A comparative study of Rayleigh-Taylor and Richtmyer-Meshkov instabilities in 2D and 3D in tantalum
Sternberger, Z.; Maddox, B. R.; Opachich, Y. P.; Wehrenberg, C. E.; Kraus, R. G.; Remington, B. A.; Randall, G. C.; Farrell, M.; Ravichandran, G.
2017-01-01
Driving a shock wave through the interface between two materials with different densities can result in the Richtmyer-Meshkov or Rayleigh-Taylor instability and initial perturbations at the interface will grow. If the shock wave is sufficiently strong, the instability will lead to plastic flow at the interface. Material strength will reduce the amount of plastic flow and suppress growth. While such instabilities have been investigated in 2D, no studies of this phenomena have been performed in 3D on materials with strength. Initial perturbations to seed the hydrodynamic instability were coined into tantalum recovery targets. Two types of perturbations were used, two dimensional (2D) perturbations (hill and valley) and three-dimensional (3D) perturbations (egg crate pattern). The targets were subjected to dynamic loading using the Janus laser at the Jupiter Laser Facility. Shock pressures ranged from 50 GPa up to 150 GPa and were calibrated using VISAR drive targets.
Fraschetti, Federico; Ballet, Jean; Decourchelle, Anne
2010-01-01
Context: The Rayleigh-Taylor instabilities generated by the deceleration of a supernova remnant during the ejecta-dominated phase are known to produce finger-like structures in the matter distribution which modify the geometry of the remnant. The morphology of supernova remnants is also expected to be modified when efficient particle acceleration occurs at their shocks. Aims: The impact of the Rayleigh-Taylor instabilities from the ejecta-dominated to the Sedov-Taylor phase is investigated over one octant of the supernova remnant. We also study the effect of efficient particle acceleration at the forward shock on the growth of the Rayleigh-Taylor instabilities. Methods: We modified the Adaptive Mesh Refinement code RAMSES to study with hydrodynamic numerical simulations the evolution of supernova remnants in the framework of an expanding reference frame. The adiabatic index of a relativistic gas between the forward shock and the contact discontinuity mimics the presence of accelerated particles. Results: The ...
Overview of Rayleigh-Taylor instability
Sharp, D.H.
1983-01-01
The aim of this talk is to survey Rayleigh-Taylor instability, describing the phenomenology that occurs at a Taylor unstable interface, and reviewing attempts to understand these phenomena quantitatively.
ALE simulation of Rayleigh-Taylor instability
Anbarlooei, H.R. [Univ. of Science and Technology, Dept. of Mechanical Engineering, Tehran (Iran, Islamic Republic of); Mazaheri, K. [Univ. of Tarbiyat Modares, Dept. of Mechanical Engineering, Tehran, (Iran, Islamic Republic of)]. E-mail: Kiumars@modares.ac.ir; Bidabadi, M. [Univ. of Science and Technology, Dept. of Mechanical Engineering, Tehran (Iran, Islamic Republic of)
2004-07-01
This paper investigates the use of an Arbitrary Lagrangian-Eulerian (ALE) technique for the simulation of a single mode Rayleigh-Taylor instability. A compatible Lagrangian algorithm is used on a simply connected quadrilateral grid in Lagrangian Phase. This algorithm includes subzonal pressures, which are used to control spurious grid motion, and an edge centered artificial viscosity. We use Reference Jacobians optimization based rezone algorithm in the rezoning phase of ALE method. Also a second order sign preserving method is used for remapping. To force monotonocity in remapping phase a Repair algorithm is used. Finally, for remapping of nodal variables we used a second order transformer to transfer these data to cell centers. It is shown that the usage of these algorithms for an ALE method can improve the simulation of a single mode Rayleigh-Taylor Instability. (author)
Kinetic Simulations of Rayleigh-Taylor Instabilities
Sagert, Irina; Colbry, Dirk; Howell, Jim; Staber, Alec; Strother, Terrance
2014-01-01
We report on an ongoing project to develop a large scale Direct Simulation Monte Carlo code. The code is primarily aimed towards applications in astrophysics such as simulations of core-collapse supernovae. It has been tested on shock wave phenomena in the continuum limit and for matter out of equilibrium. In the current work we focus on the study of fluid instabilities. Like shock waves these are routinely used as test-cases for hydrodynamic codes and are discussed to play an important role in the explosion mechanism of core-collapse supernovae. As a first test we study the evolution of a single-mode Rayleigh-Taylor instability at the interface of a light and a heavy fluid in the presence of a gravitational acceleration. To suppress small-wavelength instabilities caused by the irregularity in the separation layer we use a large particle mean free path. The latter leads to the development of a diffusion layer as particles propagate from one fluid into the other. For small amplitudes, when the instability is i...
Rayleigh-Taylor instability simulations with CRASH
Chou, C.-C.; Fryxell, B.; Drake, R. P.
2012-03-01
CRASH is a code package developed for the predictive study of radiative shocks. It is based on the BATSRUS MHD code used extensively for space-weather research. We desire to extend the applications of this code to the study of hydrodynamically unstable systems. We report here the results of Rayleigh-Taylor instability (RTI) simulations with CRASH, as a necessary step toward the study of such systems. Our goal, motivated by the previous comparison of simulations and experiment, is to be able to simulate the magnetic RTI with self-generated magnetic fields produced by the Biermann Battery effect. Here we show results for hydrodynamic RTI, comparing the effects of different solvers and numerical parameters. We find that the early-time behavior converges to the analytical result of the linear theory. We observe that the late-time morphology is sensitive to the numerical scheme and limiter beta. At low-resolution limit, the growth of RTI is highly dependent on the setup and resolution, which we attribute to the large numerical viscosity at low resolution.
Bates, J. W.; Schmitt, A. J.; Karasik, M.; Zalesak, S. T.
2016-12-01
The ablative Rayleigh-Taylor (RT) instability is a central issue in the performance of laser-accelerated inertial-confinement-fusion targets. Historically, the accurate numerical simulation of this instability has been a challenging task for many radiation hydrodynamics codes, particularly when it comes to capturing the ablatively stabilized region of the linear dispersion spectrum and modeling ab initio perturbations. Here, we present recent results from two-dimensional numerical simulations of the ablative RT instability in planar laser-ablated foils that were performed using the Eulerian code FastRad3D. Our study considers polystyrene, (cryogenic) deuterium-tritium, and beryllium target materials, quarter- and third-micron laser light, and low and high laser intensities. An initial single-mode surface perturbation is modeled in our simulations as a small modulation to the target mass density and the ablative RT growth-rate is calculated from the time history of areal-mass variations once the target reaches a steady-state acceleration. By performing a sequence of such simulations with different perturbation wavelengths, we generate a discrete dispersion spectrum for each of our examples and find that in all cases the linear RT growth-rate γ is well described by an expression of the form γ = α [ k g / ( 1 + ɛ k L m ) ] 1 / 2 - β k V a , where k is the perturbation wavenumber, g is the acceleration of the target, Lm is the minimum density scale-length, Va is the ablation velocity, and ɛ is either one or zero. The dimensionless coefficients α and β in the above formula depend on the particular target and laser parameters and are determined from two-dimensional simulation results through the use of a nonlinear curve-fitting procedure. While our findings are generally consistent with those of Betti et al. (Phys. Plasmas 5, 1446 (1998)), the ablative RT growth-rates predicted in this investigation are somewhat smaller than the values previously reported for the
Compressible, inviscid Rayleigh-Taylor instability
Guo, Yan
2009-01-01
We consider the Rayleigh-Taylor problem for two compressible, immiscible, inviscid, barotropic fluids evolving with a free interface in the presence of a uniform gravitational field. After constructing Rayleigh-Taylor steady-state solutions with a denser fluid lying above the free interface with the second fluid, we turn to an analysis of the equations obtained from linearizing around such a steady state. By a natural variational approach, we construct normal mode solutions that grow exponentially in time with rate like $e^{t \\sqrt{\\abs{\\xi}}}$, where $\\xi$ is the spatial frequency of the normal mode. A Fourier synthesis of these normal mode solutions allows us to construct solutions that grow arbitrarily quickly in the Sobolev space $H^k$, which leads to an ill-posedness result for the linearized problem. Using these pathological solutions, we then demonstrate ill-posedness for the original non-linear problem in an appropriate sense. More precisely, we use a contradiction argument to show that the non-linear...
Critical Magnetic Number in the MHD Rayleigh-Taylor instability
Wang, Yanjin
2010-01-01
We reformulate in Lagrangian coordinates the two-phase free boundary problem for the equations of Magnetohydrodynamics in a infinite slab, which is incompressible, viscous and of zero resistivity, as one for the Navier-Stokes equations with a force term induced by the fluid flow map. We study the stabilized effect of the magnetic field for the linearized equations around the steady-state solution by assuming that the upper fluid is heavier than the lower fluid, $i. e.$, the linear Rayleigh-Taylor instability. We identity the critical magnetic number $|B|_c$ by a variational problem. For the cases $(i)$ the magnetic number $\\bar{B}$ is vertical in 2D or 3D; $(ii)$ $\\bar{B}$ is horizontal in 2D, we prove that the linear system is stable when $|\\bar{B}|\\ge |B|_c$ and is unstable when $|\\bar{B}|<|B|_c$. Moreover, for $|\\bar{B}|<|B|_c$ the vertical $\\bar{B}$ stabilizes the low frequency interval while the horizontal $\\bar{B}$ stabilizes the high frequency interval, and the growth rate of growing modes is bou...
Dynamic stabilization of Rayleigh-Taylor instability in ablation fronts
Piriz A.R.
2013-11-01
Full Text Available Dynamic stabilization of Rayleigh-Taylor instability in an ablation front is studied by considering the simplest possible modulations in the acceleration. Explicit analytical expressions for the instability growth rate and for the boundaries of the stability region are obtained by considering a sequence of Dirac deltas. Besides, general square waves allow for studying the effect of the driving asymmetries on the stability region as well as the optimization process. The essential role of compressibility is phenomenologically addressed in order to find the constraints it imposes on the stability region.
Theoretical and Experimental Studies of Magneto-Rayleigh-Taylor Instabilities
Lau, Yue Ying [University of Michigan, Ann Arbor, MI (United States); Gilgenbach, Ronald [University of Michigan, Ann Arbor, MI (United States)
2013-07-07
Magneto-Rayleigh-Taylor instability (MRT) is important to magnetized target fusion, wire-array z-pinches, and equation-of-state studies using flyer plates or isentropic compression. It is also important to the study of the crab nebula. The investigators performed MRT experiments on thin foils, driven by the mega-ampere linear transformer driver (LTD) facility completed in their laboratory. This is the first 1-MA LTD in the USA. Initial experiments on the seeding of MRT were performed. Also completed was an analytic study of MRT for a finite plasma slab with arbitrary magnetic fields tangential to the interfaces. The effects of magnetic shear and feedthrough were analyzed.
Rayleigh-Taylor instability in accelerated solid media
Piriz, A. R.; Sun, Y. B.; Tahir, N. A.
2017-01-01
A linear study of the Rayleigh-Taylor instability based on momentum conservation and the consideration of an irrotational velocity field for incompressible perturbations is discussed. The theory allows for a very appealing physical picture and for a relatively simple description of the main features of the instability. As a result, it is suitable for the study of the very complex problem of the instability of accelerated solids with non-linear elastic-plastic constitutive properties, which cannot be studied by the usual normal modes approach. The elastic to plastic transition occurring early in the instability process determines the entire evolution and makes the instability exhibit behavior that cannot be captured by an asymptotic analysis.
Experimental study of 3D Rayleigh-Taylor convection between miscible fluids in a porous medium
Nakanishi, Yuji; Hyodo, Akimitsu; Wang, Lei; Suekane, Tetsuya
2016-11-01
The natural convection of miscible fluids in porous media has applications in several fields, such as geoscience and geoengineering, and can be employed for the geological storage of CO2. In this study, we used X-ray computer tomography to visualize 3D fingering structures associated with the Rayleigh-Taylor instability between miscible fluids in a porous medium. In the early stages of the onset of the Rayleigh-Taylor instability, a fine crinkling pattern gradually appeared at the interface. As the wavelength and amplitude increased, descending fingers formed on the interface and extended vertically downward; in addition, ascending and highly symmetric fingers formed. The adjacent fingers were cylindrical in shape and coalesced to form large fingers. The fingers appearing on the interface tended to become finer with increasing Rayleigh number, which is consistent with linear perturbation theory. When the Péclet number exceeded 10, transverse dispersion increased the finger diameter and enhanced the finger coalescence, strongly impacting the decrease in finger number density. When mechanical dispersion was negligible, the finger-extension velocity and the dimensionless mass-transfer rate scaled with the characteristic velocity and the Rayleigh number with an appropriate length scale. Mechanical dispersion not only reduced the onset time but also enhanced the mass transport.
Plasma transport driven by the Rayleigh-Taylor instability
Ma, X.; Delamere, P. A.; Otto, A.
2016-06-01
Two important differences between the giant magnetospheres (i.e., Jupiter's and Saturn's magnetospheres) and the terrestrial magnetosphere are the internal plasma sources and the fast planetary rotation. Thus, there must be a radially outward flow to transport the plasma to avoid infinite accumulation of plasma. This radial outflow also carries the magnetic flux away from the inner magnetosphere due to the frozen-in condition. As such, there also must be a radial inward flow to refill the magnetic flux in the inner magnetosphere. Due to the similarity between Rayleigh-Taylor (RT) instability and the centrifugal instability, we use a three-dimensional RT instability to demonstrate that an interchange instability can form a convection flow pattern, locally twisting the magnetic flux, consequently forming a pair of high-latitude reconnection sites. This process exchanges a part of the flux tube, thereby transporting the plasma radially outward without requiring significant latitudinal convection of magnetic flux in the ionosphere.
Rayleigh-Taylor instability of viscous fluids with phase change
Kim, Byoung Jae; Kim, Kyung Doo
2016-04-01
Film boiling on a horizontal surface is a typical example of the Rayleigh-Taylor instability. During the film boiling, phase changes take place at the interface, and thus heat and mass transfer must be taken into consideration in the stability analysis. Moreover, since the vapor layer is not quite thick, a viscous flow must be analyzed. Existing studies assumed equal kinematic viscosities of two fluids, and/or considered thin viscous fluids. The purpose of this study is to derive the analytical dispersion relation of the Rayleigh-Taylor instability for more general conditions. The two fluids have different properties. The thickness of the vapor layer is finite, but the liquid layer is thick enough to be nearly semi-infinite in view of perturbation. Initially, the vapor is in equilibrium with the liquid at the interface, and the direction of heat transfer is from the vapor side to the liquid side. In this case, the phase change has a stabilizing effect on the growth rate of the interface. When the vapor layer is thin, there is a coupled effect of the vapor viscosity, phase change, and vapor thickness on the critical wave number. For the other limit of a thick vapor, both the liquid and vapor viscosities influence the critical wave number. Finally, the most unstable wavelength is investigated. When the vapor layer is thin, the most unstable wavelength is not affected by phase change. When the vapor layer is thick, however, it increases with the increasing rate of phase change.
Experimental Study of Rayleigh-Taylor Instability Using Paramagnetic Fluids
Tsiklashvili, Vladimer; Likhachev, Oleg; Jacobs, Jeffry
2009-11-01
Experiments that take advantage of the properties of paramagnetic liquids are used to study Rayleigh-Taylor instability. A gravitationally unstable combination of a paramagnetic salt solution and a nonmagnetic solution is initially stabilized by a magnetic field gradient that is produced by the contoured pole-caps of a large electromagnet. Rayleigh-Taylor instability originates with the rapid removal of current from the electromagnet, which results in the heavy liquid falling into the light liquid due to gravity and, thus, mixing with it. The mixing zone is visualized by back-lit photography and is recorded with a digital video camera. For visualization purposes, a blue-green dye is added to the magnetic fluid. The mixing rate of the two liquids is determined from an averaged dye concentration across the mixing layer by means of the Beer-Lambert law. After removal of the suspending magnetic field, the initially flat interface between the two liquids develops a random surface pattern with the dominant length scale well approximated by the fastest growing wavelength in accordance with the viscous linear stability theory. Several combinations of paramagnetic and nonmagnetic solutions have been considered during the course of the research. A functional dependence of the mixing layer growth constant, α, on the properties of the liquids is a primary subject of the present study.
The magnetic Rayleigh-Taylor instability in astrophysical discs
Contopoulos, I.; Kazanas, D.; Papadopoulos, D. B.
2016-10-01
This is our first study of the magnetic Rayleigh-Taylor instability at the inner edge of an astrophysical disc around a central back hole. We derive the equations governing small-amplitude oscillations in general relativistic ideal magnetodydrodynamics and obtain a criterion for the onset of the instability. We suggest that static disc configurations where magnetic field is held by the disc material are unstable around a Schwarzschild black hole. On the other hand, we find that such configurations are stabilized by the space-time rotation around a Kerr black hole. We obtain a crude estimate of the maximum amount of poloidal magnetic flux that can be accumulated around the centre, and suggest that it is proportional to the black hole spin. Finally, we discuss the astrophysical implications of our result for the theoretical and observational estimations of the black hole jet power.
HUANG Lin; JIAN Guang-de; QIU Xiao-ming
2007-01-01
The synergistic stabilizing effect of gyroviscosity and sheared axial flow on the Rayleigh-Taylor instability in Z-pinch implosions is studied by means of the incompressible viscid magneto-hydrodynamic equations. The gyroviscosity (or finite Larmor radius) effects are introduced in the momentum equation through an anisotropic ion stress tensor. Dispersion relation with the effect of a density discontinuity is derived. The results indicate that the short-wavelength modes of the Rayleigh-Taylor instability are easily stabilized by the gyroviscosity effects. The long wavelength modes are stabilized by the sufficient sheared axial flow. However, the synergistic effects of the finite Larmor radius and sheared axial flow can heavily mitigate the Rayleigh-Taylor instability. This synergistic effect can compress the Rayleigh-Taylor instability to a narrow wave number region. Even with a sufficient gyroviscosity and large enough flow velocity, the synergistic effect can completely suppressed the Rayleigh-Taylor instability in whole wave number region.
Non-stationary Rayleigh-Taylor instability in supernovae ejecta
Ribeyre, X; Tikhonchuk, V T; Bouquet, S; Sanz, J; Ribeyre, Xavier; Hallo, Ludovic; Tikhonchuk, Vladimir; Bouquet, Serge; Sanz, Javier
2005-01-01
The Rayleigh-Taylor instability plays an important role in the dynamics of several astronomical objects, in particular, in supernovae (SN) evolution. In this paper we develop an analytical approach to study the stability analysis of spherical expansion of the SN ejecta by using a special transformation in the co-moving coordinate frame. We first study a non-stationary spherical expansion of a gas shell under the pressure of a central source. Then we analyze its stability with respect to a no radial, non spherically symmetric perturbation of the of the shell. We consider the case where the polytropic constant of the SN shell is $\\gamma=5/3$ and we examine the evolution of a arbitrary shell perturbation. The dispersion relation is derived. The growth rate of the perturbation is found and its temporal and spatial evolution is discussed. The stability domain depends on the ejecta shell thickness, its acceleration, and the perturbation wavelength.
Rayleigh-Taylor instability in partially ionized prominence plasma
Khomenko, E; de Vicente, A; Collados, M; Luna, M
2013-01-01
We study Rayleigh-Taylor instability (RTI) at the coronal-prominence boundary by means of 2.5D numerical simulations in a single-fluid MHD approach including a generalized Ohm's law. The initial configuration includes a homogeneous magnetic field forming an angle with the direction in which the plasma is perturbed. For each field inclination we compare two simulations, one for the pure MHD case, and one including the ambipolar diffusion in the Ohm's law, otherwise identical. We find that the configuration containing neutral atoms is always unstable. The growth rate of the small-scale modes in the non-linear regime is larger than in the purely MHD case.
The cylindrical magnetic Rayleigh-Taylor instability for viscous fluids
Chambers, K.; Forbes, L. K. [School of Mathematics and Physics, University of Tasmania, Private Bag 37-Hobart, Tasmania 7005 (Australia)
2012-10-15
This paper considers a cylindrical Rayleigh-Taylor instability, in which a heavy fluid surrounds a light fluid, and gravity is directed radially inwards. A massive object is located at the centre of the light fluid, and it behaves like a line dipole both for fluid flow and magnetic field strength. The initially circular interface between the two conducting fluids evolves into plumes, dependent on the magnetic and fluid dipole strengths and the nature of the initial disturbance to the interface. A spectral method is presented to solve the time-dependent interface shapes, and results are presented and discussed. Bipolar solutions are possible, and these are of particular relevance to astrophysics. The solutions obtained resemble structures of some HII regions and nebulae.
Rayleigh-Taylor Instability in a Relativistic Fireball on a Moving Computational Grid
Duffell, Paul C
2013-01-01
We numerically calculate the growth and saturation of the Rayleigh-Taylor instability caused by the deceleration of relativistic outflows with Lorentz factor \\Gamma = 10, 30, and 100. The instability generates turbulence whose scale exhibits strong dependence on Lorentz factor, as only modes within the causality scale \\Delta \\theta ~ 1/\\Gamma can grow. We develop a simple diagnostic to measure the fraction of energy in turbulent eddies and use it to estimate magnetic field amplification by the instability. We estimate a magnetic energy fraction ~ 0.01 due to Rayleigh-Taylor turbulence in a shock-heated region behind the forward shock. The instability completely disrupts the contact discontinuity between the ejecta and the swept up circumburst medium. The reverse shock is stable, but is impacted by the Rayleigh-Taylor instability, which strengthens the reverse shock and pushes it away from the forward shock. The forward shock front is unaffected by the instability, but Rayleigh-Taylor fingers can penetrate abo...
The role of Rayleigh-Taylor instabilities in filament threads
Terradas, J; Ballester, J L
2012-01-01
Many solar filaments and prominences show short-lived horizontal threads lying parallel to the photosphere. In this work the possible link between Rayleigh-Taylor instabilities and thread lifetimes is investigated. This is done by calculating the eigenmodes of a thread modelled as a Cartesian slab under the presence of gravity. An analytical dispersion relation is derived using the incompressible assumption for the magnetohydrodynamic (MHD) perturbations. The system allows a mode that is always stable, independently of the value of the Alfv\\'en speed in the thread. The character of this mode varies from being localised at the upper interface of the slab when the magnetic field is weak, to having a global nature and resembling the transverse kink mode when the magnetic field is strong. On the contrary, the slab model permits another mode that is unstable and localised at the lower interface when the magnetic field is weak. The growth rates of this mode can be very short, of the order of minutes for typical thr...
Magneto-Rayleigh-Taylor instability in solid media
Sun, Y. B. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); School of Physical Science and Technology, Lanzhou University, Lanzhou 73000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Piriz, A. R., E-mail: roberto.piriz@uclm.es [E.T.S.I. Industriales (Spain); CYTEMA (Spain); Instituto de Investigaciones Energéticas, Universidad de Castilla-La Mancha, 13071 Ciudad Real (Spain)
2014-07-15
A linear analysis of the magneto-Rayleigh-Taylor instability at the interface between a Newtonian fluid and an elastic-plastic solid is performed by considering a uniform magnetic B{sup →}, parallel to the interface, which has diffused into the fluid but not into the solid. It is found that the magnetic field attributes elastic properties to the viscous fluid which enhance the stability region by stabilizing all the perturbation wavelengths shorter than λ{sub 0}∝B{sup 2} for any initial perturbation amplitude. Longer wavelengths are stabilized by the mechanical properties of the solid provided that the initial perturbation wavelength is smaller than a threshold value determined by the yield strength and the shear modulus of the solid. Beyond this threshold, the amplitude grows initially with a growth rate reduced by the solid strength properties. However, such properties do not affect the asymptotic growth rate which is only determined by the magnetic field and the fluid viscosity. The described physical situation intends to resemble some of the features present in recent experiments involving the magnetic shockless acceleration of flyers plates.
Cylindrical Effects on Magneto-Rayleigh-Taylor Instability
Weis, Matthew; Lau, Yue Ying; Gilgenbach, Ronald; Jennings, Christopher; Hess, Mark
2012-10-01
This paper concentrates on the effects of cylindrical geometry on the magneto-Rayleigh-Taylor instability (MRT), a major concern in the magnetized liner inertial fusion concept (MagLIF) [1]. Several issues are being studied, such as the Bell-Plesset effect [2], the effects of magnetic shear and feedthrough [3], and the nonzero MRT growth rate that remains (but was hardly noticed) in the k = m = 0 limit in Harris' seminal paper on a cylindrical liner [4], where k and m are respectively the azimuthal and axial wavenumber. We shall use simulation and direct integration of the eigenvalue equation to investigate the importance of the cylindrical geometry, which is particularly relevant in the final stage of compression in the MagLIF concept. [4pt] [1] S. A. Slutz, et. al, Phys. Plasmas 17, 056303 (2010). [0pt] [2] G. I. Bell, Los Alamos Scientific Laboratory, Report LA-1321 (1951); M. S. Plesset, J. Appl. Phys. 25, 96 (1954).[0pt] [3] P. Zhang et al., Phys. Plasmas 19, 200703 (2012); Y. Y. Lau et al., Phys. Rev. E 83, 006405 (2011). [0pt] [4] E. G. Harris, Phys. Fluids 5, 1057 (1962).
Linear Rayleigh-Taylor instability for viscous, compressible fluids
Guo, Yan
2009-01-01
We study the equations obtained from linearizing the compressible Navier-Stokes equations around a steady-state profile with a heavier fluid lying above a lighter fluid along a planar interface, i.e. a Rayleigh-Taylor instability. We consider the equations with or without surface tension, with the viscosity allowed to depend on the density, and in both periodic and non-periodic settings. In the presence of viscosity there is no natural variational framework for constructing growing mode solutions to the linearized problem. We develop a general method of studying a family of modified variational problems in order to produce maximal growing modes. Using these growing modes, we construct smooth (when restricted to each fluid domain) solutions to the linear equations that grow exponentially in time in Sobolev spaces. We then prove an estimate for arbitrary solutions to the linearized equations in terms of the fastest possible growth rate for the growing modes. In the periodic setting, we show that sufficiently sm...
DSMC Simulations of the Rayleigh-Taylor Instability in Gases
Gallis, Michael; Koehler, Timothy; Torczynski, John; Plimpton, Steven
2015-11-01
The Direct Simulation Monte Carlo (DSMC) method of molecular gas dynamics is applied to simulate the Rayleigh-Taylor instability (RTI) in atmospheric-pressure monatomic gases (e.g., argon and helium). The computational domain is a 1 mm × 4 mm rectangle divided into 50-nm square cells. Each cell is populated with 1000 computational molecules, and time steps of 0.1 ns are used. Simulations are performed to quantify the growth of a single-mode perturbation on the interface as a function of the Atwood number and the gravitational acceleration. The DSMC results qualitatively reproduce all observed features of the RTI and are in reasonable quantitative agreement with existing theoretical and empirical models. Consistent with previous work in this field, the DSMC simulations indicate that the growth of the RTI follows a universal behavior. For cases with multiple-mode perturbations, the numbers of bubble-spike pairs that eventually appear are found to be in agreement with theoretical results for the most unstable wavelength. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
Direct Numerical Simulation of the Rayleigh-Taylor Instability with the Spectral Element Method
ZHANG Xu; TAN Duo-Wang
2009-01-01
A novel method is proposed to simulate Rayleigh-Taylor instabilities using a specially-developed unsteady threedimensional high-order spectral element method code.The numerical model used consists of Navier-Stokes equations and a transport-diffusive equation.The code is first validated with the results of linear stability perturbation theory.Then several characteristics of the Rayleigh-Taylor instabjJjties are studied using this three-dimensional unsteady code,inducling instantaneous turbulent structures and statistical turbulent mixing heights under different initial wave numbers.These results indicate that turbulent structures ofRayleigh-Taylor instabilities are strongly dependent on the initial conditions.The results also suggest that a high-order numerical method should provide the capability of sir.ulating small scale fluctuations of Rayleigh-Taylor instabilities of turbulent flows.
Non-equilibrium Thermodynamics of Rayleigh-Taylor instability
Sengupta, Tapan K.; Sengupta, Aditi; Shruti, K. S.; Sengupta, Soumyo; Bhole, Ashish
2016-10-01
Rayleigh-Taylor instability (RTI) has been studied here as a non-equilibrium thermodynamics problem. Air masses with temperature difference of 70K, initially with heavier air resting on lighter air isolated by a partition, are allowed to mix by impulsively removing the partition. This results in interface instabilities, which are traced here by solving two dimensional (2D) compressible Navier-Stokes equation (NSE), without using Boussinesq approximation (BA henceforth). The non-periodic isolated system is studied by solving NSE by high accuracy, dispersion relation preserving (DRP) numerical methods described in Sengupta T.K.: High Accuracy Computing Method (Camb. Univ. Press, USA, 2013). The instability onset is due to misaligned pressure and density gradients and is evident via creation and evolution of spikes and bubbles (when lighter fluid penetrates heavier fluid and vice versa, associated with pressure waves). Assumptions inherent in compressible formulation are: (i) Stokes' hypothesis that uses zero bulk viscosity assumption and (ii) the equation of state for perfect gas which is a consequence of equilibrium thermodynamics. Present computations for a non-equilibrium thermodynamic process do not show monotonic rise of entropy with time, as one expects from equilibrium thermodynamics. This is investigated with respect to the thought-experiment. First, we replace Stokes' hypothesis, with another approach where non-zero bulk viscosity of air is taken from an experiment. Entropy of the isolated system is traced, with and without the use of Stokes' hypothesis. Without Stokes' hypothesis, one notes the rate of increase in entropy to be higher as compared to results with Stokes' hypothesis. We show this using the total entropy production for the thermodynamically isolated system. The entropy increase from the zero datum is due to mixing in general; punctuated by fluctuating entropy due to creation of compression and rarefaction fronts originating at the interface
Three-Dimensional Single-Mode Nonlinear Ablative Rayleigh-Taylor Instability
Yan, R.; Betti, R.; Sanz, J.; Liu, B.; Frank, A.
2015-11-01
The nonlinear evolution of the ablative Rayleigh-Taylor (ART) instability is studied in three dimensions for conditions relevant to inertial confinement fusion targets. The simulations are performed using our newly developed code ART3D and an astrophysical code AstroBEAR. The laser ablation can suppress the growth of the short-wavelength modes in the linear phase but may enhance their growth in the nonlinear phase because of the vortex-acceleration mechanism. As the mode wavelength approaches the cutoff of the linear spectrum (short-wavelength modes), it is found that the bubble velocity grows faster than predicted in the classical 3-D theory. When compared to 2-D results, 3-D short-wavelength bubbles grow faster and do not reach saturation. The unbounded 3-D bubble acceleration is driven by the unbounded accumulation of vorticity inside the bubble. The vorticity is transferred by mass ablation from the Rayleigh-Taylor spikes into the ablated plasma filling the bubble volume. A density plateau is observed inside a nonlinear ART bubble and the plateau density is higher for shorter-wavelength modes. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.
Kulkarni, Akshay K
2008-01-01
We present results of 3D simulations of MHD instabilities at the accretion disk-magnetosphere boundary. The instability is Rayleigh-Taylor, and develops for a fairly broad range of accretion rates and stellar rotation rates and magnetic fields. It manifests itself in the form of tall, thin tongues of plasma that penetrate the magnetosphere in the equatorial plane. The shape and number of the tongues changes with time on the inner-disk dynamical timescale. In contrast with funnel flows, which deposit matter mainly in the polar region, the tongues deposit matter much closer to the stellar equator. The instability appears for relatively small misalignment angles, $\\Theta\\lesssim30^\\circ$, between the star's rotation and magnetic axes, and is associated with higher accretion rates. The hot spots and light curves during accretion through instability are generally much more chaotic than during stable accretion. The unstable state of accretion has possible implications for quasi-periodic oscillations and intermitten...
Large eddy simulation of Rayleigh-Taylor instability using the arbitrary Lagrangian-Eulerian method
Darlington, R
1999-12-01
This research addresses the application of a large eddy simulation (LES) to Arbitrary Lagrangian Eulerian (ALE) simulations of Rayleigh-Taylor instability. First, ALE simulations of simplified Rayleigh-Taylor instability are studied. The advantages of ALE over Eulerian simulations are shown. Next, the behavior of the LES is examined in a more complicated ALE simulation of Rayleigh-Taylor instability. The effects of eddy viscosity and stochastic backscatter are examined. The LES is also coupled with ALE to increase grid resolution in areas where it is needed. Finally, the methods studied above are applied to two sets of experimental simulations. In these simulations, ALE allows the mesh to follow expanding experimental targets, while LES can be used to mimic the effect of unresolved instability modes.
Large-eddy-simulation of 3-dimensional Rayleigh-Taylor instability in incompressible fluids
WANG; Lili
2002-01-01
［1］Sharp, D. H., An overview of Rayleigh-Taylor instability, Physica D, 1984, 12: 3-18.［2］Baker, G. R., Meiron, D. I., Orszag, S. A., Vortex simulation of the Rayleigh-Taylor instability, Phys. Fluids, 1980, 23: 1485-1490.［3］Tryggvason, G., Numerical simulations of the Rayleigh-Taylor instability, J. Comput. Phys., 1988, 75: 253-282.［4］Mulder, W., Osher, S., Sethian, J., Computing interface motion in compressible gas dynamics, J. Comput. Phys., 1992, 100: 209-228.［5］Osher, S., Sethian, J., Fronts propagating with curvature-dependent speed: algorithms based on Hamilton-Jacobi formulations, J. Compput. Phys., 1988, 79(1): 12-49.［6］Li, X. L., Study of three-dimensional Rayleigh-Taylor instability in compressible fluids through level set method and parallel computation, Phys. Fluids, 1993, A(5): 1904-1913.［7］Holmes, R. L, Grove, J. W., Sharp, D. H., Numerical investigation of Richtmyer-Meshkov instability using front tracking, J. Fluid Mech., 1995, 301: 51-64.［8］Gardner, C., Glimm, J., McBryan, O. et al., The dynamics of bubble growth for Rayleigh-Taylor unstable interfaces, Phys. Fluids, 1988, 31: 447-465.［9］He Xiaoyi, Chen Shiyi, Zhang Raoyang, A lattice Boltzmann scheme for incompressible multiphase flow and its application in simulation of Rayleigh-Taylor instability, J. Comput Phys., 1999, 152: 642-663.［10］Li, X. L., Jin, B. X., Glimm, J., Numerical study for the three-dimensional Rayleigh-Taylor instability through the TVD/AC scheme and parallel computation, J. Comput. Phys., 1996, 126: 343-355.［11］Taylor, G. I., The stability of liquid surface when accelerated in a direction perpendicular to their planes, I, Proc. Roy. Soc., London, 1950, A201: 192-196.［12］Abarzhi, S. I., Stable steady flow in the Rayleigh-Taylor instability, Phs. Rev. Lett., 1998, 81: 337-340.［13］Zhang, Q., The motion of single-mode Rayleigh-Taylor unstable interfaces, IMPACT Comput. Sci. Eng., 1991, 3: 277-389.［14］Deardorff. J. W
Toward analytic theory of the Rayleigh-Taylor instability: lessons from a toy model
Mailybaev, Alexei A
2016-01-01
In this work we suggest that a turbulent phase of the Rayleigh-Taylor instability can be explained as a universal stochastic wave traveling with constant speed in a properly renormalized system. This wave, originating from ordinary deterministic chaos in a renormalized time, has two constant limiting states at both sides. These states are related to the initial discontinuity at large scales and to stationary turbulence at small scales. The theoretical analysis is confirmed with extensive numerical simulations made for a new shell model, which features all basic properties of the phenomenological theory for the Rayleigh-Taylor instability.
Rayleigh Taylor Instability Growth in NIC Capsules with Engineered Defects
Peterson, K. J.; Hammel, B. A.; Suter, L. J.; Clark, D. S.; Farley, D. R.; Landen, O. L.; Scott, H.; Moreno, K.; Vesey, R. A.; Herrmann, M. C.; Nakhleh, C. W.; Golovkin, I.; Regan, S. P.; Epstein, R.
2011-10-01
In order to achieve thermonuclear burn and energy gain in ICF capsules, the growth of hydrodynamic instabilities must be understood and controlled. Experiments are planned to measure time dependent hydrodynamic instability growth of engineered defects on the surface of NIC capsules using x-ray radiography. We will present an analysis of synthetic radiography from 2D and 3D HYDRA simulations with various x-ray drive fluxes and show how these results will be used to assess code predictions of instability growth and mix. We will also discuss how these results correlate with capsule performance and observables from hot spot self emission imaging and Ge spectroscopy. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
Adams, Colin Stuart [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of New Mexico, Albuquerque, NM (United States); Univ. of Washington, Seattle, WA (United States)
2015-01-15
The Rayleigh-Taylor instability causes mixing in plasmas throughout the universe, from micron-scale plasmas in inertial confinement fusion implosions to parsec-scale supernova remnants. The evolution of this interchange instability in a plasma is influenced by the presence of viscosity and magnetic fields, both of which have the potential to stabilize short-wavelength modes. Very few experimental observations of Rayleigh-Taylor growth in plasmas with stabilizing mechanisms are reported in the literature, and those that are reported are in sub-millimeter scale plasmas that are difficult to diagnose. Experimental observations in well-characterized plasmas are important for validation of computational models used to make design predictions for inertial confinement fusion efforts. This dissertation presents observations of instability growth during the interaction between a high Mach-number, initially un-magnetized plasma jet and a stagnated, magnetized plasma. A multi-frame fast camera captures Rayleigh-Taylor-instability growth while interferometry, spectroscopy, photodiode, and magnetic probe diagnostics are employed to estimate plasma parameters in the vicinity of the collision. As the instability grows, an evolution to longer mode wavelength is observed. Comparisons of experimental data with idealized magnetohydrodynamic simulations including a physical viscosity model suggest that the observed instability evolution is consistent with both magnetic and viscous stabilization. These data provide the opportunity to benchmark computational models used in astrophysics and fusion research.
Adams, Colin Stuart [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of New Mexico, Albuquerque, NM (United States)
2015-01-15
The Rayleigh-Taylor instability causes mixing in plasmas throughout the universe, from micron-scale plasmas in inertial confinement fusion implosions to parsec-scale supernova remnants. The evolution of this interchange instability in a plasma is influenced by the presence of viscosity and magnetic fields, both of which have the potential to stabilize short-wavelength modes. Very few experimental observations of Rayleigh-Taylor growth in plasmas with stabilizing mechanisms are reported in the literature, and those that are reported are in sub-millimeter scale plasmas that are difficult to diagnose. Experimental observations in well-characterized plasmas are important for validation of computational models used to make design predictions for inertial confinement fusion efforts. This dissertation presents observations of instability growth during the interaction between a high Mach-number, initially un-magnetized plasma jet and a stagnated, magnetized plasma. A multi-frame fast camera captures Rayleigh-Taylor-instability growth while interferometry, spectroscopy, photodiode, and magnetic probe diagnostics are employed to estimate plasma parameters in the vicinity of the collision. As the instability grows, an evolution to longer mode wavelength is observed. Comparisons of experimental data with idealized magnetohydrodynamic simulations including a physical viscosity model suggest that the observed instability evolution is consistent with both magnetic and viscous stabilization. These data provide the opportunity to benchmark computational models used in astrophysics and fusion research.
Large-eddy-simulation of 3-dimensional Rayleigh-Taylor instability in incompressible fluids
无
2002-01-01
The 3-dimensional incompressible Rayleigh-Taylor instability is numerically studied through the large-eddy-simulation (LES) approach based on the passive scalar transport model. Both the instantaneous velocity and the passive scalar fields excited by sinusoidal perturbation and random perturbation are simulated. A full treatment of the whole evolution process of the instability is addressed. To verify the reliability of the LES code, the averaged turbulent energy as well as the flux of passive scalar are calculated at both the resolved scale and the subgrid scale. Our results show good agreement with the experimental and other numerical work. The LES method has proved to be an effective approach to the Rayleigh-Taylor instability.
无
2003-01-01
A hybrid model of MHD and kinetic theory is proposed to investigate the synergetic stabilizing effects of sheared axial flow and finite Larmor radius on the Rayleigh-Taylor instability in Z-pinch implosions.In our model the MHD plasma is considered to respond to a perturbation with exp[i(k*x-ωt)] at frequency ω+ik2⊥ρ2iΩi instead of frequency ω,where k2⊥ρ2i is the finite Larmor radius effects given from the general kinetic theory of magnetized plasma.Therefore linearized continuity and momentum equations include automatically the finite Larmor radius effects.Dispersion relation is derived,which includes the effects of a density discontinuity and the finite Larmor radius as well as a sheared flow that produces the Kelvin-Helmholtz instability.The dispersion equation is examined in three cases.The results indicate that the synergetic effect of sheared axial flow and the finite Larmor radius can mitigate both the Rayleigh-Taylor instability and the hybrid Rayleigh-Taylor/Kelvin-Helmholtz instability.Moreover,the synergetic mitigation effect is stronger than either of them acting separately.
Study on Electrohydrodynamic Rayleigh-Taylor Instability with Heat and Mass Transfer
Mukesh Kumar Awasthi
2014-01-01
Full Text Available The linear analysis of Rayleigh-Taylor instability of the interface between two viscous and dielectric fluids in the presence of a tangential electric field has been carried out when there is heat and mass transfer across the interface. In our earlier work, the viscous potential flow analysis of Rayleigh-Taylor instability in presence of tangential electric field was studied. Here, we use another irrotational theory in which the discontinuities in the irrotational tangential velocity and shear stress are eliminated in the global energy balance. Stability criterion is given by critical value of applied electric field as well as critical wave number. Various graphs have been drawn to show the effect of various physical parameters such as electric field, heat transfer coefficient, and vapour fraction on the stability of the system. It has been observed that heat transfer and electric field both have stabilizing effect on the stability of the system.
Mitigation Effect of Finite Larmor Radius on Rayleigh-Taylor Instability in Z-Pinch Implosions
邱孝明; 黄林; 简广德
2002-01-01
Based on the framework of magnetohydrodynamic theory, a simple model is proposed to study the mitigation effect of finite Larmor radius on the Rayleigh-Taylor instability in Z-pinch implosions. In this model, taking account of Ti ≥ Te in Z-pinch implosions we believe that the magnetohydrodynamic plasma responds to a perturbation (～ exp [i (k. x - ωt)]) at frequency (ω + ik2⊥ρ2iΩi) instead of frequency ω, where k2⊥ρ2i is due to the finite Larmor radius effects expressed from the generalkinetic theory of magnetized plasma. Therefore the linearized continuity and momentum equations for the perturbed mass-density and velocity include the finite Larmor radius effects. The calculations indicate that, in the wavenumber region of interest, the finite Larmor radius effects can mitigate the Rayleigh-Taylor instability in Z-pinch implosions.
LI Zhang-Guo; LIU Qiu-Sheng; LIU Rong; HU Wei; DENG Xin-Yu
2009-01-01
A computational simulation is conducted to investigate the influence of Rayleigh-Taylor instability on liquid propellant reorientation flow dynamics for the tank of CZ-3A launch vehicle series fuel tanks in a low-gravity environment. The volume-of-fluid (VOF) method is used to simulate the free surface flow of gas-liquid. The process of the liquid propellant reorientation started from initially fiat and curved interfaces are numerically studied. These two different initial conditions of the gas-liquid interface result in two modes of liquid flow. It is found that the Rayleigh-Taylor instability can be reduced evidently at the initial gas-liquid interface with a high curve during the process of liquid reorientation in a low-gravity environment.
Ablative Stabilization of the Deceleration-Phase Rayleigh-Taylor Instability, control No. 2000-107
Lobatchev, V.; Betti, R.
2000-10-01
The growth rates of the deceleration-phase Rayleigh-Taylor instability for imploding inertial confinement fusion capsules are calculated and compared with the results of numerical simulations. It is found that the unstable spectrum and the growth rates are significantly reduced by the finite ablation flow at the shell's inner surface. For typical direct-drive capsules designed for the National Ignition Facility, the unstable spectrum exhibits a cutoff for {ell} {approx} 90.
Direct numerical simulations of type Ia supernovae flames II: The Rayleigh-Taylor instability
Bell, J.B.; Day, M.S.; Rendleman, C.A.; Woosley, S.E.; Zingale, M.
