3D clinostat can help adjusting the parameters allowing variable g
3D Simulation Modeling of the Tooth Wear Process.
Dai, Ning; Hu, Jian; Liu, Hao
2015-01-01
Severe tooth wear is the most common non-caries dental disease, and it can seriously affect oral health. Studying the tooth wear process is time-consuming and difficult, and technological tools are frequently lacking. This paper presents a novel method of digital simulation modeling that represents a new way to study tooth wear. First, a feature extraction algorithm is used to obtain anatomical feature points of the tooth without attrition. Second, after the alignment of non-attrition areas, the initial homogeneous surface is generated by means of the RBF (Radial Basic Function) implicit surface and then deformed to the final homogeneous by the contraction and bounding algorithm. Finally, the method of bilinear interpolation based on Laplacian coordinates between tooth with attrition and without attrition is used to inversely reconstruct the sequence of changes of the 3D tooth morphology during gradual tooth wear process. This method can also be used to generate a process simulation of nonlinear tooth wear by means of fitting an attrition curve to the statistical data of attrition index in a certain region. The effectiveness and efficiency of the attrition simulation algorithm are verified through experimental simulation.
3D Simulation Modeling of the Tooth Wear Process.
Directory of Open Access Journals (Sweden)
Ning Dai
Full Text Available Severe tooth wear is the most common non-caries dental disease, and it can seriously affect oral health. Studying the tooth wear process is time-consuming and difficult, and technological tools are frequently lacking. This paper presents a novel method of digital simulation modeling that represents a new way to study tooth wear. First, a feature extraction algorithm is used to obtain anatomical feature points of the tooth without attrition. Second, after the alignment of non-attrition areas, the initial homogeneous surface is generated by means of the RBF (Radial Basic Function implicit surface and then deformed to the final homogeneous by the contraction and bounding algorithm. Finally, the method of bilinear interpolation based on Laplacian coordinates between tooth with attrition and without attrition is used to inversely reconstruct the sequence of changes of the 3D tooth morphology during gradual tooth wear process. This method can also be used to generate a process simulation of nonlinear tooth wear by means of fitting an attrition curve to the statistical data of attrition index in a certain region. The effectiveness and efficiency of the attrition simulation algorithm are verified through experimental simulation.
Global and Kinetic MHD Simulation by the Gpic-MHD Code
Institute of Scientific and Technical Information of China (English)
Hiroshi NAITOU; Yusuke YAMADA; Kenji KAJIWARA; Wei-li LEE; Shinji TOKUDA; Masatoshi YAGI
2011-01-01
In order to implement large-scale and high-beta tokamak simulation, a new algorithm of the electromagnetic gyrokinetic PIC （particle-in-cell） code was proposed and installed on the Gpic-MHD code [Gyrokinetic PIC code for magnetohydrodynamic （MHD） simulation]. In the new algorithm, the vorticity equation and the generalized Ohm＇s law along the magnetic field are derived from the basic equations of the gyrokinetic Vlasov, Poisson, and Ampere system and are used to describe the spatio-temporal evolution of the field quantities of the electrostatic potential φ and the longitudinal component of the vector potential Az. The basic algorithm is equivalent to solving the reduced-MHD-type equations with kinetic corrections, in which MHD physics related to Alfven modes are well described. The estimation of perturbed electron pressure from particle dynamics is dominant, while the effects of other moments are negligible. Another advantage of the algorithm is that the longitudinal induced electric field, ETz = -δAz/δt, is explicitly estimated by the generalized Ohm＇s law and used in the equations of motion. Furthermore, the particle velocities along the magnetic field are used （vz-formulation） instead of generalized momentums （pz-formulation）, hence there is no problem of ＇cancellation＇, which would otherwise appear when Az is estimated from the Ampere＇s law in the pz-formulation. The successful simulation of the collisionless internal kink mode by the new Gpic-MHD with realistic values of the large-scale and high-beta tokamaks revealed the usefulness of the new algorithm.
Validation of 3D simulations of reverse osmosis membrane biofouling.
Pintelon, Thomas R R; Creber, Sarah A; von der Schulenburg, Daniel A Graf; Johns, Michael L
2010-07-01
The increasing demand for drinking water and its stricter quality requirements have resulted in an exponentially expanding industry of membrane filtration processes. Currently, reverse osmosis (RO) is the most common method of desalination, able to produce water that is virtually free of pollutants and pathogenic micro-organisms. Biofouling of these devices however is a significant limitation. Here we present a 3D simulation of RO membrane biofouling based on a lattice Boltzmann (LB) platform that we subsequently favorably compare with experimental data. This data consists of temporally (and spatially) resolved velocity measurements acquired for a RO membrane using magnetic resonance techniques. The effect of biofilm cohesive strength on system pressure drop is then explored; weaker biomass is observed to have a reduced impact on pressure drop (per unit biomass accumulated).
3D Simulations of Galactic Winds in Dwarf Galaxies
Marcolini, A; D'Ercole, A; Marcolini, Andrea; Brighenti, Fabrizio; Ercole, Annibale D'
2002-01-01
We present 3D hydrodynamical simulations of galactic winds in dwarf, gas-rich galaxies. The galaxy is moving through the ICM of a small galaxy group at v=200 km/s. The ram pressure removes the galactic gas at large radii, but does not strongly influence the ISM near the center. A starburst generates a galactic wind. The newly produced metals are expelled in the ICM and carried to large distance from the galaxy by the ram pressure. 500 Myr after the starburst only a few percent of the heavy elements produced are present in the central region of the dwarf galaxy. A large collection of ram pressure + wind models will be presented in a forthcoming paper.
3D-Simulation Studies of SNS Ring Doublet Magnets
Energy Technology Data Exchange (ETDEWEB)
Wang, J.G.; Tsoupas N.; Venturini, M.
2005-05-05
The accumulator ring of the Spallation Neutron Source (SNS) at ORNL employs in its straight sections closely packed quadrupole doublemagnets with large aperture of R=15.1 cm an relatively short iron-to-iron distance of 51.4 cm. These quads have much extended fringe field, and magnetic interferences among them in the doublet assemblies is not avoidable. Though each magnet in the assemblies has been individually mapped to high accuracy of lower than 0.01 percent level, the experimental data including the magnetic interference effect will not be available. We have performed 3D computing simulations on a quadrupole doublet model in order to assess the degree of the interference and to obtain relevant data for the SNS commissioning and operation.
Lattice Boltzmann Large Eddy Simulation Model of MHD
Flint, Christopher
2016-01-01
The work of Ansumali \\textit{et al.}\\cite{Ansumali} is extended to Two Dimensional Magnetohydrodynamic (MHD) turbulence in which energy is cascaded to small spatial scales and thus requires subgrid modeling. Applying large eddy simulation (LES) modeling of the macroscopic fluid equations results in the need to apply ad-hoc closure schemes. LES is applied to a suitable mesoscopic lattice Boltzmann representation from which one can recover the MHD equations in the long wavelength, long time scale Chapman-Enskog limit (i.e., the Knudsen limit). Thus on first performing filter width expansions on the lattice Boltzmann equations followed by the standard small Knudsen expansion on the filtered lattice Boltzmann system results in a closed set of MHD turbulence equations provided we enforce the physical constraint that the subgrid effects first enter the dynamics at the transport time scales. In particular, a multi-time relaxation collision operator is considered for the density distribution function and a single rel...
3D Hydrodynamic Simulations of Carbon Burning in Massive Stars
Cristini, Andrea; Hirschi, Raphael; Arnett, David; Georgy, Cyril; Viallet, Maxime
2016-01-01
We present the first detailed three-dimensional (3D) hydrodynamic implicit large eddy simulations of turbulent convection of carbon burning in massive stars. The simulations start with initial radial profiles mapped from a carbon burning shell within a 15$\\,\\textrm{M}_\\odot$ 1D stellar evolution model. We consider 4 resolutions from $128^3$ to $1024^3$ zones. The turbulent flow properties of these carbon burning simulations are very similar to the oxygen burning case. We performed a mean field analysis of the kinetic energy budgets within the Reynolds-averaged Navier-Stokes framework. For the upper convective boundary region, we find that the inferred numerical dissipation is insensitive to resolution for linear mesh resolutions between 512 and 1,024 grid points. For the stiffer and more stratified lower boundary, our highest resolution model still shows signs of decreasing dissipation suggesting that it is not yet fully resolved numerically. We estimate the widths of the upper and lower boundaries to be roug...
Wiehle, S.; Plaschke, F.; Motschmann, U.; Glassmeier, K. H.; Auster, H. U.; Angelopoulos, V.; Mueller, J.; Kriegel, H.; Georgescu, E.; Halekas, J.; Sibeck, D. G.; McFadden, J. P.
2011-01-01
The spacecraft P1 of the new ARTEMIS (Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon's Interaction with the Sun) mission passed the lunar wake for the first time on February 13, 2010. We present magnetic field and plasma data of this event and results of 3D hybrid simulations. As the solar wind magnetic field was highly dynamic during the passage, a simulation with stationary solar wind input cannot distinguish whether distortions were caused by these solar wind variations or by the lunar wake; therefore, a dynamic real-time simulation of the flyby has been performed. The input values of this simulation are taken from NASA OMNI data and adapted to the P1 data, resulting in a good agreement between simulation and measurements. Combined with the stationary simulation showing non-transient lunar wake structures, a separation of solar wind and wake effects is achieved. An anisotropy in the magnitude of the plasma bulk flow velocity caused by a non-vanishing magnetic field component parallel to the solar wind flow and perturbations created by counterstreaming ions in the lunar wake are observed in data and simulations. The simulations help to interpret the data granting us the opportunity to examine the entire lunar plasma environment and, thus, extending the possibilities of measurements alone: A comparison of a simulation cross section to theoretical predictions of MHD wave propagation shows that all three basic MHD modes are present in the lunar wake and that their expansion governs the lunar wake refilling process.
Alignment of Velocity and Magnetic Fluctuations in Simulations of Anisotropic MHD Turbulence
Ng, C. S.; Bhattacharjee, A.
2007-11-01
There has been recent theoretical interest in the effect of the alignment of velocity and magnetic fluctuations in three-dimensional (3D) MHD turbulence with a large-scale magnetic field [Boldyrev 2005, 2006]. This theory predicts that the angle θ between the velocity and magnetic fluctuation vectors has a scaling of θ&1/4circ;, where λ is the spatial scale of the fluctuations. There have also been simulations on 3D forced MHD turbulence that supports this prediction [Mason et al. 2006, 2007]. The scaling has also been tested against observations of solar wind turbulence [Podesta et al. 2007]. We report here simulation results based on decaying 2D turbulence. The scaling of θ&1/4circ; and Iroshnikov-Kraichnan scaling has also been observed within a range of time interval and spatial scales, despite the fact that Boldyrev's theory was developed for fully 3D turbulence in the presence of a strong external field. As the external field is reduced in magnitude and becomes comparable to the magnitude of magnetic fluctuations or lower, the scale-dependent alignment is weakened. Implications for observations of solar wind turbulence will be discussed.
3D mapping and simulation of Geneva Lake environmental data
Villard, Roch; Maignan, Michel; Kanevski, Mikhail; Rapin, Francois; Klein, Audrey
2010-05-01
The Geneva Lake is the biggest alpine and subalpine lake in central Europe. The depth of this lake is 309 meters and its total volume of water is 89 billions m3. It takes, on average, around twelve years so that waters of the lake are completely brewed. Furthermore the Geneva lake waters are rich in dissolved substances as carbonate, sulfate. The quantity of particles in suspension in the lake, which mainly arrived from the Rhône, is nowadays around height million of tones. The International Commission for the Leman Lake (CIPEL) works about the improvement of the quality of this lake since 1962. In the present study three dimensional environmental data (temperature, oxygen and nitrate) which cover the period from 1954 to 2008, for a total of 27'500 cases are investigated. We are interested to study the evolution of the temperature of the lake because there is an impact on the reproduction of fishes and also because the winter brewing of the water makes the re-oxygenation of deep-water. In order that biological balance is maintained in a lake, there must be enough oxygen in the water. Moreover, we work on nitrate distribution and evolution because contributions in fertilizers cause eutrophication of lake. The data are very numerous when we consider the time series, some of them with more than 300 occurrences, but there are between 2 and 15 data available for spatial cartography. The basic methodology used for the analysis, mapping and simulations of 3D patterns of environmental data is based on geostatistical predictions (family of kriging models) and conditional stochastic simulations. Spatial and temporal variability, 3D monitoring networks changing over time, make this study challenging. An important problem is also to make interpolation/simulations over a long period of time, like ten years. One way used to overcome this problem, consists in using a weighted average of ten variograms during this period. 3D mapping was carried out using environment data for
Plasma environment of Titan: a 3-D hybrid simulation study
Directory of Open Access Journals (Sweden)
S. Simon
2006-05-01
Full Text Available Titan possesses a dense atmosphere, consisting mainly of molecular nitrogen. Titan's orbit is located within the Saturnian magnetosphere most of the time, where the corotating plasma flow is super-Alfvénic, yet subsonic and submagnetosonic. Since Titan does not possess a significant intrinsic magnetic field, the incident plasma interacts directly with the atmosphere and ionosphere. Due to the characteristic length scales of the interaction region being comparable to the ion gyroradii in the vicinity of Titan, magnetohydrodynamic models can only offer a rough description of Titan's interaction with the corotating magnetospheric plasma flow. For this reason, Titan's plasma environment has been studied by using a 3-D hybrid simulation code, treating the electrons as a massless, charge-neutralizing fluid, whereas a completely kinetic approach is used to cover ion dynamics. The calculations are performed on a curvilinear simulation grid which is adapted to the spherical geometry of the obstacle. In the model, Titan's dayside ionosphere is mainly generated by solar UV radiation; hence, the local ion production rate depends on the solar zenith angle. Because the Titan interaction features the possibility of having the densest ionosphere located on a face not aligned with the ram flow of the magnetospheric plasma, a variety of different scenarios can be studied. The simulations show the formation of a strong magnetic draping pattern and an extended pick-up region, being highly asymmetric with respect to the direction of the convective electric field. In general, the mechanism giving rise to these structures exhibits similarities to the interaction of the ionospheres of Mars and Venus with the supersonic solar wind. The simulation results are in agreement with data from recent Cassini flybys.
Jiang, Chaowei; Wu, S T; Hu, Qiang
2012-01-01
We apply a data-driven MHD model to investigate the three-dimensional (3D) magnetic field of NOAA active region (AR) 11117 around the time of a C-class confined flare occurred on 2010 October 25. The MHD model, based on the spacetime conservation-element and solution-element (CESE) scheme, is designed to focus on the magnetic-field evolution and to consider a simplified solar atomsphere with finite plasma $\\beta$. Magnetic vector-field data derived from the observations at the photoshpere is inputted directly to constrain the model. Assuming that the dynamic evolution of the coronal magnetic field can be approximated by successive equilibria, we solve a time sequence of MHD equilibria basing on a set of vector magnetograms for AR 11117 taken by the Helioseismic and Magnetic Imager (HMI) on board the {\\it Solar Dynamic Observatory (SDO)} around the time of flare. The model qualitatively reproduces the basic structures of the 3D magnetic field, as supported by the visual similarity between the field lines and t...
3D two-fluid simulations of turbulence in LAPD
Fisher, Dustin M.
The Large Plasma Device (LAPD) is modeled using a modified version of the 3D Global Braginskii Solver code (GBS) for a nominal Helium plasma. The unbiased low-flow regime is explored in simulations where there is an intrinsic E x B rotation of the plasma. In the simulations this rotation is caused primarily by sheath effects with the Reynolds stress and J x B torque due to a cross-field Pederson conductivity having little effect. Explicit biasing simulations are also explored for the first time where the intrinsic rotation of the plasma is modified through boundary conditions that mimic the biasable limiter used in LAPD. Comparisons to experimental measurements in the unbiased case show strong qualitative agreement with the data, particularly the radial dependence of the density fluctuations, cross-correlation lengths, radial flux dependence outside of the cathode edge, and camera imagery. Kelvin Helmholtz (KH) turbulence at relatively large scales is the dominant driver of cross-field transport in these simulations with smaller-scale drift waves and sheath modes playing a secondary role. Plasma holes and blobs arising from KH vortices are consistent with the scale sizes and overall appearance of those in LAPD camera images. The addition of ion-neutral collisions in the unbiased simulations at previously theorized values reduces the radial particle flux due to a modest stabilizing contribution of the collisions on the KH-modes driving the turbulent transport. In the biased runs the ion-neutral collisions have a much smaller effect due to the modification of the potential from sheath terms. In biasing the plasma to increase the intrinsic rotation, simulations show the emergence of a nonlinearly saturated coherent mode of order m = 6. In addition, the plasma inside of the cathode edge becomes quiescent due to the strong influence of the wall bias in setting up the equilibrium plasma potential. Biasing in the direction opposite to the intrinsic flow reduces the
Direct numerical simulations of helical dynamo action: MHD and beyond
Directory of Open Access Journals (Sweden)
D. O. Gómez
2004-01-01
Full Text Available Magnetohydrodynamic dynamo action is often invoked to explain the existence of magnetic fields in several astronomical objects. In this work, we present direct numerical simulations of MHD helical dynamos, to study the exponential growth and saturation of magnetic fields. Simulations are made within the framework of incompressible flows and using periodic boundary conditions. The statistical properties of the flow are studied, and it is found that its helicity displays strong spatial fluctuations. Regions with large kinetic helicity are also strongly concentrated in space, forming elongated structures. In dynamo simulations using these flows, we found that the growth rate and the saturation level of magnetic energy and magnetic helicity reach an asymptotic value as the Reynolds number is increased. Finally, extensions of the MHD theory to include kinetic effects relevant in astrophysical environments are discussed.
EVIDENCE OF ACTIVE MHD INSTABILITY IN EULAG-MHD SIMULATIONS OF SOLAR CONVECTION
Energy Technology Data Exchange (ETDEWEB)
Lawson, Nicolas; Strugarek, Antoine; Charbonneau, Paul, E-mail: nicolas.laws@gmail.ca, E-mail: strugarek@astro.umontreal.ca, E-mail: paulchar@astro.umontreal.ca [Département de Physique, Université de Montréal, C.P. 6128 Succ. Centre-ville, Montréal, Qc H3C 3J7 (Canada)
2015-11-10
We investigate the possible development of magnetohydrodynamical instabilities in the EULAG-MHD “millennium simulation” of Passos and Charbonneau. This simulation sustains a large-scale magnetic cycle characterized by solar-like polarity reversals taking place on a regular multidecadal cadence, and in which zonally oriented bands of strong magnetic fields accumulate below the convective layers, in response to turbulent pumping from above in successive magnetic half-cycles. Key aspects of this simulation include low numerical dissipation and a strongly sub-adiabatic fluid layer underlying the convectively unstable layers corresponding to the modeled solar convection zone. These properties are conducive to the growth and development of two-dimensional instabilities that are otherwise suppressed by stronger dissipation. We find evidence for the action of a non-axisymmetric magnetoshear instability operating in the upper portions of the stably stratified fluid layers. We also investigate the possibility that the Tayler instability may be contributing to the destabilization of the large-scale axisymmetric magnetic component at high latitudes. On the basis of our analyses, we propose a global dynamo scenario whereby the magnetic cycle is driven primarily by turbulent dynamo action in the convecting layers, but MHD instabilities accelerate the dissipation of the magnetic field pumped down into the overshoot and stable layers, thus perhaps significantly influencing the magnetic cycle period. Support for this scenario is found in the distinct global dynamo behaviors observed in an otherwise identical EULAG-MHD simulations, using a different degree of sub-adiabaticity in the stable fluid layers underlying the convection zone.
3-D simulation of posterior fossa reduction in Chiari I
Directory of Open Access Journals (Sweden)
Yvens Barbosa Fernandes
2016-05-01
Full Text Available ABSTRACT We proposed a 3D model to evaluate the role of platybasia and clivus length in the development of Chiari I (CI. Using a computer aided design software, two DICOM files of a normal CT scan and MR were used to simulate different clivus lengths (CL and also different basal angles (BA. The final posterior fossa volume (PFV was obtained for each variation and the percentage of the volumetric change was acquired with the same method. The initial normal values of CL and BA were 35.65 mm and 112.66º respectively, with a total PFV of 209 ml. Ranging the CL from 34.65 to 29.65 – 24.65 – 19.65, there was a PFV decrease of 0.47% – 1.12% – 1.69%, respectively. Ranging the BA from 122.66º to 127.66º – 142.66º, the PFV decreased 0.69% – 3.23%, respectively. Our model highlights the importance of the basal angle and clivus length to the development of CI.
Simulated Photoevaporative Mass Loss from Hot Jupiters in 3D
Tripathi, Anjali; Murray-Clay, Ruth A; Krumholz, Mark R
2015-01-01
Ionizing stellar photons heat the upper regions of planetary atmospheres, driving atmospheric mass loss. Gas escaping from several hot, hydrogen-rich planets has been detected using UV and X-ray transmission spectroscopy. Because these planets are tidally locked, and thus asymmetrically irradiated, escaping gas is unlikely to be spherically symmetric. In this paper, we focus on the effects of asymmetric heating on local outflow structure. We use the Athena code for hydrodynamics to produce 3D simulations of hot Jupiter mass loss that jointly model wind launching and stellar heating via photoionization. Our fiducial planet is an inflated, hot Jupiter with radius $R_p=2.14 R_{\\rm Jup}$ and mass $M_p = 0.53 M_{\\rm Jup}$. We irradiate the initially neutral, atomic hydrogen atmosphere with 13.6 eV photons and compute the outflow's ionization structure. There are clear asymmetries in the atmospheric outflow, including a neutral shadow on the planet's nightside. Given an incident ionizing UV flux comparable to that ...
3D hybrid simulations with gyrokinetic particle ions and fluid electrons
Energy Technology Data Exchange (ETDEWEB)
Belova, E.V.; Park, W.; Fu, G.Y. [Princeton Univ., NJ (United States). Plasma Physics Lab.; Strauss, H.R. [New York Univ., NY (United States); Sugiyama, L.E. [Massachusetts Inst. of Tech., Cambridge, MA (United States)
1998-12-31
The previous hybrid MHD/particle model (MH3D-K code) represented energetic ions as gyrokinetic (or drift-kinetic) particles coupled to MHD equations using the pressure or current coupling scheme. A small energetic to bulk ion density ratio was assumed, n{sub h}/n{sub b} {much_lt} 1, allowing the neglect of the energetic ion perpendicular inertia in the momentum equation and the use of MHD Ohm`s law E = {minus}v{sub b} {times} B. A generalization of this model in which all ions are treated as gyrokinetic/drift-kinetic particles and fluid description is used for the electron dynamics is considered in this paper.
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.
3-D numerical simulations of volcanic ash transport and deposition
Suzuki, Y. J.; Koyaguchi, T.
2012-12-01
During an explosive volcanic eruption, volcanic gas and pyroclasts are ejected from the volcanic vent. The pyroclasts are carried up within a convective plume, advected by the surrounding wind field, and sediment on the ground depending on their terminal velocity. The fine ash are expected to have atmospheric residence, whereas the coarser particles form fall deposits. Accurate modeling of particle transport and deposition is of critical importance from the viewpoint of disaster prevention. Previously, some particle-tracking models (e.g., PUFF) and advection-diffusion models (e.g., TEPHRA2 and FALL3D) tried to forecast particle concentration in the atmosphere and particle loading at ground level. However, these models assumed source conditions (the grain-size distribution, plume height, and mass release location) based on the simple 1-D model of convective plume. In this study, we aim to develop a new 3-D model which reproduces both of the dynamics of convective plume and the ash transport. The model is designed to describe the injection of eruption cloud and marker particles from a circular vent above a flat surface into the stratified atmosphere. Because the advection is the predominant mechanism of particle transport near the volcano, the diffusive process is not taken into account in this model. The distribution of wind velocity is given as an initial condition. The model of the eruption cloud dynamics is based on the 3-D time-dependent model of Suzuki et al. (2005). We apply a pseudo-gas model to calculate the eruption cloud dynamics: the effect of particle separation on the cloud dynamics is not considered. In order to reproduce the drastic change of eruption cloud density, we change the effective gas constant and heat capacity of the mixture in the equation of state for ideal gases with the mixing ratio between the ejected material and entrained air. In order to calculate the location and movement of ash particles, the present model employs Lagrangian marker
One year in the Earth's magnetosphere: A global MHD simulation and spacecraft measurements
Facsko, G; Zivkovic, T; Palin, L; Kallio, E; Agren, K; Opgenoorth, H; Tanskanen, E I; Milan, S E
2016-01-01
The response of the Earth's magnetosphere to changing solar wind conditions are studied with a 3D Magnetohydrodynamic (MHD) model. One full year (155 Cluster orbits) of the Earth's magnetosphere is simulated using Grand Unified Magnetosphere Ionosphere Coupling simulation (GUMICS-4) magnetohydrodynamic code. Real solar wind measurements are given to the code as input to create the longest lasting global magnetohydrodynamics simulation to date. The applicability of the results of the simulation depends critically on the input parameters used in the model. Therefore, the validity and the variance of the OMNIWeb data is first investigated thoroughly using Cluster measurement close to the bow shock. The OMNIWeb and the Cluster data were found to correlate very well before the bow shock. The solar wind magnetic field and plasma parameters are not changed significantly from the $L_1$ Lagrange point to the foreshock, therefore the OMNIWeb data is appropriate input to the GUMICS-4. The Cluster SC3 footprints are dete...
GMC Collisions as Triggers of Star Formation. II. 3D Turbulent, Magnetized Simulations
Wu, Benjamin; Tan, Jonathan C.; Nakamura, Fumitaka; Van Loo, Sven; Christie, Duncan; Collins, David
2017-02-01
We investigate giant molecular cloud collisions and their ability to induce gravitational instability and thus star formation. This mechanism may be a major driver of star formation activity in galactic disks. We carry out a series of 3D, magnetohydrodynamics (MHD), adaptive mesh refinement simulations to study how cloud collisions trigger formation of dense filaments and clumps. Heating and cooling functions are implemented based on photo-dissociation region models that span the atomic-to-molecular transition and can return detailed diagnostic information. The clouds are initialized with supersonic turbulence and a range of magnetic field strengths and orientations. Collisions at various velocities and impact parameters are investigated. Comparing and contrasting colliding and non-colliding cases, we characterize morphologies of dense gas, magnetic field structure, cloud kinematic signatures, and cloud dynamics. We present key observational diagnostics of cloud collisions, especially: relative orientations between magnetic fields and density structures, like filaments; 13CO(J = 2-1), 13CO(J = 3-2), and 12CO(J = 8-7) integrated intensity maps and spectra; and cloud virial parameters. We compare these results to observed Galactic clouds.
3D Simulations of Helmet Streamer Dynamics and Implications for the Slow Solar Wind
Higginson, Aleida K.; Antiochos, Spiro K.; DeVore, C. R.; Zurbuchen, Thomas H.
2015-04-01
The source of the slow solar wind at the Sun is still an issue of intense debate in solar and heliospheric physics. Because the majority of the solar wind observed at Earth is slow wind, understanding its origin is essential for understanding and predicting Earth’s space weather environment. In-situ and remote observations show that, when compared to the fast wind, the slow solar wind corresponds to higher freeze-in temperatures, as indicated by charge-state ratios, and more corona-like elemental abundance ratios. These results indicate that the most likely source for the slow wind is the hot plasma in the closed-field corona, but the release mechanism(s) for the wind from the closed-field regions is far from understood. We perform fully dynamic, 3D MHD simulations in order to the study the opening and closing of the Sun’s magnetic field that leads to the escape of the slow solar wind. In particular, we calculate the dynamics of helmet streamers that are driven by photospheric motions such as supergranular flows. We determine in detail the opening and closing of coronal flux, and discuss the implications of our results for theories of slow wind origin, especially the S-Web model. We also determine observational signatures for the upcoming inner heliosphere missions Solar Orbiter and Solar Probe Plus.This work was supported by the NASA SR&T and TR&T Programs.
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.
Simulations of MHD flows with moving interfaces
Gerbeau, J F; Le Bris, C
2003-01-01
We report on the numerical simulation of a two-fluid magnetohydrodynamics problem arising in the industrial production of aluminium. The motion of the two non-miscible fluids is modeled through the incompressible Navier-Stokes equations coupled with the Maxwell equations. Stabilized finite elements techniques and an arbitrary Lagrangian-Eulerian formulation (for the motion of the interface separating the two fluids) are used in the numerical simulation. With a view to justifying our strategy, details on the numerical analysis of the problem, with a special emphasis on conservation and stability properties and on the surface tension discretization, as well as results on tests cases are provided. Examples of numerical simulations of the industrial case are eventually presented.
Divergence-free MHD Simulations with the HERACLES Code
Directory of Open Access Journals (Sweden)
Vides J.
2013-12-01
Full Text Available Numerical simulations of the magnetohydrodynamics (MHD equations have played a significant role in plasma research over the years. The need of obtaining physical and stable solutions to these equations has led to the development of several schemes, all requiring to satisfy and preserve the divergence constraint of the magnetic field numerically. In this paper, we aim to show the importance of maintaining this constraint numerically. We investigate in particular the hyperbolic divergence cleaning technique applied to the ideal MHD equations on a collocated grid and compare it to the constrained transport technique that uses a staggered grid to maintain the property. The methods are implemented in the software HERACLES and several numerical tests are presented, where the robustness and accuracy of the different schemes can be directly compared.
3D Rigorous simulation of mask induced polarization
Wei, X.; Urbach, H.P.; Wachters, A.; Aksenov, Y.
2005-01-01
The polarization induced by the mask is studied by using a 3D rigorous model, wich solves Maxwell equations using the finite element method. Teh aerial image depends strongly on the change of polarization induced by the materials, thickness of the layer and pitch of the periodic masks.
Kitiashvili, I N; Goode, P R; Kosovichev, A G; Lele, S K; Mansour, N N; Wray, A A; Yurchyshyn, V B
2012-01-01
Turbulent properties of the quiet Sun represent the basic state of surface conditions, and a background for various processes of solar activity. Therefore understanding of properties and dynamics of this `basic' state is important for investigation of more complex phenomena, formation and development of observed phenomena in the photosphere and atmosphere. For characterization of the turbulent properties we compare kinetic energy spectra on granular and sub-granular scales obtained from infrared TiO observations with the New Solar Telescope (Big Bear Solar Observatory) and from 3D radiative MHD numerical simulations ('SolarBox' code). We find that the numerical simulations require a high spatial resolution with 10 - 25 km grid-step in order to reproduce the inertial (Kolmogorov) turbulence range. The observational data require an averaging procedure to remove noise and potential instrumental artifacts. The resulting kinetic energy spectra show a good agreement between the simulations and observations, opening...
Angular Momentum Transport by Acoustic Modes Generated in the Boundary Layer II: MHD Simulations
Belyaev, Mikhail A; Stone, James M
2013-01-01
We perform global unstratified 3D magnetohydrodynamic simulations of an astrophysical boundary layer (BL) -- an interface region between an accretion disk and a weakly magnetized accreting object such as a white dwarf -- with the goal of understanding the effects of magnetic field on the BL. We use cylindrical coordinates with an isothermal equation of state and investigate a number of initial field geometries including toroidal, vertical, and vertical with zero net flux. Our initial setup consists of a Keplerian disk attached to a non-rotating star. In a previous work, we found that in hydrodynamical simulations, sound waves excited by shear in the BL were able to efficiently transport angular momentum and drive mass accretion onto the star. Here we confirm that in MHD simulations, waves serve as an efficient means of angular momentum transport in the vicinity of the BL, despite the magnetorotational instability (MRI) operating in the disk. In particular, the angular momentum current due to waves is at times...
Ju, Wenhua; Zhu, Zhaohuan
2016-01-01
We present results from the first global 3D MHD simulations of accretion disks in Cataclysmic Variable (CV) systems in order to investigate the relative importance of angular momentum transport via turbulence driven by the magnetorotational instability (MRI) compared to that driven by spiral shock waves. Remarkably, we find that even with vigorous MRI turbulence, spiral shocks are an important component to the overall angular momentum budget, at least when temperatures in the disk are high (so that Mach numbers are low). In order to understand the excitation, propagation, and damping of spiral density waves in our simulations more carefully, we perform a series of 2D global hydrodynamical simulations with various equation of states and both with and without mass inflow via the Lagrangian point (L1). Compared with previous similar studies, we find the following new results. 1) Linear wave dispersion relation fits the pitch angles of spiral density waves very well. 2) We demonstrate explicitly that mass accreti...
Interdisciplinary Collaboration through Designing 3D Simulation Case Studies
Bai, Xin; 10.5121/ijma.2011.3109
2011-01-01
Interdisciplinary collaboration is essential for the advance of research. As domain subjects become more and more specialized, researchers need to cross disciplines for insights from peers in other areas to have a broader and deeper understand of a topic at micro- and macro-levels. We developed a 3D virtual learning environment that served as a platform for faculty to plan curriculum, share educational beliefs, and conduct cross-discipline research for effective learning. Based upon the scripts designed by faculty from five disciplines, virtual doctors, nurses, or patients interact in a 3D virtual hospital. The teaching vignettes were then converted to video clips, allowing users to view, pause, replay, or comment on the videos individually or in groups. Unlike many existing platforms, we anticipated a value-added by adding a social networking capacity to this virtual environment. The focus of this paper is on the cost-efficiency and system design of the virtual learning environment.
Interdisciplinary Collaboration through Designing 3D Simulation Case Studies
Directory of Open Access Journals (Sweden)
Xin Bai
2011-02-01
Full Text Available Interdisciplinary collaboration is essential for the advance of research. As domain subjects become more and more specialized, researchers need to cross disciplines for insights from peers in other areas to have a broader and deeper understand of a topic at micro- and macro-levels. We developed a 3D virtual learning environment that served as a platform for faculty to plan curriculum, share educational beliefs,and conduct cross-discipline research for effective learning. Based upon the scripts designed by facultyfrom five disciplines, virtual doctors, nurses, or patients interact in a 3D virtual hospital. The teaching vignettes were then converted to video clips, allowing users to view, pause, replay, or comment on the videos individually or in groups. Unlike many existing platforms, we anticipated a value-added by adding a social networking capacity to this virtual environment. The focus of this paper is on the cost-efficiency and system design of the virtual learning environment.
Interdisciplinary Collaboration through Designing 3D Simulation Case Studies
Directory of Open Access Journals (Sweden)
Xin Bai
2011-02-01
Full Text Available Interdisciplinary collaboration is essential for the advance of research. As domain subjects become more and more specialized, researchers need to cross disciplines for insights from peers in other areas to have a broader and deeper understand of a topic at micro- and macro-levels. We developed a 3D virtual learning environment that served as a platform for faculty to plan curriculum, share educational beliefs, and conduct cross-discipline research for effective learning. Based upon the scripts designed by faculty from five disciplines, virtual doctors, nurses, or patients interact in a 3D virtual hospital. The teaching vignettes were then converted to video clips, allowing users to view, pause, replay, or comment on the videos individually or in groups. Unlike many existing platforms, we anticipated a value-added by adding a social networking capacity to this virtual environment. The focus of this paper is on the cost-efficiency and system design of the virtual learning environment.
DREAM3D simulations of inner-belt dynamics
Energy Technology Data Exchange (ETDEWEB)
Cunningham, Gregory Scott [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2015-05-26
A 1973 paper by Lyons and Thorne explains the two-belt structure for electrons in the inner magnetosphere as a balance between inward radial diffusion and loss to the atmosphere, where the loss to the atmosphere is enabled by pitch-angle scattering from Coulomb and wave-particle interactions. In the 1973 paper, equilibrium solutions to a decoupled set of 1D radial diffusion equations, one for each value of the first invariant of motion, μ, were computed to produce the equilibrium two-belt structure. Each 1D radial diffusion equation incorporated an L-and μ-dependent `lifetime' due to the Coulomb and wave-particle interactions. This decoupling of the problem is appropriate under the assumption that radial diffusion is slow in comparison to pitch-angle scattering. However, for some values of μ and L the lifetime associated with pitch-angle scattering is comparable to the timescale associated with radial diffusion, suggesting that the true equilibrium solutions might reflect `coupled modes' involving pitch-angle scattering and radial diffusion and thus requiring a 3D diffusion model. In the work we show here, we have computed the equilibrium solutions using our 3D diffusion model, DREAM3D, that allows for such coupling. We find that the 3D equilibrium solutions are quite similar to the solutions shown in the 1973 paper when we use the same physical models for radial diffusion and pitch-angle scattering from hiss. However, we show that the equilibrium solutions are quite sensitive to various aspects of the physics model employed in the 1973 paper that can be improved, suggesting that additional work needs to be done to understand the two-belt structure.
Using 3-D Numerical Weather Data in Piloted Simulations
Daniels, Taumi S.
2016-01-01
This report describes the process of acquiring and using 3-D numerical model weather data sets in NASA Langley's Research Flight Deck (RFD). A set of software tools implement the process and can be used for other purposes as well. Given time and location information of a weather phenomenon of interest, the user can download associated numerical weather model data. These data are created by the National Oceanic and Atmospheric Administration (NOAA) High Resolution Rapid Refresh (HRRR) model, and are then processed using a set of Mathworks' Matlab(TradeMark) scripts to create the usable 3-D weather data sets. Each data set includes radar re ectivity, water vapor, component winds, temperature, supercooled liquid water, turbulence, pressure, altitude, land elevation, relative humidity, and water phases. An open-source data processing program, wgrib2, is available from NOAA online, and is used along with Matlab scripts. These scripts are described with sucient detail to make future modi cations. These software tools have been used to generate 3-D weather data for various RFD experiments.
3d particle simulations on ultra short laser interaction
Energy Technology Data Exchange (ETDEWEB)
Nishihara, Katsunobu; Okamoto, Takashi; Yasui, Hidekazu [Osaka Univ., Suita (Japan). Inst. of Laser Engineering
1998-03-01
Two topics related to ultra short laser interaction with matter, linear and nonlinear high frequency conductivity of a solid density hydrogen plasma and anisotropic self-focusing of an intense laser in an overdense plasma, have been investigated with the use of 3-d particle codes. Frequency dependence of linear conductivity in a dense plasma is obtained, which shows anomalous conductivity near plasma frequency. Since nonlinear conductivity decreases with v{sub o}{sup -3}, where v{sub o} is a quivering velocity, an optimum amplitude exists leading to a maximum electron heating. Anisotropic self-focusing of a linear polarized intense laser is observed in an overdense plasma. (author)
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.
3D Numerical Simulation of Projectile Penetration into Concrete Target
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
Basing on the explicit instantaneous dynamics software MSC-Dytran and the general coupling arithmetic, the process of the projectile penetration into concrete target was simulated with the point-line-surface-body modeling method. Simulation results are in agreement with experimental results. The simulated data could provide design reference for the defense engineering construction and penetrator design.
Mesh Resolution Effect on 3D RANS Turbomachinery Flow Simulations
Yershov, Sergiy
2016-01-01
The paper presents the study of the effect of a mesh refinement on numerical results of 3D RANS computations of turbomachinery flows. The CFD solver F, which based on the second-order accurate ENO scheme, is used in this study. The simplified multigrid algorithm and local time stepping permit decreasing computational time. The flow computations are performed for a number of turbine and compressor cascades and stages. In all flow cases, the successively refined meshes of H-type with an approximate orthogonalization near the solid walls were generated. The results obtained are compared in order to estimate their both mesh convergence and ability to resolve the transonic flow pattern. It is concluded that for thorough studying the fine phenomena of the 3D turbomachinery flows, it makes sense to use the computational meshes with the number of cells from several millions up to several hundred millions per a single turbomachinery blade channel, while for industrial computations, a mesh of about or less than one mil...
Parallel Simulation of 3-D Turbulent Flow Through Hydraulic Machinery
Institute of Scientific and Technical Information of China (English)
徐宇; 吴玉林
2003-01-01
Parallel calculational methods were used to analyze incompressible turbulent flow through hydraulic machinery. Two parallel methods were used to simulate the complex flow field. The space decomposition method divides the computational domain into several sub-ranges. Parallel discrete event simulation divides the whole task into several parts according to their functions. The simulation results were compared with the serial simulation results and particle image velocimetry (PIV) experimental results. The results give the distribution and configuration of the complex vortices and illustrate the effectiveness of the parallel algorithms for numerical simulation of turbulent flows.
Rezania, Vahid; Tuszynski, Jack
2016-01-01
In this paper, we develop a spatio-temporal modeling approach to describe blood and drug flow, as well as drug uptake and elimination, on an approximation of the liver. Extending on previously developed computational approaches, we generate an approximation of a liver, which consists of a portal and hepatic vein vasculature structure, embedded in the surrounding liver tissue. The vasculature is generated via constrained constructive optimization, and then converted to a spatial grid of a selected grid size. Estimates for surrounding upscaled lobule tissue properties are then presented appropriate to the same grid size. Simulation of fluid flow and drug metabolism (hepatic clearance) are completed using discretized forms of the relevant convective-diffusive-reactive partial differential equations for these processes. This results in a single stage, uniformly consistent method to simulate equations for blood and drug flow, as well as drug metabolism, on a 3D structure representative of a liver. PMID:27649537
Numerical Simulation of Effective Properties of 3D Piezoelectric Composites
Directory of Open Access Journals (Sweden)
Ri-Song Qin
2014-01-01
Full Text Available The prediction of the overall effective properties of fibre-reinforced piezocomposites has drawn much interest from investigators recently. In this work, an algorithm used in two-dimensional (2D analysis for calculating transversely isotropic material properties is developed. Since the finite element (FE meshing patterns on the opposite areas are the same, constraint equations can be applied directly to generate appropriate load. The numerical results derived using this model have found a good agreement with those in the literature. The 2D algorithm is then modified and improved in such a way that it is valid for three-dimensional (3D analysis in the case of random distributed shorts and inclusions. Linear interpolation of displacement field is employed to establish constraint equations of nodal displacements between two adjacent elements.
Assessment of the CATHARE 3-D module for LBLOCA simulation
Energy Technology Data Exchange (ETDEWEB)
Pascal Bazin; Isabelle Dor; Christophe Morel [Commissariat a l' Energie Atomique, CEA - GRENOBLE, 17 rue des Martyrs, 38054 GRENOBLE cedex 9 (France)
2005-07-01
Full text of publication follows: CATHARE is a best-estimate system code developed by CEA, EDF, FRAMATOME-ANP and IRSN for PWR safety analysis, accident management, definition of plant operating procedure and for research and development. It is also used to quantify conservative margins and for licensing. In the framework of Pressurized Water Reactor (PWR) safety studies, Large Break Loss-Of-Coolant Accident (LB LOCA) prediction is still one of the most important and one of the most difficult problem. The three main phases of a LB LOCA are respectively the blowdown, the refilling and the reflooding phases. During the blowdown, the lower plenum voiding results in water entrainment towards the break by steam flowing from the core. Because of the core radial profile, critical heat flux occur but a nonuniform quenching may take place, which results in a 3-D repartition of the energy stored in the core at the beginning of the reflooding. The refilling phase which starts at the accumulator discharge encounters very complex thermalhydraulic phenomena: very strong condensation which induces instabilities, presence of nitrogen degassing from accumulator water which may have an important effect on the transient, countercurrent flow limitation which occurs in the complex geometry of the annular downcomer. The reflooding phase initial conditions in the core are therefore very non-uniform. The presence of buoyancy driven transverse flows below the quench front assures a very efficient mixing between the fuel assemblies. The quench front progression in the hot assemblies is accelerated by pre-cooling due to water cross-flows just above the quench front. Therefore the clad temperature excursion is moderated in the hot assemblies by an increased water carry-over coming partially from colder assemblies. All these multi-dimensional aspects create a very challenging problem for the CATHARE 3-D module. A good prediction of the lower plenum voiding altogether with the amount of
3D FEM Simulations of a shape rolling process
Wisselink, H.H.; Huetink, J.; Dijk, van M.H.H.; Leeuwen, van A.J.