2004-01-12
A Type Ia supernova explosion likely begins as a nuclear runaway near the center of a carbon-oxygen white dwarf. The outward propagating flame is unstable to the Landau-Darrieus, Rayleigh-Taylor, and Kelvin-Helmholtz instabilities, which serve to accelerate it to a large fraction of the speed of sound. We investigate the Rayleigh-Taylor unstable flame at the transition from the flamelet regime to the distributed-burning regime, around densities of 10e7 gm/cc, through detailed, fully resolved simulations. A low Mach number, adaptive mesh hydrodynamics code is used to achieve the necessary resolution and long time scales. As the density is varied, we see a fundamental change in the character of the burning--at the low end of the density range the Rayleigh-Taylor instability dominates the burning, whereas at the high end the burning suppresses the instability. In all cases, significant acceleration of the flame is observed, limited only by the size of the domain we are able to study. We discuss the implications of these results on the potential for a deflagration to detonation transition.
Andrei, A. Ivanov
2001-06-15
In this thesis we're studying both the general case of the 'classic' Rayleigh-Taylor instability (in incompressible fluids) and more specific cases of the instabilities of Rayleigh-Taylor type in magnetized plasmas, in the liners or wire array implosions etc. We have studied the influence of the Hall diffusion of magnetic field on the growth rate of the instability. We have obtained in this work a self-similar solution for the widening of the initial profile of the magnetic field and for the wave of the penetration of magnetic field. After that the subsequent evolution of the magnetic field in plasma opening switches (POS) has been examined. We have shown the possibility of the existence of a strong rarefaction wave for collisional and non-collisional cases. This wave can explain the phenomenon of the opening of POS. The effect of the suppression of Rayleigh-Taylor instability by forced oscillations of the boundary between two fluids permits us to propose some ideas for the experiments of inertial fusion. We have considered the general case of the instability, in other words - two incompressible viscous superposed fluids in a gravitational field. We have obtained an exact analytical expression for the growth rate and then we have analyzed the influence of the parameters of external 'pumping' on the instability. These results can be applied to a wide range of systems, starting from classic hydrodynamics and up to astrophysical plasmas. The scheme of wire arrays has become recently a very popular method to obtain a high power X-radiation or for a high quality implosion in Z-pinches. The experimental studies have demonstrated that the results of implosion are much better for the case of multiple thin wires situated cylindrically than in a usual liner scheme. We have examined the problem modeling the stabilization of Rayleigh-Taylor instability for a wire array system. The reason for instability suppression is the regular spatial modulation of
Smalyuk, V A
2012-06-07
Rayleigh-Taylor (RT) instability is one of the major concerns in inertial confinement fusion (ICF) because it amplifies target modulations in both acceleration and deceleration phases of implosion, which leads to shell disruption and performance degradation of imploding targets. This article reviews experimental results of the RT growth experiments performed on OMEGA laser system, where targets were driven directly with laser light. RT instability was studied in the linear and nonlinear regimes. The experiments were performed in acceleration phase, using planar and spherical targets, and in deceleration phase of spherical implosions, using spherical shells. Initial target modulations consisted of 2-D pre-imposed modulations, and 2-D and 3-D modulations imprinted on targets by the non-uniformities in laser drive. In planar geometry, the nonlinear regime was studied using 3-D modulations with broadband spectra near nonlinear saturation levels. In acceleration-phase, the measured modulation Fourier spectra and nonlinear growth velocities are in good agreement with those predicted by Haan's model [Haan S W 1989 Phys. Rev. A 39 5812]. In a real-space analysis, the bubble merger was quantified by a self-similar evolution of bubble size distributions [Oron D et al 2001 Phys. Plasmas 8, 2883]. The 3-D, inner-surface modulations were measured to grow throughout the deceleration phase of spherical implosions. RT growth rates are very sensitive to the drive conditions, therefore they can be used to test and validate drive physics in hydrodynamic codes used to design ICF implosions. Measured growth rates of pre-imposed 2-D target modulations below nonlinear saturation levels were used to validate non-local thermal electron transport model in laser-driven experiments.
Strong stabilization of the Rayleigh-Taylor instability by material strength at Mbar pressures
Park, H S; Lorenz, K T; Cavallo, R M; Pollaine, S M; Prisbrey, S T; Rudd, R E; Becker, R C; Bernier, J V; Remington, B A
2009-11-19
Experimental results showing significant reductions from classical in the Rayleigh-Taylor (RT) instability growth rate due to high pressure effective lattice viscosity are presented. Using a laser created ramped drive, vanadium samples are compressed and accelerated quasi-isentropically at {approx}1 Mbar pressures, while maintaining the sample in the solid-state. Comparisons with simulations and theory indicate that the high pressure, high strain rate conditions trigger a phonon drag mechanism, resulting in the observed high effective lattice viscosity and strong stabilization of the RT instability.
Lattice Boltzmann simulation of three-dimensional Rayleigh-Taylor instability
Liang, H.; Li, Q. X.; Shi, B. C.; Chai, Z. H.
2016-03-01
In this paper, the three-dimensional (3D) Rayleigh-Taylor instability (RTI) with low Atwood number (At=0.15 ) in a long square duct (12 W ×W ×W ) is studied by using a multiple-relaxation-time lattice Boltzmann (LB) multiphase model. The effect of the Reynolds number on the interfacial dynamics and bubble and spike amplitudes at late time is investigated in detail. The numerical results show that at sufficiently large Reynolds numbers, a sequence of stages in the 3D immiscible RTI can be observed, which includes the linear growth, terminal velocity growth, reacceleration, and chaotic development stages. At late stage, the RTI induces a very complicated topology structure of the interface, and an abundance of dissociative drops are also observed in the system. The bubble and spike velocities at late stage are unstable and their values have exceeded the predictions of the potential flow theory [V. N. Goncharov, Phys. Rev. Lett. 88, 134502 (2002), 10.1103/PhysRevLett.88.134502]. The acceleration of the bubble front is also measured and it is found that the normalized acceleration at late time fluctuates around a constant value of 0.16. When the Reynolds number is reduced to small values, some later stages cannot be reached sequentially. The interface becomes relatively smoothed and the bubble velocity at late time is approximate to a constant value, which coincides with the results of the extended Layzer model [S.-I. Sohn, Phys. Rev. E 80, 055302(R) (2009), 10.1103/PhysRevE.80.055302] and the modified potential theory [R. Banerjee, L. Mandal, S. Roy, M. Khan, and M. R. Guptae, Phys. Plasmas 18, 022109 (2011), 10.1063/1.3555523]. In our simulations, the Graphics Processing Unit (GPU) parallel computing is also used to relieve the massive computational cost.
Proton Beam Fast Ignition Fusion: Synergy of Weibel and Rayleigh-Taylor Instabilities
Stefan, V. Alexander
2011-04-01
The proton beam generation and focusing in fast ignition inertial confinement fusion is studied. The spatial and energy spread of the proton beam generated in a laser-solid interaction is increased due to the synergy of Weibel and Rayleigh-Taylor instabilities. The focal spot radius can reach 100 μm, which is nearly an order of magnitude larger than the optimal value. The energy spread decreases the beam deposition energy in the focal spot. Under these conditions, ignition of a precompressed DT fuel is achieved with the beam powers much higher than the values presently in consideration. Work supported in part by NIKOLA TESLA Laboratories (Stefan University), La Jolla, CA.
Reckinger, Scott James [Montana State Univ., Bozeman, MT (United States); Livescu, Daniel [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Vasilyev, Oleg V. [Univ. of Colorado, Boulder, CO (United States)
2016-09-02
A comprehensive numerical methodology has been developed that handles the challenges introduced by considering the compressive nature of Rayleigh-Taylor instability (RTI) systems, which include sharp interfacial density gradients on strongly stratified background states, acoustic wave generation and removal at computational boundaries, and stratification-dependent vorticity production. The computational framework is used to simulate two-dimensional single-mode RTI to extreme late-times for a wide range of flow compressibility and variable density effects. The results show that flow compressibility acts to reduce the growth of RTI for low Atwood numbers, as predicted from linear stability analysis.
Combined effect of horizontal magnetic field and vorticity on Rayleigh Taylor instability
Banerjee, Rahul
2016-01-01
In this research, the height, curvature and velocity of the bubble tip in Rayleigh-Taylor instability at arbitrary Atwood number with horizontal magnetic field are investigated. To support the earlier simulation and experimental results, the vorticity generation inside the bubble is introduced. It is found that, in early nonlinear stage, the temporal evolution of the bubble tip parameters depend essentially on the strength and initial perturbation of the magnetic field, although the asymptotic nature coincides with the non magnetic case. The model proposed here agrees with the previous linear, nonlinear and simulation observations.
Quantum Effects on Rayleigh-Taylor Instability of Incompressible Plasma in a Vertical Magnetic Field
G.A.Hoshoudy
2010-01-01
@@ Quantum effects on Rayleigh-Taylor instability of a stratified incompressible plasmas layer under the influence of vertical magnetic field are investigated.The solutions of the linearized equations of motion together with the boundary conditions lead to deriving the relation between square normalized growth rate and square normalized wawe number in two algebraic equations and are numerically analyzed.In the case of the real solution of these two equations,they can be combined to generate a single equation.The results show that the presence of vertical magnetic field beside the quantum effect will bring about more stability on the growth rate of unstable configuration.
The viscous surface-internal wave problem: nonlinear Rayleigh-Taylor instability
Wang, Yanjin
2011-01-01
We consider the free boundary problem for two layers of immiscible, viscous, incompressible fluid in a uniform gravitational field, lying above a rigid bottom in a three-dimensional horizontally periodic setting. The effect of surface tension is either taken into account at both free boundaries or neglected at both. We are concerned with the Rayleigh-Taylor instability, so we assume that the upper fluid is heavier than the lower fluid. When the surface tension at the free internal interface is below a critical value, which we identify, we establish that the problem under consideration is nonlinearly unstable.
Kilkenny, J.D.
1994-08-04
As shown elsewhere an ablatively imploded shell is hydrodynamically unstable, the dominant instability being the well known Rayleigh-Taylor instability with growth rate {gamma} = {radical}Akg where k = 2{pi}/{lambda} is the wave number, g is the acceleration and A the Attwood number ({rho}{sub hi} {minus} {rho}{sub lo})/({rho}{sub hi} + {rho}{sub lo}) where {rho}{sub hi} is the density of the heavier fluid and {rho}{sub lo} is the density of the lighter fluid. A theoretical understanding of ablative stabilization has gradually evolved, confirmed over the last five years by experiments. The linear growth is very well understood with excellent agreement between experiment and simulation for planar geometry with wavelengths in the region of 30--100{mu}m. There is an accurate, albeit phenomenological dispersion relation. The non-linear growth has been measured and agrees with calculations. In this lecture, the authors go into the fundamentals of the Rayleigh-Taylor instability and the experimental measurements that show it is stabilized sufficiently by ablation in regimes relevant to ICF.
Simulations of Rayleigh Taylor Instabilities in the presence of a Strong Radiative shock
Trantham, Matthew; Kuranz, Carolyn; Shvarts, Dov; Drake, R. P.
2016-10-01
Recent Supernova Rayleigh Taylor experiments on the National Ignition Facility (NIF) are relevant to the evolution of core-collapse supernovae in which red supergiant stars explode. Here we report simulations of these experiments using the CRASH code. The CRASH code, developed at the University of Michigan to design and analyze high-energy-density experiments, is an Eulerian code with block-adaptive mesh refinement, multigroup diffusive radiation transport, and electron heat conduction. We explore two cases, one in which the shock is strongly radiative, and another with negligible radiation. The experiments in all cases produced structures at embedded interfaces by the Rayleigh Taylor instability. The weaker shocked environment is cooler and the instability grows classically. The strongly radiative shock produces a warm environment near the instability, ablates the interface, and alters the growth. We compare the simulated results with the experimental data and attempt to explain the differences. This work is funded by the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, Grant Number DE-NA0002956.
Jian Guangde; Huang Lin; Qiu Xiaoming
2005-01-01
The assembling stabilizing effect of the finite Larmor radius (FLR) and the sheared axial flow (SAF) on the Rayleigh-Taylor instability in Z-pinch implosions is studied by means of the incompressible finite Larmor radius magnetohydrodynamic (MHD) equations. The finite Larmor radius effects are introduced in the momentum equation with the sheared axial flow through an anisotropic ion stress tensor. In this paper a linear mode equation is derived that is valid for arbitrary kL, where k is the wave number and L is the plasma shell thickness. Numerical solutions are presented. The results indicate that the short-wavelength modes of the RayleighTaylor instability are easily stabilized by the individual effect of the finite Larmor radius or the sheared axial flow. The assembling effects of the finite Larmor radius and sheared axial flow can heavily mitigate the Rayleigh-Taylor instability, and the unstable region can be compressed considerably.
Analytical modeling of magnetic Rayleigh-Taylor instabilities in compressible fluids
Liberatore, Stéphane; Bouquet, Serge
2008-11-01
The magnetic Rayleigh-Taylor instability (MRTI) is investigated in the case of compressible plasmas. The goal of this work is highlighting the influence of both the magnetic field and the compressibility of the material on the growth rate of the Rayleigh-Taylor instability, compared to the classical growth rate derived for incompressible fluids. Our analytical linear models are derived in the framework of the ideal magnetohydrodynamics theory. Three general dispersion relations are obtained: (1) Two for stratified fluids, including compressible (denoted CS∥ when the wave vector k is parallel to the equilibrium magnetic field B0 and CS⊥ when k ⊥B0) and incompressible (denoted IS∥ and IS⊥) and (2) one for incompressible uniform density fluids, including finite mass (denoted Ifm) and infinite (denoted IU). For k ⊥B0, Ifm, IU, and IS⊥ are unmagnetized cases. Comparisons of those various configurations are performed and several differences are pointed out. The main results are as follows: Stratification weakens the MRTI while compressibility has a destabilizing effect. The magnetic field enhances these phenomena. The CS∥ and IU configurations have an identical cutoff wave number. The upper fluid (also called heavy fluid) is more sensitive to compressibility than the light one when k ∥B0. Finally, the CS∥ case is more sensitive than the CS⊥ one to physical variations.
Mokler, Matthew; Roberts, Michael; Jacobs, Jeffrey
2011-11-01
Incompressible Rayleigh-Taylor instability experiments are presented in which two stratified miscible liquids having Atwood number of 0.2 are accelerated in a vertical linear induction motor driven drop tower. A test sled having only vertical freedom of motion contains the experiment tank and visualization equipment. The sled is positioned at the top of the tower within the linear motors and accelerated downward causing the initially stable interface to be unstable and allowing the Rayleigh-Taylor instability to develop. Experiments are presented with and without forced initial perturbations produced by vertically oscillating the test sled prior to the start of acceleration. The interface is visualized using a 445nm laser light source that illuminates a fluorescent dye mixed in one of the fluids. The resulting fluorescent images are recorded using a monochromatic high speed video camera. The laser beam is synchronously swept across the fluorescent fluid, at the frame rate of the camera, exposing a single plane of the interface allowing for the measurement of spike and bubble mixing layer growth rates.
Mokler, Matthew; Roberts, Michael; Jacobs, Jeffrey
2013-11-01
Incompressible Rayleigh-Taylor instability experiments are presented in which two stratified liquids having Atwood number of 0.2 are accelerated in a vertical linear induction motor driven drop tower. A test sled having only vertical freedom of motion contains the experiment tank and visualization equipment. The sled is positioned at the top of the tower within the linear induction motors and accelerated downward causing the initially stable interface to be unstable and allowing the Rayleigh-Taylor instability to develop. Forced and unforced experiments are conducted using both immiscible and miscible liquid combinations. Forced initial perturbations are produced by vertically oscillating the test sled prior to the start of acceleration. The interface is visualized using a 445 nm laser light source that illuminates a fluorescent dye mixed in one of the fluids. The resulting fluorescent images are recorded using a monochromatic high speed video camera. The laser beam is synchronously swept across the fluorescent fluid, at the frame rate of the camera, exposing a single plane of the interface allowing for the measurement of spike and bubble growth. Comparisons between miscible and immiscible mixing layer distributions are made from the resulting interface concentration profiles.
Similar Rayleigh-Taylor Instability of Shock Fronts Perturbed by Corrugated Interfaces
HE Yong; HU Xi-Wei; JIANG Zhong-He
2011-01-01
@@ Instability of a planar shock front perturbed by a corrugated interface is analyzed,where the perturbation wavelength is along the shock front plane.The presented analysis involves the effects of the features on the shock front,which is different from a general method presented by D'yakov and Kontorovich,where the shock front is taken as an infinitely discontinuity.The growth rate of the instability of the perturbed shock front is obtained and compared with the growth rate of the Rayleigh-Taylor instability(RTI) of an interface,on which the density gradient and the initial conditions are similar to the perturbed shock front.The analysis and comparisons of the growth rate of the instability indicate that the features of the shock front should be considered seriously in the shock interface interactions.%Instability of a planar shock front perturbed by a corrugated interface is analyzed, where the perturbation wavelength is along the shock front plane. The presented analysis involves the effects of the features on the shock front, which is different from a general method presented by D'yakov and Kontorovich, where the shock front is taken as an infinitely discontinuity. The growth rate of the instability of the perturbed shock front is obtained and compared with the growth rate of the Rayleigh-Taylor instability (RTI) of an interface, on which the density gradient and the initial conditions are similar to the perturbed shock front. The analysis and comparisons of the growth rate of the instability indicate that the features of the shock front should be considered seriously in the shock interface interactions.
Shvarts, D.; Oron, D.; Kartoon, D.; Rikanati, A.; Sadot, O.; Srebro, Y.; Yedvab, Y.; Ofer, D.; Levin, A.; Sarid, E.; Ben-Dor, G.; Erez, L.; Erez, G.; Yosef-Hai, A.; Alon, U.; Arazi, L.
2016-10-01
The late-time nonlinear evolution of the Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) instabilities for random initial perturbations is investigated using a statistical mechanics model based on single-mode and bubble-competition physics at all Atwood numbers (A) and full numerical simulations in two and three dimensions. It is shown that the RT mixing zone bubble and spike fronts evolve as h ~ α · A · gt2 with different values of a for the bubble and spike fronts. The RM mixing zone fronts evolve as h ~ tθ with different values of θ for bubbles and spikes. Similar analysis yields a linear growth with time of the Kelvin-Helmholtz mixing zone. The dependence of the RT and RM scaling parameters on A and the dimensionality will be discussed. The 3D predictions are found to be in good agreement with recent Linear Electric Motor (LEM) experiments.
Direct simulation Monte Carlo investigation of the Rayleigh-Taylor instability
Gallis, M. A.; Koehler, T. P.; Torczynski, J. R.; Plimpton, S. J.
2016-08-01
The Rayleigh-Taylor instability (RTI) is investigated using the direct simulation Monte Carlo (DSMC) method of molecular gas dynamics. Here, fully resolved two-dimensional DSMC RTI simulations are performed to quantify the growth of flat and single-mode perturbed interfaces between two atmospheric-pressure monatomic gases as a function of the Atwood number and the gravitational acceleration. The DSMC simulations reproduce many qualitative features of the growth of the mixing layer and are in reasonable quantitative agreement with theoretical and empirical models in the linear, nonlinear, and self-similar regimes. In some of the simulations at late times, the instability enters the self-similar regime, in agreement with experimental observations. For the conditions simulated, diffusion can influence the initial instability growth significantly.
Gauglitz, Phillip A.; Wells, Beric E.; Buchmiller, William C.; Rassat, Scot D.
2013-03-21
In Hanford underground waste storage tanks, a typical waste configuration is settled beds of waste particles beneath liquid layers. The settled beds are typically composed of layers, and these layers can have different physical and chemical properties. One postulated configuration within the settled bed is a less-dense layer beneath a more-dense layer. The different densities can be a result of different gas retention in the layers or different degrees of settling and compaction in the layers. This configuration can experience a Rayleigh-Taylor (RT) instability where the less dense lower layer rises into the upper layer. Previous studies of gas retention and release have not considered potential buoyant motion within a settle bed of solids. The purpose of this report is to provide a review of RT instabilities, discuss predictions of RT behavior for sediment layers, and summarize preliminary experimental observations of RT instabilities in simulant experiments.
Development of Richtmyer-Meshkov and Rayleigh-Taylor Instability in presence of magnetic field
Khan, Manoranjan; Banerjee, Rahul; Roy, Sourav; Gupta, M R
2011-01-01
Fluid instabilities like Rayleigh-Taylor,Richtmyer-Meshkov and Kelvin-Helmholtz instability can occur in a wide range of physical phenomenon from astrophysical context to Inertial Confinement Fusion(ICF).Using Layzer's potential flow model, we derive the analytical expressions of growth rate of bubble and spike for ideal magnetized fluid in R-T and R-M cases. In presence of transverse magnetic field the R-M and R-T instability are suppressed or enhanced depending on the direction of magnetic pressure and hydrodynamic pressure. Again the interface of two fluid may oscillate if both the fluids are conducting. However the magnetic field has no effect in linear case.
The effect of a magnetic field on the development of Rayleigh Taylor type instability
Syusyukin, A.I.
1984-01-01
The results are presented of an experimental study of magnetohydrodynamic (MGD) instability of the Rayleigh Taylor type. The effect of a magnetic field on the development of magnetohydrodynamic instability was studied in the free surfaces of an accelerating electricity conducting piston. The tests were conducted with a liquid metallic piston and with a piston which is made up of a liquid which does not conduct electricity and one which does. It is shown that a rise in the magnetic induction leads to a more intense development of the instability which is accompanied by a more rapid destruction of the dense structure of the piston. The mechanism of destruction of a free surface under the effects of bulk forces is discussed.
Compressibility Effect on the Rayleigh-Taylor Instability with Sheared Magnetic Fields
Ruderman, M. S.
2017-04-01
We study the effect of plasma compressibility on the Rayleigh-Taylor instability of a magnetic interface with a sheared magnetic field. We assume that the plasma is ideal and the equilibrium quantities are constant above and below the interface. We derive the dispersion equation. Written in dimensionless variables, it contains seven dimensionless parameters: the ratio of plasma densities above and below the interface ζ, the ratio of magnetic field magnitude squared χ, the shear angle α, the plasma beta above and below the interface, β2 and β1, the angle between the perturbation wave number and the magnetic field direction above the interface φ, and the dimensionless wave number κ. Only six of these parameters are independent because χ, β1, and β2 are related by the condition of total pressure continuity at the interface. Only perturbations with the wave number smaller than the critical wave number are unstable. The critical wave number depends on φ, but it is independent of β1 and β2, and is the same as that in the incompressible plasma approximation. The dispersion equation is solved numerically with ζ= 100, χ= 1, and β1 = β2 = β. We obtain the following results. When β decreases, so does the maximum instability increment. However, the effect is very moderate. It is more pronounced for high values of α. We also calculate the dependence on φ of the maximum instability increment with respect to κ. The instability increment takes its maximum at φ= φm. Again, the decrease of β results in the reduction of the instability increment. This reduction is more pronounced for high values of |φ- φm|. When both α and |φ- φm| are small, the reduction effect is practically negligible. The theoretical results are applied to the magnetic Rayleigh-Taylor instability of prominence threads in the solar atmosphere.
Roberts, Michael Scott
The Rayleigh-Taylor instability is a buoyancy driven instability that takes place in a stratified fluid system with a constant acceleration directed from the heavy fluid into the light fluid. In this study, both experimental data and numerical simulations are presented. Experiments are performed primarily using a lithium-tungstate aqueous solution as the heavy liquid, but sometimes a calcium nitrate aqueous solution is used for comparison purposes. Experimental data is obtained for both miscible and immiscible fluid combinations. For the miscible experiments the light liquid is either ethanol or isopropanol, and for the immiscible experiments either silicone oil or trans-anethole is used. The resulting Atwood number is either 0.5 when the lithium-tungstate solution is used or 0.2 when the calcium nitrate solution is used. These fluid combinations are either forced or left unforced. The forced experiments have an initial perturbation imposed by vertically oscillating the liquid containing tank to produce Faraday waves at the interface. The unforced experiments rely on random interfacial fluctuations, due to background noise, to seed the instability. The liquid combination is partially enclosed in a test section that is accelerated downward along a vertical rail system causing the Rayleigh-Taylor instability. Accelerations of approximately 1g (with a weight and pulley system) or 10g (with a linear induction motor system) are experienced by the liquids. The tank is backlit and digitally recorded with high speed video cameras. These experiments are then simulated with the incompressible, Navier-Stokes code Miranda. The main focus of this study is the growth parameter (α) of the mixing region produced by the instability after it has become apparently self-similar and turbulent. The measured growth parameters are compared to determine the effects of miscibility and initial perturbations (of the small wavelength, finite bandwidth type used here). It is found that while
The effect of normal electric field on the evolution of immiscible Rayleigh-Taylor instability
Tofighi, Nima; Ozbulut, Murat; Feng, James J.; Yildiz, Mehmet
2016-10-01
Manipulation of the Rayleigh-Taylor instability using an external electric field has been the subject of many studies. However, most of these studies are focused on early stages of the evolution. In this work, the long-term evolution of the instability is investigated, focusing on the forces acting on the interface between the two fluids. To this end, numerical simulations are carried out at various electric permittivity and conductivity ratios as well as electric field intensities using Smoothed Particle Hydrodynamics method. The electric field is applied in parallel to gravity to maintain unstable evolution. The results show that increasing top-to-bottom permittivity ratio increases the rising velocity of the bubble while hindering the spike descent. The opposite trend is observed for increasing top-to-bottom conductivity ratio. These effects are amplified at larger electric field intensities, resulting in narrower structures as the response to the excitation is non-uniform along the interface.
Particle drift model for Z-pinch-driven magneto-Rayleigh-Taylor instability
Dan, Jia Kun; Xu, Qiang; Wang, Kun Lun; Ren, Xiao Dong; Huang, Xian Bin
2016-09-01
A theoretical model of Z-pinch driven magneto-Rayleigh-Taylor instability is proposed based on the particle drift point of view, which can explain the helical instability structure observed in premagnetized imploding liner experiments. It is demonstrated that all possible drift motions, including polarization drift, gradient drift, and curvature drift, which can lead to charge separations, each will attribute to an effective gravity acceleration. Theoretical predictions given by this model are dramatically different from those given by previous theories which have been readily recovered in the theory presented here as a limiting case. The theory shows qualitative agreement with available experimental data of the pitch angle and provides certain predictions to be verified.
Effect of enhanced thermal dissipation on the Rayleigh-Taylor instability in emulsion-like media
Toor, A.; Ryutov, D.
1997-07-01
Rayleigh-Taylor instability in a finely structured emulsion-like medium consisting of the two components of different compressibility is considered. Although the term ``emulsion`` is used to describe the structure of the medium, under typical fast Z-pinch conditions both components behave as gases. The two components are chosen in such a way that their densities in the unperturbed state are approximately equal. Specific emphasis has been made on the analysis of perturbations with the scale {lambda} considerably exceeding the size of the grains a. Averaged equations describing such perturbations am derived. The difference in compressibility of the two components leads to the formation of temperature variations at the scale a, and increases the rate of the thermal dissipation by a factor ({lambda}/a){sup 2}. The strongest stabilizing effect of the thermal dissipation takes place when the thermal relaxation time is comparable with the instability growth rate.
Rayleigh-Taylor instability in Magnetohydrodynamic Simulations of the Crab Nebula
Porth, Oliver; Keppens, Rony
2014-01-01
In this paper we discuss the development of Rayleigh-Taylor filaments in axisymmetric simulations of Pulsar wind nebulae (PWN). High-resolution adaptive mesh refinement magnetohydrodynamic (MHD) simulations are used to resolve the non-linear evolution of the instability. The typical separation of filaments is mediated by the turbulent flow in the nebula and hierarchical growth of the filaments. The strong magnetic dissipation and field-randomization found in recent global three-dimensional simulations of PWN suggests that magnetic tension is not strong enough to suppress the growth of RT filaments, in agreement with the observations of prominent filaments in the Crab nebula. The long-term axisymmetric results presented here confirm this finding.
On the Rayleigh-Taylor instability for incompressible viscous magnetohydrodynamic equations
Jiang, Fei; Wang, Yanjin
2012-01-01
We study the Rayleigh-Taylor problem for two incompressible, immiscible, viscous magnetohydrodynamic (MHD) flows, with zero resistivity, surface tension (or without surface tenstion) and special initial magnetic field, evolving with a free interface in the presence of a uniform gravitational field. First, we reformulate in Lagrangian coordinates MHD equations in a infinite slab as one for the Navier-Stokes equations with a force term induced by the fluid flow map. Then we analyze the linearized problem around the steady state which describes a denser immiscible fluid lying above a light one with an free interface separating the two fluids, and both fluids being in (unstable) equilibrium. By a general method of studying a family of modified variational problems, we construct smooth (when restricted to each fluid domain) solutions to the linearized problem that grow exponentially fast in time in Sobolev spaces, thus leading to an global instability result for the linearized problem. Finally, using these patholo...
Nonequilibrium thermohydrodynamic effects on the Rayleigh-Taylor instability in compressible flows
Lai, Huilin; Xu, Aiguo; Zhang, Guangcai; Gan, Yanbiao; Ying, Yangjun; Succi, Sauro
2016-08-01
The effects of compressibility on Rayleigh-Taylor instability (RTI) are investigated by inspecting the interplay between thermodynamic and hydrodynamic nonequilibrium phenomena (TNE, HNE, respectively) via a discrete Boltzmann model. Two effective approaches are presented, one tracking the evolution of the local TNE effects and the other focusing on the evolution of the mean temperature of the fluid, to track the complex interfaces separating the bubble and the spike regions of the flow. It is found that both the compressibility effects and the global TNE intensity show opposite trends in the initial and the later stages of the RTI. Compressibility delays the initial stage of RTI and accelerates the later stage. Meanwhile, the TNE characteristics are generally enhanced by the compressibility, especially in the later stage. The global or mean thermodynamic nonequilibrium indicators provide physical criteria to discriminate between the two stages of the RTI.
The Rayleigh-Taylor instability of Newtonian and non-Newtonian fluids
Doludenko, A. N.; Fortova, S. V.; Son, E. E.
2016-10-01
Along with Newtonian fluids (for example, water), fluids with non-Newtonian rheology are widespread in nature and industry. The characteristic feature of a non-Newtonian fluid is the non-linear dependence between the shear stress and shear rate tensors. The form of this relation defines the types of non-Newtonian behavior: viscoplastic, pseudoplastic, dilatant and viscoelastic. The present work is devoted to the study of the Rayleigh-Taylor instability in pseudoplastic fluids. The main aim of the work is to undertake a direct three-dimensional numerical simulation of the mixing of two media with various rheologies and obtain the width of the mixing layer and the kinetic energy spectra, depending on the basic properties of the shear thinning liquids and the Atwood number. A theoretical study is carried out on the basis of the Navier-Stokes equation system for weakly compressible media.
Non-linear Evolution of Rayleigh-Taylor Instability in a Radiation Supported Atmosphere
Jiang, Yan-Fei; Stone, James
2012-01-01
The non-linear regime of Rayleigh-Taylor instability (RTI) in a radiation supported atmosphere, consisting of two uniform fluids with different densities, is studied numerically. We perform simulations using our recently developed numerical algorithm for multi-dimensional radiation hydrodynamics based on a variable Eddington tensor as implemented in Athena, focusing on the regime where scattering opacity greatly exceeds absorption opacity. We find that the radiation field can reduce the growth and mixing rate of RTI, but this reduction is only significant when radiation pressure significantly exceeds gas pressure. Small scale structures are also suppressed in this case. In the non-linear regime, dense fingers sink faster than rarefied bubbles can rise, leading to asymmetric structures about the interface. By comparing the calculations that use a variable Eddington tensor (VET) versus the Eddington approximation, we demonstrate that anisotropy in the radiation field can affect the non-linear development of RTI...
Miscible and immiscible, forced and unforced experiments on the Rayleigh-Taylor instability
Roberts, Michael; Mokler, Matthew; Jacobs, Jeffrey
2012-11-01
Experiments are presented in which an incompressible system of two liquids is accelerated to produce the Rayleigh-Taylor instability. In these experiments, the initially stable, stratified liquid combination is accelerated downward on a vertical rail system in one of two experimental apparatuses: an apparatus in which a system of weights and pulleys accelerates the liquid filled tank, or a new apparatus which uses linear induction motors to accelerate the tank to produce much greater acceleration levels. Both miscible and immiscible liquid combinations are used. In both apparatuses the resulting fluid flows are visualized with backlit imaging using LED backlights in conjunction with monochrome high-speed video cameras, both of which travel with the moving fluid filled containers. Initial perturbations are either unforced and allowed to progress from background noise or forced by vertically oscillating the liquid combination to produce parametric internal waves. The mixing layer growth rate α is determined for all cases and compared to numerical simulations and past experiments.
Numerical study on Rayleigh-Taylor instabilities in the lightning return stroke
Chen, Qiang, E-mail: cq0405@126.com [National Key Laboratory of Electromagnetic Environment and Electro-optical Engineering, PLA University of Science and Technology, Nanjing 210007 (China); Luoyang Electronic Equipment Testing Center, Luoyang 471000 (China); Chen, Bin, E-mail: emcchen@163.com; Shi, Lihua; Yi, Yun [National Key Laboratory of Electromagnetic Environment and Electro-optical Engineering, PLA University of Science and Technology, Nanjing 210007 (China); Wang, Yangyang [Department of Electro-optical Engineering, Electronic Engineering Institute of PLA, Hefei 230037 (China)
2015-09-15
The Rayleigh-Taylor (R-T) instabilities are important hydrodynamics and magnetohydrodynamics (MHD) phenomena that are found in systems in high energy density physics and normal fluids. The formation and evolution of the R-T instability at channel boundary during back-flow of the lightning return stroke are analyzed using the linear perturbation theory and normal mode analysis methods, and the linear growth rate of the R-T instability in typical condition for lightning return stroke channel is obtained. Then, the R-T instability phenomena of lightning return stroke are simulated using a two-dimensional Eulerian finite volumes resistive radiation MHD code. The numerical results show that the evolution characteristics of the R-T instability in the early stage of back-flow are consistent with theoretical predictions obtained by linear analysis. The simulation also yields more evolution characteristics for the R-T instability beyond the linear theory. The results of this work apply to some observed features of the return stroke channel and further advance previous theoretical and experimental work.
Numerical study on Rayleigh-Taylor instabilities in the lightning return stroke
Chen, Qiang; Chen, Bin; Shi, Lihua; Yi, Yun; Wang, Yangyang
2015-09-01
The Rayleigh-Taylor (R-T) instabilities are important hydrodynamics and magnetohydrodynamics (MHD) phenomena that are found in systems in high energy density physics and normal fluids. The formation and evolution of the R-T instability at channel boundary during back-flow of the lightning return stroke are analyzed using the linear perturbation theory and normal mode analysis methods, and the linear growth rate of the R-T instability in typical condition for lightning return stroke channel is obtained. Then, the R-T instability phenomena of lightning return stroke are simulated using a two-dimensional Eulerian finite volumes resistive radiation MHD code. The numerical results show that the evolution characteristics of the R-T instability in the early stage of back-flow are consistent with theoretical predictions obtained by linear analysis. The simulation also yields more evolution characteristics for the R-T instability beyond the linear theory. The results of this work apply to some observed features of the return stroke channel and further advance previous theoretical and experimental work.
Simulating the Rayleigh-Taylor instability in polymer fluids with dissipative particle dynamics
Li, Yanggui; Geng, Xingguo; Zhuang, Xin; Wang, Lihua; Ouyang, Jie
2016-04-01
The Rayleigh-Taylor (RT) instability that occurs in the flow of polymer fluids is numerically investigated with dissipative particle dynamics (DPD) method at the mesoscale particle level. For modeling two-phase flow, the Flory-Huggins parameter is introduced to model binary fluids. And the polymer chains in fluids are described by the modified FENE model that depicts both the elastic tension and the elastic repulsion between the adjacent beads with bond length as the equilibrium length of one segment. Besides, a bead repulsive potential is employed to capture entanglements between polymer chains. Through our model and numerical simulation, we research the dynamics behaviors of the RT instability in polymer fluid medium. Furthermore, we also explore the effects of polymer volume concentration, chain length, and extensibility on the evolution of RT instability. These simulation results show that increasing any of the parameters, concentration, chain length, and extensibility, the saturation length of spikes becomes longer, and the two polymer fluids have less mixture. On the contrary, for the case of low concentration, or short chain, or small extensibility, the spikes easily split and break up, and the RT instability pattern evolves into chaotic structure. These observations indicate that the polymer and its properties drastically modify the RT instability pattern.
The Experimental Study of Rayleigh-Taylor Instability using a Linear Induction Motor Accelerator
Yamashita, Nicholas; Jacobs, Jeffrey
2009-11-01
The experiments to be presented utilize an incompressible system of two stratified miscible liquids of different densities that are accelerated in order to produce the Rayleigh-Taylor instability. Three liquid combinations are used: isopropyl alcohol with water, a calcium nitrate solution or a lithium polytungstate solution, giving Atwood numbers of 0.11, 0.22 and 0.57, respectively. The acceleration required to drive the instability is produced by two high-speed linear induction motors mounted to an 8 m tall drop tower. The motors are mounted in parallel and have an effective acceleration length of 1.7 m and are each capable of producing 15 kN of thrust. The liquid system is contained within a square acrylic tank with inside dimensions 76 x76x184 mm. The tank is mounted to an aluminum plate, which is driven by the motors to create constant accelerations in the range of 1-20 g's, though the potential exists for higher accelerations. Also attached to the plate are a high-speed camera and an LED backlight to provide continuous video of the instability. In addition, an accelerometer is used to provide acceleration measurements during each experiment. Experimental image sequences will be presented which show the development of a random three-dimensional instability from an unforced initial perturbation. Measurements of the mixing zone width will be compared with traditional growth models.
Steiner, Adam; Yager-Elorriaga, David; Patel, Sonal; Jordan, Nicholas; Gilgenbach, Ronald; Lau, Y. Y.
2015-11-01
The electrothermal instability (ETI) and magneto-Rayleigh Taylor instability (MRT) are important in the implosion of metallic liners, such as magnetized liner implosion fusion (MagLIF). The MAIZE linear transformer driver (LTD) at the University of Michigan generates 200 ns risetime-current pulses of 500 to 600 kA into Al foil liners to study plasma instabilities and implosion dynamics, most recently MRT growth on imploding cylindrical liners. A full circuit model of MAIZE, along with I-V measurements, yields time-resolved load inductance. This has enabled measurements of an effective current-carrying radius to determine implosion velocity and plasma-vacuum interface acceleration. Measurements are also compared to implosion data from 4-time-frame laser shadowgraphy. Improved resolution measurements on the laser shadowgraph system have been used to examine the liner interface early in the shot to examine surface perturbations resulting from ETI for various seeding conditions. Fourier analysis examines the growth rates of wavelength bands of these structures to examine the transition from ETI to MRT. This work was supported by the U.S. DoE through award DE-SC0012328. S.G. Patel is supported by Sandia National Labs. D.A. Yager is supported by NSF fellowship grant DGE 1256260.
Khomenko, E; de Vicente, A; Collados, M; Luna, M
2014-01-01
We study the Rayleigh-Taylor instability (RTI) at a prominence-corona transition region in a non-linear regime. Our aim is to understand how the presence of neutral atoms in the prominence plasma influences the instability growth rate, and the evolution of velocity, magnetic field vector and thermodynamic parameters of turbulent drops. We perform 2.5D numerical simulations of the instability initiated by a multi-mode perturbation at the corona-prominence interface using a single-fluid MHD approach including a generalized Ohm's law. The initial equilibrium configuration is purely hydrostatic and contains a homogeneous horizontal magnetic field forming an angle with the direction in which the plasma is perturbed. We analyze simulations with two different orientations of the magnetic field. For each field orientation we compare two simulations, one for the pure MHD case, and one including the ambipolar diffusion in the Ohm's law (AD case). Other than that, both simulations for each field orientation are identica...
Hillier, Andrew; Isobe, Hiroaki; Shibata, Kazunari [Kwasan and Hida Observatories, Kyoto University, Kyoto (Japan); Berger, Thomas, E-mail: andrew@kwasan.kyoto-u.ac.jp [Lockheed Martin Solar and Astrophysics Laboratory, Palo Alto, CA (United States)
2012-02-20
The launch of the Hinode satellite led to the discovery of rising plumes, dark in chromospheric lines, that propagate from large ({approx}10 Mm) bubbles that form at the base of quiescent prominences. The plumes move through a height of approximately 10 Mm while developing highly turbulent profiles. The magnetic Rayleigh-Taylor instability was hypothesized to be the mechanism that drives these flows. In this study, using three-dimensional (3D) MHD simulations, we investigate the nonlinear stability of the Kippenhahn-Schlueter prominence model for the interchange mode of the magnetic Rayleigh-Taylor instability. The model simulates the rise of a buoyant tube inside the quiescent prominence model, where the interchange of magnetic field lines becomes possible at the boundary between the buoyant tube and the prominence. Hillier et al. presented the initial results of this study, where upflows of constant velocity (maximum found 6 km s{sup -1}) and a maximum plume width Almost-Equal-To 1.5 Mm which propagate through a height of approximately 6 Mm were found. Nonlinear interaction between plumes was found to be important for determining the plume dynamics. In this paper, using the results of ideal MHD simulations, we determine how the initial parameters for the model and buoyant tube affect the evolution of instability. We find that the 3D mode of the magnetic Rayleigh-Taylor instability grows, creating upflows aligned with the magnetic field of constant velocity (maximum found 7.3 km s{sup -1}). The width of the upflows is dependent on the initial conditions, with a range of 0.5-4 Mm which propagate through heights of 3-6 Mm. These results are in general agreement with the observations of the rising plumes.
Bhowmick, Aklant K.; Abarzhi, Snezhana
2016-10-01
Rayleigh Taylor instability in a power-law time dependent acceleration field is investigated for a flow with the symmetry group p6mm (hexagonal) in the plane normal to acceleration. The Regular asymptotic solutions form a one-parameter family and the physically significant solution is identified with the one having the fastest growth and being stable (bubble tip velocity). Two distinct regimes are identified dependent on the acceleration exponent, the RM-type regime, where the dynamics is identical to conventional RM instability and is dominated by initial conditions, and the RT-type regime where the dynamics is dominated by the acceleration term. For the latter, the time dependence has profound effects on the dynamics. In the RT non-linear regime, the time dependence has no consequence on the morphology of the bubbles but the growth rate (bubble tip velocity) evolves as power law with the exponent set by the acceleration. The solutions for a one-parameter family, and are convergent with exponential decay of Fourier amplitudes close to the physical solution. The solutions are stable at maximum tip velocity and flat bubbles are unstable, and the growth/decay of perturbations is no longer purely exponential and depends on the acceleration exponent. The work is supported by the US National Science Foundation.
Bhowmick, Aklant K.; Abarzhi, Snezhana
2016-11-01
Rayleigh Taylor instability in a power-law time dependent acceleration field is investigated theoretically for a flow with the symmetry group p6mm (hexagon) in the plane normal to acceleration. In the nonlinear regime, regular asymptotic solutions form a one-parameter family. The physically significant solution is identified with the one having the fastest growth and being stable (bubble tip velocity). Two distinct regimes are identified depending on the acceleration exponent. Particularly, the RM-type regime, where the dynamics is identical to conventional RM instability and is dominated by initial conditions, and the RT-type regime where the dynamics is dominated by the acceleration term. For the latter, the time dependence has profound effects on the dynamics. In the RT non-linear regime, the time dependence has no consequence on the morphology of the bubbles; the growth rate (bubble tip velocity) evolves as power law with the exponent set by the acceleration. The solutions for a one-parameter family, and are convergent with exponential decay of Fourier amplitudes. The solutions are stable at maximum tip velocity, whereas flat bubbles are unstable, and the growth/decay of perturbations is no longer purely exponential and depends on the acceleration exponent. The work is supported by the US National Science Foundation.
Algorithm and exploratory study of the Hall MHD Rayleigh-Taylor instability.
Gardiner, Thomas Anthony
2010-09-01
This report is concerned with the influence of the Hall term on the nonlinear evolution of the Rayleigh-Taylor (RT) instability. This begins with a review of the magnetohydrodynamic (MHD) equations including the Hall term and the wave modes which are present in the system on time scales short enough that the plasma can be approximated as being stationary. In this limit one obtains what are known as the electron MHD (EMHD) equations which support two characteristic wave modes known as the whistler and Hall drift modes. Each of these modes is considered in some detail in order to draw attention to their key features. This analysis also serves to provide a background for testing the numerical algorithms used in this work. The numerical methods are briefly described and the EMHD solver is then tested for the evolution of whistler and Hall drift modes. These methods are then applied to study the nonlinear evolution of the MHD RT instability with and without the Hall term for two different configurations. The influence of the Hall term on the mixing and bubble growth rate are analyzed.
Rayleigh-Taylor instability in partially ionized compressible plasmas: one fluid approach
Diaz, A J; Collados, M
2014-01-01
We study the modification of the classical criterion for the linear onset and growth rate of the Rayleigh-Taylor instability (RTI) in a partially ionized (PI) plasma in the one-fluid description, considering a generalized induction equation. The governing linear equations and appropriate boundary conditions, including gravitational terms, are derived and applied to the case of the RTI in a single interface between two partially ionized plasmas. The boundary conditions lead to an equation for the frequencies in which some of them have positive complex parts, marking the appearance of the RTI. We study the ambipolar term alone first, extending the result to the full induction equation later. We find that the configuration is always unstable because of the presence of a neutral species. In the classical stability regime the growth rate is small, since the collisions prevent the neutral fluid to fully develop the RTI. For parameters in the classical instability regime the growth rate is lowered, but for the consi...
Effects of acceleration rate on Rayleigh-Taylor instability in elastic-plastic materials
Banerjee, Arindam; Polavarapu, Rinosh
2016-11-01
The effect of acceleration rate in the elastic-plastic transition stage of Rayleigh-Taylor instability in an accelerated non-Newtonian material is investigated experimentally using a rotating wheel experiment. A non-Newtonian material (mayonnaise) was accelerated at different rates by varying the angular acceleration of a rotating wheel and growth patterns of single mode perturbations with different combinations of amplitude and wavelength were analyzed. Experiments were run at two different acceleration rates to compare with experiments presented in prior years at APS DFD meetings and the peak amplitude responses are captured using a high-speed camera. Similar to the instability acceleration, the elastic-plastic transition acceleration is found to be increasing with increase in acceleration rate for a given amplitude and wavelength. The experimental results will be compared to various analytical strength models and prior experimental studies using Newtonian fluids. Authors acknowledge funding support from Los Alamos National Lab subcontract(370333) and DOE-SSAA Grant (DE-NA0001975).
3-D simulations to investigate initial condition effects on the growth of Rayleigh-Taylor mixing
Andrews, Malcolm J [Los Alamos National Laboratory
2008-01-01
The effect of initial conditions on the growth rate of turbulent Rayleigh-Taylor (RT) mixing has been studied using carefully formulated numerical simulations. An integrated large-eddy simulation (ILES) that uses a finite-volume technique was employed to solve the three-dimensional incompressible Euler equations with numerical dissipation. The initial conditions were chosen to test the dependence of the RT growth parameters ({alpha}{sub b}, {alpha}{sub s}) on variations in (a) the spectral bandwidth, (b) the spectral shape, and (c) discrete banded spectra. Our findings support the notion that the overall growth of the RT mixing is strongly dependent on initial conditions. Variation in spectral shapes and bandwidths are found to have a complex effect of the late time development of the RT mixing layer, and raise the question of whether we can design RT transition and turbulence based on our choice of initial conditions. In addition, our results provide a useful database for the initialization and development of closures describing RT transition and turbulence.
Martinez, D A; Smalyuk, V A; Kane, J O; Casner, A; Liberatore, S; Masse, L P
2015-05-29
We investigate on the National Ignition Facility the ablative Rayleigh-Taylor instability in the transition from weakly nonlinear to highly nonlinear regimes. A planar plastic package with preimposed two-dimensional broadband modulations is accelerated for up to 12 ns by the x-ray drive of a gas-filled Au radiation cavity with a radiative temperature plateau at 175 eV. This extended tailored drive allows a distance traveled in excess of 1 mm for a 130 μm thick foil. Measurements of the modulation optical density performed by x-ray radiography show that a bubble-merger regime for the Rayleigh-Taylor instability at an ablation front is achieved for the first time in indirect drive. The mutimode modulation amplitudes are in the nonlinear regime, grow beyond the Haan multimode saturation level, evolve toward the longer wavelengths, and show insensitivity to the initial conditions.
Martinez, David
2015-11-01
We investigate on the National Ignition Facility (NIF) the ablative Rayleigh-Taylor (RT) instability in the transition from linear to highly nonlinear regimes. This work is part of the Discovery Science Program on NIF and of particular importance to indirect-drive inertial confinement fusion (ICF) where careful attention to the form of the rise to final peak drive is calculated to prevent the RT instability from shredding the ablator in-flight and leading to ablator mixing into the cold fuel. The growth of the ablative RT instability was investigated using a planar plastic foil with pre-imposed two-dimensional broadband modulations and diagnosed using x-ray radiography. The foil was accelerated for 12ns by the x-ray drive created in a gas-filled Au radiation cavity with a radiative temperature plateau at 175 eV. The dependence on initial conditions was investigated by systematically changing the modulation amplitude, ablator material and the modulation pattern. For each of these cases bubble mergers were observed and the nonlinear evolution of the RT instability showed insensitivity to the initial conditions. This experiment provides critical data needed to validate current theories on the ablative RT instability for indirect drive that relies on the ablative stabilization of short-scale modulations for ICF ignition. This paper will compare the experimental data to the current nonlinear theories. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344. Lawrence Livermore National Security, LLC.
Viscous effects on the Rayleigh-Taylor instability with background temperature gradient
Gerashchenko, S
2016-01-01
The growth rate of the compressible Rayleigh-Taylor instability is studied in the presence of a background temperature gradient, $\\Theta$, using a normal mode analysis. The effect of $\\Theta$ variation is examined for three interface types corresponding to combinations of the viscous properties of the fluids (inviscid-inviscid, viscous-viscous and viscous-inviscid) at different Atwood numbers, $At$, and, when at least one of the fluids' viscosity is non-zero, as a function of the Grashof number. For the general case, the resulting ordinary differential equations are solved numerically; however, dispersion relations for the growth rate are presented for several limiting cases. An analytical solution is found for the inviscid-inviscid interface and the corresponding dispersion equation for the growth rate is obtained in the limit of a large $\\Theta$. For the viscous-inviscid case, a dispersion relation is derived in the incompressible limit and $\\Theta=0$. Compared to $\\Theta=0$ case, the role of $\\Theta0$ (col...
Fully-kinetic simulations of the Rayleigh-Taylor instability in high-energy-density plasmas
Alves, E. Paulo; Mori, Warren B.; Fiuza, Frederico
2016-10-01
The Rayleigh-Taylor instability (RTI) in high-energy-density (HED) plasmas is a central problem in a wide range of scenarios. It dictates, for instance, the dynamics of supernovae in astrophysical plasmas, and is also recognized as a critical challenge to achieving ignition in inertial confinement fusion. In some of these conditions the Larmor radius or Coulomb mean free path (m.f.p.) is finite, allowing kinetic effects to become important, and it is not fully clear how the development of the RTI deviates from standard hydrodynamic behavior. In order to obtain an accurate description of the RTI in these HED conditions it is essential to capture the self-consistent interplay between collisional and collisionless plasma processes, and the role of self-generated electric and magnetic fields. We have explored the dynamics of the RTI in HED plasma conditions using first-principles particle-in-cell simulations combined with Monte Carlo binary collisions. Our simulations capture the role of kinetic diffusion as well as the self-generated electric (e.g. space-charge) and magnetic (e.g. Biermann battery) fields on the growth rate and nonlinear evolution of the RTI for different plasma conditions. We will discuss how different collisional m.f.p. relative to the collisionless plasma skin depth affect the RTI development. This work was supported by the DOE Office of Science, Fusion Energy Science (FWP 100182).
Controlling Rayleigh-Taylor instabilities in solid liner implosions with rotating magnetic fields
Schmit, P. F.; McBride, R. D.; Robertson, G. K.; Velikovich, A. L.
2016-10-01
We report calculations demonstrating that a remarkable reduction in the growth of the magneto-Rayleigh-Taylor instability (MRTI) in initially solid, cylindrical metal shells can be achieved by applying a magnetic drive with a tilted, dynamic polarization, forming a solid-liner dynamic screw pinch (SLDSP). Using a self-consistent analytic framework, we demonstrate that MRTI growth factors of the most detrimental modes may be reduced by up to two orders of magnitude relative to conventional z-pinch implosions. One key application of this technique is to enable increasingly stable, higher performance liner implosions to achieve fusion. We weigh the potentially dramatic benefits of the SLDSP against the practical tradeoffs required to achieve the desired drive field history and identify promising target designs for future experimental and computational investigations. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. DoE's National Nuclear Security Administration under contract DE-AC04-94AL85000.
Numerical Experiments with a Turbulent Single-Mode Rayleigh-Taylor Instability
Cloutman, L.D.
2000-04-01
Direct numerical simulation is a powerful tool for studying turbulent flows. Unfortunately, it is also computationally expensive and often beyond the reach of the largest, fastest computers. Consequently, a variety of turbulence models have been devised to allow tractable and affordable simulations of averaged flow fields. Unfortunately, these present a variety of practical difficulties, including the incorporation of varying degrees of empiricism and phenomenology, which leads to a lack of universality. This unsatisfactory state of affairs has led to the speculation that one can avoid the expense and bother of using a turbulence model by relying on the grid and numerical diffusion of the computational fluid dynamics algorithm to introduce a spectral cutoff on the flow field and to provide dissipation at the grid scale, thereby mimicking two main effects of a large eddy simulation model. This paper shows numerical examples of a single-mode Rayleigh-Taylor instability in which this procedure produces questionable results. We then show a dramatic improvement when two simple subgrid-scale models are employed. This study also illustrates the extreme sensitivity to initial conditions that is a common feature of turbulent flows.
The Destruction of 3He by Rayleigh-Taylor Instability on the First Giant Branch
Eggleton, P P; Lattanzio, J C
2006-01-01
Low-mass stars, ~1-2 solar masses, near the Main Sequence are efficient at producing 3He, which they mix into the convective envelope on the giant branch and distribute into the Galaxy by way of envelope loss. This process is so efficient that it is difficult to reconcile the observed cosmic abundance of 3He with the predictions of Big Bang nucleosynthesis. In this paper we find, by modeling a red giant with a fully three-dimensional hydrodynamic code and a full nucleosynthetic network, that mixing arises in the supposedly stable and radiative zone between the hydrogen-burning shell and the base of the convective envelope. This mixing is due to Rayleigh-Taylor instability within a zone just above the hydrogen-burning shell. In this zone the burning of the 3He left behind by the retreating convective envelope is predominantly by the reaction 3He + 3He -> 4He + 2p, a reaction which, untypically for stellar nuclear reactions, {\\it lowers} the mean molecular weight, leading to a local minimum. This local minimum ...
Zaitsev, V. V.; Kronshtadtov, P. V.; Stepanov, A. V.
2016-09-01
Within the framework of the long-standing so-called "number problem" in the physics of solar flares, we consider the excitation of a super-Dreicer electric field at the leading edge of the electric current pulse that occurs at the chromospheric legs of a coronal magnetic loop as a result of the magnetic Rayleigh-Taylor instability. It is shown that for a sufficiently strong electric current, I0 ≥ 10^{10} A, the current pulse propagates in the non-linear mode and generates a strong longitudinal electric field Ez, which strongly depends on the current ( Ez ∝ I03) and can exceed the Dreicer field ( Ez > ED). In this case, the bulk of electrons in the site of the current pulse is in a runaway mode, and the energy release rate in the chromosphere increases significantly. Super-Dreicer electric fields also provide injection of protons into the regime of acceleration by Langmuir turbulence generated by fast electrons at the leading edge of the electric current pulse. The electric field at the pulse edge can exceed the Dreicer field starting from the chromosphere level with the number density n ≈ 10^{13} cm^{-3}. At a lower current I0 < 10^{10} A, a super-Dreicer mode at the higher levels of the chromosphere with n < 10^{12} cm^{-3} occurs.
Rayleigh-Taylor instability under curved substrates: An optimal transient growth analysis
Balestra, Gioele; Brun, P.-T.; Gallaire, François
2016-12-01
We investigate the stability of thin viscous films coated on the inside of a horizontal cylindrical substrate. In such a case, gravity acts both as a stabilizing force through the progressive drainage of the film and as a destabilizing force prone to form droplets via the Rayleigh-Taylor instability. The drainage solution, derived from lubrication equations, is found asymptotically stable with respect to infinitesimally small perturbations, although in reality, droplets often form. To resolve this paradox, we perform an optimal transient growth analysis for the first-order perturbations of the liquid's interface, generalizing the results of Trinh et al. [Phys. Fluids 26, 051704 (2014), 10.1063/1.4876476]. We find that the system displays a linear transient growth potential that gives rise to two different scenarios depending on the value of the Bond number (prescribing the relative importance of gravity and surface tension forces). At low Bond numbers, the optimal perturbation of the interface does not generate droplets. In contrast, for higher Bond numbers, perturbations on the upper hemicircle yield gains large enough to potentially form droplets. The gain increases exponentially with the Bond number. In particular, depending on the amplitude of the initial perturbation, we find a critical Bond number above which the short-time linear growth is sufficient to trigger the nonlinear effects required to form dripping droplets. We conclude that the transition to droplets detaching from the substrate is noise and perturbation dependent.
Stabilization of the Rayleigh-Taylor instability in quantum magnetized plasmas
Wang, L. F.; Ye, W. H.; He, X. T. [HEDPS and CAPT, Peking University, Beijing 100871 (China); Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China); Yang, B. L. [Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China); Graduate School, China Academy of Engineering Physics, Beijing 100088 (China)
2012-07-15
In this research, stabilization of the Rayleigh-Taylor instability (RTI) due to density gradients, magnetic fields, and quantum effects, in an ideal incompressible plasma, is studied analytically and numerically. A second-order ordinary differential equation (ODE) for the RTI including quantum corrections, with a continuous density profile, in a uniform external magnetic field, is obtained. Analytic expressions of the linear growth rate of the RTI, considering modifications of density gradients, magnetic fields, and quantum effects, are presented. Numerical approaches are performed to solve the second-order ODE. The analytical model proposed here agrees with the numerical calculation. It is found that the density gradients, the magnetic fields, and the quantum effects, respectively, have a stabilizing effect on the RTI (reduce the linear growth of the RTI). The RTI can be completely quenched by the magnetic field stabilization and/or the quantum effect stabilization in proper circumstances leading to a cutoff wavelength. The quantum effect stabilization plays a central role in systems with large Atwood number and small normalized density gradient scale length. The presence of external transverse magnetic fields beside the quantum effects will bring about more stability on the RTI. The stabilization of the linear growth of the RTI, for parameters closely related to inertial confinement fusion and white dwarfs, is discussed. Results could potentially be valuable for the RTI treatment to analyze the mixing in supernovas and other RTI-driven objects.
Reckinger, Scott J.; Livescu, Daniel; Vasilyev, Oleg V.
2016-05-01
An investigation of compressible Rayleigh-Taylor instability (RTI) using Direct Numerical Simulations (DNS) requires efficient numerical methods, advanced boundary conditions, and consistent initialization in order to capture the wide range of scales and vortex dynamics present in the system, while reducing the computational impact associated with acoustic wave generation and the subsequent interaction with the flow. An advanced computational framework is presented that handles the challenges introduced by considering the compressive nature of RTI systems, which include sharp interfacial density gradients on strongly stratified background states, acoustic wave generation and removal at computational boundaries, and stratification dependent vorticity production. The foundation of the numerical methodology described here is the wavelet-based grid adaptivity of the Parallel Adaptive Wavelet Collocation Method (PAWCM) that maintains symmetry in single-mode RTI systems to extreme late-times. PAWCM is combined with a consistent initialization, which reduces the generation of acoustic disturbances, and effective boundary treatments, which prevent acoustic reflections. A dynamic time integration scheme that can handle highly nonlinear and potentially stiff systems, such as compressible RTI, completes the computational framework. The numerical methodology is used to simulate two-dimensional single-mode RTI to extreme late-times for a wide range of flow compressibility and variable density effects. The results show that flow compressibility acts to reduce the growth of RTI for low Atwood numbers, as predicted from linear stability analysis.
Rayleigh-Taylor finger instability mixing in hydrodynamic shell convection models
Mocak, Miroslav
2010-01-01
Mixing processes in stars driven by composition gradients as a result of the Rayleigh-Taylor instability are not anticipated. They are supported only by hydrodynamic studies of stellar convection. We find that such mixing occurs below the bottom edge of convection zones in our multidimensional hydrodynamic shell convection models. It operates at interfaces created by off-center nuclear burning, where less dense gas with higher mean molecular weight is located above denser gas with a lower mean molecular weight. We discuss the mixing under various conditions with hydrodynamic convection models based on stellar evolutionary calculations of the core helium flash in a 1.25 Msun star, the core carbon flash in a 9.3 Msun star, and of oxygen burning shell in a star with a mass of 23 Msun. We simulate the hydrodynamic behavior of shell convection during various phases of stellar evolution with the Eulerian hydrodynamics code HERAKLES in two and three spatial dimensions. Initial models for this purpose are obtained by...
Three-Dimensional DSMC Simulations of the Rayleigh-Taylor Instability in Gases
Koehler, T. P.; Gallis, M. A.; Torczynski, J. R.; Plimpton, S. J.
2016-11-01
The Direct Simulation Monte Carlo (DSMC) method of molecular gas dynamics is applied to simulate the Rayleigh-Taylor instability (RTI) in atmospheric-pressure monatomic gases (e.g., argon and helium). The computational domain is a 1-mm by 1-mm by 4-mm cuboid uniformly divided into 62.5 billion cubical cells. A total of 1 trillion computational molecules are used, and time steps of 0.1 ns are used. Simulations are performed to quantify the growth of perturbations on an initially flat interface as a function of the Atwood number. The DSMC results reproduce many features of the RTI and are in reasonable agreement with theoretical and empirical models. Consistent with previous work, the DSMC simulations indicate that the growth of the RTI follows a universal behavior. The numbers of bubble-spike pairs that eventually appear agree with theoretical values based on the most unstable wavelength and are independent of the statistical representation of the gas. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
Phase-field model for the Rayleigh--Taylor instability of immiscible fluids
Celani, Antonio; Muratore-Ginanneschi, Paolo; Vozella, Lara
2008-01-01
The Rayleigh--Taylor instability of two immiscible fluids in the limit of small Atwood numbers is studied by means of a phase-field description. In this method the sharp fluid interface is replaced by a thin, yet finite, transition layer where the interfacial forces vary smoothly. This is achieved by introducing an order parameter (the phase field) whose variation is continuous across the interfacial layers and is uniform in the bulk region. The phase field model obeys a Cahn--Hilliard equation and is two-way coupled to the standard Navier--Stokes equations. Starting from this system of equations we have first performed a linear analysis from which we have analytically rederived the known gravity-capillary dispersion relation in the limit of vanishing mixing energy density and capillary width. We have performed numerical simulations and identified a region of parameters in which the known properties of the linear phase (both stable and unstable) are reproduced in a very accurate way. This has been done both i...
Zaitsev, V. V.; Kronshtadtov, P. V.; Stepanov, A. V.
2016-11-01
Within the framework of the long-standing so-called "number problem" in the physics of solar flares, we consider the excitation of a super-Dreicer electric field at the leading edge of the electric current pulse that occurs at the chromospheric legs of a coronal magnetic loop as a result of the magnetic Rayleigh-Taylor instability. It is shown that for a sufficiently strong electric current, I0 ≥ 10^{10} A, the current pulse propagates in the non-linear mode and generates a strong longitudinal electric field Ez, which strongly depends on the current (Ez ∝ I03) and can exceed the Dreicer field (Ez > ED). In this case, the bulk of electrons in the site of the current pulse is in a runaway mode, and the energy release rate in the chromosphere increases significantly. Super-Dreicer electric fields also provide injection of protons into the regime of acceleration by Langmuir turbulence generated by fast electrons at the leading edge of the electric current pulse. The electric field at the pulse edge can exceed the Dreicer field starting from the chromosphere level with the number density n ≈ 10^{13} cm^{-3}. At a lower current I0 < 10^{10} A, a super-Dreicer mode at the higher levels of the chromosphere with n < 10^{12} cm^{-3} occurs.
Solar effect on the Rayleigh-Taylor instability growth rate as simulated by the NCAR TIEGCM
Wu, Qian
2017-04-01
The TIEGCM (Thermosphere Ionosphere Electrodynamics General Circulation Model) is used to investigate the solar effect on the equatorial ionospheric Rayleigh-Taylor (R-T) instability growth rate, which is responsible for the occurrence of the plasma bubbles. The R-T growth rate is calculated for the solar maximum year 2003 and minimum 2009. The growth rate is strongly dependent on the solar activity. During solar maximum, the pre-reversal enhancement is much stronger leading to higher R-T growth rate. The R-T growth rates from the TIEGCM follow the same solar dependence as the observed occurrence of equatorial plasma bubbles by DMSP satellites. The R-T growth rate also enhances when the day/night terminator is parallel to the magnetic field line near the equator. The R-T growth rate does not correlate well with the solar F10.7 index on a short time scale ( 10 days) because the field-line integrated electron content gradient cancels out the positive correlation between the vertical ion drift with the F10.7 index. The TIEGCM result shows the importance of the electron content gradient to the R-T growth rate and the plasma bubble occurrence. The bubble occurrence rates were estimated based on the vertical ion drift simulation results.
Miscible and immiscible liquid experiments and simulations on the Rayleigh-Taylor instability
Roberts, Michael; Mokler, Matthew; Cabot, William; Jacobs, Jeffrey
2011-11-01
Experiments and numerical simulations are presented in which an incompressible system of two liquids is accelerated to produce the Rayleigh-Taylor instability. In these experiments, the initially stable, stratified liquid combination is accelerated downward on a vertical rail system in one of two experimental apparatuses: an apparatus in which a system of weights and pulleys accelerates the liquid filled tank (which is affixed to a test sled), or a new apparatus which uses linear induction motors to accelerate the tank (which is attached to an aluminum plate) to produce much greater acceleration levels. Both miscible and immiscible liquid combinations are used. In both apparatuses the resulting fluid flows are visualized with backlit imaging using LED backlights in conjunction with monochrome high-speed video cameras, both of which travel with the moving fluid filled containers. Initial perturbations are either unforced and allowed to progress from background noise or forced by vertically oscillating the liquid combination to produce parametric internal waves. The results of these experiments are compared to numerical simulations performed using the CFD code Miranda.
Analysis of Rayleigh-Taylor Instability Part I: Bubble and Spike Count
Kamath, C; Gezahegne, A; Miller, P
2006-08-08
The use of high-performance computers to simulate hydrodynamic instabilities has resulted in the generation of massive amounts of data. One aspect of the analysis of this data involves the identification and characterization of coherent structures known as ''bubbles'' and ''spikes''. This can be a challenge as there is no precise definition of these structures, and the large size of the data, as well as its distributed nature, precludes any extensive experimentation with different definitions and analysis algorithms. In this report, we describe the use of image processing techniques to identify and count bubbles and spikes in the Rayleigh-Taylor instability, which occurs when an initially perturbed interface between a heavier fluid and a lighter fluid is allowed to grow under the influence of gravity. We analyze data from two simulations, one a large-eddy simulation with 30 terabytes of analysis data, and the other a direct numerical simulation with 80 terabytes of analysis data. We consider different techniques to first convert the three-dimensional data to two dimensions and then count the structures of interest in the two-dimensional data. Our analysis of the bubble and spike counts over time indicates that there are four distinct regimes in the process of the mixing of the two fluids, starting from the initial linear stage, followed by the non-linear stage with weak turbulence, the mixing transition stage, and the final stage of strong turbulence. We also show that our results are relatively insensitive to the parameters used in our algorithms.
Hillier, Andrew S.
2016-10-01
The magnetic Rayleigh-Taylor instability has been shown to play a key role in many astrophysical systems. The equation for the growth rate of this instability in the incompressible limit, and the most-unstable mode that can be derived from it, are often used to estimate the strength of the magnetic field that is associated with the observed dynamics. However, there are some issues with the interpretations given. Here, we show that the class of most unstable modes ku for a given θ, the class of modes often used to estimate the strength of the magnetic field from observations, for the system leads to the instability growing as σ2 = 1/2Agku, a growth rate which is independent of the strength of the magnetic field and which highlights that small scales are preferred by the system, but not does not give the fastest growing mode for that given k. We also highlight that outside of the interchange (k ṡ B = 0) and undular (k parallel to B) modes, all the other modes have a perturbation pair of the same wavenumber and growth rate that when excited in the linear regime can result in an interference pattern that gives field aligned filamentary structure often seen in 3D simulations. The analysis was extended to a sheared magnetic field, where it was found that it was possible to extend the results for a non-sheared field to this case. We suggest that without magnetic shear it is too simplistic to be used to infer magnetic field strengths in astrophysical systems.
Generalized Rayleigh-Taylor instability in the presence of time-dependent equilibrium
Basu, B.
1997-08-01
Plasma instability under the combined influence of the gravity and an eastward electric field, commonly referred to as the generalized Rayleigh-Taylor instability, is considered for a time-dependent equilibrium situation. In the nighttime equatorial ionosphere the time-dependent equilibrium situation arises because of the vertically upward E0×B0 drift of the plasma in conjunction with the altitude-dependent recombination process and the collisional diffusion process. After determining the time-dependent equilibrium density and, in particular, the inverse density gradient scale length L-1, which determines the growth rate of the instability, the stability of small-amplitude perturbations is analyzed. The general solution of the problem, where the effects of all of the above-mentioned processes are included simultaneously, requires numerical analysis. In this paper the effects are studied in limiting situations for which useful analytic solutions can be obtained. The effect of diffusion on L-1 is studied by neglecting both the upward plasma drift and the altitude variation of the recombination frequency νR, and it is verified that the effect is negligible for typical values of the ionospheric parameters. The effects of the other two processes on L-1 are studied by neglecting diffusion. The effect of the altitude variation of νR on the linear growth of the perturbations is studied by adopting the so-called local approximation. It is found that the value of L-1 and hence the value of the growth rate are enhanced by the altitude variation of νR. The enhancements rapidly increase with time to large values at lower altitudes and to significant values at higher altitudes when compared with the values for the spatially uniform νR case. Consequently, the time evolution of the instability and, more importantly, the level of fluctuations at saturation will be significantly affected by the enhancements. The nonlocal aspect of the instability in the upward drifting plasma
Weis, Matthew R.
Cylindrical liner implosions in the Magnetized Liner Inertial Fusion (MagLIF) concept are susceptible to the magneto-Rayleigh-Taylor instability (MRT). The danger of MRT enters in two phases, (1) during the main implosion, the outer surface of the liner is MRT unstable, and (2) during the short time period when the liner decelerates onto hot fuel, the inner surface becomes unstable. Growth of MRT on the outer surface may also feedthrough, which may seed the inner surface leading to high MRT growth in the second phase. If MRT growth becomes large enough, confinement of the fuel is lost. To characterize MRT we solve the linearized, ideal MHD equations in both planar and cylindrical geometries, including the presence of an axial magnetic field and the effects of sausage and kink modes (present in cylindrical coordinates only). In general, the total instability growth rates in cylindrical geometry are found to be larger than those in planar geometry. MRT and feedthrough is shown to be suppressed by strong magnetic field line bending (tension). However, for the same amount of field line bending, feedthrough is the most stabilized. Application of the planar and the cylindrical model to results from the Z-machine at Sandia National Laboratories is presented. Analytic MRT growth rates for a typical magnetized MagLIF-like implosion show the kink mode to be the fastest growing early and very late in the liner implosion (during deceleration). 1D HYDRA MHD simulations are used to generate realistic, evolving profiles (in density, pressure, and magnetic field) during the implosion from which instantaneous growth rates can be computed exactly, using either the planar or cylindrical analytic formulae developed in this thesis. Sophisticated 2D HYDRA MHD simulations were also performed to compare with the analytic theory and experimental results. In 2D, highly compressed axial magnetic fields can reduce the growth of perturbations at the fuel/liner interface during the implosion
Aglitskiy, Y. [Science Applications International Corporation, McLean, Virginia 22150 (United States); Karasik, M.; Velikovich, A. L.; Serlin, V.; Weaver, J. L.; Kessler, T. J.; Schmitt, A. J.; Obenschain, S. P. [Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375 (United States); Nikitin, S. P.; Oh, J. [Research Support Instruments, Lanham, Maryland 20706 (United States); Metzler, N. [Research Support Instruments, Lanham, Maryland 20706 (United States); Ben Gurion University, Beer Sheva (Israel)
2012-10-15
Experimental study of hydrodynamic perturbation evolution triggered by a laser-driven shock wave breakout at the free rippled rear surface of a plastic target is reported. At sub-megabar shock pressure, planar jets manifesting the development of the Richtmyer-Meshkov-type instability in a non-accelerated target are observed. As the shock pressure exceeds 1 Mbar, an oscillatory rippled expansion wave is observed, followed by the 'feedout' of the rear-surface perturbations to the ablation front and the development of the Rayleigh-Taylor instability, which breaks up the accelerated target.
Prajapati, Ramprasad
2016-07-01
The Rayleigh-Taylor (R-T) instability is recently investigated is strongly coupled plasma looking to its importance in dense stellar systems and Inertial Confinement Fusion [1-3]. In the present work, the effect of quantum corrections are studied on Rayleigh-Taylor (R-T) instability and internal wave propagation in a strongly coupled, magnetized, viscoelastic fluid. The modified generalized hydrodynamic model is used to derive the analytical dispersion relation. The internal wave mode and dispersion relation are modified due to the presence of quantum corrections and viscoelastic effects. We observe that strong coupling effects and quantum corrections significantly modifies the dispersion characteristics. The dispersion relation is also discussed in weakly coupled (hydrodynamic) and strongly coupled (kinetic) limits. The explicit expression of R-T instability criterion is derived which is influenced by shear velocity and quantum corrections. Numerical calculations are performed in astrophysical and experimental relevance and it is examined that both the shear and quantum effects suppresses the growth rate of R-T instability. The possible application of the work is discussed in Inertial Confinement Fusion (ICF) to discuss the suppression of R-T instability under considered situation. References: [1] R. P. Prajapati, Phys. Plasmas 23, 022106 (2016). [2] K. Avinash and A. Sen, Phys. Plasmas 22, 083707 (2015). [3] A. Das and P. Kaw, Phys. Plasmas 21 (2014) 062102.
Nonlinear Rayleigh--Taylor instability of the cylindrical fluid flow with mass and heat transfer
ALY R SEADAWY; K EL-RASHIDY
2016-08-01
The nonlinear Rayleigh--Taylor stability of the cylindrical interface between the vapour and liquid phases of a fluid is studied. The phases enclosed between two cylindrical surfaces coaxial with mass and heat transfer is derived from nonlinear Ginzburg--Landau equation. The F-expansion method is used to get exactsolutions for a nonlinear Ginzburg--Landau equation. The region of solutions is displayed graphically.
Gopalakrishnan, S. S.; Carballido-Landeira, J.; De Wit, A.; Knaepen, B.
2017-01-01
The relative role of convection and diffusion is characterized both numerically and experimentally for porous media flows due to a Rayleigh-Taylor instability of a horizontal interface between two miscible solutions in the gravity field. We show that, though globally convection dominates over diffusion during the nonlinear regime, diffusion can locally be as important as convection and even dominates over lateral convection far away from the fingertips. Our experimental and numerical computations of the temporal evolution of the mixing length, the width of the fingers, and their wavelength are in good agreement and show that the lateral evolution of fingers is governed by diffusion.
Sengupta, Tapan K.; Sengupta, Aditi; Sharma, Nidhi; Sengupta, Soumyo; Bhole, Ashish; Shruti, K. S.
2016-09-01
Direct numerical simulations of Rayleigh-Taylor instability (RTI) between two air masses with a temperature difference of 70 K is presented using compressible Navier-Stokes formulation in a non-equilibrium thermodynamic framework. The two-dimensional flow is studied in an isolated box with non-periodic walls in both vertical and horizontal directions. The non-conducting interface separating the two air masses is impulsively removed at t = 0 (depicting a heaviside function). No external perturbation has been used at the interface to instigate the instability at the onset. Computations have been carried out for rectangular and square cross sections. The formulation is free of Boussinesq approximation commonly used in many Navier-Stokes formulations for RTI. Effect of Stokes' hypothesis is quantified, by using models from acoustic attenuation measurement for the second coefficient of viscosity from two experiments. Effects of Stokes' hypothesis on growth of mixing layer and evolution of total entropy for the Rayleigh-Taylor system are reported. The initial rate of growth is observed to be independent of Stokes' hypothesis and the geometry of the box. Following this stage, growth rate is dependent on the geometry of the box and is sensitive to the model used. As a consequence of compressible formulation, we capture pressure wave-packets with associated reflection and rarefaction from the non-periodic walls. The pattern and frequency of reflections of pressure waves noted specifically at the initial stages are reflected in entropy variation of the system.
Mokler, Matthew; Roberts, Michael; Jacobs, Jeffrey
2012-11-01
Incompressible Rayleigh-Taylor instability experiments are presented in which two stratified liquids having Atwood number of 0.2 are accelerated in a vertical linear induction motor driven drop tower. A test sled having only vertical freedom of motion contains the experiment tank and visualization equipment. The sled is positioned at the top of the tower within the linear motors and accelerated downward causing the initially stable interface to be unstable and allowing the Rayleigh-Taylor instability to develop. Experiments are presented with and without forced initial perturbations produced by vertically oscillating the test sled prior to the start of acceleration. Half of the experimental tank is visualized using a 445nm laser light source that illuminates a fluorescent dye mixed in one of the fluids. The other half is illuminated with a white backlight. The resulting images are recorded using a monochromatic high speed video camera allowing for the measurement of spike and bubble mixing layer growth rates for both visualization techniques in a single experiment.
Mokler, Matthew; Jacobs, Jeffrey
2014-11-01
Incompressible Rayleigh-Taylor instability experiments are presented in which two stratified liquids having Atwood number of 0.2 are accelerated in a vertical linear induction motor driven drop tower. A test sled having only vertical freedom of motion contains the experiment tank and visualization equipment. The sled is positioned at the top of the tower within the linear induction motors and accelerated downward causing the initially stable interface to be unstable and allowing the Rayleigh-Taylor instability to develop. Forced and unforced experiments are conducted using an immiscible liquid combination. Forced initial perturbations are produced by vertically oscillating the test sled prior to the start of acceleration. The interface is visualized using a 445 nm laser light source that illuminates a fluorescent dye mixed in one of the fluids and aluminum oxide particles dispersed in both fluids. The laser beam is synchronously swept across the fluorescent fluid, at the frame rate of the camera, exposing a single plane of the interface. The resulting images are recorded using a monochromatic high speed video camera. Time dependent velocity and density fields are obtained from the recorded images allowing for 2D full field measurements of turbulent kinetic energy and turbulent mass transport.
Jiang, Fei
2016-11-01
In this article, we investigate the effect of viscosity on the largest growth rate in the linear Rayleigh-Taylor (RT) instability of a three-dimensional nonhomogeneous incompressible viscous flow in a bounded domain. By adapting a modified variational approach and careful analysis, we show that the largest growth rate in linear RT instability tends to zero as the viscosity coefficient goes to infinity. Moreover, the largest growth rate increasingly converges to one of the corresponding inviscid fluids as the viscosity coefficient goes to zero. Applying these analysis techniques to the corresponding viscous magnetohydrodynamic fluids, we can also show that the largest growth rate in linear magnetic RT instability tends to zero as the strength of horizontal (or vertical) magnetic field increasingly goes to a critical value.
Wang, H.; Currie, C. A.
2013-12-01
For many continental plates, significant vertical motion of Earth's surface has occurred within the plate interior which can not be clearly linked to plate tectonic processes. For example, several craton areas exhibit anomalous basins, e.g., the Williston basin, Illinois basin and Michigan basin in North America. In orogenic belts, there are examples of local areas (~100 km wide) where the surface has undergone subsidence and then uplift of >1 km, such as the Arizaro basin (central Andes) and Wallowa Mountains (northeast Oregon). Given the near-circular shape of the surface deflection, it has been suggested that they may be related to gravitational foundering of dense lower lithosphere, i.e., Rayleigh-Taylor instability (or 'RT drip'). In order to investigate the surface effects of an RT drip, we use two methods: (1) 2D thermal-mechanical numerical models to study links between drip dynamics and crustal deformation and (2) a theoretical analysis of the crustal deformation induced by stresses from the RT drip. The numerical models consist of a continental lithosphere overlying a sublithospheric mantle. A high-density material is placed in the mantle lithosphere or lower crust to initiate a drip event, and a stress-free boundary condition allows the development of surface topography during model evolution. A reasonable range of crustal viscosity and thickness is tested to study the RT drip in different tectonic settings, from a cold craton to a hot orogen with thick crust. Four types of surface deflection are observed: (1) subsidence; (2) subsidence followed by uplift; (3) uplift; and (4) little deflection. When the crust is relatively strong or thin, the surface has a negative elevation, forming a basin. For a weak or thick crust, the RT drip induces crustal flow, leading to crustal thickening that can uplift the surface; an extremely weak crust decouples the surface and RT drip and the surface is unperturbed. Our theoretical analysis considers the surface
Zhou, M. L.; Liu, B.; Hu, R. H.; Shou, Y. R.; Lin, C.; Lu, H. Y.; Lu, Y. R.; Gu, Y. Q.; Ma, W. J.; Yan, X. Q.
2016-08-01
In the case of a thin plasma slab accelerated by the radiation pressure of an ultra-intense laser pulse, the development of Rayleigh-Taylor instability (RTI) will destroy the acceleration structure and terminate the acceleration process much sooner than theoretical limit. In this paper, a new scheme using multiple Gaussian pulses for ion acceleration in a radiation pressure acceleration regime is investigated with particle-in-cell simulation. We found that with multiple Gaussian pulses, the instability could be efficiently suppressed and the divergence of the ion bunch is greatly reduced, resulting in a longer acceleration time and much more collimated ion bunch with higher energy than using a single Gaussian pulse. An analytical model is developed to describe the suppression of RTI at the laser-plasma interface. The model shows that the suppression of RTI is due to the introduction of the long wavelength mode RTI by the multiple Gaussian pulses.
Henry de Frahan, M. T. [Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA; Belof, J. L. [Lawrence Livermore National Laboratory Livermore, California 94551-0808, USA; Cavallo, R. M. [Lawrence Livermore National Laboratory Livermore, California 94551-0808, USA; Raevsky, V. A. [Russian Federal Nuclear Center-VNIIEF, Sarov 607188, Russia; Ignatova, O. N. [Russian Federal Nuclear Center-VNIIEF, Sarov 607188, Russia; Lebedev, A. [Russian Federal Nuclear Center-VNIIEF, Sarov 607188, Russia; Ancheta, D. S. [Lawrence Livermore National Laboratory Livermore, California 94551-0808, USA; El-dasher, B. S. [Lawrence Livermore National Laboratory Livermore, California 94551-0808, USA; Florando, J. N. [Lawrence Livermore National Laboratory Livermore, California 94551-0808, USA; Gallegos, G. F. [Lawrence Livermore National Laboratory Livermore, California 94551-0808, USA; Johnsen, E. [Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA; LeBlanc, M. M. [Lawrence Livermore National Laboratory Livermore, California 94551-0808, USA
2015-06-14
A recent collaboration between LLNL and VNIIEF has produced a set of high explosive driven Rayleigh-Taylor strength data for beryllium. Design simulations using legacy strength models from Steinberg-Lund and Preston-Tonks-Wallace (PTW) suggested an optimal design that would delineate between not just different strength models, but different parameters sets of the PTW model. Application of the models to the post-shot results, however, shows close to classical growth. We characterize the material properties of the beryllium tested in the experiments. We also discuss recent efforts to simulate the data using the legacy strength models as well as the more recent RING relaxation model developed at VNIIEF. Finally, we present shock and ramp-loading recovery experiments conducted as part of the collaboration.
Henry de Frahan, M. T., E-mail: marchdf@umich.edu; Johnsen, E. [Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109 (United States); Belof, J. L.; Cavallo, R. M.; Ancheta, D. S.; El-dasher, B. S.; Florando, J. N.; Gallegos, G. F.; LeBlanc, M. M. [Lawrence Livermore National Laboratory Livermore, California 94551-0808 (United States); Raevsky, V. A.; Ignatova, O. N.; Lebedev, A. [Russian Federal Nuclear Center-VNIIEF, Sarov 607188 (Russian Federation)
2015-06-14
We present a set of high explosive driven Rayleigh-Taylor strength experiments for beryllium to produce data to distinguish predictions by various strength models. Design simulations using existing strength model parameterizations from Steinberg-Lund and Preston-Tonks-Wallace (PTW) suggested an optimal design that would delineate between not just different strength models, but different parameters sets of the PTW model. Application of the models to the post-shot results, however, suggests growth consistent with little material strength. We focus mostly on efforts to simulate the data using published strength models as well as the more recent RING relaxation model developed at VNIIEF. The results of the strength experiments indicate weak influence of strength in mitigating the growth with the RING model coming closest to predicting the material behavior. Finally, we present shock and ramp-loading recovery experiments.
Coupling of sausage, kink, and magneto-Rayleigh-Taylor instabilities in a cylindrical liner
Weis, M. R.; Zhang, P.; Lau, Y. Y., E-mail: yylau@umich.edu; Gilgenbach, R. M. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Michigan 48109-2104 (United States); Schmit, P. F.; Peterson, K. J.; Hess, M. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)
2015-03-15
This paper analyzes the coupling of magneto-Rayleigh-Taylor (MRT), sausage, and kink modes in an imploding cylindrical liner, using ideal MHD. A uniform axial magnetic field of arbitrary value is included in each region: liner, its interior, and its exterior. The dispersion relation is solved exactly, for arbitrary radial acceleration (-g), axial wavenumber (k), azimuthal mode number (m), liner aspect ratio, and equilibrium quantities in each region. For small k, a positive g (inward radial acceleration in the lab frame) tends to stabilize the sausage mode, but destabilize the kink mode. For large k, a positive g destabilizes both the kink and sausage mode. Using the 1D-HYDRA simulation results for an equilibrium model that includes a pre-existing axial magnetic field and a preheated fuel, we identify several stages of MRT-sausage-kink mode evolution. We find that the m = 1 kink-MRT mode has a higher growth rate at the initial stage and stagnation stage of the implosion, and that the m = 0 sausage-MRT mode dominates at the main part of implosion. This analysis also sheds light on a puzzling feature in Harris' classic paper of MRT [E. G. Harris, Phys. Fluids 5, 1057 (1962)]. An attempt is made to interpret the persistence of the observed helical structures [Awe et al., Phys. Rev. Lett. 111, 235005 (2013)] in terms of non-axisymmetric eigenmode.
Coupling of sausage, kink, and magneto-Rayleigh-Taylor instabilities in a cylindrical liner
Weis, M. R.; Zhang, P.; Lau, Y. Y.; Schmit, P. F.; Peterson, K. J.; Hess, M.; Gilgenbach, R. M.
2015-03-01
This paper analyzes the coupling of magneto-Rayleigh-Taylor (MRT), sausage, and kink modes in an imploding cylindrical liner, using ideal MHD. A uniform axial magnetic field of arbitrary value is included in each region: liner, its interior, and its exterior. The dispersion relation is solved exactly, for arbitrary radial acceleration (-g), axial wavenumber (k), azimuthal mode number (m), liner aspect ratio, and equilibrium quantities in each region. For small k, a positive g (inward radial acceleration in the lab frame) tends to stabilize the sausage mode, but destabilize the kink mode. For large k, a positive g destabilizes both the kink and sausage mode. Using the 1D-HYDRA simulation results for an equilibrium model that includes a pre-existing axial magnetic field and a preheated fuel, we identify several stages of MRT-sausage-kink mode evolution. We find that the m = 1 kink-MRT mode has a higher growth rate at the initial stage and stagnation stage of the implosion, and that the m = 0 sausage-MRT mode dominates at the main part of implosion. This analysis also sheds light on a puzzling feature in Harris' classic paper of MRT [E. G. Harris, Phys. Fluids 5, 1057 (1962)]. An attempt is made to interpret the persistence of the observed helical structures [Awe et al., Phys. Rev. Lett. 111, 235005 (2013)] in terms of non-axisymmetric eigenmode.
Measurements of Magneto-Rayleigh-Taylor instability growth in solid liners on the 20 MA Z facility.