2001-01-01
A finite element model has been developed for the simulation of the shape rolling of stator vanes. These simulations should support the design of rolling tools for new vane types. For the time being only straight vanes (vanes with a constant cross-section over the length) are studied. In that case t
On the characterization of magnetic reconnection in global MHD simulations
Directory of Open Access Journals (Sweden)
T. V. Laitinen
2006-11-01
Full Text Available The conventional definition of reconnection rate as the electric field parallel to an x-line is problematic in global MHD simulations for several reasons: the x-line itself may be hard to find in a non-trivial geometry such as at the magnetopause, and the lack of realistic resistivity modelling leaves us without reliable non-convective electric field. In this article we describe reconnection characterization methods that avoid those problems and are practical to apply in global MHD simulations. We propose that the reconnection separator line can be identified as the region where magnetic field lines of different topological properties meet, rather than by local considerations. The global convection associated with reconnection is then quantified by calculating the transfer of mass, energy or magnetic field across the boundary of closed and open field line regions. The extent of the diffusion region is determined from the destruction of electromagnetic energy, given by the divergence of the Poynting vector. Integrals of this energy conversion provide a way to estimate the total reconnection efficiency.
3D Radiation Nonideal Magnetohydrodynamical Simulations of the Inner Rim in Protoplanetary Disks
Flock, M.; Fromang, S.; Turner, N. J.; Benisty, M.
2017-02-01
Many planets orbit within 1 au of their stars, raising questions about their origins. Particularly puzzling are the planets found near the silicate sublimation front. We investigate conditions near the front in the protostellar disk around a young intermediate-mass star, using the first global 3D radiation nonideal MHD simulations in this context. We treat the starlight heating; the silicate grains’ sublimation and deposition at the local, time-varying temperature and density; temperature-dependent ohmic dissipation; and various initial magnetic fields. The results show magnetorotational turbulence around the sublimation front at 0.5 au. The disk interior to 0.8 au is turbulent, with velocities exceeding 10% of the sound speed. Beyond 0.8 au is the dead zone, cooler than 1000 K and with turbulence orders of magnitude weaker. A local pressure maximum just inside the dead zone concentrates solid particles, favoring their growth. Over many orbits, a vortex develops at the dead zone’s inner edge, increasing the disk’s thickness locally by around 10%. We synthetically observe the results using Monte Carlo transfer calculations, finding that the sublimation front is near-infrared bright. The models with net vertical magnetic fields develop extended, magnetically supported atmospheres that reprocess extra starlight, raising the near-infrared flux 20%. The vortex throws a nonaxisymmetric shadow on the outer disk. At wavelengths > 2 μ {{m}}, the flux varies several percent on monthly timescales. The variations are more regular when the vortex is present. The vortex is directly visible as an arc at ultraviolet through near-infrared wavelengths, given sub-au spatial resolution.
FLASH MHD simulations of experiments that study shock-generated magnetic fields
Tzeferacos, P.; Fatenejad, M.; Flocke, N.; Graziani, C.; Gregori, G.; Lamb, D. Q.; Lee, D.; Meinecke, J.; Scopatz, A.; Weide, K.
2015-12-01
We summarize recent additions and improvements to the high energy density physics capabilities in FLASH, highlighting new non-ideal magneto-hydrodynamic (MHD) capabilities. We then describe 3D Cartesian and 2D cylindrical FLASH MHD simulations that have helped to design and analyze experiments conducted at the Vulcan laser facility. In these experiments, a laser illuminates a carbon rod target placed in a gas-filled chamber. A magnetic field diagnostic (called a Bdot) employing three very small induction coils is used to measure all three components of the magnetic field at a chosen point in space. The simulations have revealed that many fascinating physical processes occur in the experiments. These include megagauss magnetic fields generated by the interaction of the laser with the target via the Biermann battery mechanism, which are advected outward by the vaporized target material but decrease in strength due to expansion and resistivity; magnetic fields generated by an outward expanding shock via the Biermann battery mechanism; and a breakout shock that overtakes the first wave, the contact discontinuity between the target material and the gas, and then the initial expanding shock. Finally, we discuss the validation and predictive science we have done for this experiment with FLASH.
Single-sided sheet-to-tube spot welding investigated by 3D numerical simulations
DEFF Research Database (Denmark)
Nielsen, Chris Valentin; Chergui, Azeddine; Zhang, Wenqi
The single-sided resistance spot welding process is analyzed by a 3D numerical study of sheet-to-tube joining. Finite element simulations are carried out in SORPAS® 3D. Two levels of electrode force and five levels of welding current are simulated. The overall effects of changing current and force...
Simple 3-D stimulus for motion parallax and its simulation.
Ono, Hiroshi; Chornenkyy, Yevgen; D'Amour, Sarah
2013-01-01
Simulation of a given stimulus situation should produce the same perception as the original. Rogers et al (2009 Perception 38 907-911) simulated Wheeler's (1982, PhD thesis, Rutgers University, NJ) motion parallax stimulus and obtained quite different perceptions. Wheeler's observers were unable to reliably report the correct direction of depth, whereas Rogers's were. With three experiments we explored the possible reasons for the discrepancy. Our results suggest that Rogers was able to see depth from the simulation partly due to his experience seeing depth with random dot surfaces.
3D Modeling and Simulation of Dendritic Growth during Solidification
Institute of Scientific and Technical Information of China (English)
Zuojian LIANG; Qingyan XU; Baicheng LIU
2003-01-01
A mathematical model for the three-dimensional simulation of free dendritic growth and microstructure evolutionwas developed based on the growth mechanism of crystal grains and basic transfer equations such as heat, massand momentum transfer equations. Ma
Simulations of Gyrosynchrotron Microwave Emission from an Oscillating 3D Magnetic Loop
Kuznetsov, A. A.; Van Doorsselaere, T.; Reznikova, V. E.
2015-04-01
Radio observations of solar flares often reveal various periodic or quasi-periodic oscillations. Most likely, these oscillations are caused by magnetohydrodynamic (MHD) oscillations of flaring loops which modulate the emission. Interpreting the observations requires comparing them with simulations. We simulated the gyrosynchrotron radio emission from a semicircular (toroidal-shaped) magnetic loop containing sausage-mode MHD oscillations. The aim was to detect the observable signatures specific to the considered MHD mode and to study their dependence on the various source parameters. The MHD waves were simulated using a linear three-dimensional model of a magnetized plasma cylinder; both standing and propagating waves were considered. The curved loop was formed by replicating the MHD solutions along the plasma cylinder and bending the cylinder; this model allowed us to study the effect of varying the viewing angle along the loop. The radio emission was simulated using a three-dimensional model, and its spatial and temporal variations were analyzed. We considered several loop orientations and different parameters of the magnetic field, plasma, and energetic electrons in the loop. In the model with low plasma density, the intensity oscillations at all frequencies are synchronous (with the exception of a narrow spectral region below the spectral peak). In the model with high plasma density, the emission at low frequencies (where the Razin effect is important) oscillates in anti-phase with the emissions at higher frequencies. The oscillations at high and low frequencies are more pronounced in different parts of the loop (depending on the loop orientation). The layers where the line-of-sight component of the magnetic field changes sign can produce additional peculiarities in the oscillation patterns.
MHD Simulations of Core Collapse Supernovae with Cosmos++
Akiyama, Shizuka
2010-01-01
We performed 2D, axisymmetric, MHD simulations with Cosmos++ in order to examine the growth of the magnetorotational instability (MRI) in core--collapse supernovae. We have initialized a non--rotating 15 solar mass progenitor, infused with differential rotation and poloidal magnetic fields. The collapse of the iron core is simulated with the Shen EOS, and the parametric Ye and entropy evolution. The wavelength of the unstable mode in the post--collapse environment is expected to be only ~ 200 m. In order to achieve the fine spatial resolution requirement, we employed remapping technique after the iron core has collapsed and bounced. The MRI unstable region appears near the equator and angular momentum and entropy are transported outward. Higher resolution remap run display more vigorous overturns and stronger transport of angular momentum and entropy. Our results are in agreement with the earlier work by Akiyama et al. (2003) and Obergaulinger et al. (2009).
SIERRA - A 3-D device simulator for reliability modeling
Chern, Jue-Hsien; Arledge, Lawrence A., Jr.; Yang, Ping; Maeda, John T.
1989-05-01
SIERRA is a three-dimensional general-purpose semiconductor-device simulation program which serves as a foundation for investigating integrated-circuit (IC) device and reliability issues. This program solves the Poisson and continuity equations in silicon under dc, transient, and small-signal conditions. Executing on a vector/parallel minisupercomputer, SIERRA utilizes a matrix solver which uses an incomplete LU (ILU) preconditioned conjugate gradient square (CGS, BCG) method. The ILU-CGS method provides a good compromise between memory size and convergence rate. The authors have observed a 5x to 7x speedup over standard direct methods in simulations of transient problems containing highly coupled Poisson and continuity equations such as those found in reliability-oriented simulations. The application of SIERRA to parasitic CMOS latchup and dynamic random-access memory single-event-upset studies is described.
3D Simulations of methane convective storms on Titan's atmosphere
Hueso, R.; Sánchez-Lavega, A.
2005-08-01
The arrival of the Cassini/Huygens mission to Titan has opened an unprecedented opportunity to study the atmosphere of this satellite. Under the pressure-temperature conditions on Titan, methane, a large atmospheric component amounting perhaps to a 3-5% of the atmosphere, is close to its triple point, potentially playing a similar role as water on Earth. The Huygens probe has shown a terrain shaped by erosion of probably liquid origin, suggestive of past rain. On the other hand, Voyager IRIS spectroscopic observations of Titan imply a saturated atmosphere of methane (amounting perhaps to 150 covered by methane clouds, if we think on Earth meteorology. However, observations from Earth and Cassini have shown that clouds are localized, transient and fast evolving, in particular in the South Pole (currently in its summer season). This might imply a lack of widespread presence on Titan of nuclei where methane could initiate condensation and particle growth with subsequent precipitation. We investigate different scenarios of moist convective storms on Titan using a complete 3D atmospheric model that incorporates a full microphysics treatment required to study cloud formation processes under a saturated atmosphere with low concentration of condensation nuclei. We study local convective development under a variety of atmospheric conditions: sub-saturation, super-saturation, abundances of condensation nuclei fall, condensation nuclei lifted from the ground or gently falling from the stratosphere. We show that under the appropriate circumstances, precipitation rates comparable to typical tropical storms on Earth can be found. Acknowledgements: This work has been funded by Spanish MCYT PNAYA2003-03216, fondos FEDER and Grupos UPV 15946/2004. R. Hueso acknowledges a post-doc fellowship from Gobierno Vasco.
Humanoid Robot 3 -D Motion Simulation for Hardware Realization
Institute of Scientific and Technical Information of China (English)
CAO Xi; ZHAO Qun-fei; MA Pei-sun
2007-01-01
In this paper, three dimensions kinematics andkinetics simulation arc discussed for hardware realization ofa physical biped walking-chair robot. The direct and inverseclose-form kinematics solution of the biped walking-chairis deduced. Several gaits are realized with thekinematics solution, including walking straight on levelfloor, going up stair, squatting down and standing up. ZeroMoment Point(ZMP) equation is analyzed considering themovement of the crew. The simulated biped walking-chairrobot is used for mechanical design, gaits development andvalidation before they are tested on real robot.
Bai, Xue-Ning
2014-01-01
We perform 3D stratified shearing-box MHD simulations on the gas dynamics of protoplanetary disks threaded by net vertical magnetic field Bz. All three non-ideal MHD effects, Ohmic resistivity, the Hall effect and ambipolar diffusion are included in a self-consistent manner based on equilibrium chemistry. We focus on regions toward outer disk radii, from 5-60AU, where Ohmic resistivity tends to become negligible, ambipolar diffusion dominates over an extended region across disk height, and the Hall effect largely controls the dynamics near the disk midplane. We find that around R=5AU, the system launches a laminar/weakly turbulent magnetocentrifugal wind when the net vertical field Bz is not too weak, as expected. Moreover, the wind is able to achieve and maintain a configuration with reflection symmetry at disk midplane. The case with anti-aligned field polarity (Omega. Bz<0) is more susceptible to the MRI when Bz drops, leading to an outflow oscillating in radial directions and very inefficient angular m...
Self-organisation in protoplanetary disks: global, non-stratified Hall-MHD simulations
Béthune, William; Ferreira, Jonathan
2016-01-01
Recent observations revealed organised structures in protoplanetary disks, such as axisymmetric rings or horseshoe concen- trations evocative of large-scale vortices. These structures are often interpreted as the result of planet-disc interactions. However, these disks are also known to be unstable to the magneto-rotational instability (MRI) which is believed to be one of the dominant angular momentum transport mechanism in these objects. It is therefore natural to ask if the MRI itself could produce these structures without invoking planets. The nonlinear evolution of the MRI is strongly affected by the low ionisation fraction in protoplanetary disks. The Hall effect in particular, which is dominant in dense and weakly ionised parts of these objects, has been shown to spontaneously drive self- organising flows in shearing box simulations. Here, we investigate the behaviour of global MRI-unstable disc models dominated by the Hall effect and characterise their dynamics. We perform 3D unstratified Hall-MHD simu...
Cheung, M. C.; Schüssler, M.; Moreno-Insertis, F.; Tarbell, T. D.
2007-12-01
With high angular resolution, high temporal cadence and a stable point spread function, the Solar Optical Telescope (SOT) onboard the Hinode satellite is the ideal instrument for the study of magnetic flux emergence and its manifestations on the solar surface. In this presentation, we focus on the development of ephemeral regions and small active regions. In many instances, SOT has been able to capture the entire emergence process from beginning to end: i.e. from the initial stages of flux appearance in granule interiors, through the intermediate stages of G-band bright point formation, and finally to the coalescence of small vertical flux elements to form pores. To investigate the physics of the flux emergence process, we performed 3D numerical MHD simulations with the MURaM code. The models are able to reproduce, and help us explain, various observational signatures of magnetic flux emergence.
Simulation of 3D-CRT treatment for lung cancer
Energy Technology Data Exchange (ETDEWEB)
Thalhofer, Jardel L.; Silva, Ademir X. da; Junior, Juraci R.P., E-mail: jardellt@yahoo.com.br [Coordenacao dos Programas de Pos-Graduacao de Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil); Rebello, Wilson F., E-mail: rebello@ime.eb.br [Instituto Militar de Engenharia (IME), Rio de Janeiro, RJ (Brazil). Secao de Engenharia Nuclear; Correa, Samanda C.A., E-mail: samandacristine@uezo.rj.gov.br [Comissao Nacional de Energia Nuclear (CNEN), Rio de Janeiro, RJ (Brazil); Souza, Edmilson M., E-mail: emonteiro@nuclear.ufrj.br [Centro Universitario da Zona Oeste (UEZO), Rio de Janeiro, RJ (Brazil). Colegiado de Comutacao e Matematica; Batista, Delano V.S., E-mail: delano@inca.gov.br [Instituto Nacional de Cancer (INCA), Rio de Janeiro, RJ (Brazil)
2013-07-01
In radiotherapy treatment for lung cancer, occurs doses deposition in healthy organs. During the treatment planning are calculated some doses due to photons. This dose deposition in healthy organs could induce to the appearance of new cancers foci. The aim of this study was to analyze the equivalent doses in healthy organs of a patient treated by radiotherapy for lung cancer. In order to calculate the doses, was done a computer simulation of radiotherapy treatment for lung cancer, adopting database of the treatment performed by INCA. To perform the simulation was used several tools, among them, the radiation transport code MCNPX, in which was shaped the radiotherapy room and the head from the linear accelerator Varian 2300 C / D, the patient was simulated by Voxel male phantom in Rex,and the treatment protocol adopted considers a beam with energy of 6 MV focusing on three gantry tilt angles (0 deg, 180 deg and 45 deg). In addition, there was variation in the opening of the radiation field according to the angle of inclination. The results of this study point to the organs close to the irradiated area are predominantly affected by the dose due to photons, affecting organs from different body systems, such as esophagus, heart, thymus, spine and lymph nodes. The calculated values demonstrating that the angle of 0 deg was the most responsible for the deposit of unwanted dose. The results showed that the simulations in this paper is developed in accordance with the planning data described in different studies and literature. (author)
3D COMPOSITIONAL RESERVOIR SIMULATION IN CONJUNCTION WITH UNSTRUCTURED GRIDS
Directory of Open Access Journals (Sweden)
A. L. S. Araújo
Full Text Available Abstract In the last decade, unstructured grids have been a very important step in the development of petroleum reservoir simulators. In fact, the so-called third generation simulators are based on Perpendicular Bisection (PEBI unstructured grids. Nevertheless, the use of PEBI grids is not very general when full anisotropic reservoirs are modeled. Another possibility is the use of the Element based Finite Volume Method (EbFVM. This approach has been tested for several reservoir types and in principle has no limitation in application. In this paper, we implement this approach in an in-house simulator called UTCOMP using four element types: hexahedron, tetrahedron, prism, and pyramid. UTCOMP is a compositional, multiphase/multi-component simulator based on an Implicit Pressure Explicit Composition (IMPEC approach designed to handle several hydrocarbon recovery processes. All properties, except permeability and porosity, are evaluated in each grid vertex. In this work, four case studies were selected to evaluate the implementation, two of them involving irregular geometries. Results are shown in terms of oil and gas rates and saturated gas field.
Final Report: "Large-Eddy Simulation of Anisotropic MHD Turbulence"
Energy Technology Data Exchange (ETDEWEB)
Zikanov, Oleg
2008-06-23
To acquire better understanding of turbulence in flows of liquid metals and other electrically conducting fluids in the presence of steady magnetic fields and to develop an accurate and physically adequate LES (large-eddy simulation) model for such flows. The scientific objectives formulated in the project proposal have been fully completed. Several new directions were initiated and advanced in the course of work. Particular achievements include a detailed study of transformation of turbulence caused by the imposed magnetic field, development of an LES model that accurately reproduces this transformation, and solution of several fundamental questions of the interaction between the magnetic field and fluid flows. Eight papers have been published in respected peer-reviewed journals, with two more papers currently undergoing review, and one in preparation for submission. A post-doctoral researcher and a graduate student have been trained in the areas of MHD, turbulence research, and computational methods. Close collaboration ties have been established with the MHD research centers in Germany and Belgium.
Microbial Enhanced Oil Recovery: 3D Simulation with Gravity Effects
DEFF Research Database (Denmark)
Nielsen, Sidsel Marie; Jessen, K.; Shapiro, Alexander
2010-01-01
implemented our MEOR model into a compositional streamline simulator based on the standard IMPEC framework (implicit pressure, explicit composition) to decouple flow and reactive transport. The reaction and transport processes are solved simultaneously along each streamline. Gravity effects are implemented......, with all the relevant physical processes included. We have developed a mathematical model describing the process of MEOR, where reactive transport is combined with a simple compositional approach. The model describes the displacement of oil by water containing bacteria, substrate, and the produced...
Formation and collimation of relativistic MHD jets - simulations and radio maps
Fendt, Christian; Sheikhnezami, Somayeh
2013-01-01
We present results of magnetohydrodynamic (MHD) simulations of jet formation and propagation, discussing a variety of astrophysical setups. In the first approach we consider simulations of relativistic MHD jet formation, considering jets launched from the surface of a Keplerian disk, demonstrating numerically - for the first time - the self-collimating ability of relativistic MHD jets. We obtain Lorentz factors up to about 10 while acquiring a high degree of collimation of about 1 degree. We then present synchrotron maps calculated from the intrinsic jet structure derived from the MHD jet formation simulation. We finally present (non-relativistic) MHD simulations of jet lauching, treating the transition between accretion and ejection. These setups include a physical magnetic diffusivity which is essential for loading the accretion material onto the outflow. We find relatively high mass fluxes in the outflow, of the order of 20-40 % of the accretion rate.
Photorealistic 3D omni-directional stereo simulator
Reiners, Dirk; Cruz-Neira, Carolina; Neumann, Carsten
2015-03-01
While a lot of areas in VR have made significant advances, visual rendering in VR is often not quite keeping up with the state of the art. There are many reasons for this, but one way to alleviate some of the issues is by using ray tracing instead of rasterization for image generation. Contrary to popular belief, ray tracing is a realistic, competitive technology nowadays. This paper looks at the pros and cons of using ray tracing and demonstrates the feasibility of employing it using the example of a helicopter flight simulator image generator.
3D General Relativistic Simulations of Coalescing Binary Neutron Stars
Oohara, K I; Nakamura, Takashi; Oohara, Ken-ichi
1999-01-01
We develop a 3 dimensional computer code to study a coalescing neutron star binary. The code can currently follow the evolution up to two stars begin to merge from two spherical stars of mass 1 solar mass and radius 8.9km with separation 35.4km. As for coordinate conditions, we use conformal slicing and pseudo-minimal distortion conditions. The evolution equations for the metric is integrated using the CIP method while the van Leer's scheme is used to integrate the equations for the matter. We present a few results of our simulations including gravitational radiation.
Kanki, Takashi; Nagata, Masayoshi; Kagei, Yasuhiro
2011-10-01
The dynamics of structures of magnetic field, current density, and plasma flow generated during multi-pulsed coaxial helicity injection in spherical torus is investigated by 3-D nonlinear MHD simulations. During the driven phase, the flux and current amplifications occur due to the merging and magnetic reconnection between the preexisting plasma in the confinement region and the ejected plasma from the gun region involving the n = 1 helical kink distortion of the central open flux column (COFC). Interestingly, the diamagnetic poloidal flow which tends toward the gun region is then observed due to the steep pressure gradients of the COFC generated by ohmic heating through an injection current winding around the inboard field lines, resulting in the formation of the strong poloidal flow shear at the interface between the COFC and the core region. This result is consistent with the flow shear observed in the HIST. During the decay phase, the configuration approaches the axisymmetric MHD equilibrium state without flow because of the dissipation of magnetic fluctuation energy to increase the closed flux surfaces, suggesting the generation of ordered magnetic field structure. The parallel current density λ concentrated in the COFC then diffuses to the core region so as to reduce the gradient in λ, relaxing in the direction of the Taylor state.
3D Simulation of a Medium scale Pool Fire
Directory of Open Access Journals (Sweden)
Naveen S
2014-04-01
Full Text Available Pool fires represent the most frequently encountered accidents of the different types of fires that are known to occur in the Chemical Process Industry (CPI. Exhaustive analysis of the history of past accidents in CPI's that have occurred across the world since early 1900's reveal that pool fires are major threats to industrial safety, and result in huge losses of life and property. Studies have been going on to study the interaction mechanisms of the fire and models have been developed which were mostly empirical, zone models and field models developed according to and based on the conditions available for the experiment. The experiment considered consisted of a 2-m-diameter methanol pool in an unconfined area with a cross-wind velocity of 13 m/s. Steady state simulations with uniform time step were done using computational fluid dynamics and the simulations showed sensitivity to the grid refinement, size of the pool and wind profiles.Comparison between calculated and experimental results are also made.Turbulence models were also investigated, and was observed that RNG model gave more predictable results for the test cases to the accuracy of almost 80%.
Plasma boundaries at Mars: a 3-D simulation study
Directory of Open Access Journals (Sweden)
A. Bößwetter
2004-12-01
Full Text Available The interaction of the solar wind with the ionosphere of planet Mars is studied using a three-dimensional hybrid model. Mars has only a weak intrinsic magnetic field, and consequently its ionosphere is directly affected by the solar wind. The gyroradii of the solar wind protons are in the range of several hundred kilometers and therefore comparable with the characteristic scales of the interaction region. Different boundaries emerge from the interaction of the solar wind with the continuously produced ionospheric heavy-ion plasma, which could be identified as a bow shock (BS, ion composition boundary (ICB and magnetic pile up boundary (MPB, where the latter both turn out to coincide. The simulation results regarding the shape and position of these boundaries are in good agreement with the measurements made by Phobos-2 and MGS spacecraft. It is shown that the positions of these boundaries depend essentially on the ionospheric production rate, the solar wind ram pressure, and the often unconsidered electron temperature of the ionospheric heavy ion plasma. Other consequences are rays of planetary plasma in the tail and heavy ion plasma clouds, which are stripped off from the dayside ICB region by some instability.
Key words. Magnetospheric physics (solar wind interactions with unmagnetized bodies – Space plasma physics (discontinuities; numerical simulation studies
A 3-d simulation of the atmospheric neutrinos
Favier, Jean; Vialle, J P
2003-01-01
The first AMS flight in June 1998 on board of the space shuttle Discovery at an altitude of approximately 380 km unveiled unexpected features of the cosmic rays spectra below the Earth geomagnetic cut-off. In addition to a secondary flux of particles at all latitude, a ring of high energy particles (up to 6 GeV) and an anomalous ratio e+/e- as high as 4 was observed near the geomagnetic equator. This paper describes a simulation of the interaction of primary cosmic rays with atmosphere in which the effect of the Earth magnetic field is included . Using the GEANT3 package for the tracking of particles with the GFLUKA associated package for the physics of interactions, this simulation reproduces quite well the AMS experimental results and the CAPRICE muon data at ground level. The predictions of this model for the flux of atmospheric neutrino are compared with the Super-Kamiokande results and with the results of other atmospheric neutrino models.
3D Computational Simulation of Calcium Leaching in Cement Matrices
Directory of Open Access Journals (Sweden)
Gaitero, J. J.
2014-12-01
Full Text Available Calcium leaching is a degradation process consisting in progressive dissolution of the cement paste by migration of calcium atoms to the aggressive solution. It is therefore, a complex phenomenon involving several phases and dissolution and diffusion processes simultaneously. Along this work, a new computational scheme for the simulation of the degradation process in three dimensions was developed and tested. The toolkit was used to simulate accelerated calcium leaching by a 6M ammonium nitrate solution in cement matrices. The obtained outputs were the three dimensional representation of the matrix and the physicochemical properties of individual phases as a consequence of the degradation process. This not only makes it possible to study the evolution of such properties as a function of time but also as a function of the position within the matrix. The obtained results are in good agreement with experimental values of the elastic modulus in degraded and undegraded samples.El lixiviado de calcio es un proceso de degradación consistente en la disolución progresiva de la pasta de cemento por la migración de los átomos de calcio a la disolución agresiva. Se trata por tanto de un fenómeno complejo que involucra simultáneamente diferentes fases y procesos de disolución y difusión. En este trabajo se desarrolló y probó una nueva herramienta computacional para la simulación del proceso de degradación en tres dimensiones. Para ello se simuló el lixiviado de calcio acelerado provocado por una disolución de nitrato amónico 6M en matrices de cemento. Como resultado se obtuvieron la representación tridimensional de la matriz y las propiedades físico-químicas sus fases a lo largo del tiempo. Esto permitió estudiar la evolución de dichas propiedades a lo largo del proceso de degradación así como en función de su posición dentro de la matriz. Los resultados obtenidos coinciden con los valores experimentales del módulo elástico tanto
Development of 3D beam-beam simulation for the Tevatron
Energy Technology Data Exchange (ETDEWEB)
Stern, E.; Amundson, J.; Spentzouris, P.; Valishev, A.; /Fermilab; Qiang, J.; Ryne, R.; /LBL, Berkeley
2007-06-01
We present status of development of a 3D Beam-Beam simulation code for simulating the Fermilab Tevatron collider. The essential features of the code are 3D particle-in-cell Poisson solver for calculating the Beam-Beam electromagnetic interactions with additional modules for linear optics, machine impedance and chromaticity, and multiple bunch tracking. The simulations match synchrobetatron oscillations measured at the VEPP-2M collider. The impedance calculations show beam instability development consistent with analytic expressions.
Simulation of Fully Nonlinear 3-D Numerical Wave Tank
Institute of Scientific and Technical Information of China (English)
张晓兔; 滕斌; 宁德志
2004-01-01
A fully nonlinear numerical wave tank (NWT) has been simulated by use of a three-dimensional higher order boundary element method (HOBEM) in the time domain. Within the frame of potential flow and the adoption of simply Rankine source, the resulting boundary integral equation is repeatedly solved at each time step and the fully nonlinear free surface boundary conditions are integrated with time to update its position and boundary values. A smooth technique is also adopted in order to eliminate the possible saw-tooth numerical instabilities. The incident wave at the uptank is given as theoretical wave in this paper. The outgoing waves are absorbed inside a damping zone by spatially varying artificial damping on the free surface at the wave tank end. The numerical results show that the NWT developed by these approaches has a high accuracy and good numerical stability.
MHD Remote Numerical Simulations: Evolution of Coronal Mass Ejections
Hernandez-Cervantes, L; Gonzalez-Ponce, A R
2008-01-01
Coronal mass ejections (CMEs) are solar eruptions into interplanetary space of as much as a few billion tons of plasma, with embedded magnetic fields from the Sun's corona. These perturbations play a very important role in solar--terrestrial relations, in particular in the spaceweather. In this work we present some preliminary results of the software development at the Universidad Nacional Autonoma de Mexico to perform Remote MHD Numerical Simulations. This is done to study the evolution of the CMEs in the interplanetary medium through a Web-based interface and the results are store into a database. The new astrophysical computational tool is called the Mexican Virtual Solar Observatory (MVSO) and is aimed to create theoretical models that may be helpful in the interpretation of observational solar data.
3D Design & Simulation of Printed Dipole Antenna
Directory of Open Access Journals (Sweden)
Protap Mollick
2015-09-01
Full Text Available This paper represents design of a printed dipole antenna with both lambda by 2 & half dipole. In this research paper the impedance increases with combined design on the FR-4 substrate and ground plane. The main feature of printed dipole antenna is there is a feeder between the radiant elements. Average impedance about 73 ohm, which is very large form other antenna. For vertical earth position impedance decreases about 36 ohm. Applied AC voltage forwarding bias dipole antenna gains are high but when reverse bias condition gains are low. Between ropes to station there is need extra insulator that abate high impedance current flow to dipole antenna. Feed lines are approximately 75 ohm and the main length between two poles are 143 meter. The radius of two pole line is very thin it’s about 2.06 meter. Transmission lines are added in the last portion of feed lines, which situated apposite of two poles. Designs are simulated by hfss and solving equations are done my matlab.
Fajardo, Kristel C Meza; Chaillat, Stéphanie; Lenti, Luca
2016-01-01
In this work, we study seismic wave amplification in alluvial basins having 3D standard geometries through the Fast Multipole Boundary Element Method in the frequency domain. We investigate how much 3D amplification differs from the 1D (horizontal layering) case. Considering incident fields of plane harmonic waves, we examine the relationships between the amplification level and the most relevant physical parameters of the problem (impedance contrast, 3D aspect ratio, vertical and oblique incidence of plane waves). The FMBEM results show that the most important parameters for wave amplification are the impedance contrast and the so-called equivalent shape ratio. Using these two parameters, we derive simple rules to compute the fundamental frequency for various 3D basin shapes and the corresponding 3D/1D amplification factor for 5% damping. Effects on amplification due to 3D basin asymmetry are also studied and incorporated in the derived rules.
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.
MHD Simulations of the Plasma Flow in the Magnetic Nozzle
Smith, T. E. R.; Keidar, M.; Sankaran, K.; olzin, K. A.
2013-01-01
The magnetohydrodynamic (MHD) flow of plasma through a magnetic nozzle is simulated by solving the governing equations for the plasma flow in the presence of an static magnetic field representing the applied nozzle. This work will numerically investigate the flow and behavior of the plasma as the inlet plasma conditions and magnetic nozzle field strength are varied. The MHD simulations are useful for addressing issues such as plasma detachment and to can be used to gain insight into the physical processes present in plasma flows found in thrusters that use magnetic nozzles. In the model, the MHD equations for a plasma, with separate temperatures calculated for the electrons and ions, are integrated over a finite cell volume with flux through each face computed for each of the conserved variables (mass, momentum, magnetic flux, energy) [1]. Stokes theorem is used to convert the area integrals over the faces of each cell into line integrals around the boundaries of each face. The state of the plasma is described using models of the ionization level, ratio of specific heats, thermal conductivity, and plasma resistivity. Anisotropies in current conduction due to Hall effect are included, and the system is closed using a real-gas equation of state to describe the relationship between the plasma density, temperature, and pressure.A separate magnetostatic solver is used to calculate the applied magnetic field, which is assumed constant for these calculations. The total magnetic field is obtained through superposition of the solution for the applied magnetic field and the self-consistently computed induced magnetic fields that arise as the flowing plasma reacts to the presence of the applied field. A solution for the applied magnetic field is represented in Fig. 1 (from Ref. [2]), exhibiting the classic converging-diverging field pattern. Previous research was able to demonstrate effects such as back-emf at a super-Alfvenic flow, which significantly alters the shape of the
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...
Numerical simulation of 3D backward facing step flows at various Reynolds numbers
Directory of Open Access Journals (Sweden)
Louda Petr
2015-01-01
Full Text Available The work deals with the numerical simulation of 3D turbulent flow over backward facing step in a narrow channel. The mathematical model is based on the RANS equations with an explicit algebraic Reynolds stress model (EARSM. The numerical method uses implicit finite volume upwind discretization. While the eddy viscosity models fail in predicting complex 3D flows, the EARSM model is shown to provide results which agree well with experimental PIV data. The reference experimental data provide the 3D flow field. The simulations are compared with experiment for 3 values of Reynolds number.
Simulação 3D de movimento ortodôntico 3D simulation of orthodontic tooth movement
Directory of Open Access Journals (Sweden)
Norman Duque Penedo
2010-10-01
Full Text Available OBJETIVO: desenvolver e validar, através do Método dos Elementos Finitos (MEF, um modelo numérico tridimensional (3D de um incisivo central superior para simular o movimento dentário. MÉTODOS: esse modelo contempla a unidade dentária, o osso alveolar e o ligamento periodontal. Permite a simulação dos diferentes movimentos dentários e a determinação dos centros de rotação e de resistência. Limita o movimento ao espaço periodontal, registrando a direção, quantificando o deslocamento dentário e as tensões iniciais no ligamento periodontal. RESULTADOS: a análise dos deslocamentos dentários e das áreas que recebem tensões iniciais possibilita determinar os tipos de movimentos dentários. Com base nas forças ortodônticas, é possível quantificar a intensidade das tensões em cada região do dente, do ligamento periodontal ou do osso alveolar. Com base nas tensões axiais ao longo do ligamento periodontal e da tensão capilar, é possível predizer, teoricamente, as regiões em que deve ocorrer a remodelação óssea. CONCLUSÃO: o modelo foi validado pela determinação do módulo de elasticidade do ligamento periodontal de forma compatível com dados experimentais existentes na literatura. Os métodos utilizados na construção do modelo permitiram a criação de um modelo completo para uma arcada dentária, o qual possibilita realizar variadas simulações que envolvem a mecânica ortodôntica.OBJECTIVE: To develop and validate a three-dimensional (3D numerical model of a maxillary central incisor to simulate tooth movement using the Finite Element Method (FEM. METHODS: This model encompasses the tooth, alveolar bone and periodontal ligament. It allows the simulation of different tooth movements and the establishment of centers of rotation and resistance. It limits the movement into the periodontal space, recording the direction, quantifying tooth displacement and initial stress in the periodontal ligament. RESULTS: By
Nonlinear evolution of parallel propagating Alfven waves: Vlasov - MHD simulation
Nariyuki, Y; Kumashiro, T; Hada, T
2009-01-01
Nonlinear evolution of circularly polarized Alfv\\'en waves are discussed by using the recently developed Vlasov-MHD code, which is a generalized Landau-fluid model. The numerical results indicate that as far as the nonlinearity in the system is not so large, the Vlasov-MHD model can validly solve time evolution of the Alfv\\'enic turbulence both in the linear and nonlinear stages. The present Vlasov-MHD model is proper to discuss the solar coronal heating and solar wind acceleration by Alfve\\'n waves propagating from the photosphere.
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
Center-to-Limb Variation of Solar 3-D Hydrodynamical Simulations
Koesterke, L; Lambert, D L
2008-01-01
We examine closely the solar Center-to-Limb variation of continua and lines and compare observations with predictions from both a 3-D hydrodynamic simulation of the solar surface (provided by M. Asplund and collaborators) and 1-D model atmospheres. Intensities from the 3-D time series are derived by means of the new synthesis code ASSET, which overcomes limitations of previously available codes by including a consistent treatment of scattering and allowing for arbitrarily complex line and continuum opacities. In the continuum, we find very similar discrepancies between synthesis and observation for both types of model atmospheres. This is in contrast to previous studies that used a ``horizontally'' and time averaged representation of the 3-D model and found a significantly larger disagreement with observations. The presence of temperature and velocity fields in the 3-D simulation provides a significant advantage when it comes to reproduce solar spectral line shapes. Nonetheless, a comparison of observed and s...
3D Simulation of External Flooding Events for the RISMC Pathway
Energy Technology Data Exchange (ETDEWEB)
Prescott, Steven [Idaho National Lab. (INL), Idaho Falls, ID (United States); Mandelli, Diego [Idaho National Lab. (INL), Idaho Falls, ID (United States); Sampath, Ramprasad [Idaho National Lab. (INL), Idaho Falls, ID (United States); Smith, Curtis [Idaho National Lab. (INL), Idaho Falls, ID (United States); Lin, Linyu [Idaho National Lab. (INL), Idaho Falls, ID (United States)
2015-09-01
Incorporating 3D simulations as part of the Risk-Informed Safety Margins Characterization (RISMIC) Toolkit allows analysts to obtain a more complete picture of complex system behavior for events including external plant hazards. External events such as flooding have become more important recently – however these can be analyzed with existing and validated simulated physics toolkits. In this report, we describe these approaches specific to flooding-based analysis using an approach called Smoothed Particle Hydrodynamics. The theory, validation, and example applications of the 3D flooding simulation are described. Integrating these 3D simulation methods into computational risk analysis provides a spatial/visual aspect to the design, improves the realism of results, and can prove visual understanding to validate the analysis of flooding.
Application of 3-D numerical simulation software SRIFCAST to produce ductile iron castings
Institute of Scientific and Technical Information of China (English)
无
2005-01-01
Based on a method using numerical simulation equations and their solution schemes for liquid metal flows and heat transfer during mold filling and the solidification process of casting, 3-D numerical simulation software SRIFCAST was created. This includes enmeshment of casting; velocity and temperature fields calculation; displaying iso-temperature lines;velocity vectors and 3-D temperature fields on a Windows 9x operating system. SRIFCAST was applied to produce sound castings of automobile and diesel engines, and also to connect with microstructure simulation for ductile iron castings.
Energy Technology Data Exchange (ETDEWEB)
Steven Prescott; Ramprasad Sampath; Curtis Smith; Tony Koonce
2014-09-01
Computers have been used for 3D modeling and simulation, but only recently have computational resources been able to give realistic results in a reasonable time frame for large complex models. This report addressed the methods, techniques, and resources used to develop a prototype for using 3D modeling and simulation engine to improve risk analysis and evaluate reactor structures and components for a given scenario. The simulations done for this evaluation were focused on external events, specifically tsunami floods, for a hypothetical nuclear power facility on a coastline.
MORPHOLOGY AND DYNAMICS OF SOLAR PROMINENCES FROM 3D MHD SIMULATIONS
Energy Technology Data Exchange (ETDEWEB)
Terradas, J.; Soler, R.; Oliver, R.; Ballester, J. L. [Departament de Física, Universitat de les Illes Balears, E-07122 Palma de Mallorca (Spain); Luna, M., E-mail: jaume.terradas@uib.es [Instituto de Astrofísica de Canarias, E-38200 La Laguna, Tenerife (Spain)
2015-01-20
In this paper we present a numerical study of the time evolution of solar prominences embedded in sheared magnetic arcades. The prominence is represented by a density enhancement in a background-stratified atmosphere and is connected to the photosphere through the magnetic field. By solving the ideal magnetohydrodynamic equations in three dimensions, we study the dynamics for a range of parameters representative of real prominences. Depending on the parameters considered, we find prominences that are suspended above the photosphere, i.e., detached prominences, but also configurations resembling curtain or hedgerow prominences whose material continuously connects to the photosphere. The plasma-β is an important parameter that determines the shape of the structure. In many cases magnetic Rayleigh-Taylor instabilities and oscillatory phenomena develop. Fingers and plumes are generated, affecting the whole prominence body and producing vertical structures in an essentially horizontal magnetic field. However, magnetic shear is able to reduce or even to suppress this instability.
Terradas, J; Luna, M; Oliver, R; Ballester, J L; Wright, A N
2015-01-01
The temporal evolution of a solar prominence inserted in a three-dimensional magnetic flux rope is investigated numerically. Using the model of Titov Demoulin (1999) under the regime of weak twist, the cold and dense prominence counteracts gravity by modifying the initially force-free magnetic configuration. In some cases a quasi-stationary situation is achieved after the relaxation phase, characterized by the excitation of standing vertical oscillations. These oscillations show a strong attenuation with time produced by the mechanism of continuum damping due to the inhomogeneous transition between the prominence and solar corona. The characteristic period of the vertical oscillations does not depend strongly on the twist of the flux rope. Nonlinearity is the responsible for triggering the Kelvin-Helmholtz instability associated to the vertical oscillations and that eventually produces horizontal structures. Contrary to other configurations in which the longitudinal axis of the prominence is permeated by a pe...
Energy Technology Data Exchange (ETDEWEB)
Terradas, J.; Soler, R.; Oliver, R.; Ballester, J. L. [Departament de Física, Universitat de les Illes Balears, E-07122 Palma de Mallorca (Spain); Luna, M. [Instituto de Astrofsíca de Canarias, E-38205 La Laguna, Tenerife (Spain); Wright, A. N., E-mail: jaume.terradas@uib.es [School of Mathematics and Statistics, University of St Andrews, St Andrews, KY16 9SS (United Kingdom)
2016-04-01
The temporal evolution of a solar prominence inserted in a three-dimensional magnetic flux rope is investigated numerically. Using the model of Titov and Démoulin under the regime of weak twist, the cold and dense prominence counteracts gravity by modifying the initially force-free magnetic configuration. In some cases a quasi-stationary situation is achieved after the relaxation phase, characterized by the excitation of standing vertical oscillations. These oscillations show a strong attenuation with time produced by the mechanism of continuum damping due to the inhomogeneous transition between the prominence and solar corona. The characteristic period of the vertical oscillations does not depend strongly on the twist of the flux rope. Nonlinearity is responsible for triggering the Kelvin–Helmholtz instability associated with the vertical oscillations and that eventually produces horizontal structures. Contrary to other configurations in which the longitudinal axis of the prominence is permeated by a perpendicular magnetic field, like in unsheared arcades, the orientation of the prominence along the flux rope axis prevents the development of Rayleigh–Taylor instabilities and therefore the appearance of vertical structuring along this axis.
Calculation of residual stresses by means of a 3D numerical weld simulation
Energy Technology Data Exchange (ETDEWEB)
Nicak, Tomas; Huemmer, Matthias [AREVA NP GmbH, Postfach 1109 (Germany)
2008-07-01
The numerical weld simulation has developed very fast in recent years. The problem complexity has increased from simple 2D models to full 3D models, which can describe the entire welding process more realistically. As recent research projects indicate, a quantitative assessment of the residual stresses by means of a 3D analysis is possible. The structure integrity can be assessed based on the weld simulation results superimposed with the operating load. Moreover, to support the qualification of welded components parametric studies for optimization of the residual stress distribution in the weld region can be performed. In this paper a full 3D numerical weld simulation for a man-hole drainage nozzle in a steam generator will be presented. The residual stresses are calculated by means of an uncoupled transient thermal and mechanical FE analysis. The paper will present a robust procedure allowing reasonable predictions of the residual stresses for complex structures in industrial practice. (authors)
2012-02-28
Engineering, 2010. 8 Roth, T., “ Modeling and Numerical Simulations of Pulse Detonation Engines with MHD Thrust Augmentation”, M.S. thesis, Department of...throat, at time 2.3ms. Results are shown for the PDE (blow-down model ) with and without MHD generation in the region between 0.4 and 0.8m from the...down model ) for different values of the exit- to-throat area ratio and for different altitudes, without MHD generation and without the presence of the
Simulating receptive fields of human visual cortex for 3D image quality prediction.