Bigman, Verle; Vesey, Roger Alan; Shores, Jonathon; Herrmann, Mark C.; Stamm, Robert (General Atomics, San Diego, CA); Killebrew, Korbie (General Atomics, San Diego, CA); Holt, Randy (General Atomics, San Diego, CA); Blue, Brent (General Atomics, San Diego, CA); Nakhleh, Charlie; McBride, Ryan D.; Leifeste, Gordon T.; Smith, Ian Craig; Stygar, William A.; Porter, John Larry, Jr.; Cuneo, Michael Edward; Bennett, Guy R.; Schroen, Diana Grace (General Atomics, San Diego, CA); Sinars, Daniel Brian; Lopez, Mike R.; Slutz, Stephen A.; Atherton, Briggs W.; Tomlinson, Kurt; Edens, Aaron D.; Savage, Mark Edward; Peterson, Kyle J.
2010-07-01
The magneto-Rayleigh-Taylor (MRT) instability is the most important instability for determining whether a cylindrical liner can be compressed to its axis in a relatively intact form, a requirement for achieving the high pressures needed for inertial confinement fusion (ICF) and other high energy-density physics applications. While there are many published RT studies, there are a handful of well-characterized MRT experiments at time scales >1 {micro}s and none for 100 ns z-pinch implosions. Experiments used solid Al liners with outer radii of 3.16 mm and thicknesses of 292 {micro}m, dimensions similar to magnetically-driven ICF target designs [1]. In most tests the MRT instability was seeded with sinusoidal perturbations ({lambda} = 200, 400 {micro}m, peak-to-valley amplitudes of 10, 20 {micro}m, respectively), wavelengths similar to those predicted to dominate near stagnation. Radiographs show the evolution of the MRT instability and the effects of current-induced ablation of mass from the liner surface. Additional Al liner tests used 25-200 {micro}m wavelengths and flat surfaces. Codes being used to design magnetized liner ICF loads [1] match the features seen except at the smallest scales (<50 {micro}m). Recent experiments used Be liners to enable penetrating radiography using the same 6.151 keV diagnostics and provide an in-flight measurement of the liner density profile.
Hillier, Andrew
2016-01-01
The magnetic Rayleigh-Taylor instability has been shown to play a key role in many astrophysical systems. The equation for the growth rate of this instability in the incompressible limit, and the most-unstable mode that can be derived from it, are often used to estimate the strength of the magnetic field that is associated with the observed dynamics. However, there are some issues with the interpretations given. Here we show that the class of most unstable modes $k_u$ for a given $\\theta$, the class of modes often used to estimate the strength of the magnetic field from observations, for the system leads to the instability growing as $\\sigma^2=1/2 A g k_u$, a growth rate which is independent of the strength of the magnetic field and which highlights that small scales are preferred by the system, but not does not give the fastest growing mode for that given $k$. We also highlight that outside of the interchange ($\\mathbf{k}\\cdot\\mathbf{B}=0$) and undular ($\\mathbf{k}$ parallel to $\\mathbf{B}$) modes, all the o...
Velikovich, A. L.; Giuliani, J. L.; Clark, R. W.; Mikitchuk, D.; Kroupp, E.; Maron, Y.; Fisher, A.; Schmit, P. F.
2014-10-01
Recent progress in developing the MagLIF approach to pulsed-power driven inertial confinement fusion has stimulated the interest in observation and mitigation of the magnetic Rayleigh-Taylor instability (MRTI) of liners and Z-pinches imploded in an axial magnetic field. Theoretical analysis of these issues is particularly important because direct numerical simulation of the MRTI development is challenging due to intrinsically 3D helical structure of the fastest-growing modes. We review the analytical small-amplitude theory of the MRTI perturbation development and the weakly nonlinear theory of MRTI mode interaction, emphasizing basic physics, opportunity for 3D code verification against exact analytical solutions, and stabilization criteria. The theory is compared to the experimental results obtained at Weizmann Institute with gas-puff Z pinches and on the Z facility at Sandia with solid liners imploded in an axial magnetic field. Work supported by the US DOE/NNSA, and by the US-Israel Binational Science Foundation. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.
Yager-Elorriaga, D. A.; Steiner, A. M.; Patel, S. G.; Jordan, N. M.; Gilgenbach, R. M.; Lau, Y. Y.; Weis, M. R.; Zhang, P.
2015-11-01
At the Michigan Accelerator for Inductive Z-Pinch Experiments (MAIZE) facility, a 1-MA Linear Transformer Driver (LTD) is being used to deliver 500-600 kA to cylindrical liners in order to study the magneto Rayleigh-Taylor (MRT), sausage, and kink instabilities in imploding and exploding Al plasmas. The liners studied in this experiment had thicknesses of 400 nm to 30 μm, heights of 1-2 cm, and diameters of 1-6 mm. The plasmas were imaged using 4-time-frame, laser shadowgraphy and shearing-interferometry at 532 nm. For imploding liners, the measured acceleration was found to be less than predicted from the current pulse, indicating significant diffusion of the azimuthal magnetic field. A simple experimental configuration is presented for ``end-on'' laser probing in the r- θ plane in order to study the interior of the liner. Finally, the effects of axial magnetic fields are determined by modifying the return current posts and incorporating external coils. Experimental growth rates are determined and discussed. This work was supported by DOE award DE-SC0012328. S.G. Patel supported by Sandia National Labs. D.A. Yager was supported by NSF fellowship grant DGE 1256260.
Casner, A.; Liberatore, S.; Masse, L.; Martinez, D.; Haan, S. W.; Kane, J.; Moore, A. S.; Seugling, R.; Farrell, M.; Giraldez, E.; Nikroo, A.; Smalyuk, V. A.; Remington, B. A.
2016-05-01
Under the Discovery Science program, the longer pulses and higher laser energies provided by the National Ignition Facility (NIF) have been harnessed to study, first time in indirect-drive, the highly nonlinear stage of the Rayleigh-Taylor Instability (RTI) at the ablation front. A planar plastic package with pre-imposed two-dimensional broadband modulations is accelerated for up to 12 ns by the x-ray drive of a gas-filled gold radiation cavity with a radiative temperature plateau at 175 eV. This extended tailored drive allows a distance traveled in excess of 1 mm for a 130 μm thick foil, a factor 3x larger than previously achieved on other laser facilities. As a consequence, we have measured the ablative RTI in transition from the weakly nonlinear stage up to the deep nonlinear stage for various initial conditions. A bubble merger regime has been observed and the ablative stabilization strength varied by changing the plastic dopant from iodine to germanium.
Egly, H
2007-10-15
This thesis deals with the dynamics of accelerated ablative front spreading in Inertial Confinement Fusion experiments. ICF is designed for the implosion of a deuterium-tritium spherical target. The outer shell, the ablator, is irradiated providing a high level pressure inside the target. During this first stage, the ablation front propagating inwards is perturbed by hydrodynamics instabilities, which can prevent the fusion reaction in the decelerated stage. We propose here a study on Rayleigh-Taylor instabilities during ablation process, in the two dimensional case. In order to obtain a numerical solution, we perform an asymptotic analysis in the limit of a high temperature ratio, between the remaining cold ablator and the hot ablated plasma. This study is divided in two steps. First, the thermo-diffusive part of the set of equations is approximated by a Hele-Shaw model, which is then perturbed by the hydrodynamics part. Using a vortex method, we have to solve the advection of a vortical sheet moving with the ablation front. We compute the numerical solution on an Eulerian mesh coupled with a marker method. The thermal part is computed by implementing the Fat Boundary Method, recently developed. The hydrodynamic part is obtained from a Finite Volume scheme. (author)
Rayleigh-Taylor mixing in supernova experiments
Swisher, N. C.; Abarzhi, S. I., E-mail: snezhana.abarzhi@gmail.com [Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Kuranz, C. C. [University of Michigan, Ann Arbor, Michigan 48109 (United States); Arnett, D. [University of Arizona, Tucson, Arizona 85721 (United States); Hurricane, O.; Remington, B. A.; Robey, H. F. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
2015-10-15
We report a scrupulous analysis of data in supernova experiments that are conducted at high power laser facilities in order to study core-collapse supernova SN1987A. Parameters of the experimental system are properly scaled to investigate the interaction of a blast-wave with helium-hydrogen interface, and the induced Rayleigh-Taylor instability and Rayleigh-Taylor mixing of the denser and lighter fluids with time-dependent acceleration. We analyze all available experimental images of the Rayleigh-Taylor flow in supernova experiments and measure delicate features of the interfacial dynamics. A new scaling is identified for calibration of experimental data to enable their accurate analysis and comparisons. By properly accounting for the imprint of the experimental conditions, the data set size and statistics are substantially increased. New theoretical solutions are reported to describe asymptotic dynamics of Rayleigh-Taylor flow with time-dependent acceleration by applying theoretical analysis that considers symmetries and momentum transport. Good qualitative and quantitative agreement is achieved of the experimental data with the theory and simulations. Our study indicates that in supernova experiments Rayleigh-Taylor flow is in the mixing regime, the interface amplitude contributes substantially to the characteristic length scale for energy dissipation; Rayleigh-Taylor mixing keeps order.
Wu, Dong; Qiao, B; Zhou, C T; Yan, X Q; Yu, M Y; He, X T
2014-01-01
It is shown that the transverse Rayleigh-Taylor-like (RT) instability in the hole boring radiation pressure acceleration can be suppressed by using elliptically polarized (EP) laser. A moderate ${J}\\times{B}$ heating of the EP laser will thermalize the local electrons, which leads to the transverse diffusion of ions, suppressing the short wavelength perturbations of RT instability. A proper condition of polarization ratio is obtained analytically for the given laser intensity and plasma density. The idea is confirmed by two dimensional Particle-in-Cell simulations, showing that the ion beam driven by the EP laser is more concentrated and intense compared with that of the circularly polarized laser.
邱孝明; 黄林; 简广德
2002-01-01
A magnetohydrodynamic (MHD) formulation is derived to investigate and compare the mitigation effects of both the sheared axial flow and finite Larmor radius (FLR) on the Rayleigh-Taylor (RT) instability in Z-pinch implosions. The sheared axial flow is introduced into MHD equations in a conventional way and the FLR effect into the equations via а/аt → -i(ω + ik2⊥ρi2Ωi), as proposed in our previous paper [Chin. Phys. Lett. 2002, 19:217] , where k2⊥ρ2i is referred to FLR effect from the general kinetic theory of magnetized plasma. Therefore the linearized continuity and momentum equations for the perturbed massdensity and velocity include both the sheared axial flow and the FLR effect. It is found that the effect of sheared axial flow with a lower peak velocity can mitigate RT instability in the whole wavenumber region and the effect of sheared axial flow with a higher one can mitigate RT instability only in the large wavenumber region (for normalized wavenumber κ＞ 2.4); The effect of FLR can mitigate RT instability in the whole wavenumber region and the mitigation effect is stronger than that of the sheared axial flow with a lower peak velocity in the almost whole wavenumber region.
Casner, A., E-mail: alexis.casner@cea.fr; Masse, L.; Liberatore, S.; Loiseau, P.; Masson-Laborde, P. E.; Jacquet, L. [CEA, DAM, DIF, F-91297 Arpajon (France); Martinez, D.; Moore, A. S.; Seugling, R.; Felker, S.; Haan, S. W.; Remington, B. A.; Smalyuk, V. A. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Farrell, M.; Giraldez, E.; Nikroo, A. [General Atomics, San Diego, California 92121 (United States)
2015-05-15
Academic tests in physical regimes not encountered in Inertial Confinement Fusion will help to build a better understanding of hydrodynamic instabilities and constitute the scientifically grounded validation complementary to fully integrated experiments. Under the National Ignition Facility (NIF) Discovery Science program, recent indirect drive experiments have been carried out to study the ablative Rayleigh-Taylor Instability (RTI) in transition from weakly nonlinear to highly nonlinear regime [A. Casner et al., Phys. Plasmas 19, 082708 (2012)]. In these experiments, a modulated package is accelerated by a 175 eV radiative temperature plateau created by a room temperature gas-filled platform irradiated by 60 NIF laser beams. The unique capabilities of the NIF are harnessed to accelerate this planar sample over much larger distances (≃1.4 mm) and longer time periods (≃12 ns) than previously achieved. This extended acceleration could eventually allow entering into a turbulent-like regime not precluded by the theory for the RTI at the ablation front. Simultaneous measurements of the foil trajectory and the subsequent RTI growth are performed and compared with radiative hydrodynamics simulations. We present RTI growth measurements for two-dimensional single-mode and broadband multimode modulations. The dependence of RTI growth on initial conditions and ablative stabilization is emphasized, and we demonstrate for the first time in indirect-drive a bubble-competition, bubble-merger regime for the RTI at ablation front.
Hillier, Andrew; Isobe, Hiroaki; Shibata, Kazunari [Kwasan and Hida Observatories, Kyoto University, Kyoto (Japan); Berger, Thomas [Lockheed Martin Solar and Astrophysics Laboratory, Palo Alto, CA (United States)
2012-09-10
The launch of the Hinode satellite has allowed high-resolution observations of supersonic bright downflows in quiescent prominences, known as prominence knots. We present observations in the Ca II H spectral line using the Solar Optical Telescope on board the Hinode satellite of a descending plasma knot of size {approx}900 km. The knot initially undergoes ballistic motion before undergoing impulsive accelerations at the same time as experiencing increases in intensity. We also present a subset of our three-dimensional magnetohydrodynamic simulations, performed to investigate the nonlinear stability of the Kippenhahn-Shlueter prominence model to the magnetic Rayleigh-Taylor instability in which interchange reconnection occurs. The interchange reconnection in the model breaks the force balance along the field lines which initiates the downflows. The downflows propagate with a downward fluid velocity of {approx}15 km s{sup -1} and a characteristic size of {approx}700 km. We conclude that the observed plasma blob and the simulated downflow are driven by the breaking of the force balance along the magnetic field as a result of a change in magnetic topology caused by reconnection of the magnetic field.
Liu, Wanhai; Yu, Changping; Jiang, Hongbin; Li, Xinliang
2017-02-01
Based on the harmonic analysis [Liu et al., Phys. Plasmas 22, 112112 (2015)], the analytical investigation on the harmonic evolution in Rayleigh-Taylor instability (RTI) at a spherical interface has been extended to the general case of arbitrary Atwood numbers by using the method of the formal perturbation up to the third order in a small parameter. Our results show that the radius of the initial interface [i.e., Bell-Plessett (BP) effect] dramatically influences the harmonic evolution for arbitrary Atwood numbers. When the initial radius approaches infinity compared against the initial perturbation wavelength, the amplitudes of the first four harmonics will recover those in planar RTI. The BP effect makes the amplitudes of the zeroth, second, and third harmonics increase faster for a larger Atwood number than smaller one. The BP effect reduces the third-order negative feedback to the fundamental mode for a smaller Atwood number, and strengthens it for a larger one. Hence, the BP effect helps the fundamental mode grow faster for a smaller Atwood number.
Dutta, Urmi; Baruah, Amiya; Mandal, Nibir
2016-09-01
In many geological systems, inversion of density stratification sets in Rayleigh-Taylor (RT) instabilities, leading to an ascent of relatively low-density materials through the high-density overburden in the form of diapirs. These diapirs often originate from dipping low-density layers. This study aims to show how the initial tilt of such source layers can control the ascent behaviour of diapirs initiated by RT instabilities. Using two-layer viscous models we produced RT instabilities in physical experiments, and investigated the effects of source-layer tilts (beta;). Our experiments suggest that these diapirs ascend with contrasting lateral spreading rates in the up and down slope directions, resulting in their axi-asymmetric geometry. However, their heads retain a circular outline on the horizontal top surface, where the upwelling axis is located away from their geometric centre in the upslope direction. In this paper, we present a series of experimental models to demonstrate the spectrum of axi-symmetric to -asymmetric geometrical transitions with increasing beta;. Our experiments also reveal that when beta; is large (>4°) the diapirs become unstable, resulting in a continuous migration of their stems in the upslope direction. Using the volume of fluid method we ran computational fluid dynamic (CFD) simulations to study the underlying hydrodynamics of axi-asymmetric diapiric growth. The CFD simulations show that beta; > 0° conditions develop stronger flow vortices on the downslope side of an ascending diapir, leading to a pressure difference between the up- and downslope flanks. Such a differential pressure causes the diapir head to spread at a faster rate in the tilt direction. An estimate of the asymmetric spreading rates is given as a function of beta;. Our present study provides a fundamental understanding of the hydrodynamic flow structure responsible for the asymmetric growth of RT instabilities on tilted source layers, as applicable to a wide range of
Rotating Rayleigh-Taylor turbulence
Boffetta, G.; Mazzino, A.; Musacchio, S.
2016-09-01
The turbulent Rayleigh-Taylor system in a rotating reference frame is investigated by direct numerical simulations within the Oberbeck-Boussinesq approximation. On the basis of theoretical arguments, supported by our simulations, we show that the Rossby number decreases in time, and therefore the Coriolis force becomes more important as the system evolves and produces many effects on Rayleigh-Taylor turbulence. We find that rotation reduces the intensity of turbulent velocity fluctuations and therefore the growth rate of the temperature mixing layer. Moreover, in the presence of rotation the conversion of potential energy into turbulent kinetic energy is found to be less effective, and the efficiency of the heat transfer is reduced. Finally, during the evolution of the mixing layer we observe the development of a cyclone-anticyclone asymmetry.
Parker, E. N.
1987-01-01
The dynamics of thermal shadows which develop in the convective zone of a star around an insulating obstacle such as a horizontal band in intense magnetic field are studied. The depth of the shadow on the cool side of the obstacle is found to depend largely on the width of the obstacle multiplied by the temperature gradient. Thermal shadows pressing fields up to 10,000 G downward against the bottom of the convective zone are produced by the broad bands of the azimuthal field in the sun's convective zone. In the third part, the time-dependent accumulation of heat beneath a thermal barrier simulating such a band in the lower convective zone of the sun is considered. The resulting Rayleigh-Taylor instability is shown to cause tongues of heated gas to penetrate upward through the field, providing the emerging magnetic fields that give rise to the activity of the sun.
Kulkarni, Akshay K
2008-01-01
We present results of 3D simulations of MHD instabilities at the accretion disk-magnetosphere boundary. The instability is Rayleigh-Taylor, and develops for a fairly broad range of accretion rates and stellar rotation rates and magnetic fields. It produces tall, thin tongues of plasma that penetrate the magnetosphere in the equatorial plane. The shape and number of the tongues changes with time on the inner-disk dynamical timescale. In contrast with funnel flows, which deposit matter mainly in the polar region, the tongues deposit matter much closer to the stellar equator. The instability appears for relatively small misalignment angles, $\\Theta\\lesssim30^\\circ$, between the star's rotation and magnetic axes, and is associated with higher accretion rates. The hot spots and light curves during accretion through instability are generally much more chaotic than during stable accretion. The unstable state of accretion has possible implications for quasi-periodic oscillations and intermittent pulsations from accre...
Schilling, Oleg
2016-11-01
Two-, three- and four-equation, single-velocity, multicomponent Reynolds-averaged Navier-Stokes (RANS) models, based on the turbulent kinetic energy dissipation rate or lengthscale, are used to simulate At = 0 . 5 Rayleigh-Taylor turbulent mixing with constant and complex accelerations. The constant acceleration case is inspired by the Cabot and Cook (2006) DNS, and the complex acceleration cases are inspired by the unstable/stable and unstable/neutral cases simulated using DNS (Livescu, Wei & Petersen 2011) and the unstable/stable/unstable case simulated using ILES (Ramaprabhu, Karkhanis & Lawrie 2013). The four-equation models couple equations for the mass flux a and negative density-specific volume correlation b to the K- ɛ or K- L equations, while the three-equation models use a two-fluid algebraic closure for b. The lengthscale-based models are also applied with no buoyancy production in the L equation to explore the consequences of neglecting this term. Predicted mixing widths, turbulence statistics, fields, and turbulent transport equation budgets are compared among these models to identify similarities and differences in the turbulence production, dissipation and diffusion physics represented by the closures used in these models. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Rayleigh-Taylor stabilization by material strength at Mbar pressures
Remington, Bruce; Park, Hye-Sook; Lorenz, Thomas; Cavallo, Robert; Pollaine, Stephen; Prisbrey, Shon; Rudd, Robert; Becker, Richard; Bernier, Joel
2009-11-01
We present experiments on the Rayleigh-Taylor (RT) instability in the plastic flow regime of solid-state vanadium (V) foils at 1 Mbar pressures and strain rates of 1.e6-1.e8 1/s, using a laser based, ramped-pressure acceleration technique. High pressure material strength causes strong stabilization of the RT instability at short wavelengths. Comparisons with 2D simulations utilizing models of high pressure strength show that the V strength increases by factors of 3-4 at peak pressure, compared to its ambient strength. An effective lattice viscosity of 400 poise would have a similar effect. [1] Constitutive models, and theoretical implications of these experiments will be discussed. [1] H.S. Park, B.A. Remington et al., submitted for publication (July, 2009).
Magneto-Rayleigh-Taylor growth and feedthrough in cylindrical liners
Weis, Matthew; Lau, Y. Y.; Gilgenbach, Ronald; Peterson, Kyle; Hess, Mark
2013-10-01
Cylindrical liner implosions in the MagLIF concept are susceptible to the magneto-Rayleigh-Taylor instability (MRT). The linearized ideal MHD equations are solved, including the presence of an axial magnetic field and the effects of sausage and kink modes. The eigenmode solution, using appropriate equilibrium profiles, allows an assessment of the local MRT growth rate and of the instantaneous feedthrough factor during the entire implosion process. Of particular interest will be the high convergence/stagnation phase, which is difficult to image experimentally. Strong axial magnetic fields can mitigate feedthrough and MRT growth, which may be useful at the fuel/liner interface during this phase of the MagLIF implosion. For the MRT growth rate and feedthrough factors, the LLNL code, HYDRA, is used to benchmark with the analytic theory, and with experiments on the Z-machine. This work was supported by DoE and NSF.
Collisional effects on Rayleigh-Taylor-induced magnetic fields
Manuel, M. J.-E. [University of Michigan, Ann Arbor, Michigan 48109 (United States); Flaig, M.; Plewa, T. [Florida State University, Tallahassee, Florida 32306 (United States); Li, C. K.; Séguin, F. H.; Frenje, J. A.; Casey, D. T.; Petrasso, R. D. [Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Hu, S. X.; Betti, R.; Hager, J.; Meyerhofer, D. D.; Smalyuk, V. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States)
2015-05-15
Magnetic-field generation from the Rayleigh-Taylor (RT) instability was predicted more than 30 years ago, though experimental measurements of this phenomenon have only occurred in the past few years. These pioneering observations demonstrated that collisional effects are important to B-field evolution. To produce fields of a measurable strength, high-intensity lasers irradiate solid targets to generate the nonaligned temperature and density gradients required for B-field generation. The ablation process naturally generates an unstable system where RT-induced magnetic fields form. Field strengths inferred from monoenergetic-proton radiographs indicate that in the ablation region diffusive effects caused by finite plasma resistivity are not negligible. Results from the first proof-of-existence experiments are reviewed and the role of collisional effects on B-field evolution is discussed in detail.
Anelastic Rayleigh-Taylor mixing layers
Schneider, N.; Gauthier, S.
2016-07-01
Anelastic Rayleigh-Taylor mixing layers for miscible fluids are investigated with a recently built model (Schneider and Gauthier 2015 J. Eng. Math. 92 55-71). Four Chebyshev-Fourier-Fourier direct numerical simulations are analyzed. They use different values for the compressibility parameters: Atwood number (the dimensionless difference of the heavy and light fluid densities) and stratification (accounts for the vertical variation of density due to gravity). For intermediate Atwood numbers and finite stratification, compressibility effects quickly occurs. As a result only nonlinear behaviours are reached. The influence of the compressibility parameters on the growth speed of the RTI is discussed. The 0.1—Atwood number/0.4—stratification configuration reaches a turbulent regime. This turbulent mixing layer is analyzed with statistical tools such as moments, PDFs, anisotropy indicators and spectra.
Stability of Rayleigh-Taylor Vortices in Dusty Plasma
MA Jun; CHEN Yin-Hua; GAN Bao-Xia; WANG Fei-Hu; WANG Dong
2006-01-01
@@ The evolution of Rayleigh-Taylor mode in dusty plasma with vortex-flow is investigated. Based on fluid theory and Bayly's method, we derive the coupling equations describing the Rayleigh-Taylor mode in the core of vortex,and research the evolution characteristics of the perturbation amplitude with time numerically. It is shown that the eccentric of vortex and the content of dust have considerable effects on the amplitude evolutions.
Very-high-growth-factor Planar Ablative Rayleigh Taylor Experiments
Bradley, D K; Braun, D G; Glendinning, S G; Edwards, M J; Milovich, J L; Sorce, C M; Collins, G W; Haan, S W; Page, R H
2006-10-30
The Rayleigh-Taylor (RT) instability is an important factor in bounding the performance envelope of ignition targets. This paper describes an experiment for ablative RT instability that for the first time achieves growth factors close to those expected to occur in ignition targets at the National Ignition Facility (NIF). The large growth allows small seed perturbations to be detected and can be used to place an upper bound on perturbation growth at the ablation front resulting from microstructure in the preferred Be ablator. The experiments were performed on the Omega laser using a halfraum 1.2 mm long by 2 mm diameter with a 75% laser entrance hole. The halfraum was filled with {approx} 1 atm of neopentane to delay gold plasma from closing the diagnostic line of sight down the axis of the halfraum. The ablator was mounted at the base of the halfraum, and was accelerated by a two stepped X-ray pulse consisting of an early time section {approx} 100 eV to emulate the NIF foot followed by an approximately constant {approx} 150 eV drive sustained over an additional 5-7ns. It is this long pulse duration and late time observation that distinguishes the present work from previous experiments, and is responsible for the large growth that is achieved. The growth of a 2D sinusoidal perturbation machined on the drive side of the ablator was measured using face-on radiography. The diagnostic view remained open until {approx} 11 ns with maximum growth factors measured to be {approx} 200. The trajectory of the ablator was measured using streaked backlit radiography. The design and analysis of the experiments is described, and implications for experiments on ignition target ablators are discussed.
Rayleigh-Taylor-Induced Electromagnetic Fields in Laser-Produced Plasmas
Manuel, Mario J.-E.
Spontaneous electromagnetic fields can be important to the dynamic evolution of a plasma by directing heat flow as well as providing additional pressures on the conducting fluids through the Lorentz force. Electromagnetic fields are predicted to affect fluid behavior during the core-collapse of supernovae through generation of fields due to hydrodynamic instabilities. In the coronae of stars, self-generated magnetic fields lead to filamentary structure in the hot plasma. Recent experiments by Gregori et al. investigated sources of protogalactic magnetic fields generated by laser-produced shock waves. In inertial confinement fusion experiments, self-generated electromagnetic fields can also play a role and have recently become of great interest to the community. Present day laser facilities provide a unique opportunity to study spontaneous field-generation in these extreme environments under controlled conditions. Instability-induced electromagnetic fields were investigated using a novel monoenergetic-proton radiography system. Fusion protons generated by an 'exploding-pusher' implosion were used to probe laser-irradiated plastic foils with various preimposed surface perturbations. Imaging protons are sensitive to electromagnetic fields and density modulations in the plasma through the Lorentz force and Coulomb collisions, respectively. Corresponding x-ray radiographs of these targets provided mass density distributions and Coulomb effects on protons were assessed using a Monte Carlo code written using the Geant4 framework. Proton fluence distributions were recorded on CR-39 detectors and Fourier analyzed to infer path-integrated field strengths. Rayleigh-Taylor (RT) growth of preimposed surface perturbations generated magnetic fields by the RT-induced Biermann battery and were measured for the first time. Good data were obtained during linear growth and when compared to ideal calculations, demonstrated that field diffusion near the source played an important role
3-D nonlinear evolution of MHD instabilities
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.
Nonlinear diffusion model for Rayleigh-Taylor mixing.
Boffetta, G; De Lillo, F; Musacchio, S
2010-01-22
The complex evolution of turbulent mixing in Rayleigh-Taylor convection is studied in terms of eddy diffusivity models for the mean temperature profile. It is found that a nonlinear model, derived within the general framework of Prandtl mixing theory, reproduces accurately the evolution of turbulent profiles obtained from numerical simulations. Our model allows us to give very precise predictions for the turbulent heat flux and for the Nusselt number in the ultimate state regime of thermal convection.
Nonlinear diffusion model for Rayleigh-Taylor mixing
Boffetta, G; Musacchio, S
2010-01-01
The complex evolution of turbulent mixing in Rayleigh-Taylor convection is studied in terms of eddy diffusiviy models for the mean temperature profile. It is found that a non-linear model, derived within the general framework of Prandtl mixing theory, reproduces accurately the evolution of turbulent profiles obtained from numerical simulations. Our model allows to give very precise predictions for the turbulent heat flux and for the Nusselt number in the ultimate state regime of thermal convection.
Ablation Front Rayleigh-Taylor Growth Experiments in Spherically Convergent Geometry
Glendinning, S.G.; Cherfils, C.; Colvin, J.; Divol, L.; Galmiche, D.; Haan, S.; Marinak, M.M.; Remington, B.A.; Richard, A.L.; Wallace, R.
1999-11-03
Experiments were performed on the Nova laser, using indirectly driven capsules mounted in cylindrical gold hohlraums, to measure the Rayleigh-Taylor growth at the ablation front by time-resolved radiography. Modulations were preformed on the surface of Ge-doped plastic capsules. With initial modulations of 4 {micro}m, growth factors of about 6 in optical depth were seen, in agreement with simulations using the radiation hydrocode FCI2. With initial modulations of 1 {micro}m, growth factors of about 100-150 in optical depth were seen. The Rayleigh-Taylor (RT) instability at the ablation front in an inertial confinement fusion capsule has been the subject of considerable investigation. Much of this research has been concentrated on planar experiments, in which RT growth is inferred from radiography. The evolution is somewhat different in a converging geometry; the spatial wavelength decreases (affecting the onset of nonlinear saturation), and the shell thickens and compresses rather than decompressing as in a planar geometry. In a cylindrically convergent geometry, the latter effect is proportional to the radius, while in spherically convergent geometry, the latter effect is proportional to the radius squared. Experiments were performed on the Nova and Omega lasers in cylindrical geometry (using both direct and indirect drive) and have been performed in spherical geometry using direct drive.
Lecoanet, Daniel; Quataert, Eliot
2012-01-01
We study the effects of anisotropic thermal conduction along magnetic field lines on an accelerated contact discontinuity in a weakly collisional plasma. We first perform a linear stability analysis similar to that used to derive the Rayleigh-Taylor instability (RTI) dispersion relation. We find that anisotropic conduction is only important for compressible modes, as incompressible modes are isothermal. Modes grow faster in the presence of anisotropic conduction, but growth rates do not change by more than a factor of order unity. We next run fully non-linear numerical simulations of a contact discontinuity with anisotropic conduction. The non-linear evolution can be thought of as a superposition of three physical effects: temperature diffusion due to vertical conduction, the RTI, and the heat flux driven buoyancy instability (HBI). In simulations with RTI-stable contact discontinuities, the temperature discontinuity spreads due to vertical heat conduction. This occurs even for initially horizontal magnetic f...
2D HYDRA Calculations of Magneto-Rayleigh-Taylor Growth and Feedthrough in Cylindrical Liners
Weis, Matthew; Zhang, Peng; Lau, Y. Y.; Gilgenbach, Ronald; Peterson, Kyle; Hess, Mark
2014-10-01
Cylindrical liner implosions are susceptible to the magneto-Rayleigh-Taylor instability (MRT), along with the azimuthal current-carrying modes (sausage, kink, etc). ``Feedthrough'' of these instabilities has a strong influence on the integrity of the liner/fuel interface in the magnetized liner inertial fusion concept (MagLIF). The linearized ideal MHD equations can be solved to quantify these effects, including the presence of an effective gravity and an axial magnetic field. We investigate the potential of this field to mitigate feedthrough, due to MRT growth from various initial surface finishes (seeded, rough), throughout the implosion using our analytic results and the LLNL code, HYDRA. We will present both low and high convergence cases. Lastly, we illustrate the effect shock compression can have on feedthrough in seeded liners for various fill gases (cold and pre-heated) and magnetic field configurations. M. R. Weis was supported by the Sandia National Laboratories.
A generalised Rayleigh-Taylor condition for the Muskat problem
Escher, Joachim; Matioc, Bogdan-Vasile
2010-01-01
In this paper we consider the evolution of two fluid phases in a porous medium. The fluids are separated from each other and also the wetting phase from air by interfaces which evolve in time. We reduce the problem to an abstract evolution equation. A generalised Rayleigh-Taylor condition characterizes the parabolicity regime of the problem and allows us to establish a general well-posedness result and to study stability properties of flat steady-states. When considering surface tension effects at the interface between the fluids and if the more dense fluid lies above, we find bifurcating finger-shaped equilibria which are all unstable.
Measurements of Molecular Mixing in a High Schmidt Number Rayleigh-Taylor Mixing Layer
Mueschke, N J; Schilling, O; Youngs, D L; Andrews, M
2007-12-03
Rayleigh?Taylor instability-induced mixing are discussed.
Qualitative and quantitative features of Rayleigh-Taylor mixing dynamics
Ramaprabhu, Praveen; Karkhanis, Varad; Lawrie, Andrew; Bhowmick, Aklant; Abarzhi, Snezhana; RTI Collaboration
2015-11-01
We consider dynamics of Rayleigh-Taylor (RT) flow in a large aspect ratio three-dimensional domain with square symmetry in the plane for fluids with contrasting densities. In order to quantify the interface evolution from a small amplitude single-mode initial perturbation to advanced stage of RT mixing, we apply numerical simulations using the MOBILE code, theoretical analyses, including group theory and momentum model, as well as parameters describing the interplay between acceleration and turbulence. We find: In RT flow, the fluid motion is intense near the interface and is negligible far from the interface. At late times the growth rates of RT bubbles and spikes may increase without a corresponding increase of length-scales in the direction normal to acceleration. The parameters describing the interplay between acceleration and turbulence in RT mixing are shown to scale well with the flow Reynolds number and Froude number.
Mueschke, N J; Andrews, M J; Schilling, O
2006-03-24
The initial multi-mode interfacial velocity and density perturbations present at the onset of a small Atwood number, incompressible, miscible, Rayleigh-Taylor instability-driven mixing layer have been quantified using a combination of experimental techniques. The streamwise interfacial and spanwise interfacial perturbations were measured using high-resolution thermocouples and planar laser-induced fluorescence (PLIF), respectively. The initial multi-mode streamwise velocity perturbations at the two-fluid density interface were measured using particle-image velocimetry (PIV). It was found that the measured initial conditions describe an initially anisotropic state, in which the perturbations in the streamwise and spanwise directions are independent of one another. The evolution of various fluctuating velocity and density statistics, together with velocity and density variance spectra, were measured using PIV and high-resolution thermocouple data. The evolution of the velocity and density statistics is used to investigate the early-time evolution and the onset of strongly-nonlinear, transitional dynamics within the mixing layer. The early-time evolution of the density and vertical velocity variance spectra indicate that velocity fluctuations are the dominant mechanism driving the instability development. The implications of the present experimental measurements on the initialization of Reynolds-averaged turbulent transport and mixing models and of direct and large-eddy simulations of Rayleigh-Taylor instability-induced turbulence are discussed.
Mueschke, N J; Andrews, M J; Schilling, O
2005-09-26
The initial multi-mode interfacial velocity and density perturbations present at the onset of a small Atwood number, incompressible, miscible, Rayleigh-Taylor instability-driven mixing layer have been quantified using a combination of experimental techniques. The streamwise interfacial and spanwise interfacial perturbations were measured using high-resolution thermocouples and planar laser-induced fluorescence (PLIF), respectively. The initial multi-mode streamwise velocity perturbations at the two-fluid density interface were measured using particle-image velocimetry (PIV). It was found that the measured initial conditions describe an initially anisotropic state, in which the perturbations in the streamwise and spanwise directions are independent of one another. The evolution of various fluctuating velocity and density statistics, together with velocity and density variance spectra, were measured using PIV and high-resolution thermocouple data. The evolution of the velocity and density statistics is used to investigate the early-time evolution and the onset of strongly-nonlinear, transitional dynamics within the mixing layer. The early-time evolution of the density and vertical velocity variance spectra indicate that velocity fluctuations are the dominant mechanism driving the instability development. The implications of the present experimental measurements on the initialization of Reynolds-averaged turbulent transport and mixing models and of direct and large-eddy simulations of Rayleigh-Taylor instability-induced turbulence are discussed.
Ripesi, P; Schifano, S F; Tripiccione, R
2014-01-01
We study the turbulent evolution originated from a system subjected to a Rayleigh-Taylor instability with a double density at high resolution in a 2 dimensional geometry using a highly optimized thermal Lattice Boltzmann code for GPUs. The novelty of our investigation stems from the initial condition, given by the superposition of three layers with three different densities, leading to the development of two Rayleigh-Taylor fronts that expand upward and downward and collide in the middle of the cell. By using high resolution numerical data we highlight the effects induced by the collision of the two turbulent fronts in the long time asymptotic regime. We also provide details on the optimized Lattice-Boltzmann code that we have run on a cluster of GPUs
Planar and cylindrical Rayleigh-Taylor experiments on Nova (HEP2)
Remington, B.A.; Weber, S.V.; Marinak, M.M. [and others
1996-06-01
A high-density fluid on top of a low-density fluid is Rayleigh-Taylor (RT) unstable. Driven by gravity, random perturbations at the interface between the two fluids will grow: fingers ({open_quotes}spikes{close_quotes}) of the heavier fluid will poke through the lighter fluid, and bubbles of the lighter fluid will rise into the heavier fluid. The RT instability and its shock-driven analog, the Richtmyer-Meshkov (RM) instability, have been a focus of research in inertial confinement fusion (ICF) for some time. In ICF, the driver - laser light, x rays, or ions - heats the outer layer of the capsule wall, causing it to ionize and expand rapidly. The result is a low-density ablated plasma accelerating the high-density capsule wall ({open_quotes}Pusher{close_quotes}). The ablation front is RT unstable, and outer-surface imperfections grow. This growth can seed perturbations at the pusher inner wall, which in turn become RT unstable during deceleration and stagnation. Ultimately, pusher material can mix into the fuel, degrading performance.
Application of monotone integrated large eddy simulation to Rayleigh-Taylor mixing.
Youngs, David L
2009-07-28
Rayleigh-Taylor (RT) instability occurs when a dense fluid rests on top of a light fluid in a gravitational field. It also occurs in an equivalent situation (in the absence of gravity) when an interface between fluids of different density is accelerated by a pressure gradient, e.g. in inertial confinement fusion implosions. Engineering models (Reynolds-averaged Navier-Stokes models) are needed to represent the effect of mixing in complex applications. However, large eddy simulation (LES) currently makes an essential contribution to understanding the mixing process and calibration or validation of the engineering models. In this paper, three cases are used to illustrate the current role of LES: (i) mixing at a plane boundary, (ii) break-up of a layer of dense fluid due to RT instability, and (iii) mixing in a simple spherical implosion. A monotone integrated LES approach is preferred because of the need to treat discontinuities in the flow, i.e. the initial density discontinuities or shock waves. Of particular interest is the influence of initial conditions and how this needs to be allowed for in engineering modelling. It is argued that loss of memory of the initial conditions is unlikely to occur in practical applications.
Adjoint-based approach to Enhancing Mixing in Rayleigh-Taylor Turbulence
Kord, Ali; Capecelatro, Jesse
2016-11-01
A recently developed adjoint method for multi-component compressible flow is used to measure sensitivity of the mixing rate to initial perturbations in Rayleigh-Taylor (RT) turbulence. Direct numerical simulations (DNS) of RT instabilities are performed at moderate Reynolds numbers. The DNS are used to provide an initial prediction, and the corresponding space-time discrete-exact adjoint provides a sensitivity gradient for a specific quantity of interest (QoI). In this work, a QoI is defined based on the time-integrated scalar field to quantify the mixing rate. Therefore, the adjoint solution is used to measure sensitivity of this QoI to a set of initial perturbations, and inform a gradient-based line search to optimize mixing. We first demonstrate the adjoint approach in the linear regime and compare the optimized initial conditions to the expected values from linear stability analysis. The adjoint method is then used in the high Reynolds number limit where theory is no longer valid. Finally, chaos is known to contaminate the accuracy of the adjoint gradient in turbulent flows when integrated over long time horizons. We assess the influence of chaos on the accuracy of the adjoint gradient to guide the work of future studies on adjoint-based sensitivity of turbulent mixing. PhD Student, Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI.
Understanding the impact of initial condition on low Atwood number Rayleigh-Taylor driven flows
Kuchibhatla, Sarat Chandra; Ranjan, Devesh
2012-11-01
Experimental investigation of the effects of initial conditions on Rayleigh-Taylor instability was performed using the Water Channel facility at Texas A&M University. Hot and cold water (with a temperature difference of ~7-8 degrees C) selected as working fluids were unstably stratified using a splitter plate resulting in a low Atwood number of ~0.0015. Using a servo controlled flapper system the effect of initial conditions is studied using different diagnostics such as optical imaging, thermocouples and hot-wire anemometry. A parametric study comprising of up to 10 modes of the initial condition was performed by varying the number of modes as well as modal composition (i . e . ratio of wavenumbers and phase differences). Variation of density, temperature and velocity field in the linear and non-linear stages of RT growth was recorded and analyzed. At non-dimensional time, t* = t (At g /H)0.5= 1.3, where t is the time, H is the width of the Channel, and g is the acceleration due to gravity, power spectra of the non-dimensional density showed fine-scale components that are dependent upon the initial condition. Plots of scalar dissipation and mixing rate indicate greater dissipation rate at early times that tends to asymptote to the order of kinematic viscosity at late times.
Rayleigh Taylor growth at an embedded interface driven by a radiative shock
Huntington, Channing
2016-10-01
Radiative shocks are those where the radiation generated by the shock influences the hydrodynamics of the matter in the system. Radiative shocks are common in astrophysics, including during type II supernovae, and have also been observed in the rebound phase of a compressed inertial confinement fusion (ICF) capsule. It is predicted that the radiative heating serves to stabilize hydrodynamic instabilities in these systems, but studying the effect is challenging. Only in recent experiments at the National Ignition Facility has the energy been available to drive a radiative shock across a planar, Rayleigh-Taylor unstable interface in solid-density materials. Because the generation of radiation at the shock front is a strong function of shock velocity (v8) , the RT growth rates in the presence of fast and slow shockas were directly compared. We observe reduced RT spike development when the driving shock is expected to be radiative. Both low drive (225 eV) hydrodynamic RT growth and high drive (325 eV), radiatively-stabilized growth rates are in good agreement with 2D models. This NIF Discovery Science result has important implications for our understanding of astrophysical radiative shocks, as well as the dynamics of ICF capsules. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Investigating iron material strength up to 1 Mbar using Rayleigh-Taylor growth measurements
Huntington, C. M.; Belof, J. L.; Blobaum, K. J. M.; Cavallo, R. M.; Kostinski, N. B.; Maddox, B. R.; Park, H.-S.; Plechaty, C.; Prisbrey, S. T.; Rudd, R.; Swift, D. W.; Wallace, R. J.; Weber, S. V.; Wehrenberg, C.; Wilson, M. J.; Remington, B. A.
2017-01-01
The solid-solid phase transition between the bcc (α) and hcp (ɛ) lattice structures in iron is known to occur as the material is compressed. When kept below its melting point, an effective increase in the macroscopic strength of the material accompanies this phase transition. Understanding the material strength of iron throughout the deformation process presents a significant computational challenge, but is important for improving models of planetary structure, including interpretation of seismic measurements taken through our own Earth's core. To explore the strength of iron at high pressures and strain rates, we have developed the IronRT campaign at the OMEGA laser [1]. This laser-driven platform produces pressure greater than 1 Mbar on a thin Fe disk with a sinusoidal ripple pattern imposed on its face. These ripples seed the Rayleigh-Taylor (RT) instability, the growth of which is suppressed by the material strength of the sample. The amplitude of the ripples is diagnosed with high-energy x-ray radiography, and the measured growth is compared to simulations performed with different strength models. By matching the simulations to the low level of growth measured, we infer an average flow stress of greater than 40 GPa over the course of the experiment. This value is in agreement with other dynamic iron strength experiments at pressures greater than 1 Mbar [2].
Beryllium liner z-pinches for magneto-Rayleigh-Taylor studies on Z
McBride, R. D.; Slutz, S. A.; Sinars, D. B.; Lemke, R. W.; Martin, M. R.; Jennings, C. A.; Cuneo, M. E.; Herrmann, M. C.; Blue, B. E.
2011-10-01
Magnetized Liner Inertial Fusion (MagLIF) [S. A. Slutz, et al., Phys. Plasmas 17, 056303 (2010)] is a promising new concept for achieving >100 kJ of fusion yield on Z. The greatest threat to this concept is the magneto-Rayleigh-Taylor (MRT) instability. Thus experimental campaigns have been initiated to study MRT growth in fast imploding (<100 ns) cylindrical liners. This talk will present results from experiments that used 6.151-keV radiography to study the implosions of unperturbed (surface roughness only) beryllium (Be) liners. The high transmission efficiency of 6.151-keV photons through Be allowed us to obtain radiographs with finite transmission throughout the radial extent of the imploding liners. The data from these experiments will be shown and compared to simulation data from several magneto-hydrodynamic codes. These data are allowing us to evaluate the integrity of the inside (fuel-confining) surface of the imploding liner as it approaches stagnation. Sandia is a multi-program laboratory operated by Sandia Corp, a Lockheed-Martin company, for the US Dept of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.
Study of Rayleigh-Taylor growth in directly driven cryogenic-deuterium targets
Hager, J. D.; Hu, S. X.; Knauer, J. P.; Meyerhofer, D. D.; Sangster, T. C. [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623-1299 (United States); Smalyuk, V. A. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
2012-07-15
Direct-drive, Rayleigh-Taylor growth experiments in liquid deuterium (D{sub 2}) were performed on the OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] using planar cryogenic targets at a laser intensity of {approx}4 Multiplication-Sign 10{sup 14} W/cm{sup 2}. These are the first Rayleigh-Taylor measurements in deuterium at conditions relevant to inertial confinement fusion using a mass preimposed initial modulation. The measured modulation optical depths are in agreement with the 2D hydrodynamics code DRACO using flux-limited local thermal transport, providing an important step in the experimental validation of simulations for direct-drive ignition.
3D instability of liquid films and rivulets
Alekseenko Sergey
2016-01-01
Full Text Available This article presents the results of experimental and theoretical study of 3D instability of waves in liquid films and rivulets, falling down a vertical plate. The method of laser induced fluorescence was used to obtain instant shapes of three dimensional waves in a liquid films and rivulets and to investigate the regularities of formation of 3D wave patterns. In particular, during 2D-3D wave transition in the film flow, we observed a strong transverse redistribution of liquid leading to the formation of rivulets on the surface of isothermal liquid film, which is a phenomenon not described previously. The results of simulation of 2 D and 3D regular waves in the single rivulet are compared with the authors’ previous experimental data.
Experimental, Numerical and Analytical Studies of the MHD-driven plasma jet, instabilities and waves
Zhai, Xiang
This thesis describes a series of experimental, numerical, and analytical studies involving the Caltech magnetohydrodynamically (MHD)-driven plasma jet experiment. The plasma jet is created via a capacitor discharge that powers a magnetized coaxial planar electrodes system. The jet is collimated and accelerated by the MHD forces. We present three-dimensional ideal MHD finite-volume simulations of the plasma jet experiment using an astrophysical magnetic tower as the baseline model. A compact magnetic energy/helicity injection is exploited in the simulation analogous to both the experiment and to astrophysical situations. Detailed analysis provides a comprehensive description of the interplay of magnetic force, pressure, and flow effects. We delineate both the jet structure and the transition process that converts the injected magnetic energy to other forms. When the experimental jet is sufficiently long, it undergoes a global kink instability and then a secondary local Rayleigh-Taylor instability caused by lateral acceleration of the kink instability. We present an MHD theory of the Rayleigh-Taylor instability on the cylindrical surface of a plasma flux rope in the presence of a lateral external gravity. The Rayleigh-Taylor instability is found to couple to the classic current-driven instability, resulting in a new type of hybrid instability. The coupled instability, produced by combination of helical magnetic field, curvature of the cylindrical geometry, and lateral gravity, is fundamentally different from the classic magnetic Rayleigh-Taylor instability occurring at a two-dimensional planar interface. In the experiment, this instability cascade from macro-scale to micro-scale eventually leads to the failure of MHD. When the Rayleigh-Taylor instability becomes nonlinear, it compresses and pinches the plasma jet to a scale smaller than the ion skin depth and triggers a fast magnetic reconnection. We built a specially designed high-speed 3D magnetic probe and
Effect of noise on Rayleigh-Taylor mixing with time-dependent acceleration
Swisher, Nora; Pandian, Arun; Abarzhi, Snezhana
2016-11-01
We perform a detailed stochastic study of Rayleigh-Taylor (RT) mixing with time-dependent acceleration. A set of nonlinear stochastic differential equations with multiplicative noise is derived on the basis of momentum model and group theory analysis. A broad range of parameters is investigated, and self-similar asymptotic solutions are found. The existence is shown of two sub-regimes of RT mixing dynamics - the acceleration-driven and the dissipation-driven mixing. In each sub-regime, statistic properties of the solutions are investigated, and dynamic invariants are found. Transition between the sub-regimes is studied. The work is supported by the US National Science Foundation.
Fiksel, G.; Hu, S. X.; Goncharov, V. A.; Meyerhofer, D. D.; Sangster, T. C.; Yaakobi, B.; Bonino, M. J.; Jungquist, R. [Laboratory for Laser Energetics, University of Rochester, 250 East River Rd., Rochester, New York 14623-1299 (United States); Smalyuk, V. A. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)
2012-06-15
The effect of medium-Z doping of plastic ablators on laser imprinting and Rayleigh-Taylor (RT) instability growth was studied using spherical direct-drive implosions on the OMEGA Laser System [T. R. Boehly et al., Opt. Commun. 133, 495 (1977)]. The targets were spherical plastic (CH) shells, with an outer diameter of 860 {mu}m and a thickness of 22 {mu}m, volume doped with a varied concentration of Si (4.3% and 7.4%) and Ge (3.9%). The targets were imploded with 48 beams with a low-adiabat, triple-picket laser shape pulse with a peak intensity of 4 Multiplication-Sign 10{sup 14}W/cm{sup 2}, and a pulse duration of 2.5 ns. The shells were x-ray radiographed through a 400 -{mu}m opening in the side of the target. The results show that volumetric impurity doping strongly reduces the shell density modulation and the instability growth rate. The amplitude of the initial imprint is reduced by a factor of 2.5 {+-} 0.5 for CH[4.3% Si] targets and by a factor of 3 {+-} 0.5 for CH[7.4% Si] and CH[3.9% Ge] targets. At the end of the acceleration phase, the reduction factor becomes 3 {+-} 0.5 and 5 {+-} 0.5, correspondingly. The RT instability growth rate in doped targets is reduced by a factor of 1.5 compared to undoped ones. Simulations using the two-dimensional, radiation-hydrodynamics code draco show good agreement with the measurements.
Fiksel, G.; Hu, S. X.; Epstein, R.; Goncharov, V. N.; Meyerhofer, D. D.; Sangster, T. C.; Yaakobi, B.; Bonino, M. J.; Jungquist, R. K.; Smalyuk, V. A.
2012-10-01
The effect of medium-Z doping of plastic ablators on laser imprinting and Rayleigh-- Taylor (RT) instability growth was studied using spherical direct-drive implosions on the OMEGA Laser System. The targets were spherical plastic (CH) shells, with an outer diameter of 860 μm and a thickness of 22 μm, doped with a varied concentration of Si (4.3% and 7.4%) and Ge (3.9%). The targets were imploded with 48 beams with a low-adiabat, triple-picket laser shape pulse with a peak intensity of 4 x 10^14 W/cm^2 and a pulse duration of 2.5 ns. The shells were x-ray radiographed through a 400-μm opening in the side of the target. The results show that impurity doping strongly reduces the shell-density modulation and the instability growth rate. The amplitude of the initial imprint is reduced by a factor of 2.5±0.5 for CH[4.3% Si] targets and a factor of 3±0.5 for CH[7.4% Si] and CH[3.9% Ge] targets. At the end of the acceleration phase, the reduction factor becomes 3±0.5 and 5±0.5, correspondingly. The RT instability growth rate in doped targets is reduced by a factor of 1.5 compared to undoped ones. Simulations using the 2-D radiation--hydrodynamics code DRACO show good agreement with the measurements. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302.
Fiksel, G.; Hu, S. X.; Goncharov, V. A.; Meyerhofer, D. D.; Sangster, T. C.; Smalyuk, V. A.; Yaakobi, B.; Bonino, M. J.; Jungquist, R.
2012-06-01
The effect of medium-Z doping of plastic ablators on laser imprinting and Rayleigh-Taylor (RT) instability growth was studied using spherical direct-drive implosions on the OMEGA Laser System [T. R. Boehly et al., Opt. Commun. 133, 495 (1977)]. The targets were spherical plastic (CH) shells, with an outer diameter of 860 μm and a thickness of 22 μm, volume doped with a varied concentration of Si (4.3% and 7.4%) and Ge (3.9%). The targets were imploded with 48 beams with a low-adiabat, triple-picket laser shape pulse with a peak intensity of 4×1014W/cm2, and a pulse duration of 2.5 ns. The shells were x-ray radiographed through a 400 -μm opening in the side of the target. The results show that volumetric impurity doping strongly reduces the shell density modulation and the instability growth rate. The amplitude of the initial imprint is reduced by a factor of 2.5 ± 0.5 for CH[4.3% Si] targets and by a factor of 3 ± 0.5 for CH[7.4% Si] and CH[3.9% Ge] targets. At the end of the acceleration phase, the reduction factor becomes 3 ± 0.5 and 5 ± 0.5, correspondingly. The RT instability growth rate in doped targets is reduced by a factor of 1.5 compared to undoped ones. Simulations using the two-dimensional, radiation-hydrodynamics code draco show good agreement with the measurements.
Numerical investigation of 3D effects on a 2D-dominated shocked mixing layer
Reese, Daniel; Weber, Christopher
2016-11-01
A nominally two-dimensional interface, unstable to the Rayleigh-Taylor or Richtmyer-Meshkov instability, will become three-dimensional at high Reynolds numbers due to the growth of background noise and 3D effects like vortex stretching. This three-dimensionality changes macroscopic features, such as the perturbation growth rate and mixing, as it enhances turbulent dissipation. In this study, a 2D perturbation with small-scale, 3D fluctuations is modeled using the hydrodynamics code Miranda. A Mach 1.95 shockwave accelerates a helium-over-SF6 interface, similar to the experiments of Motl et al. ["Experimental validation of a Richtmyer-Meshkov scaling law over large density ratio and shock strength ranges," Phys. Fluids 21(12), 126102 (2009)], to explore the regime where a 2D dominated flow will experience 3D effects. We report on the structure, growth, and mixing of the post-shocked interface in 2D and 3D.
Magneto-Rayleigh-Taylor, Sausage And Kink Mode In Cylindrical Liners
Lau, Y. Y.; Zhang, Peng; Weis, Matthew; Gilgenbach, Ronald; Hess, Mark; Peterson, Kyle
2014-10-01
This paper analyzes the coupling of magneto-Rayleigh-Taylor (MRT), sausage (azimuthal mode number m = 0) and kink mode (m = 1) in an imploding cylindrical liner, using ideal MHD. A uniform axial magnetic field of arbitrary value is included in each region: liner, its interior, and its exterior. The dispersion relation, the feedthrough factor, and the temporal evolution of perturbations were solved exactly, for arbitrary values of g (= gravity), k (= axial wavenumber), m, aspect ratio, and equilibrium quantities in each region. For small k, a positive g (inward radial acceleration in the lab frame) tends to stabilize the sausage mode, but destabilize the kink mode. For large k, a positive g destabilizes both the kink and sausage mode. This analysis might shed lights into some puzzling features in Harris' classic paper, and in the recent cylindrical liner experiments on MRT. M. R. Weis was supported by the Sandia National Laboratories.
Experimental investigation of late time Rayleigh-Taylor mixing at high Atwood number
Suchandra, Prasoon; Mikhaeil, Mark; Ranjan, Devesh
2016-11-01
Dynamics of late time, high Reynolds number (Re >20000) Rayleigh-Taylor (RT) mixing is studied using statistically steady experiments performed in a multi-layer gas tunnel. The density ratio of air and air-Helium mixture used in the present experiment results in an Atwood number 0.73. Three types of diagnostics - back-lit visualization, hot-wire anemometry and stereo particle image velocimetry (S-PIV) - are employed to obtain mixing width, velocity and density fields, with S-PIV employed for the first time for such experimental conditions. Velocity and density statistics, and their correlations (u', v', w',ρ' ,ρ'v') are presented. Calculations of probability density functions (p.d.f.s) and energy spectra are made to provide further insight into the flow physics. Energy budget of the flow is also discussed.
Retarding viscous Rayleigh-Taylor mixing by an optimized additional mode
Xie, C. Y.; Tao, J. J.; Sun, Z. L.; Li, J.
2017-02-01
The Rayleigh-Taylor (RT) mixing induced by random interface disturbances between two incompressible viscous fluids is simulated numerically. The ensemble averaged spike velocity is found to be remarkably retarded when the random interface disturbances are superimposed with an optimized additional mode. The mode's wavenumber is selected to be large enough to avoid enhancing the dominance of long-wavelength modes, but not so large that its saturated spike and bubble velocities are too small to stimulate a growing effective density-gradient layer suppressing the long-wavelength modes. Such an optimized suppressing mode is expected to be found in the RT mixing including other diffusion processes, e.g., concentration diffusion and thermal diffusion.
Statistically steady measurements of Rayleigh-Taylor mixing in a gas channel
Banerjee, Arindam
A novel gas channel experiment was constructed to study the development of high Atwood number Rayleigh-Taylor mixing. Two gas streams, one containing air and the other containing helium-air mixture, flow parallel to each other separated by a thin splitter plate. The streams meet at the end of a splitter plate leading to the formation of an unstable interface and of buoyancy driven mixing. This buoyancy driven mixing experiment allows for long data collection times, short transients and was statistically steady. The facility was designed to be capable of large Atwood number studies of At ˜ 0.75. We describe work to measure the self similar evolution of mixing at density differences corresponding to 0.035 hot-wire anemometer, and high resolution digital image analysis. The hot-wire probe gives velocity, density and velocity-density statistics of the mixing layer. Two different multi-position single-wire techniques were used to measure the velocity fluctuations in three mutually perpendicular directions. Analysis of the measured data was used to explain the mixing as it develops to a self-similar regime in this flow. These measurements are to our knowledge, the first use of hot-wire anemometry in the Rayleigh-Taylor community. Since the measurement involved extensive calibration of the probes in a binary gas mixture of air and helium, a new convective heat transfer correlation was formulated to account for variable-density low Reynolds number flows past a heated cylinder. In addition to the hot-wire measurements, a digital image analysis procedure was used to characterize various properties of the flow and also to validate the hot-wire measurements. A test of statistical convergence was performed and the study revealed that the statistical convergence was a direct consequence of the number of different large three-dimensional structures that were averaged over the duration of the run.
Matsumoto, Y.; Seki, K.
2006-12-01
An appearance of cold and dense plasma at the geosynchronous orbit is one of the characteristic natures after a prolonged northward IMF duration. This cold dense material can contribute to the enhancement of the ring current density, which results a further declination of Dst. Therefore investigating the origin, path and fate of the cold dense plasma is important to understand how it preconditions the magnetosphere during a quiet interval before storm [Borovsky and Steinberg, 2006]. Observational evidences have shown that the cold dense material builds up during the northward IMF intervals in the flanks of the magnetosphere [e.g., Wing and Newell, 2002] which is referred to as the low latitude boundary layer (LLBL). The entry process of the solar wind plasma into the magnetosphere during the northward IMF conditions has been controversial in contrast to the Dungey's reconnection model for the southward IMF cases. The major candidate processes are the double lobe reconnection model [Song et al., 1999], in which newly closed magnetic field lines on the dayside magnetopause capture the solar wind plasma, and the turbulent transport by the Kelvin-Helmholtz instability (KHI) driven by the fast solar wind flow. We have studied the solar wind entry process by the KHI. Matsumoto and Hoshino [2004, 2006] showed by 2- D MHD and full particle simulation studies that the strong flow turbulence is a natural consequence of the nonlinear development of the KHI through the secondary Rayleigh-Taylor instability, if there is a large density difference between the two media. The mechanism is fundamentally two-dimensional and therefore we term it the 2-D secondary instability. They also showed that the turbulent development greatly contributes to the solar wind plasma transport deep into the magnetosphere. Based on the previous 2-D studies, the 3-D nonlinear evolution of the KHI is studied by performing MHD simulation. Starting with a uniform background field configuration and a
Strong electron-scale instability in relativistic shear flows
Alves, Eduardo Paulo; Grismayer, Thomas; Fonseca, Ricardo; Silva, Luis
2013-10-01
Collisionless shear-driven plasma instabilities have recently been shown to be capable of generating strong and large-scale magnetic fields and may therefore play an important role in relativistic astrophysical outflows. We present a new collisionless shear-driven plasma instability, which operates in the plane transverse to the Kelvin Helmholtz instability (KHI). We develop the linear stability analysis of electromagnetic modes in the transverse plane and find that the growth rate of this instability is greater than the competing KHI in relativistic shears. The analytical results are confirmed with 2D particle-in-cell (PIC) simulations. Simulations also reveal the nonlinear evolution of the instability which leads to the development of mushroom-like electron-density structures, similar to the Rayleigh Taylor instability. Finally, the interplay between the competing instabilities is investigated in 3D PIC simulations.
Belof, J L; Cavallo, R M; Olson, R T; King, R S; Gray, G T; Holtkamp, D B; Chen, S R; Rudd, R E; Barton, N R; Arsenlis, A; Remington, B A; Park, H; Prisbrey, S T; Vitello, P A; Bazan, G; Mikaelian, K O; Comley, A J; Maddox, B R; May, M J
2011-08-10
We present here the first dynamic Rayleigh-Taylor (RT) strength measurement of a material undergoing solid-solid phase transition. Iron is quasi-isentropically driven across the pressure-induced bcc ({alpha}-Fe) {yields} hcp ({var_epsilon}-Fe) phase transition and the dynamic strength of the {alpha}, {var_epsilon} and reverted {alpha}{prime} phases have been determined via proton radiography of the resulting Rayleigh-Taylor unstable interface between the iron target and high-explosive products. Simultaneous velocimetry measurements of the iron free surface yield the phase transition dynamics and, in conjunction with detailed hydrodynamic simulations, allow for determination of the strength of the distinct phases of iron. Forward analysis of the experiment via hydrodynamic simulations reveals significant strength enhancement of the dynamically-generated {var_epsilon}-Fe and reverted {alpha}{prime}-Fe, comparable in magnitude to the strength of austenitic stainless steels.
3D analyses of cavitation instabilities accounting for plastic anisotropy
Legarth, Brian Nyvang; Tvergaard, Viggo
2010-01-01
, and the main focus is on the effect of different degrees of plastic anisotropy. Loading cases are considered, where all the macroscopic principal stresses differ. The numerical quasi‐static solutions are obtained by a full transient analysis of the equations of motion, in which the loading is applied so slowly......Full three dimensional cell model analyses are carried out for a solid containing a single small void, in order to determine the critical stress levels for the occurrence of cavitation instabilities. The material models applied are elastic‐viscoplastic, with a small rate‐hardening exponent...... that the quasi‐static solution is well approximated. A special procedure is used to strongly reduce the loading rate a little before the instability occurs. It is found that plastic anisotropy has a significant effect on the level of the critical stress for cavitation instabilities....
On hot-wire diagnostics in Rayleigh-Taylor mixing layers
Kraft, Wayne N. [Texas A and M University, Department of Mechanical Engineering, College Station, TX (United States); Banerjee, Arindam [Missouri University of Science and Technology, Department of Mechanical and Aerospace Engineering, Rolla, MO (United States); Andrews, Malcolm J. [Texas A and M University, Department of Mechanical Engineering, College Station, TX (United States); Los Alamos National Laboratory, NM (United States)
2009-07-15
Two hot-wire flow diagnostics have been developed to measure a variety of turbulence statistics in the buoyancy driven, air-helium Rayleigh-Taylor mixing layer. The first diagnostic uses a multi-position, multi-overheat (MPMO) single wire technique that is based on evaluating the wire response function to variations in density, velocity and orientation, and gives time-averaged statistics inside the mixing layer. The second diagnostic utilizes the concept of temperature as a fluid marker, and employs a simultaneous three-wire/cold-wire anemometry technique (S3WCA) to measure instantaneous statistics. Both of these diagnostics have been validated in a low Atwood number (A{sub t}{<=} 0.04), small density difference regime, that allowed validation of the diagnostics with similar experiments done in a hot-water/cold-water water channel facility. Good agreement is found for the measured growth parameters for the mixing layer, velocity fluctuation anisotropy, velocity fluctuation p.d.f behavior, and measurements of molecular mixing. We describe in detail the MPMO and S3WCA diagnostics, and the validation measurements in the low Atwood number regime (A{sub t}{<=} 0.04). We also outline the advantages of each technique for measurement of turbulence statistics in fluid mixtures with large density differences. (orig.)
Effect of noise on Rayleigh-Taylor mixing with space-dependent acceleration
Pandian, Arun; Abarzhi, Snezhana
2016-11-01
We analyze, for the first time by our knowledge, the effect of noise on Rayleigh-Taylor (RT) mixing with space-dependent acceleration by applying the stochastic model. In these conditions, the RT mixing is a statistically unsteady process where the means values of the flow quantities vary in space and time, and there are also the space and time dependent fluctuations around these mean values. The stochastic model is derived from the momentum model and is represented by a set of nonlinear differential equations with multiplicative noise. The models equations are solved theoretically and numerically. Investigating a broad range of values of acceleration, self-similar asymptotic solutions are found in the mixing regime. There are two types of mixing sub-regimes (acceleration-driven and dissipation-driven respectively), each of which has its own types of solutions and characteristic values with the latter saturating to a value on the order of one. It is also observed that the representation of the dynamics in an implicit form is noisier as compared to the case of an explicit time-dependent form. The work is supported by the US National Science Foundation.
Cherniavski, V M
2013-01-01
The potential flow of an incompressible inviscid heavy fluid over a light one is considered. The integral version of the method of matched asymptotic expansion is applied to the construction of the solution over long intervals of time. The asymptotic solution describes the flow in which a bubble rises with constant speed and the "tongue" is in free fall. The outer expansion is stationary, but the inner one depends on time. It is shown that the solution exists within the same range of Froude number obtained previously by Vanden-Broeck (1984a,b). The Froude number and the solution depend on the initial energy of the disturbance. At the top of the bubble, the derivative of the free-surface curvature has a discontinuity when the Froude number is not equal to 0.23. This makes it possible to identify the choice of the solution obtained in a number of studies with the presence of an artificial numerical surface tension. The first correction term in the neighborhood of the tongue is obtained when large surface tensio...
Long-wave analysis and control of the viscous Rayleigh-Taylor instability with electric fields
Cimpeanu, Radu; Anderson, Thomas; Petropoulos, Peter; Papageorgiou, Demetrios
2016-11-01
We investigate the electrostatic stabilization of a viscous thin film wetting the underside of a solid surface in the presence of a horizontally acting electric field. The competition between gravity, surface tension and the nonlocal effect of the applied electric field is captured analytically in the form of a nonlinear evolution equation. A semi-spectral solution strategy is employed to resolve the dynamics of the resulting partial differential equation. Furthermore, we conduct direct numerical simulations (DNS) of the Navier-Stokes equations and assess the accuracy of the obtained solutions when varying the electric field strength from zero up to the point when complete stabilization at the target finite wavelengths occurs. We employ DNS to examine the limitations of the asymptotically derived behavior in the context of increasing liquid film heights, with agreement found to be excellent even beyond the target lengthscales. Regimes in which the thin film assumption is no longer valid and droplet pinch-off occurs are then analyzed. Finally, the asymptotic and computational approaches are used in conjunction to identify efficient active control mechanisms allowing the manipulation of the fluid interface in light of engineering applications at small scales, such as mixing.
3D Printing Variable Stiffness Foams Using Viscous Thread Instability
Lipton, Jeffrey I.; Lipson, Hod
2016-08-01
Additive manufacturing of cellular structures has numerous applications ranging from fabrication of biological scaffolds and medical implants, to mechanical weight reduction and control over mechanical properties. Various additive manufacturing processes have been used to produce open regular cellular structures limited only by the resolution of the printer. These efforts have focused on printing explicitly designed cells or explicitly planning offsets between strands. Here we describe a technique for producing cellular structures implicitly by inducing viscous thread instability when extruding material. This process allows us to produce complex cellular structures at a scale that is finer than the native resolution of the printer. We demonstrate tunable effective elastic modulus and density that span two orders of magnitude. Fine grained cellular structures allow for fabrication of foams for use in a wide range of fields ranging from bioengineering, to robotics to food printing.
Detailed Measurements of Turbulent Rayleigh-Taylor Mixing at Large and Small Atwood Numbers
Malcolm J. Andrews, Ph.D.
2004-12-14
This project has two major tasks: Task 1. The construction of a new air/helium facility to collect detailed measurements of Rayleigh-Taylor (RT) mixing at high Atwood number, and the distribution of these data to LLNL, LANL, and Alliance members for code validation and design purposes. Task 2. The collection of initial condition data from the new Air/Helium facility, for use with validation of RT simulation codes at LLNL and LANL. Also, studies of multi-layer mixing with the existing water channel facility. Over the last twelve (12) months there has been excellent progress, detailed in this report, with both tasks. As of December 10, 2004, the air/helium facility is now complete and extensive testing and validation of diagnostics has been performed. Currently experiments with air/helium up to Atwood numbers of 0.25 (the maximum is 0.75, but the highest Reynolds numbers are at 0.25) are being performed. The progress matches the project plan, as does the budget, and we expect this to continue for 2005. With interest expressed from LLNL we have continued with initial condition studies using the water channel. This work has also progressed well, with one of the graduate Research Assistants (Mr. Nick Mueschke) visiting LLNL the past two summers to work with Dr. O. Schilling. Several journal papers are in preparation that describe the work. Two MSc.'s have been completed (Mr. Nick Mueschke, and Mr. Wayne Kraft, 12/1/03). Nick and Wayne are both pursuing Ph.D.s' funded by this DOE Alliances project. Presently three (3) Ph.D. graduate Research Assistants are supported on the project, and two (2) undergraduate Research Assistants. During the year two (2) journal papers and two (2) conference papers have been published, ten (10) presentations made at conferences, and three (3) invited presentations.
How Do Hydrodynamic Instabilities Affect 3D Transport in Geophysical Vortices?
Wang, P.; Ozgokmen, T. M.
2014-12-01
Understanding three-dimensional (3D) transport in ocean eddies is important for processes at a variety of scales, ranging from plankton production to climate variability. It is well known that geophysical vortices are subject to various hydrodynamic instabilities. Yet the influence of these instabilities on 3D material transport in vortex systems is not well investigated. Focusing on barotropic, inertial and 3D instabilities, we analyze these instabilities with normal-mode method, and reproduce their characteristics via highly-resolved numerical simulations using a spectral element Navier-Stokes solver. By comparing the simulation results of stable and unstable vortices, we investigate the joint impacts of instabilities on 3D transport through three major aspects: (i) energy transfer, (ii) overturning transport of the secondary circulation, and (iii) rates of vertical exchange and mixing. It is found that instabilities can enhance local nonlinear interactions and cause the kinetic energy wavenumber spectrum to have slopes between the conventional -5/3 and -3 at inertial ranges. The cascade of a new quantity is proposed to explain these non-conventional slopes. One of our main results is the discovery of material exchange between the central vortex and satellite vortices through 3D pathways, called funnels. These funnels modify the concept of elliptic regions that can trap material when confined to 2D dynamics. Thus, we show that a family of vortices, created by the hydrodynamic instabilities of the initially unstable vortex, can still continue to operate in unity in order to complete the 3D transport in these systems. We also show that flow instabilities can double the magnitude of vertical velocity, increase the rate of vertical exchange by an order of magnitude and enhance mixing rate more than 100%.
Y.G. Cao; W.K. Chow; N.K. Fong
2011-01-01
With a self-similar parameter b（At） = Hi/λi, where At is the Atwood number, Hi and λi are the a.mplluae and wavelength of bubble （i = 1） and spike （i = 2） respectively, we derive analytically the solutions to the buoyancy-drag equation recently proposed for dynamical evolution of Rayleigh-Taylor and Richtmyer-Meshkov mixing zone. Numerical solutions are obtained with a simple form ofb（At）--- 1/（1 ＋ At） and comparisons with recent LEM （linear electric motor） experiments are made, and an agreement is found with properly chosen initial conditions.
Rayleigh-Taylor Gravity Waves and Quasiperiodic Oscillation Phenomenon in X-ray Binaries
Titarchuk, Lev
2002-01-01
Accretion onto compact objects in X-ray binaries (black hole, neutron star (NS), white dwarf) is characterized by non-uniform flow density profiles. Such an effect of heterogeneity in presence of gravitational forces and pressure gradients exhibits Rayleigh-Taylor gravity waves (RTGW). They should be seen as quasiperiodic wave oscillations (QPO) of the accretion flow in the transition (boundary) layer between the Keplerian disk and the central object. In this paper the author shows that the main QPO frequency, which is very close to the Keplerian frequency, is split into separate frequencies (hybrid and low branch) under the influence of the gravitational forces in the rotational frame of reference. The RTGWs must be present and the related QPOs should be detected in any system where the gravity, buoyancy and Coriolis force effects cannot be excluded (even in the Earth and solar environments). The observed low and high QPO frequencies are an intrinsic signature of the RTGW. The author elaborates the conditions for the density profile when the RTGW oscillations are stable. A comparison of the inferred QPO frequencies with QPO observations is presented. The author finds that hectohertz frequencies detected from NS binaries can be identified as the RTGW low branch frequencies. The author also predicts that an observer can see the double NS spin frequency during the NS long (super) burst events when the pressure gradients and buoyant forces are suppressed. The Coriolis force is the only force which acts in the rotational frame of reference and its presence causes perfect coherent pulsations with a frequency twice of the NS spin. The QPO observations of neutron binaries have established that the high QPO frequencies do not go beyond of the certain upper limit. The author explains this observational effect as a result of the density profile inversions. Also the author demonstrates that a particular problem of the gravity waves in the rotational frame of reference in the
An axis-free overset grid in spherical polar coordinates for simulating 3D self-gravitating flows
Wongwathanarat, Annop; Müller, Ewald
2010-01-01
A type of overlapping grid in spherical coordinates called the Yin-Yang grid is successfully implemented into a 3D version of the explicit Eulerian grid-based code PROMETHEUS including self-gravity. The modified code successfully passed several standard hydrodynamic tests producing results which are in very good agreement with analytic solutions. Moreover, the solutions obtained with the Yin-Yang grid exhibit no peculiar behaviour at the boundary between the two grid patches. The code has also been successfully used to model astrophysically relevant situations, namely equilibrium polytropes, a Taylor-Sedov explosion, and Rayleigh-Taylor instabilities. According to our results, the usage of the Yin-Yang grid greatly enhances the suitability and efficiency of 3D explicit Eulerian codes based on spherical polar coordinates for astrophysical flows.
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.
Madura, T. I.; Clementel, N.; Gull, T. R.; Kruip, C. J. H.; Paardekooper, J.-P.
2015-06-01
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 M⊙), highly eccentric (e ˜ 0.9) binary star system η Carinae. We demonstrate the methodology used to incorporate 3D interactive figures into a PDF (Portable Document Format) journal publication and the benefits of using 3D visualization and 3D printing as tools to analyse data from multidimensional numerical simulations. Using a consumer-grade 3D printer (MakerBot Replicator 2X), we successfully printed 3D smoothed particle hydrodynamics simulations of η Carinae's inner (r ˜ 110 au) wind-wind collision interface at multiple orbital phases. The 3D prints and visualizations reveal important, previously unknown `finger-like' structures at orbital phases shortly after periastron (φ ˜ 1.045) that protrude radially outwards from the spiral wind-wind collision region. We speculate that these fingers are related to instabilities (e.g. thin-shell, Rayleigh-Taylor) that arise at the interface between the radiatively cooled layer of dense post-shock primary-star wind and the fast (3000 km s-1), adiabatic post-shock companion-star wind. The success of our work and easy identification of previously unrecognized physical features highlight the important role 3D printing and interactive graphics can play in the visualization and understanding of complex 3D time-dependent numerical simulations of astrophysical phenomena.
Kelvin-Helmholtz instability in a current-vortex sheet at a 3D magnetic null
Wyper, P. F.; Pontin, D. I.
2013-03-01
We report here, for the first time, an observed instability of a Kelvin-Helmholtz nature occurring in a fully three-dimensional (3D) current-vortex sheet at the fan plane of a 3D magnetic null point. The current-vortex layer forms self-consistently in response to foot point driving around the spine lines of the null. The layer first becomes unstable at an intermediate distance from the null point, with the instability being characterized by a rippling of the fan surface and a filamentation of the current density and vorticity in the shear layer. Owing to the 3D geometry of the shear layer, a branching of the current filaments and vortices is observed. The instability results in a mixing of plasma between the two topologically distinct regions of magnetic flux on either side of the fan separatrix surface, as flux is reconnected across this surface. We make a preliminary investigation of the scaling of the system with the dissipation parameters. Our results indicate that the fan plane separatrix surface is an ideal candidate for the formation of current-vortex sheets in complex magnetic fields and, therefore, the enhanced heating and connectivity change associated with the instabilities of such layers.
Kelvin-Helmholtz instability in a current-vortex sheet at a 3D magnetic null
Wyper, P. F. [School of Mathematics and Statistics, University of Sheffield, Sheffield S3 7RH (United Kingdom); Pontin, D. I. [Division of Mathematics, University of Dundee, Dundee DD1 4HN (United Kingdom)
2013-03-15
We report here, for the first time, an observed instability of a Kelvin-Helmholtz nature occurring in a fully three-dimensional (3D) current-vortex sheet at the fan plane of a 3D magnetic null point. The current-vortex layer forms self-consistently in response to foot point driving around the spine lines of the null. The layer first becomes unstable at an intermediate distance from the null point, with the instability being characterized by a rippling of the fan surface and a filamentation of the current density and vorticity in the shear layer. Owing to the 3D geometry of the shear layer, a branching of the current filaments and vortices is observed. The instability results in a mixing of plasma between the two topologically distinct regions of magnetic flux on either side of the fan separatrix surface, as flux is reconnected across this surface. We make a preliminary investigation of the scaling of the system with the dissipation parameters. Our results indicate that the fan plane separatrix surface is an ideal candidate for the formation of current-vortex sheets in complex magnetic fields and, therefore, the enhanced heating and connectivity change associated with the instabilities of such layers.
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.
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.
Madura, Thomas I; Gull, Theodore R; Kruip, Chael J H; Paardekooper, Jan-Pieter
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 M_Sun), highly eccentric (e ~ 0.9) binary star system Eta Carinae. We demonstrate the methodology used to incorporate 3D interactive figures into a PDF journal publication and the benefits of using 3D visualization and 3D printing as tools to analyze data from multidimensional numerical simulations. Using a consumer-grade 3D printer (MakerBot Replicator 2X), we successfully printed 3D smoothed particle hydrodynamics (SPH) simulations of Eta Carinae's inner (r ~ 110 au) wind-wind collision interface at multiple orbital phases. The 3D prints and visualizations reveal important, previously unknown 'finger-like' structures at orbital phases shortly after periastron (phi ~ 1.045) that protrude radially outward from the spiral wind-wind collision region. We speculate that these fingers are related to instabilities (e.g. thin-shell, Rayleigh-Taylor) that arise a...
Kelvin-Helmholtz instability in a current-vortex sheet at a 3D magnetic null
Wyper, P F
2013-01-01
We report here, for the first time, an observed instability of a Kelvin-Helmholtz (KH) nature occurring in a fully three-dimensional (3D) current-vortex sheet at the fan plane of a 3D magnetic null point. The current-vortex layer forms self-consistently in response to foot point driving around the spine lines of the null. The layer first becomes unstable at an intermediate distance from the null point, with the instability being characterized by a rippling of the fan surface and a filamentation of the current density and vorticity in the shear layer. Owing to the 3D geometry of the shear layer, a branching of the current filaments and vortices is observed. The instability results in a mixing of plasma between the two topologically distinct regions of magnetic flux on either side of the fan separatrix surface, as flux is reconnected across this surface. We make a preliminary investigation of the scaling of the system with the dissipation parameters. Our results indicate that the fan plane separatrix surface is...
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 ...
Parametric instabilities in 3D periodically focused beams with space charge
Hofmann, Ingo; Boine-Frankenheim, Oliver
2017-01-01
Parametric resonances of beam eigenmodes with a periodic focusing system under the effect of space charge—also called structural instabilities—are the collective counterparts to parametric resonances of single particles or of mechanical systems. Their common feature is that an exponential instability is driven by a temporal modulation of a system parameter. Thus, they are complementary to the more commonly considered space charge single particle resonances, where space charge pseudo-multipole terms are assumed to exist already at finite level in the initial distribution. This article elaborates on the characteristics of such parametric instabilities in 3D bunched beams—as typical in linear accelerators—for modes of second (envelope), third and fourth order, including the transverse coupled "sum envelope instabilities" recently discovered for 2D beams. Noteworthy results are the finding that parametric resonances can be in competition with single particle resonances of twice the order due to overlapping stopbands; furthermore the surprisingly good applicability of the stopband positions and widths obtained from previously published 2D linearised Vlasov stability theory to the 3D non-Kapchinskij-Vladimirskij particle-in-cell code studies presented here.
Bret, Antoine
2014-01-01
The filamentation (Weibel) instability plays a key role in the formation of collisionless shocks which are thought to produce Gamma-Ray-Bursts and High-Energy-Cosmic-Rays in astrophysical environments. While it has been known for long that a flow-aligned magnetic field can completely quench the instability, it was recently proved in 2D that in the cold regime, such cancelation is possible if and only if the field is perfectly aligned. Here, this result is finally extended to a 3D geometry. Calculations are conducted for symmetric and asymmetric counter-streaming relativistic plasma shells. 2D results are retrieved in 3D: the instability can never be completely canceled for an oblique magnetic field. In addition, the maximum growth-rate is always larger for wave vectors lying in the plan defined by the flow and the oblique field. On the one hand, this bears consequences on the orientation of the generated filaments. On the other hand, it certifies 2D simulations of the problem can be performed without missing ...
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...
Early Earth tectonics: A high-resolution 3D numerical modelling approach
Fischer, R.; Gerya, T.
2014-12-01
Early Earth had a higher amount of remaining radiogenic elements as well as a higher amount of leftover primordial heat. Both contributed to the increased temperature in the Earth's interior and it is mainly this increased mantle potential temperature ΔTp that controls the dynamics of the crust and upper mantle and the style of Early Earth tectonics. For a minor increase in temperature ΔTp buckling, delamination and Rayleigh-Taylor style dripping of the plate is observed in addition. For higher temperatures ΔTp > 250 K no subduction can be observed anymore and tectonics is dominated by delamination and Rayleigh-Taylor instabilities. We conduct 3D petrological-thermomechanical numerical modelling experiments of the crust and upper mantle under Early Earth conditions and a plume tectonics model setup. For varying crustal structures and an increased mantle potential temperature ΔTp, a thermal anomaly in the bottom temperature boundary introduces a plume. The model is able to self-sufficiently form depleted mantle lithosphere after repeated melt removal. New crust can be produced in the form of volcanics or plutonics. To simulate differentiation the newly formed crust can have a range in composition from basaltic over dacitic to granitic depending on its source rock. Models show large amounts of subcrustal decompression melting and consequently large amounts of new formed crust which in turn influences the dynamics. Mantle and crust are convecting separately. Dome-shaped plutons of mafic or felsic composition can be observed in the crust. Between these domes elongated belts of upper crust, volcanics and sediments are formed. These structures look similar to, for example, the Kaapvaal craton in South Africa where the elongated shape of the Barberton Greenstone Belt is surrounded by multiple plutons.
Morgan, Brandon; Olson, Britton; White, Justin; McFarland, Jacob
2016-11-01
High-fidelity large eddy simulation (LES) of a low-Atwood number (A = 0.05) Rayleigh-Taylor mixing layer is performed using the tenth-order compact difference code Miranda. An initial multimode perturbation spectrum is specified in Fourier space as a function of mesh resolution such that a database of results is obtained in which each successive level of increased grid resolution corresponds approximately to one additional doubling of the mixing layer width, or generation. The database is then analyzed to determine approximate requirements for self-similarity, and a new metric is proposed to quantify how far a given simulation is from the limit of self-similarity. It is determined that the present database reaches a high degree of self-similarity after approximately 4.5 generations. Finally, self-similar turbulence profiles from the LES database are compared with one-dimensional simulations using the k- L- a and BHR-2 Reynolds-averaged Navier-Stokes (RANS) models. The k- L- a model, which is calibrated to reproduce a quadratic turbulence kinetic energy profile for a self-similar mixing layer, is found to be in better agreement with the LES than BHR-2 results. This work was preformed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.
Pandian, Arun; Swisher, Nora C.; Abarzhi, S. I.
2017-01-01
Rayleigh-Taylor (RT) mixing occurs in a variety of natural and man-made phenomena in fluids, plasmas and materials, from celestial event to atoms. In many circumstances, RT flows are driven by variable acceleration, whereas majority of existing studies have considered only sustained acceleration. In this work we perform detailed analytical and numerical study of RT mixing with a power-law time-dependent acceleration. A set of deterministic nonlinear non-homogeneous ordinary differential equations and nonlinear stochastic differential equations with multiplicative noise are derived on the basis of momentum model. For a broad range of parameters, self-similar asymptotic solutions are found analytically, and their statistical properties are studied numerically. We identify two sub-regimes of RT mixing dynamics depending on the acceleration exponent—the acceleration-driven mixing and dissipation-driven mixing. Transition between the sub-regimes is studied, and it is found that each sub-regime has its own characteristic dimensionless invariant quantity.
Instabilities at planetary gap edges in 3D self-gravitating disks
Lin, Min-Kai
2013-01-01
Numerical simulations are presented to study the stability of gaps opened by giant planets in 3D self-gravitating disks. In weakly self-gravitating disks, a few vortices develop at the gap edge and merge on orbital time-scales. The result is one large but weak vortex with Rossby number -0.01. In moderately self-gravitating disks, more vortices develop and their merging is resisted on dynamical time-scales. Self-gravity can sustain multi-vortex configurations, with Rossby number -0.2 to -0.1, over a time-scale of order 100 orbits. Self-gravity also enhances the vortex vertical density stratification, even in disks with initial Toomre parameter of order 10. However, vortex formation is suppressed in strongly self-gravitating disks and replaced by a global spiral instability associated with the gap edge which develops during gap formation.
Instabilities at planetary gap edges in 3D self-gravitating disks
Lin Min-Kai
2013-04-01
Full Text Available Numerical simulations are presented to study the stability of gaps opened by giant planets in 3D self-gravitating disks. In weakly self-gravitating disks, a few vortices develop at the gap edge and merge on orbital time-scales. The result is one large but weak vortex with Rossby number -0.01. In moderately self-gravitating disks, more vortices develop and their merging is resisted on dynamical time-scales. Self-gravity can sustain multi-vortex configurations, with Rossby number -0.2 to -0.1, over a time-scale of order 100 orbits. Self-gravity also enhances the vortex vertical density stratification, even in disks with initial Toomre parameter of order 10. However, vortex formation is suppressed in strongly self-gravitating disks and replaced by a global spiral instability associated with the gap edge which develops during gap formation.
Quasi 3D ECE imaging system for study of MHD instabilities in KSTAR
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.
Thermo/Soluto-capillary instabilities in 3D bi-component liquid pools using DNS
Williams, Adam; Saenz, Pedro; Valluri, Prashant; Sefiane, Khellil
2015-11-01
The behaviour of surface tension dominated flows in the presence of a temperature gradient and phase change is of great importance in designing micro-cooling devices. While evaporating pools and droplets have been investigated numerically and experimentally, these studies have dealt only with pure fluids. For bicomponent liquid mixtures, limited experimental studies have been conducted but a rigorous numerical model is absent. We present a two-phase multicomponent DNS model to simulate thermo/soluto-capillary instabilities in bicomponent liquid layers subject to a horizontal temperature gradient. The strategy fully accounts for a deformable interface using a variant of volume-of-fluid method. The presence of a second component introduces thermophoresis in the liquid phase which then gives rise to solutal Marangoni effects. By combining mixture thermodynamics with multiphase DNS, we investigate thermo/soluto-capillary and interfacial instabilities of a 3D bicomponent liquid pool. An important aspect we quantify is the strength of solutal over thermal Marangoni convection and its effect on stability of resultant interfacial waves and phase-separation in the liquid. The model is robust enough to include phase-change and the advection-diffusion of volatile species in the gas phase. Funded by EPSRC, Grant No. EP/K00963X/1.