Shao, Feng; Chen, Wanting; Lin, Wenchong; Jiang, Qiuping; Jiang, Gangyi
2016-07-20
Quality assessment of 3D images presents many challenges when attempting to gain better understanding of the human visual system. In this paper, we propose a new 3D image quality prediction approach by simulating receptive fields (RFs) of human visual cortex. To be more specific, we extract the RFs from a complete visual pathway, and calculate their similarity indices between the reference and distorted 3D images. The final quality score is obtained by determining their connections via support vector regression. Experimental results on three 3D image quality assessment databases demonstrate that in comparison with the most relevant existing methods, the devised algorithm achieves high consistency alignment with subjective assessment, especially for asymmetrically distorted stereoscopic images.
Mixed reality orthognathic surgical simulation by entity model manipulation and 3D-image display
Shimonagayoshi, Tatsunari; Aoki, Yoshimitsu; Fushima, Kenji; Kobayashi, Masaru
2005-12-01
In orthognathic surgery, the framing of 3D-surgical planning that considers the balance between the front and back positions and the symmetry of the jawbone, as well as the dental occlusion of teeth, is essential. In this study, a support system for orthodontic surgery to visualize the changes in the mandible and the occlusal condition and to determine the optimum position in mandibular osteotomy has been developed. By integrating the operating portion of a tooth model that is to determine the optimum occlusal position by manipulating the entity tooth model and the 3D-CT skeletal images (3D image display portion) that are simultaneously displayed in real-time, the determination of the mandibular position and posture in which the improvement of skeletal morphology and occlusal condition is considered, is possible. The realistic operation of the entity model and the virtual 3D image display enabled the construction of a surgical simulation system that involves augmented reality.
Madura, Thomas; Gull, Theodore R.; Clementel, Nicola; Paardekooper, Jan-Pieter; Kruip, Chael; Corcoran, Michael F.; Hamaguchi, Kenji; Teodoro, Mairan
2015-01-01
We present the first 3D prints of output from a supercomputer simulation of a complex astrophysical system, the colliding stellar winds in the massive (>120 MSun), highly eccentric (e ~ 0.9) binary Eta Carinae. Using a consumer-grade 3D printer (Makerbot Replicator 2X), we successfully printed 3D smoothed particle hydrodynamics simulations of Eta Carinae's inner (r ~110 AU) wind-wind collision interface at multiple orbital phases. These 3D prints reveal important, previously unknown 'finger-like' structures at orbital phases shortly after periastron (φ ~1.045) that protrude radially outward from the spiral wind-wind collision region. We speculate that these fingers are related to instabilities (e.g. Rayleigh-Taylor) that arise at the interface between the radiatively-cooled layer of dense post-shock primary-star wind and the hot, adiabatic post-shock companion-star wind. The success of our work and easy identification of previously unknown physical features highlight the important role 3D printing can play in the visualization and understanding of complex 3D time-dependent numerical simulations of astrophysical phenomena.
Detached eddy simulation of unsteady cavitation and pressure fluctuation around 3-D NACA66 hydrofoil
Directory of Open Access Journals (Sweden)
Zhang De-Sheng
2015-01-01
Full Text Available The unsteady cavitating flow and pressure fluctuation around the 3-D NACA66 hydrofoil were simulated and validated based on detached eddy simulation turbulence model and a homogeneous cavitation model. Numerical results show that detached eddy simulation can predict the evolution of cavity inception, sheet cavitation growth, cloud cavitation shedding, and breakup, as well as the pressure fluctuation on the surface of hydrofoil. The sheet cavitation growth, detachment, cloud cavitation shedding are responsible for the features of the pressure fluctuation.
Study of 3-D Numerical Simulation for Gas Transfer in the Goaf of the Coal Mining
Institute of Scientific and Technical Information of China (English)
WU Zheng-yan; JIANG Shu-guang; HE Xin-jian; WANG Lan-yun; LIN Bai-quan
2007-01-01
In order to simulate field distribution rules, mathematical models for 3-D air flows and gas transfer in the goaf of the coal mining are established, based on theories of permeability and dynamic dispersion through porous media. A gas dispersion equation in a 3-D field is calculated by use of numerical method on a weighted upstream multi-element balance. Based on data of an example with a U type ventilation mode, surface charts of air pressure distribution and gas concentration are drawn by Graphtool software. Finally, a comparison between actually measured results in the model test and the numerical simulation results is made to proves the numerical implementation feasible.
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.
Wareing, C J; Falle, S A E G; Van Loo, S
2016-01-01
We have used the AMR hydrodynamic code, MG, to perform 3D MHD simulations of the formation of clumpy and filamentary structure in a thermally unstable medium. A stationary thermally unstable spherical diffuse cloud with uniform density in pressure equilibrium with low density surroundings was seeded with random density variations and allowed to evolve. A range of magnetic field strengths threading the cloud have been explored, from beta=0.1 to beta=1.0 to the zero magnetic field case (beta=infinity), where beta is the ratio of thermal pressure to magnetic pressure. Once the density inhomogeneities had developed to the point where gravity started to become important, self-gravity was introduced to the simulation. With no magnetic field, clumps form within the cloud with aspect ratios of around unity, whereas in the presence of a relatively strong field (beta=0.1) these become filaments, then evolve into interconnected corrugated sheets that are predominantly perpendicular to the magnetic field. With magnetic a...
Attempts to Simulate Anisotropies of Solar Wind Fluctuations Using MHD with a Turning Magnetic Field
Ghosh, Sanjoy; Roberts, D. Aaron
2010-01-01
We examine a "two-component" model of the solar wind to see if any of the observed anisotropies of the fields can be explained in light of the need for various quantities, such as the magnetic minimum variance direction, to turn along with the Parker spiral. Previous results used a 3-D MHD spectral code to show that neither Q2D nor slab-wave components will turn their wave vectors in a turning Parker-like field, and that nonlinear interactions between the components are required to reproduce observations. In these new simulations we use higher resolution in both decaying and driven cases, and with and without a turning background field, to see what, if any, conditions lead to variance anisotropies similar to observations. We focus especially on the middle spectral range, and not the energy-containing scales, of the simulation for comparison with the solar wind. Preliminary results have shown that it is very difficult to produce the required variances with a turbulent cascade.
Accurate load prediction by BEM with airfoil data from 3D RANS simulations
Schneider, Marc S.; Nitzsche, Jens; Hennings, Holger
2016-09-01
In this paper, two methods for the extraction of airfoil coefficients from 3D CFD simulations of a wind turbine rotor are investigated, and these coefficients are used to improve the load prediction of a BEM code. The coefficients are extracted from a number of steady RANS simulations, using either averaging of velocities in annular sections, or an inverse BEM approach for determination of the induction factors in the rotor plane. It is shown that these 3D rotor polars are able to capture the rotational augmentation at the inner part of the blade as well as the load reduction by 3D effects close to the blade tip. They are used as input to a simple BEM code and the results of this BEM with 3D rotor polars are compared to the predictions of BEM with 2D airfoil coefficients plus common empirical corrections for stall delay and tip loss. While BEM with 2D airfoil coefficients produces a very different radial distribution of loads than the RANS simulation, the BEM with 3D rotor polars manages to reproduce the loads from RANS very accurately for a variety of load cases, as long as the blade pitch angle is not too different from the cases from which the polars were extracted.
2D-3D hybrid stabilized finite element method for tsunami runup simulations
Takase, S.; Moriguchi, S.; Terada, K.; Kato, J.; Kyoya, T.; Kashiyama, K.; Kotani, T.
2016-09-01
This paper presents a two-dimensional (2D)-three-dimensional (3D) hybrid stabilized finite element method that enables us to predict a propagation process of tsunami generated in a hypocentral region, which ranges from offshore propagation to runup to urban areas, with high accuracy and relatively low computational costs. To be more specific, the 2D shallow water equation is employed to simulate the propagation of offshore waves, while the 3D Navier-Stokes equation is employed for the runup in urban areas. The stabilized finite element method is utilized for numerical simulations for both of the 2D and 3D domains that are independently discretized with unstructured meshes. The multi-point constraint and transmission methods are applied to satisfy the continuity of flow velocities and pressures at the interface between the resulting 2D and 3D meshes, since neither their spatial dimensions nor node arrangements are consistent. Numerical examples are presented to demonstrate the performance of the proposed hybrid method to simulate tsunami behavior, including offshore propagation and runup to urban areas, with substantially lower computation costs in comparison with full 3D computations.
Flattening simulations of 3D thick sheets made of fiber composite materials
Directory of Open Access Journals (Sweden)
Kotaro Morioka
2015-04-01
Full Text Available Recently, fiber composite materials have been attracting attention from industry because of their remarkable material characteristics, including light weight and high stiffness. However, the costs of products composed of fiber materials remain high because of the lack of effective manufacturing and designing technologies. To improve the relevant design technology, this paper proposes a novel simulation method for deforming fiber materials. Specifically, given a 3D model with constant thickness and known fiber orientation, the proposed method simulates the deformation of a model made of thick fiber-material. The method separates a 3D sheet model into two surfaces and then flattens these surfaces into two dimensional planes by a parameterization method with involves cross vector fields. The cross vector fields are generated by propagating the given fiber orientations specified at several important points on the 3D model. Integration of the cross vector fields gives parameterization with low-stretch and low-distortion.
3D Numerical Simulation Analysis of Passive Drag near Free Surface in Swimming
Institute of Scientific and Technical Information of China (English)
詹杰民; 李天赠; 陈学彬; 李毓湘; 韦永康
2015-01-01
The aim of this work is to build a 3D numerical model to study the characteristics of passive drag on competitive swimmers taking into account the impact of the free surface. This model solves the 3D incompressible Navier-Stokes equations using RNG k-εturbulence closure. The volume of fluid (VOF) method is used to locate the free surface. The 3D virtual model is created by Computer Aided Industrial Design (CAID) software, Rhinoceros. Firstly, a specific posture of swimming is studied. The simulation results are in good agreement with the data from mannequin towing experiments. The effects of a swimmer’s arms and legs positions on swimming performance are then studied. Finally, it is demonstrated that the present method is capable of simulating gliding near the free surface.
3D numerical simulation analysis of passive drag near free surface in swimming
Zhan, Jie-min; Li, Tian-zeng; Chen, Xue-bin; Li, Yok-sheung; Wai, Wing-hong Onyx
2015-04-01
The aim of this work is to build a 3D numerical model to study the characteristics of passive drag on competitive swimmers taking into account the impact of the free surface. This model solves the 3D incompressible Navier-Stokes equations using RNG k- ɛ turbulence closure. The volume of fluid (VOF) method is used to locate the free surface. The 3D virtual model is created by Computer Aided Industrial Design (CAID) software, Rhinoceros. Firstly, a specific posture of swimming is studied. The simulation results are in good agreement with the data from mannequin towing experiments. The effects of a swimmer's arms and legs positions on swimming performance are then studied. Finally, it is demonstrated that the present method is capable of simulating gliding near the free surface.
A Jones matrix formalism for simulating 3D Polarised Light Imaging of brain tissue
Menzel, Miriam; De Raedt, Hans; Reckfort, Julia; Amunts, Katrin; Axer, Markus
2015-01-01
The neuroimaging technique 3D Polarised 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 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 ...
Stochastic microstructure modeling and electrochemical simulation of lithium-ion cell anodes in 3D
Hein, Simon; Feinauer, Julian; Westhoff, Daniel; Manke, Ingo; Schmidt, Volker; Latz, Arnulf
2016-12-01
Thermodynamically consistent transport theory is used to compare 3D images of real anode microstructures from lithium-ion batteries to virtual ones created by a parametric stochastic 3D microstructure model. Half-cell simulations in 3D with spatially resolved microstructures at different applied currents show that for low currents the deviations between various electrochemical quantities like current density or overpotential are negligibly small. For larger currents small differences become more pronounced. Qualitative and quantitative differences of these features are discussed with respect to the microstructure and it is shown that the real and virtual structures behave similar during electrochemical simulations. Extensions of the stochastic microstructure model, which overcome small differences in electrochemical behavior, are proposed.
Kempka, Thomas; Nakaten, Benjamin; De Lucia, Marco; Nakaten, Natalie; Otto, Christopher; Pohl, Maik; Tillner, Elena; Kühn, Michael
2016-04-01
Utilization of the geological subsurface for production and storage of hydrocarbons, chemical energy and heat as well as for waste disposal requires the quantification and mitigation of environmental impacts as well as the improvement of georesources utilization in terms of efficiency and sustainability. The development of tools for coupled process simulations is essential to tackle these challenges, since reliable assessments are only feasible by integrative numerical computations. Coupled processes at reservoir to regional scale determine the behaviour of reservoirs, faults and caprocks, generally demanding for complex 3D geological models to be considered besides available monitoring and experimenting data in coupled numerical simulations. We have been developing a flexible numerical simulation framework that provides efficient workflows for integrating the required data and software packages to carry out coupled process simulations considering, e.g., multiphase fluid flow, geomechanics, geochemistry and heat. Simulation results are stored in structured data formats to allow for an integrated 3D visualization and result interpretation as well as data archiving and its provision to collaborators. The main benefits in using the flexible simulation framework are the integration of data geological and grid data from any third party software package as well as data export to generic 3D visualization tools and archiving formats. The coupling of the required process simulators in time and space is feasible, while different spatial dimensions in the coupled simulations can be integrated, e.g., 0D batch with 3D dynamic simulations. User interaction is established via high-level programming languages, while computational efficiency is achieved by using low-level programming languages. We present three case studies on the assessment of geological subsurface utilization based on different process coupling approaches and numerical simulations.
Simulation System Design of 3-D Panorama of Ship Motions in Wave
Institute of Scientific and Technical Information of China (English)
LIU; Ya-dong; LI; Ji-de; LI; Zhen
2002-01-01
In this paper a 3-D panoramic simulation system of a ship is described which is developed with the MAXSCRIPT language and VC++ as programming tools on the platform of 3Dsmax. The strip theory method is applied to the motion prediction of the mono-hull. The time history solutions of heave and pitch are obtained in the condition of head sea to provide the primary data on panoramic simulation. The simulation system has following functions: 1)digital simulation;2) panoramic simulation; 3) environmental set-up; 4) render preview and output.
Renal Tumor Cryoablation Planning. The Efficiency of Simulation on Reconstructed 3D CT Scan
Directory of Open Access Journals (Sweden)
Ciprian Valerian LUCAN
2010-12-01
Full Text Available Introduction & Objective: Nephron-sparing surgical techniques risks are related to tumor relationships with adjacent anatomic structures. Complexity of the renal anatomy drives the interest to develop tools for 3D reconstruction and surgery simulation. The aim of the article was to assess the simulation on reconstructed 3D CT scan used for planning the cryoablation. Material & Method: A prospective randomized study was performed between Jan. 2007 and July 2009 on 27 patients who underwent retroperitoneoscopic T1a renal tumors cryoablation (RC. All patients were assessed preoperatively by CT scan, also used for 3D volume rendering. In the Gr.A, the patients underwent surgery planning by simulation on 3D CT scan. In the Gr.B., patients underwent standard RC. The two groups were compared in terms of surgical time, bleeding, postoperative drainage, analgesics requirement, hospital stay, time to socio-professional reintegration. Results: Fourteen patients underwent preoperative cryoablation planning (Gr.A and 13 patients underwent standard CR (Gr.B. All parameters analyzed were shorter in the Gr.A. On multivariate logistic regression, only shortens of the surgical time (138.79±5.51 min. in Gr.A. vs. 140.92±5.54 min in Gr.B. and bleeding (164.29±60.22 mL in Gr.A. vs. 215.38±100.80 mL in Gr.B. achieved statistical significance (p<0.05. The number of cryoneedles assessed by simulation had a 92.52% accuracy when compared with those effectively used. Conclusions: Simulation of the cryoablation using reconstructed 3D CT scan improves the surgical results. The application used for simulation was able to accurately assess the number of cryoneedles required for tumor ablation, their direction and approach.
Energy Technology Data Exchange (ETDEWEB)
Grafenberger, P.; Klinner, P.; Nefischer, P. [BMW Motoren GmbH, Steyr (Austria); Klingebiel, F. [AMSTRAL Engineering fuer Stroemungsmechanik GmbH, Idstein (Germany)
2000-04-01
Shorting the development time for new engines and vehicles is leading to the increasing use of computational design and simulation methods in the automotive industry. For several years now, both one-dimensional and three-dimensional flow computation have been used successfully in the development of cooling systems. However, the fact that less hardware is used in the early development stages makes new demands on the quality and quantity of these simulation results. BMW's diesel development division has been able to improve the quality of the results and to reduce the processing time by improving the model quality and by coupling existing 1D and 3D computational fluid dynamic programmes. (orig.) [German] Die Verkuerzung der Entwicklungszeit neuer Motoren und Automobile fuehrt zu einem verstaerkten Einsatz von rechnergestuetzten Konstruktions- und Simulationsmethoden in der Fahrzeugindustrie. Sowohl eindimensionale als auch dreidimensionale Stroemungsberechnungen werden seit Jahren erfolgreich bei der Entwicklung von Kuehlsystemen eingesetzt. Der Entfall von Hardware-Baugruppen in der fruehen Entwicklungsphase stellt jedoch neue Anforderungen an die Qualitaet und Quantitaet dieser Simulationsergebnisse. Durch Verbesserung der Modellqualitaet und durch Kopplung vorhandener 1D- und 3D-Stroemungsberechnungsprogramme konnten in der Dieselmotorenentwicklung von BMW die Qualitaet der Ergebnisse und die Bearbeitungsgeschwindigkeit deutlich gesteigert werden. (orig.)
[Pre-surgical simulation of microvascular decompression for hemifacial spasm using 3D-models].
Mashiko, Toshihiro; Yang, Qiang; Kaneko, Naoki; Konno, Takehiko; Yamaguchi, Takashi; Watanabe, Eiju
2015-01-01
We have been performing pre-surgical simulations using custom-built patient-specific 3D-models. Here we report the advantageous use of 3D-models for simulating microvascular decompression(MVD)for hemifacial spasms. Seven cases of MVD surgery were performed. Two types of 3D-printers were used to fabricate the 3D-models:one using plaster as the modeling material(Z Printer®450, 3D systems, Rock Hill, SC, USA)and the other using acrylonitrile butadiene styrene(ABS)(UP! Plus 3D printer®, Beijing Tiertime Technology, Beijing). We tested three types of models. Type 1 was a plaster model of the brainstem, cerebellum, facial nerve, and the artery compressing the root exit zone of the facial nerve. Part of the cerebellum was digitally trimmed off to observe "the compressing point" from the same angle as that used during actual surgery. Type 2 was a modified Type 1 in which part of the skull was opened digitally to mimic a craniectomy. Type 3 was a combined model in which the cerebellum and the artery of the Type 2 model were replaced by a soft retractable cerebellum and an elastic artery. The cerebellum was made from polyurethane and cast from a plaster prototype. To fabricate elastic arteries, liquid silicone was painted onto the surface of an ABS artery and the inner ABS model was dissolved away using solvent. In all cases, the 3D-models were very useful. Although each type has advantages, the Type-3 model was judged extremely useful for training junior surgeons in microsurgical approaches.
An Object-Oriented Simulator for 3D Digital Breast Tomosynthesis Imaging System
Directory of Open Access Journals (Sweden)
Saeed Seyyedi
2013-01-01
Full Text Available Digital breast tomosynthesis (DBT is an innovative imaging modality that provides 3D reconstructed images of breast to detect the breast cancer. Projections obtained with an X-ray source moving in a limited angle interval are used to reconstruct 3D image of breast. Several reconstruction algorithms are available for DBT imaging. Filtered back projection algorithm has traditionally been used to reconstruct images from projections. Iterative reconstruction algorithms such as algebraic reconstruction technique (ART were later developed. Recently, compressed sensing based methods have been proposed in tomosynthesis imaging problem. We have developed an object-oriented simulator for 3D digital breast tomosynthesis (DBT imaging system using C++ programming language. The simulator is capable of implementing different iterative and compressed sensing based reconstruction methods on 3D digital tomosynthesis data sets and phantom models. A user friendly graphical user interface (GUI helps users to select and run the desired methods on the designed phantom models or real data sets. The simulator has been tested on a phantom study that simulates breast tomosynthesis imaging problem. Results obtained with various methods including algebraic reconstruction technique (ART and total variation regularized reconstruction techniques (ART+TV are presented. Reconstruction results of the methods are compared both visually and quantitatively by evaluating performances of the methods using mean structural similarity (MSSIM values.
Simulation of free surfaces in 3-D with the arbitrary Lagrange-Euler method
DEFF Research Database (Denmark)
Szabo, Peter; Hassager, Ole
1995-01-01
The arbitrary Lagrange-Euler (ALE) kinematic description has been implemented in a 3-D transient finite element program so as to simulate multiple fluid flows with Surfaces and interfaces of general shapes. The description of fluid interfaces includes continuity of velocity and a discontinuous...
Numerical Simulation of Transient Flows around a 3D Pitching Hydrofoil
Directory of Open Access Journals (Sweden)
Qin Wu
2015-02-01
Full Text Available The objective of this paper is to investigate the hydrodynamic characteristics of the transient flows around a 3D pitching hydrofoil via numerical studies, where the effects of tunnel wall boundary layer and gap flows are considered. Simulations are performed using an unsteady Reynolds Average Navier-Stokes solver and the k-ω SST turbulence model, coupled with a two-equation γ-Reθ transition model. Hydrodynamic forces and flow structures are compared to the results with the equivalent 2D computations. During the upward pitching stage, the transition phenomenon is accurately captured by both the 2D and 3D simulations. The slightly lower lift and suction side loading coefficients predicted by the 3D simulation are due to the pressure effects caused by the tip gap flow. During the dynamic stall stage, the 2D case exhibits a clear overshoot on the hydrodynamic force coefficients and the 3D simulation results better agree with the experimental results. During the downward pitching stage, the flow transitions back to laminar. As for the effect of gap flow and the wall boundary condition, the gap flow causes disturbances to the formation and development of the vortex structures, resulting in the complex distribution of the three-dimensional streamlines and the particle path.
Institute of Scientific and Technical Information of China (English)
WANG Xin-yun; GUO Zhi-feng; QINWen-hans; SUN Guo-qing
2011-01-01
It is difficulties for the computer simulation method to study radiation regime at large-scale.Simplified coniferous model was investigated in the present study.It makes the computer simulation methods such as L-systems and radiosity-graphics combined method (RGM) more powerful in remote sensing of heterogeneous coniferous forests over a large-scale region.L-systems is applied to render 3-D coniferous forest scenarios,and RGM model was used to calculate BRF (bidirectional reflectance factor) in visible and near-infrared regions.Results in this study show that in most cases both agreed well Meanwhile at a tree and forest level,the results are also good.
Clementel, N.; Madura, T. I.; Kruip, C. J. H.; Icke, V.; Gull, T. R.
2014-01-01
Eta Carinae is an ideal astrophysical laboratory for studying massive binary interactions and evolution, and stellar wind-wind collisions. Recent three-dimensional (3D) simulations set the stage for understanding the highly complex 3D flows in Eta Car. Observations of different broad high- and low-ionization forbidden emission lines provide an excellent tool to constrain the orientation of the system, the primary's mass-loss rate, and the ionizing flux of the hot secondary. In this work we present the first steps towards generating synthetic observations to compare with available and future HST/STIS data. We present initial results from full 3D radiative transfer simulations of the interacting winds in Eta Car. We use the SimpleX algorithm to post-process the output from 3D SPH simulations and obtain the ionization fractions of hydrogen and helium assuming three different mass-loss rates for the primary star. The resultant ionization maps of both species constrain the regions where the observed forbidden emission lines can form. Including collisional ionization is necessary to achieve a better description of the ionization states, especially in the areas shielded from the secondary's radiation. We find that reducing the primary's mass-loss rate increases the volume of ionized gas, creating larger areas where the forbidden emission lines can form. We conclude that post processing 3D SPH data with SimpleX is a viable tool to create ionization maps for Eta Car.
The computer simulation of 3d gas dynamics in a gas centrifuge
Borman, V. D.; Bogovalov, S. V.; Borisevich, V. D.; Tronin, I. V.; Tronin, V. N.
2016-09-01
We argue on the basis of the results of 2D analysis of the gas flow in gas centrifuges that a reliable calculation of the circulation of the gas and gas content in the gas centrifuge is possible only in frameworks of 3D numerical simulation of gas dynamics in the gas centrifuge (hereafter GC). The group from National research nuclear university, MEPhI, has created a computer code for 3D simulation of the gas flow in GC. The results of the computer simulations of the gas flows in GC are presented. A model Iguassu centrifuge is explored for the simulations. A nonaxisymmetric gas flow is produced due to interaction of the hypersonic rotating flow with the scoops for extraction of the product and waste flows from the GC. The scoops produce shock waves penetrating into a working camera of the GC and form spiral waves there.
The Vajont disaster: a 3D numerical simulation for the slide and the waves
Rubino, Angelo; Androsov, Alexey; Vacondio, Renato; Zanchettin, Davide; Voltzinger, Naum
2016-04-01
A very high resolution O(5 m), 3D hydrostatic nonlinear numerical model was used to simulate the dynamics of both the slide and the surface waves produced during the Vajont disaster (north Italy, 1963), one of the major landslide-induced tsunamis ever documented. Different simulated wave phenomena like, e.g., maximum run-up on the opposite shore, maximum height, and water velocity were analyzed and compared with data available in literature, including the results of a fully 3D simulation obtained with a Smoothed Particle Hydrodynamic code. The difference between measured and simulated after-slide bathymetries was calculated and used in an attempt to quantify the relative magnitude and extension of rigid and fluid motion components during the event.
VITASCOPE: Extensible and Scalable 3D Visualization of Simulated Construction Operations
Kamat, Vineet Rajendra
2003-01-01
In the domain of operations design and analysis, the ability to see a 3D animation of processes that have been simulated allows for three very important things: 1) The developer of a simulation model can ascertain that there are no errors in the coding (Verification); 2) The experts, field personnel, and decision makers can discover differences between the way they understand the operation and the way the model developer understands it (Validation); and 3) A model can be communicated effectiv...
Simulations of 3D Magnetic Merging: Resistive Scalings for Null Point and QSL Reconnection
Effenberger, Frederic
2016-01-01
Starting from an exact, steady-state, force-free solution of the magnetohydrodynamic (MHD) equations, we investigate how resistive current layers are induced by perturbing line-tied three-dimensional magnetic equilibria. This is achieved by the superposition of a weak perturbation field in the domain, in contrast to studies where the boundary is driven by slow motions, like those present in photospheric active regions. Our aim is to quantify how the current structures are altered by the contribution of so called quasi-separatrix layers (QSLs) as the null point is shifted outside the computational domain. Previous studies based on magneto-frictional relaxation have indicated that, despite the severe field line gradients of the QSL, the presence of a null is vital in maintaining fast reconnection. Here, we explore this notion using highly resolved simulations of the full MHD evolution. We show that for the null-point configuration, the resistive scaling of the peak current density is close to $J\\sim\\eta^{-1}$, ...
Simulations of 3D Magnetic Merging: Resistive Scalings for Null Point and QSL Reconnection
Effenberger, Frederic; Craig, I. J. D.
2016-01-01
Starting from an exact, steady-state, force-free solution of the magnetohydrodynamic (MHD) equations, we investigate how resistive current layers are induced by perturbing line-tied three-dimensional magnetic equilibria. This is achieved by the superposition of a weak perturbation field in the domain, in contrast to studies where the boundary is driven by slow motions, like those present in photospheric active regions. Our aim is to quantify how the current structures are altered by the contribution of so-called quasi-separatrix layers (QSLs) as the null point is shifted outside the computational domain. Previous studies based on magneto-frictional relaxation have indicated that despite the severe field line gradients of the QSL, the presence of a null is vital in maintaining fast reconnection. Here, we explore this notion using highly resolved simulations of the full MHD evolution. We show that for the null-point configuration, the resistive scaling of the peak current density is close to J˜η^{-1}, while the scaling is much weaker, i.e. J˜η^{-0.4}, when only the QSL connectivity gradients provide a site for the current accumulation.
MHD simulations of near-surface convection in cool main-sequence stars
Beeck, Benjamin; Reiners, Ansgar
2014-01-01
The solar photospheric magnetic field is highly structured owing to its interaction with the convective flows. Its local structure has a strong influence on the profiles of spectral lines not only by virtue of the Zeeman effect, but also through the modification of the thermodynamical structure (e.g. line weakening in hot small-scale magnetic structures). Many stars harbor surface magnetic fields comparable to or larger than the Sun at solar maximum. Therefore, a strong influence of the field on the surface convection and on spectral line profiles can be expected. We carried out 3D local-box MHD simulations of unipolar magnetized regions (average fields of 20, 100, and 500G) with parameters corresponding to six main-sequence stars (spectral types F3V to M2V). The influence of the magnetic field on the convection and the local thermodynamical structure were analyzed in detail. For three spectral lines, we determined the impact of the magnetic field on the disc-integrated Stokes-I profiles. Line weakening has i...
Effect of the Interplanetary Electric Field on the Magnetopause From Global MHD Simulations
Institute of Scientific and Technical Information of China (English)
HUANG Zhaohui; DING Kai; WANG Chi
2012-01-01
The north-south component B_z of the Interplanetary Magnetic Field（IMF） and solar wind dynamic pressure P_d are generally treated as the two main factors in the solar wind that determine the geometry of the magnetosphere.By using the 3D global MHD simulations,we investigate the effect of the Interplanetary Electric Field（IEF） on the size and shape of magnetopause quantitatively. Our numerical experiments confirm that the geometry of the magnetopause are mainly determined by P_d and B_z,as expected.However,the dawn-dusk IEFs have great impact on the magnetopause erosion because of the magnetic reconnection,thus affecting the size and shape of the magnetopause.Higher solar wind speed with the same B_z will lead to bigger dawn-dusk IEFs,which means the higher reconnection rate,and then results in more magnetic flux removal from the dayside. Consequently,the dayside magnetopause moves inward and flank magnetopause moves outward.
Large Scale Earth's Bow Shock with Northern IMF as simulated by PIC code in parallel with MHD model
Baraka, Suleiman M
2016-01-01
In this paper, we propose a 3D kinetic model (Particle-in-Cell PIC ) for the description of the large scale Earth's bow shock. The proposed version is stable and does not require huge or extensive computer resources. Because PIC simulations work with scaled plasma and field parameters, we also propose to validate our code by comparing its results with the available MHD simulations under same scaled Solar wind ( SW ) and ( IMF ) conditions. We report new results from the two models. In both codes the Earth's bow shock position is found to be ~14.8 RE along the Sun-Earth line, and ~ 29 RE on the dusk side. Those findings are consistent with past in situ observations. Both simulations reproduce the theoretical jump conditions at the shock. However, the PIC code density and temperature distributions are inflated and slightly shifted sunward when compared to the MHD results. Kinetic electron motions and reflected ions upstream may cause this sunward shift. Species distributions in the foreshock region are depicted...
Deng, Wei; Zhang, Bing; Li, Shengtai
2015-01-01
We perform 3D relativistic ideal MHD simulations to study the collisions between high-$\\sigma$ (Poynting-flux-dominated) blobs which contain both poloidal and toroidal magnetic field components. This is meant to mimic the interactions inside a highly variable Poynting-flux-dominated jet. We discover a significant electromagnetic field (EMF) energy dissipation with an Alfv\\'enic rate with the efficiency around 35\\%. Detailed analyses show that this dissipation is mostly facilitated by the collision-induced magnetic reconnection. Additional resolution and parameter studies show a robust result that the relative EMF energy dissipation efficiency is nearly independent of the numerical resolution or most physical parameters in the relevant parameter range. The reconnection outflows in our simulation can potentially form the multi-orientation relativistic mini-jets as needed for several analytical models. We also find a linear relationship between the $\\sigma$ values before and after the major EMF energy dissipatio...
Huang, Z.; Toth, G.; Gombosi, T. I.; Jia, X.; Rubin, M.; Hansen, K. C.; Fougere, N.; Bieler, A. M.; Shou, Y.; Altwegg, K.; Combi, M. R.; Tenishev, V.
2015-12-01
The neutral and plasma environment is critical in understanding the interaction of comet Churyumov-Gerasimenko (CG), the target of the Rosetta mission, and the solar wind. To serve this need and support the Rosetta mission, we develop a 3-D four fluid model, which is based on BATS-R-US within the SWMF (Space Weather Modeling Framework) that solves the governing multi-fluid MHD equations and the Euler equations for the neutral gas fluid. These equations describe the behavior and interactions of the cometary heavy ions, the solar wind protons, the electrons, and the neutrals. This model incorporates different mass loading processes, including photo and electron impact ionization, charge exchange, dissociative ion-electron recombination, and collisional interactions between different fluids. We simulate the near nucleus plasma and neutral gas environment near perihelion with a realistic shape model of CG and compare our simulation results with Rosetta observations.
Simulations of 3D-Si sensors for the innermost layer of the ATLAS pixel upgrade
Baselga, M.; Pellegrini, G.; Quirion, D.
2017-03-01
The LHC is expected to reach luminosities up to 3000 fb-1 and the innermost layer of the ATLAS upgrade plans to cope with higher occupancy and to decrease the pixel size. 3D-Si sensors are a good candidate for the innermost layer of the ATLAS pixel upgrade since they exhibit good performance under high fluences and the new designs will have smaller pixel size to fulfill the electronics expectations. This paper reports TCAD simulations of the 3D-Si sensors designed at IMB-CNM with non-passing-through columns that are being fabricated for the next innermost layer of the ATLAS pixel upgrade. It shows the charge collection response before and after irradiation, and the response of 3D-Si sensors located at large η angles.
Energy Technology Data Exchange (ETDEWEB)
Courau, T.; Moustafa, S.; Plagne, L.; Poncot, A. [EDF R and D, 1, Av du General de Gaulle, F92141 Clamart cedex (France)
2013-07-01
As part of its activity, EDF R and D is developing a new nuclear core simulation code named COCAGNE. This code relies on DIABOLO, a Simplified PN (SPN) method to compute the neutron flux inside the core for eigenvalue calculations. In order to assess the accuracy of SPN calculations, we have developed DOMINO, a new 3D Cartesian SN solver. The parallel implementation of DOMINO is very efficient and allows to complete an eigenvalue calculation involving around 300 x 10{sup 9} degrees of freedom within a few hours on a single shared-memory supercomputing node. This computation corresponds to a 26-group S{sub 8} 3D PWR core model used to assess the SPN accuracy. At the pin level, the maximal error for the SP{sub 5} DIABOLO fission production rate is lower than 0.2% compared to the S{sub 8} DOMINO reference for this 3D PWR core model. (authors)
Simulations of 3D-Si sensors for the innermost layer of the ATLAS pixel upgrade
Baselga, Marta
2017-01-01
The LHC is expected to reach luminosities up to 3000fb-1 and the innermost layer of the ATLAS upgrade plans to cope with higher occupancy and to decrease the pixel size. 3D-Si sensors are a good candidate for the innermost layer of the ATLAS pixel upgrade since they exhibit good performance under high fluences and the new designs will have smaller pixel size to fulfill the electronics expectations. This paper reports TCAD simulations of the 3D-Si sensors designed at IMB-CNM with non passing-through columns that are being fabricated for the next innermost layer of the ATLAS pixel upgrade, shows the charge collection response before and after irradiation, and the response of 3D-Si sensors located at large $\\eta$ angles.
Jung, Jaewoon; Kobayashi, Chigusa; Imamura, Toshiyuki; Sugita, Yuji
2016-03-01
Three-dimensional Fast Fourier Transform (3D FFT) plays an important role in a wide variety of computer simulations and data analyses, including molecular dynamics (MD) simulations. In this study, we develop hybrid (MPI+OpenMP) parallelization schemes of 3D FFT based on two new volumetric decompositions, mainly for the particle mesh Ewald (PME) calculation in MD simulations. In one scheme, (1d_Alltoall), five all-to-all communications in one dimension are carried out, and in the other, (2d_Alltoall), one two-dimensional all-to-all communication is combined with two all-to-all communications in one dimension. 2d_Alltoall is similar to the conventional volumetric decomposition scheme. We performed benchmark tests of 3D FFT for the systems with different grid sizes using a large number of processors on the K computer in RIKEN AICS. The two schemes show comparable performances, and are better than existing 3D FFTs. The performances of 1d_Alltoall and 2d_Alltoall depend on the supercomputer network system and number of processors in each dimension. There is enough leeway for users to optimize performance for their conditions. In the PME method, short-range real-space interactions as well as long-range reciprocal-space interactions are calculated. Our volumetric decomposition schemes are particularly useful when used in conjunction with the recently developed midpoint cell method for short-range interactions, due to the same decompositions of real and reciprocal spaces. The 1d_Alltoall scheme of 3D FFT takes 4.7 ms to simulate one MD cycle for a virus system containing more than 1 million atoms using 32,768 cores on the K computer.
Numerical Simulation of Injection Molding Cooling Process Based on 3D Surface Model
Institute of Scientific and Technical Information of China (English)
CUIShu-biao; ZHOUHua-min; LIDe-qun
2004-01-01
The design of the coohng system of injection molds directly affects both productivity and the quality of the final part. Using the cooling process CAE system to instruct the mold design, the efficiency and quality of design can be improved greatly. At the same time, it is helpful to confirm the cooling system structure and optimize the process conditions. In this paper, the 3D surface model of mold cavity is used to replace the middle-plane model in the simulation by Boundary Element Method, which break the bottleneck of the application of the injection molding simulation softwares base on the middle-plane model. With the improvements of this paper, a practical and commercial simulation software of injection molding cooling process named as HsCAE3D6.0 is developed.
Digital simulation of 3D turbulence wind field of Sutong Bridge based on measured wind spectra
Institute of Scientific and Technical Information of China (English)
Hao WANG; Zhou-hong ZONG; Ai-qun LI; Teng TONG; Jie NIU; Wen-ping DENG
2012-01-01
Time domain analysis is an essential implement to study the buffeting behavior of long-span bridges for it can consider the non-linear effect which is significant in long-span bridges.The prerequisite of time domain analysis is the accurate description of 3D turbulence winds.In this paper,some hypotheses for simplifying the 3D turbulence simulation of long-span cable-stayed bridges are conducted,considering the structural characteristics.The turbulence wind which is a 3D multivariate stochastic vector process is converted into four independent ID univariate stochastic processes.Based on recorded wind data from structural health monitoring system (SHMS) of the Sutong Bridge,China,the measured spectra expressions are then presented using the nonlinear least-squares fitting method.Turbulence winds at the Sutong Bridge site are simulated based on the spectral representation method and the Fast Fourier transform (FFT) technique,and the relevant results derived from target spectra including measured spectra and recommended spectra are compared.The reliability and accuracy of the presented turbulence simulation method are validated through comparisons between simulated and target spectra (measured and recommended spectra).The obtained turbulence simulations can not only serve further analysis of the buffeting behavior of the Sutong Bridge,but references for structural anti-wind design in adjacent regions.
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.
Large Scale Earth’s Bow Shock with Northern IMF as Simulated by PIC Code in Parallel with MHD Model
Indian Academy of Sciences (India)
Suleiman Baraka
2016-06-01
In this paper, we propose a 3D kinetic model (particle-in-cell, PIC) for the description of the large scale Earth’s bow shock. The proposed version is stable and does not require huge or extensive computer resources. Because PIC simulations work with scaled plasma and field parameters, we also propose to validate our code by comparing its results with the available MHD simulations under same scaled solar wind (SW) and (IMF) conditions. We report new results from the two models. In both codes the Earth’s bow shock position is found to be $\\approx 14.8 R_{{\\rm E}}$ along the Sun–Earth line, and $\\approx 29 R_{{\\rm E}}$ on the dusk side. Those findings are consistent with past in situ observations. Both simulations reproduce the theoretical jump conditions at the shock. However, the PIC code density and temperature distributions are inflated and slightly shifted sunward when compared to the MHD results. Kinetic electron motions and reflected ions upstream may cause this sunward shift. Species distributions in the foreshock region are depicted within the transition of the shock (measured $\\approx$2$c/\\omega_{pi}$ for $ \\Theta_{Bn}=90^{\\circ}$ and $M_{{\\rm MS}} = 4.7 $) and in the downstream. The size of the foot jump in the magnetic field at the shock is measured to be ($1.7 c/ \\omega_{pi} $). In the foreshocked region, the thermal velocity is found equal to 213 km $s^{−1}$ at $15R_{{\\rm E}}$ and is equal to $63 km s^{-1}$ at $12 R_{{\\rm E}}$ (magnetosheath region). Despite the large cell size of the current version of the PIC code, it is powerful to retain macrostructure of planets magnetospheres in very short time, thus it can be used for pedagogical test purposes. It is also likely complementary with MHD to deepen our understanding of the large scale magnetosphere.
Yang, L. M.; Shu, C.; Wang, Y.; Sun, Y.
2016-08-01
The sphere function-based gas kinetic scheme (GKS), which was presented by Shu and his coworkers [23] for simulation of inviscid compressible flows, is extended to simulate 3D viscous incompressible and compressible flows in this work. Firstly, we use certain discrete points to represent the spherical surface in the phase velocity space. Then, integrals along the spherical surface for conservation forms of moments, which are needed to recover 3D Navier-Stokes equations, are approximated by integral quadrature. The basic requirement is that these conservation forms of moments can be exactly satisfied by weighted summation of distribution functions at discrete points. It was found that the integral quadrature by eight discrete points on the spherical surface, which forms the D3Q8 discrete velocity model, can exactly match the integral. In this way, the conservative variables and numerical fluxes can be computed by weighted summation of distribution functions at eight discrete points. That is, the application of complicated formulations resultant from integrals can be replaced by a simple solution process. Several numerical examples including laminar flat plate boundary layer, 3D lid-driven cavity flow, steady flow through a 90° bending square duct, transonic flow around DPW-W1 wing and supersonic flow around NACA0012 airfoil are chosen to validate the proposed scheme. Numerical results demonstrate that the present scheme can provide reasonable numerical results for 3D viscous flows.
Numerical simulation of 3D boundary-driven acoustic streaming in microfluidic devices.
Lei, Junjun; Hill, Martyn; Glynne-Jones, Peter
2014-02-07
This article discusses three-dimensional (3D) boundary-driven streaming in acoustofluidic devices. Firstly, the 3D Rayleigh streaming pattern in a microchannel is simulated and its effect on the movement of microparticles of various sizes is demonstrated. The results obtained from this model show good comparisons with 3D experimental visualisations and demonstrate the fully 3D nature of the acoustic streaming field and the associated acoustophoretic motion of microparticles in acoustofluidic devices. This method is then applied to another acoustofluidic device in order to gain insights into an unusual in-plane streaming pattern. The origin of this streaming has not been fully described and its characteristics cannot be explained from the classical theory of Rayleigh streaming. The simulated in-plane streaming pattern was in good agreement with the experimental visualisation. The mechanism behind it is shown to be related to the active sound intensity field, which supports our previous findings on the mechanism of the in-plane acoustic streaming pattern visualised and modelled in a thin-layered capillary device.
3D thermal modeling of TRISO fuel coupled with neutronic simulation
Energy Technology Data Exchange (ETDEWEB)
Hu, Jianwei [Los Alamos National Laboratory; Uddin, Rizwan [UNIV OF ILLINIOS
2010-01-01
The Very High Temperature Gas Reactor (VHTR) is widely considered as one of the top candidates identified in the Next Generation Nuclear Power-plant (NGNP) Technology Roadmap under the U.S . Depanment of Energy's Generation IV program. TRlSO particle is a common element among different VHTR designs and its performance is critical to the safety and reliability of the whole reactor. A TRISO particle experiences complex thermo-mechanical changes during reactor operation in high temperature and high burnup conditions. TRISO fuel performance analysis requires evaluation of these changes on micro scale. Since most of these changes are temperature dependent, 3D thermal modeling of TRISO fuel is a crucial step of the whole analysis package. In this paper, a 3D numerical thermal model was developed to calculate temperature distribution inside TRISO and pebble under different scenarios. 3D simulation is required because pebbles or TRISOs are always subjected to asymmetric thermal conditions since they are randomly packed together. The numerical model was developed using finite difference method and it was benchmarked against ID analytical results and also results reported from literature. Monte-Carlo models were set up to calculate radial power density profile. Complex convective boundary condition was applied on the pebble outer surface. Three reactors were simulated using this model to calculate temperature distribution under different power levels. Two asymmetric boundary conditions were applied to the pebble to test the 3D capabilities. A gas bubble was hypothesized inside the TRISO kernel and 3D simulation was also carried out under this scenario. Intuition-coherent results were obtained and reported in this paper.