Mueschke, N; Schilling, O
2008-07-23
A 1152 x 760 x 1280 direct numerical simulation (DNS) using initial conditions, geometry, and physical parameters chosen to approximate those of a transitional, small Atwood number Rayleigh-Taylor mixing experiment [Mueschke, Andrews and Schilling, J. Fluid Mech. 567, 27 (2006)] is presented. The density and velocity fluctuations measured just off of the splitter plate in this buoyantly unstable water channel experiment were parameterized to provide physically-realistic, anisotropic initial conditions for the DNS. The methodology for parameterizing the measured data and numerically implementing the resulting perturbation spectra in the simulation is discussed in detail. The DNS model of the experiment is then validated by comparing quantities from the simulation to experimental measurements. In particular, large-scale quantities (such as the bubble front penetration hb and the mixing layer growth parameter {alpha}{sub b}), higher-order statistics (such as velocity variances and the molecular mixing parameter {theta}), and vertical velocity and density variance spectra from the DNS are shown to be in favorable agreement with the experimental data. Differences between the quantities obtained from the DNS and from experimental measurements are related to limitations in the dynamic range of scales resolved in the simulation and other idealizations of the simulation model. This work demonstrates that a parameterization of experimentally-measured initial conditions can yield simulation data that quantitatively agrees well with experimentally-measured low- and higher-order statistics in a Rayleigh-Taylor mixing layer. This study also provides resolution and initial conditions implementation requirements needed to simulate a physical Rayleigh-Taylor mixing experiment. In Part II [Mueschke and Schilling, Phys. Fluids (2008)], other quantities not measured in the experiment are obtained from the DNS and discussed, such as the integral- and Taylor-scale Reynolds numbers
Laboratory blast wave driven instabilities
Kuranz, Carolyn
2008-11-01
This presentation discusses experiments involving the evolution of hydrodynamic instabilities in the laboratory under high-energy-density (HED) conditions. These instabilities are driven by blast waves, which occur following a sudden, finite release of energy, and consist of a shock front followed by a rarefaction wave. When a blast wave crosses an interface with a decrease in density, hydrodynamic instabilities will develop. Instabilities evolving under HED conditions are relevant to astrophysics. These experiments include target materials scaled in density to the He/H layer in SN1987A. About 5 kJ of laser energy from the Omega Laser facility irradiates a 150 μm plastic layer that is followed by a low-density foam layer. A blast wave structure similar to those in supernovae is created in the plastic layer. The blast wave crosses an interface having a 2D or 3D sinusoidal structure that serves as a seed perturbation for hydrodynamic instabilities. This produces unstable growth dominated by the Rayleigh-Taylor (RT) instability in the nonlinear regime. We have detected the interface structure under these conditions using x-ray backlighting. Recent advances in our diagnostic techniques have greatly improved the resolution of our x-ray radiographic images. Under certain conditions, the improved images show some mass extending beyond the RT spike and penetrating further than previously observed or predicted by current simulations. The observed effect is potentially of great importance as a source of mass transport to places not anticipated by current theory and simulation. I will discuss the amount of mass in these spike extensions, the associated uncertainties, and hypotheses regarding their origin We also plan to show comparisons of experiments using single mode and multimode as well as 2D and 3D initial conditions. This work is sponsored by DOE/NNSA Research Grants DE-FG52-07NA28058 (Stewardship Sciences Academic Alliances) and DE-FG52-04NA00064 (National Laser User
WANG Jing-yi; ZOU Jian-feng; ZHENG Yao; REN An-lu
2011-01-01
A front tracking method based on a marching cubes isosurface extractor,which is related filter generating isosurfaces from a structured point set,is provided to achieve sharp resolution for the simulation of non-diffusive interfacial flow.Compared with the traditional topology processing procedure,the current front tracking method is easier to be implemented and presents high performance in terms of computational resources.The numerical tests for 2-D highly-shearing flows and 3-D bubbles merging process are conducted to numerically examine the performance of the current methodology for tracking interfaces between two immiscible fluids.The Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) instability problems are successfully investigated with the present marching cubes based front tracking method.
Andronov, V.A.; Zhidov, I.G.; Meskov, E.E.; Nevmerzhitskii, N.V.; Nikiforov, V.V.; Razin, A.N.; Rogatchev, V.G.; Tolshmyakov, A.I.; Yanilkin, Y.V. [Russian Federal Nuclear Center (Russian Federation)
1994-12-31
The report presents the basic results of some calculations, theoretical and experimental efforts in the study of Rayleigh-Taylor, Kelvin-Helmholtz, Richtmyer-Meshkov instabilities and the turbulent mixing which is caused by their evolution. Since the late forties the VNIIEF has been conducting these investigations. This report is based on the data which were published in different times in Russian and foreign journals. The first part of the report deals with calculations an theoretical techniques for the description of hydrodynamic instabilities applied currently, as well as with the results of several individual problems and their comparison with the experiment. These methods can be divided into two types: direct numerical simulation methods and phenomenological methods. The first type includes the regular 2D and 3D gasdynamical techniques as well as the techniques based on small perturbation approximation and on incompressible liquid approximation. The second type comprises the techniques based on various phenomenological turbulence models. The second part of the report describes the experimental methods and cites the experimental results of Rayleigh-Taylor and Richtmyer-Meskov instability studies as well as of turbulent mixing. The applied methods were based on thin-film gaseous models, on jelly models and liquid layer models. The research was done for plane and cylindrical geometries. As drivers, the shock tubes of different designs were used as well as gaseous explosive mixtures, compressed air and electric wire explosions. The experimental results were applied in calculational-theoretical technique calibrations. The authors did not aim at covering all VNIIEF research done in this field of science. To a great extent the choice of the material depended on the personal contribution of the author in these studies.
Simulation of the Initial 3-D Instability of an Impacting Drop Vortex Ring
Sigurdson, Lorenz; Wiwchar, Justin; Walther, Jens Honore
2013-01-01
Computational vortex particle method simulations of a perturbed vortex ring are performed to recreate and understand the instability seen in impacting water drop experiments. Three fundamentally different initial vorticity distributions are used to attempt to trigger a Widnall instability......, a Rayleigh centrifugal instability, or a vortex breakdown-type instability. Simulations which simply have a perturbed solitary ring result in an instability similar to that seen experimentally. Waviness of the core which would be expected from a Widnall instability is not visible. Adding an opposite......, though tests are not conclusive. Perhaps the opposite-signed secondary vortex was not strong enough or placed appropriately. Elliptical streamlines , as expected, are visible in the core of the solitary ring at early times. Support from the Canadian Natural Sciences and Engineering Research Council grant...
Awe, T. J.; Jennings, C. A.; McBride, R. D.; Cuneo, M. E.; Lamppa, D. C.; Martin, M. R.; Rovang, D. C.; Sinars, D. B.; Slutz, S. A.; Owen, A. C.; Tomlinson, K.; Gomez, M. R.; Hansen, S. B.; Herrmann, M. C.; Jones, M. C.; McKenney, J. L.; Robertson, G. K.; Rochau, G. A.; Savage, M. E.; Schroen, D. G.; Stygar, W. A.
2014-05-01
Recent experiments at the Sandia National Laboratories Z Facility have, for the first time, studied the implosion dynamics of magnetized liner inertial fusion (MagLIF) style liners that were pre-imposed with a uniform axial magnetic field. As reported [T. J. Awe et al., Phys. Rev. Lett. 111, 235005 (2013)] when premagnetized with a 7 or 10 T axial field, these liners developed 3D-helix-like hydrodynamic instabilities; such instabilities starkly contrast with the azimuthally correlated magneto-Rayleigh-Taylor (MRT) instabilities that have been consistently observed in many earlier non-premagnetized experiments. The helical structure persisted throughout the implosion, even though the azimuthal drive field greatly exceeded the expected axial field at the liner's outer wall for all but the earliest stages of the experiment. Whether this modified instability structure has practical importance for magneto-inertial fusion concepts depends primarily on whether the modified instability structure is more stable than standard azimuthally correlated MRT instabilities. In this manuscript, we discuss the evolution of the helix-like instability observed on premagnetized liners. While a first principles explanation of this observation remains elusive, recent 3D simulations suggest that if a small amplitude helical perturbation can be seeded on the liner's outer surface, no further influence from the axial field is required for the instability to grow.
Tijssen, Rob H N; Okell, Thomas W; Miller, Karla L
2011-08-15
Although 2D echo-planar imaging (EPI) remains the dominant method for functional MRI (FMRI), 3D readouts are receiving more interest as these sequences have favorable signal-to-noise ratio (SNR) and enable imaging at a high isotropic resolution. Spoiled gradient-echo (SPGR) and balanced steady-state free-precession (bSSFP) are rapid sequences that are typically acquired with highly segmented 3D readouts, and thus less sensitive to image distortion and signal dropout. They therefore provide a powerful alternative for FMRI in areas with strong susceptibility offsets, such as deep gray matter structures and the brainstem. Unfortunately, the multi-shot nature of the readout makes these sequences highly sensitive to physiological fluctuations, and large signal instabilities are observed in the inferior regions of the brain. In this work a characterization of the source of these instabilities is given and a new method is presented to reduce the instabilities observed in 3D SPGR and bSSFP. Rapidly acquired single-slice data, which critically sampled the respiratory and cardiac waveforms, showed that cardiac pulsation is the dominant source of the instabilities. Simulations further showed that synchronizing the readout to the cardiac cycle minimizes the instabilities considerably. A real-time synchronization method was therefore developed, which utilizes parallel-imaging techniques to allow cardiac synchronization without alteration of the volume acquisition rate. The implemented method significantly improves the temporal stability in areas that are affected by cardiac-related signal fluctuations. In bSSFP data the tSNR in the brainstem increased by 45%, at the cost of a small reduction in tSNR in the cortical areas. In SPGR the temporal stability is improved by approximately 20% in the subcortical structures and as well as cortical gray matter when synchronization was performed.
Markenstein, Jeroen E. [Onze Lieve Vrouwe Gasthuis, Department of Orthopedic Surgery, Postbox 95500, Amsterdam (Netherlands); Jaspars, Kjell C.C.J. [Van Weel-Bethesda Ziekenhuis, Department of Orthopedic Surgery, Dirksland (Netherlands); Hulst, Victor P.M. van der [Onze Lieve Vrouwe Gasthuis, Department of Radiology, Postbox 95500, Amsterdam (Netherlands); Willems, W.J. [Delairesse Kliniek, Department of Orthopedic Surgery, Amsterdam (Netherlands)
2014-04-15
The purpose of this study is to investigate if magnetic resonance imaging with intra-articular contrast (MR-arthro) is as reliable as three-dimensionally reconstructed computed tomography imaging (3D-CT) in quantifying the glenoid bone loss in patients with anterior shoulder instability. Thirty-five patients were included. Sagittal MR-arthro and 3D-CT images of the glenoid surface were obtained pre-operatively. Two observers measured these images twice with OsiriX software in a randomized and blinded way. The intraclass correlations (ICC) of the intra- and inter-observer reliability within one method and an additional Bland-Altman plot for calculating agreement between the two methods were obtained. The joint estimates of the intra-observer reliability, taking into account the data from both observer A and B, for 3D-CT and MR-arthro were good to excellent. The intra-observer reliability was 0.938 (95 % CI: 0.879, 0.968) for 3D-CT and 0.799 (95 % CI: 0.639, 0.837) for MR-arthro. The inter-observer reliability between the two observers within one method (3D-CT or MR-arthro) was moderate to good. 3D-CT: 0.724 (95 % CI: 0.236, 0.886) and MR-arthro: 0.534 (95 % CI: 0.128, 0.762). Comparing both the 3D-CT and MR-arthro method, a Bland-Altman plot showed satisfying differences with the majority of outcomes (89 %) within 1 SD. Good to excellent intra- and moderate to good inter-observer correlations and a satisfying Bland-Altman plot when compared to 3D-CT show tendencies that MR-arthro is reliable and valid for measuring bony defects of the glenoid. (orig.)
Direct Numerical Simulation of 3D Salt Fingers: From Secondary Instability to Chaotic Convection
Simeonov, Julian A; Radko, Timour
2009-01-01
The amplification and equilibration of three-dimensional salt fingers in unbounded uniform vertical gradients of temperature and salinity is studied with a Direct Numerical Simulation in a triply periodic computational domain. A fluid dynamics video of the simulation shows that the secondary instability of the fastest growing square-planform finger mode is a combination of the well-known vertical shear instability of two-dimensional fingers [Holyer, 1984] and a new horizontal shear mode.
上颈椎不稳的3 D-CT等影像学和临床表现%The 3D-CT imaging and clinical symptoms of the upper cervical instability
范恒华; 王超; 杜俊杰; 刘冬州; 张洋; 侯中会
2016-01-01
目的：为了提高对上颈椎不稳的认识和重视，系统观察该疾病的3 D-CT影像学和临床表现。方法收集诊治的上颈椎不稳患者62例，采用CT（3D-CT、CTA）、X片等进行检查，结合临床表现，按轴性、前后、旋转不稳3种情况分别展示、描述，并对其进行总结分析和治疗。结果采用3D-CT技术，可以很好的发现和显示上颈椎不稳的原因及解剖结构异常，MRI能发现脊髓、脑干受压畸形等情况。通过对该病的影像学资料总结阅读、能够及时发现，避免漏诊，为及时治疗提供依据。结论采用X片、CT（3D-CT），可以有效发现上颈椎不稳，及时诊断。%Objective In order to pay more attention to upper cervical instability , the imaging of 3D-CT( three dimensional computed tomography and reconstructions ) and clinical symptoms of the upper cervical instability were systematically observed . Methods 62 cases of the upper cervical instability were studied on the diagnosis and treatment using 3D-CT, X films and com-bined with clinical symptoms .The 3D-CT imagings of 3 states, according to axial instability , instability in flexion and extension , rotation instability, were shown and described.Results The 3D-CT technology was a good tool to find and display the causes and anatomical structural abnormalities of upper cervical instability .We could detect and diagnosis the upper cervical instability through the 3D-CT imaging data, and could avoid misdiagnosis , provide the basis for timely treatment .Conclusion The upper cervical spine instability can effectively detect and timely diagnosis by 3D-CT, X-ray.
3D simulations of supernova remnants evolution including non-linear particle acceleration
Ferrand, Gilles; Ballet, Jean; Teyssier, Romain; Fraschetti, Federico
2009-01-01
If a sizeable fraction of the energy of supernova remnant shocks is channeled into energetic particles (commonly identified with Galactic cosmic rays), then the morphological evolution of the remnants must be distinctly modified. Evidence of such modifications has been recently obtained with the Chandra and XMM-Newton X-ray satellites. To investigate these effects, we coupled a semi-analytical kinetic model of shock acceleration with a 3D hydrodynamic code (by means of an effective adiabatic index). This enables us to study the time-dependent compression of the region between the forward and reverse shocks due to the back reaction of accelerated particles, concomitantly with the development of the Rayleigh-Taylor hydrodynamic instability at the contact discontinuity. Density profiles depend critically on the injection level eta of particles: for eta up to about 10^-4 modifications are weak and progressive, for eta of the order of 10^-3 modifications are strong and immediate. Nevertheless, the extension of the...
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 $\\dot{M}$.
Ruiz, Luciana O; Lanfranchi, Gustavo A; Caproni, Anderson
2012-01-01
Theoretical $\\Lambda$CDM cosmological models predict a much larger number of low mass dark matter haloes than has been observed in the Local Group of galaxies. One possible explanation is the increased difficulty of detecting these haloes if most of the visible matter is lost at early evolutionary phases through galactic winds. In this work we study the current models of triggering galactic winds in dwarf spheroidal galaxies (dSph) from supernovae, and study, based on 3D hydrodynamic numerical simulations, the correlation of the mass loss rates and important physical parameters as the dark matter halo mass and its radial profile, and the star formation rate. We find that the existence of winds is ubiquitous, independent on the gravitational potential. Our simulations revealed that the Rayleigh-Taylor Instability (RTI) may play a major role on pushing matter out of these systems, even for very massive haloes. The instability is responsible for 5 - 40% of the mass loss during the early evolution of the galaxy, ...
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
Kelvin-Helmholtz instability with mixing zone; Instabilite de Kelvin-Helmholtz avec zone de melange
Chong-Techer, R. [CEA Saclay, Dept. Modelisation de Systemes et Structures (DEN/DANS/DM2S/DIR-SFME), 91 - Gif sur Yvette (France)
2008-07-01
This thesis is part of the FATHER experiment and the analyze of the hydrodynamical instabilities which appear during the mixing of two liquids of same volume mass with shearing speed in the mixing zone. The aim is to understand the possible influence of a Kelvin-Helmholtz hydrodynamical instability with mixing zone, compared to classical Kelvin-Helmholtz instability with interface and with theoretical results of Rayleigh-Taylor instability. (A.L.B.)
Quasimodes instability analysis of uncertain asymmetric rotor system based on 3D solid element model
Zuo, Yanfei; Wang, Jianjun; Ma, Weimeng
2017-03-01
Uncertainties are considered in the equation of motion of an asymmetric rotor system. Based on Hill's determinant method, quasimodes stability analysis with uncertain parameters is used to get stochastic boundaries of unstable regions. Firstly, A 3D finite element rotor model was built in rotating frame with four parameterized coefficients, which is assumed as random parameters representing the uncertainties existing in the rotor system. Then the influences of uncertain coefficients on the distribution of the unstable region boundaries are analyzed. The results show that uncertain parameters have various influences on the size, boundary and number of unstable regions. At last, the statistic results of the minimum and maximum spin speeds of unstable regions were got by Monte Carlo simulation. The used method is suitable for real engineering rotor system, because arbitrary configuration of rotors can be modeled by 3D finite element.
3D point cloud in the evaluation of processes that generate instability of the lumbar spine
José Luis González Gallegos
2015-03-01
Full Text Available OBJECTIVE: To integrate patients with lumbar instability in a multisensor platform in the process of assessment and diagnosis, assigning quantitative parameters for the sagittal balance (SB and muscle function. METHODS: Experimental study involving adult patients diagnosed with diseases that cause alterations in the SB, that were or were not submitted to surgery with posterior instrumentation and fusion. Each patient underwent anthropometric measurements in body composition scale; a kinesiological analysis using a multisensor platform consisting of depth camera to static/dynamic analysis for the quantitative measurement of SB, and surface electromyography to capture the level of abdominal and lumbar muscles activation and through flexion and extension. RESULTS: Seven adult patients: five females (62.5%and two men (37.5% with a mean age 48 years. Images with depth cameras resulted in a SB of from -6.4 to +5.3cm (average -5.7cm. In individuals with positive sagittal balance the percentage of activation (PA of the abdominal muscles was 58.5% and the lower back lumbar was 75.25%; patients with negative SB integrated the PA of the abdominal muscles of 70.25% and lumbar of 65%; the patient with neutral SB exhibited activation of the abdominal muscles of 87.75% and lumbar muscles of 78.25%. CONCLUSIONS: We observed a trend towards positive SB in patients with overweight and obesity by BMI, as well as increased activation of the abdominal muscles. The multi sensor platform is a useful tool for the diagnosis and prognosis of diseases involving sagittal imbalance.
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.
Pecover, J. D.; Chittenden, J. P. [The Centre for Inertial Fusion Studies, The Blackett Laboratory, Imperial College, London SW7 2AZ (United Kingdom)
2015-10-15
A critical limitation of magnetically imploded systems such as magnetized liner inertial fusion (MagLIF) [Slutz et al., Phys. Plasmas 17, 056303 (2010)] is the magneto-Rayleigh-Taylor (MRT) instability which primarily disrupts the outer surface of the liner. MagLIF-relevant experiments have showed large amplitude multi-mode MRT instability growth growing from surface roughness [McBride et al., Phys. Rev. Lett. 109, 135004 (2012)], which is only reproduced by 3D simulations using our MHD code Gorgon when an artificially azimuthally correlated initialisation is added. We have shown that the missing azimuthal correlation could be provided by a combination of the electro-thermal instability (ETI) and an “electro-choric” instability (ECI); describing, respectively, the tendency of current to correlate azimuthally early in time due to temperature dependent Ohmic heating; and an amplification of the ETI driven by density dependent resistivity around vapourisation. We developed and implemented a material strength model in Gorgon to improve simulation of the solid phase of liner implosions which, when applied to simulations exhibiting the ETI and ECI, gave a significant increase in wavelength and amplitude. Full circumference simulations of the MRT instability provided a significant improvement on previous randomly initialised results and approached agreement with experiment.
Pecover, J. D.; Chittenden, J. P.
2015-10-01
A critical limitation of magnetically imploded systems such as magnetized liner inertial fusion (MagLIF) [Slutz et al., Phys. Plasmas 17, 056303 (2010)] is the magneto-Rayleigh-Taylor (MRT) instability which primarily disrupts the outer surface of the liner. MagLIF-relevant experiments have showed large amplitude multi-mode MRT instability growth growing from surface roughness [McBride et al., Phys. Rev. Lett. 109, 135004 (2012)], which is only reproduced by 3D simulations using our MHD code Gorgon when an artificially azimuthally correlated initialisation is added. We have shown that the missing azimuthal correlation could be provided by a combination of the electro-thermal instability (ETI) and an "electro-choric" instability (ECI); describing, respectively, the tendency of current to correlate azimuthally early in time due to temperature dependent Ohmic heating; and an amplification of the ETI driven by density dependent resistivity around vapourisation. We developed and implemented a material strength model in Gorgon to improve simulation of the solid phase of liner implosions which, when applied to simulations exhibiting the ETI and ECI, gave a significant increase in wavelength and amplitude. Full circumference simulations of the MRT instability provided a significant improvement on previous randomly initialised results and approached agreement with experiment.
Development of the electrothermal instability from resistive inclusions
Yu, Edmund; Awe, T. J.; Bauer, B. S.; Yates, K. C.; Yelton, W. G.; Hutchinson, T. M.; Fuelling, S.; McKenzie, B. B.; Peterson, K. J.
2016-10-01
The magneto Rayleigh-Taylor (MRT) instability limits the performance of all magnetically imploded systems. In the case of compressing metal liners, as in the magnetized liner inertial fusion concept, a dominant seed for MRT is believed to be the electrothermal instability (ETI). Here, linear theory predicts the most unstable mode manifests as horizontal (i.e. perpendicular to current flow) bands of heated and expanded metal. However, how do such bands, known as striations, actually develop from a smooth metal surface? Recent experiments on ETI evolution, performed at the University of Nevada, Reno, provide a possible answer: pre-shot characterization of aluminum rods show numerous resistive inclusions, several microns in diameter and distributed throughout the rod. In this work, we use 3D MHD simulation and analytic theory to explore how current redistribution around these isolated inclusions, combined with ETI, can lead to rapid formation of the global striation structures. Later in time, striations expand and form density perturbations much larger than the initial inclusion size. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the National Nuclear Security Administration under DE-AC04-94AL85000.
Lyra, Wladimir
2012-01-01
It has been suggested that the transition between magnetorotationally active and dead zones in protoplanetary disks should be prone to the excitation of vortices via Rossby wave instability (RWI). However, the only numerical evidence for this has come from alpha disk models, where the magnetic field evolution is not followed, and the effect of turbulence is parametrized by Laplacian viscosity. We aim to establish the phenomenology of the flow in the transition in 3D resistive-magnetohydrodynamical models. We model the transition by a sharp jump in resistivity, as expected in the inner dead zone boundary, using the Pencil Code to simulate the flow. We find that vortices are readily excited in the dead side of the transition. We measure the mass accretion rate finding similar levels of Reynolds stress at the dead and active zones, at the $\\alpha\\approx 10^{-2}$ level. The vortex sits in a pressure maximum and does not migrate, surviving until the end of the simulation. A pressure maximum in the active zone also...
The dynamics of neutrino-driven supernova explosions after shock revival in 2D and 3D
Müller, B.
2015-10-01
We study the growth of the explosion energy after shock revival in neutrino-driven explosions in two and three dimensions (2D/3D) using multi-group neutrino hydrodynamics simulations of an 11.2 M⊙ star. The 3D model shows a faster and steadier growth of the explosion energy and already shows signs of subsiding accretion after one second. By contrast, the growth of the explosion energy in 2D is unsteady, and accretion lasts for several seconds as confirmed by additional long-time simulations of stars of similar masses. Appreciable explosion energies can still be reached, albeit at the expense of rather high neutron star masses. In 2D, the binding energy at the gain radius is larger because the strong excitation of downward-propagating g modes removes energy from the freshly accreted material in the downflows. Consequently, the mass outflow rate is considerably lower in 2D than in 3D. This is only partially compensated by additional heating by outward-propagating acoustic waves in 2D. Moreover, the mass outflow rate in 2D is reduced because much of the neutrino energy deposition occurs in downflows or bubbles confined by secondary shocks without driving outflows. Episodic constriction of outflows and vertical mixing of colder shocked material and hot, neutrino-heated ejecta due to Rayleigh-Taylor instability further hamper the growth of the explosion energy in 2D. Further simulations will be necessary to determine whether these effects are generic over a wider range of supernova progenitors.
Gigli, Giovanni; Margottini, Claudio; Spizzichino, Daniele; Ruther, Heinz; Casagli, Nicola
2016-04-01
released, stratigraphic setting and tectonic activity can be recognized. As a consequence, rock-falls have been occurring, even recently, with unstable rock mass volumes ranging from 0.1 m3 up to over some hundreds m3. Slope instability, acceleration of crack deformation and consequent increasing of rock-fall hazard conditions, could threaten the safety of tourist as well as the integrity of the heritage. 3D surface model coming from Terrestrial Laser Scanner acquisitions was developed almost all over the site of Petra, including the Siq. Comprehensively, a point cloud of five billion points was generated making the site of Petra likely the largest scanned archaeological site in the word. As far as the Siq, the scanner was positioned on the path floor at intervals of not more than 10 meters from each station. The total number of scans in the Siq was 220 with an average point cloud interval of approximately 3 cm. Subsequently, for the definition of the main rockfall source areas, a spatial kinematic analysis for the whole Siq has been performed, by using discontinuity orientation data extracted from the point cloud by means of the software Diana. Orientation, number of sets, spacing/frequency, persistence, block size and scale dependent roughness was obtained combining fieldwork and automatic analysis. This kind of analysis is able to establish where a particular instability mechanism is kinematically feasible, given the geometry of the slope, the orientation of discontinuities and shear strength of the rock. The final outcome of this project was a detail landslide kinematic index map, reporting main potential instability mechanisms for a given area. The kinematic index was finally calibrated for each instability mechanism (plane failure; wedge failure; block toppling; flexural toppling) surveyed in the site. The latter is including the collapse occurred in May 2015, likely not producing any victim, in a sector clearly identified by the susceptibility maps produced by the
Hernandez, Karina; Mitchell, Neil; Huuse, Mads
2016-04-01
At ~255 Ma, cycles of evaporation of seawater led to deposition of evaporites including halite (rock salt) in the North Sea Basin. After later burial by denser sediments, the salt beds rose as pillows and diapirs. Assuming mobilization is due to Rayleigh-Taylor gravitational instability of heavy fluid (sediments) overlying light fluid (salts), theory suggests that the spacing between diapirs should be proportional to the original thickness of the salt layer. For example, a description of the theory in Turcotte and Schubert (1982) predicts structure wavelength to be 2.6 times the salt thickness. Previous research has explored mobilization of salt deposits assuming they have uniform rheology. However, this is not justified as halite rheology varies with temperature, grain size and pore brine content. Furthermore, evaporitic sequences contain various minerals besides halite (e.g., anhydrite, gypsum), which have different rheological properties. 3D seismic and well data reveal the internal structure of salt beds. The data have allowed characterization of structure wavelengths and salt thickness, so that the impact of internal composition and other properties on halokinetic behaviour can be assessed.
Pecover, James; Chittenden, Jeremy
2015-11-01
Magnetized liner inertial fusion (MagLIF) is a promising route to controlled thermonuclear fusion. The concept involves magnetically imploding a metal liner containing fuel with an azimuthal magnetic field (Bz) ; a key limitation of such systems is the magneto-Rayleigh-Taylor (MRT) instability. MagLIF relevant liner implosions with Bz = 0 carried out at SNL showed high amplitude MRT growth; we present a quantitative comparison between experimental results and 3D results from our MHD code Gorgon, demonstrating closer agreement for the MRT properties with the inclusion of electro-thermal and electro-choric instabilities (ETI and ECI) and material strength. The ETI and ECI result in early time azimuthally correlated structures which provide a seed for the MRT. Material strength increases the ETI amplitude due to positive feedback during the solid phase of the liner. Similar liner implosions with Bz exhibited a re-orientation of the MRT into helical structures, which are yet to be reproduced by simulations without an artificial helical initialisation. Our 3D Gorgon results with Bz show helices prior to vapourisation; these occur at initially positive angles before changing sign, tending to zero later in time. This angle does not follow the relative magnitudes of Bz and Bθ as would be expected for the MRT. The angle instead follows the ratio of axial and azimuthal currents (induced by compression or rarefaction of the initial Bz) , indicating an electro-thermal origin.
Pecover, James; Weinwurm, Marcus; Chittenden, Jeremy
2014-10-01
Magnetized liner inertial fusion (MagLIF) is a promising route to controlled thermonuclear fusion. The concept involves magnetically imploding a metal liner; a key limitation of such systems is the magneto-Rayleigh-Taylor (MRT) instability. MagLIF relevant liner implosions carried out at Sandia showed high amplitude MRT growth. 3D simulations with our MHD code Gorgon have shown that azimuthal correlation required to explain this can be contributed to by early time effects the electro-thermal instability (ETI) and an ``electro-choric instability'' (ECI). Shear forces can damp short wavelength perturbations while the liner remains solid, potentially setting axial wavelengths for the ETI and ECI. We can now model shear stresses in solids with Gorgon using a Johnson-Cook strength model and a bulk modulus calculated from the FEOS equation of state. Gorgon results with the strength model are compared to results from the shock hydrodynamics code iSALE. Results for liners show elongation of perturbations at the outer edge relative to the case without strength. We present results showing the model applied to liner implosions with axial magnetic fields of 0 T and 10 T.
Three-dimensional simulations of ablative hydrodynamic instabilities in indirectly driven targets
Marinak, M.M.; Tipton, R.E.; Remington, B.A. [and others
1996-06-01
To model ignition in a National Ignition Facility (NIF) capsule implosion, the authors must understand the behavior of instabilities that can cause breakup of the pellet shell. During a capsule implosion, shocks that transit the shell cause growth of perturbations at the surface or at an interface because of a Richtmyer-Meshkov type of instability. Following shock breakout, or earlier for a shaped pulse, the low-density ablated plasma accelerates the pusher, and the ablation front is Rayleigh-Taylor (RT) unstable. Ablation and finite density gradients have the effect of stabilizing the short wavelength modes. Unstable modes present on the outer surface grow and feed through to the inner surface. Once the shell encounters the rebounding shock from the capsule center, it decelerates and the inner surface becomes RT unstable. If perturbations grow large enough, pusher material mixes into the core, degrading implosion performance. Capsule designs for the NIF depend on ablative stabilization and saturation to prevent perturbations initially present on the capsule surface from growing large enough to quench ignition. Here, the authors examine the first simulations and experiments to study the effect of 3-D perturbation shape on instability growth and saturation in indirectly driven targets. The first section discusses HYDRA, the radiation hydrodynamics code developed for these simulations. The subsequent section examines 3-D shape effects in single-mode perturbations in planar foil simulations and experiments. A discussion of the evolution of multimode perturbations on planar foils is followed by a discussion of 3-D simulations of instability growth in Nova capsule implosions.
Morphology and Dynamics of Lithospheric Body Force Instabilities: Sheets, Drips and In-Between
Beall, A.; Moresi, L. N.
2014-12-01
Foundering of the Earth's lithosphere, and consequent energy and mass flux across the upper boundary layer and mantle interface, is driven locally by gravitational body forces. The related instabilities are usually classified as having sheet-like or drip-like morphologies. The former is associated with whole lithosphere (subduction) or delamination type foundering such as suggested for beneath the southern Sierra-Nevada and the Colorado Plateau, the latter to classic Rayleigh-Taylor instability below an upper layer, suggested to have occurred beneath the Tibetan Plateau and North Island, New Zealand. This dichotomy is non-trivial; classification of phenomena into one or the other is often debated and is difficult to infer from observables. The two morphologies are most likely end-members. Here I refine the dynamics driving morphology selection as a function of rheological lamination and boundary layer Rayleigh number in 2D and 3D, using the finite-element particle-in-cell code Underworld. I explore the influence of morphology on mass flux, topography and crustal deformation as well as deviation from classic 2D scalings. Additionally, tectonic displacement interference with instability development is discussed using basic 3D shear-box style models. By quantifying and describing the theoretical instability dynamics which could result in a plausible range of morphological expressions, I aim to build a general framework which can be paired to the discussion involving firstly, the recognition of varied styles of body force instabilities in the modern Earth and rock record and secondly, to what degree pattern selection impacts boundary layer mass and energy flux.
Sedimentation and gravitational instability of Escherichia coli Suspension
Douarche, Carine; Salin, Dominique; Collaboration between Laboratory FAST; LPS Collaboration
2016-11-01
The successive run and tumble of Escherichia coli bacteria provides an active matter suspension of rod-like particles with a large swimming diffusion. As opposed to inactive elongated particles, this diffusion prevents clustering and instability in the gravity field. We measure the time dependent E . coli concentration profile during their sedimentation. After some hours, due to the dioxygen consumption, a motile / non-motile front forms leading to a Rayleigh-Taylor type gravitational instability. Analyzing both sedimentation and instability in the framework of active particle suspensions, we can measure the relevant bacteria hydrodynamic characteristics such as its single particle sedimentation velocity and its hindrance volume.
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
Mitrovic, S.; Fazekas, P.; Søndergaard, C.; Ariosa, D.; Barišić, N.; Berger, H.; Cloëtta, D.; Forró, L.; Höchst, H.; Kupčić, I.; Pavuna, D.; Margaritondo, G.
2007-04-01
The correlated 3d sulphide BaVS3 exhibits an interesting coexistence of one-dimensional and three-dimensional properties. Our experiments determine the electronic band structure and shed light on this puzzle. High-resolution angle-resolved photoemission measurements in a 4-eV -wide range below the Fermi energy level uncover and investigate the coexistence of a1g wide-band and eg narrow-band d electrons, which lead to the complicated electronic properties of this material. We explore the effects of strong correlations and the Fermi surface instability associated with the metal-insulator transition.
Interfacial instabilities and Kapitsa pendula
Krieger, Madison
2015-11-01
Determining the critera for onset and amplitude growth of instabilities is one of the central problems of fluid mechanics. We develop a parallel between the Kapitsa effect, in which a pendulum subject to high-frequency low-amplitude vibrations becomes stable in the inverted position, and interfaces separating fluids of different density. It has long been known that such interfaces can be stabilized by vibrations, even when the denser fluid is on top. We demonstrate that the stability diagram for these fluid interfaces is identical to the stability diagram for an appopriate Kapitsa pendulum. We expand the robust, ``dictionary''-type relationship between Kapitsa pendula and interfacial instabilities by considering the classical Rayleigh-Taylor, Kelvin-Helmholtz and Plateau instabilities, as well as less-canonical examples ranging in scale from the micron to the width of a galaxy.
Boulet, M.; Griffond, J. [CEA Bruyeres-le-Chatel, Dept. Sciences de la Simulation et de l' Information, 91 (France)
2004-07-01
Occurrence of a secondary instability developing after the Richtmyer-Meshkov (primary) instability is emphasized thanks to numerical simulations with the TRICLADE code. We are mainly considering 2D perturbations describes by trigonometric function cosine or [cosine]. However, the 3D case is also tackled. The sinuous secondary instability is characterized by the loss of the symmetries in the direction normal to the interface at its crests. It reduces the late time growing rate of the 'mushrooms' formed by the Richtmyer-Meshkov instability. Related simplified problems, like symmetrical Riemann problems or the Mallier-Maslowe array of counter-rotating vortices, allow us to perform 2D linear stability analysis. Thus, we show that the sinuous secondary instability is not a numerical artifact and that is comes from the continuous incompressible velocity field in the interface region. This instability implies temporal limitations for the validity of single mode simulations; therefore multimode simulations are necessary to study the ]ate-time behaviour of interfaces bitted by shocks. (authors)
Instability, Turbulence, and 3D Magnetic Reconnection in a Line-Tied, Zero Net Current Screw Pinch
Brookhart, Matthew I.; Stemo, Aaron; Zuberbier, Amanda; Zweibel, Ellen; Forest, Cary B.
2015-04-01
This Letter reports the first experimental investigation into a line-tied plasma with a reversed current profile. Discrete current sources create a cylindrical plasma equilibrium with an axial field and zero net current. Detailed magnetic measurements show that an internal m =1 mode with no external character grows exponentially. The nonlinear evolution of the mode drives 3D reconnection events that reorganize the plasma equilibrium. The plasma is turbulent and exhibits reconnection events on a range of scales. These data are consistent with recent simulations of coronal loops and the nanoflare coronal heating mechanism.
Instability, turbulence, and 3D magnetic reconnection in a line-tied, zero net current screw pinch.
Brookhart, Matthew I; Stemo, Aaron; Zuberbier, Amanda; Zweibel, Ellen; Forest, Cary B
2015-04-10
This Letter reports the first experimental investigation into a line-tied plasma with a reversed current profile. Discrete current sources create a cylindrical plasma equilibrium with an axial field and zero net current. Detailed magnetic measurements show that an internal m=1 mode with no external character grows exponentially. The nonlinear evolution of the mode drives 3D reconnection events that reorganize the plasma equilibrium. The plasma is turbulent and exhibits reconnection events on a range of scales. These data are consistent with recent simulations of coronal loops and the nanoflare coronal heating mechanism.
Hwang, Alex D; Peli, Eli
2014-01-01
Watching 3D content using a stereoscopic display may cause various discomforting symptoms, including eye strain, blurred vision, double vision, and motion sickness. Numerous studies have reported motion-sickness-like symptoms during stereoscopic viewing, but no causal linkage between specific aspects of the presentation and the induced discomfort has been explicitly proposed. Here, we describe several causes, in which stereoscopic capture, display, and viewing differ from natural viewing resulting in static and, importantly, dynamic distortions that conflict with the expected stability and rigidity of the real world. This analysis provides a basis for suggested changes to display systems that may alleviate the symptoms, and suggestions for future studies to determine the relative contribution of the various effects to the unpleasant symptoms.
Begg, J; Taylor, M L; Holloway, L; Kron, T; Franich, R D
2014-12-01
Temporally varying light intensity during acquisition of projection images in an optical CT scanner can potentially be misinterpreted as physical properties of the sample. This work investigated the impact of LED light source intensity instability on measured attenuation coefficients. Different scenarios were investigated by conducting one or both of the reference and data scans in a 'cold' scanner, where the light source intensity had not yet stabilised. Uniform samples were scanned to assess the impact on measured uniformity. The orange (590 nm) light source decreased in intensity by 29 % over the first 2 h, while the red (633 nm) decreased by 9 %. The rates of change of intensity at 2 h were 0.1 and 0.03 % respectively over a 5 min period-corresponding to the scan duration. The normalisation function of the reconstruction software does not fully account for the intensity differences and discrepancies remain. Attenuation coefficient inaccuracies of up to 8 % were observed for data reconstructed from projection images acquired with a cold scanner. Increased noise was observed for most cases where one or both of the scans was acquired without sufficient warm-up. The decrease in accuracy and increase in noise were most apparent for data reconstructed from reference and data scans acquired with a cold scanner on different days.
Xu, Qian; Krivets, Vitaliy V.; Sewell, Everest G.; Jacobs, Jeffrey W.
2016-11-01
A vertical shock tube is used to perform experiments on the single-mode three-dimensional Richtmyer-Meshkov Instability (RMI). The light gas (Air) and the heavy gas (SF6) enter from the top and the bottom of the shock tube driven section to form the interface. The initial perturbation is then generated by oscillating the gases vertically. Both gases are seeded with particles generated through vaporizing propylene glycol. An incident shock wave (M 1.2) impacts the interface to create an impulsive acceleration. The seeded particles are illuminated by a dual cavity 75W, Nd: YLF laser. Three high-speed CMOS cameras record time sequences of image pairs at a rate of 2 kHz. The initial perturbation used is that of a single, square-mode perturbation with either a single spike or a single bubble positioned at the center of the shock tube. The full time dependent velocity field is obtained allowing the determination of the circulation versus time. In addition, the evolution of time dependent amplitude is also determined. The results are compared with PIV measurements from previous two-dimensional single mode experiments along with PLIF measurements from previous three-dimensional single mode experiments.
Wang, Zhenyu; Lin, Yu; Wang, Xueyi; Tummel, Kurt; Chen, Liu
2016-07-01
The eigenmode stability properties of three-dimensional lower-hybrid-drift-instabilities (LHDI) in a Harris current sheet with a small but finite guide magnetic field have been systematically studied by employing the gyrokinetic electron and fully kinetic ion (GeFi) particle-in-cell (PIC) simulation model with a realistic ion-to-electron mass ratio mi/me . In contrast to the fully kinetic PIC simulation scheme, the fast electron cyclotron motion and plasma oscillations are systematically removed in the GeFi model, and hence one can employ the realistic mi/me . The GeFi simulations are benchmarked against and show excellent agreement with both the fully kinetic PIC simulation and the analytical eigenmode theory. Our studies indicate that, for small wavenumbers, ky, along the current direction, the most unstable eigenmodes are peaked at the location where k →.B → =0 , consistent with previous analytical and simulation studies. Here, B → is the equilibrium magnetic field and k → is the wavevector perpendicular to the nonuniformity direction. As ky increases, however, the most unstable eigenmodes are found to be peaked at k →.B → ≠0 . In addition, the simulation results indicate that varying mi/me , the current sheet width, and the guide magnetic field can affect the stability of LHDI. Simulations with the varying mass ratio confirm the lower hybrid frequency and wave number scalings.
Interfacial fluid instabilities and Kapitsa pendula
Krieger, Madison Ski
2015-01-01
The onset and development of instabilities is one of the central problems in fluid mechanics. Here we develop a connection between instabilities of free fluid interfaces and inverted pendula. When acted upon solely by the gravitational force, the inverted pendulum is unstable. This position can be stabilised by the Kapitsa phenomenon, in which high-frequency low-amplitude vertical vibrations of the base creates a fictitious force which opposes the gravitational force. By transforming the dynamical equations governing a fluid interface into an appropriate pendulum, we demonstrate how stability can be induced in fluid systems by properly tuned vibrations. We construct a "dictionary"-type relationship between various pendula and the classical Rayleigh-Taylor, Kelvin-Helmholtz, Rayleigh-Plateau and the self-gravitational instabilities. This makes several results in control theory and dynamical systems directly applicable to the study of "tunable" fluid instabilities, where the critical wavelength depends on the e...
Miles, Aaron
2004-11-01
In this talk we discuss the nature of late-time, broad-banded instability development at an interface when a strong blast wave travels from a heavier to lighter fluid, as is the case in a supernova explosion. After a short period of Richtmyer-Meshkov growth, the interface is unstable via the Rayleigh-Taylor mechanism, which rapidly becomes the dominant energy source for growth. This situation is distinct from the classical case in two important ways, both of which can be understood in terms of a bubble merger model we have developed for blast-wave-driven systems. Rather than the constant acceleration feeding the instability to spawn ever larger scales and accelerate the growth, the decaying acceleration in the blast-wave case leads to a decay in the RT growth rate, and a freezing in of a preferred largest scale, which is dependent on the precise details of the system. In the language of bubble-merger models, this can be understood in terms of the time for the generation of the next largest scale being longer than the lifetime of the blast wave. Secondly, the continual expansion behind the blast front precludes the emergence of a self-similar regime, independent of the initial conditions, in the planar case. Self-similarity may be recovered in diverging systems but may be difficult to observe in reality because of rather restrictive conditions that must be met. These observations are borne out by hi-resolution numerical simulations using the higher order Godunov AMR hydrocode Raptor in 2 and 3D, and explain other simulations of instability growth in supernovae explosions; the initial "interfacial" structure is likely very important in determining the late-time growth. The model predictions are also consistent with numerous images of natural and manmade explosions.
MORPHOLOGY AND DYNAMICS OF SOLAR PROMINENCES FROM 3D MHD SIMULATIONS
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.
EFFECTS OF DIFFERENT NUMERICAL INTERFACE METHODS ON HYDRODYNAMICS INSTABILITY
FRANCOIS, MARIANNE M. [Los Alamos National Laboratory; DENDY, EDWARD D. [Los Alamos National Laboratory; LOWRIE, ROBERT B. [Los Alamos National Laboratory; LIVESCU, DANIEL [Los Alamos National Laboratory; STEINKAMP, MICHAEL J. [Los Alamos National Laboratory
2007-01-11
The authors compare the effects of different numerical schemes for the advection and material interface treatments on the single-mode Rayleigh-Taylor instability, using the RAGE hydro-code. The interface growth and its surface density (interfacial area) versus time are investigated. The surface density metric shows to be better suited to characterize the difference in the flow, than the conventional interface growth metric. They have found that Van Leer's limiter combined to no interface treatment leads to the largest surface area. Finally, to quantify the difference between the numerical methods they have estimated the numerical viscosity in the linear-regime at different scales.
Mitigation of Electrothermal Instabilities with Thick Insulating Coatings
Peterson, Kyle; Awe, Thomas; Yu, Edmund; Sinars, Daniel; Cuneo, Michael
2013-10-01
We will show results of recent experiments on Sandia's Z facility that demonstrate a dramatic reduction in instability growth when thick insulating coatings are used to mitigate electrothermal instability growth in magnetically driven imploding liners. These results also provide further evidence that the inherent surface roughness as a result of target fabrication is not the dominant seed for the growth of Magneto-Rayleigh-Taylor (MRT) instabilities in liners with carefully machined smooth surfaces (~100 nm surface RMS or better), but rather electrothermal instabilities that form early in the electrical current pulse as Joule heating melts and vaporizes the liner surface. More importantly, these results suggest a mechanism for possibly reducing the integral MRT instability growth substantially in magnetically driven inertial confinement fusion concepts such as MagLIF. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
Malcolm J. Andrews
2006-04-14
This project had two major tasks: Task 1. The construction of a new air/helium facility to collect detailed measurements of Rayleigh-Taylor (RT) mixing at high Atwood number, and the distribution of these data to LLNL, LANL, and Alliance members for code validation and design purposes. Task 2. The collection of initial condition data from the new Air/Helium facility, for use with validation of RT simulation codes at LLNL and LANL. This report describes work done in the last twelve (12) months of the project, and also contains a summary of the complete work done over the three (3) life of the project. As of April 1, 2006, the air/helium facility (Task 1) is now complete and extensive testing and validation of diagnostics has been performed. Initial condition studies (Task 2) is also comp lete. Detailed experiments with air/helium with Atwood numbers up to 0.1 have been completed, and Atwood numbers of 0.25. Within the last three (3) months we have been able to successfully run the facility at Atwood numbers of 0.5. The progress matches the project plan, as does the budget. We have finished the initial condition studies using the water channel, and this work has been accepted for publication on the Journal of Fluid Mechanics (the top fluid mechanics journal). Mr. Nick Mueschke and Mr. Wayne Kraft are continuing with their studies to obtain PhDs in the same field, and will also continue their collaboration visits to LANL and LLNL. Over its three (3) year life the project has supported two(2) Ph.D.’s and three (3) MSc’s, and produced nine (9) international journal publications, twenty four (24) conference publications, and numerous other reports. The highlight of the project has been our close collaboration with LLNL (Dr. Oleg Schilling) and LANL (Drs. Dimonte, Ristorcelli, Gore, and Harlow).
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...
Awe, Thomas
2013-10-01
Magnetically driven implosions provide an energy-rich platform for inertial confinement fusion. The magnetized liner inertial fusion concept (MagLIF, Slutz et al., Phys. Plasmas 17, 056303 (2010)) uses a pulsed-power-driven metallic liner to compress and inertially confine preheated and premagnetized fusion fuel. The fuel is premagnetized with a uniform axial seed field Bz , 0 of 10 to 30 T, which is then compressed by the liner to nearly 1000 T. In the fuel, the ultra-high field reduces thermal conduction and enhances alpha-particle heating. Preheating the fuel to 100-300 eV eases requirements on liner-convergence; nonetheless, convergence ratios at stagnation of 20 or more may be necessary. The ability to maintain liner stability and uniformity through stagnation may ultimately determine the success of the MagLIF concept. The integrity of magnetically imploded liners is compromised both by electrode instabilities and by the magneto-Rayleigh Taylor (MRT) instability. Electrode instabilities form local perturbations that can mix liner material into the fuel prior to bulk compression. Recent experiments on the Z facility have shown that this instability is mitigated when the liner's ends implode onto a nylon ``cushion,'' which impedes local perturbation growth. Other recent experiments have, for the first time, studied the implosion dynamics of premagnetized (Bz , 0 > 0) MagLIF-type liners. When seeded with a 7 or 10 T axial field, these liners developed 3D-helix-like surface instabilities; such instabilities starkly contrast with the azimuthally-correlated MRT instabilities that have been consistently observed in many earlier unmagnetized (Bz , 0 = 0 T) experiments. Quite unexpectedly, the helical structure persisted throughout the implosion, even though the azimuthal drive field greatly exceeded the expected axial field at the liner surface for all but the earliest stages of the experiment. Thus far, no self-consistent model has reproduced this fundamentally 3D
Transverse electron-scale instability in relativistic shear flows
Alves, E P; Fonseca, R A; Silva, L O
2015-01-01
Electron-scale surface waves are shown to be unstable in the transverse plane of a shear flow in an initially unmagnetized plasma, unlike in the (magneto)hydrodynamics case. It is found that these unstable modes have a higher growth rate than the closely related electron-scale Kelvin-Helmholtz instability in relativistic shears. Multidimensional particle-in-cell simulations verify the analytic results and further reveal the emergence of mushroom-like electron density structures in the nonlinear phase of the instability, similar to those observed in the Rayleigh Taylor instability despite the great disparity in scales and different underlying physics. Macroscopic ($\\gg c/\\omega_{pe}$) fields are shown to be generated by these microscopic shear instabilities, which are relevant for particle acceleration, radiation emission and to seed MHD processes at long time-scales.
Llor, A
2001-07-01
Theoretical criteria are defined to perform quick analytical evaluations of statistical hydro models for turbulent mixing flows induced by Kelvin-Helmholtz, Rayleigh-Taylor and Richtmyer-Meshkov instabilities. They are based on a global energy balance analysis of the mixing zone ('0D' projection) in the limit of zero Atwood number, for incompressible fluids, and in self-similar regime. It is then shown that single-fluid descriptions must be replaced by two-fluid descriptions, particularly for the Rayleigh-Taylor case with variable acceleration. The interaction between a shock and heterogeneities is also considered. Various approaches for the development of new models are finally given. (author)
Two-Fluid Interface Instability Being Studied
Niederhaus, Charles E.
2003-01-01
The interface between two fluids of different density can experience instability when gravity acts normal to the surface. The relatively well known Rayleigh-Taylor (RT) instability results when the gravity is constant with a heavy fluid over a light fluid. An impulsive acceleration applied to the fluids results in the Richtmyer-Meshkov (RM) instability. The RM instability occurs regardless of the relative orientation of the heavy and light fluids. In many systems, the passing of a shock wave through the interface provides the impulsive acceleration. Both the RT and RM instabilities result in mixing at the interface. These instabilities arise in a diverse array of circumstances, including supernovas, oceans, supersonic combustion, and inertial confinement fusion (ICF). The area with the greatest current interest in RT and RM instabilities is ICF, which is an attempt to produce fusion energy for nuclear reactors from BB-sized pellets of deuterium and tritium. In the ICF experiments conducted so far, RM and RT instabilities have prevented the generation of net-positive energy. The $4 billion National Ignition Facility at Lawrence Livermore National Laboratory is being constructed to study these instabilities and to attempt to achieve net-positive yield in an ICF experiment.
Progress toward Kelvin-Helmholtz instabilities in a High-Energy-Density Plasma on the Nike laser
Harding, E. C.; Drake, R. P.; Gillespie, R. S.; Grosskopf, M. J.; Huntington, C. M.; Aglitskiy, Y.; Weaver, J. L.; Velikovich, A. L.; Plewa, T.; Dwarkadas, V. V.
2008-04-01
In the realm of high-energy-density (HED) plasmas, there exist three primary hydrodynamic instabilities of concern: Rayleigh-Taylor (RT), Richtmyer-Meshkov (RM), and Kelvin-Helmholtz (KH). Although the RT and the RM instabilities have been readily observed and diagnosed in the laboratory, the KH instability remains relatively unexplored in HED plasmas. Unlike the RT and RM instabilities, the KH instability is driven by a lifting force generated by a strong velocity gradient in a stratified fluid. Understanding the KH instability mechanism in HED plasmas will provide essential insight into oblique shock systems, jets, mass stripping, and detailed RT-spike development. In addition, our KH experiment will help provide the groundwork for future transition to turbulence experiments. We present 2D FLASH simulations and experimental data from our initial attempts to create a pure KH system using the Nike laser at the Naval Research Laboratory.
Hydrodynamic Instability Experiments at the GEKKO XII/HIPER Laser
Azechi, Hiroshi; Nakai, Mitsuo; Shiraga, Hiroyuki; Miyanaga, Noriaki; Shigemori, Keisuke; Nishikino, Masaharu; Sakaiya, Tatsuro; Nishimura, Hiroaki; Fujita, Kazuhisa; Kang, Young-Gwang; Nagatomo, Hideo; Nishihara, Katsunobu; Yamanaka, Tatsuhiko
2000-10-01
We have constructed the HIPER laser system that combines all 12 beams of the existing GEKKO XII laser to irradiate a target from one side.The laser pulse in standard operation consists of partially coherent light for foot (green) and two-dimensional SSD for main drive (blue). We will test in the first series of experiment the ablation pressure and its uniformity, ablative Rayleigh-Taylor instability, and instability at explosion phase.\\x81@ Although the primary objective is to test hydrodynamic stability of an ignition target (both in fast ignition and conventional self-ignition), the HIPER laser is expected to be a major tool for a number of high energy-density physics, such as laboratory astrophysics, equation-of-state study.
Numerical analysis of anisotropic diffusion effect on ICF hydrodynamic instabilities
Olazabal-Loumé M.
2013-11-01
Full Text Available The effect of anisotropic diffusion on hydrodynamic instabilities in the context of Inertial Confinement Fusion (ICF flows is numerically assessed. This anisotropy occurs in indirect-drive when laminated ablators are used to modify the lateral transport [1,2]. In direct-drive, non-local transport mechanisms and magnetic fields may modify the lateral conduction [3]. In this work, numerical simulations obtained with the code PERLE [4], dedicated to linear stability analysis, are compared with previous theoretical results [5]. In these approaches, the diffusion anisotropy can be controlled by a characteristic coefficient which enables a comprehensive study. This work provides new results on the ablative Rayleigh-Taylor (RT, ablative Richtmyer-Meshkov (RM and Darrieus-Landau (DL instabilities.
Waves, instabilities and turbulence properties in Depolarisation Fronts
Lapenta, Giovanni; Goldman, Martin; Newman, David L.; Olshevskyi, Vyacheslav; Eastwood, Jonathan; Divin, Andrey; Pucci, Francesco
2016-04-01
The new mission MMS is currently focusing on the magnetopause but we need to be ready for the study of the tail. An aspect of great importance there are the Dipolarization fronts (DF), formed by reconnection outflows interacting with the pre-existing environment. These regions are host of important energy and wave phenomena [1-3]. Our recent work has investigated these regions via fully kinetic 3D simulations [4-5]. 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 develops 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 and the onset of waves and secondary instabilities, transitioning towards a turbulent state. We investigate here especially the wave signatures that are observed in fully 3D simulations, looking for signatures of interchange-type lower hybrid waves [8], of whistler waves [7]. The end result present a vast array of waves and it is best analysed relying on concepts mutated by the turbulence theory. The end result of these waves and particle flows [2,6] are energy exchanges. We evaluate the different terms of the energy exchanges (energy deposition, J.E, and energy fluxes) and evaluate their relative improtance. The results presented are contrasted against existing results [1,9] and will provided useful guidance in analysis of future MMS data. [1] Hamrin, Maria, et al. "The evolution of flux pileup regions in the plasma sheet: Cluster observations." Journal of Geophysical Research: Space Physics 118.10 (2013): 6279-6290. [2] Angelopoulos, V., et al. "Electromagnetic energy conversion at reconnection fronts." Science 341.6153 (2013): 1478-1482. [3] Zhou, Meng, et al. "THEMIS observation of multiple
Michoud, Clément; Baillifard, François; Harald Blikra, Lars; Derron, Marc-Henri; Jaboyedoff, Michel; Kristensen, Lene; Leva, Davide; Metzger, Richard; Rivolta, Carlo
2014-05-01
Terrestrial Laser Scanning and Ground-Based Radar Interferometry have changed our perception and interpretation of slope activities for the last 20 years and are now routinely used for monitoring and even early warning purposes. Terrestrial LiDAR allows indeed to model topography with very high point density, even in steep slopes, and to extract 3D displacements of rock masses by comparing successive datasets. GB-InSAR techniques are able to detect mm displacements over large areas. Nevertheless, both techniques suffer of some limitations. The precision of LiDAR devices actually limits its ability to monitor very slow-moving landslides, as well as by the dam resolution and the particular geometry (in azimuth/range) of GB-InSAR data may complicate their interpretations. To overcome those limitations, tools were produced to truly combine strong advantages of both techniques, by coupling high resolution geometrical data from terrestrial LiDAR or photogrammetry with high precision displacement time series from GB-InSAR. We thus developed a new exportation module into the processing chain of LiSAmobile (GB-InSAR) devices in order to wrap radar results from their particular geometry on high resolution 3D point clouds with cm mean point spacing. Furthermore, we also added new importation and visualization functionalities into Coltop3D (software for geological interpretations of laser scanning data) to display those results in 3D and even analyzing displacement time series. This new method has also been optimized to create as few and small files as possible and for time processing. Advantages of coupling terrestrial LiDAR and GB-InSAR data will be illustrated on the La Perraire instability, an active large rockslide involving frequent rockfalls and threatening inhabitant within the Val de Bagnes in the Swiss Alps. This rock mass, monitored by LiDAR and GPS since 2006, is huge enough and long-term movements are big (up to 1.6 m in 6 years) and complex enough to make
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.
Long term instability growth of radiatively driven thin planar shells
Mason, R.J.; Hollowell, D.E. [and others
2000-10-01
The authors study Rayleigh-Taylor instability of radiatively driven thin copper foils under pure ablation, as well as with beryllium tampers to provide additional pressure drive. Modeling was done with the RAGE adaptive mesh refinement code of experiments done on the NOVA and OMEGA lasers. The copper foils were typically 11.5 {micro}m thick with 0.45 {micro}m amplitude, 45 {micro}m wavelength cosine surface perturbations. The beryllium layer was 5 {micro}m thick. The drive was a P26-like laser pulse delivering a peak 160-185 eV radiation temperatures. Good agreement between experiment and simulation has been obtained out to 4.5 ns. Mechanisms for late time agreement are discussed.
Rao, Pooja; She, Dan; Lim, Hyunkyung; Glimm, James
2015-11-01
The qualitative and quantitative effect of initial conditions (linear and non-linear) and high Mach number (1.3 and 1.45) is studied on the turbulent mixing induced by the Richtmyer-Meshkov instability in idealized ICF conditions. The Richtmyer-Meshkov instability seeds Rayleigh-taylor instabilities in ICF experiments and is one of the factors that contributes to reduced performance of ICF experiments. Its also found in collapsing cores of stars and supersonic combustion. We use the Stony Brook University code, FronTier, which is verified via a code comparison study against the AMR multiphysics code FLASH, and validated against vertical shock tube experiments done by the LANL Extreme Fluids Team. These simulations are designed as a step towards simulating more realistic ICF conditions and quantifying the detrimental effects of mixing on the yield.
Badjin, D A; Manukovskiy, K V; Blinnikov, S I
2015-01-01
We describe our experience of modelling of the radiatively cooling shocks and their thin shells with various numerical tools in different physical and calculational setups. We have found that under certain physical conditions, the circular shaped shells show a strong bending instability and successive fragmentation on Cartesian grids soon after their formation, while remain almost unperturbed when simulated on polar meshes. We explain these results as an interplay of numerical perturbations superimposed by grids not aligned to the flow lines, and a physical Rayleigh--Taylor like instability of the thin shell inner boundary being accelerated during re-estabilshing of pressure balance within and behind the shell after preceding sudden temperature loss. This phenomenon also sets new requirements on further radiatively cooling shocks simulations in order to be physically correct and free of numerical artefacts.
A hydrodynamic instability is used to create aesthetically appealing patterns in painting.
Sandra Zetina
Full Text Available Painters often acquire a deep empirical knowledge of the way in which paints and inks behave. Through experimentation and practice, they can control the way in which fluids move and deform to create textures and images. David Alfaro Siqueiros, a recognized Mexican muralist, invented an accidental painting technique to create new and unexpected textures. By pouring layers of paint of different colors on a horizontal surface, the paints infiltrate into each other creating patterns of aesthetic value. In this investigation, we reproduce the technique in a controlled manner. We found that for the correct color combination, the dual viscous layer becomes Rayleigh-Taylor unstable: the density mismatch of the two color paints drives the formation of a spotted pattern. Experiments and a linear instability analysis were conducted to understand the properties of the process. We also argue that this flow configuration can be used to study the linear properties of this instability.
Beane, Andy
2012-01-01
The essential fundamentals of 3D animation for aspiring 3D artists 3D is everywhere--video games, movie and television special effects, mobile devices, etc. Many aspiring artists and animators have grown up with 3D and computers, and naturally gravitate to this field as their area of interest. Bringing a blend of studio and classroom experience to offer you thorough coverage of the 3D animation industry, this must-have book shows you what it takes to create compelling and realistic 3D imagery. Serves as the first step to understanding the language of 3D and computer graphics (CG)Covers 3D anim
Lucas, Laurent; Loscos, Céline
2013-01-01
While 3D vision has existed for many years, the use of 3D cameras and video-based modeling by the film industry has induced an explosion of interest for 3D acquisition technology, 3D content and 3D displays. As such, 3D video has become one of the new technology trends of this century.The chapters in this book cover a large spectrum of areas connected to 3D video, which are presented both theoretically and technologically, while taking into account both physiological and perceptual aspects. Stepping away from traditional 3D vision, the authors, all currently involved in these areas, provide th
Kinetic Kelvin-Helmholtz instability at a finite sized object
Thomas, V. A.
1995-01-01
Two-dimensional hybrid simulations with particle ions and fluid electrons are used to calculate the kinetic evolution of the self-consistent flow around a two-dimensional obstacle with zero intrinsic magnetic field. Plasma outlfow from the obstacle is used to establish a boundary layer between the incoming solar wind and the outgoing plasma. Because the self-consistent flow solution, a velocity shear is naturally set up at this interface, and since the magnetic field for these simulations is transverse to this flow, the Kelvin-Helmholtz (K-H) instability can be excited at low-velocity shear. Simulations demonstrate the existence of the instability even near the subsolar location, which normally is thought to be stable to this instability. The apparent reason for this result is the overall time dependence at the boundary layer, which gives rise to a Rayleigh-Taylor like instability which provides seed perturbations for the K-H instability. These results are directly applicable to Venus, comets, artificial plasma releases, and laser target experiments. This result has potentially important ramifications for the interpretation of observational results as well as for an estimation of the cross-field transport. The results suggest that the K-H instability may play a role in dayside processes and the Venus ionopause, and may exist within the context of more general situations, for example, the Earth's magnetopause.
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.
Lessons Learned from Numerical Simulations of Interfacial Instabilities
Cook, Andrew
2015-11-01
Rayleigh-Taylor (RT), Richtmyer-Meshkov (RM) and Kelvin-Helmholtz (KH) instabilities serve as efficient mixing mechanisms in a wide variety of flows, from supernovae to jet engines. Over the past decade, we have used the Miranda code to temporally integrate the multi-component Navier-Stokes equations at spatial resolutions up to 29 billion grid points. The code employs 10th-order compact schemes for spatial derivatives, combined with 4th-order Runge-Kutta time advancement. Some of our major findings are as follows: The rate of growth of a mixing layer is equivalent to the net mass flux through the equi-molar plane. RT growth rates can be significantly reduced by adding shear. RT instability can produce shock waves. The growth rate of RM instability can be predicted from known interfacial perturbations. RM vortex projectiles can far outrun the mixing region. Thermal fluctuations in molecular dynamics simulations can seed instabilities along the braids in KH instability. And finally, enthalpy diffusion is essential in preserving the second law of thermodynamics. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Brdnik, Lovro
2015-01-01
Diplomsko delo analizira trenutno stanje 3D tiskalnikov na trgu. Prikazan je razvoj in principi delovanja 3D tiskalnikov. Predstavljeni so tipi 3D tiskalnikov, njihove prednosti in slabosti. Podrobneje je predstavljena zgradba in delovanje koračnih motorjev. Opravljene so meritve koračnih motorjev. Opisana je programska oprema za rokovanje s 3D tiskalniki in komponente, ki jih potrebujemo za izdelavo. Diploma se oklepa vprašanja, ali je izdelava 3D tiskalnika bolj ekonomična kot pa naložba v ...
Meulien Ohlmann, Odile
2013-02-01
Today the industry offers a chain of 3D products. Learning to "read" and to "create in 3D" becomes an issue of education of primary importance. 25 years professional experience in France, the United States and Germany, Odile Meulien set up a personal method of initiation to 3D creation that entails the spatial/temporal experience of the holographic visual. She will present some different tools and techniques used for this learning, their advantages and disadvantages, programs and issues of educational policies, constraints and expectations related to the development of new techniques for 3D imaging. Although the creation of display holograms is very much reduced compared to the creation of the 90ies, the holographic concept is spreading in all scientific, social, and artistic activities of our present time. She will also raise many questions: What means 3D? Is it communication? Is it perception? How the seeing and none seeing is interferes? What else has to be taken in consideration to communicate in 3D? How to handle the non visible relations of moving objects with subjects? Does this transform our model of exchange with others? What kind of interaction this has with our everyday life? Then come more practical questions: How to learn creating 3D visualization, to learn 3D grammar, 3D language, 3D thinking? What for? At what level? In which matter? for whom?
Kolar, Nataša
2016-01-01
Diplomsko delo predstavi razvoj tiskanja skozi čas. Podrobneje so opisani 3D tiskalniki, ki uporabljajo različne tehnologije 3D tiskanja. Predstavljene so različne tehnologije 3D tiskanja, njihova uporaba in narejeni prototipi oz. končni izdelki. Diplomsko delo opiše celoten postopek, od zamisli, priprave podatkov in tiskalnika do izdelave prototipa oz. končnega izdelka.
CHF Enhancement by Surface Patterning based on Hydrodynamic Instability Model
Seo, Han; Bang, In Cheol [UNIST, Ulsan (Korea, Republic of)
2015-05-15
If the power density of a device exceeds the CHF point, bubbles and vapor films will be covered on the whole heater surface. Because vapor films have much lower heat transfer capabilities compared to the liquid layer, the temperature of the heater surface will increase rapidly, and the device could be damaged due to the heater burnout. Therefore, the prediction and the enhancement of the CHF are essential to maximizing the efficient heat removal region. Numerous studies have been conducted to describe the CHF phenomenon, such as hydrodynamic instability theory, macrolayer dryout theory, hot/dry spot theory, and bubble interaction theory. The hydrodynamic instability model, proposed by Zuber, is the predominant CHF model that Helmholtz instability attributed to the CHF. Zuber assumed that the Rayleigh-Taylor (RT) instability wavelength is related to the Helmholtz wavelength. Lienhard and Dhir proposed a CHF model that Helmholtz instability wavelength is equal to the most dangerous RT wavelength. In addition, they showed the heater size effect using various heater surfaces. Lu et al. proposed a modified hydrodynamic theory that the Helmholtz instability was assumed to be the heater size and the area of the vapor column was used as a fitting factor. The modified hydrodynamic theories were based on the change of Helmholtz wavelength related to the RT instability wavelength. In the present study, the change of the RT instability wavelength, based on the heater surface modification, was conducted to show the CHF enhancement based on the heater surface patterning in a plate pool boiling. Sapphire glass was used as a base heater substrate, and the Pt film was used as a heating source. The patterning surface was based on the change of RT instability wavelength. In the present work the study of the CHF was conducted using bare Pt and patterned heating surfaces.
Tournay, Bruno; Rüdiger, Bjarne
2006-01-01
3d digital model af Arkitektskolens gård med virtuel udstilling af afgangsprojekter fra afgangen sommer 2006. 10 s.......3d digital model af Arkitektskolens gård med virtuel udstilling af afgangsprojekter fra afgangen sommer 2006. 10 s....
Fu, Wen
2012-01-01
We study global non-axisymmetric oscillation modes and instabilities in magnetosphere- disc systems, as expected in neutron star X-ray binaries and possibly also in accreting black hole systems. Our two-dimensional magnetosphere-disc model consists of a Keplerian disc in contact with an uniformly rotating magnetosphere with low plasma density. Two types of global overstable modes exist in such systems, the interface modes and the disc inertial-acoustic modes. We examine various physical effects and parameters that influence the properties of these oscillation modes, particularly their growth rates, including the magnetosphere field configuration, the velocity and density contrasts across the magnetosphere-disc interface, the rotation profile (with Newtonian or General Relativistic potential), the sound speed and magnetic field of the disc. The interface modes are driven unstable by Rayleigh-Taylor and Kelvin-Helmholtz in- stabilities, but can be stabilized by the toroidal field (through magnetic tension) and ...
Valenza, Enrico
2015-01-01
This book is aimed at the professionals that already have good 3D CGI experience with commercial packages and have now decided to try the open source Blender and want to experiment with something more complex than the average tutorials on the web. However, it's also aimed at the intermediate Blender users who simply want to go some steps further.It's taken for granted that you already know how to move inside the Blender interface, that you already have 3D modeling knowledge, and also that of basic 3D modeling and rendering concepts, for example, edge-loops, n-gons, or samples. In any case, it'
Hundebøl, Jesper
wave of new building information modelling tools demands further investigation, not least because of industry representatives' somewhat coarse parlance: Now the word is spreading -3D digital modelling is nothing less than a revolution, a shift of paradigm, a new alphabet... Research qeustions. Based...... on empirical probes (interviews, observations, written inscriptions) within the Danish construction industry this paper explores the organizational and managerial dynamics of 3D Digital Modelling. The paper intends to - Illustrate how the network of (non-)human actors engaged in the promotion (and arrest) of 3......D Modelling (in Denmark) stabilizes - Examine how 3D Modelling manifests itself in the early design phases of a construction project with a view to discuss the effects hereof for i.a. the management of the building process. Structure. The paper introduces a few, basic methodological concepts...
Lively, Michael
2010-01-01
Professional Papervision3D describes how Papervision3D works and how real world applications are built, with a clear look at essential topics such as building websites and games, creating virtual tours, and Adobe's Flash 10. Readers learn important techniques through hands-on applications, and build on those skills as the book progresses. The companion website contains all code examples, video step-by-step explanations, and a collada repository.
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.
Numerical simulation of the hydrodynamic instability experiments and flow mixing
BAI JingSong; WANG Tao; LI Ping; ZOU LiYong; LIU CangLi
2009-01-01
Based on the numerical methods of volume of fluid (VOF) and piecewise parabolic method (PPM) and parallel circumstance of Message Passing Interface (MPI), a parallel multi-viscosity-fluid hydrodynamic code MVPPM (Multi-Viscosity-Fluid Piecewise Parabolic Method) is developed and performed to study the hydrodynamic instability and flow mixing. Firstly, the MVPPM code is verified and validated by simulating three instability cases: The first one is a Riemann problem of viscous flow on the shock tube;the second one is the hydrodynamic instability and mixing of gaseous flows under re-shocks; the third one is a half height experiment of interfacial instability, which is conducted on the AWE's shock tube. By comparing the numerical results with experimental data, good agreement is achieved. Then the MVPPM code is applied to simulate the two cases of the interfacial instabilities of jelly models accelerated by explosion products of a gaseous explosive mixture (GEM), which are adopted in our experiments. The first is implosive dynamic interfacial instability of cylindrical symmetry and mixing. The evolving process of inner and outer interfaces, and the late distribution of mixing mass caused by Rayleigh-Taylor (RT) instability in the center of different radius are given. The second is jelly layer experiment which is initialized with one periodic perturbation with different amplitude and wave length. It reveals the complex processes of evolution of interface, and presents the displacement of front face of jelly layer, bubble head and top of spike relative to initial equilibrium position vs. time. The numerical results are in excellent agreement with that experimental images, and show that the amplitude of initial perturbations affects the evolvement of fluid mixing zone (FMZ) growth rate extremely, especially at late times.
Numerical simulation of the hydrodynamic instability experiments and flow mixing
无
2009-01-01
Based on the numerical methods of volume of fluid (VOF) and piecewise parabolic method (PPM) and parallel circumstance of Message Passing Interface (MPI),a parallel multi-viscosity-fluid hydrodynamic code MVPPM (Multi-Viscosity-Fluid Piecewise Parabolic Method) is developed and performed to study the hydrodynamic instability and flow mixing. Firstly,the MVPPM code is verified and validated by simulating three instability cases:The first one is a Riemann problem of viscous flow on the shock tube; the second one is the hydrodynamic instability and mixing of gaseous flows under re-shocks; the third one is a half height experiment of interfacial instability,which is conducted on the AWE’s shock tube. By comparing the numerical results with experimental data,good agreement is achieved. Then the MVPPM code is applied to simulate the two cases of the interfacial instabilities of jelly models acceler-ated by explosion products of a gaseous explosive mixture (GEM),which are adopted in our experi-ments. The first is implosive dynamic interfacial instability of cylindrical symmetry and mixing. The evolving process of inner and outer interfaces,and the late distribution of mixing mass caused by Rayleigh-Taylor (RT) instability in the center of different radius are given. The second is jelly layer ex-periment which is initialized with one periodic perturbation with different amplitude and wave length. It reveals the complex processes of evolution of interface,and presents the displacement of front face of jelly layer,bubble head and top of spike relative to initial equilibrium position vs. time. The numerical results are in excellent agreement with that experimental images,and show that the amplitude of initial perturbations affects the evolvement of fluid mixing zone (FMZ) growth rate extremely,especially at late times.
Elmegreen, Bruce G.
1991-09-01
The growth of shearing wavelets in thick galactic gas disks is studied, including the magnetic Rayleigh-Taylor instability perpendicular to the plane, various degrees of thermal instability, and the gravitational instability. Growth rates are calculated numerically for a wide range of parameter values, giving an effective dispersion relation and mass distribution function, and an approximate dispersion relation is derived analytically for the epoch of peak growth. An extensive coverage of parameter space illustrates the relative insensitivity of the gaseous shear instability to the axisymmetric stability parameter Q. The fragmentation of shearing wavelets by self-gravitational collapse parallel to the wave crest is also considered. Such fragmentation is sensitive to Q, requiring Q equal to or less than 1-2 for the growth of parallel perturbations to overcome shear inside the wavelet. Fragmentation instabilities may provide the link between shear instabilities and the formation of individual clouds. They are much more sensitive to Q than shear instabilities, and may regulate star formation so that Q approximately equals 1.
Linear simulations of the cylindrical Richtmyer-Meshkov instability in magnetohydrodynamics
Bakhsh, Abeer
2016-03-09
Numerical simulations and analysis indicate that the Richtmyer-Meshkov instability(RMI) is suppressed in ideal magnetohydrodynamics(MHD) in Cartesian slab geometry. Motivated by the presence of hydrodynamic instabilities in inertial confinement fusion and suppression by means of a magnetic field, we investigate the RMI via linear MHD simulations in cylindrical geometry. The physical setup is that of a Chisnell-type converging shock interacting with a density interface with either axial or azimuthal (2D) perturbations. The linear stability is examined in the context of an initial value problem (with a time-varying base state) wherein the linearized ideal MHD equations are solved with an upwind numerical method. Linear simulations in the absence of a magnetic field indicate that RMI growth rate during the early time period is similar to that observed in Cartesian geometry. However, this RMI phase is short-lived and followed by a Rayleigh-Taylor instability phase with an accompanied exponential increase in the perturbation amplitude. We examine several strengths of the magnetic field (characterized by β=2p/B^2_r) and observe a significant suppression of the instability for β ≤ 4. The suppression of the instability is attributed to the transport of vorticity away from the interface by Alfvén fronts.
Casner, A.; Masse, L.; Delorme, B.; Martinez, D.; Huser, G.; Galmiche, D.; Liberatore, S.; Igumenshchev, I.; Olazabal-Loumé, M.; Nicolaï, Ph.; Breil, J.; Michel, D. T.; Froula, D.; Seka, W.; Riazuelo, G.; Fujioka, S.; Sunahara, A.; Grech, M.; Chicanne, C.; Theobald, M.; Borisenko, N.; Orekhov, A.; Tikhonchuk, V. T.; Remington, B.; Goncharov, V. N.; Smalyuk, V. A.
2014-12-01
Understanding and mitigating hydrodynamic instabilities and the fuel mix are the key elements for achieving ignition in Inertial Confinement Fusion. Cryogenic indirect-drive implosions on the National Ignition Facility have evidenced that the ablative Rayleigh-Taylor Instability (RTI) is a driver of the hot spot mix. This motivates the switch to a more flexible higher adiabat implosion design [O. A. Hurricane et al., Phys. Plasmas 21, 056313 (2014)]. The shell instability is also the main candidate for performance degradation in low-adiabat direct drive cryogenic implosions [Goncharov et al., Phys. Plasmas 21, 056315 (2014)]. This paper reviews recent results acquired in planar experiments performed on the OMEGA laser facility and devoted to the modeling and mitigation of hydrodynamic instabilities at the ablation front. In application to the indirect-drive scheme, we describe results obtained with a specific ablator composition such as the laminated ablator or a graded-dopant emulator. In application to the direct drive scheme, we discuss experiments devoted to the study of laser imprinted perturbations with special phase plates. The simulations of the Richtmyer-Meshkov phase reversal during the shock transit phase are challenging, and of crucial interest because this phase sets the seed of the RTI growth. Recent works were dedicated to increasing the accuracy of measurements of the phase inversion. We conclude by presenting a novel imprint mitigation mechanism based on the use of underdense foams. The foams induce laser smoothing by parametric instabilities thus reducing the laser imprint on the CH foil.
Casner, A., E-mail: alexis.casner@cea.fr; Masse, L.; Huser, G.; Galmiche, D.; Liberatore, S.; Riazuelo, G. [CEA, DAM, DIF, F-91297 Arpajon (France); Delorme, B. [CEA, DAM, DIF, F-91297 Arpajon (France); CELIA, University of Bordeaux-CNRS-CEA, F-33400 Talence (France); Martinez, D.; Remington, B.; Smalyuk, V. A. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Igumenshchev, I.; Michel, D. T.; Froula, D.; Seka, W.; Goncharov, V. N. [Laboratory of Laser Energetics, Rochester, New York 14623-1299 (United States); Olazabal-Loumé, M.; Nicolaï, Ph.; Breil, J.; Tikhonchuk, V. T. [CELIA, University of Bordeaux-CNRS-CEA, F-33400 Talence (France); Fujioka, S. [Institute of Laser Engineering, Osaka University, Suita, Osaka 565 (Japan); and others
2014-12-15
Understanding and mitigating hydrodynamic instabilities and the fuel mix are the key elements for achieving ignition in Inertial Confinement Fusion. Cryogenic indirect-drive implosions on the National Ignition Facility have evidenced that the ablative Rayleigh-Taylor Instability (RTI) is a driver of the hot spot mix. This motivates the switch to a more flexible higher adiabat implosion design [O. A. Hurricane et al., Phys. Plasmas 21, 056313 (2014)]. The shell instability is also the main candidate for performance degradation in low-adiabat direct drive cryogenic implosions [Goncharov et al., Phys. Plasmas 21, 056315 (2014)]. This paper reviews recent results acquired in planar experiments performed on the OMEGA laser facility and devoted to the modeling and mitigation of hydrodynamic instabilities at the ablation front. In application to the indirect-drive scheme, we describe results obtained with a specific ablator composition such as the laminated ablator or a graded-dopant emulator. In application to the direct drive scheme, we discuss experiments devoted to the study of laser imprinted perturbations with special phase plates. The simulations of the Richtmyer-Meshkov phase reversal during the shock transit phase are challenging, and of crucial interest because this phase sets the seed of the RTI growth. Recent works were dedicated to increasing the accuracy of measurements of the phase inversion. We conclude by presenting a novel imprint mitigation mechanism based on the use of underdense foams. The foams induce laser smoothing by parametric instabilities thus reducing the laser imprint on the CH foil.
Oldham, Mark
2015-01-01
Radiochromic materials exhibit a colour change when exposed to ionising radiation. Radiochromic film has been used for clinical dosimetry for many years and increasingly so recently, as films of higher sensitivities have become available. The two principle advantages of radiochromic dosimetry include greater tissue equivalence (radiologically) and the lack of requirement for development of the colour change. In a radiochromic material, the colour change arises direct from ionising interactions affecting dye molecules, without requiring any latent chemical, optical or thermal development, with important implications for increased accuracy and convenience. It is only relatively recently however, that 3D radiochromic dosimetry has become possible. In this article we review recent developments and the current state-of-the-art of 3D radiochromic dosimetry, and the potential for a more comprehensive solution for the verification of complex radiation therapy treatments, and 3D dose measurement in general.
3D Spectroscopic Instrumentation
Bershady, Matthew A
2009-01-01
In this Chapter we review the challenges of, and opportunities for, 3D spectroscopy, and how these have lead to new and different approaches to sampling astronomical information. We describe and categorize existing instruments on 4m and 10m telescopes. Our primary focus is on grating-dispersed spectrographs. We discuss how to optimize dispersive elements, such as VPH gratings, to achieve adequate spectral resolution, high throughput, and efficient data packing to maximize spatial sampling for 3D spectroscopy. We review and compare the various coupling methods that make these spectrographs ``3D,'' including fibers, lenslets, slicers, and filtered multi-slits. We also describe Fabry-Perot and spatial-heterodyne interferometers, pointing out their advantages as field-widened systems relative to conventional, grating-dispersed spectrographs. We explore the parameter space all these instruments sample, highlighting regimes open for exploitation. Present instruments provide a foil for future development. We give an...
Halskov, Kim; Johansen, Stine Liv; Bach Mikkelsen, Michelle
2014-01-01
Three-dimensional projection installations are particular kinds of augmented spaces in which a digital 3-D model is projected onto a physical three-dimensional object, thereby fusing the digital content and the physical object. Based on interaction design research and media studies, this article...... contributes to the understanding of the distinctive characteristics of such a new medium, and identifies three strategies for designing 3-D projection installations: establishing space; interplay between the digital and the physical; and transformation of materiality. The principal empirical case, From...... Fingerplan to Loop City, is a 3-D projection installation presenting the history and future of city planning for the Copenhagen area in Denmark. The installation was presented as part of the 12th Architecture Biennale in Venice in 2010....
Villaume, René Domine; Ørstrup, Finn Rude
2002-01-01
Projektet undersøger potentialet for interaktiv 3D design via Internettet. Arkitekt Jørn Utzons projekt til Espansiva blev udviklet som et byggesystem med det mål, at kunne skabe mangfoldige planmuligheder og mangfoldige facade- og rumudformninger. Systemets bygningskomponenter er digitaliseret som...... 3D elementer og gjort tilgængelige. Via Internettet er det nu muligt at sammenstille og afprøve en uendelig række bygningstyper som systemet blev tænkt og udviklet til....
Nonlinear Saturation Amplitude in Classical Planar Richtmyer-Meshkov Instability
Liu, Wan-Hai; Wang, Xiang; Jiang, Hong-Bin; Ma, Wen-Fang
2016-04-01
The classical planar Richtmyer-Meshkov instability (RMI) at a fluid interface supported by a constant pressure is investigated by a formal perturbation expansion up to the third order, and then according to definition of nonlinear saturation amplitude (NSA) in Rayleigh-Taylor instability (RTI), the NSA in planar RMI is obtained explicitly. It is found that the NSA in planar RMI is affected by the initial perturbation wavelength and the initial amplitude of the interface, while the effect of the initial amplitude of the interface on the NSA is less than that of the initial perturbation wavelength. Without marginal influence of the initial amplitude, the NSA increases linearly with wavelength. The NSA normalized by the wavelength in planar RMI is about 0.11, larger than that corresponding to RTI. Supported by the National Natural Science Foundation of China under Grant Nos. 11472278 and 11372330, the Scientific Research Foundation of Education Department of Sichuan Province under Grant No. 15ZA0296, the Scientific Research Foundation of Mianyang Normal University under Grant Nos. QD2014A009 and 2014A02, and the National High-Tech ICF Committee
Hejlesen, Aske K.; Ovesen, Nis
2012-01-01
This paper presents an experimental approach to teaching 3D modelling techniques in an Industrial Design programme. The approach includes the use of tangible free form models as tools for improving the overall learning. The paper is based on lecturer and student experiences obtained through...
Stenholt, Rasmus; Madsen, Claus B.
2011-01-01
Enabling users to shape 3-D boxes in immersive virtual environments is a non-trivial problem. In this paper, a new family of techniques for creating rectangular boxes of arbitrary position, orientation, and size is presented and evaluated. These new techniques are based solely on position data...
Jordi, Moréton; F, Escribano; J. L., Farias
This document is a general report on the implementation of gamification in 3D Wire 2015 event. As the second gamification experience in this event, we have delved deeply in the previous objectives (attracting public areas less frequented exhibition in previous years and enhance networking) and ha......, improves socialization and networking, improves media impact, improves fun factor and improves encouragement of the production team....
Carson, Jeffrey J. L.; Roumeliotis, Michael; Chaudhary, Govind; Stodilka, Robert Z.; Anastasio, Mark A.
2010-06-01
Our group has concentrated on development of a 3D photoacoustic imaging system for biomedical imaging research. The technology employs a sparse parallel detection scheme and specialized reconstruction software to obtain 3D optical images using a single laser pulse. With the technology we have been able to capture 3D movies of translating point targets and rotating line targets. The current limitation of our 3D photoacoustic imaging approach is its inability ability to reconstruct complex objects in the field of view. This is primarily due to the relatively small number of projections used to reconstruct objects. However, in many photoacoustic imaging situations, only a few objects may be present in the field of view and these objects may have very high contrast compared to background. That is, the objects have sparse properties. Therefore, our work had two objectives: (i) to utilize mathematical tools to evaluate 3D photoacoustic imaging performance, and (ii) to test image reconstruction algorithms that prefer sparseness in the reconstructed images. Our approach was to utilize singular value decomposition techniques to study the imaging operator of the system and evaluate the complexity of objects that could potentially be reconstructed. We also compared the performance of two image reconstruction algorithms (algebraic reconstruction and l1-norm techniques) at reconstructing objects of increasing sparseness. We observed that for a 15-element detection scheme, the number of measureable singular vectors representative of the imaging operator was consistent with the demonstrated ability to reconstruct point and line targets in the field of view. We also observed that the l1-norm reconstruction technique, which is known to prefer sparseness in reconstructed images, was superior to the algebraic reconstruction technique. Based on these findings, we concluded (i) that singular value decomposition of the imaging operator provides valuable insight into the capabilities of
Garcia-Fenoll, M.; Barrachina, T.; Miro, R.; Verdu, G.
2014-07-01
In this work, part of our works in the frame of the OECD/NEA Oskarshamn-2 (O{sub 2}) BWR Stability Benchmark for Coupled Code Calculations and Uncertainty Analysis in Modelling are shown. The objective is to simulate the instability event registered in February 1999 at the Swedish NPP Oskarshamn-2 with the coupled code RELAP5/PARCSv2.7. (Author)
Bhardwaj, Lakshya
2016-01-01
This paper generalizes two facts about oriented 3d TFTs to the unoriented case. On one hand, it is known that oriented 3d TFTs having a topological boundary condition admit a state-sum construction known as the Turaev-Viro construction. This is related to the string-net construction of fermionic phases of matter. We show how Turaev-Viro construction can be generalized to unoriented 3d TFTs. On the other hand, it is known that the "fermionic" versions of oriented TFTs, known as Spin-TFTs, can be constructed in terms of "shadow" TFTs which are ordinary oriented TFTs with an anomalous Z_2 1-form symmetry. We generalize this correspondence to Pin+ TFTs by showing that they can be constructed in terms of ordinary unoriented TFTs with anomalous Z_2 1-form symmetry having a mixed anomaly with time-reversal symmetry. The corresponding Pin+ TFT does not have any anomaly for time-reversal symmetry however and hence it can be unambiguously defined on a non-orientable manifold. In case a Pin+ TFT admits a topological bou...