Real-time 3D radiation risk assessment supporting simulation of work in nuclear environments.
Szőke, I; Louka, M N; Bryntesen, T R; Bratteli, J; Edvardsen, S T; RøEitrheim, K K; Bodor, K
2014-06-01
This paper describes the latest developments at the Institute for Energy Technology (IFE) in Norway, in the field of real-time 3D (three-dimensional) radiation risk assessment for the support of work simulation in nuclear environments. 3D computer simulation can greatly facilitate efficient work planning, briefing, and training of workers. It can also support communication within and between work teams, and with advisors, regulators, the media and public, at all the stages of a nuclear installation's lifecycle. Furthermore, it is also a beneficial tool for reviewing current work practices in order to identify possible gaps in procedures, as well as to support the updating of international recommendations, dissemination of experience, and education of the current and future generation of workers.IFE has been involved in research and development into the application of 3D computer simulation and virtual reality (VR) technology to support work in radiological environments in the nuclear sector since the mid 1990s. During this process, two significant software tools have been developed, the VRdose system and the Halden Planner, and a number of publications have been produced to contribute to improving the safety culture in the nuclear industry.This paper describes the radiation risk assessment techniques applied in earlier versions of the VRdose system and the Halden Planner, for visualising radiation fields and calculating dose, and presents new developments towards implementing a flexible and up-to-date dosimetric package in these 3D software tools, based on new developments in the field of radiation protection. The latest versions of these 3D tools are capable of more accurate risk estimation, permit more flexibility via a range of user choices, and are applicable to a wider range of irradiation situations than their predecessors.
GMC Collisions as Triggers of Star Formation. II. 3D Turbulent, Magnetized Simulations
Wu, Benjamin; Nakamura, Fumitaka; Van Loo, Sven; Christie, Duncan; Collins, David
2016-01-01
We investigate giant molecular cloud (GMCs) collisions and their ability to induce gravitational instability and thus star formation. This mechanism may be a major driver of star formation activity in galactic disks. We carry out a series of three dimensional, magnetohydrodynamics (MHD), adaptive mesh refinement (AMR) simulations to study how cloud collisions trigger formation of dense filaments and clumps. Heating and cooling functions are implemented based on photo-dissociation region (PDR) models that span the atomic to molecular transition and can return detailed diagnostic information. The clouds are initialized with supersonic turbulence and a range of magnetic field strengths and orientations. Collisions at various velocities and impact parameters are investigated. Comparing and contrasting colliding and non-colliding cases, we characterize morphologies of dense gas, magnetic field structure, cloud kinematic signatures, and cloud dynamics. We present key observational diagnostics of cloud collisions, e...
The Surface of Stellar Models - Now with more 3D simulations!
Directory of Open Access Journals (Sweden)
Trampedach Regner
2015-01-01
Full Text Available We have constructed a grid of 3D hydrodynamic simulations of deep convective and line-blanketed atmospheres. We have developed a new consistent method for computing and employing T(τ relations from these simulations, as surface boundary conditions for 1D stellar structure models. These 1D models have, in turn, had their mixing-length, α, calibrated against the averaged structure of each of the simulations. Both α and T(τ vary significantly with Teff and log g.
Reactive Flow Modeling of Liquid Explosives via ALE3D/Cheetah Simulations
Energy Technology Data Exchange (ETDEWEB)
Kuo, I W; Bastea, S; Fried, L E
2010-03-10
We carried out reactive flow simulations of liquid explosives such as nitromethane using the hydrodynamic code ALE3D coupled with equations of state and reaction kinetics modeled by the thermochemical code Cheetah. The simulation set-up was chosen to mimic cylinder experiments. For pure unconfined nitromethane we find that the failure diameter and detonation velocity dependence on charge diameter are in agreement with available experimental results. Such simulations are likely to be useful for determining detonability and failure behavior for a wide range of experimental conditions and explosive compounds.
Clementel, N; Kruip, C J H; Icke, V; Gull, T R
2014-01-01
Eta Carinae is an ideal astrophysical laboratory for studying massive binary interactions and evolution, and stellar wind-wind collisions. Recent three-dimensional (3D) simulations set the stage for understanding the highly complex 3D flows in $\\eta$ Car. Observations of different broad high- and low-ionization forbidden emission lines provide an excellent tool to constrain the orientation of the system, the primary's mass-loss rate, and the ionizing flux of the hot secondary. In this work we present the first steps towards generating synthetic observations to compare with available and future HST/STIS data. We present initial results from full 3D radiative transfer simulations of the interacting winds in $\\eta$ Car. We use the SimpleX algorithm to post-process the output from 3D SPH simulations and obtain the ionization fractions of hydrogen and helium assuming three different mass-loss rates for the primary star. The resultant ionization maps of both species constrain the regions where the observed forbidde...
Westerveld, W.J.; Urbach, H.P.; Yousefi, M.
2011-01-01
We present an accurate and fast 3-D simulation scheme for out-of-plane grating couplers, based on 2-D rigorous [finite difference time domain (FDTD)] grating simulations, the effective index method, and the RayleighSommerfeld diffraction formula. In comparison with full 3-D FDTD simulations, the rms
Deca, J.; Divin, A. V.; Wang, X.; Lembege, B.; Markidis, S.; Lapenta, G.; Horanyi, M.
2015-12-01
We present three-dimensional full-kinetic electromagnetic simulations of the solar wind interaction with lunar crustal magnetic anomalies (LMAs). Using the implicit particle-in-cell code iPic3D, we confirm that LMAs may indeed be strong enough to stand off the solar wind from directly impacting the lunar surface forming a mini-magnetosphere, as suggested by spacecraft observations and theory. In contrast to earlier MHD and hybrid simulations, the full-kinetic nature of iPic3D allows to self-consistently investigate space charge effects, and in particular the electron dynamics dominating the near-surface lunar plasma environment. We describe the general mechanism of the interaction of both a horizontal and vertical dipole model embedded just below the lunar surface focussing on the ion and electron kinetic behaviour of the system. It is shown that the configurations are largely dominated by electron motion, because the LMA scale size is small with respect to the gyro-radius of the solar wind ions. The formation of mini-magnetospheres is an electrostatic effect. Additionally, we discuss typical particle trajectories as well as complete particle distribution functions covering thermal and suprathermal energies, within the interaction region and on viable spacecraft altitudes. Our work opens new frontiers of research toward a deeper understanding of LMAs and is ideally suited to be compared with field or particle observations from spacecraft such as Kaguya (SELENE), Lunar Prospector or ARTEMIS. The ability to evaluate the implications for future lunar exploration as well as lunar science in general hinges on a better understanding of LMAs.This research has received funding from the European Commission's FP7 Program with the grant agreement EHEROES (project 284461, www.eheroes.eu). The simulations were conducted on the computational resources provided by the PRACE Tier-0 project 2013091928 (SuperMUC). This research was supported by the Swedish National Space Board
Confocal 3D DNA Cytometry: Assessment of Required Coefficient of Variation by Computer Simulation
Directory of Open Access Journals (Sweden)
Lennert S. Ploeger
2004-01-01
Full Text Available Background: Confocal Laser Scanning Microscopy (CLSM provides the opportunity to perform 3D DNA content measurements on intact cells in thick histological sections. So far, sample size has been limited by the time consuming nature of the technology. Since the power of DNA histograms to resolve different stemlines depends on both the sample size and the coefficient of variation (CV of histogram peaks, interpretation of 3D CLSM DNA histograms might be hampered by both a small sample size and a large CV. The aim of this study was to analyze the required CV for 3D CLSM DNA histograms given a realistic sample size. Methods: By computer simulation, virtual histograms were composed for sample sizes of 20000, 10000, 5000, 1000, and 273 cells and CVs of 30, 25, 20, 15, 10 and 5%. By visual inspection, the histogram quality with respect to resolution of G0/1 and G2/M peaks of a diploid stemline was assessed. Results: As expected, the interpretability of DNA histograms deteriorated with decreasing sample sizes and higher CVs. For CVs of 15% and lower, a clearly bimodal peak pattern with well distinguishable G0/1 and G2/M peaks were still seen at a sample size of 273 cells, which is our current average sample size with 3D CLSM DNA cytometry. Conclusions: For unambiguous interpretation of DNA histograms obtained using 3D CLSM, a CV of at most 15% is tolerable at currently achievable sample sizes. To resolve smaller near diploid stemlines, a CV of 10% or better should be aimed at. With currently available 3D imaging technology, this CV is achievable.
Cosmic-ray pitch-angle scattering in imbalanced MHD turbulence simulations
Weidl, Martin S; Teaca, Bogdan; Schlickeiser, Reinhard
2015-01-01
Pitch-angle scattering rates for cosmic-ray particles in magnetohydrodynamic (MHD) simulations with imbalanced turbulence are calculated for fully evolving electromagnetic turbulence. We compare with theoretical predictions derived from the quasilinear theory of cosmic-ray diffusion for an idealized slab spectrum and demonstrate how cross helicity affects the shape of the pitch-angle diffusion coefficient. Additional simulations in evolving magnetic fields or static field configurations provide evidence that the scattering anisotropy in imbalanced turbulence is not primarily due to coherence with propagating Alfven waves, but an effect of the spatial structure of electric fields in cross-helical MHD turbulence.
3D Kinetic Simulation of Plasma Jet Penetration in Magnetic Field
Galkin, Sergei A.; Bogatu, I. N.; Kim, J. S.
2009-11-01
A high velocity plasmoid penetration through a magnetic barrier is a problem of a great experimental and theoretical interest. Our LSP PIC code 3D fully kinetic numerical simulations of high density (10^16 cm-3) high velocity (30-140 km/sec) plasma jet/bullet, penetrating through the transversal magnetic field, demonstrate three different regimes: reflection by field, penetration by magnetic field expulsion and penetration by magnetic self-polarization. The behavior depends on plasma jet parameters and its composition: hydrogen, carbon (A=12) and C60-fullerene (A=720) plasmas were investigated. The 3D simulation of two plasmoid head-on injections along uniform magnetic field lines is analyzed. Mini rail plasma gun (accelerator) modeling is also presented and discussed.
On 3D simulation of moving objects in a digital earth system
Institute of Scientific and Technical Information of China (English)
2008-01-01
"How do the rescue helicopters find out an optimized path to arrive at the site of a disaster as soon as possible?" or "How are the flight procedures over mountains and plateaus simulated?" and so on.In this paper a script language on spatial moving objects is presented by abstracting 3D spatial moving objects’ behavior when implementing moving objects simulation in 3D digital Earth scene,which is based on a platform of digital China named "ChinaStar".The definition of this script language,its morphology and syntax,its compiling and mediate language generating,and the behavior and state control of spatial moving objects are discussed emphatically.In addition,the language’s applications and implementation are also discussed.
3D COMPUTER SIMULATION FOR LIGNIFICATION OF ANCIENT CHINESE TIMBER BUILDINGS
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
A pioneer research work was carried out by investigators engaged in surveying and mapping for describing ancient Chinese timber buildings by 3D frame graphs w ith a computer.Users can know the structural layers and the assembly process of the se buildings if the frame graphs are processed further with a computer model.Th is can be implemented by computer simulation technique.This technique display t he raw data on the screen of a computer and interactively manage them by combini ng technologies from computer graphics and image processing,multi-media technol ogy,artificial intelligence,highly parallel real-time computation technique an d human behavior science.This paper presents the implementing procedure of ligni fi cation simulation for large-sized wooden buildings as well as 3D dynamic assembl y of these buildings under the 3DS MAX environment.The results from computer sim ulation are also shown in the paper.
Institute of Scientific and Technical Information of China (English)
ZHONG Denghua; TONG Dawei
2009-01-01
Applying stiffness migration method, a 3D finite element mechanical model is established to simulate the excavation and advance processes. By using 3D nonlinear finite element method, the tunnel boring machine (TBM) excavation process is dynamically simulated to analyze the stress and strain field status of surrounding rock and segment. The maximum tensile stress of segment ring caused by tunnel construction mainly lies in arch bottom and presents zonal distribution. The stress increases slightly and limitedly in the course of excavation. The maxi-mum and minimum displacements of segment, manifesting as zonal distribution, distribute in arch bottom and vault respectively. The displacements slightly increase with the advance of TBM and gradually tend to stability.
The Idea and Concept of Metos3D: A Marine Ecosystem Toolkit for Optimization and Simulation in 3D
Piwonski, Jaroslaw
2014-01-01
The simulation and parameter optimization of coupled ocean circulation and ecosystem models in three space dimensions is one of the most challenging tasks in numerical climate research. Here we present a scientific toolkit that aims at supporting researchers by defining clear coupling interfaces, providing state-of-the-art numerical methods for simulation, parallelization and optimization while using only freely available and (to a great extend) platform-independent software. Besides defining a user-friendly coupling interface (API) for marine ecosystem or biogeochemical models, we heavily rely on the Portable, Extensible Toolkit for Scientific computation (PETSc) developed at Argonne Nat. Lab. for a wide variety of parallel linear and non-linear solvers and optimizers. We specifically focus on the usage of matrix-free Newton-Krylov methods for the fast computation of steady periodic solutions, and make use of the Transport Matrix Method (TMM) introduced by Khatiwala et al.
Modeling and 3-D Simulation of Biofilm Dynamics in Aqueous Environment
Wang, Qi
2011-11-01
We present a complex fluid model for biofilms growing in an aqueous environment. The modeling approach represents a new paradigm to develop models for biofilm-environment interaction that can be used to systematically incorporate refined chemical and physiological mechanisms. Special solutions of the model are presented and analyzed. 3-D numerical simulations in aqueous environment with emphasis on biofilm- ambient fluid interaction will be discussed in detail.
hp-finite element method for simulating light scattering from complex 3D structures
Burger, S; Pomplun, J; Herrmann, S; Schmidt, F
2015-01-01
Methods for solving Maxwell's equations are integral part of optical metrology and computational lithography setups. Applications require accurate geometrical resolution, high numerical accuracy and/or low computation times. We present a finite-element based electromagnetic field solver relying on unstructured 3D meshes and adaptive hp-refinement. We apply the method for simulating light scattering off arrays of high aspect-ratio nano-posts and FinFETs.
Nigrin, S.; Armstrong, G. A.; Kranti, A.
2007-09-01
This paper provides a comprehensive analysis of thermal resistance of trench isolated bipolar transistors on SOI substrates based on 3D electro-thermal simulations calibrated to experimental data. The impact of emitter length, width, spacing and number of emitter fingers on thermal resistance is analysed in detail. The results are used to design and optimise transistors with minimum thermal resistance and minimum transistor area.
Depth of field simulation for still digital images using a 3D camera
Directory of Open Access Journals (Sweden)
Omar Alejandro Rodríguez Rosas
2016-11-01
Full Text Available In a world where digital photography is almost ubiquitous, the size of image capturing devices and their lenses limit their capabilities to achieve shallower depths of field for aesthetic purposes. This work proposes a novel approach to simulate this effect using the color and depth images from a 3D camera. Comparative tests yielded results similar to those of a regular lens.
The 3D numerical simulation of waste heat inside the end-pumped DPAL
Hua, Weihong; Yang, Zining; Wang, Hongyan
2012-01-01
The thermal effect produced by quantum defect is an important factor that affects the performance of DPAL. We report on 3D simulation results of temperature distribution inside the alkali gain medium. The results show a high and non-uniform temperature rise under CW pumped condition, and the current models that assume uniform alkali density distribution needs to be modified. A convective cooling scheme should be applied for high power DPALs.
Prototyping Novel Instruments for Fetal Surgery through Virtual Reality Simulation and 3D Printing
2015-01-01
Designing novel medical devices is a complex matter. Involving clinicians as early as possible into the development process is of crucial importance; it helps to shorten the development cycle and increases the likelihood of later acceptance by clinicians. In this paper we show how through a combination of 3D printing and Virtual Reality simulation it is possible to involve clinicians in a very early stage, yet receive concrete quantitative and qualitative information that can shift the design...
Jovian Plasma Torus Interaction with Europa: 3D Hybrid Kinetic Simulation. First results
Lipatov, A. S.; Cooper, J. F.; Paterson, W. R.; Sittler, E. C.; Hartle, R. E.; Simpson, D. G.
2010-01-01
The hybrid kinetic model supports comprehensive simulation of the interaction between different spatial and energetic elements of the Europa-moon-magnetosphere system with respect to variable upstream magnetic field and flux or density distributions of plasma and energetic ions, electrons, and neutral atoms. This capability is critical for improving the interpretation of the existing Europa flyby measurements from the Galileo orbiter mission, and for planning flyby and orbital measurements, (including the surface and atmospheric compositions) for future missions. The simulations are based on recent models of the atmosphere of Europa (Cassidy etal.,2007;Shematovichetal.,2005). In contrast to previous approaches with MHD simulations, the hybrid model allows us to fully take into account the finite gyro radius effect and electron pressure, and to correctly estimate the ion velocity distribution and the fluxes along the magnetic field (assuming an initial Maxwellian velocity distribution for upstream background ions).Non-thermal distributions of upstream plasma will be addressed in future work. Photoionization,electron-impact ionization, charge exchange and collisions between the ions and neutrals are also included in our model. We consider two models for background plasma:(a) with O(++) ions; (b) with O(++) and S(++) ions. The majority of O2 atmosphere is thermal with an extended cold population (Cassidyetal.,2007). A few first simulations already include an induced magnetic dipole; however, several important effects of induced magnetic fields arising from oceanic shell conductivity will be addressed in later work.
Directory of Open Access Journals (Sweden)
S. Gómez
2005-01-01
Full Text Available Se presenta un simulador de sombras vectoriales por radiación solar sobre objetos tridimensionales, SSV3D, una herramienta de computación gráfica desarrollada sobre la plataforma tridimensional del AUTOCAD 2004. El software simula vectorialmente la radiación solar directa, calculando y trazando los contornos de sombra sobre los planos iluminados del modelo 3D evaluado. En el desarrollo de la herramienta se comprobaron los resultados analíticos mediante su comparación con los obtenidos en las fórmulas de una hoja de cálculo, y de los resultados gráficos mediante comparación con las sombras arrojadas por simulación con un heliodón de tecnología francesa y por el Render de AUTOCAD. El simulador SSV3D respondió satisfactoriamente a las necesidades de estudio de sistemas de protección solar en investigaciones desarrolladas anteriormente.SSV3D is presented as a graphic computer tool developed on the three-dimensional platform of AUTOCAD 2004, which simulates direct solar radiation by measuring and vectorial tracing of shadow outlines on illuminated plans of the 3D model evaluated. The analytical results of this tool were tested during its' development by comparing its' results with those obtained in the formula of a calculus sheet, and graphic results were checked comparing these to the shadows obtained by simulation using physical models in a heliodon (French technology and by the Render of AUTOCAD. The SSV3D simulator responded satisfactorily to the requirements for the study of solar protection systems which had been determined in previous research.
Sayah, Abdeljalil; Gijs, Martin A. M.
2016-11-01
We characterise computationally and experimentally a three-dimensional (3D) microfluidic passive mixer for various Reynolds numbers ranging from 1 to 100, corresponding to primary flow rates of 10-870 µl min-1. The 3D mixing channel is composed of multiple curved segments: circular arcs situated in the substrate plane and curved nozzle/diffuser elements normal to the substrate plane. Numerical simulation provides a detailed understanding of the mixing mechanism resulting from the geometrical topology of the mixer. These Comsol software-based simulations reveal the development of two secondary flows perpendicular to the primary flow: a swirling flow resulting from tangential injection of the flow into the nozzle holes and Dean vortices present in the circular arcs. These phenomena are particularly important at a Reynolds number larger than 30, where mixing occurs by chaotic advection. Experimentally, the 3D mixer is fabricated in a monolithic glass substrate by powder blasting machining, exploiting eroding powder beams at various angles of impact with respect to the substrate plane. Experimental mixing was characterised using two coloured dyes, showing nearly perfect mixing for a microfluidic footprint of the order of a few mm2, in good agreement with the simulations.
Simulation of a true-triaxial deformation test on anisotropic gneiss using FLAC3D
Ye, Shenghua; Sehizadeh, Mehdi; Nasseri, Mohammad; Young, Paul
2016-04-01
A series of true-triaxial experiments have been carried out at the University of Toronto's Rock Fracture Dynamics Laboratory. Isotropic pegmatite and gneiss have been used to systematically study the effect of anisotropy on the strength, behaviour and seismic response. Samples were loaded under true-triaxial stress conditions and subjected to complex loading and unloading histories associated with rock deformation around underground openings. The results show expected patterns of weakness from preferentially oriented samples and highlight the importance of unloading history under true-triaxial conditions on the deformation and seismic response of the samples. These tests have been used to validate a synthetic simulation using the Itasca FLAC3D numerical code. The paper describes the FLAC3D simulations of the complex true-triaxial loading and unloading history of the different anisotropic samples. Various parameters were created to describe the physico-mechanical properties of the synthetic rock samples. Foliation planes of preferential orientations with respect to the primary loading direction were added to the synthetic rock samples to reflect the anisotropy of the gneiss. These synthetic rock samples were subjected to the same loading and unloading paths as the real rock samples, and failed in the same mechanism as what was observed from the experiments, and thus it proved the validity of this numerical simulation with FLAC3D.
Meso-Scale Damage Simulation of 3D Braided Composites under Quasi-Static Axial Tension
Zhang, Chao; Mao, Chunjian; Zhou, Yexin
2017-01-01
The microstructure of 3D braided composites is composed of three phases: braiding yarn, matrix and interface. In this paper, a representative unit-cell (RUC) model including these three phases is established. Coupling with the periodical boundary condition, the damage behavior of 3D braided composites under quasi-static axial tension is simulated by using finite element method based on this RUC model. An anisotropic damage model based on Murakami damage theory is proposed to predict the damage evolution of yarns and matrix; a damage-friction combination interface constitutive model is adopted to predict the interface debonding behavior. A user material subroutine (VUMAT) involving these damage models is developed and implemented in the finite element software ABAQUS/Explicit. The whole process of damage evolution of 3D braided composites under quasi-static axial tension with typical braiding angles is simulated, and the damage mechanisms are revealed in detail in the simulation process. The tensile strength properties of the braided composites are predicted from the calculated stress-strain curves. Numerical results agree with the available experiment data and thus validates the proposed damage analysis model. The effects of certain material parameters on the predicted stress-strain responses are also discussed by numerical parameter study.
Forced Reconnection in the Near Magnetotail: Onset and Energy Conversion in PIC and MHD Simulations
Birn, J.; Hesse, Michael
2014-01-01
Using two-dimensional particle-in-cell (PIC) together with magnetohydrodynamic (MHD) Q1 simulations of magnetotail dynamics, we investigate the evolution toward onset of reconnection and the subsequent energy transfer and conversion. In either case, reconnection onset is preceded by a driven phase, during which magnetic flux is added to the tail at the high-latitude boundaries, followed by a relaxation phase, during which the configuration continues to respond to the driving. The boundary deformation leads to the formation of thin embedded current sheets, which are bifurcated in the near tail, converging to a single sheet farther out in the MHD simulations. The thin current sheets in the PIC simulation are carried by electrons and are associated with a strong perpendicular electrostatic field, which may provide a connection to parallel potentials and auroral arcs and an ionospheric signal even prior to the onset of reconnection. The PIC simulation very well satisfies integral entropy conservation (intrinsic to ideal MHD) during this phase, supporting ideal ballooning stability. Eventually, the current intensification leads to the onset of reconnection, the formation and ejection of a plasmoid, and a collapse of the inner tail. The earthward flow shows the characteristics of a dipolarization front: enhancement of Bz, associated with a thin vertical electron current sheet in the PIC simulation. Both MHD and PIC simulations show a dominance of energy conversion from incoming Poynting flux to outgoing enthalpy flux, resulting in heating of the inner tail. Localized Joule dissipation plays only a minor role.
Piwonski, Jaroslaw; Slawig, Thomas
2016-10-01
We designed and implemented a modular software framework for the offline simulation of steady cycles of 3-D marine ecosystem models based on the transport matrix approach. It is intended for parameter optimization and model assessment experiments. We defined a software interface for the coupling of a general class of water column-based biogeochemical models, with six models being part of the package. The framework offers both spin-up/fixed-point iteration and a Jacobian-free Newton method for the computation of steady states. The simulation package has been tested with all six models. The Newton method converged for four models when using standard settings, and for two more complex models after alteration of a solver parameter or the initial guess. Both methods delivered the same steady states (within a reasonable precision) on convergence for all models employed, with the Newton iteration generally operating 6 times faster. The effects on performance of both the biogeochemical and the Newton solver parameters were investigated for one model. A profiling analysis was performed for all models used in this work, demonstrating that the number of tracers had a dominant impact on overall performance. We also implemented a geometry-adapted load balancing procedure which showed close to optimal scalability up to a high number of parallel processors.
The Impact of 3D Data Quality on Improving GNSS Performance Using City Models Initial Simulations
Ellul, C.; Adjrad, M.; Groves, P.
2016-10-01
There is an increasing demand for highly accurate positioning information in urban areas, to support applications such as people and vehicle tracking, real-time air quality detection and navigation. However systems such as GPS typically perform poorly in dense urban areas. A number of authors have made use of 3D city models to enhance accuracy, obtaining good results, but to date the influence of the quality of the 3D city model on these results has not been tested. This paper addresses the following question: how does the quality, and in particular the variation in height, level of generalization and completeness and currency of a 3D dataset, impact the results obtained for the preliminary calculations in a process known as Shadow Matching, which takes into account not only where satellite signals are visible on the street but also where they are predicted to be absent. We describe initial simulations to address this issue, examining the variation in elevation angle - i.e. the angle above which the satellite is visible, for three 3D city models in a test area in London, and note that even within one dataset using different available height values could cause a difference in elevation angle of up to 29°. Missing or extra buildings result in an elevation variation of around 85°. Variations such as these can significantly influence the predicted satellite visibility which will then not correspond to that experienced on the ground, reducing the accuracy of the resulting Shadow Matching process.
An inexpensive underwater mine countermeasures simulator with real-time 3D after action review
Directory of Open Access Journals (Sweden)
Robert Stone
2016-10-01
Full Text Available This paper presents the results of a concept capability demonstration pilot study, the aim of which was to investigate how inexpensive gaming software and hardware technologies could be exploited in the development and evaluation of a simulator prototype for training Royal Navy mine clearance divers, specifically focusing on the detection and accurate reporting of the location and condition of underwater ordnance. The simulator was constructed using the Blender open source 3D modelling toolkit and game engine, and featured not only an interactive 3D editor for underwater scenario generation by instructors, but also a real-time, 3D After Action Review (AAR system for formative assessment and feedback. The simulated scenarios and AAR architecture were based on early human factors observations and briefings conducted at the UK's Defence Diving School (DDS, an organisation that provides basic military diving training for all Royal Navy and Army (Royal Engineers divers. An experimental pilot study was undertaken to determine whether or not basic navigational and mine detection components of diver performance could be improved as a result of exposing participants to the AAR system, delivered between simulated diving scenarios. The results suggest that the provision of AAR was accompanied by significant performance improvements in the positive identification of simulated underwater ordnance (in contrast to non-ordnance objects and on participants' description of their location, their immediate in-water or seabed context and their structural condition. Only marginal improvements were found with participants' navigational performance in terms of their deviation accuracies from a pre-programmed expert search path. Overall, this project contributes to the growing corpus of evidence supporting the development of simulators that demonstrate the value of exploiting open source gaming software and the significance of adopting established games design
Sedimentary basin effects in Seattle, Washington: Ground-motion observations and 3D simulations
Frankel, Arthur; Stephenson, William; Carver, David
2009-01-01
Seismograms of local earthquakes recorded in Seattle exhibit surface waves in the Seattle basin and basin-edge focusing of S waves. Spectral ratios of Swaves and later arrivals at 1 Hz for stiff-soil sites in the Seattle basin show a dependence on the direction to the earthquake, with earthquakes to the south and southwest producing higher average amplification. Earthquakes to the southwest typically produce larger basin surface waves relative to S waves than earthquakes to the north and northwest, probably because of the velocity contrast across the Seattle fault along the southern margin of the Seattle basin. S to P conversions are observed for some events and are likely converted at the bottom of the Seattle basin. We model five earthquakes, including the M 6.8 Nisqually earthquake, using 3D finite-difference simulations accurate up to 1 Hz. The simulations reproduce the observed dependence of amplification on the direction to the earthquake. The simulations generally match the timing and character of basin surface waves observed for many events. The 3D simulation for the Nisqually earth-quake produces focusing of S waves along the southern margin of the Seattle basin near the area in west Seattle that experienced increased chimney damage from the earthquake, similar to the results of the higher-frequency 2D simulation reported by Stephenson et al. (2006). Waveforms from the 3D simulations show reasonable agreement with the data at low frequencies (0.2-0.4 Hz) for the Nisqually earthquake and an M 4.8 deep earthquake west of Seattle.
Large plasmoids in global MHD simulations: Solar wind dependence and ionospheric mapping
Honkonen, Ilja; Palmroth, Minna; Pulkkinen, T.; Janhunen, Pekka
The energy from the solar wind drives magnetospheric dynamics. An important, but the most difficult to measure, factor is the energy released in plasmoids. Plasmoids are large magnetic structures that form in the Earth's magnetotail during substorms, which are the main mecha-nism of extracting and releasing solar wind energy from the magnetosphere. During plasmoid formation the 3-d structure of the magnetotail becomes complicated, with spatially alternating closed and open magnetic topologies. While the formation and the release of plasmoids are unresolved, they are classically thought to detach from the magnetotail at the substorm onset. Using our global magnetohydrodynamic (MHD) simulation GUMICS-4, we investigate how different parameters of the solar wind affect the formation of plasmoids. Specifically we con-centrate on the role of the solar wind magnetic field parameters. We also investigate the solar wind dependence of plasmoid foot points, which are the end points of the plasmoid magnetic field in the ionosphere. Preliminary results suggest that plasmoid formation and plasmoid foot point location in the ionosphere strongly depend on the solar wind magnetic field param-eters. Our work may be of importance when interpreting some observed, but unexplained, ionospheric phenomena. We also present an operational definition of plasmoids, which enables their automatic detection in simulations. The project has received funding from the European Research Council under the European Community's Seventh Framework Programme (FP7/2007-2013) / ERC Starting Grant agree-ment number 200141-QuESpace. The work of IH and MP is supported by the Academy of Finland.
Implementation of Headtracking and 3D Stereo with Unity and VRPN for Computer Simulations
Noyes, Matthew A.
2013-01-01
This paper explores low-cost hardware and software methods to provide depth cues traditionally absent in monocular displays. The use of a VRPN server in conjunction with a Microsoft Kinect and/or Nintendo Wiimote to provide head tracking information to a Unity application, and NVIDIA 3D Vision for retinal disparity support, is discussed. Methods are suggested to implement this technology with NASA's EDGE simulation graphics package, along with potential caveats. Finally, future applications of this technology to astronaut crew training, particularly when combined with an omnidirectional treadmill for virtual locomotion and NASA's ARGOS system for reduced gravity simulation, are discussed.
Mizuno, Yosuke; Lyubarsky, Yuri; ishikawa, Ken-Ichi; Hardee, Philip E.
2010-01-01
We have investigated the development of current-driven (CD) kink instability through three-dimensional relativistic MHD simulations. A static force-free equilibrium helical magnetic configuration is considered in order to study the influence of the initial configuration on the linear and nonlinear evolution of the instability. We found that the initial configuration is strongly distorted but not disrupted by the kink instability. The instability develops as predicted by linear theory. In the non-linear regime the kink amplitude continues to increase up to the terminal simulation time, albeit at different rates, for all but one simulation. The growth rate and nonlinear evolution of the CD kink instability depends moderately on the density profile and strongly on the magnetic pitch profile. The growth rate of the kink mode is reduced in the linear regime by an increase in the magnetic pitch with radius and the non-linear regime is reached at a later time than for constant helical pitch. On the other hand, the growth rate of the kink mode is increased in the linear regime by a decrease in the magnetic pitch with radius and reaches the non-linear regime sooner than the case with constant magnetic pitch. Kink amplitude growth in the non-linear regime for decreasing magnetic pitch leads to a slender helically twisted column wrapped by magnetic field. On the other hand, kink amplitude growth in the non-linear regime nearly ceases for increasing magnetic pitch.
Rise time of proton cut-off energy in 2D and 3D PIC simulations
Babaei, Javad; Londrillo, Pasquale; Mirzanejad, Saeed; Rovelli, Tiziano; Sinigardi, Stefano; Turchetti, Giorgio
2016-01-01
The Target Normal Sheath Acceleration (TNSA) regime for proton acceleration by laser pulses is experimentally consolidated and fairly well understood. However, uncertainties remain in the analysis of particle-in-cell (PIC) simulation results. The energy spectrum is exponential with a cut-off, but the maximum energy depends on the simulation time, following different laws in two and three dimensional (2D, 3D) PIC simulations, so that the determination of an asymptotic value has some arbitrariness. We propose two empirical laws for rise time of the cut-off energy in 2D and 3D PIC simulations, suggested by a model in which the proton acceleration is due to a surface charge distribution on the target rear side. The kinetic energy of the protons that we obtain follows two distinct laws, which appear to be nicely satisfied by PIC simulations. The laws depend on two parameters: the scaling time, at which the energy starts to rise, and the asymptotic cut-off energy. The values of the cut-off energy, obtained by fitti...
Simulation of the impact of 3-D porosity distribution in metallic U-10Zr fuels
Yun, Di; Yacout, Abdellatif M.; Stan, Marius; Bauer, Theodore H.; Wright, Arthur E.
2014-05-01
Evolution of porosity generated in metallic U-Zr fuel irradiated in fast spectrum reactors leads to changes in fuel properties and impacts important phenomena such as heat transport and constituent redistribution. The porosity is generated as a result of the accumulation of fission gases and is affected by the possible bond sodium infiltration into the fuel. Typically, the impact of porosity development on properties, such as thermal conductivity, is accounted for through empirical correlations that are dependent on porosity and infiltrated sodium fractions. Currently available simulation tools make it possible to take into account fuel 3-D porosity distributions, potentially eliminating the need for such correlations. This development allows for a more realistic representation of the porosity evolution in metallic fuel and creates a framework for truly mechanistic fuel development models. In this work, COMSOL multi-physics simulation platform is used to model 3-D porosity distributions and simulate heat transport in metallic U-10Zr fuel. Available experimental data regarding microstructural evolution of fuel that was irradiated in EBR-II and associated phase stability information are used to guide the simulation. The impact of changes in porosity characteristics on material properties is estimated and the results are compared with calculated temperature distributions. The simulations demonstrate the developed capability and importance of accounting for detailed porosity distribution features for accurate fuel performance evaluation.
Full Core 3-D Simulation of a Partial MOX LWR Core
Energy Technology Data Exchange (ETDEWEB)
S. Bays; W. Skerjanc; M. Pope
2009-05-01
A comparative analysis and comparison of results obtained between 2-D lattice calculations and 3-D full core nodal calculations, in the frame of MOX fuel design, was conducted. This study revealed a set of advantages and disadvantages, with respect to each method, which can be used to guide the level of accuracy desired for future fuel and fuel cycle calculations. For the purpose of isotopic generation for fuel cycle analyses, the approach of using a 2-D lattice code (i.e., fuel assembly in infinite lattice) gave reasonable predictions of uranium and plutonium isotope concentrations at the predicted 3-D core simulation batch average discharge burnup. However, it was found that the 2-D lattice calculation can under-predict the power of pins located along a shared edge between MOX and UO2 by as much as 20%. In this analysis, this error did not occur in the peak pin. However, this was a coincidence and does not rule out the possibility that the peak pin could occur in a lattice position with high calculation uncertainty in future un-optimized studies. Another important consideration in realistic fuel design is the prediction of the peak axial burnup and neutron fluence. The use of 3-D core simulation gave peak burnup conditions, at the pellet level, to be approximately 1.4 times greater than what can be predicted using back-of-the-envelope assumptions of average specific power and irradiation time.
Lorentz boosted frame simulation of Laser wakefield acceleration in quasi-3D geometry
Yu, Peicheng; Davidson, Asher; Tableman, Adam; Dalichaouch, Thamine; Meyers, Michael D; Tsung, Frank S; Decyk, Viktor K; Fiuza, Frederico; Vieira, Jorge; Fonseca, Ricardo A; Lu, Wei; Silva, Luis O; Mori, Warren B
2015-01-01
When modeling laser wakefield acceleration (LWFA) using the particle-in-cell (PIC) algorithm in a Lorentz boosted frame, the plasma is drifting relativistically at $\\beta_b c$ towards the laser, which can lead to a computational speedup of $\\sim \\gamma_b^2=(1-\\beta_b^2)^{-1}$. Meanwhile, when LWFA is modeled in the quasi-3D geometry in which the electromagnetic fields and current are decomposed into a limited number of azimuthal harmonics, speedups are achieved by modeling three dimensional problems with the computation load on the order of two dimensional $r-z$ simulations. Here, we describe how to combine the speed ups from the Lorentz boosted frame and quasi-3D algorithms. The key to the combination is the use of a hybrid Yee-FFT solver in the quasi-3D geometry that can be used to effectively eliminate the Numerical Cerenkov Instability (NCI) that inevitably arises in a Lorentz boosted frame due to the unphysical coupling of Langmuir modes and EM modes of the relativistically drifting plasma in these simul...
Simulation of 3D chip shaping of aluminum alloy 7075 in milling processes
Institute of Scientific and Technical Information of China (English)
DONG Hui-yue; KE Ying-lin
2005-01-01
By adopting an equivalent geometry model of machining process and considering thermo-plastic properties of the work material, a finite element method(FEM) to study oblique milling process of aluminum alloy with a double-edge tool was presented. In the FEM, shear flow stress was determined by material test. Re-meshing technology was used to represent chip separation process. Comparing the predicted cutting forces with the measured forces shows the 3D FEM is reasonable. Using this FEM, chip forming process and temperature distribution were predicted. Chips obtained by the 3D FEM are in spiral shape and are similar to the experimental ones. Distribution and change trend of temperature in the tool and chip indicate that contact length between tool rake face and chip is extending as tool moving forward. These results confirm the capability of FEM simulation in predicting chip flow and selecting optimal tool.
3D anisotropy simulation of dendrites growth with phase field method
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
The anisotropy problem of 3D phase-field model was studied,and various degrees of anisotropy were simulated by numerical calculation method.The results show that with the change of interface anisotropy coefficients,from smooth transition to the appearance of angle,equilibrium crystals shape morphology has a critical value,and 3D critical value is 0.3.The growth of dendrites is stable and the interface is smooth when it is less than critical value;the interface is unstable,rolling edge appears and the growth is discontinuous when it is more than critical value.With the increase of anisotropy coefficients,the dendrites grow faster under the same condition.
Anomalous Surface Deformation of Sapphire Clarified by 3D-FEM Simulation of the Nanoindentation
Nowak, Roman; Manninen, Timo; Li, Chunliang; Heiskanen, Kari; Hannula, Simo-Pekka; Lindroos, Veikko; Soga, Tetsuo; Yoshida, Fusahito
This work clarifies the origin of anomalous surface deformation reflected by peculiar surface patterns around indentation impressions on various crystallographic planes of sapphire. The three-dimensional finite element simulation (3D-FEM) of nanoindentation in Al2O3 crystal allowed the authors to localize the regions in which various kinds of twinning and slip are most prone to be activated. The work provides a novel approach to the “hardness anisotropy”, which was modeled so far using a modified uniaxial-stress approximation of this essentially 3D, non-isotropic contact problem. The calculated results enabled the authors to unravel the asymmetric surface deformation detected on prismatic planes by the high-resolution microscopy, which cannot be explained using simple crystallographic considerations.
3D Finite Volume Simulation of Accretion Discs with Spiral Shocks
Makita, M; Makita, Makoto; Matsuda, Takuya
1998-01-01
We perform 2D and 3D numerical simulations of an accretion disc in a close binary system using the Simplified Flux vector Splitting (SFS) finite volume method. In our calculations, gas is assumed to be the ideal one, and we calculate the cases with gamma=1.01, 1.05, 1.1 and 1.2. The mass ratio of the mass losing star to the mass accreting star is unity. Our results show that spiral shocks are formed on the accretion disc in all cases. In 2D calculations we find that the smaller gamma is, the more tightly the spiral winds. We observe this trend in 3D calculations as well in somewhat weaker sense.
Numerical simulations of self-propelled swimming of 3D bionic fish school
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
Numerical simulations of self-propelled swimming of a three dimensional bionic fish and fish school in a viscous fluid are carried out. This is done with the assistance of a parallel software package produced for 3D moving boundary problems. This computational fluid dynamics package combines the adaptive multi-grid finite volume method, the immersed boundary method and VOF (volume of fluid) method. By using the package results of the self-propelled swimming of a 3D bionic fish and fish school in a vis- cous fluid are obtained. With comparison to the existing experimental measurements of living fishes, the predicted structure of vortical wakes is in good agreement with the measurements.
Energy Technology Data Exchange (ETDEWEB)
Young, R. P.; Collins, D.; Hazzard, J.; Heath, A. [Department of Earth Sciences, Liverpool University, 4 Brownlow street, UK-0 L69 3GP Liverpool (United Kingdom); Pettitt, W.; Baker, C. [Applied Seismology Consultants LTD, 10 Belmont, Shropshire, UK-S41 ITE Shrewsbury (United Kingdom); Billaux, D.; Cundall, P.; Potyondy, D.; Dedecker, F. [Itasca Consultants S.A., Centre Scientifique A. Moiroux, 64, chemin des Mouilles, F69130 Ecully (France); Svemar, C. [Svensk Karnbranslemantering AB, SKB, Aspo Hard Rock Laboratory, PL 300, S-57295 Figeholm (Sweden); Lebon, P. [ANDRA, Parc de la Croix Blanche, 7, rue Jean Monnet, F-92298 Chatenay-Malabry (France)
2004-07-01
This paper presents current results from work performed within the European Commission project SAFETI. The main objective of SAFETI is to develop and test an innovative 3D numerical modelling procedure that will enable the 3-D simulation of nuclear waste repositories in rock. The modelling code is called AC/DC (Adaptive Continuum/ Dis-Continuum) and is partially based on Itasca Consulting Group's Particle Flow Code (PFC). Results are presented from the laboratory validation study where algorithms and procedures have been developed and tested to allow accurate 'Models for Rock' to be produced. Preliminary results are also presented on the use of AC/DC with parallel processors and adaptive logic. During the final year of the project a detailed model of the Prototype Repository Experiment at SKB's Hard Rock Laboratory will be produced using up to 128 processors on the parallel super computing facility at Liverpool University. (authors)
Li, Zheng; Zhang, Yuwen
2016-01-01
Three-dimensional melting problems are investigated numerically with Lattice Boltzmann method (LBM). Regarding algorithm's accuracy and stability, Multiple-Relaxation-Time (MRT) models are employed to simplify the collision term in LBM. Temperature and velocity fields are solved with double distribution functions, respectively. 3-D melting problems are solved with double MRT models for the first time in this article. The key point for the numerical simulation of a melting problem is the methods to obtain the location of the melting front and this article uses interfacial tracking method. The interfacial tracking method combines advantages of both deforming and fixed grid approaches. The location of the melting front was obtained by calculating the energy balance at the solid-liquid interface. Various 3-D conduction controlled melting problems are solved firstly to verify the numerical method. Liquid fraction tendency and temperature distribution obtained from numerical methods agree with the analytical result...
The current status of the development of the technology on 3D computer simulation in Japan
Energy Technology Data Exchange (ETDEWEB)
Kim, Hee Reyoung; Park, Seung Kook; Chung, Un Soo; Jung, Ki Jung
2002-05-01
The development background and property of the COSIDA, which is the 3D computer simulation system for the analysis on the dismantling procedure of the nuclear facilities in Japan was reviewed. The function of the visualization on the work area, Kinematics analysis and dismantling scenario analysis, which are the sub systems of the COSIDA, has been investigated. The physical, geometrical and radiological properties were modelled in 2D or 3D in the sub system of the visualization of the work area. In the sub system of the kinematics analysis, the command set on the basic work procedure for the control of the motion of the models at a cyber space was driven. The suitability of the command set was estimated by the application of COSIDA to the programming on the motion of the remote dismantling tools for dismantling the components of the nuclear facilities at cyber space.
Application of FUN3D Solver for Aeroacoustics Simulation of a Nose Landing Gear Configuration
Vatsa, Veer N.; Lockard, David P.; Khorrami, Mehdi R.
2011-01-01
Numerical simulations have been performed for a nose landing gear configuration corresponding to the experimental tests conducted in the Basic Aerodynamic Research Tunnel at NASA Langley Research Center. A widely used unstructured grid code, FUN3D, is examined for solving the unsteady flow field associated with this configuration. A series of successively finer unstructured grids has been generated to assess the effect of grid refinement. Solutions have been obtained on purely tetrahedral grids as well as mixed element grids using hybrid RANS/LES turbulence models. The agreement of FUN3D solutions with experimental data on the same size mesh is better on mixed element grids compared to pure tetrahedral grids, and in general improves with grid refinement.
Directory of Open Access Journals (Sweden)
Hoffmann Alex C.
2013-05-01
Full Text Available Particle tracks in a hydrocyclone generated both experimentally by positron emission particle tracking (PEPT and numerically with Eulerian-Lagranian CFD have been studied and compared. A hydrocyclone with a cylinder-on-cone design was used in this study, the geometries used in the CFD simulations and in the experiments being identical. It is shown that it is possible to track a fast-moving particle in a hydrocyclone using PEPT with high temporal and spatial resolutions. The numerical 3-D particle trajectories were generated using the Large Eddy Simulation (LES turbulence model for the fluid and Lagrangian particle tracking for the particles. The behaviors of the particles were analyzed in detail and were found to be consistent between experiments and CFD simulations. The tracks of the particles are discussed and related to the fluid flow field visualized in the CFD simulations using the cross-sectional static pressure distribution.
Novel 3D/VR interactive environment for MD simulations, visualization and analysis.
Doblack, Benjamin N; Allis, Tim; Dávila, Lilian P
2014-12-18
The increasing development of computing (hardware and software) in the last decades has impacted scientific research in many fields including materials science, biology, chemistry and physics among many others. A new computational system for the accurate and fast simulation and 3D/VR visualization of nanostructures is presented here, using the open-source molecular dynamics (MD) computer program LAMMPS. This alternative computational method uses modern graphics processors, NVIDIA CUDA technology and specialized scientific codes to overcome processing speed barriers common to traditional computing methods. In conjunction with a virtual reality system used to model materials, this enhancement allows the addition of accelerated MD simulation capability. The motivation is to provide a novel research environment which simultaneously allows visualization, simulation, modeling and analysis. The research goal is to investigate the structure and properties of inorganic nanostructures (e.g., silica glass nanosprings) under different conditions using this innovative computational system. The work presented outlines a description of the 3D/VR Visualization System and basic components, an overview of important considerations such as the physical environment, details on the setup and use of the novel system, a general procedure for the accelerated MD enhancement, technical information, and relevant remarks. The impact of this work is the creation of a unique computational system combining nanoscale materials simulation, visualization and interactivity in a virtual environment, which is both a research and teaching instrument at UC Merced.
Multiple-mode Lamb wave scattering simulations using 3D elastodynamic finite integration technique.
Leckey, Cara A C; Rogge, Matthew D; Miller, Corey A; Hinders, Mark K
2012-02-01
We have implemented three-dimensional (3D) elastodynamic finite integration technique (EFIT) simulations to model Lamb wave scattering for two flaw-types in an aircraft-grade aluminum plate, a rounded rectangle flat-bottom hole and a disbond of the same shape. The plate thickness and flaws explored in this work include frequency-thickness regions where several Lamb wave modes exist and sometimes overlap in phase and/or group velocity. For the case of the flat-bottom hole the depth was incrementally increased to explore progressive changes in multiple-mode Lamb wave scattering due to the damage. The flat-bottom hole simulation results have been compared to experimental data and are shown to provide key insight for this well-defined experimental case by explaining unexpected results in experimental waveforms. For the rounded rectangle disbond flaw, which would be difficult to implement experimentally, we found that Lamb wave behavior differed significantly from the flat-bottom hole flaw. Most of the literature in this field is restricted to low frequency-thickness regions due to difficulties in interpreting data when multiple modes exist. We found that benchmarked 3D EFIT simulations can yield an understanding of scattering behavior for these higher frequency-thickness regions and in cases that would be difficult to set up experimentally. Additionally, our results show that 2D simulations would not have been sufficient for modeling the complicated scattering that occurred.
Magnetospheric Magnetic Reconnection with Southward IMF by a 3D EMPM Simulation
Nishikawa, K.-I.; Yan, X. Y.; Cai, D. S.; Lembege, B.
2004-01-01
We report our new simulation results on magnetospheric magnetic reconnection with southward IMF using a 3D EMPM model, with greater resolution and more particles using the parallelized 3D HPF TRISTAN code on VPP5000 supercomputer. Main parameters used in the new simulation are: domain size is 215 x 145 x 145, grid size = 0.5 Earth radius, initial particle number is 16 per cell, the IMF is southward. Arrival of southward IMF will cause reconnection in the magnetopause, thus allowing particles to enter into the inner magnetosphere. Sunward and tailward high particle flow are observed by satellites, and these phenomena are also observed in the simulation near the neutral line (X line) of the near-Earth magnetotail. This high particle flow goes along with the reconnected island. The magnetic reconnection process contributes to direct plasma entry between the magnetosheath to the inner magnetosphere and plasma sheet, in which the entry process eats the magnetosheath plasma to plasma sheet temperatures. We investigate magnetic, electric fields, density, and current during this magnetic reconnection with southward IMF. Further investigation with this simulation will provide insight into unsolved problems, such as the triggering of storms and substorms, and the storm-substorm relationship. New results will be presented at the meeting.
3D Simulation of Dam-break effect on a Solid Wall using Smoothed Particle Hydrodynamics
Suprijadi,; Naa, Christian; Putra, Anggy Trisnawan
2013-01-01
Dam is built for water supply, water flow or flooding control and electricity energy storage, but in other hand, dam is one of the most dangerous natural disaster in many countries including in Indonesia. The impact of dam break in neighbour area and is huge and many flooding in remote area, as happen in Dam Situ Gintung in Tangerang (close to Jakarta) in 2009. Smoothed Particle Hydrodynamics (SPH), is one of numerical method based on Lagrangian grid which is ap- plied in astrophysical simulation may be used to solve the simulation on dam break effect. The development of SPH methods become alternative methods to solving Navier Stokes equation, which is main key in fluid dynamic simulation. In this paper, SPH is developed for supporting solid par- ticles in use for 3D dam break effect (3D-DBE) simulation. Solid particle have been treated same as fluid particles with additional calculation for converting gained position became translation and rotation of solid object in a whole body. With this capability, the r...
Water flow prediction for Membranes using 3D simulations with detailed morphology
Shi, Meixia
2015-04-01
The membrane morphology significantly influences membrane performance. For osmotically driven membrane processes, the morphology strongly affects the internal concentration polarization. Different membrane morphologies were generated by simulation and their influence on membrane performance was studied, using a 3D model. The simulation results were experimentally validated for two classical phase-inversion membrane morphologies: sponge- and finger-like structures. Membrane porosity and scanning electron microscopy image information were used as model input. The permeance results from the simulation fit well the experimentally measured permeances. Water permeances were predicted for different kinds of finger-like cavity membranes with different finger-like cavity lengths and various finger-like cavity sets, as well as for membranes with cylindrical cavities. The results provide realistic information on how to increase water permeance, and also illustrate that membrane’s complete morphology is important for the accurate water permeance evaluation. Evaluations only based on porosity might be misleading, and the new 3D simulation approach gives a more realistic representation.
Numerical simulation study of disk MHD generator for nonequilibrium plasma (NPG) system
Energy Technology Data Exchange (ETDEWEB)
Tsunoda, Kazumi [Shibaura Institute of Technology, Tokyo (Japan); Harada, Nob [Nagaoka Univ. of Technology (Japan)
1995-12-31
Design and performance prediction of a disk-shaped magnetohydrodynamic (MHD) generator, which is applied to the nonequilibrium plasma generator (NPG) system, have been carried out by means of a quasi-one-dimensional numerical simulation. The calculations have been performed for generator with constant height which is planned to be used for NPG-MHD disk generator pulse power demonstration. A maximum enthalpy extraction ratio obtained from the present calculation reached up to 20%, and, in this case, the electron temperature of working plasma fluctuated in the unstable regime against ionization instability. Taking into account this phenomenon, in order to obtain much higher generator performance, the MHD channel, in which electron temperature was kept at 5000 K, was designed. With this channel, enthalpy extraction ratio of 40% and output power of 7.2 MW were achieved without major modification of the supersonic nozzle, the inlet swirl vanes and the configuration of magnet system.
Klimeck, Gerhard
2001-03-01
The quantum mechanical functionality of commercially pursued heterostructure devices such as resonant tunneling diodes (RTDs), quantum well infrared photodetectors, and quantum well lasers are enabled by material variations on an atomic scale. The creation of these heterostructure devices is realized in a vast design space of material compositions, layer thicknesses and doping profiles. The full experimental exploration of this design space is unfeasible and a reliable design tool is needed. The Nanoelectronic Modeling tool (NEMO) is one of the first commercial grade attempts for such a modeling tool. NEMO was developed as a general-purpose quantum mechanics-based 1-D device design and analysis tool from 1993-97 by the Central Research Laboratory of Texas Instruments (later Raytheon Systems). NEMO enables(R. Lake, G. Klimeck, R. C. Bowen, and D. Jovanovic, J. Appl. Phys. 81), 7845 (1997). the fundamentally sound inclusion of the required(G. Klimeck et al.), in the 1997 55th Annual Device Research Conference Digest, (IEEE, NJ, 1997), p. 92^,(R. C. Bowen et al.), J. Appl. Phys 81, 3207 (1997). physics: bandstructure, scattering, and charge self-consistency based on the non-equilibrium Green function approach. A new class of devices which require full 3-D quantum mechanics based models is starting to emerge: quantum dots, or in general semiconductor based deca-nano devices. We are currently building a 3-D modeling tool based on NEMO to include the important physics to understand electronic stated in such superscaled structures. This presentation will overview various facets of the NEMO 1-D tool such electron transport physics in RTDs, numerical technology, software engineering and graphical user interface. The lessons learned from that work are now entering the NEMO 3-D development and first results using the NEMO 3-D prototype will be shown. More information about the publically available NEMO 1-D executables can be found at http://hpc.jpl.nasa.gov/ PEP/gekco/nemo
High fidelity studies of exploding foil initiator bridges, Part 3: ALEGRA MHD simulations
Neal, William; Garasi, Christopher
2017-01-01
Simulations of high voltage detonators, such as Exploding Bridgewire (EBW) and Exploding Foil Initiators (EFI), have historically been simple, often empirical, one-dimensional models capable of predicting parameters such as current, voltage, and in the case of EFIs, flyer velocity. Experimental methods have correspondingly generally been limited to the same parameters. With the advent of complex, first principles magnetohydrodynamic codes such as ALEGRA and ALE-MHD, it is now possible to simulate these components in three dimensions, and predict a much greater range of parameters than before. A significant improvement in experimental capability was therefore required to ensure these simulations could be adequately verified. In this third paper of a three part study, the experimental results presented in part 2 are compared against 3-dimensional MHD simulations. This improved experimental capability, along with advanced simulations, offer an opportunity to gain a greater understanding of the processes behind the functioning of EBW and EFI detonators.
Energy Technology Data Exchange (ETDEWEB)
2016-06-20
AE3D solves for the shear Alfven eigenmodes and eigenfrequencies in a torodal magnetic fusion confinement device. The configuration can be either 2D (e.g. tokamak, reversed field pinch) or 3D (e.g. stellarator, helical reversed field pinch, tokamak with ripple). The equations solved are based on a reduced MHD model and sound wave coupling effects are not currently included.
Institute of Scientific and Technical Information of China (English)
吴开腾; 宁建国
2003-01-01
A numerical method is presented that simulates 3D explosive field problems. A code MMIC3D using this method can be used to simulate the propagation and reflected effects of all kinds of rigid boundaries to shock waves produced by an explosive source. These numerical results indicate that the code MMIC3D has the ability in computing cases such as 3D shock waves produced by air explosion, vortex region of the shock wave, the Mach wave, and reflected waves behind rigid boundaries.
Recent Developments in the VISRAD 3-D Target Design and Radiation Simulation Code
Macfarlane, Joseph; Woodruff, P.; Golovkin, I.
2011-10-01
The 3-D view factor code VISRAD is widely used in designing HEDP experiments at major laser and pulsed-power facilities, including NIF, OMEGA, OMEGA-EP, ORION, Z, and PLX. It simulates target designs by generating a 3-D grid of surface elements, utilizing a variety of 3-D primitives and surface removal algorithms, and can be used to compute the radiation flux throughout the surface element grid by computing element-to-element view factors and solving power balance equations. Target set-up and beam pointing are facilitated by allowing users to specify positions and angular orientations using a variety of coordinates systems (e . g . , that of any laser beam, target component, or diagnostic port). Analytic modeling for laser beam spatial profiles for OMEGA DPPs and NIF CPPs is used to compute laser intensity profiles throughout the grid of surface elements. VISRAD includes a variety of user-friendly graphics for setting up targets and displaying results, can readily display views from any point in space, and can be used to generate image sequences for animations. We will discuss recent improvements to the software package and plans for future developments.
Characterizing the propagation of gravity waves in 3D nonlinear simulations of solar-like stars
Alvan, L; Brun, A S; Mathis, S; Garcia, R A
2015-01-01
The revolution of helio- and asteroseismology provides access to the detailed properties of stellar interiors by studying the star's oscillation modes. Among them, gravity (g) modes are formed by constructive interferences between progressive internal gravity waves (IGWs), propagating in stellar radiative zones. Our new 3D nonlinear simulations of the interior of a solar-like star allows us to study the excitation, propagation, and dissipation of these waves. The aim of this article is to clarify our understanding of the behavior of IGWs in a 3D radiative zone and to provide a clear overview of their properties. We use a method of frequency filtering that reveals the path of {individual} gravity waves of different frequencies in the radiative zone. We are able to identify the region of propagation of different waves in 2D and 3D, to compare them to the linear raytracing theory and to distinguish between propagative and standing waves (g modes). We also show that the energy carried by waves is distributed in d...
Numerical Simulations of Flow in a 3-D Supersonic Intake at High Mach Numbers
Directory of Open Access Journals (Sweden)
R. Sivakumar
2006-10-01
Full Text Available Numerical simulations of the compressible, 3-D non reacting flow in the engine inlet sectionof a concept hypersonic air-breathing vehicle are presented. These simulations have been carriedout using FLUENT. For all the results reported, the mesh has been refined to achieve areaaveragedwall y+ about 105. Mass flow rate through the intake and stagnation pressure recoveryare used to compare the performance at various angles of attack. The calculations are able topredict the mode of air-intake operation (critical and subcritical for different angles of attack.Flow distortion at the intake for various angles of attack is also calculated and discussed. Thenumerical results are validated by simulating the flow through a 2-D mixed compression hypersonicintake model and comparing with the experimental data.
Simulating Growth Kinetics in a Data-Parallel 3D Lattice Photobioreactor
Directory of Open Access Journals (Sweden)
A. V. Husselmann
2013-01-01
Full Text Available Though there have been many attempts to address growth kinetics in algal photobioreactors, surprisingly little have attempted an agent-based modelling (ABM approach. ABM has been heralded as a method of practical scientific inquiry into systems of a complex nature and has been applied liberally in a range of disciplines including ecology, physics, social science, and microbiology with special emphasis on pathogenic bacterial growth. We bring together agent-based simulation with the Photosynthetic Factory (PSF model, as well as certain key bioreactor characteristics in a visual 3D, parallel computing fashion. Despite being at small scale, the simulation gives excellent visual cues on the dynamics of such a reactor, and we further investigate the model in a variety of ways. Our parallel implementation on graphical processing units of the simulation provides key advantages, which we also briefly discuss. We also provide some performance data, along with particular effort in visualisation, using volumetric and isosurface rendering.
Kuznetsov, Alexey A; Fleishman, Gregory D
2011-01-01
Microwave emission of solar flares is formed primarily by incoherent gyrosynchrotron radiation generated by accelerated electrons in coronal magnetic loops. The resulting emission depends on many factors, including pitch-angle distribution of the emitting electrons and the source geometry. In this work, we perform systematic simulations of solar microwave emission using recently developed tools (GS Simulator and fast gyrosynchrotron codes) capable of simulating maps of radio brightness and polarization as well as spatially resolved emission spectra. A 3D model of a symmetric dipole magnetic loop is used. We compare the emission from isotropic and anisotropic (of loss-cone type) electron distributions. We also investigate effects caused by inhomogeneous distribution of the emitting particles along the loop. It is found that effect of the adopted moderate electron anisotropy is the most pronounced near the footpoints and it also depends strongly on the loop orientation. Concentration of the emitting particles a...
Detecting drug use in adolescents using a 3D simulation program
Directory of Open Access Journals (Sweden)
Luis Iribarne
2010-11-01
Full Text Available This work presents a new 3D simulation program, called MiiSchool, and its application to the detection of problem behaviours appearing in school settings. We begin by describing some of the main features of the Mii School program. Then, we present the results of a study in which adolescents responded to Mii School simulations involving the consumption of alcoholic drinks, cigarettes, cannabis, cocaine, and MDMA (ecstasy. We established a“risk profile” based on the observed response patterns. We also present results concerning user satisfaction with the program and the extent to which users felt that the simulated scenes were realistic. Lastly, we discuss the usefulness of Mii School as a tool for assessing drug use in school settings.
hp-HGS strategy for inverse 3D DC resistivity logging measurement simulations
Gajda-Zaǵorska, Ewa
2012-06-02
In this paper we present a twin adaptive strategy hp-HGS for solving inverse problems related to 3D DC borehole resistivity measurement simulations. The term “simulation of measurements” is widely used by the geophysical community. A quantity of interest, voltage, is measured at a receiver electrode located in the logging instrument. We use the self-adaptive goal-oriented hp-Finite Element Method (hp-FEM) computer simulations of the process of measurements in deviated wells (when the angle between the borehole and formation layers are < 90 deg). We also employ the hierarchical genetic search (HGS) algorithm to solve the inverse problem. Each individual in the population represents a single conﬁguration of the formation layers. The evaluation of the individual is performed by solving the direct problem by means of the hp-FEM algorithm and by comparison with measured logging curve. We conclude the paper with some discussion on the parallelization of the algorithm.
Institute of Scientific and Technical Information of China (English)
2008-01-01
Based on the potential flow theory, the vortex ring is introduced to simulate the toroidal bubble, and the boundary element method is applied to simulate the evo- lution of the bubble. Elastic-plasticity of structure being taken into account, the interaction between the bubble and the elastic-plastic structure is computed by combining the boundary element method (BEM) and the finite element method (FEM), and a corresponding 3D computing program is developed. This program is used to simulate the three-dimensional bubble dynamics in free field, near wall and near the elastic-plastic structure, and the numerical results are compared with the existing experimental results. The error is within 10%. The effects of different boundaries upon the bubble dynamics are presented by studying the bubble dy- namics near different boundaries.
Virtual experimentation through 3D full-loop simulation of a circulating fluidized bed
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
Eulerian granular multiphase model with a drag coefficient correction based on the energy-minimization multi-male (EMMS) model was used to simulate a semi-industry scale circulating fiuidized bed (CFB).Three-dimensional(3D), time-dependent simulation of a full-loop CFB revealed that the axial profiles of cross-sectionally averaged solid volume fraction,and the radial profiles of solid axial velocity and solid volume fraction were in reasonable agreement with experimental data.Based on this agreement,database derived from experiments not yet accomplished was replenished with such simulations, and fluid regime diagrams and pressure balance around the CFB loop were derived accordingly. This work presents an integrated viewpoint on CFB and unfolds a fresh paradigm fur CFB modeling, which can be expected to help resolve certain issues long in dispute but hard for experiments.
pF3D Simulations of SBS and SRS in NIF Hohlraum Experiments
Langer, Steven; Strozzi, David; Amendt, Peter; Chapman, Thomas; Hopkins, Laura; Kritcher, Andrea; Sepke, Scott
2016-10-01
We present simulations of stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS) for NIF experiments using high foot pulses in cylindrical hohlraums and for low foot pulses in rugby-shaped hohlraums. We use pF3D, a massively-parallel, paraxial-envelope laser plasma interaction code, with plasma profiles obtained from the radiation-hydrodynamics codes Lasnex and HYDRA. We compare the simulations to experimental data for SBS and SRS power and spectrum. We also show simulated SRS and SBS intensities at the target chamber wall and report the fraction of the backscattered light that passes through and misses the lenses. Work performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344. Release number LLNL-ABS-697482.
RF study and 3-D simulations of a side-coupling thermionic RF-gun
Rimjaem, S.; Kusoljariyakul, K.; Thongbai, C.
2014-02-01
A thermionic RF-gun for generating ultra-short electron bunches was optimized, developed and used as a source at a linac-based THz radiation research laboratory of the Plasma and Beam Physics Research Facility, Chiang Mai University, Thailand. The RF-gun is a π/2-mode standing wave structure, which consists of two S-band accelerating cells and a side-coupling cavity. The 2856 MHz RF wave is supplied from an S-band klystron to the gun through the waveguide input-port at the cylindrical wall of the second cell. A fraction of the RF power is coupled from the second cell to the first one via a side-coupling cavity. Both the waveguide input-port and the side-coupling cavity lead to an asymmetric geometry of the gun. RF properties and electromagnetic field distributions inside the RF-gun were studied and numerically simulated by using computer codes SUPERFISH 7.19 and CST Microwave Studio 2012©. RF characterizations and tunings of the RF-gun were performed to ensure the reliability of the gun operation. The results from 3D simulations and measurements are compared and discussed in this paper. The influence of asymmetric field distributions inside the RF-gun on the electron beam properties was investigated via 3D beam dynamics simulations. A change in the coupling-plane of the side-coupling cavity is suggested to improve the gun performance.
RF study and 3-D simulations of a side-coupling thermionic RF-gun
Energy Technology Data Exchange (ETDEWEB)
Rimjaem, S., E-mail: sakhorn.rimjaem@cmu.ac.th [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Thailand Center of Excellence in Physics (ThEP), Commission on Higher Education, Bangkok 10400 (Thailand); Kusoljariyakul, K.; Thongbai, C. [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Thailand Center of Excellence in Physics (ThEP), Commission on Higher Education, Bangkok 10400 (Thailand)
2014-02-01
A thermionic RF-gun for generating ultra-short electron bunches was optimized, developed and used as a source at a linac-based THz radiation research laboratory of the Plasma and Beam Physics Research Facility, Chiang Mai University, Thailand. The RF-gun is a π/2-mode standing wave structure, which consists of two S-band accelerating cells and a side-coupling cavity. The 2856 MHz RF wave is supplied from an S-band klystron to the gun through the waveguide input-port at the cylindrical wall of the second cell. A fraction of the RF power is coupled from the second cell to the first one via a side-coupling cavity. Both the waveguide input-port and the side-coupling cavity lead to an asymmetric geometry of the gun. RF properties and electromagnetic field distributions inside the RF-gun were studied and numerically simulated by using computer codes SUPERFISH 7.19 and CST Microwave Studio 2012{sup ©}. RF characterizations and tunings of the RF-gun were performed to ensure the reliability of the gun operation. The results from 3D simulations and measurements are compared and discussed in this paper. The influence of asymmetric field distributions inside the RF-gun on the electron beam properties was investigated via 3D beam dynamics simulations. A change in the coupling-plane of the side-coupling cavity is suggested to improve the gun performance.
3D numerical simulation of the evolutionary process of aeolian downsized crescent-shaped dunes
Zhou, Xiaosi; Zhang, Yang; Wang, Yuan; Li, Min
2016-06-01
A dune constitutive model was coupled with a large eddy simulation (LES) with the Smagorinsky subgrid-scale (SGS) model to accurately describe the evolutionary process of dunes from the macroscopic perspective of morphological dynamics. A 3D numerical simulation of the evolution of aeolian downsized crescent-shaped dunes was then performed. The evolution of the 3D structure of Gaussian-shaped dunes was simulated under the influence of gravity modulation, which was the same with the vertical oscillation of the sand bed to adjust the threshold of sand grain liftoff in wind tunnel experiments under the same wind speed. The influence of gravity modulation intensity on the characteristic scale parameter of the dune was discussed. Results indicated that the crescent shape of the dune was reproduced with the action of gravity during regulation of the saturation of wind-sand flow at specific times. The crescent shape was not dynamically maintained as time passed, and the dunes dwindled until they reached final decomposition because of wind erosion. The height of the dunes decreased over time, and the height-time curve converged as the intensity of modulation increased linearly. The results qualitatively agreed with those obtained from wind tunnel experiments.
3-D-numerical approach to simulate an avalanche impact into a reservoir
Directory of Open Access Journals (Sweden)
R. Gabl
2015-06-01
Full Text Available The impact of an avalanche into a reservoir induces an impulse wave, which poses a threat to population and infrastructure. For a good approximation of the generated wave height and length as well as the resulting outflow volume over structures and dams, formulas, which base on different simplifying assumptions, can be used. Further project-specific investigations by means of a scale model test or numerical simulations are advisable for complex reservoirs as well as the inclusion of hydraulic structures such as spillways. The paper presents a new approach for a 3-D-numerical simulation of an avalanche impact into a reservoir. In this model concept the energy and mass of the avalanche are represented by accelerated water on the real hill slope. Instead of snow, only water and air are used to simulate the moving avalanche with the software FLOW-3D. A significant advantage of this assumption is the self-adaptation of the model avalanche onto the terrain. In order to reach good comparability of the results with existing research at the ETH Zürich, a simplified reservoir geometry is investigated. Thus, a reference case has been analysed including a variation of three geometry parameters (still water depth in the reservoir, freeboard of the dam and reservoir width.
Integrated ray tracing simulation of spectral bio-signatures from full 3D earth model
Ryu, Dongok; Seong, Sehyun; Lee, Jae-Min; Hong, Jinsuk; Jeong, Soomin; Jeong, Yukyeong; Kim, Sug-Whan
2009-08-01
Accurate identification and understanding of spectral bio-signatures from possible extra terrestrial planets have received an ever increasing attention from both astronomy and space science communities in recent years. In pursuance of this subject, one of the most important scientific breakthroughs would be to obtain the detailed understanding on spectral biosignatures of the Earth, as it serves as a reference datum for accurate interpretation of collapsed (in temporal and spatial domains) information from the spectral measurement using TPF instruments. We report a new Integrated Ray Tracing (IRT) model capable of computing various spectral bio-signatures as they are observed from the Earth surface. The model includes the Sun, the full 3-D Earth, and an optical instrument, all combined into single ray tracing environment in real scale. In particular, the full 3-D Earth surface is constructed from high resolution coastal line data and defined with realistic reflectance and BSDF characteristics depending on wavelength, vegetation types and their distributions. We first examined the model validity by confirming the imaging and radiometric performance of the AmonRa visible channel camera, simulating the Earth observation from the L1 halo orbit. We then computed disk averaged spectra, light curves and NDVI indexes, leading to the construction of the observed disk averaged spectra at the AmonRa instrument detector plane. The model, computational procedure and the simulation results are presented. The future plan for the detailed spectral signature simulation runs for various input conditions including seasonal vegetation changes and variable cloud covers is discussed.
3D Simulation of Storm Surge Disaster Based on Scenario Analysis
Institute of Scientific and Technical Information of China (English)
王晓玲; 孙小沛; 张胜利; 孙蕊蕊; 李瑞金; 朱泽彪
2016-01-01
The occurrence of storm surge disaster is often accompanied with floodplain, overflow, dike breach and other complex phenomena, while current studies on storm surge flooding are more concentrated on the 1D/2D numerical simulation of single disaster scenario (floodplain, overflow or dike breach), ignoring the composite ef-fects of various phenomena. Therefore, considering the uncertainty in the disaster process of storm surge, scenario analysis was firstly proposed to identify the composite disaster scenario including multiple phenomena by analyzing key driving forces, building scenario matrix and deducing situation logic. Secondly, by combining the advantages of k-ωand k-εmodels in the wall treatment, a shear stress transmission k-ωmodel coupled with VOF was proposed to simulate the 3D flood routing for storm surge disaster. Thirdly, risk degree was introduced to make the risk analysis of storm surge disaster. Finally, based on the scenario analysis, four scenarios with different storm surge intensity (100-year and 200-year frequency) were identified in Tianjin Binhai New Area. Then, 3D numerical simulation and risk map were made for the case.
3D simulations of globules and pillars formation around HII regions: turbulence and shock curvature
Tremblin, P; Minier, V; Schmidt, W; Schneider, N
2012-01-01
We investigate the interplay between the ionization radiation from massive stars and the turbulence inside the surrounding molecular gas thanks to 3D numerical simulations. We used the 3D hydrodynamical code HERACLES to model an initial turbulent medium that is ionized and heated by an ionizing source. Three different simulations are performed with different mean Mach numbers (1, 2 and 4). A non-equilibrium model for the ionization and the associated thermal processes was used. This revealed to be crucial when turbulent ram pressure is of the same order as the ionized-gas pressure. The density structures initiated by the turbulence cause local curvatures of the dense shell formed by the ionization compression. When the curvature of the shell is sufficient, the shell collapse on itself to form a pillar while a smaller curvature leads to the formation of dense clumps that are accelerated with the shell and therefore remain in the shell during the simulation. When the turbulent ram pressure of the cold gas is su...
High-resolution 3D simulations of NIF ignition targets performed on Sequoia with HYDRA
Marinak, M. M.; Clark, D. S.; Jones, O. S.; Kerbel, G. D.; Sepke, S.; Patel, M. V.; Koning, J. M.; Schroeder, C. R.
2015-11-01
Developments in the multiphysics ICF code HYDRA enable it to perform large-scale simulations on the Sequoia machine at LLNL. With an aggregate computing power of 20 Petaflops, Sequoia offers an unprecedented capability to resolve the physical processes in NIF ignition targets for a more complete, consistent treatment of the sources of asymmetry. We describe modifications to HYDRA that enable it to scale to over one million processes on Sequoia. These include new options for replicating parts of the mesh over a subset of the processes, to avoid strong scaling limits. We consider results from a 3D full ignition capsule-only simulation performed using over one billion zones run on 262,000 processors which resolves surface perturbations through modes l = 200. We also report progress towards a high-resolution 3D integrated hohlraum simulation performed using 262,000 processors which resolves surface perturbations on the ignition capsule through modes l = 70. These aim for the most complete calculations yet of the interactions and overall impact of the various sources of asymmetry for NIF ignition targets. This work was performed under the auspices of the Lawrence Livermore National Security, LLC, (LLNS) under Contract No. DE-AC52-07NA27344.
3D printing of tissue-simulating phantoms for calibration of biomedical optical devices
Zhao, Zuhua; Zhou, Ximing; Shen, Shuwei; Liu, Guangli; Yuan, Li; Meng, Yuquan; Lv, Xiang; Shao, Pengfei; Dong, Erbao; Xu, Ronald X.
2016-10-01
Clinical utility of many biomedical optical devices is limited by the lack of effective and traceable calibration methods. Optical phantoms that simulate biological tissues used for optical device calibration have been explored. However, these phantoms can hardly simulate both structural and optical properties of multi-layered biological tissue. To address this limitation, we develop a 3D printing production line that integrates spin coating, light-cured 3D printing and Fused Deposition Modeling (FDM) for freeform fabrication of optical phantoms with mechanical and optical heterogeneities. With the gel wax Polydimethylsiloxane (PDMS), and colorless light-curable ink as matrix materials, titanium dioxide (TiO2) powder as the scattering ingredient, graphite powder and black carbon as the absorption ingredient, a multilayer phantom with high-precision is fabricated. The absorption and scattering coefficients of each layer are measured by a double integrating sphere system. The results demonstrate that the system has the potential to fabricate reliable tissue-simulating phantoms to calibrate optical imaging devices.
NUMERICAL SIMULATION OF 3-D FLOW FIELD IN ARCIFORM PLUNGE POOL
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
The 3-D complex turbulent flow fields in aplunge pool with arciform bottom are simulated by using thek-ε model in body-fitted coordinates. The calculated results re-veal the flow characteristics in the arciform plunge pool underthe different flood discharge conditions, which can not be easi-ly obtained in the physical model test because the measure-ment of the complex velocity is very difficult. The calculatedflow fields are helpful to understand in depth the hydrauliccharacteristics of plunge pool. The calculated and the meas-ured pressure distributions on the pool bottom are comparedand in good agreement.
Numerical simulation of a combined oxidation ditch flow using 3D k-εturbulence model
Institute of Scientific and Technical Information of China (English)
LUO Lin; LI Wei-min; DENG Yong-sen; WANG Tao
2005-01-01
The standard three dimensional(3D) k-ε turbulence model was applied to simulate the flow field of a small scale combined oxidation ditch. The moving mesh approach was used to model the rotor of the ditch. Comparison of the computed and the measured data is acceptable. A vertical reverse flow zone in the ditch was found, and it played a very important role in the ditch flow behavior. The flow pattern in the ditch is discussed in detail, and approaches are suggested to improve the hydrodynamic performance in the ditch.
Coupling Magnetic Fields and ALE Hydrodynamics for 3D Simulations of MFCG's
Energy Technology Data Exchange (ETDEWEB)
White, D; Rieben, R; Wallin, B
2006-09-20
We review the development of a full 3D multiphysics code for the simulation of explosively driven Magnetic Flux Compression Generators (MFCG) and related pulse power devices. In a typical MFCG the device is seeded with an initial electric current and the device is then detonated. The detonation compresses the magnetic field and amplifies the current. This is a multiphysics problem in that detonation kinetics, electromagnetic diffusion and induction, material deformation, and thermal effects are all important. This is a tightly coupled problem in that the different physical quantities have comparable spatial and temporal variation, and hence should be solved simultaneously on the same computational mesh.
Comparison of empirical magnetic field models and global MHD simulations: The near-tail currents
Pulkkinen, T. I.; Baker, D. N.; Walker, R. J.; Raeder, J.; Ashour-Abdalla, M.
1995-01-01
The tail currents predicted by empirical magnetic field models and global MHD simulations are compared. It is shown that the near-Earth currents obtained from the MHD simulations are much weaker than the currents predicted by the Tsyganenko models, primarily because the ring current is not properly represented in the simulations. On the other hand, in the mid-tail and distant tail the lobe field strength predicted by the simulations is comparable to what is observed at about 50 R(sub E) distance, significantly larger than the very low lobe field values predicted by the Tsyganenko models at that distance. Ways to improve these complementary approaches to model the actual magnetospheric configuration are discussed.
MHD simulations of radiative jets from young stellar objects: Halpha emission
De Colle, F; Colle, Fabio De; Raga, Alejandro
2005-01-01
We study the H$\\alpha$ emission from jets using two-dimensional axisymmetrical simulations. We compare the emission obtained from hydrodynamic (HD) simulations with that obtained from magnetohydrodynamics (MHD) simulations. The magnetic field is supposed to be present in the jet only, and with a toroidal configuration. The simulations have time-dependent ejection velocities and different intensities for the initial magnetic field. The results show an increase in the H$\\alpha$ emission along the jet for the magnetized cases with respect to the HD case. The increase in the emission is due to a better collimation of the jet in the MHD case, and to a small increase in the shock velocity. These results could have important implications for the interpretation of the observations of jets from young stellar objects.
Terascale direct numerical simulations of turbulent combustion using S3D.
Energy Technology Data Exchange (ETDEWEB)
Sankaran, Ramanan; Mellor-Crummy, J.; DeVries, M.; Yoo, Chun Sang; Ma, K. L.; Podhorski, N.; Liao, W. K.; Klasky, S.; de Supinski, B.; Choudhary, A.; Hawkes, Evatt R.; Chen, Jacqueline H.; Shende, Sameer
2008-08-01
Computational science is paramount to the understanding of underlying processes in internal combustion engines of the future that will utilize non-petroleum-based alternative fuels, including carbon-neutral biofuels, and burn in new combustion regimes that will attain high efficiency while minimizing emissions of particulates and nitrogen oxides. Next-generation engines will likely operate at higher pressures, with greater amounts of dilution and utilize alternative fuels that exhibit a wide range of chemical and physical properties. Therefore, there is a significant role for high-fidelity simulations, direct numerical simulations (DNS), specifically designed to capture key turbulence-chemistry interactions in these relatively uncharted combustion regimes, and in particular, that can discriminate the effects of differences in fuel properties. In DNS, all of the relevant turbulence and flame scales are resolved numerically using high-order accurate numerical algorithms. As a consequence terascale DNS are computationally intensive, require massive amounts of computing power and generate tens of terabytes of data. Recent results from terascale DNS of turbulent flames are presented here, illustrating its role in elucidating flame stabilization mechanisms in a lifted turbulent hydrogen/air jet flame in a hot air co-flow, and the flame structure of a fuel-lean turbulent premixed jet flame. Computing at this scale requires close collaborations between computer and combustion scientists to provide optimized scaleable algorithms and software for terascale simulations, efficient collective parallel I/O, tools for volume visualization of multiscale, multivariate data and automating the combustion workflow. The enabling computer science, applied to combustion science, is also required in many other terascale physics and engineering simulations. In particular, performance monitoring is used to identify the performance of key kernels in the DNS code, S3D and especially memory
Terascale direct numerical simulations of turbulent combustion using S3D
Chen, J. H.; Choudhary, A.; de Supinski, B.; DeVries, M.; Hawkes, E. R.; Klasky, S.; Liao, W. K.; Ma, K. L.; Mellor-Crummey, J.; Podhorszki, N.; Sankaran, R.; Shende, S.; Yoo, C. S.
2009-01-01
Computational science is paramount to the understanding of underlying processes in internal combustion engines of the future that will utilize non-petroleum-based alternative fuels, including carbon-neutral biofuels, and burn in new combustion regimes that will attain high efficiency while minimizing emissions of particulates and nitrogen oxides. Next-generation engines will likely operate at higher pressures, with greater amounts of dilution and utilize alternative fuels that exhibit a wide range of chemical and physical properties. Therefore, there is a significant role for high-fidelity simulations, direct numerical simulations (DNS), specifically designed to capture key turbulence-chemistry interactions in these relatively uncharted combustion regimes, and in particular, that can discriminate the effects of differences in fuel properties. In DNS, all of the relevant turbulence and flame scales are resolved numerically using high-order accurate numerical algorithms. As a consequence terascale DNS are computationally intensive, require massive amounts of computing power and generate tens of terabytes of data. Recent results from terascale DNS of turbulent flames are presented here, illustrating its role in elucidating flame stabilization mechanisms in a lifted turbulent hydrogen/air jet flame in a hot air coflow, and the flame structure of a fuel-lean turbulent premixed jet flame. Computing at this scale requires close collaborations between computer and combustion scientists to provide optimized scaleable algorithms and software for terascale simulations, efficient collective parallel I/O, tools for volume visualization of multiscale, multivariate data and automating the combustion workflow. The enabling computer science, applied to combustion science, is also required in many other terascale physics and engineering simulations. In particular, performance monitoring is used to identify the performance of key kernels in the DNS code, S3D and especially memory
Large-scale 3D simulations of ICF and HEDP targets
Marinak, Michael M.
2000-10-01
The radiation hydrodynamics code HYDRA continues to be developed and applied to 3D simulations of a variety of targets for both inertial confinement fusion (ICF) and high energy density physics. Several packages have been added enabling this code to perform ICF target simulations with similar accuracy as two-dimensional codes of long-time historical use. These include a laser ray trace and deposition package, a heavy ion deposition package, implicit Monte Carlo photonics, and non-LTE opacities, derived from XSN or the linearized response matrix approach.(R. More, T. Kato, Phys. Rev. Lett. 81, 814 (1998), S. Libby, F. Graziani, R. More, T. Kato, Proceedings of the 13th International Conference on Laser Interactions and Related Plasma Phenomena, (AIP, New York, 1997).) LTE opacities can also be calculated for arbitrary mixtures online by combining tabular values generated by different opacity codes. Thermonuclear burn, charged particle transport, neutron energy deposition, electron-ion coupling and conduction, and multigroup radiation diffusion packages are also installed. HYDRA can employ ALE hydrodynamics; a number of grid motion algorithms are available. Multi-material flows are resolved using material interface reconstruction. Results from large-scale simulations run on up to 1680 processors, using a combination of massively parallel processing and symmetric multiprocessing, will be described. A large solid angle simulation of Rayleigh-Taylor instability growth in a NIF ignition capsule has resolved simultaneously the full spectrum of the most dangerous modes that grow from surface roughness. Simulations of a NIF hohlraum illuminated with the initial 96 beam configuration have also been performed. The effect of the hohlraum’s 3D intrinsic drive asymmetry on the capsule implosion will be considered. We will also discuss results from a Nova experiment in which a copper sphere is crushed by a planar shock. Several interacting hydrodynamic instabilities, including
Insights from 3D numerical simulations on the dynamics of the India-Asia collision zone
Pusok, A. E.; Kaus, B.; Popov, A.
2013-12-01
The dynamics of the India-Asia collision zone remains one of the most remarkable topics of the current research interest: the transition from subduction to collision and uplift, followed by the rise of the abnormally thick Tibetan plateau, and the deformation at its Eastern and Western syntaxes, are processes still not fully understood. Models that have addressed this topic include wholescale underthrusting of Indian lithospheric mantle under Tibet, distributed homogeneous shortening or the thin-sheet model, slip-line field model for lateral extrusion or lower crustal flow models for the exhumation of the Himalayan units and lateral spreading of the Tibetan plateau. Of these, the thin-sheet model has successfully illustrated some of the basic physics of continental collision and has the advantage of a 3D model being reduced to 2D, but one of its major shortcomings is that it cannot simultaneously represent channel flow and gravitational collapse of the mantle lithosphere, since these mechanisms require the lithosphere to interact with the underlying mantle, or to have a vertically non-homogeneous rheology. As a consequence, 3D models are emerging as powerful tools to understand the dynamics of coupled systems. However, because of yet recent developments and various complexities, the current 3D models simulating the dynamics of continent collision zones have relied on certain explicit assumptions, such as replacing part of the asthenosphere with various types of boundary conditions that mimic the effect of mantle flow, in order to focus on the lithospheric/crustal deformation. Here, we employ the parallel 3D code LaMEM (Lithosphere and Mantle Evolution Model), with a finite difference staggered grid solver, which is capable of simulating lithospheric deformation while simultaneously taking mantle flow and a free surface into account. We present qualitative results on lithospheric and upper-mantle scale simulations in which the Indian lithosphere is subducted and
A 3-D nonisothermal flow simulation and pulling force model for injection pultrusion processes
Mustafa, Ibrahim
1998-12-01
Injected Pultrusion (IP) is an efficient way of producing high quality, low cost, high volume and constant cross-section polymeric composites. This process has been developed recently, and the efforts to optimize it are still underway. This work is related to the development of a 3-D non-isothermal flow model for the IP processes. The governing equations for transport of mass, momentum and, energy are formulated by using a local volume averaging approach, and the Finite Element/Control Volume method is used to solve the system of equations numerically. The chemical species balance equation is solved in the Lagrangian frame of reference whereas the energy equation is solved using Galerkin, SU (Streamline Upwind), and SUPG (Streamline Upwind Petrov Galerkin) approaches. By varying degrees of freedom and the flow rates of the resin, it is shown that at high Peclet numbers the SUPG formulation performs better than the SU and the Galerkin methods in all cases. The 3-D model predictions for degree of cure and temperature are compared with a one dimensional analytical solution and the results are found satisfactory. Moreover, by varying the Brinkman Number, it is shown that the effect of viscous dissipation is insignificant. The 3-D flow simulations have been carried out for both thin and thick parts and the results are compared with the 2-D model. It is shown that for thick parts 2-D simulations render erroneous results. The effect of changing permeability on the flow fronts is also addressed. The effect of increasing taper angle on the model prediction is also investigated. A parametric study is conducted to isolate optimum conditions for both isothermal and non-isothermal cases using a straight rectangular die and a die with a tapered inlet. Finally, a simple pulling force model is developed and the pulling force required to pull the carbon-epoxy fiber resin system is estimated for dies of varying tapered inlet.
3-D GRMHD Simulations of Disk-Jet Coupling and Emission
Nishikawa, K I; Fuerst, S; Wu, K; Hardee, P; Richardson, G; Koide, S; Shibata, K; Kudoh, T; Fishman, G J
2005-01-01
We have performed a fully three-dimensional general relativistic magnetohydrodynamic (GRMHD) simulation of jet formation from a thin accretion disk around a Schwarzschild black hole with a free-falling corona. The initial simulation results show that a bipolar jet (velocity nearly 0.3c) is created as shown by previous two-dimensional axisymmetric simulations with mirror symmetry at the equator. The 3-D simulation ran over one hundred light-crossing time units which is considerably longer than the previous simulations. We show that the jet is initially formed as predicted due in part to magnetic pressure from the twisting the initially uniform magnetic field and from gas pressure associated with shock formation in the region around r = 3r_S. At later times, the accretion disk becomes thick and the jet fades resulting in a wind that is ejected from the surface of the thickened (torus-like) disk. It should be noted that no streaming matter from a donor is included at the outer boundary in the simulation (an isol...
3D simulations on output power fluctuation in a short bunch rf-linac FEL
Sentoku, Y.; Furukawa, H.; Mima, K.; Taguchi, T.; Kuruma, S.; Yasuda, H.; Yamanaka, C.; Nakai, S.
1995-04-01
A space-time dependent 3D simulation code has been developed in order to analyze the RF-linac FEL oscillator dynamics. Our simulation code employed both the transverse mode spectral method and the longitudinal finite difference method. The electron beam is modeled by a group of super particles which have a density profile in the time domain. In this model the electron beam is able to determine the energy spread and the finite emittance. This simulation code enables us to describe the transverse mode competition and the slippage effects in the resonator cavity. In this paper, a high power infrared FEL with a short bunch electron beam is investigated. The output power fluctuation with cavity desynchronism is simulated with this code. Especially, we investigated the effects of the transverse mode competition, energy spread, and the finite emittance of the electron beam on the output fluctuation. Using FELIX parameters, the FEL oscillator is simulated for 300 passes. The output power oscillates periodically in the case of single transverse mode and not in the case of multi-transverse modes. In a warm beam with multi-transverse modes, the emission is higher than that with a single mode, and the optical pulse shape is almost the after 100 passes. Furthermore, the phase space motion of the laser field is periodic and stable. As a result of the simulation, we recommend that high power infrared FEL operation should include multi-transverse modes in order to get higher emission and a more stable optical pulse.
Quasi 3D refined simulation of flow and pollutant transport in a meandering River Reach
Directory of Open Access Journals (Sweden)
Li-ren Yu
2013-03-01
Full Text Available This paper reports a quasi 3D numerical simulation in a meandering river reach of the Yellow River, aiming to develop a tool for modeling turbulent flows and pollutant transport in complex natural waters. The recently built depth-averaged two-equation turbulence model, together with and models, were used to close non-simplified quasi 3D hydrodynamic fundamental governing equations. The discretized equations were solved by advanced multi-grid iterative method under non-orthogonal body-fitted coarse and fine two-levels’ grids with collocated variable arrangement. Except for steady flow and transport computation, the processes of contaminant inpouring and plume development, caused by the side-discharge from a tribytary, also have been investigated numerically. The used three closure approaches are suitable for modeling strong mixing turbulence. The established model with higher order of magnitude of transported variable provides a possibility to elevate the computational precision. Based on the developed mathematical model, a CFD (Computational Fluid Dynamics software, namely Q3drm1.0, was developed. This numerical tool focuses on the refined simulations of the steady and unsteady problems of flow and temperature/contaminant transports in complicated computational domains with the strong ability to deal with different discharge situations: side-discharge, point-source discharge/point-sink, and area-source discharge from the slope along bank. In this article, the study of side-discharge is presented only.
Casting directly from a computer model by using advanced simulation software FLOW-3D Cast ®
Directory of Open Access Journals (Sweden)
M. Sirviö
2009-01-01
Full Text Available ConiferRob - A patternless casting technique, originally conceived at VTT Technical Research Centre of Finland and furtherdeveloped at its spin-off company, Simtech Systems, offers up to 40% savings in product development costs, and up to two months shorterdevelopment times compared to conventional techniques. Savings of this order can be very valuable on today's highly competitivemarkets. Casting simulation is commonly used for designing of casting systems. However, most of the software are today old fashioned and predicting just shrinkage porosity. Flow Science, VTT and Simtech have developed new software called FLOW-3D Cast ® , whichcan simulate surface defects, air entrainment, filters, core gas problems and even a cavitation.
A NUMERICAL SIMULATION OF 3-D INNER FLOW IN UP-STREAM PUMPING MECHANICAL SEAL
Institute of Scientific and Technical Information of China (English)
ZHANG Jin-feng; YUAN Shou-qi; FU Yong-hong; FANG Yu-jian
2006-01-01
Numerical simulation of 3-D inner flow between Up-stream Pumping Mechanical Face Seals (UPMFS) faces was initially done by CFD software, which made the flow visualization come true.Simulation results directly discover the action of hydrodynamic lubrication, and by comparison with that of Conventional Mechanic Face Seals (CMFS), the advantage over bigger bearing capability, less friction and much less leakage are explained clearly.Otherwise there are also some different ideas and results from precedent analysis and computational research results: dynamic and static pressure profiles can be obtained respectively instead of the analytic total pressure distribution only, pressure distribution is nonlinear, while always be solved as linear, lower pressure is observed at the area of inner diameter caused by the grooves, but its possible cavitations effects to the performance of UPMFS still need further study.
3-D transient numerical simulation on the process of laser cladding by powder feeding
Institute of Scientific and Technical Information of China (English)
Yanlu Huang; Gongying Liang; Junyi Su
2004-01-01
A 3-D transient mathematical model for laser cladding by powder feeding was developed to examine the macroscopic heat and momentum transport during the process, based on which a novel method for determining the configuration and thickness of cladding layer was presented. By using Lambert-Beer theorem and Mie′s theory, the interaction between powder stream and laser beam was treated to evoke their subtle effects on heat transfer and fluid flow in laser molten pool. The numerical study was performed in a co-ordinate system moving with the laser at a constant scanning speed. A fixed grid enthalpy-porosity approach was used,which predicted the evolutionary development of the laser molten pool. The commercial software PHOENICS, to which several modules were appended, was used to accomplish the simulation. The results obtained by the simulation were coincident with those measured in experiment basically.
[A rapid prototype fabrication method of dental splint based on 3D simulation and technology].
Lin, Yanping; Chen, Xiaojun; Zhang, Shilei; Wang, Chengtao
2006-04-01
The conventional design and fabrication of the dental splint (in orthognathic surgery) is based on the preoperative planning and model surgery so this process is of low precision and efficiency. In order to solve the problems and be up to the trend of computer-assisted surgery, we have developed a novel method to design and fabricate the dental splint--computer-generated dental splint, which is based on three-dimensional model simulation and rapid prototype technology. After the surgical planning and simulation of 3D model, we can modify the model to be superior in chewing action (functional) and overall facial appearance (aesthetic). Then, through the Boolean operation of the dental splint blank and the maxillofacial bone model the model of dental splint is formed. At last, the dental splint model is fabricated through rapid prototype machine and applied in clinic. The result indicates that, with the use of this method, the surgical precision and efficiency are improved.
3D Simulation of the Gas Dynamics in the Central Parsec of the Galaxy
Coker, R F
1998-01-01
It is thought that many characteristics of the gaseous features within the central parsec of our Galaxy, are associated with the accretion of ambient plasma by a central concentration of mass. Using a 3D hydrodynamical code, we have been simulating this process in order to realistically model the gaseous flows in the center of our Galaxy. In the most recent simulation, we have taken into account the multi-point-like distribution of stellar wind sources, as well as the magnetic heating and radiative cooling of these stellar winds. As expected, we find that the structure of the flow is significantly different from that due to a uniform medium. We also investigate the possibility that Sgr A* is due to a distributed mass concentration instead of the canonical point mass of a black hole. We discuss the physical state of the accreting gas and how our results suggest that Sgr A* is unlikely to be associated with a ``dark cluster''.
A simulation technique for 3D MR-guided acoustic radiation force imaging
Energy Technology Data Exchange (ETDEWEB)
Payne, Allison, E-mail: apayne@ucair.med.utah.edu [Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah 84112 (United States); Bever, Josh de [Department of Computer Science, University of Utah, Salt Lake City, Utah 84112 (United States); Farrer, Alexis [Department of Bioengineering, University of Utah, Salt Lake City, Utah 84112 (United States); Coats, Brittany [Department of Mechanical Engineering, University of Utah, Salt Lake City, Utah 84112 (United States); Parker, Dennis L. [Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah 84108 (United States); Christensen, Douglas A. [Department of Bioengineering, University of Utah, Salt Lake City, Utah 84112 and Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, Utah 84112 (United States)
2015-02-15
Purpose: In magnetic resonance-guided focused ultrasound (MRgFUS) therapies, the in situ characterization of the focal spot location and quality is critical. MR acoustic radiation force imaging (MR-ARFI) is a technique that measures the tissue displacement caused by the radiation force exerted by the ultrasound beam. This work presents a new technique to model the displacements caused by the radiation force of an ultrasound beam in a homogeneous tissue model. Methods: When a steady-state point-source force acts internally in an infinite homogeneous medium, the displacement of the material in all directions is given by the Somigliana elastostatic tensor. The radiation force field, which is caused by absorption and reflection of the incident ultrasound intensity pattern, will be spatially distributed, and the tensor formulation takes the form of a convolution of a 3D Green’s function with the force field. The dynamic accumulation of MR phase during the ultrasound pulse can be theoretically accounted for through a time-of-arrival weighting of the Green’s function. This theoretical model was evaluated experimentally in gelatin phantoms of varied stiffness (125-, 175-, and 250-bloom). The acoustic and mechanical properties of the phantoms used as parameters of the model were measured using independent techniques. Displacements at focal depths of 30- and 45-mm in the phantoms were measured by a 3D spin echo MR-ARFI segmented-EPI sequence. Results: The simulated displacements agreed with the MR-ARFI measured displacements for all bloom values and focal depths with a normalized RMS difference of 0.055 (range 0.028–0.12). The displacement magnitude decreased and the displacement pattern broadened with increased bloom value for both focal depths, as predicted by the theory. Conclusions: A new technique that models the displacements caused by the radiation force of an ultrasound beam in a homogeneous tissue model theory has been rigorously validated through comparison
Parallel computing simulation of electrical excitation and conduction in the 3D human heart.
Di Yu; Dongping Du; Hui Yang; Yicheng Tu
2014-01-01
A correctly beating heart is important to ensure adequate circulation of blood throughout the body. Normal heart rhythm is produced by the orchestrated conduction of electrical signals throughout the heart. Cardiac electrical activity is the resulted function of a series of complex biochemical-mechanical reactions, which involves transportation and bio-distribution of ionic flows through a variety of biological ion channels. Cardiac arrhythmias are caused by the direct alteration of ion channel activity that results in changes in the AP waveform. In this work, we developed a whole-heart simulation model with the use of massive parallel computing with GPGPU and OpenGL. The simulation algorithm was implemented under several different versions for the purpose of comparisons, including one conventional CPU version and two GPU versions based on Nvidia CUDA platform. OpenGL was utilized for the visualization / interaction platform because it is open source, light weight and universally supported by various operating systems. The experimental results show that the GPU-based simulation outperforms the conventional CPU-based approach and significantly improves the speed of simulation. By adopting modern computer architecture, this present investigation enables real-time simulation and visualization of electrical excitation and conduction in the large and complicated 3D geometry of a real-world human heart.
3D Multistage Simulation of Each Component of the GE90 Turbofan Engine
Turner, Mark; Topp, Dave; Veres, Joe
1999-01-01
A 3D multistage simulation of each component of the GE90 Turbofan engine has been made. This includes 49 blade rows. A coupled simulation of all blade rows will be made very soon. The simulation is running using two levels of parallelism. The first level is on a blade row basis with information shared using files. The second level is using a grid domain decomposition with information shared using MPI. Timings will be shown for running on the SP2, an SGI Origin and a distributed system of HP workstations. On the HP workstations, the CHIMP version of MPI is used, with queuing supplied by LSF (Load Sharing Facility). A script-based control system is used to ensure reliability. An MPEG movie illustrating the flow simulation of the engine has been created using PV3, a parallel visualization library created by Bob Haimes of MIT. PVM is used to create a virtual machine from 10 HP workstations and display on an SGI workstation. A representative component simulation will be compared to rig data to demonstrate its usefulness in turbomachinery design and analysis.
Esposti Ongaro, T.; Neri, A.; Menconi, G.; de'Michieli Vitturi, M.; Marianelli, P.; Cavazzoni, C.; Erbacci, G.; Baxter, P. J.
2008-12-01
Numerical simulations of column collapse and pyroclastic density current (PDC) scenarios at Vesuvius were carried out using a transient 3D flow model based on multiphase transport laws. The model describes the dynamics of the collapse as well as the effects of the 3D topography of the volcano on PDC propagation. Source conditions refer to a medium-scale sub-Plinian event and consider a pressure-balanced jet. Simulation results provide new insights into the complex dynamics of these phenomena. In particular: 1) column collapse can be characterized by different regimes, from incipient collapse to partial or nearly total collapse, thus confirming the possibility of a transitional field of behaviour of the column characterized by the contemporaneous and/or intermittent occurrence of ash fallout and PDCs; 2) the collapse regime can be characterized by its fraction of eruptive mass reaching the ground and generating PDCs; 3) within the range of the investigated source conditions, the propagation and hazard potential of PDCs appear to be directly correlated with the flow-rate of the mass collapsing to the ground, rather than to the collapse height of the column (this finding is in contrast with predictions based on the energy-line concept, which simply correlates the PDC runout and kinetic energy with the collapse height of the column); 4) first-order values of hazard variables associated with PDCs (i.e., dynamic pressure, temperature, airborne ash concentration) can be derived from simulation results, thereby providing initial estimates for the quantification of damage scenarios; 5) for scenarios assuming a location of the central vent coinciding with that of the present Gran Cono, Mount Somma significantly influences the propagation of PDCs, largely reducing their propagation in the northern sector, and diverting mass toward the west and southeast, accentuating runouts and hazard variables for these sectors; 6) the 2D modelling approximation can force an artificial
Augmented reality intravenous injection simulator based 3D medical imaging for veterinary medicine.
Lee, S; Lee, J; Lee, A; Park, N; Lee, S; Song, S; Seo, A; Lee, H; Kim, J-I; Eom, K
2013-05-01
Augmented reality (AR) is a technology which enables users to see the real world, with virtual objects superimposed upon or composited with it. AR simulators have been developed and used in human medicine, but not in veterinary medicine. The aim of this study was to develop an AR intravenous (IV) injection simulator to train veterinary and pre-veterinary students to perform canine venipuncture. Computed tomographic (CT) images of a beagle dog were scanned using a 64-channel multidetector. The CT images were transformed into volumetric data sets using an image segmentation method and were converted into a stereolithography format for creating 3D models. An AR-based interface was developed for an AR simulator for IV injection. Veterinary and pre-veterinary student volunteers were randomly assigned to an AR-trained group or a control group trained using more traditional methods (n = 20/group; n = 8 pre-veterinary students and n = 12 veterinary students in each group) and their proficiency at IV injection technique in live dogs was assessed after training was completed. Students were also asked to complete a questionnaire which was administered after using the simulator. The group that was trained using an AR simulator were more proficient at IV injection technique using real dogs than the control group (P ≤ 0.01). The students agreed that they learned the IV injection technique through the AR simulator. Although the system used in this study needs to be modified before it can be adopted for veterinary educational use, AR simulation has been shown to be a very effective tool for training medical personnel. Using the technology reported here, veterinary AR simulators could be developed for future use in veterinary education.
The dark side of photovoltaic — 3D simulation of glare assessing risk and discomfort
Energy Technology Data Exchange (ETDEWEB)
Rose, Thomas; Wollert, Alexander
2015-04-15
Photovoltaic (PV) systems form an important force in the implementation of renewable energies, but as we all know, the force has always its dark side. Besides efficiency considerations and discussions about architectures of power distribution networks, the increasing numbers of installations of PV systems for implementing renewable energies have secondary effects. PV systems can generate glare due to optical reflections and hence might be a serious concern. On the one hand, glare could affect safety, e.g. regarding traffic. On the other hand, glare is a constant source of discomfort in vicinities of PV systems. Hence, assessment of glare is decisive for the success of renewable energies near municipalities and traffic zones for the success of solar power. Several courts decided on the change of PV systems and even on their de-installation because of glare effects. Thus, location-based assessments are required to limit potential reflections and to avoid risks for public infrastructure or discomfort of residents. The question arises on how to calculate reflections accurately according to the environment's topography. Our approach is founded in a 3D-based simulation methodology to calculate and visualize reflections based on the geometry of the environment of PV systems. This computational model is implemented by an interactive tool for simulation and visualization. Hence, project planners receive flexible assistance for adjusting the parameters of solar panels amid the planning process and in particular before the installation of a PV system. - Highlights: • Solar panels cause glare that impacts neighborhoods and traffic infrastructures. • Glare might cause disability and discomfort. • 3D environment for the calculation of glare • Interactive tool to simulate and visualize reflections • Impact assessment of solar power plant farms.
Tchekhovskoy, Alexander
2015-01-01
Active galactic nuclei jets are thought to form in the immediate vicinity of the event horizons of supermassive black holes. Therefore, jets could be excellent probes of general relativity. However, in practice, using jets to infer near-black hole physics is not straightforward since the cause of their most basic morphological features is not understood. For instance, there is no agreement on the cause of the well-known Fanaroff-Riley (FR) morphological dichotomy of jets, with FRI jets being shorter and wiggly and FRII jets being longer and more stable. Here, we carry out 3D relativistic magnetohydrodynamic (MHD) simulations of relativistic jets propagating through the ambient medium. Because in flat density cores of galaxies ($n \\propto r^{-\\alpha}$ with $\\alpha < 2$) the mass per unit distance ahead of the jets increases with distance, the jets slow down and collimate into smaller opening angles. This makes the jets more vulnerable to the 3D magnetic kink ("corkscrew") instability, which develops faster ...
Deng, Wei; Li, Hui; Zhang, Bing; Li, Shengtai
2015-06-01
We perform 3D relativistic ideal magnetohydrodynamics (MHD) simulations to study the collisions between high-σ (Poynting-flux-dominated (PFD)) blobs which contain both poloidal and toroidal magnetic field components. This is meant to mimic the interactions inside a highly variable PFD jet. We discover a significant electromagnetic field (EMF) energy dissipation with an Alfvénic rate with the efficiency around 35%. Detailed analyses show that this dissipation is mostly facilitated by the collision-induced magnetic reconnection. Additional resolution and parameter studies show a robust result that the relative EMF energy dissipation efficiency is nearly independent of the numerical resolution or most physical parameters in the relevant parameter range. The reconnection outflows in our simulation can potentially form the multi-orientation relativistic mini jets as needed for several analytical models. We also find a linear relationship between the σ values before and after the major EMF energy dissipation process. Our results give support to the proposed astrophysical models that invoke significant magnetic energy dissipation in PFD jets, such as the internal collision-induced magnetic reconnection and turbulence model for gamma-ray bursts, and reconnection triggered mini jets model for active galactic nuclei. The simulation movies are shown in http://www.physics.unlv.edu/∼deng/simulation1.html.
Photospheric Emission of Collapsar Jet in 3D Relativistic Radiation Hydrodynamical Simulation
Ito, Hirotaka; Nagataki, Shigehiro; Warren, Donald C; Barkov, Maxim V
2015-01-01
We explore the photospheric emission from a relativistic jet breaking out from a massive stellar envelope based on relativistic hydrodynamical simulations and post-process radiation transfer calculations in three dimensions (3D). To investigate the impact of 3D dynamics on the emission, two models of injection conditions are considered for the jet at the center of the progenitor star: one with periodic precession and another without precession. We show that structures developed within the jet due to the interaction with the stellar envelope, as well as due to the precession, have a significant imprint on the resulting emission. Particularly, we find that the signature of precession activity by the central engine is not smeared out and can be directly observed in the light curve as a periodic signal. We also show non-thermal features that can account for observations of gamma-ray bursts are produced in the resulting spectra, even though only thermal photons are injected initially and the effect of non-thermal ...
3D cut-cell modelling for high-resolution atmospheric simulations
Yamazaki, H; Nikiforakis, N
2015-01-01
With the recent, rapid development of computer technology, the resolution of atmospheric numerical models has increased substantially. As a result, steep gradients in mountainous terrain are now being resolved in high-resolution models. This results in large truncation errors in those models using terrain-following coordinates. In this study, a new 3D Cartesian coordinate non-hydrostatic atmospheric model is developed. A cut-cell representation of topography based on finite-volume discretization is combined with a cell-merging approach, in which small cut-cells are merged with neighboring cells either vertically or horizontally. In addition, a block-structured mesh-refinement technique achieves a variable resolution on the model grid with the finest resolution occurring close to the terrain surface. The model successfully reproduces a flow over a 3D bell-shaped hill that shows a good agreement with the flow predicted by the linear theory. The ability of the model to simulate flows over steep terrain is demons...
The Shock Dynamics of Heterogeneous YSO Jets: 3-D Simulations Meet Multi-Epoch Observations
Hansen, E C; Hartigan, P; Lebedev, S V
2016-01-01
High resolution observations of Young Stellar Object (YSO) jets show them to be composed of many small-scale knots or clumps. In this paper we report results of 3-D numerical simulations designed to study how such clumps interact and create morphologies and kinematic patterns seen in emission line observations. Our simulations focus on clump scale dynamics by imposing velocity differences between spherical, over-dense regions which then lead to the formation of bow shocks as faster clumps overtake slower material. We show that much of the spatial structure apparent in emission line images of jets arises from the dynamics and interactions of these bow shocks. Our simulations show a variety of time-dependent features, including bright knots associated with Mach stems where the shocks intersect, a "frothy" emission structure that arises from the presence of the Non-linear Thin Shell Instability (NTSI) along the surfaces of the bow shocks, and the merging and fragmentation of clumps. Our simulations use a new non...
3D design and electric simulation of a silicon drift detector using a spiral biasing adapter
Li, Yu-yun; Xiong, Bo; Li, Zheng
2016-09-01
The detector system of combining a spiral biasing adapter (SBA) with a silicon drift detector (SBA-SDD) is largely different from the traditional silicon drift detector (SDD), including the spiral SDD. It has a spiral biasing adapter of the same design as a traditional spiral SDD and an SDD with concentric rings having the same radius. Compared with the traditional spiral SDD, the SBA-SDD separates the spiral's functions of biasing adapter and the p-n junction definition. In this paper, the SBA-SDD is simulated using a Sentaurus TCAD tool, which is a full 3D device simulation tool. The simulated electric characteristics include electric potential, electric field, electron concentration, and single event effect. Because of the special design of the SBA-SDD, the SBA can generate an optimum drift electric field in the SDD, comparable with the conventional spiral SDD, while the SDD can be designed with concentric rings to reduce surface area. Also the current and heat generated in the SBA are separated from the SDD. To study the single event response, we simulated the induced current caused by incident heavy ions (20 and 50 μm penetration length) with different linear energy transfer (LET). The SBA-SDD can be used just like a conventional SDD, such as X-ray detector for energy spectroscopy and imaging, etc.
3D Simulation of Flow with Free Surface Based on Adaptive Octree Mesh System
Institute of Scientific and Technical Information of China (English)
Li Shaowu; Zhuang Qian; Huang Xiaoyun; Wang Dong
2015-01-01
The technique of adaptive tree mesh is an effective way to reduce computational cost through automatic adjustment of cell size according to necessity. In the present study, the 2D numerical N-S solver based on the adaptive quadtree mesh system was extended to a 3D one, in which a spatially adaptive octree mesh system and multiple parti-cle level set method were adopted for the convenience to deal with the air-water-structure multiple-medium coexisting domain. The stretching process of a dumbbell was simulated and the results indicate that the meshes are well adaptable to the free surface. The collapsing process of water column impinging a circle cylinder was simulated and from the results, it can be seen that the processes of fluid splitting and merging are properly simulated. The interaction of sec-ond-order Stokes waves with a square cylinder was simulated and the obtained drag force is consistent with the result by the Morison’s wave force formula with the coefficient values of the stable drag component and the inertial force component being set as 2.54.
A GIS-Based 3D Simulation for Occupant Evacuation in a Building
Institute of Scientific and Technical Information of China (English)
TANG Fangqin; ZHANG Xin
2008-01-01
The evacuation efficiency of building plans is of obvious importance to the public safety.The cem- plexity of building plans,however,makes it difficult for the efficiency evaluation.This paper presents a com- putational model AutoEscape,which can simulate the evacuation process for any given occupant distribu. Uon in buildings.Designed as an extensible multi-level structure, the model constructs the geometry level and occupant level and establishes the interactions between levels.The GIS-based environmental analysis is realized to automatically generate the geometric representation and formulate the cognition of agents. The multi-agent based technology is employed to simulate the crowd behaviom with autonomously acting individuals.A visualization component,which provides 3D free observations for the simulation process,is developed on the platform of OGRE and integrated into the system interface in form of ActiveX control.Fi- nally,a case study has been conducted and the results have been compared with the results of an existing model to show the reliability and capacity of AutoEscape simulation.
Validation of 3-D Ice Accretion Measurement Methodology for Experimental Aerodynamic Simulation
Broeren, Andy P.; Addy, Harold E., Jr.; Lee, Sam; Monastero, Marianne C.
2015-01-01
Determining the adverse aerodynamic effects due to ice accretion often relies on dry-air wind-tunnel testing of artificial, or simulated, ice shapes. Recent developments in ice-accretion documentation methods have yielded a laser-scanning capability that can measure highly three-dimensional (3-D) features of ice accreted in icing wind tunnels. The objective of this paper was to evaluate the aerodynamic accuracy of ice-accretion simulations generated from laser-scan data. Ice-accretion tests were conducted in the NASA Icing Research Tunnel using an 18-in. chord, two-dimensional (2-D) straight wing with NACA 23012 airfoil section. For six ice-accretion cases, a 3-D laser scan was performed to document the ice geometry prior to the molding process. Aerodynamic performance testing was conducted at the University of Illinois low-speed wind tunnel at a Reynolds number of 1.8 × 10(exp 6) and a Mach number of 0.18 with an 18-in. chord NACA 23012 airfoil model that was designed to accommodate the artificial ice shapes. The ice-accretion molds were used to fabricate one set of artificial ice shapes from polyurethane castings. The laser-scan data were used to fabricate another set of artificial ice shapes using rapid prototype manufacturing such as stereolithography. The iced-airfoil results with both sets of artificial ice shapes were compared to evaluate the aerodynamic simulation accuracy of the laser-scan data. For five of the six ice-accretion cases, there was excellent agreement in the iced-airfoil aerodynamic performance between the casting and laser-scan based simulations. For example, typical differences in iced-airfoil maximum lift coefficient were less than 3 percent with corresponding differences in stall angle of approximately 1 deg or less. The aerodynamic simulation accuracy reported in this paper has demonstrated the combined accuracy of the laser-scan and rapid-prototype manufacturing approach to simulating ice accretion for a NACA 23012 airfoil. For several
Gas Core Reactor Numerical Simulation Using a Coupled MHD-MCNP Model
Kazeminezhad, F.; Anghaie, S.
2008-01-01
Analysis is provided in this report of using two head-on magnetohydrodynamic (MHD) shocks to achieve supercritical nuclear fission in an axially elongated cylinder filled with UF4 gas as an energy source for deep space missions. The motivation for each aspect of the design is explained and supported by theory and numerical simulations. A subsequent report will provide detail on relevant experimental work to validate the concept. Here the focus is on the theory of and simulations for the proposed gas core reactor conceptual design from the onset of shock generations to the supercritical state achieved when the shocks collide. The MHD model is coupled to a standard nuclear code (MCNP) to observe the neutron flux and fission power attributed to the supercritical state brought about by the shock collisions. Throughout the modeling, realistic parameters are used for the initial ambient gaseous state and currents to ensure a resulting supercritical state upon shock collisions.
SOLAR WIND TURBULENCE FROM MHD TO SUB-ION SCALES: HIGH-RESOLUTION HYBRID SIMULATIONS
Energy Technology Data Exchange (ETDEWEB)
Franci, Luca; Verdini, Andrea; Landi, Simone [Dipartimento di Fisica e Astronomia, Università di Firenze, Largo E. Fermi 2, I-50125 Firenze (Italy); Matteini, Lorenzo [Department of Physics, Imperial College London, London SW7 2AZ (United Kingdom); Hellinger, Petr [Astronomical Institute, AS CR, Bocni II/1401, CZ-14100 Prague (Czech Republic)
2015-05-10
We present results from a high-resolution and large-scale hybrid (fluid electrons and particle-in-cell protons) two-dimensional numerical simulation of decaying turbulence. Two distinct spectral regions (separated by a smooth break at proton scales) develop with clear power-law scaling, each one occupying about a decade in wavenumbers. The simulation results simultaneously exhibit several properties of the observed solar wind fluctuations: spectral indices of the magnetic, kinetic, and residual energy spectra in the magnetohydrodynamic (MHD) inertial range along with a flattening of the electric field spectrum, an increase in magnetic compressibility, and a strong coupling of the cascade with the density and the parallel component of the magnetic fluctuations at sub-proton scales. Our findings support the interpretation that in the solar wind, large-scale MHD fluctuations naturally evolve beyond proton scales into a turbulent regime that is governed by the generalized Ohm’s law.
Implementation of 3D Lattice Monte Carlo Simulation on a Cluster of Symmetric Multiprocessors
Institute of Scientific and Technical Information of China (English)
雷咏梅; 蒋英; 等
2002-01-01
This paper presents a new approach to parallelize 3D lattice Monte Carlo algorithms used in the numerical simulation of polymer on ZiQiang 2000-a cluster of symmetric multiprocessors(SMPs).The combined load for cell and energy calculations over the time step is balanced together to form a single spatial decomposition.Basic aspects and strategies of running Monte Carlo calculations on parallel computers are studied.Different steps involved in porting the software on a parallel architecture based on ZiQiang 2000 running under Linux and MPI are described briefly.It is found that parallelization becomes more advantageous when either the lattice is very large or the model contains many cells and chains.
3D Nonlinear Numerical Simulation of Intact and Debonded Reinforced Concrete Beams
Institute of Scientific and Technical Information of China (English)
Chen Quan(陈权); Marcus L.
2004-01-01
To study the behaviour of reinforced concrete (RC) structures with sections of concrete removed and the reinforcement exposed, 3D nonlinear numerical analysis was performed upon both intact and debonded RC beams by using finite element techniques. The deformational characteristics and the ultimate loads were obtained through numerical models, as well as crack and stress distributions. The failure modes can also be deduced from computational results. Compared with intact beams, the normal assumptions of plane section behaviour is not hold true and the patterns of stress and strain are different in debonded RC beams. The numerical results show good consistency with experimental data. This kind of numerical simulation is a supplement to existing codes.
3-D NUMERICAL SIMULATION OF CONVOY-GENERATED WAVES IN A RESTRICTED WATERWAY
Institute of Scientific and Technical Information of China (English)
JI Sheng Cheng; OUAHSINE Abdellatif; SMAOUI Hassan; SERGENT Philippe
2012-01-01
We consider waves generated by the passing of convoys in a restricted waterway.The magnitude of these waves depends mainly on the geometrical and kinematical parameters of the convoy,such as the speed and the hull geometry.The objective of this study is to predict the relationship between these geometrical and kinematical parameters and the amplitude of ship-generated waves as well as the water plane drawdown.Numerical simulations are conducted by solving the 3-D Navier-Stokes equations along with the standard k-ε model for turbulent processes.The results are compared first with the empirical model and second with experimental measurements performed by the French company Compagnie National du Rh(o)ne (CNR).
Simulation of 3D material flow in friction stir welding of AA6061-T6
Institute of Scientific and Technical Information of China (English)
Zhang Zhao; Zhang Hongwu
2008-01-01
This paper reports the numerical simulation of the 3D material flow in friction stir welding process by using finite element methods based on solid mechanics. It is found that the material flow behind the pin is much faster than that in front of the pin. The material in front of the pin moves upwards and then rotates with the pin due to the effect of the rotating tool. Behind of the pin, the material moves downwards. This process of material movement is the real cause to make the friction stir welding process continuing successfully. With the increase of the translational velocity or the rotational velocity of the pin, the material flow becomes faster.
GPU-advanced 3D electromagnetic simulations of superconductors in the Ginzburg-Landau formalism
Stošić, Darko; Stošić, Dušan; Ludermir, Teresa; Stošić, Borko; Milošević, Milorad V.
2016-10-01
Ginzburg-Landau theory is one of the most powerful phenomenological theories in physics, with particular predictive value in superconductivity. The formalism solves coupled nonlinear differential equations for both the electronic and magnetic responsiveness of a given superconductor to external electromagnetic excitations. With order parameter varying on the short scale of the coherence length, and the magnetic field being long-range, the numerical handling of 3D simulations becomes extremely challenging and time-consuming for realistic samples. Here we show precisely how one can employ graphics-processing units (GPUs) for this type of calculations, and obtain physics answers of interest in a reasonable time-frame - with speedup of over 100× compared to best available CPU implementations of the theory on a 2563 grid.
GPU-advanced 3D electromagnetic simulations of superconductors in the Ginzburg–Landau formalism
Energy Technology Data Exchange (ETDEWEB)
Stošić, Darko; Stošić, Dušan; Ludermir, Teresa [Centro de Informática, Universidade Federal de Pernambuco, Av. Luiz Freire s/n, 50670-901, Recife, PE (Brazil); Stošić, Borko [Departamento de Estatística e Informática, Universidade Federal Rural de Pernambuco, Rua Dom Manoel de Medeiros s/n, Dois Irmãos, 52171-900 Recife, PE (Brazil); Milošević, Milorad V., E-mail: milorad.milosevic@uantwerpen.be [Departement Fysica, Universiteit Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen (Belgium)
2016-10-01
Ginzburg–Landau theory is one of the most powerful phenomenological theories in physics, with particular predictive value in superconductivity. The formalism solves coupled nonlinear differential equations for both the electronic and magnetic responsiveness of a given superconductor to external electromagnetic excitations. With order parameter varying on the short scale of the coherence length, and the magnetic field being long-range, the numerical handling of 3D simulations becomes extremely challenging and time-consuming for realistic samples. Here we show precisely how one can employ graphics-processing units (GPUs) for this type of calculations, and obtain physics answers of interest in a reasonable time-frame – with speedup of over 100× compared to best available CPU implementations of the theory on a 256{sup 3} grid.
Bu, Shuhui; Shiina, Tsuyoshi; Yamakawa, Makoto; Takizawa, Hotaka
Accurate assessment of local myocardial contraction is important for diagnosis of ischemic heart disease, because decreases of myocardial motion often appear in the early stages of the disease. Three-dimensional (3-D) assessment of the stiffness distribution is required for accurate diagnosis of ischemic heart disease. Since myocardium motion occurs radially within the left ventricle wall and the ultrasound beam propagates axially, conventional approaches, such as tissue Doppler imaging and strain-rate imaging techniques, cannot provide us with enough quantitative information about local myocardial contraction. In order to resolve this problem, we propose a novel myocardial contraction imaging system which utilizes the weighted phase gradient method, the extended combined autocorrelation method, and the dynamic grid interpolation (DGI) method. From the simulation results, we conclude that the strain image's accuracy and contrast have been improved by the proposed method.
Cognitive/emotional models for human behavior representation in 3D avatar simulations
Peterson, James K.
2004-08-01
Simplified models of human cognition and emotional response are presented which are based on models of auditory/ visual polymodal fusion. At the core of these models is a computational model of Area 37 of the temporal cortex which is based on new isocortex models presented recently by Grossberg. These models are trained using carefully chosen auditory (musical sequences), visual (paintings) and higher level abstract (meta level) data obtained from studies of how optimization strategies are chosen in response to outside managerial inputs. The software modules developed are then used as inputs to character generation codes in standard 3D virtual world simulations. The auditory and visual training data also enable the development of simple music and painting composition generators which significantly enhance one's ability to validate the cognitive model. The cognitive models are handled as interacting software agents implemented as CORBA objects to allow the use of multiple language coding choices (C++, Java, Python etc) and efficient use of legacy code.
Numerical methods for 3D tokamak simulations using a flux-surface independent grid
Energy Technology Data Exchange (ETDEWEB)
Stegmeir, A.; Coster, D.; Maj, O.; Lackner, K. [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, 85748 Garching (Germany)
2014-06-15
A numerical approach for 3D Tokamak simulations using a flux surface independent grid is presented. The grid consists of few poloidal planes with a Cartesian isotropic grid within each poloidal plane. Perpendicular operators can be discretised within a poloidal plane using standard second order finite difference methods. The discretisation of parallel operators is achieved with a field line following map and an interpolation. The application of the support operator method to the parallel diffusion operator conserves the self-adjointness of the operator on the discrete level and keeps the numerical decay rate at a low level. The developed numerical methods can be applied to geometries where an X-point is present. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Interplay between plasma turbulence and particle injection in 3D global simulations
Energy Technology Data Exchange (ETDEWEB)
Tamain, P.; Baudoin, C.; Ciraolo, G.; Futtersack, R.; Ghendrih, P.; Nace, N. [Association Euratom-CEA, Institut de Recherche sur la Fusion Magnetique, CEA Cadarache, St. Paul-lez-Durance (France); Bufferand, H.; Carbajal, L.; Marandet, Y. [Aix-Marseille Universite, CNRS, PIIM, UMR 7345, Marseille (France); Colin, C.; Galassi, D.; Schwander, F.; Serre, E. [Aix-Marseille Universite, CNRS, Ecole Centrale Marseille, M2P2, Marseille (France)
2016-08-15
The impact of a 3D localized particle source on the edge plasma in 3D global turbulence simulations is investigated using the TOKAM3X fluid code. Results apply to advanced fueling methods such as Supersonic Molecular Beam Injection (SMBI) or pellets injection. The fueling source is imposed as a volumetric particle source in the simulations so that the physics leading to the ionization of particles and its localization are not taken into account. As already observed in experiments, the localized particle source strongly perturbs both turbulence and the large scale organization of the edge plasma. The localized increase of the pressure generated by the source drives sonic parallel flows in the plasma, leading to a poloidal redistribution of the particles on the time scale of the source duration. However, the particle deposition also drives localized transverse pressure gradients which impacts the stability of the plasma with respect to interchange processes. The resulting radial transport occurs on a sufficiently fast time scale to compete with the parallel redistribution of particles, leading to immediate radial losses of a significant proportion of the injected particles. Low Field Side (LFS) and High Field Side (HFS) injections exhibit different dynamics due to their interaction with curvature. In particular, HFS particle deposition drives an inward flux leading to differences in the particle deposition efficiency (higher for HFS than LFS). These results demonstrate the importance of taking into account plasma transport in a self-consistent manner when investigating fueling methods. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Borazjani, Iman; Ge, Liang; Sotiropoulos, Fotis
2008-08-10
The sharp-interface CURVIB approach of Ge and Sotiropoulos [L. Ge, F. Sotiropoulos, A Numerical Method for Solving the 3D Unsteady Incompressible Navier-Stokes Equations in Curvilinear Domains with Complex Immersed Boundaries, Journal of Computational Physics 225 (2007) 1782-1809] is extended to simulate fluid structure interaction (FSI) problems involving complex 3D rigid bodies undergoing large structural displacements. The FSI solver adopts the partitioned FSI solution approach and both loose and strong coupling strategies are implemented. The interfaces between immersed bodies and the fluid are discretized with a Lagrangian grid and tracked with an explicit front-tracking approach. An efficient ray-tracing algorithm is developed to quickly identify the relationship between the background grid and the moving bodies. Numerical experiments are carried out for two FSI problems: vortex induced vibration of elastically mounted cylinders and flow through a bileaflet mechanical heart valve at physiologic conditions. For both cases the computed results are in excellent agreement with benchmark simulations and experimental measurements. The numerical experiments suggest that both the properties of the structure (mass, geometry) and the local flow conditions can play an important role in determining the stability of the FSI algorithm. Under certain conditions unconditionally unstable iteration schemes result even when strong coupling FSI is employed. For such cases, however, combining the strong-coupling iteration with under-relaxation in conjunction with the Aitken's acceleration technique is shown to effectively resolve the stability problems. A theoretical analysis is presented to explain the findings of the numerical experiments. It is shown that the ratio of the added mass to the mass of the structure as well as the sign of the local time rate of change of the force or moment imparted on the structure by the fluid determine the stability and convergence of the FSI
3D simulations of young core-collapse supernova remnants undergoing efficient particle acceleration
Ferrand, Gilles
2016-01-01
Within our Galaxy, supernova remnants are believed to be the major sources of cosmic rays up to the "knee". However important questions remain regarding the share of the hadronic and leptonic components, and the fraction of the supernova energy channelled into these components. We address such question by the means of numerical simulations that combine a hydrodynamic treatment of the shock wave with a kinetic treatment of particle acceleration. Performing 3D simulations allows us to produce synthetic projected maps and spectra of the thermal and non-thermal emission, that can be compared with multi-wavelength observations (in radio, X-rays, and gamma-rays). Supernovae come in different types, and although their energy budget is of the same order, their remnants have different properties, and so may contribute in different ways to the pool of Galactic cosmic-rays. Our first simulations were focused on thermonuclear supernovae, like Tycho's SNR, that usually occur in a mostly undisturbed medium. Here we present...
3D optical simulation formalism OPTOS for textured silicon solar cells.
Tucher, Nico; Eisenlohr, Johannes; Kiefel, Peter; Höhn, Oliver; Hauser, Hubert; Peters, Marius; Müller, Claas; Goldschmidt, Jan Christoph; Bläsi, Benedikt
2015-11-30
In this paper we introduce the three-dimensional formulation of the OPTOS formalism, a matrix-based method that allows for the efficient simulation of non-coherent light propagation and absorption in thick textured sheets. As application examples, we calculate the absorptance of solar cells featuring textures on front and rear side with different feature sizes operating in different optical regimes. A discretization of polar and azimuth angle enables a three-dimensional description of systems with arbitrary surface textures. We present redistribution matrices for 3D surface textures, including pyramidal textures, binary crossed gratings and a Lambertian scatterer. The results of the OPTOS simulations for silicon sheets with different combinations of these surfaces are in accordance with both optical measurements and results based on established simulation methods like ray tracing. Using OPTOS, we show that the integration of a diffractive grating at the rear side of a silicon solar cell featuring a pyramidal front side results in absorption close to the Yablonovitch Limit enhancing the photocurrent density by 0.6 mA/cm2 for a 200 µm thick cell.
The Making of FR Is I. Numerical Hydrodynamic 3D Simulations of Low Power Jets
Massaglia, S; Rossi, P; Capetti, S; Mignone, A
2016-01-01
Extragalactic radiosources have been classified in two classes, Fanaroff-Riley I and II, which differ in morphology and radio power. Strongly emitting sources belong to the edge brightened FR II class while the weak ones to the edge darkened FR I class. The origin of this dichotomy is not yet fully understood. Numerical simulations are successful in generating FR~II morphologies but they fail to reproduce the diffuse structure of FR Is. By means of hydro-dynamical 3D simulations of supersonic jets, we investigate how the displayed morphologies depend on the jet parameters. Bow shocks and Mach disks at the jet's head, likely responsible for the presence of hot spots in the FR II sources, disappear for a jet kinetic power less than 10^43 erg/s. This threshold compares favorably with the luminosity at which the FR~I/FR~II transition is observed. The problem is addressed by numerical means carrying out three-dimensional HD simulations of supersonic jets that propagate in a non homogeneous medium with the ambient ...
3-D simulation of gases transport under condition of inert gas injection into goaf
Liu, Mao-Xi; Shi, Guo-Qing; Guo, Zhixiong; Wang, Yan-Ming; Ma, Li-Yang
2016-12-01
To prevent coal spontaneous combustion in mines, it is paramount to understand O2 gas distribution under condition of inert gas injection into goaf. In this study, the goaf was modeled as a 3-D porous medium based on stress distribution. The variation of O2 distribution influenced by CO2 or N2 injection was simulated based on the multi-component gases transport and the Navier-Stokes equations using Fluent. The numerical results without inert gas injection were compared with field measurements to validate the simulation model. Simulations with inert gas injection show that CO2 gas mainly accumulates at the goaf floor level; however, a notable portion of N2 gas moves upward. The evolution of the spontaneous combustion risky zone with continuous inert gas injection can be classified into three phases: slow inerting phase, rapid accelerating inerting phase, and stable inerting phase. The asphyxia zone with CO2 injection is about 1.25-2.4 times larger than that with N2 injection. The efficacy of preventing and putting out mine fires is strongly related with the inert gas injecting position. Ideal injections are located in the oxidation zone or the transitional zone between oxidation zone and heat dissipation zone.
Fang, Qianqian; Boas, David A
2009-10-26
We report a parallel Monte Carlo algorithm accelerated by graphics processing units (GPU) for modeling time-resolved photon migration in arbitrary 3D turbid media. By taking advantage of the massively parallel threads and low-memory latency, this algorithm allows many photons to be simulated simultaneously in a GPU. To further improve the computational efficiency, we explored two parallel random number generators (RNG), including a floating-point-only RNG based on a chaotic lattice. An efficient scheme for boundary reflection was implemented, along with the functions for time-resolved imaging. For a homogeneous semi-infinite medium, good agreement was observed between the simulation output and the analytical solution from the diffusion theory. The code was implemented with CUDA programming language, and benchmarked under various parameters, such as thread number, selection of RNG and memory access pattern. With a low-cost graphics card, this algorithm has demonstrated an acceleration ratio above 300 when using 1792 parallel threads over conventional CPU computation. The acceleration ratio drops to 75 when using atomic operations. These results render the GPU-based Monte Carlo simulation a practical solution for data analysis in a wide range of diffuse optical imaging applications, such as human brain or small-animal imaging.
Simulation of water temperature in two reservoirs with Delft3d
Yang, J. Y.; Zhou, L. Y.
2016-08-01
The proposeled Guanjingkou and Fengdou reservoir will be constructed at Chongqing city and Muling city in China respectively. The water temperature in the reservoir, in the downstream, and the aquatic ecosystem would be altered by the construction of the reservoirs. This paper simulates the water temperature in the two reservoirs by using the Delft3d z-layer model, which uses the fixed elevation for layers. According to the simulation results, the temperature profile in the reservoirs can be divided into three layers: the upmost epilimnion layer, the beneathed thermocline layer, and the constant tepmerature layer at bottom. The temperature effects can be reduced by measurements of stoplogs gates and mutiple gates, respectively. Based on the simulation results in the wet, nomal, and dry year, the temperature of water released from the stoplogs gates at Guanjingkou reservior can be respectively increased by 5.7°C, 6.8°C, 9.6°C, and 5.5°C in the irrigation season from May to August. The temperature of water released from the mutiple gates at Fengdou reservior can be respectively increased by 7.7 °C, 1.9 °C, 9.5 °C, and 10.1 °C from May to August. The negative impacts from the water with lower temperature on the related ecosystem can be significently alleviated.
Numerical simulation of unsteady flow characteristics for cavitation around a 3-D hydrofoil
Ahn, S. H.; Xiao, Y. X.; Wang, Z. W.
2015-01-01
At present it is possible to predict more accurately by various numerical methods established for cavitation simulation around a hydrofoil. However, for the solution of the complex unsteady cavity flow, it is still marginal. In this paper, numerical method is adopted to simulate cavitation around 3-D NACA0015 hydrofoil with homogeneous two-phase flow calculation using commercial code CFX-solver with two turbulence models, the standard RNG k-epsilon turbulence model and the modified RNG k-epsilon turbulence model respectively. First, pressure coefficient for non-cavitating flow, time averaged values of unsteady cavity flow around a hydrofoil are verified to simulate more closely to an actual cavity flow. And then frequency analysis is performed with Fast Fourier Transform. The results show that the calculation results with modified RNG k-epsilon turbulence model agree with experimental results in terms of mean cavity length and pressure drop, but the unsteady flow characteristics of oscillating cavitation still deviate slightly in terms of unsteady cavity flow.
Institute of Scientific and Technical Information of China (English)
刘柏鑫; 任婷婷
2016-01-01
研究三维不可压双流体MHD方程Cauchy问题，给出该问题在小初值条件下解的整体存在性结果。%This paper deals with the Cauchy pronlems of 3D two-fluid MHD model. The global well-posedness is obtained under the two-fluid MHD model.
Energy Technology Data Exchange (ETDEWEB)
Deng, Wei [Los Alamos National Laboratory
2015-07-21
The question of the energy composition of the jets/outflows in high-energy astrophysical systems, e.g. GRBs, AGNs, is taken up first: Matter-flux-dominated (MFD), σ < 1, and/or Poynting-flux-dominated (PFD), σ >1? The standard fireball IS model and dissipative photosphere model are MFD, while the ICMART (Internal-Collision-induced MAgnetic Reconnection and Turbulence) model is PFD. Motivated by ICMART model and other relevant problems, such as “jets in a jet” model of AGNs, the author investigates the models from the EMF energy dissipation efficiency, relativistic outflow generation, and σ evolution points of view, and simulates collisions between high-σ blobs to mimic the situation of the interactions inside the PFD jets/outflows by using a 3D SRMHD code which solves the conservative form of the ideal MHD equations. σ_{b,f} is calculated from the simulation results (threshold = 1). The efficiency obtained from this hybrid method is similar to the efficiency got from the energy evolution of the simulations (35.2%). Efficiency is nearly σ independent, which is also confirmed by the hybrid method. σ_{b,i} - σ_{b,f} provides an interesting linear relationship. Results of several parameter studies of EMF energy dissipation efficiency are shown.
Real-Time Climate Simulations in the Interactive 3D Game Universe Sandbox ²
Goldenson, N. L.
2014-12-01
Exploration in an open-ended computer game is an engaging way to explore climate and climate change. Everyone can explore physical models with real-time visualization in the educational simulator Universe Sandbox ² (universesandbox.com/2), which includes basic climate simulations on planets. I have implemented a time-dependent, one-dimensional meridional heat transport energy balance model to run and be adjustable in real time in the midst of a larger simulated system. Universe Sandbox ² is based on the original game - at its core a gravity simulator - with other new physically-based content for stellar evolution, and handling collisions between bodies. Existing users are mostly science enthusiasts in informal settings. We believe that this is the first climate simulation to be implemented in a professionally developed computer game with modern 3D graphical output in real time. The type of simple climate model we've adopted helps us depict the seasonal cycle and the more drastic changes that come from changing the orbit or other external forcings. Users can alter the climate as the simulation is running by altering the star(s) in the simulation, dragging to change orbits and obliquity, adjusting the climate simulation parameters directly or changing other properties like CO2 concentration that affect the model parameters in representative ways. Ongoing visuals of the expansion and contraction of sea ice and snow-cover respond to the temperature calculations, and make it accessible to explore a variety of scenarios and intuitive to understand the output. Variables like temperature can also be graphed in real time. We balance computational constraints with the ability to capture the physical phenomena we wish to visualize, giving everyone access to a simple open-ended meridional energy balance climate simulation to explore and experiment with. The software lends itself to labs at a variety of levels about climate concepts including seasons, the Greenhouse effect
Easy, Luke; Omotani, John; Dudson, Benjamin; Havlíčková, Eva; Tamain, Patrick; Naulin, Volker; Nielsen, Anders H
2014-01-01
This paper presents simulations of isolated 3D filaments in a slab geometry obtained using a 3D reduced fluid code. First, systematic scans were performed to investigate how the dynamics of a filament are affected by its amplitude, perpendicular size and parallel extent. The perpendicular size of the filament was found to have a strong influence on its motions, as it determined the relative importance of parallel currents to polarisation and viscous currents, whilst drift-wave instabilities were observed if the initial amplitude of the blob was increased sufficiently. Next, the 3D simulations were compared to 2D simulations using different parallel closures; namely, the sheath dissipation closure, which neglects parallel gradients, and the vorticity advection closure, which neglects the influence of parallel currents. The vorticity advection closure was found to not replicate the 3D perpendicular dynamics and overestimated the initial radial acceleration of all the filaments studied. In contrast, a more satis...
Coyac, Antoine; Riviere, Nicolas; Hespel, Laurent; Briottet, Xavier
2016-05-01
In this paper, we show the feasibility and the benefit to use a Geiger-mode Avalanche Photo-Diode (GmAPD) array for long range detection, up to several kilometers. A simulation of a Geiger detection sensor is described, which is a part of our end-to-end laser simulator, to generate simulated 3D laser images from synthetic scenes. Resulting 3D point clouds have been compared to experimental acquisitions, performed with our GmAPD 3D camera on similar scenarios. An operational case of long range detection is presented: a copper cable outstretched above the ground, 1 kilometer away the experimental system and with a horizontal line-of-sight (LOS). The detection of such a small object from long distance observation strongly suggests that GmAPD focal plane arrays could be easily used for real-time 3D mapping or surveillance applications from airborne platforms, with good spatial and temporal resolutions.
Compressible magma/mantle dynamics: 3-D, adaptive simulations in ASPECT
Dannberg, Juliane; Heister, Timo
2016-12-01
Melt generation and migration are an important link between surface processes and the thermal and chemical evolution of the Earth's interior. However, their vastly different timescales make it difficult to study mantle convection and melt migration in a unified framework, especially for 3-D global models. And although experiments suggest an increase in melt volume of up to 20 per cent from the depth of melt generation to the surface, previous computations have neglected the individual compressibilities of the solid and the fluid phase. Here, we describe our extension of the finite element mantle convection code ASPECT that adds melt generation and migration. We use the original compressible formulation of the McKenzie equations, augmented by an equation for the conservation of energy. Applying adaptive mesh refinement to this type of problems is particularly advantageous, as the resolution can be increased in areas where melt is present and viscosity gradients are high, whereas a lower resolution is sufficient in regions without melt. Together with a high-performance, massively parallel implementation, this allows for high-resolution, 3-D, compressible, global mantle convection simulations coupled with melt migration. We evaluate the functionality and potential of this method using a series of benchmarks and model setups, compare results of the compressible and incompressible formulation, and show the effectiveness of adaptive mesh refinement when applied to melt migration. Our model of magma dynamics provides a framework for modelling processes on different scales and investigating links between processes occurring in the deep mantle and melt generation and migration. This approach could prove particularly useful applied to modelling the generation of komatiites or other melts originating in greater depths. The implementation is available in the Open Source ASPECT repository.
Lapenta, Giovanni; Goldman, Martin; Newman, David; olshevskyi, Vyacheslav; Markidis, Stefano
2016-04-01
Dipolarization fronts (DF) are formed by reconnection outflows interacting with the pre-existing environment. These regions are host of important energy exchanges [1], particle acceleration [2] and a complex structure and evolution [3]. Our recent work has investigated these regions via fully kinetic 3D simulations [4]. As reported recently on Nature Physics [3], based on 3D fully kinetic simulations started with a well defined x-line, we observe that in the DF reconnection transitions towards a more chaotic regime. In the fronts an instability devel- ops caused by the local gradients of the density and by the unfavourable acceleration and field line curvature. The consequence is the break up of the fronts in a fashion similar to the classical fluid Rayleigh-Taylor instability with the formation of "fingers" of plasma and embedded magnetic fields. These fingers interact and produce secondary reconnection sites. We present several different diagnostics that prove the existence of these secondary reconnection sites. Each site is surrounded by its own electron diffusion region. At the fronts the ions are generally not magnetized and considerable ion slippage is present. The discovery we present is that electrons are also slipping, forming localized diffusion regions near secondary reconnection sites [1]. The consequence of this discovery is twofold. First, the instability in the fronts has strong energetic implications. We observe that the energy transfer locally is very strong, an order of magnitude stronger than in the "X" line. However, this energy transfer is of both signs as it is natural for a wavy rippling with regions of magnetic to kinetic and regions of kinetic to magnetic energy conversion. Second, and most important for this session, is that MMS should not limit the search for electron diffusion regions to the location marked with X in all reconnection cartoons. Our simulations predict more numerous and perhaps more easily measurable electron diffusion
Di Renzo, Valeria; Wohletz, Kenneth; Civetta, Lucia; Moretti, Roberto; Orsi, Giovanni; Gasparini, Paolo
2016-12-01
We illustrate a quantitative conductive/convective thermal model incorporating a wide range of geophysical, petrological, geological, geochemical and isotopical observations that constrain the thermal evolution and present state of the Campi Flegrei caldera (CFc) magmatic system. The proposed model has been computed on the basis of the current knowledge of: (1) the volcanic and magmatic history of the volcano over the last 44 ka, (2) its underlying crustal structure, and (3) the physical properties of the erupted magmas. 3D numerical simulations of heat conduction and convection within heterogeneous rock/magma materials with evolving heat sources and boundary conditions that simulate magma rise from a deep (≥ 8 km depth) to shallow (2-6 km) reservoirs, magma chamber formation, magma extrusion, caldera collapse, and intra-caldera hydrothermal convection, have been carried out. The evolution of the CFc magmatic system through time has been simulated through different steps related to its changes in terms of depth, location and size of magma reservoirs and their replenishment. The thermal modeling results show that both heat conduction and convection have played an important role in the CFc thermal evolution, although with different timing. The simulated present heat distribution is in agreement with the measured geothermal profiles (Agip, 1987), reproduces the thermal gradient peaks at the CFc margins in correspondence to the anomalies in surface gradients (Corrado et al., 1998), and suggests temperatures of 700 °C at depth of 4 km in the central portion of the caldera, in agreement with the estimated temperature for the brittle-ductile transition (Hill, 1992).
Nonlinear 3-D simulation of high-intensity focused ultrasound therapy in the kidney
Suomi, Visa; Treeby, Bradley; Cleveland, Robin
2016-01-01
Kidney cancer is a severe disease which can be treated non-invasively using high-intensity focused ultrasound (HIFU) therapy. However, tissue in front of the transducer and the deep location of kidney can cause significant losses to the efficiency of the treatment. The effect of attenuation, refraction and reflection due to different tissue types on HIFU therapy of the kidney was studied using a nonlinear ultrasound simulation model. The geometry of the tissue was derived from a computed tomography (CT) dataset of a patient which had been segmented for water, bone, soft tissue, fat and kidney. The combined effect of inhomogeneous attenuation and sound-speed was found to result in an 11.0 dB drop in spatial peak-temporal average (SPTA) intensity in the kidney compared to pure water. The simulation without refraction effects showed a 6.3 dB decrease indicating that both attenuation and refraction contribute to the loss in focal intensity. The losses due to reflections at soft tissue interfaces were less than 0....
A 3D numerical simulation of different phases of friction stir welding
Guerdoux, S.; Fourment, L.
2009-10-01
An adaptive arbitrary Lagrangian-Eulerian formulation is developed to compute the material flow and the temperature evolution during the three phases of the friction stir welding (FSW) process. It follows a splitting approach: after the calculations of the velocity/pressure and temperature fields, the mesh velocity is derived from the domain boundary evolution and from an adaptive refinement criterion provided by error estimation, and finally state variables are remapped. In this way, the unilateral contact conditions between the plate and the tool are accurately taken into account, so allowing one to model various instabilities that may occur during the process, such as the role played by the plunge depth of the tool on the formations of flashes, the possible appearance of non-steady voids or tunnel holes and the influence of the threads on the material flow, the temperature field and the welding efforts. This formulation is implemented in the 3D Forge3 FE software with automatic remeshing. The non-steady phases of FSW can so be simulated, as well as the steady welding phase. The study of different process conditions shows that the main phenomena taking place during FSW can be simulated with the right sensitivities.
Study on 3D simulation of wave fields in acoustic reflection image logging
Institute of Scientific and Technical Information of China (English)
2008-01-01
The borehole acoustic reflection imaging logging is a newly developed acoustic logging method that has attracted many interests. These converted and reflected waves for imaging are usually mixed up with borehole guided waves and therefore difficult to be clearly identified. To improve the downhole tool design and develop more sophisticate data processing and interpretation algorithms,studies on precisely numerical modeling of the wave fields in the acoustic reflection imaging logging are neces-sary and critical. This paper developed a parallelized scheme of 3D finite difference (3DFD) with non-uniform staggered grid and PML absorbing boundary to simulate the acoustic wave fields in isotropic and anisotropic formations. Applications of this scheme to the typical cases of isotropic and anisot-ropic formations and comparison with the results from published analytical solutions have demon-strated the validation and efficiency of the scheme. Higher accuracy and lower computation cost (3.5 times faster than the conventional schemes) have been achieved with this scheme for modeling such a complex wave fields of 60 dB dynamic range with higher frequency (10 kHz). This simulating program provides a quantitative analytical means for studying acoustic reflection imaging tool and development of the data processing and interpretation methods.
Parallel 3-d simulations for porous media models in soil mechanics
Wieners, C.; Ammann, M.; Diebels, S.; Ehlers, W.
Numerical simulations in 3-d for porous media models in soil mechanics are a difficult task for the engineering modelling as well as for the numerical realization. Here, we present a general numerical scheme for the simulation of two-phase models in combination with an material model via the stress response with a specialized parallel saddle point solver. Therefore, we give a brief introduction into the theoretical background of the Theory of Porous Media and constitute a two-phase model consisting of a porous solid skeleton saturated by a viscous pore-fluid. The material behaviour of the skeleton is assumed to be elasto-viscoplastic. The governing equations are transfered to a weak formulation suitable for the application of the finite element method. Introducing an formulation in terms of the stress response, we define a clear interface between the assembling process and the parallel solver modules. We demonstrate the efficiency of this approach by challenging numerical experiments realized on the Linux Cluster in Chemnitz.
Comparison of plasma data from ASPERA-3/Mars-Express with a 3-D hybrid simulation
Directory of Open Access Journals (Sweden)
A. Bößwetter
2007-08-01
Full Text Available The ELS and IMA sensors of the ASPERA-3 experiment onboard of Mars-Express (MEX can measure electron as well as ion moments. We compare these measurements for a specific orbit with the simulation results from a 3-D hybrid model. In the hybrid approximation the electrons are modeled as a massless charge-neutralizing fluid, whereas the ions are treated as individual particles. This approach allows gyroradius effects to be included in our model calculations of the Martian plasma environment because the gyroradii of the solar wind protons are in the range of several hundred kilometers and therefore comparable with the characteristic scales of the subsolar ionospheric interaction region. The position of both the bow shock and the Ion Composition Boundary (ICB manifest in the MEX data as well as in the results from the hybrid simulation nearly at the same location. The characteristic features of these boundaries, i.e. an increase of proton density and temperature at the Bow Shock and a transition from solar wind to ionospheric particles at the ICB, are clearly identifiable in the data.
EMPulse, a new 3-D simulation code for electromagnetic pulse studies
Cohen, Bruce; Eng, Chester; Farmer, William; Friedman, Alex; Grote, David; Kruger, Hans; Larson, David
2016-10-01
EMPulse is a comprehensive and modern 3-D simulation code for electro-magnetic pulse (EMP) formation and propagation studies, being developed at LLNL as part of a suite of codes to study E1 EMP originating from prompt gamma rays. EMPulse builds upon the open-source Warp particle-in-cell code framework developed by members of this team and collaborators at other institutions. The goal of this endeavor is a new tool enabling the detailed and self-consistent study of multi-dimensional effects in geometries that have typically been treated only approximately. Here we present an overview of the project, the models and methods that have been developed and incorporated into EMPulse, tests of these models, comparisons to simulations undertaken in CHAP-lite (derived from the legacy code CHAP due to C. Longmire and co-workers), and some approaches to increased computational efficiency being studied within our project. This work was performed under the auspices of the U.S. DOE by Lawrence Livermore National Security, LLC, Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Statistical Analysis of Detailed 3-D CFD LES Simulations with Regard to CCV Modeling
Directory of Open Access Journals (Sweden)
Vítek Oldřich
2016-06-01
Full Text Available The paper deals with statistical analysis of large amount of detailed 3-D CFD data in terms of cycle-to-cycle variations (CCVs. These data were obtained by means of LES calculations of many consecutive cycles. Due to non-linear nature of Navier-Stokes equation set, there is a relatively significant CCV. Hence, every cycle is slightly different – this leads to requirement to perform statistical analysis based on ensemble averaging procedure which enables better understanding of CCV in ICE including its quantification. The data obtained from the averaging procedure provides results on different space resolution levels. The procedure is applied locally, i.e., in every cell of the mesh. Hence there is detailed CCV information on local level – such information can be compared with RANS simulations. Next, volume/mass averaging provides information at specific locations – e.g., gap between electrodes of a spark plug. Finally, volume/mass averaging of the whole combustion chamber leads to global information which can be compared with experimental data or results of system simulation tools (which are based on 0-D/1-D approach.
3D Simulation of Spindle Gravitational Collapse of a Collisionless Particle System
Yoo, Chul-Moon; Okawa, Hirotada
2016-01-01
We simulate the spindle gravitational collapse of a collisionless particle system in a 3D numerical relativity code and compare the qualitative results with the old work done by Shapiro and Teukolsky(ST). The simulation starts from the prolate-shaped distribution of particles and a spindle collapse is observed. The peak value and its spatial position of curvature invariants are monitored during the time evolution. We find that the peak value of the Kretschmann invariant takes a maximum at some moment, when there is no apparent horizon, and its value is greater for finer resolution, which is consistent with what is reported in ST. We also find a similar tendency for the Weyl curvature invariant. Therefore, our results lend support to the formation of a naked singularity as a result of the spindle collapse of a collisionless particle system in the limit of infinite resolution. However, unlike in ST, our code does not break down then but go well beyond. We find that the peak values of the curvature invariants st...
Self-consistent 3D simulations of longitudinal halo in rf -linacs
Energy Technology Data Exchange (ETDEWEB)
Barnard, J J; Lund, S M; Ryne, R D
1998-08-19
In order to prevent activation of the beam pipe walls and components of a high power ion accelera- tor: beam loss must be minimized. Here we present self-consistent, 3D particle-in-cell simulations of longi- tudinally mismatched beams including the effects of rf non-linearities using parameters based on the Acceler- ator Production of Tritium linac design. In particular, we explore the evolution of the longitudinal halo distri- bution, i.e., the distribution of particles in longitudinal phase space with oscillation amplitudes significantly larger than amplitudes of particles in the main body or ''core'' of the beam. When a particle reaches a suf- ficiently large amplitude longitudinally it can he lost from the rf bucket and consequently loses synchro- nism with thr rf wave. Such particles will lose energy and so be poorly matched to the transverse focusing field and consequently can be lost transversely. We compare the present simulations in which all particles contribute self-consistently to the self-field to predic- tions of a core/test particle model in which the core distribution has uniformly distributed charge and does not evolve self-consistently. Effects of self-consistent, non-linear space-charge forces, non-linear rf focusing on envelope mismatch induced beam halo are explored through comparisons of both models.
Taha, Uday; Shabeeb, Ahmed; dragonetti, giovanna; Lamaddalena, Nicola; Coppola, Antonio
2016-04-01
This work analyzed the variability of sprinkler irrigation application over a bare soil, both in terms of water application efficiency and uniformity, by integrating and comparing the information on the irrigation depth data (ID), as measured by catch cans, soil water storage in the upper root zone, as measured by TDR probes, and a 3D simulations of water flow in soils. Three irrigation tests were performed at three different pressures (2, 3 and 4 bar). A lateral water redistribution was observed and simulated after each irrigation event by comparing spatial distributions of site-specific water application efficiency (AEs), as well as ratios of site-specific actual water storage increase (SWEs) and irrigation depth (IDs) to the water content before irrigation. Because of soil water redistribution processes, distribution uniformity based on soil storages was systematically higher than the catch can uniformity. The obvious consequence of lateral water redistribution processes was that the soil smoothing action on non-uniformity observed at the surface increased both with depth and over time. At a given depth the uniformity of soil water storages always attained the same value, whatever the pressure considered and the catch can-based uniformity coefficient. It was concluded that, for the case of random distribution of ID, the uniformity of water storages is driven by the soil behavior rather than by the irrigation system.
Linear Simulations of the Cylindrical Richtmyer-Meshkov Instability in Hydrodynamics and MHD
Gao, Song
2013-05-01
The Richtmyer-Meshkov instability occurs when density-stratified interfaces are impulsively accelerated, typically by a shock wave. We present a numerical method to simulate the Richtmyer-Meshkov instability in cylindrical geometry. The ideal MHD equations are linearized about a time-dependent base state to yield linear partial differential equations governing the perturbed quantities. Convergence tests demonstrate that second order accuracy is achieved for smooth flows, and the order of accuracy is between first and second order for flows with discontinuities. Numerical results are presented for cases of interfaces with positive Atwood number and purely azimuthal perturbations. In hydrodynamics, the Richtmyer-Meshkov instability growth of perturbations is followed by a Rayleigh-Taylor growth phase. In MHD, numerical results indicate that the perturbations can be suppressed for sufficiently large perturbation wavenumbers and magnetic fields.
Extension of the MURaM radiative MHD code for coronal simulations
Rempel, Matthias
2016-01-01
We present a new version of the MURaM radiative MHD code that allows for simulations spanning from the upper convection zone into the solar corona. We implemented the relevant coronal physics in terms of optically thin radiative loss, field aligned heat conduction and an equilibrium ionization equation of state. We artificially limit the coronal Alfv{\\'e}n and heat conduction speeds to computationally manageable values using an approximation to semi-relativistic MHD with an artificially reduced speed of light (Boris correction). We present example solutions ranging from quiet to active Sun in order to verify the validity of our approach. We quantify the role of numerical diffusivity for the effective coronal heating. We find that the (numerical) magnetic Prandtl number determines the ratio of resistive to viscous heating and that owing to the very large magnetic Prandtl number of the solar corona, heating is expected to happen predominantly through viscous dissipation. We find that reasonable solutions can be...
FTE Dependence on IMF Orientation and Presence of Hall Physics in Global MHD Simulations
Maynard, K. M.; Germaschewski, K.; Lin, L.; Raeder, J.
2013-12-01
Flux Transfer Events (FTEs) are poleward traveling flux ropes that form in the dayside magnetopause and represent significant coupling of the solar wind to the magnetosphere during times of southward IMF. In the 35 years since their discovery, FTEs have been extensively observed and modeled; however, there is still no consensus on their generation mechanism. Previous modeling efforts have shown that FTE occurrence and size depend on the resistivity model that is used in simulations and the structure of X-lines in the magnetopause. We use Hall OpenGGCM, a global Hall-MHD code, to study the formation and propagation of FTEs in the dayside magnetopause using synthetic solar wind conditions. We examine large scale FTE structure and nearby magnetic separators for a range of IMF clock angles and dipole tilts. In addition, we investigate how FTE formation and recurrence rate depends on the presence of the Hall term in the generalized Ohm's law compared with resistive MHD.
Yu, Peicheng; Xu, Xinlu; Davidson, Asher; Tableman, Adam; Dalichaouch, Thamine; Li, Fei; Meyers, Michael D.; An, Weiming; Tsung, Frank S.; Decyk, Viktor K.; Fiuza, Frederico; Vieira, Jorge; Fonseca, Ricardo A.; Lu, Wei; Silva, Luis O.; Mori, Warren B.
2016-07-01
When modeling laser wakefield acceleration (LWFA) using the particle-in-cell (PIC) algorithm in a Lorentz boosted frame, the plasma is drifting relativistically at βb c towards the laser, which can lead to a computational speedup of ∼ γb2 = (1 - βb2)-1. Meanwhile, when LWFA is modeled in the quasi-3D geometry in which the electromagnetic fields and current are decomposed into a limited number of azimuthal harmonics, speedups are achieved by modeling three dimensional (3D) problems with the computational loads on the order of two dimensional r - z simulations. Here, we describe a method to combine the speedups from the Lorentz boosted frame and quasi-3D algorithms. The key to the combination is the use of a hybrid Yee-FFT solver in the quasi-3D geometry that significantly mitigates the Numerical Cerenkov Instability (NCI) which inevitably arises in a Lorentz boosted frame due to the unphysical coupling of Langmuir modes and EM modes of the relativistically drifting plasma in these simulations. In addition, based on the space-time distribution of the LWFA data in the lab and boosted frame, we propose to use a moving window to follow the drifting plasma, instead of following the laser driver as is done in the LWFA lab frame simulations, in order to further reduce the computational loads. We describe the details of how the NCI is mitigated for the quasi-3D geometry, the setups for simulations which combine the Lorentz boosted frame, quasi-3D geometry, and the use of a moving window, and compare the results from these simulations against their corresponding lab frame cases. Good agreement is obtained among these sample simulations, particularly when there is no self-trapping, which demonstrates it is possible to combine the Lorentz boosted frame and the quasi-3D algorithms when modeling LWFA. We also discuss the preliminary speedups achieved in these sample simulations.
Ngirmang, Gregory K; Feister, Scott; Morrison, John T; Chowdhury, Enam A; Frische, Kyle; Roquemore, W M
2015-01-01
We present 3D Particle-in-Cell (PIC) modeling of an ultra-intense laser experiment by the Extreme Light group at the Air Force Research Laboratory (AFRL) using the PIC code LSP. This is the first time PIC simulations have been performed in 3D for this experiment which involves an ultra-intense, short-pulse (30 fs) laser interacting with a water jet target at normal incidence. These 3D PIC simulation results are compared to results from 2D(3$v$) PIC simulations for both $5.4\\cdot10^{17}$ W cm$^{-2}$ and $3\\cdot10^{18}$ W cm$^{-2}$ intensities. Comparing the 2D(3$v$) and 3D simulation results, the laser-energy-to-ejected-electron-energy conversion efficiencies were comparable, but the angular distribution of ejected electrons show interesting differences with qualitative differences at higher intensity. An analytic plane-wave model is provided that provides some explanation for the angular distribution and energies of ejected electrons in the 2D(3$v$) simulations. We also performed a 3D simulation with circular...
From micro-scale 3D simulations to macro-scale model of periodic porous media
Crevacore, Eleonora; Tosco, Tiziana; Marchisio, Daniele; Sethi, Rajandrea; Messina, Francesca
2015-04-01
In environmental engineering, the transport of colloidal suspensions in porous media is studied to understand the fate of potentially harmful nano-particles and to design new remediation technologies. In this perspective, averaging techniques applied to micro-scale numerical simulations are a powerful tool to extrapolate accurate macro-scale models. Choosing two simplified packing configurations of soil grains and starting from a single elementary cell (module), it is possible to take advantage of the periodicity of the structures to reduce the computation costs of full 3D simulations. Steady-state flow simulations for incompressible fluid in laminar regime are implemented. Transport simulations are based on the pore-scale advection-diffusion equation, that can be enriched introducing also the Stokes velocity (to consider the gravity effect) and the interception mechanism. Simulations are carried on a domain composed of several elementary modules, that serve as control volumes in a finite volume method for the macro-scale method. The periodicity of the medium involves the periodicity of the flow field and this will be of great importance during the up-scaling procedure, allowing relevant simplifications. Micro-scale numerical data are treated in order to compute the mean concentration (volume and area averages) and fluxes on each module. The simulation results are used to compare the micro-scale averaged equation to the integral form of the macroscopic one, making a distinction between those terms that could be computed exactly and those for which a closure in needed. Of particular interest it is the investigation of the origin of macro-scale terms such as the dispersion and tortuosity, trying to describe them with micro-scale known quantities. Traditionally, to study the colloidal transport many simplifications are introduced, such those concerning ultra-simplified geometry that usually account for a single collector. Gradual removal of such hypothesis leads to a
Understanding the core-halo relation of quantum wave dark matter from 3D simulations.
Schive, Hsi-Yu; Liao, Ming-Hsuan; Woo, Tak-Pong; Wong, Shing-Kwong; Chiueh, Tzihong; Broadhurst, Tom; Hwang, W-Y Pauchy
2014-12-31
We examine the nonlinear structure of gravitationally collapsed objects that form in our simulations of wavelike cold dark matter, described by the Schrödinger-Poisson (SP) equation with a particle mass ∼10(-22) eV. A distinct gravitationally self-bound solitonic core is found at the center of every halo, with a profile quite different from cores modeled in the warm or self-interacting dark matter scenarios. Furthermore, we show that each solitonic core is surrounded by an extended halo composed of large fluctuating dark matter granules which modulate the halo density on a scale comparable to the diameter of the solitonic core. The scaling symmetry of the SP equation and the uncertainty principle tightly relate the core mass to the halo specific energy, which, in the context of cosmological structure formation, leads to a simple scaling between core mass (Mc) and halo mass (Mh), Mc∝a(-1/2)Mh(1/3), where a is the cosmic scale factor. We verify this scaling relation by (i) examining the internal structure of a statistical sample of virialized halos that form in our 3D cosmological simulations and by (ii) merging multiple solitons to create individual virialized objects. Sufficient simulation resolution is achieved by adaptive mesh refinement and graphic processing units acceleration. From this scaling relation, present dwarf satellite galaxies are predicted to have kiloparsec-sized cores and a minimum mass of ∼10(8)M⊙, capable of solving the small-scale controversies in the cold dark matter model. Moreover, galaxies of 2×10(12)M⊙ at z=8 should have massive solitonic cores of ∼2×10(9)M⊙ within ∼60 pc. Such cores can provide a favorable local environment for funneling the gas that leads to the prompt formation of early stellar spheroids and quasars.
Cosmological MHD simulations of cluster formation with anisotropic thermal conduction
Ruszkowski, M; Bruggen, M; Parrish, I; Oh, S Peng
2010-01-01
(abridged) The ICM has been suggested to be buoyantly unstable in the presence of magnetic field and anisotropic thermal conduction. We perform first cosmological simulations of galaxy cluster formation that simultaneously include magnetic fields, radiative cooling and anisotropic thermal conduction. In isolated and idealized cluster models, the magnetothermal instability (MTI) tends to reorient the magnetic fields radially. Using cosmological simulations of the Santa Barbara cluster we detect radial bias in the velocity and magnetic fields. Such radial bias is consistent with either the inhomogeneous radial gas flows due to substructures or residual MTI-driven field rearangements that are expected even in the presence of turbulence. Although disentangling the two scenarios is challenging, we do not detect excess bias in the runs that include anisotropic thermal conduction. The anisotropy effect is potentially detectable via radio polarization measurements with LOFAR and SKA and future X-ray spectroscopic stu...
Westerveld, W J; Yousefi, M
2015-01-01
We present an accurate and fast 3D simulation scheme for out-of-plane grating couplers, based on two dimensional rigorous (finite difference time domain) grating simulations, the effective index method (EIM), and the Rayleigh-Sommerfeld diffraction formula. In comparison with full 3D FDTD simulations, the rms difference in electric field is below 5% and the difference in power flux is below 3%. A grating coupler for coupling from a silicon-on-insulator photonic integrated circuit to an optical fiber positioned 0.1 mm above the circuit is designed as example.
Software Development: 3D Animations and Creating User Interfaces for Realistic Simulations
Gordillo, Orlando Enrique
2015-01-01
My fall 2015 semester was spent at the Lyndon B. Johnson Space Center working in the Integrated Graphics, Operations, and Analysis Laboratory (IGOAL). My first project was to create a video animation that could tell the story of OMICS. OMICS is a term being used in the field of biomedical science to describe the collective technologies that study biological systems, such as what makes up a cell and how it functions with other systems. In the IGOAL I used a large 23 inch Wacom monitor to draw storyboards, graphics, and line art animations. I used Blender as the 3D environment to sculpt, shape, cut or modify the several scenes and models for the video. A challenge creating this video was to take a term used in biomedical science and describe it in such a way that an 8th grade student can understand. I used a line art style because it would visually set the tone for what we thought was an educational style. In order to get a handle on the perspective and overall feel for the animation without overloading my workspace, I split up the 2 minute animation into several scenes. I used Blender's python scripting capabilities which allowed for the addition of plugins to add or modify tools. The scripts can also directly interact with the objects to create naturalistic patterns or movements. After collecting the rendered scenes, I used Blender's built-in video editing workspace to output the animation. My second project was to write software that emulates a physical system's interface. The interface was to simulate a boat, ROV, and winch system. Simulations are a time and cost effective way to test complicated data and provide training for operators without having to use expensive hardware. We created the virtual controls with 3-D Blender models and 2-D graphics, and then add functionality in C# using the Unity game engine. The Unity engine provides several essential behaviors of a simulator, such as the start and update functions. A framework for Unity, which was developed in
Global MHD modeling of resonant ULF waves: Simulations with and without a plasmasphere.
Claudepierre, S G; Toffoletto, F R; Wiltberger, M
2016-01-01
We investigate the plasmaspheric influence on the resonant mode coupling of magnetospheric ultralow frequency (ULF) waves using the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamic (MHD) model. We present results from two different versions of the model, both driven by the same solar wind conditions: one version that contains a plasmasphere (the LFM coupled to the Rice Convection Model, where the Gallagher plasmasphere model is also included) and another that does not (the stand-alone LFM). We find that the inclusion of a cold, dense plasmasphere has a significant impact on the nature of the simulated ULF waves. For example, the inclusion of a plasmasphere leads to a deeper (more earthward) penetration of the compressional (azimuthal) electric field fluctuations, due to a shift in the location of the wave turning points. Consequently, the locations where the compressional electric field oscillations resonantly couple their energy into local toroidal mode field line resonances also shift earthward. We also find, in both simulations, that higher-frequency compressional (azimuthal) electric field oscillations penetrate deeper than lower frequency oscillations. In addition, the compressional wave mode structure in the simulations is consistent with a radial standing wave oscillation pattern, characteristic of a resonant waveguide. The incorporation of a plasmasphere into the LFM global MHD model represents an advance in the state of the art in regard to ULF wave modeling with such simulations. We offer a brief discussion of the implications for radiation belt modeling techniques that use the electric and magnetic field outputs from global MHD simulations to drive particle dynamics.
Global MHD modeling of resonant ULF waves: Simulations with and without a plasmasphere
Claudepierre, S. G.; Toffoletto, F. R.; Wiltberger, M.
2016-01-01
We investigate the plasmaspheric influence on the resonant mode coupling of magnetospheric ultralow frequency (ULF) waves using the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamic (MHD) model. We present results from two different versions of the model, both driven by the same solar wind conditions: one version that contains a plasmasphere (the LFM coupled to the Rice Convection Model, where the Gallagher plasmasphere model is also included) and another that does not (the stand-alone LFM). We find that the inclusion of a cold, dense plasmasphere has a significant impact on the nature of the simulated ULF waves. For example, the inclusion of a plasmasphere leads to a deeper (more earthward) penetration of the compressional (azimuthal) electric field fluctuations, due to a shift in the location of the wave turning points. Consequently, the locations where the compressional electric field oscillations resonantly couple their energy into local toroidal mode field line resonances also shift earthward. We also find, in both simulations, that higher-frequency compressional (azimuthal) electric field oscillations penetrate deeper than lower frequency oscillations. In addition, the compressional wave mode structure in the simulations is consistent with a radial standing wave oscillation pattern, characteristic of a resonant waveguide. The incorporation of a plasmasphere into the LFM global MHD model represents an advance in the state of the art in regard to ULF wave modeling with such simulations. We offer a brief discussion of the implications for radiation belt modeling techniques that use the electric and magnetic field outputs from global MHD simulations to drive particle dynamics.
Mandumpala Devassy, B.; Edelbauer, W.; Greif, D.
2015-12-01
Cavitation and its effect on spray formation and its dispersion play a crucial role in proper engine combustion and controlled emission. This study focuses on these effects in a typical common rail 6-hole diesel injector accounting for 3D needle movement and flow compressibility effects. Coupled numerical simulations using 1D and 3D CFD codes are used for this investigation. Previous studies in this direction have already presented a detailed structure of the adopted methodology. Compared to the previous analysis, the present study investigates the effect of 3D needle movement and cavitation on the spray formation for pilot and main injection events for a typical diesel engine operating point. The present setup performs a 3D compressible multiphase simulation coupled with a standalone 1D high pressure flow simulation. The simulation proceeds by the mutual communication between 1D and 3D solvers. In this work a typical common rail injector with a mini-sac nozzle is studied. The lateral and radial movement of the needle and its effect on the cavitation generation and the subsequent spray penetration are analyzed. The result indicates the effect of compressibility of the liquid on damping the needle forces, and also the difference in the spray penetration levels due to the asymmetrical flow field. Therefore, this work intends to provide an efficient and user-friendly engineering tool for simulating a complete fuel injector including spray propagation.
Constrained Transport vs. Divergence Cleanser Options in Astrophysical MHD Simulations
Lindner, Christopher C.; Fragile, P.
2009-01-01
In previous work, we presented results from global numerical simulations of the evolution of black hole accretion disks using the Cosmos++ GRMHD code. In those simulations we solved the magnetic induction equation using an advection-split form, which is known not to satisfy the divergence-free constraint. To minimize the build-up of divergence error, we used a hyperbolic cleanser function that simultaneously damped the error and propagated it off the grid. We have since found that this method produces qualitatively and quantitatively different behavior in high magnetic field regions than results published by other research groups, particularly in the evacuated funnels of black-hole accretion disks where Poynting-flux jets are reported to form. The main difference between our earlier work and that of our competitors is their use of constrained-transport schemes to preserve a divergence-free magnetic field. Therefore, to study these differences directly, we have implemented a constrained transport scheme into Cosmos++. Because Cosmos++ uses a zone-centered, finite-volume method, we can not use the traditional staggered-mesh constrained transport scheme of Evans & Hawley. Instead we must implement a more general scheme; we chose the Flux-CT scheme as described by Toth. Here we present comparisons of results using the divergence-cleanser and constrained transport options in Cosmos++.
Modeling and simulation of 3D thermal stresses of large-sized castings in solidification processes
Institute of Scientific and Technical Information of China (English)
无
2004-01-01
When heavy machines and large scaled receiver system of communication equipment are manufactured, it always needs to produce large- sized steel castings, aluminum castings and etc. Some defects of hot cracking by thermal stress often appear during solidification process as these castings are produced, which results in failure of castings.Therefore predicting the effects of technological parameters for production of castings on the thermal stress during solidification process becomes an important means. In this paper, the mathematical models have been established and numerical calculation of temperature fields by using finite difference method (FDM) and then thermal stress fields by using finite element method (FEM) during solidification process of castings have been carried out. The technological parameters of production have been optimized by the results of calculation and the defects of hot cracking have been eliminated. Modeling and simulation of 3D thermal stress during solidification processes of large-sized castings provided a scientific basis, which promoted further development of advanced manufacturing technique.
USM3D Simulations of Saturn V Plume Induced Flow Separation
Deere, Karen; Elmlilgui, Alaa; Abdol-Hamid, K. S.
2011-01-01
The NASA Constellation Program included the Ares V heavy lift cargo vehicle. During the design stage, engineers questioned if the Plume Induced Flow Separation (PIFS) that occurred along Saturn V rocket during moon missions at some flight conditions, would also plague the newly proposed rocket. Computational fluid dynamics (CFD) was offered as a tool for initiating the investigation of PIFS along the Ares V rocket. However, CFD best practice guidelines were not available for such an investigation. In an effort to establish a CFD process and define guidelines for Ares V powered simulations, the Saturn V vehicle was used because PIFS flight data existed. The ideal gas, computational flow solver USM3D was evaluated for its viability in computing PIFS along the Saturn V vehicle with F-1 engines firing. Solutions were computed at supersonic freestream conditions, zero degree angle of attack, zero degree sideslip, and at flight Reynolds numbers. The effects of solution sensitivity to grid refinement, turbulence models, and the engine boundary conditions on the predicted PIFS distance along the Saturn V were discussed and compared to flight data from the Apollo 11 mission AS-506.
3D numerical model of the Omega Nebula (M17): simulated thermal X-ray emission
Reyes-Iturbide, J; Rosado, M; Rodríguez-Gónzalez, A; González, R F; Esquivel, A
2009-01-01
We present 3D hydrodynamical simulations of the superbubble M17, also known as the Omega nebula, carried out with the adaptive grid code yguazu'-a, which includes radiative cooling. The superbubble is modelled considering the winds of 11 individual stars from the open cluster inside the nebula (NGC 6618), for which there are estimates of the mass loss rates and terminal velocities based on their spectral types. These stars are located inside a dense interstellar medium, and they are bounded by two dense molecular clouds. We carried out three numerical models of this scenario, considering different line of sight positions of the stars (the position in the plane of the sky is known, thus fixed). Synthetic thermal X-ray emission maps are calculated from the numerical models and compared with ROSAT observations of this astrophysical object. Our models reproduce successfully both the observed X-ray morphology and the total X-ray luminosity, without taking into account thermal conduction effects.
Surface-effect corrections for solar-like oscillations using 3D hydrodynamical simulations
Sonoi, T; Belkacem, K; Ludwig, H -G; Caffau, E; Mosser, B
2015-01-01
The space-borne missions have provided us with a wealth of high-quality observational data that allows for seismic inferences of stellar interiors. This requires the computation of precise and accurate theoretical frequencies, but imperfect modeling of the uppermost stellar layers introduces systematic errors. To overcome this problem, an empirical correction has been introduced by Kjeldsen et al. (2008, ApJ, 683, L175) and is now commonly used for seismic inferences. Nevertheless, we still lack a physical justification allowing for the quantification of the surface-effect corrections. We used a grid of these simulations computed with the CO$^5$BOLD code to model the outer layers of solar-like stars. Upper layers of the corresponding 1D standard models were then replaced by the layers obtained from the horizontally averaged 3D models. The frequency differences between these patched models and the 1D standard models were then calculated using the adiabatic approximation and allowed us to constrain the Kjeldsen...
3D numerical simulation of gaseous flows structure in semidetached binaries
Bisikalo, D V; Chechetkin, V M; Kuznetsov, O A; Molteni, D
1998-01-01
The results of 3D hydrodynamic simulation of mass transfer in semidetached binaries of different types (cataclysmic variables and low-mass X-ray binaries) are presented. We find that taking into account of a circumbinary envelope leads to significant changes in the stream-disc morphology. In particular, the obtained steady-state self-consistent solutions show an absence of impact between gas stream from the inner Lagrangian point L1 and forming accretion disc. The stream deviates under the action of gas of circumbinary envelope, and does not cause the shock perturbation of the disc boundary (traditional `hotspot'). At the same time, the gas of circumbinary envelope interacts with the stream and causes the formation of an extended shock wave, located on the stream edge. We discuss the implication of this model without `hotspot' (but with a shock wave located outside the disc) for interpretation of observations. The comparison of synthetic light curves with observations proves the validity of the discussed hydr...
Simulation study of a novel 3D SPAD pixel in an advanced FD-SOI technology
Vignetti, M. M.; Calmon, F.; Lesieur, P.; Savoy-Navarro, A.
2017-02-01
In this paper, a novel SPAD architecture implemented in a Fully-Depleted Silicon-On-Insulator (SOI) CMOS technology is presented. Thanks to its intrinsic vertical 3D structure, the proposed solution is expected to allow further scaling of the pixel size while ensuring high fill factors. Moreover the pixel and the detector electronics can benefit of the well-known advantages brought by SOI technology with respect to bulk CMOS, such as higher speed and lower power consumption. TCAD simulations based on realistic process parameters and dedicated post-processing analysis are carried out in order to optimize and validate the avalanche diode architecture for an optimal electric field distribution in the device but also to extract the main parameters of the SPAD, such as the breakdown voltage, the avalanche triggering probability, the dark count rate and the photon detection probability. A comparison between the efficiency in back-side and front-side approaches is carried out with a particular focus on time-of-flight applications.
Multi-ion, multi-fluid 3-D magnetohydrodynamic simulation of the outer heliosphere
Prested, Christina; Toth, Gabor
2012-01-01
Data from the Voyager probes and the Interstellar Boundary Explorer have revealed the importance of pick-up ions (PUIs) in understanding the character and behavior of the outer heliosphere, the region of interaction between the solar wind and the interstellar medium. In the outer heliosphere PUIs carry a large fraction of the thermal pressure, which effects the nature of the termination shock, and they are a dominate component of pressure in the heliosheath. This paper describes the development of a new multi-ion, multi-fluid 3-D magnetohydrodynamic model of the outer heliosphere. This model has the added capability of tracking the individual fluid properties of multiple ion populations. For this initial study two ion populations are modeled: the thermal solar wind ions and PUIs produced in the supersonic solar wind. The model also includes 4 neutral fluids that interact through charge-exchange with the ion fluids. The new multi-ion simulation reproduces the significant heating of PUIs at the termination shoc...
Numerical simulation on the evolution of cloud particles in 3-D convective cloud
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
A 3-D convective cloud model with compressible non-hydrostatic dynamics and the spectral bin microphysics of a 2-D slab-symmetric model has been used to simulate an observed supercell storm occurring on 29 June, 2000 near Bird City, Kansas, USA. The main objective of this paper is to study the evolution of particles in this convective storm with bin spectral microphysics scheme. Graupels form and grow through two mechanisms, deposition and riming, with the riming process dominant on top of the inflow and in the upper portion of main updraft. Over the outflow and during the developing and mature stages of the storm, graupel particles mainly grow through deposition with dominant unimodal spectra. Most fall out after growing up. Reducing initial relative humidity disturbance (increasing initial potential temperature disturbance) has negative impact on the formation and growth of graupels over the inflow (outflow). This study shows that large graupel and hail could be suppressed by altering the deposition and coalescence process over the inflow and main updraft. At different locations of the convective cells and with different initial humidity and potential temperature disturbance, the graupel formation and growth mechanisms are different, so as to the feasible hail suppression locations and methods.
Study of strength properties of ceramic composites with soft filler based on 3D computer simulation
Smolin, Alexey Yu.; Smolin, Igor Yu.; Smolina, Irina Yu.
2016-11-01
The movable cellular automaton method which is a computational method of particle mechanics is applied to simulating uniaxial compression of 3D specimens of a ceramic composite. Soft inclusions were considered explicitly by changing the sort (properties) of automata selected randomly from the original fcc packing. The distribution of inclusions in space, their size, and the total fraction were varied. For each value of inclusion fraction, there were generated several representative specimens with individual pore position in space. The resulting magnitudes of the elastic modulus and strength of the specimens were scattered and well described by the Weibull distribution. We showed that to reveal the dependence of the elastic and strength properties of the composite on the inclusion fraction it is much better to consider the mathematical expectation of the corresponding Weibull distribution, rather than the average of the values for the specimens of the same inclusion fraction. It is shown that the relation between the mechanical properties of material and its inclusion fraction depends significantly on the material structure. Namely, percolation transition from isolated inclusions to interconnected clusters of inclusions strongly manifests itself in the dependence of strength on the fraction of inclusions. Thus, the curve of strength versus inclusion fraction fits different equations for a different kind of structure.
3D finite element simulation of effects of deflection rate on energy absorption for TRIP steel
Directory of Open Access Journals (Sweden)
Hayashi Asuka
2015-01-01
Full Text Available Recently, with the requirement of lighter weight and more safety for a design of automobile, energy absorption capability of structural materials has become important. TRIP (Transformation-induced Plasticity steel is expected to apply to safety members because of excellent energy absorption capability and ductility. Past studies proved that such excellent characteristics in TRIP steel are dominated by strain-induced martensitic transformation (SIMT during plastic deformation. Because SIMT strongly depends on deformation rate and temperature, an investigation of the effects of deformation rate and temperature on energy absorption in TRIP is essential. Although energy absorption capability of material can be estimated by J-integral experimentally by using pre-cracked specimen, it is difficult to determine volume fraction of martensite and temperature rise during the crack extension. In addition, their effects on J-integral, especially at high deformation rate in experiment might be quite hard. Thus, a computational prediction needs to be performed. In this study, bending deformation behavior of pre-cracked specimen until the onset point of crack extension are predicted by 3D finite element simulation based on the transformation kinetics model proposed by Iwamoto et al. (1998. It is challenged to take effects of temperature, volume fraction of martensite and deformation rate into account. Then, the mechanism for higher energy absorption characteristic will be discussed.
In vitro bioactivity of 3D Ti-mesh with bioceramic coatings in simulated body fluid
Directory of Open Access Journals (Sweden)
Wei Yi
2014-09-01
Full Text Available 3D Ti-mesh has been coated with bioceramics under different coating conditions, such as material compositions and micro-porosity, using a dip casting method. Hydroxyapatite (HA, micro-HA particles (HAp, a bioglass (BG and their different mixtures together with polymer additives were used to control HA-coating microstructures. Layered composites with the following coating-to-substrate designs, such as BG/Ti, HA + BG/BG/Ti and HAp + BG/BG/Ti, were fabricated. The bioactivity of these coated composites and the uncoated Ti-mesh substrate was then investigated in a simulated body fluid (SBF. The Ti-mesh substrate and BG/Ti composite did not induce biomimetic apatite deposition when they were immersed in SBF for the selected BG, a pressable dental ceramic, used in this study. After seven days in SBF, an apatite layer was formed on both HA + BG/BG/Ti and HAp + BG/BG/Ti composites. The difference is the apatite layer on the HAp + BG/BG/Ti composite was rougher and contained more micro-pores, while the apatite layer on the HA + BG/BG/Ti composite was dense and smooth. The formation of biomimetic apatite, being more bioresorbable, is favored for bone regeneration.
STATICS ANALYSIS AND OPENGL BASED 3D SIMULATION OF COLLABORATIVE RECONFIGURABLE PLANETARY ROBOTS
Institute of Scientific and Technical Information of China (English)
Zhang Zheng; Ma Shugen; Li Bin; Zhang Liping; Cao Binggang
2006-01-01
Objective To study mechanics characteristics of two cooperative reconfigurable planetary robots when they get across an obstacle, and to find out the relationship between the maximum height of a stair with the configuration of the two-robot, and to find some restrictions of kinematics for the cooperation. Methods Multirobot cooperation theory is used in the whole study process. Inverse kinematics of the robot is used to form a desired configuration in the cooperation process. Static equations are established to analyze the relations between the friction factor, the configuration of robots and the maximum height of a stair. Kinematics analysis is used to find the restrictions of the two collaborative robots in position, velocity and acceleration. Results 3D simulation shows that the two cooperative robots can climb up a stair under the condition of a certain height and a certain friction factor between robot wheel and the surface of the stair. Following the restrictions of kinematics, the climbing mission is fulfilled successfully and smoothly. Conclusion The maximum height of a stair, which the two cooperative robots can climb up, is involved in the configuration of robots, friction factor between the stair and the robots. The most strict restriction of the friction factor does not appear in the horizontal position. In any case, the maximum height is smaller than half of the distance between the centroid of robot1 with the centroid of robot2. However, the height can be higher than the radius of one robot wheel, which profit from the collaboration.
Method of internal 3D flow field numerical simulation for hydrodynamic torque converter
Institute of Scientific and Technical Information of China (English)
Tao SHANG; Dingxuan ZHAO; Yuankun ZHANG; Xiangen GUO; Xiangzhong SHI
2008-01-01
To enhance the performance of a hydrody-namic torque converter and thoroughly understand the trait of inside flow, a numerical simulation method of internal 3D flow for the three-element centrifugal hydrodynamic torque converter was systematically researched and expatiated in this paper. First, the internal flow field of each impeller was calculated. The curves that illustrate the relationships between the pressure differences of the inlet and outlet versus flux were drawn. Second, the concurrent working point of each impeller was approximately estimated. Finally, a calculation was performed considering the influence on each impeller. The flow field of a working point was solved by multiple calculations and the actual working condition was gradually determined. The pressure and velocity distributions of the flow field were proposed. The performance parameters of the hydrodynamic torque converter were predicted. The calculation method, and the proposed pressure and velocity distribution of the flow field, have practical significance for the design and improvement of a hydrodynamic torque converter.
Linking 1D evolutionary to 3D hydrodynamical simulations of massive stars
Cristini, A.; Meakin, C.; Hirschi, R.; Arnett, D.; Georgy, C.; Viallet, M.
2016-03-01
Stellar evolution models of massive stars are important for many areas of astrophysics, for example nucleosynthesis yields, supernova progenitor models and understanding physics under extreme conditions. Turbulence occurs in stars primarily due to nuclear burning at different mass coordinates within the star. The understanding and correct treatment of turbulence and turbulent mixing at convective boundaries in stellar models has been studied for decades but still lacks a definitive solution. This paper presents initial results of a study on convective boundary mixing (CBM) in massive stars. The ‘stiffness’ of a convective boundary can be quantified using the bulk Richardson number ({{Ri}}{{B}}), the ratio of the potential energy for restoration of the boundary to the kinetic energy of turbulent eddies. A ‘stiff’ boundary ({{Ri}}{{B}}˜ {10}4) will suppress CBM, whereas in the opposite case a ‘soft’ boundary ({{Ri}}{{B}}˜ 10) will be more susceptible to CBM. One of the key results obtained so far is that lower convective boundaries (closer to the centre) of nuclear burning shells are ‘stiffer’ than the corresponding upper boundaries, implying limited CBM at lower shell boundaries. This is in agreement with 3D hydrodynamic simulations carried out by Meakin and Arnett (2007 Astrophys. J. 667 448-75). This result also has implications for new CBM prescriptions in massive stars as well as for nuclear burning flame front propagation in super-asymptotic giant branch stars and also the onset of novae.
Laser-Plasma Modeling Using PERSEUS Extended-MHD Simulation Code for HED Plasmas
Hamlin, Nathaniel; Seyler, Charles
2016-10-01
We discuss the use of the PERSEUS extended-MHD simulation code for high-energy-density (HED) plasmas in modeling laser-plasma interactions in relativistic and nonrelativistic regimes. By formulating the fluid equations as a relaxation system in which the current is semi-implicitly time-advanced using the Generalized Ohm's Law, PERSEUS enables modeling of two-fluid phenomena in dense plasmas without the need to resolve the smallest electron length and time scales. For relativistic and nonrelativistic laser-target interactions, we have validated a cycle-averaged absorption (CAA) laser driver model against the direct approach of driving the electromagnetic fields. The CAA model refers to driving the radiation energy and flux rather than the fields, and using hyperbolic radiative transport, coupled to the plasma equations via energy source terms, to model absorption and propagation of the radiation. CAA has the advantage of not requiring adequate grid resolution of each laser wavelength, so that the system can span many wavelengths without requiring prohibitive CPU time. For several laser-target problems, we compare existing MHD results to extended-MHD results generated using PERSEUS with the CAA model, and examine effects arising from Hall physics. This work is supported by the National Nuclear Security Administration stewardship sciences academic program under Department of Energy cooperative agreements DE-FOA-0001153 and DE-NA0001836.
Klimas, A. J.; Uritsky, V.; Vassiliadis, D.; Baker, D. N.
2005-01-01
Loading and consequent unloading of magnetic flux is an essential element of the substorm cycle in Earth's magnetotail. We are unaware of an available global MHD magnetospheric simulation model that includes a loading- unloading cycle in its behavior. Given the central role that MHD models presently play in the development of our understanding of magnetospheric dynamics, and given the present plans for the central role that these models will play in ongoing space weather prediction programs, it is clear that this failure must be corrected. A 2-dimensional numerical driven current-sheet model has been developed that incorporates an idealized current- driven instability with a resistive MHD system. Under steady loading, the model exhibits a global loading- unloading cycle. The specific mechanism for producing the loading-unloading cycle will be discussed. It will be shown that scale-free avalanching of electromagnetic energy through the model, from loading to unloading, is carried by repetitive bursts of localized reconnection. Each burst leads, somewhat later, to a field configuration that is capable of exciting a reconnection burst again. This process repeats itself in an intermittent manner while the total field energy in the system falls. At the end of an unloading interval, the total field energy is reduced to well below that necessary to initiate the next unloading event and, thus, a loading-unloading cycle results. It will be shown that, in this model, it is the topology of bursty localized reconnection that is responsible for the appearance of the loading-unloading cycle.
You’re Cut Off: HD and MHD Simulations of Truncated Accretion Disks
Hogg, J. Drew; Reynolds, Christopher S.
2017-01-01
Truncated accretion disks are commonly invoked to explain the spectro-temporal variability from accreting black holes in both small systems, i.e. state transitions in galactic black hole binaries (GBHBs), and large systems, i.e. low-luminosity active galactic nuclei (LLAGNs). In the canonical truncated disk model of moderately low accretion rate systems, gas in the inner region of the accretion disk occupies a hot, radiatively inefficient phase, which leads to a geometrically thick disk, while the gas in the outer region occupies a cooler, radiatively efficient phase that resides in the standard geometrically thin disk. Observationally, there is strong empirical evidence to support this phenomenological model, but a detailed understanding of the disk behavior is lacking. We present well-resolved hydrodynamic (HD) and magnetohydrodynamic (MHD) numerical models that use a toy cooling prescription to produce the first sustained truncated accretion disks. Using these simulations, we study the dynamics, angular momentum transport, and energetics of a truncated disk in the two different regimes. We compare the behaviors of the HD and MHD disks and emphasize the need to incorporate a full MHD treatment in any discussion of truncated accretion disk evolution.
A Resistive MHD Simulation of the Shear Flow Effects on the Structure of Reconnection Layer
Institute of Scientific and Technical Information of China (English)
SUN Xiaoxia; WANG Chunhua; LIN Yu; WANG Xiaogang
2007-01-01
By using a one-dimensional resistive magnetohydrodynamic (MHD) model, the Rie-mann problem is solved numerically for the structure of the reconnection layer under a sheared flow along the anti-parallel magnetic field components. The simulation is carried out for general cases with symmetric or asymmetric plasma densities and magnetic fields on the two sides of the initial current sheet, and cases with or without a guide magnetic field, as in various space and fusion plasmas. The generation of MHD discontinuities in the reconnection layer is discussed, including time-dependent intermediate shocks, intermediate shocks, slow shocks, slow expansion waves, and the contact discontinuity. It is shown that the structure of the reconnection layer is significantly affected by the presence of the shear flow. For an initial symmetric current sheet, the symmetry condition is altered due to the shear flow. For cases with an asymmetric initial current sheet, as at the Earth's magnetopause, the strengths of MHD discontinuities change significantly with the shear flow speed. Moreover, the general results for the reconnection layers in the outflow regions on either side of the X line are discussed systematically for the first time.
Yang, H.; Bhattacharjee, A.; Forbes, T. G.
2008-12-01
It has long been suggested that eruptive phenomena such as coronal mass ejections, prominence eruptions, and large flares might be caused by a loss of equilibrium in a coronal flux rope (Van Tend and Kuperus, 1978). Forbes et al. (1994) developed an analytical two-dimensional model in which eruptions occur due to a catastrophic loss of equilibrium and relaxation to a lower-energy state containing a thin current sheet. Magnetic reconnection then intervenes dynamically, leading to the release of magnetic energy and expulsion of a plasmoid. We have carried out high-Lundquist-number simulations to test the loss-of equilibrium mechanism, and demonstrated that it does indeed occur in the quasi-ideal limit. We have studied the subsequent dynamical evolution of the system in resistive and Hall MHD models for single as well as multiple arcades. The typical parallel electric fields are super-Dreicer, which makes it necessary to include collisionless effects via a generalized Ohm's law. It is shown that the nature of the local dissipation mechanism has a significant effect on the global geometry and dynamics of the magnetic configuration. The presence of Hall currents is shown to alter the length of the current sheet and the jets emerging from the reconnection site, directed towards the chromosphere. Furthermore, Hall MHD effects break certain symmetries of resistive MHD dynamics, and we explore their observational consequences.
Mapping of coma anisotropies to plasma structures of weak comets: a 3-D hybrid simulation study
Directory of Open Access Journals (Sweden)
N. Gortsas
2009-04-01
Full Text Available The effects of coma anisotropies on the plasma environment of comets have been studied by means of a 3-D hybrid model which treats electrons as a massless, charge-neutralizing fluid, whereas ion dynamics are covered by a kinetic approach. From Earth-based observations as well as from in-situ spacecraft measurements the shape of the coma of many comets is ascertained to be anisotropic. However, most plasma simulation studies deploy a spherically symmetric activity pattern. In this paper anisotropy is studied by considering three different coma shape models. The first model is derived from the Haser model and is characterised by spherically symmetry. This reference model is then compared with two different neutral gas shape models: the dayside restricted model with no nightside activity and a cone shaped model with opening angle of π/2. In all models the integrated surface activity is kept constant. The simulations have been done for the Rosetta target comet 67P/Churyumov-Gerasimenko for two heliocentric distances, 1.30 AU and 3.25 AU. It is found that shock formation processes are modified as a result of increasing spatial confinement. Characteristic plasma structures of comets such as the bow shock, magnetic barrier region and the ion composition boundary exhibit a shift towards the sun. In addition, the cone shaped model leads to a strong increase of the mass-loaded region which in turn leads to a smooth deceleration of the solar wind flow and an increasing degree of mixture between the solar wind and cometary ion species. This creates an additional transport channel of the magnetic field from the magnetic barrier region away which in turn leads to a broadening of this region. In addition, it leads to an ion composition boundary which is only gradually developed.
Energy Technology Data Exchange (ETDEWEB)
Duru, Kenneth, E-mail: kduru@stanford.edu [Department of Geophysics, Stanford University, Stanford, CA (United States); Dunham, Eric M. [Department of Geophysics, Stanford University, Stanford, CA (United States); Institute for Computational and Mathematical Engineering, Stanford University, Stanford, CA (United States)
2016-01-15
Dynamic propagation of shear ruptures on a frictional interface in an elastic solid is a useful idealization of natural earthquakes. The conditions relating discontinuities in particle velocities across fault zones and tractions acting on the fault are often expressed as nonlinear friction laws. The corresponding initial boundary value problems are both numerically and computationally challenging. In addition, seismic waves generated by earthquake ruptures must be propagated for many wavelengths away from the fault. Therefore, reliable and efficient numerical simulations require both provably stable and high order accurate numerical methods. We present a high order accurate finite difference method for: a) enforcing nonlinear friction laws, in a consistent and provably stable manner, suitable for efficient explicit time integration; b) dynamic propagation of earthquake ruptures along nonplanar faults; and c) accurate propagation of seismic waves in heterogeneous media with free surface topography. We solve the first order form of the 3D elastic wave equation on a boundary-conforming curvilinear mesh, in terms of particle velocities and stresses that are collocated in space and time, using summation-by-parts (SBP) finite difference operators in space. Boundary and interface conditions are imposed weakly using penalties. By deriving semi-discrete energy estimates analogous to the continuous energy estimates we prove numerical stability. The finite difference stencils used in this paper are sixth order accurate in the interior and third order accurate close to the boundaries. However, the method is applicable to any spatial operator with a diagonal norm satisfying the SBP property. Time stepping is performed with a 4th order accurate explicit low storage Runge–Kutta scheme, thus yielding a globally fourth order accurate method in both space and time. We show numerical simulations on band limited self-similar fractal faults revealing the complexity of rupture
Albedo and heat transport in 3-D model simulations of the early Archean climate
Directory of Open Access Journals (Sweden)
H. Kienert
2013-08-01
Full Text Available At the beginning of the Archean eon (ca. 3.8 billion years ago, the Earth's climate state was significantly different from today due to the lower solar luminosity, smaller continental fraction, higher rotation rate and, presumably, significantly larger greenhouse gas concentrations. All these aspects play a role in solutions to the "faint young Sun paradox" which must explain why the ocean surface was not fully frozen at that time. Here, we present 3-D model simulations of climate states that are consistent with early Archean boundary conditions and have different CO2 concentrations, aiming at an understanding of the fundamental characteristics of the early Archean climate system. In order to do so, we have appropriately modified an intermediate complexity climate model that couples a statistical-dynamical atmosphere model (involving parameterizations of the dynamics to an ocean general circulation model and a thermodynamic-dynamic sea-ice model. We focus on three states: one of them is ice-free, one has the same mean surface air temperature of 288 K as today's Earth and the third one is the coldest stable state in which there is still an area with liquid surface water (i.e. the critical state at the transition to a "snowball Earth". We find a reduction in meridional heat transport compared to today, which leads to a steeper latitudinal temperature profile and has atmospheric as well as oceanic contributions. Ocean surface velocities are largely zonal, and the strength of the atmospheric meridional circulation is significantly reduced in all three states. These aspects contribute to the observed relation between global mean temperature and albedo, which we suggest as a parameterization of the ice-albedo feedback for 1-D model simulations of the early Archean and thus the faint young Sun problem.
Jinya, John; Bipasha, Paul S.
2016-05-01
Clouds strongly modulate the Earths energy balance and its atmosphere through their interaction with the solar and terrestrial radiation. They interact with radiation in various ways like scattering, emission and absorption. By observing these changes in radiation at different wavelength, cloud properties can be estimated. Cloud properties are of utmost importance in studying different weather and climate phenomena. At present, no satellite provides cloud microphysical parameters over the Indian region with high temporal resolution. INSAT-3D imager observations in 6 spectral channels from geostationary platform offer opportunity to study continuous cloud properties over Indian region. Visible (0.65 μm) and shortwave-infrared (1.67 μm) channel radiances can be used to retrieve cloud microphysical parameters such as cloud optical thickness (COT) and cloud effective radius (CER). In this paper, we have carried out a feasibility study with the objective of cloud microphysics retrieval. For this, an inter-comparison of 15 globally available radiative transfer models (RTM) were carried out with the aim of generating a Look-up- Table (LUT). SBDART model was chosen for the simulations. The sensitivity of each spectral channel to different cloud properties was investigated. The inputs to the RT model were configured over our study region (50°S - 50°N and 20°E - 130°E) and a large number of simulations were carried out using random input vectors to generate the LUT. The determination of cloud optical thickness and cloud effective radius from spectral reflectance measurements constitutes the inverse problem and is typically solved by comparing the measured reflectances with entries in LUT and searching for the combination of COT and CER that gives the best fit. The products are available on the website www.mosdac.gov.in
Extragalactic jets with helical magnetic fields: relativistic MHD simulations
Keppens, R; van der Holst, B; Casse, F
2008-01-01
Extragalactic jets are inferred to harbor dynamically important, organized magnetic fields which presumably aid in the collimation of the relativistic jet flows. We here explore by means of grid-adaptive, high resolution numerical simulations the morphology of AGN jets pervaded by helical field and flow topologies. We concentrate on morphological features of the bow shock and the jet beam behind the Mach disk, for various jet Lorentz factors and magnetic field helicities. We investigate the influence of helical magnetic fields on jet beam propagation in overdense external medium. We use the AMRVAC code, employing a novel hybrid block-based AMR strategy, to compute ideal plasma dynamics in special relativity. The helicity of the beam magnetic field is effectively transported down the beam, with compression zones in between diagonal internal cross-shocks showing stronger toroidal field regions. In comparison with equivalent low-relativistic jets which get surrounded by cocoons with vortical backflows filled by ...
Numerical Simulations of Driven Supersonic Relativistic MHD Turbulence
Zrake, Jonathan; 10.1063/1.3621748
2011-01-01
Models for GRB outflows invoke turbulence in relativistically hot magnetized fluids. In order to investigate these conditions we have performed high-resolution three-dimensional numerical simulations of relativistic magneto-hydrodynamical (RMHD) turbulence. We find that magnetic energy is amplified to several percent of the total energy density by turbulent twisting and folding of magnetic field lines. Values of epsilon_B near 1% are thus naturally expected. We study the dependence of saturated magnetic field energy fraction as a function of Mach number and relativistic temperature. We then present power spectra of the turbulent kinetic and magnetic energies. We also present solenoidal (curl-like) and dilatational (divergence-like) power spectra of kinetic energy. We propose that relativistic effects introduce novel couplings between these spectral components. The case we explore in most detail is for equal amounts of thermal and rest mass energy, corresponding to conditions after collisions of shells with re...
MRI-driven Accretion onto Magnetized stars: Axisymmetric MHD Simulations
Romanova, Marina M; Koldoba, Alexander V; Lovelace, Richard V E
2011-01-01
We present the first results of a global axisymmetric simulation of accretion onto rotating magnetized stars from a turbulent, MRI-driven disk. The angular momentum is transported outward by the magnetic stress of the turbulent flow with a rate corresponding to a Shakura-Sunyaev viscosity parameter alpha\\approx 0.01-0.04. The result of the disk-magnetosphere interaction depends on the orientation of the poloidal field in the disk relative to that of the star at the disk-magnetosphere boundary. If fields have the same polarity, then the magnetic flux is accumulated at the boundary and blocks the accretion which leads to the accumulation of matter at the boundary. Subsequently, this matter accretes to the star in outburst before accumulating again. Hence, the cycling, `bursty' accretion is observed. If the disc and stellar fields have opposite polarity, then the field reconnection enhances the penetration of the disk matter towards the deeper field lines of the magnetosphere. However, the magnetic stress at the...
MHD Simulations of a Moving Subclump with Heat Conduction
Asai, N; Matsumoto, R; Asai, Naoki; Fukuda, Naoya; Matsumoto, Ryoji
2004-01-01
High resolution observations of cluster of galaxies by Chandra have revealed the existence of an X-ray emitting comet-like galaxy C153 in the core of cluster of galaxies A2125. The galaxy C153 moving fast in the cluster core has a distinct X-ray tail on one side, obviously due to ram pressure stripping, since the galaxy C153 crossed the central region of A2125. The X-ray emitting plasma in the tail is substantially cooler than the ambient plasma. We present results of two-dimensional magnetohydrodynamic simulations of the time evolution of a subclump like C153 moving in magnetized intergalactic matter. Anisotropic heat conduction is included. We found that the magnetic fields are essential for the existence of the cool X-ray tail, because in non-magnetized plasma the cooler subclump tail is heated up by isotropic heat conduction from the hot ambient plasma and does not form such a comet-like tail.
Heng, Kevin
2011-09-01
The atmospheres of hot Jupiters are three-dimensional, non-linear entities and understanding them requires the construction of a hierarchy of models of varying sophistication. Since previous work has either focused on the atmospheric dynamics or implemented multi-band radiative transfer, a reasonable approach is to combine the treatment of 3D dynamics with dual-band radiative transfer, where the assumption is that the stellar irradiation and re-emitted radiation from the exoplanet are at distinct wavelengths. I report on the successful implementation of such a setup and demonstrate how it can be used to compute self-consistent temperature-pressure profiles on both the day and night sides of a hot Jupiter, as well as zonal-wind profiles, circulation cell patterns and the angular/temporal offset of the hotspot from the substellar point. In particular, the hotspot offset should aid us in distinguishing between different types of hot Jupiter atmospheres. Together with N. Madhusudhan, we combine the dual-band simulation technique with the abundance/temperature retrieval method of Madhusudhan & Seager, by empirically constraining a range of values for the broad-band opacities which are consistent with the current observations. The advantage of our novel method is that the range of opacities used improves with time as the observations get better. The ability to thoroughly, efficiently and systematically explore the interplay between atmospheric dynamics, radiation and synthetic spectra is an important step forward, as it prepares us for the theoretical interpretation of exoplanetary spectra which will be obtained by future space-based missions such as JWST and EChO. I acknowledge generous support from the Zwicky Prize Fellowship and the Star and Planet Formation Group (PI: Michael Meyer) at ETH Zurich.
Wu, Chin-Chun; Liou, Kan; Wu, S. T.; Dryer, Murray; Plunkett, Simon
2016-03-01
We study an unusual solar energetic particle (SEP) event that was associated with the coronal mass ejection (CME) on March 15, 2013. Enhancements of the SEP fluxes were first detected by the ACE spacecraft at 14:00 UT, ˜7 hours after the onset of the CME (07:00 UT), and the SEP's peak intensities were recorded ˜36 hours after the onset of the CME. Our recent study showed that the CME-driven shock Mach number, based on a global three-dimensional (3-D) magnetohydrodynamic (MHD) simulation, is well correlated with the time-intensity of 10-30 MeV and 30-80 MeV protons. Here we focus on the radial dependence (r-α) of 4He (3.43-41.2 MeV/n) and O (7.30-89.8 MeV/n) energetic particles from ACE/SIS. It is found that the scaling factor (α) ranges between 2 and 4 for most of the energy channels. We also found that the correlation coefficients tend to increase with SEP energies.
Inertial Current Generators of Poynting Flux in MHD Simulations of Black Hole Ergospheres
Punsly, B
2005-01-01
This Letter investigates the physics that is responsible for creating the current system that supports the outgoing Poynting flux emanating from the ergosphere of a rotating black hole in the limit that the magnetic energy density greatly exceeds the plasma rest mass density (magnetically dominated limit). The underlying physics is derived from published three-dimensional simulations that obey the general relativistic equations of perfect magnetohydrodynamics (MHD). It is found that the majority of the Poynting flux emitted from the magnetically dominated regions of the ergosphere has a source associated with inertial effects outside of the event horizon.
Lipatov, A S; Paterson, W R; Sittler, E C; Hartle, R E; Simpson, D G
2012-01-01
The hybrid kinetic model supports comprehensive simulation of the interaction between different spatial and energetic elements of the Europa moon-magnetosphere system with respect a to variable upstream magnetic field and flux or density distributions of plasma and energetic ions, electrons, and neutral atoms. This capability is critical for improving the interpretation of the existing Europa flyby measurements from the Galileo Orbiter mission, and for planning flyby and orbital measurements (including the surface and atmospheric compositions) for future missions. The simulations are based on recent models of the atmosphere of Europa (Cassidy et al., 2007; Shematovich et al., 2005). In contrast to previous approaches with MHD simulations, the hybrid model allows us to fully take into account the finite gyroradius effect and electron pressure, and to correctly estimate the ion velocity distribution and the fluxes along the magnetic field (assuming an initial Maxwellian velocity distribution for upstream backgr...
Relativistic modeling capabilities in PERSEUS extended MHD simulation code for HED plasmas
Energy Technology Data Exchange (ETDEWEB)
Hamlin, Nathaniel D., E-mail: nh322@cornell.edu [438 Rhodes Hall, Cornell University, Ithaca, NY, 14853 (United States); Seyler, Charles E., E-mail: ces7@cornell.edu [Cornell University, Ithaca, NY, 14853 (United States)
2014-12-15
We discuss the incorporation of relativistic modeling capabilities into the PERSEUS extended MHD simulation code for high-energy-density (HED) plasmas, and present the latest hybrid X-pinch simulation results. The use of fully relativistic equations enables the model to remain self-consistent in simulations of such relativistic phenomena as X-pinches and laser-plasma interactions. By suitable formulation of the relativistic generalized Ohm’s law as an evolution equation, we have reduced the recovery of primitive variables, a major technical challenge in relativistic codes, to a straightforward algebraic computation. Our code recovers expected results in the non-relativistic limit, and reveals new physics in the modeling of electron beam acceleration following an X-pinch. Through the use of a relaxation scheme, relativistic PERSEUS is able to handle nine orders of magnitude in density variation, making it the first fluid code, to our knowledge, that can simulate relativistic HED plasmas.
Colangelo, Antonio C.
2010-05-01
each cell in synthetic slope systems performed by relief unity emulator. The central methodological strategy is to locate the potential rupture surfaces (prs), main material discontinuities, like soil-regolith or regolith-rock transitions. Inner these "prs", we would to outline the effective potential rupture surfaces (eprs). This surface is a sub-set of the "prs" that presents safety factor less than unity (fequilibrium be attained at residual shear strength. These devices generate graphic 3D cinematic sequences of experiments in synthetic slope systems and numerical results about physical and morphological data about scars and deposits. Thus, we have a detailed geotechnical, morphological, topographic and morphometric description of these mass movements prototypes, for deal with effective mass movements found in the real environments.
Kawasaki, Akira; Kubota, Kenichi; Funaki, Ikkoh; Okuno, Yoshihiro
2016-09-01
Steady-state and self-field magnetoplasmadynamic (MPD) thruster, which utilizes high-intensity direct-current (DC) discharge, is one of the prospective candidates of future high-power electric propulsion devices. In order to accurately assess the thrust performance and the electrode temperature, input electric power and wall heat flux must correctly be evaluated where electrostatic sheaths formed in close proximity of the electrodes affect these quantities. Conventional model simulates only plasma flows occurring in MPD thrusters with the absence of electrostatic sheath consideration. Therefore, this study extends the conventional model to a coupled magnetohydrodynamic (MHD) and thermal model by incorporating the phenomena relevant to the electrostatic sheaths. The sheaths are implemented as boundary condition of the MHD model on the walls. This model simulated the operation of the 100-kW-class thruster at discharge current ranging from 6 to 10 kA with argon propellant. The extended model reproduced the discharge voltages and wall heat load which are consistent with past experimental results. In addition, the simulation results indicated that cathode sheath voltages account for approximately 5-7 V subject to approximately 20 V of discharge voltages applied between the electrodes. This work was supported by JSPS KAKENHI Grant Numbers 26289328 and 15J10821.
Institute of Scientific and Technical Information of China (English)
XIE Hongqin; WU Zengmao; GAO Shanhong
2004-01-01
A series of test simulations are performed to evaluate the impact of satellite-derived meteorological data on numerical typhoon track prediction. Geostationary meteorological satellite (GMS-5) and NOAA's TIROS operational vertical sounder (TOVS) observations are used in the experiments. A three-dimensional variational (3D-Var) assimilation scheme is developed to assimilate the satellite data directly into the Penn State-NCAR nonhydrostatic meteorological model (MM5). Three-dimensional objective analysis fields based on the T213 results and conventional observations are employed as the background fields of the initialization. The comparisons of the simulated typhoon tracks are carried out, which correspond respectively to assimilate different kinds of satellite data. It is found that, compared with the experiment without satellite data assimilation, the 3D-Var assimilation schemes lead to significant improvements on typhoon track prediction. Track errors reduce from approximately 25% at 24 h to approximately 30% at 48 h for 3D-Var assimilation experiments.
Xie, Yifan; Wu, Jichun; Nan, Tongchao; Xue, Yuqun; Xie, Chunhong; Ji, Haifeng
2017-03-01
In this paper, an efficient triple-grid multiscale finite element method (ETMSFEM) is proposed for 3D groundwater simulation in heterogeneous porous media. The main idea of this method is to employ new 3D linear base functions and the domain decomposition technique to solve the local reduced elliptical problem, thereby simplifying the base function construction process and improving the efficiency. Furthermore, by using the ETMSFEM base functions, this method can solve Darcy's equation with high efficiency to obtain a continuous velocity field. Therefore, this method can considerably reduce the computational cost of solving for heads and velocities, which is crucial for large-scale 3D groundwater simulations. In the application section, we present numerical examples to compare the ETMSFEM with several classical methods to demonstrate its efficiency and effectiveness.
An Interactive 3D Graphics Modeler Based on Simulated Human Immune System
Directory of Open Access Journals (Sweden)
Hiroaki Nishino
2008-07-01
Full Text Available We propose an intuitive computer graphics authoring method based on interactive evolutionary computation (IEC. Our previous systems employed genetic algorithm (GA and mainly focused on rapid exploration of a single optimum 3D graphics model. The proposed method adopts a different computation strategy called immune algorithm (IA to ease the creation of varied 3D models even if a user doesn’t have any specific idea of final 3D products. Because artistic work like graphics design needs a process to diversify the user’s imagery, a tool that allows the user to select his/her preferred ones from a broad range of possible design solutions is particularly desired. IA enables the user to effectively explore a wealth of solutions in a huge 3D parametric space by using its essential mechanisms such as antibody formation and self-regulating function. We conducted an experiment to verify the effectiveness of the proposed method. The results show that the proposed method helps the user to easily generating wide variety of 3D graphics models.
Tay, W.B.; Van Oudheusden, B.W.; Bijl, H.
2013-01-01
The numerical simulation of a “X-wing” type biplane flapping wings, has been performed in 3D using the Immersed Boundary Method (IBM). This “X-wing” type flapping configuration draws its inspiration from Delfly [1], a family of ornithopters developed by the Delft University of Technology, as shown i
Simulated and Real Sheet-of-Light 3D Object Scanning Using a-Si:H Thin Film PSD Arrays
Directory of Open Access Journals (Sweden)
Javier Contreras
2015-11-01
Full Text Available A MATLAB/SIMULINK software simulation model (structure and component blocks has been constructed in order to view and analyze the potential of the PSD (Position Sensitive Detector array concept technology before it is further expanded or developed. This simulation allows changing most of its parameters, such as the number of elements in the PSD array, the direction of vision, the viewing/scanning angle, the object rotation, translation, sample/scan/simulation time, etc. In addition, results show for the first time the possibility of scanning an object in 3D when using an a-Si:H thin film 128 PSD array sensor and hardware/software system. Moreover, this sensor technology is able to perform these scans and render 3D objects at high speeds and high resolutions when using a sheet-of-light laser within a triangulation platform. As shown by the simulation, a substantial enhancement in 3D object profile image quality and realism can be achieved by increasing the number of elements of the PSD array sensor as well as by achieving an optimal position response from the sensor since clearly the definition of the 3D object profile depends on the correct and accurate position response of each detector as well as on the size of the PSD array.
Institute of Scientific and Technical Information of China (English)
LUO Jian; WANG Ying; LI Ainong; HUA Lin
2006-01-01
Using ABAQUS FEM software, the Elastic-plastic with isotropic hardening model is applied to simulate 3D cylinder slab rolling forming in continuous casting (CC), the change of liquid core before slab solidification completely on soft reduction process is studied, the analyse result shows the soft reduction technique can change the liquid core size, which is useful to cylinder slab forming in CC.
Institute of Scientific and Technical Information of China (English)
WANG Xi-fen; ZHOU Huai-chun
2005-01-01
The control of 3-D temperature distribution in a utility boiler furnace is essential for the safe, economic and clean operation of pcfired furnace with multi-burner system. The development of the visualization of 3-D temperature distributions in pc-fired furnaces makes it possible for a new combustion control strategy directly with the fumacs temperature as its goal to improve the control quality for the combustion processes. Studied in this paper is such a new strategy that the whole furnace is divided into several parts in the vertical direction, and the average temperature and its bias from the center in every cross section can be extracted from the visualization results of the 3-D temperature distributions. In the simulation stage, a computational fluid dynamics (CFD) code served to calculate the 3-D temperature distributions in a furnace, then a linear model was set up to relate the features of the temperature distributions with the input of the combustion processes, such as the flow rates of fuel and air fed into the furnaces through all the burners. The adaptive genetic algorithm was adopted to find the optimal combination of the whole input parameters which ensure to form an optimal 3-D temperature field in the furnace desired for the operation of boiler. Simulation results showed that the strategy could soon find the factors making the temperature distribution apart from the optimal state and give correct adjusting suggestions.
Small scale magnetosphere: Laboratory experiment, physical model and Hall MHD simulation
Shaikhislamov, I F; Zakharov, Yu P; Boyarintsev, E L; Melekhov, A V; Posukh, V G; Ponomarenko, A G
2011-01-01
A problem of magnetosphere formation on ion inertia scale around weakly magnetized bodies is investigated by means of laboratory experiment, analytical analysis and 2.5D Hall MHD simulation. Experimental evidence of specific magnetic field generated by the Hall term is presented. Direct comparison of regimes with small and large ion inertia length revealed striking differences in measured magnetopause position and plasma stand off distance. Analytical model is presented, which explains such basic features of mini-magnetosphere observed in previous kinetic simulations as disappearance of bow shock and plasma stopping at Stoermer particle limit instead of pressure balance distance. Numerical simulation is found to be in a good agreement with experiments and analytical model. It gives detailed spatial structure of Hall field and reveals that while ions penetrate deep inside mini-magnetosphere electrons overflow around it along magnetopause boundary.