Hydrodynamic instability measurements in DT-layered ICF capsules using the layered-HGR platform
Weber, C.; Döppner, T.; Casey, D.; Bunn, T.; Carlson, L.; Dylla-Spears, R.; Kozioziemski, B.; MacPhee, A. G.; Sater, J.; Nikroo, A.; Robey, H.; Smalyuk, V.
2016-05-01
The first measurements of hydrodynamic instability growth at the fuel-ablator interface in an ICF implosion are reported. Previous instability measurements on the National Ignition Facility have used plastic capsules to measure ablation front Rayleigh-Taylor growth with the Hydro.-Growth Radiography (HGR) platform. These capsules substituted an additional thickness of plastic ablator material in place of the cryogenic layer of Deuterium- Tritium (DT) fuel. The present experiments are the first to include a DT ice layer, which enables measurements of the instability growth occurring at the fuel-ablator interface. Instability growth at the fuel-ablator interface is seeded differently in two independent NIF experiments. In the first case, a perturbation on the outside of the capsule feeds through and grows on the interface. Comparisons to an implosion without a fuel layer produce a measure of the fuel's modulation. In the second case, a modulation was directly machined on the inner ablator before the fuel layer was added. The measurement of growth in these two scenarios are compared to 2D rad-hydro modeling.
Interfacial Instabilities Driven by Self-Gravity in the ISM: Onset and Evolution
Hueckstaedt, R. M.; Hunter, J. H., Jr.
2000-12-01
As the sites of all present day star formation within the Milky Way, cold molecular clouds are a vital link in the evolution of tenuous interstellar gas into stars. Any comprehensive theory of star formation must include a study of the hydrodynamic processes that effect molecular cloud morphology. In the ISM, hydrodynamic instabilities and turbulence play large roles in shaping clouds and creating regions capable of gravitational collapse. One of the key forces in the interstellar environment is self-gravity. Regardless of the mechanism initially responsible for creating density enhancements, self-gravity must ultimately drive the final collapse. A recent study has shown that self-gravity also gives rise to an interfacial instability that persists in the static limit when a density discontinuity exists (Hunter, Whitaker & Lovelace 1997). This instability also persists in the absence of a constant gravitational acceleration, unlike the familiar Rayleigh-Taylor instability. Analytic studies in Cartesian geometry predict that for perturbations proportional to exp(-iωt), the instability has an incompressible growth rate ω2= -2πG(ρ 1-ρ 2)2/(ρ1+ρ2). The growth rate is independent of the perturbation wavelength. Studies have also included cases in cylindrical geometry in which a static density interface has proven stable to kink modes but unstable to sausage modes. In the case of sausage modes, (perturbations in the radial direction), there exists a critical wavelength below which the instability does not appear. In this paper, we present two-dimensional numerical models designed to examine this self-gravity driven instability. A hydrodynamic code with self-gravity is used to test the analytic predictions in Cartesian and cylindrical geometries and to follow the instability into the nonlinear regime. We consider how the growth of hydrodynamic instabilities, including self-gravity driven instabilities, can have a role in shaping the ISM. We discuss implications for
Kelvin-Helmholtz Instability in the Solar Atmosphere, Solar Wind and Geomagnetosphere
Mishin, V. V.; Tomozov, V. M.
2016-11-01
Modern views on the nature of the Kelvin-Helmholtz (KH) instability and its manifestations in the solar corona, in the interplanetary medium, and at the geomagnetospheric boundary are under consideration. We briefly describe the main theoretical results of the KH instability obtained in the linear approximation. Analysis of observational data, confirming the occurrence of the KH instability in magnetic formations of the solar coronal plasma and on the daytime magnetopause, was mainly performed in the approximation of incompressibility. We show that the Rayleigh-Taylor instability can significantly enhance the KH instability in the above regions due to interface accelerations or its curvature. Special attention is focused on the compressibility effect on the supersonic shear flow instability in the solar wind (SW) and at the geomagnetic tail boundary where this instability is usually considered to be ineffective. We have shown that the phase velocity of oblique perturbations is substantially less than the flow velocity, and values of the growth rate and frequency range are considerably higher than when only taking velocity-aligned disturbances into account. We emphasize that the magnetic field and plasma density inhomogeneity which weaken the KH instability of subsonic shear flows, in the case of a supersonic velocity difference weaken the stabilizing effect of the medium compressibility, and can significantly increase the instability. Effective generation of oblique disturbances by the supersonic KH instability explains the observations of magnetosonic waves and the formation of diffuse shear flows in the SW and on the distant magnetotail boundary, as well as the SW-magnetosphere energy and impulse transfer.
Hydrodynamic Instabilities in High-Energy-Density Settings
Smalyuk, Vladimir
2016-10-01
Our understanding of hydrodynamic instabilities, such as the Rayleigh-Taylor (RT), Richtmyer-Meshkov (RM), and Kelvin-Helmholtz (KH) instabilities, in high-energy-density (HED) settings over past two decades has progressed enormously. The range of conditions where hydrodynamic instabilities are experimentally observed now includes direct and indirect drive inertial confinement fusion (ICF) where surprises continue to emerge, linear and nonlinear regimes, classical interfaces vs. stabilized ablation fronts, tenuous ideal plasmas vs. high density Fermi degenerate plasmas, bulk fluid interpenetration vs. mixing down to the atomic level, in the presence of magnetic fields and/or intense radiation, and in solid state plastic flow at high pressures and strain rates. Regimes in ICF can involve extreme conditions of matter with temperatures up to kilovolts, densities of a thousand times solid densities, and time scales of nanoseconds. On the other hand, scaled conditions can be generated that map to exploding stars (supernovae) with length and time scales of millions of kilometers and hours to days or even years of instability evolution, planetary formation dynamics involving solid-state plastic flow which severely modifies the RT growth and continues to challenge reliable theoretical descriptions. This review will look broadly at progress in probing and understanding hydrodynamic instabilities in these very diverse HED settings, and then will examine a few cases in more depth to illustrate the detailed science involved. Experimental results on large-scale HED facilities such as the Omega, Nike, Gekko, and Shenguang lasers will be reviewed and the latest developments at the National Ignition Facility (NIF) and Z machine will be covered. Finally, current overarching questions and challenges will be summarized to motivate research directions for future. This work was performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344.
Fung, Y. C.
1995-05-01
This conference on physiology and function covers a wide range of subjects, including the vasculature and blood flow, the flow of gas, water, and blood in the lung, the neurological structure and function, the modeling, and the motion and mechanics of organs. Many technologies are discussed. I believe that the list would include a robotic photographer, to hold the optical equipment in a precisely controlled way to obtain the images for the user. Why are 3D images needed? They are to achieve certain objectives through measurements of some objects. For example, in order to improve performance in sports or beauty of a person, we measure the form, dimensions, appearance, and movements.
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
Ms. Swapnali R. Ghadge
2013-08-01
Full Text Available In today’s ever-shifting media landscape, it can be a complex task to find effective ways to reach your desired audience. As traditional media such as television continue to lose audience share, one venue in particular stands out for its ability to attract highly motivated audiences and for its tremendous growth potential the 3D Internet. The concept of '3D Internet' has recently come into the spotlight in the R&D arena, catching the attention of many people, and leading to a lot of discussions. Basically, one can look into this matter from a few different perspectives: visualization and representation of information, and creation and transportation of information, among others. All of them still constitute research challenges, as no products or services are yet available or foreseen for the near future. Nevertheless, one can try to envisage the directions that can be taken towards achieving this goal. People who take part in virtual worlds stay online longer with a heightened level of interest. To take advantage of that interest, diverse businesses and organizations have claimed an early stake in this fast-growing market. They include technology leaders such as IBM, Microsoft, and Cisco, companies such as BMW, Toyota, Circuit City, Coca Cola, and Calvin Klein, and scores of universities, including Harvard, Stanford and Penn State.
Spike Penetration in Blast-Wave-Driven Instabilities
Drake, R. Paul
2010-05-01
Recent experiments by C. Kuranz and collaborators, motivated by structure in supernovae, have studied systems in which planar blast waves encounter interfaces where the density decreases. During the Rayleigh-Taylor (RT) phase of such experiments, they observed greater penetration of the RT spikes than tends to be seen in simulations. Here we seek to employ semi-analytic theory to understand the general nature and regimes of spike penetration for blast-wave-driven instabilities. This problem is not trivial as one must account for the initial vorticity deposition at the interface, for its time-dependent deceleration, for the expansion of the shocked material in time and space, and for the drag on the broadened tips of the spikes. We offer here an improved evaluation of the material expansion in comparison to past work. The goal is to use such models to increase our ability to interpret the behavior of simulations of such systems, in both the laboratory and astrophysics. Supported by the US DOE NNSA under the Predictive Sci. Academic Alliance Program by grant DE-FC52-08NA28616, the Stewardship Sci. Academic Alliances program by grant DE-FG52-04NA00064, and the Nat. Laser User Facility by grant DE-FG03-00SF22021.
Hausman, Kalani Kirk
2014-01-01
Get started printing out 3D objects quickly and inexpensively! 3D printing is no longer just a figment of your imagination. This remarkable technology is coming to the masses with the growing availability of 3D printers. 3D printers create 3-dimensional layered models and they allow users to create prototypes that use multiple materials and colors. This friendly-but-straightforward guide examines each type of 3D printing technology available today and gives artists, entrepreneurs, engineers, and hobbyists insight into the amazing things 3D printing has to offer. You'll discover methods for
Kühmstedt, Peter; Bräuer-Burchardt, Christian; Munkelt, Christoph; Heinze, Matthias; Palme, Martin; Schmidt, Ingo; Hintersehr, Josef; Notni, Gunther
2007-09-01
Here a new set-up of a 3D-scanning system for CAD/CAM in dental industry is proposed. The system is designed for direct scanning of the dental preparations within the mouth. The measuring process is based on phase correlation technique in combination with fast fringe projection in a stereo arrangement. The novelty in the approach is characterized by the following features: A phase correlation between the phase values of the images of two cameras is used for the co-ordinate calculation. This works contrary to the usage of only phase values (phasogrammetry) or classical triangulation (phase values and camera image co-ordinate values) for the determination of the co-ordinates. The main advantage of the method is that the absolute value of the phase at each point does not directly determine the coordinate. Thus errors in the determination of the co-ordinates are prevented. Furthermore, using the epipolar geometry of the stereo-like arrangement the phase unwrapping problem of fringe analysis can be solved. The endoscope like measurement system contains one projection and two camera channels for illumination and observation of the object, respectively. The new system has a measurement field of nearly 25mm × 15mm. The user can measure two or three teeth at one time. So the system can by used for scanning of single tooth up to bridges preparations. In the paper the first realization of the intraoral scanner is described.
1997-01-01
This area of terrain near the Sagan Memorial Station was taken on Sol 3 by the Imager for Mars Pathfinder (IMP). 3D glasses are necessary to identify surface detail.The IMP is a stereo imaging system with color capability provided by 24 selectable filters -- twelve filters per 'eye.' It stands 1.8 meters above the Martian surface, and has a resolution of two millimeters at a range of two meters.Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is an operating division of the California Institute of Technology (Caltech). The Imager for Mars Pathfinder (IMP) was developed by the University of Arizona Lunar and Planetary Laboratory under contract to JPL. Peter Smith is the Principal Investigator.Click below to see the left and right views individually. [figure removed for brevity, see original site] Left [figure removed for brevity, see original site] Right
Aboufadel, Edward F.
2014-01-01
The purpose of this short paper is to describe a project to manufacture a regular octohedron on a 3D printer. We assume that the reader is familiar with the basics of 3D printing. In the project, we use fundamental ideas to calculate the vertices and faces of an octohedron. Then, we utilize the OPENSCAD program to create a virtual 3D model and an STereoLithography (.stl) file that can be used by a 3D printer.
Salient Local 3D Features for 3D Shape Retrieval
Godil, Afzal
2011-01-01
In this paper we describe a new formulation for the 3D salient local features based on the voxel grid inspired by the Scale Invariant Feature Transform (SIFT). We use it to identify the salient keypoints (invariant points) on a 3D voxelized model and calculate invariant 3D local feature descriptors at these keypoints. We then use the bag of words approach on the 3D local features to represent the 3D models for shape retrieval. The advantages of the method are that it can be applied to rigid as well as to articulated and deformable 3D models. Finally, this approach is applied for 3D Shape Retrieval on the McGill articulated shape benchmark and then the retrieval results are presented and compared to other methods.
Movahed, Pooya
High-speed flows are prone to hydrodynamic interfacial instabilities that evolve to turbulence, thereby intensely mixing different fluids and dissipating energy. The lack of knowledge of these phenomena has impeded progress in a variety of disciplines. In science, a full understanding of mixing between heavy and light elements after the collapse of a supernova and between adjacent layers of different density in geophysical (atmospheric and oceanic) flows remains lacking. In engineering, the inability to achieve ignition in inertial fusion and efficient combustion constitute further examples of this lack of basic understanding of turbulent mixing. In this work, my goal is to develop accurate and efficient numerical schemes and employ them to study compressible turbulence and mixing generated by interactions between shocked (Richtmyer-Meshkov) and accelerated (Rayleigh-Taylor) interfaces, which play important roles in high-energy-density physics environments. To accomplish my goal, a hybrid high-order central/discontinuity-capturing finite difference scheme is first presented. The underlying principle is that, to accurately and efficiently represent both broadband motions and discontinuities, non-dissipative methods are used where the solution is smooth, while the more expensive and dissipative capturing schemes are applied near discontinuous regions. Thus, an accurate numerical sensor is developed to discriminate between smooth regions, shocks and material discontinuities, which all require a different treatment. The interface capturing approach is extended to central differences, such that smooth distributions of varying specific heats ratio can be simulated without generating spurious pressure oscillations. I verified and validated this approach against a stringent suite of problems including shocks, interfaces, turbulence and two-dimensional single-mode Richtmyer-Meshkov instability simulations. The three-dimensional code is shown to scale well up to 4000 cores
R-T instability model of magnetic fluid and its numerical simulations
郑秋云; 李明军; 舒适
2008-01-01
The Rayleigh-Taylor(R-T) instability of ferrofluid has been the subject of recent research,because of its implications on the stability of stellar.By neglecting the viscosity and rotation of magnetic fluid,and assuming that the magnetic particles are irrotational and temperature insensitive,we obtain a simplified R-T instability model of magnetic fluid.For the interface tracing,we use five-order weighted essentially non-oscillatory(WENO) scheme to spatial direction and three-order TVD R-K method to time direction on the uniform mesh,respectively.If the direction of the external magnetic field is the same as that of gravity,the velocities of the interface will be increased.But if the direction of the external magnetic field is in opposition to the direction of gravity,the velocities of the interface will be decreased.When the direction of the external magnetic field is perpendicular to the direction of gravity,the symmetry of the interface will be destroyed.Because of the action which is produced by perpendicular external magnetic field,there are other bubbles at the boudaries which parallel the direction of gravity.When we increase the magnetic susceptibility of the magnetic fluids,the effects of external magnetic fields will be more distinct for the interface tracing.
Angulo, A. A.; Kuranz, C. C.; Drake, R. P.; Huntington, C. M.; Park, H.-S.; Remington, B. A.; Kalantar, D.; MacLaren, S.; Raman, K.; Miles, A.; Trantham, Matthew; Kline, J. L.; Flippo, K.; Doss, F. W.; Shvarts, D.
2016-10-01
This poster will describe simulations based on results from ongoing laboratory astrophysics experiments at the National Ignition Facility (NIF) relevant to the effects of radiative shock on hydrodynamically unstable surfaces. The experiments performed on NIF uniquely provide the necessary conditions required to emulate radiative shock that occurs in astrophysical systems. The core-collapse explosions of red supergiant stars is such an example wherein the interaction between the supernova ejecta and the circumstellar medium creates a region susceptible to Rayleigh-Taylor (R-T) instabilities. Radiative and nonradiative experiments were performed to show that R-T growth should be reduced by the effects of the radiative shocks that occur during this core-collapse. Simulations were performed using the radiation hydrodynamics code Hyades using the experimental conditions to find the mean interface acceleration of the instability and then further analyzed in the buoyancy drag model to observe how the material expansion contributes to the mix-layer growth. This work is funded by the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas under Grant Number DE-FG52-09NA29548.
Mediavilla, Evencio; Arribas, Santiago; Roth, Martin; Cepa-Nogué, Jordi; Sánchez, Francisco
2011-09-01
Preface; Acknowledgements; 1. Introductory review and technical approaches Martin M. Roth; 2. Observational procedures and data reduction James E. H. Turner; 3. 3D Spectroscopy instrumentation M. A. Bershady; 4. Analysis of 3D data Pierre Ferruit; 5. Science motivation for IFS and galactic studies F. Eisenhauer; 6. Extragalactic studies and future IFS science Luis Colina; 7. Tutorials: how to handle 3D spectroscopy data Sebastian F. Sánchez, Begona García-Lorenzo and Arlette Pécontal-Rousset.
Spherical 3D isotropic wavelets
Lanusse, F.; Rassat, A.; Starck, J.-L.
2012-04-01
Context. Future cosmological surveys will provide 3D large scale structure maps with large sky coverage, for which a 3D spherical Fourier-Bessel (SFB) analysis in spherical coordinates is natural. Wavelets are particularly well-suited to the analysis and denoising of cosmological data, but a spherical 3D isotropic wavelet transform does not currently exist to analyse spherical 3D data. Aims: The aim of this paper is to present a new formalism for a spherical 3D isotropic wavelet, i.e. one based on the SFB decomposition of a 3D field and accompany the formalism with a public code to perform wavelet transforms. Methods: We describe a new 3D isotropic spherical wavelet decomposition based on the undecimated wavelet transform (UWT) described in Starck et al. (2006). We also present a new fast discrete spherical Fourier-Bessel transform (DSFBT) based on both a discrete Bessel transform and the HEALPIX angular pixelisation scheme. We test the 3D wavelet transform and as a toy-application, apply a denoising algorithm in wavelet space to the Virgo large box cosmological simulations and find we can successfully remove noise without much loss to the large scale structure. Results: We have described a new spherical 3D isotropic wavelet transform, ideally suited to analyse and denoise future 3D spherical cosmological surveys, which uses a novel DSFBT. We illustrate its potential use for denoising using a toy model. All the algorithms presented in this paper are available for download as a public code called MRS3D at http://jstarck.free.fr/mrs3d.html
3D IBFV : Hardware-Accelerated 3D Flow Visualization
Telea, Alexandru; Wijk, Jarke J. van
2003-01-01
We present a hardware-accelerated method for visualizing 3D flow fields. The method is based on insertion, advection, and decay of dye. To this aim, we extend the texture-based IBFV technique for 2D flow visualization in two main directions. First, we decompose the 3D flow visualization problem in a
3D Elevation Program—Virtual USA in 3D
Lukas, Vicki; Stoker, J.M.
2016-04-14
The U.S. Geological Survey (USGS) 3D Elevation Program (3DEP) uses a laser system called ‘lidar’ (light detection and ranging) to create a virtual reality map of the Nation that is very accurate. 3D maps have many uses with new uses being discovered all the time.
Interactive 3D multimedia content
Cellary, Wojciech
2012-01-01
The book describes recent research results in the areas of modelling, creation, management and presentation of interactive 3D multimedia content. The book describes the current state of the art in the field and identifies the most important research and design issues. Consecutive chapters address these issues. These are: database modelling of 3D content, security in 3D environments, describing interactivity of content, searching content, visualization of search results, modelling mixed reality content, and efficient creation of interactive 3D content. Each chapter is illustrated with example a
Larsen, Rasmus
1997-01-01
. This includes the specification of a Gaussian distribution for the pixel values as well as a prior distribution for the configuration of class variables within the cross that is m ade of a pixel and its four nearest neighbours. We will extend this algorithm to 3-D, i.e. we will specify a simultaneous Gaussian...... distr ibution for a pixel and its 6 nearest 3-D neighbours, and generalise the class variable configuration distribution within the 3-D cross. The algorithm is tested on a synthetic 3-D multivariate dataset....
3D Bayesian contextual classifiers
Larsen, Rasmus
2000-01-01
We extend a series of multivariate Bayesian 2-D contextual classifiers to 3-D by specifying a simultaneous Gaussian distribution for the feature vectors as well as a prior distribution of the class variables of a pixel and its 6 nearest 3-D neighbours.......We extend a series of multivariate Bayesian 2-D contextual classifiers to 3-D by specifying a simultaneous Gaussian distribution for the feature vectors as well as a prior distribution of the class variables of a pixel and its 6 nearest 3-D neighbours....
Griffey, Jason
2014-01-01
As the maker movement continues to grow and 3-D printers become more affordable, an expanding group of hobbyists is keen to explore this new technology. In the time-honored tradition of introducing new technologies, many libraries are considering purchasing a 3-D printer. Jason Griffey, an early enthusiast of 3-D printing, has researched the marketplace and seen several systems first hand at the Consumer Electronics Show. In this report he introduces readers to the 3-D printing marketplace, covering such topics asHow fused deposition modeling (FDM) printing workBasic terminology such as build
Connell, Ellery
2011-01-01
Helping graphic designers expand their 2D skills into the 3D space The trend in graphic design is towards 3D, with the demand for motion graphics, animation, photorealism, and interactivity rapidly increasing. And with the meteoric rise of iPads, smartphones, and other interactive devices, the design landscape is changing faster than ever.2D digital artists who need a quick and efficient way to join this brave new world will want 3D for Graphic Designers. Readers get hands-on basic training in working in the 3D space, including product design, industrial design and visualization, modeling, ani
Simulations of 3D LPI's relevant to IFE using the PIC code OSIRIS
Tsung, F. S.; Mori, W. B.; Winjum, B. J.
2014-10-01
We will study three dimensional effects of laser plasma instabilities, including backward raman scattering, the high frequency hybrid instability, and the two plasmon instability using OSIRIS in 3D Cartesian geometry and cylindrical 2D OSIRIS with azimuthal mode decompositions. With our new capabilities we hope to demonstrate that we are capable of studying single speckle physics relevant to IFE in an efficent manner.
Spherical 3D Isotropic Wavelets
Lanusse, F; Starck, J -L
2011-01-01
Future cosmological surveys will provide 3D large scale structure maps with large sky coverage, for which a 3D Spherical Fourier-Bessel (SFB) analysis in is natural. Wavelets are particularly well-suited to the analysis and denoising of cosmological data, but a spherical 3D isotropic wavelet transform does not currently exist to analyse spherical 3D data. The aim of this paper is to present a new formalism for a spherical 3D isotropic wavelet, i.e. one based on the Fourier-Bessel decomposition of a 3D field and accompany the formalism with a public code to perform wavelet transforms. We describe a new 3D isotropic spherical wavelet decomposition based on the undecimated wavelet transform (UWT) described in Starck et al. 2006. We also present a new fast Discrete Spherical Fourier-Bessel Transform (DSFBT) based on both a discrete Bessel Transform and the HEALPIX angular pixelisation scheme. We test the 3D wavelet transform and as a toy-application, apply a denoising algorithm in wavelet space to the Virgo large...
无
2003-01-01
The disadvantage remaining in 3D scanning system and its reasons are discussed. A new host-and-slave structure with high speed image acquisition and processing system is proposed to quicken the image processing and improve the performance of 3D scanning system.
ECT Team, Purdue
2015-01-01
Building Bytes, by Brian Peters, is a project that uses desktop 3D printers to print bricks for architecture. Instead of using an expensive custom-made printer, it uses a normal standard 3D printer which is available for everyone and makes it more accessible and also easier for fabrication.
Pezzaniti, J. Larry; Edmondson, Richard; Vaden, Justin; Hyatt, Bryan; Chenault, David B.; Kingston, David; Geulen, Vanilynmae; Newell, Scott; Pettijohn, Brad
2009-02-01
In this paper, we report on the development of a 3D vision system consisting of a flat panel stereoscopic display and auto-converging stereo camera and an assessment of the system's use for robotic driving, manipulation, and surveillance operations. The 3D vision system was integrated onto a Talon Robot and Operator Control Unit (OCU) such that direct comparisons of the performance of a number of test subjects using 2D and 3D vision systems were possible. A number of representative scenarios were developed to determine which tasks benefited most from the added depth perception and to understand when the 3D vision system hindered understanding of the scene. Two tests were conducted at Fort Leonard Wood, MO with noncommissioned officers ranked Staff Sergeant and Sergeant First Class. The scenarios; the test planning, approach and protocols; the data analysis; and the resulting performance assessment of the 3D vision system are reported.
Walatka, Pamela P.; Buning, Pieter G.; Pierce, Larry; Elson, Patricia A.
1990-01-01
PLOT3D is a computer graphics program designed to visualize the grids and solutions of computational fluid dynamics. Seventy-four functions are available. Versions are available for many systems. PLOT3D can handle multiple grids with a million or more grid points, and can produce varieties of model renderings, such as wireframe or flat shaded. Output from PLOT3D can be used in animation programs. The first part of this manual is a tutorial that takes the reader, keystroke by keystroke, through a PLOT3D session. The second part of the manual contains reference chapters, including the helpfile, data file formats, advice on changing PLOT3D, and sample command files.
Dawood, A; Marti Marti, B; Sauret-Jackson, V; Darwood, A
2015-12-01
3D printing has been hailed as a disruptive technology which will change manufacturing. Used in aerospace, defence, art and design, 3D printing is becoming a subject of great interest in surgery. The technology has a particular resonance with dentistry, and with advances in 3D imaging and modelling technologies such as cone beam computed tomography and intraoral scanning, and with the relatively long history of the use of CAD CAM technologies in dentistry, it will become of increasing importance. Uses of 3D printing include the production of drill guides for dental implants, the production of physical models for prosthodontics, orthodontics and surgery, the manufacture of dental, craniomaxillofacial and orthopaedic implants, and the fabrication of copings and frameworks for implant and dental restorations. This paper reviews the types of 3D printing technologies available and their various applications in dentistry and in maxillofacial surgery.
Wood, Jo; Kirschenbauer, Sabine; Döllner, Jürgen
2005-01-01
The notion of three-dimensionality is applied to five stages of the visualization pipeline. While 3D visulization is most often associated with the visual mapping and representation of data, this chapter also identifies its role in the management and assembly of data, and in the media used...... to display 3D imagery. The extra cartographic degree of freedom offered by using 3D is explored and offered as a motivation for employing 3D in visualization. The use of VR and the construction of virtual environments exploit navigational and behavioral realism, but become most usefil when combined...... with abstracted representations embedded in a 3D space. The interactions between development of geovisualization, the technology used to implement it and the theory surrounding cartographic representation are explored. The dominance of computing technologies, driven particularly by the gaming industry...
ADT-3D Tumor Detection Assistant in 3D
Jaime Lazcano Bello
2008-12-01
Full Text Available The present document describes ADT-3D (Three-Dimensional Tumor Detector Assistant, a prototype application developed to assist doctors diagnose, detect and locate tumors in the brain by using CT scan. The reader may find on this document an introduction to tumor detection; ADT-3D main goals; development details; description of the product; motivation for its development; result’s study; and areas of applicability.
Unassisted 3D camera calibration
Atanassov, Kalin; Ramachandra, Vikas; Nash, James; Goma, Sergio R.
2012-03-01
With the rapid growth of 3D technology, 3D image capture has become a critical part of the 3D feature set on mobile phones. 3D image quality is affected by the scene geometry as well as on-the-device processing. An automatic 3D system usually assumes known camera poses accomplished by factory calibration using a special chart. In real life settings, pose parameters estimated by factory calibration can be negatively impacted by movements of the lens barrel due to shaking, focusing, or camera drop. If any of these factors displaces the optical axes of either or both cameras, vertical disparity might exceed the maximum tolerable margin and the 3D user may experience eye strain or headaches. To make 3D capture more practical, one needs to consider unassisted (on arbitrary scenes) calibration. In this paper, we propose an algorithm that relies on detection and matching of keypoints between left and right images. Frames containing erroneous matches, along with frames with insufficiently rich keypoint constellations, are detected and discarded. Roll, pitch yaw , and scale differences between left and right frames are then estimated. The algorithm performance is evaluated in terms of the remaining vertical disparity as compared to the maximum tolerable vertical disparity.
Stanton, M M; Samitier, J; Sánchez, S
2015-08-07
Three-dimensional (3D) bioprinting has recently emerged as an extension of 3D material printing, by using biocompatible or cellular components to build structures in an additive, layer-by-layer methodology for encapsulation and culture of cells. These 3D systems allow for cell culture in a suspension for formation of highly organized tissue or controlled spatial orientation of cell environments. The in vitro 3D cellular environments simulate the complexity of an in vivo environment and natural extracellular matrices (ECM). This paper will focus on bioprinting utilizing hydrogels as 3D scaffolds. Hydrogels are advantageous for cell culture as they are highly permeable to cell culture media, nutrients, and waste products generated during metabolic cell processes. They have the ability to be fabricated in customized shapes with various material properties with dimensions at the micron scale. 3D hydrogels are a reliable method for biocompatible 3D printing and have applications in tissue engineering, drug screening, and organ on a chip models.
Tuotekehitysprojekti: 3D-tulostin
Pihlajamäki, Janne
2011-01-01
Opinnäytetyössä tutustuttiin 3D-tulostamisen teknologiaan. Työssä käytiin läpi 3D-tulostimesta tehty tuotekehitysprojekti. Sen lisäksi esiteltiin yleisellä tasolla tuotekehitysprosessi ja syntyneiden tulosten mahdollisia suojausmenetelmiä. Tavoitteena tässä työssä oli kehittää markkinoilta jo löytyvää kotitulostin-tasoista 3D-laiteteknologiaa lähemmäksi ammattilaistason ratkaisua. Tavoitteeseen pyrittiin keskittymällä parantamaan laitteella saavutettavaa tulostustarkkuutta ja -nopeutt...
Garrou , Philip; Ramm , Peter
2014-01-01
Edited by key figures in 3D integration and written by top authors from high-tech companies and renowned research institutions, this book covers the intricate details of 3D process technology.As such, the main focus is on silicon via formation, bonding and debonding, thinning, via reveal and backside processing, both from a technological and a materials science perspective. The last part of the book is concerned with assessing and enhancing the reliability of the 3D integrated devices, which is a prerequisite for the large-scale implementation of this emerging technology. Invaluable reading fo
无
2002-01-01
This paper presents a principle and a method of col or 3D laser scanning measurement. Based on the fundamental monochrome 3D measureme nt study, color information capture, color texture mapping, coordinate computati on and other techniques are performed to achieve color 3D measurement. The syste m is designed and composed of a line laser light emitter, one color CCD camera, a motor-driven rotary filter, a circuit card and a computer. Two steps in captu ring object's images in the measurement process: Firs...
Lin, Zeyu
2014-01-01
3D printing technology is introduced and defined in this Thesis. Some methods of 3D printing are illustrated and their principles are explained with pictures. Most of the essential parts are presented with pictures and their effects are explained within the whole system. Problems on Up! Plus 3D printer are solved and a DIY product is made with this machine. The processes of making product are recorded and the items which need to be noticed during the process are the highlight in this th...
Rich, D.O.; Pope, S.C.; DeLapp, J.G.
1994-10-01
In April, a 128 PE Cray T3D was installed at Los Alamos National Laboratory`s Advanced Computing Laboratory as part of the DOE`s High-Performance Parallel Processor Program (H4P). In conjunction with CRI, the authors implemented a 30 day acceptance test. The test was constructed in part to help them understand the strengths and weaknesses of the T3D. In this paper, they briefly describe the H4P and its goals. They discuss the design and implementation of the T3D acceptance test and detail issues that arose during the test. They conclude with a set of system requirements that must be addressed as the T3D system evolves.
Advanced 3-D Ultrasound Imaging
Rasmussen, Morten Fischer
The main purpose of the PhD project was to develop methods that increase the 3-D ultrasound imaging quality available for the medical personnel in the clinic. Acquiring a 3-D volume gives the medical doctor the freedom to investigate the measured anatomy in any slice desirable after the scan has...... been completed. This allows for precise measurements of organs dimensions and makes the scan more operator independent. Real-time 3-D ultrasound imaging is still not as widespread in use in the clinics as 2-D imaging. A limiting factor has traditionally been the low image quality achievable using...... Field II simulations and measurements with the ultrasound research scanner SARUS and a 3.5MHz 1024 element 2-D transducer array. In all investigations, 3-D synthetic aperture imaging achieved a smaller main-lobe, lower sidelobes, higher contrast, and better signal to noise ratio than parallel...
Conducting polymer 3D microelectrodes
Sasso, Luigi; Vazquez, Patricia; Vedarethinam, Indumathi
2010-01-01
Conducting polymer 3D microelectrodes have been fabricated for possible future neurological applications. A combination of micro-fabrication techniques and chemical polymerization methods has been used to create pillar electrodes in polyaniline and polypyrrole. The thin polymer films obtained...
Lading, Brian; Larsen, Rasmus; Astrom, K
2006-01-01
We build a 3D face shape model, including inter- and intra-shape variations, derive the analytical Jacobian of its resulting 2D rendered image, and show example of its fitting performance with light, pose, id, expression and texture variations......We build a 3D face shape model, including inter- and intra-shape variations, derive the analytical Jacobian of its resulting 2D rendered image, and show example of its fitting performance with light, pose, id, expression and texture variations...
Lading, Brian; Larsen, Rasmus; Åström, Kalle
2006-01-01
We build a 3d face shape model, including inter- and intra-shape variations, derive the analytical jacobian of its resulting 2d rendered image, and show example of its fitting performance with light, pose, id, expression and texture variations.}......We build a 3d face shape model, including inter- and intra-shape variations, derive the analytical jacobian of its resulting 2d rendered image, and show example of its fitting performance with light, pose, id, expression and texture variations.}...
Main: TATCCAYMOTIFOSRAMY3D [PLACE
Full Text Available TATCCAYMOTIFOSRAMY3D S000256 01-August-2006 (last modified) kehi TATCCAY motif foun...d in rice (O.s.) RAmy3D alpha-amylase gene promoter; Y=T/C; a GATA motif as its antisense sequence; TATCCAY ...motif and G motif (see S000130) are responsible for sugar repression (Toyofuku et al. 1998); GATA; amylase; sugar; repression; rice (Oryza sativa) TATCCAY ...
The instability of a horizontal magnetic field in an atmosphere stable against convection
Parker, E. N.
1979-01-01
The theoretical problem posed by the buoyant escape of a magnetic field from the interior of a stably stratified body bears directly on the question of the present existence of primordial magnetic fields in stars. This paper treats the onset of the Rayleigh-Taylor instability of the upper boundary of a uniform horizontal magnetic field in a stably stratified atmosphere. The calculations are carried out in the Boussinesq approximation and show the rapid growth of the initial infinitesimal perturbation of the boundary. This result is in contrast to the extremely slow buoyant rise of a separate flux tube in the same atmosphere. Thus for instance, at a depth of 1/3 of a solar radius beneath the surface of the sun, a field of 100 G develops ripples over a scale of 1000 km in a characteristic time of 50 years, whereas the characteristic rise time of the same field in separate flux tubes with the same dimensions is 10 billion years. Thus, the development of irregularities proceeds quickly, soon slowing, however, to a very slow pace when the amplitude of the irregularities becomes significant. Altogether, the calculations show the complexity of the question of the existence of remnant primordial magnetic fields in stellar interiors.
Simulation of direct contact condensation of steam jets based on interfacial instability theories
Heinze, David; Schulenberg, Thomas; Class, Andreas; Behnke, Lars
2014-11-01
A simulation model for the direct contact condensation of steam in subcooled water is presented that allows to determine major parameters of the process such as the jet penetration length. Entrainment of water by the steam jet is modeled based on the Kelvin-Helmholtz and Rayleigh-Taylor instability theories. Primary atomization due to acceleration of interfacial waves and secondary atomization due to aerodynamic forces account for the initial size of entrained droplets. The resulting steam-water two-phase flow is simulated based on a one-dimensional two-fluid model. An interfacial area transport equation is used to track changes of the interfacial area density due to droplet entrainment and steam condensation. Interfacial heat and mass transfer rates during condensation are calculated using the two-resistance model. The resulting two-phase flow equations constitute a system of ordinary differential equations which is discretized by means of an explicit Runge-Kutta method. The simulation results are in good agreement with published experimental data over a wide range of pool temperatures and mass flow rates. funded by RWE Power AG.
Hydrodynamic instabilities and mix studies on NIF: predictions, observations, and a path forward
Remington, B. A.; Atherton, L. J.; Benedetti, L. R.; Berzak-Hopkins, L.; Bradley, D. K.; Callahan, D. A.; Casey, D. T.; Celliers, P. M.; Cerjan, C. J.; Clark, D. S.; Dewald, E. L.; Dittrich, T. R.; Dixit, S. N.; Döppner, T.; Edgell, D. H.; Edwards, M. J.; Epstein, R.; Frenje, J.; Gatu-Johnson, M.; Glenn, S.; Glenzer, S. H.; Grim, G.; Haan, S. W.; Hammel, B. A.; Hamza, A.; Hicks, D.; Hsing, W. W.; Hurricane, O.; Izumi, N.; Jones, O. S.; Key, M. H.; Khan, S. F.; Kilkenny, J. D.; Kline, J. L.; Kyrala, G. A.; Landen, O. L.; Le Pape, S.; Lindl, J. D.; Ma, T.; MacGowan, B. J.; Mackinnon, A. J.; MacPhee, A. G.; Meezan, N. B.; Moody, J. D.; Moses, E. I.; Nikroo, A.; Pak, A.; Parham, T.; Park, H.-S.; Patel, P. K.; Petrasso, R.; Pino, J.; Ralph, J. E.; Raman, K.; Regan, S. P.; Robey, H. F.; Ross, J. S.; Spears, B. K.; Smalyuk, V. A.; Springer, P. T.; Suter, L. J.; Tipton, R.; Tommasini, R.; Town, R. P.; Weber, S. V.
2016-03-01
The goals of the Mix Campaign are to determine how mix affects performance, locate the “mix cliff”, locate the source of the mix, and develop mitigation methods that allow performance to be increased. We have used several different drive pulse shapes and capsule designs in the Mix Campaign, to understand sensitivity to drive peak power, level of coast, rise time to peak power, adiabat, and dopant level in the capsule. Ablator material mixing into the hot spot has been shown conclusively with x-ray spectroscopy. The observed neutron yield drops steeply when the hot spot mix mass becomes too large. The mix appears to be driven by ablation- front Rayleigh-Taylor instabilities. A high foot, higher adiabat drive has a more stable ablation front and has allowed the mix mass in the hot spot to be reduced significantly. Two recent high foot shots achieved neutron yields > 1015 and measured neutron yield over clean 1D simulation (YOC) > 50%, which was one of the central goals of the Mix Campaign.
MPML3D: Scripting Agents for the 3D Internet.
Prendinger, Helmut; Ullrich, Sebastian; Nakasone, Arturo; Ishizuka, Mitsuru
2011-05-01
The aim of this paper is two-fold. First, it describes a scripting language for specifying communicative behavior and interaction of computer-controlled agents ("bots") in the popular three-dimensional (3D) multiuser online world of "Second Life" and the emerging "OpenSimulator" project. While tools for designing avatars and in-world objects in Second Life exist, technology for nonprogrammer content creators of scenarios involving scripted agents is currently missing. Therefore, we have implemented new client software that controls bots based on the Multimodal Presentation Markup Language 3D (MPML3D), a highly expressive XML-based scripting language for controlling the verbal and nonverbal behavior of interacting animated agents. Second, the paper compares Second Life and OpenSimulator platforms and discusses the merits and limitations of each from the perspective of agent control. Here, we also conducted a small study that compares the network performance of both platforms.
Dima, M.; Farisato, G.; Bergomi, M.; Viotto, V.; Magrin, D.; Greggio, D.; Farinato, J.; Marafatto, L.; Ragazzoni, R.; Piazza, D.
2014-08-01
In the last few years 3D printing is getting more and more popular and used in many fields going from manufacturing to industrial design, architecture, medical support and aerospace. 3D printing is an evolution of bi-dimensional printing, which allows to obtain a solid object from a 3D model, realized with a 3D modelling software. The final product is obtained using an additive process, in which successive layers of material are laid down one over the other. A 3D printer allows to realize, in a simple way, very complex shapes, which would be quite difficult to be produced with dedicated conventional facilities. Thanks to the fact that the 3D printing is obtained superposing one layer to the others, it doesn't need any particular work flow and it is sufficient to simply draw the model and send it to print. Many different kinds of 3D printers exist based on the technology and material used for layer deposition. A common material used by the toner is ABS plastics, which is a light and rigid thermoplastic polymer, whose peculiar mechanical properties make it diffusely used in several fields, like pipes production and cars interiors manufacturing. I used this technology to create a 1:1 scale model of the telescope which is the hardware core of the space small mission CHEOPS (CHaracterising ExOPlanets Satellite) by ESA, which aims to characterize EXOplanets via transits observations. The telescope has a Ritchey-Chrétien configuration with a 30cm aperture and the launch is foreseen in 2017. In this paper, I present the different phases for the realization of such a model, focusing onto pros and cons of this kind of technology. For example, because of the finite printable volume (10×10×12 inches in the x, y and z directions respectively), it has been necessary to split the largest parts of the instrument in smaller components to be then reassembled and post-processed. A further issue is the resolution of the printed material, which is expressed in terms of layers
3D-mallinnus ja 3D-animaatiot biovoimalaitoksesta
Hiltula, Tytti
2014-01-01
Opinnäytetyössä tehtiin biovoimalaitoksen piirustuksista 3D-mallinnus ja animaatiot. Työn tarkoituksena oli saada valmiiksi Recwell Oy:lle markkinointiin tarkoitetut kuva- ja videomateriaalit. Työssä perehdyttiin 3D-mallintamisen perustietoihin ja lähtökohtiin sekä animaation laatimiseen. Työ laadittiin kokonaisuudessaan AutoCAD-ohjelmalla, ja työn aikana tutustuttiin huolellisesti myös ohjelman käyttöohjeisiin. Piirustusten mitoituksessa huomattiin jo alkuvaiheessa suuria puutteita, ...
The Blast-Wave-Driven Instability as a Vehicle for Understanding Supernova Explosion Structure
Miles, A R
2008-05-27
Blast-wave-driven instabilities play a rich and varied role throughout the evolution of supernovae from explosion to remnant, but interpreting their role is difficult due to the enormous complexity of the stellar systems. We consider the simpler and fundamental hydrodynamic instability problem of a material interface between two constant-density fluids perturbed from spherical and driven by a divergent central Taylor-Sedov blast wave. The existence of unified solutions at high Mach number and small density ratio suggests that general conclusions can be drawn about the likely asymptotic structure of the mixing zone. To this end we apply buoyancy-drag and bubble merger models modified to include the effects of divergence and radial velocity gradients. In general, these effects preclude the true self-similar evolution of classical Raleigh-Taylor, but can be incorporated into a quasi-self-similar growth picture. Loss of memory of initial conditions can occur in the quasi-self-similar model, but requires initial mode numbers higher than those predicted for pre-explosion interfaces in Type II SNe, suggesting that their late-time structure is likely strongly influenced by details of the initial perturbations. Where low-modes are dominant, as in the Type Ia Tycho remnant, they result from initial perturbations rather than generation from smaller scales. Therefore, structure observed now contains direct information about the explosion process. When large-amplitude modes are present in the initial conditions, the contribution to the perturbation growth from the Richtmyer-Meshkov instability is significant or dominant compared to Rayleigh-Taylor. Such Richtmyer-Meshkov growth can yield proximity of the forward shock to the growing spikes and structure that strongly resembles that observed in the Tycho. Laser-driven high-energy-density laboratory experiments offer a promising avenue for testing model and simulation descriptions of blast-wave-driven instabilities and making
FOREWORD: Second International Symposium on Instability and Bifurcations in Fluid Dynamics
Bar Yoseph, P. Z.; Brøns, M.; Gelfgat, A.; Sørensen, J. N.
2007-05-01
Hydrodynamic stability is of fundamental importance in fluid dynamics and is a well-established subject of scientific investigation that continues to attract great interest in the fluid mechanics community. Hydrodynamic instabilities of prototypical character are, for example, the Rayleigh-Bénard, the Taylor-Couette, the Bénard-Marangoni, the Rayleigh-Taylor, and the Kelvin-Helmholtz instabilities. A fundamental understanding of various patterns of bifurcations such as identifying the most dominant mechanisms responsible for the instability threshold is also required if one is to design reliable and efficient industrial processes and applications, such as melting, mixing, crystal growth, coating, welding, flow re-attachment over wings, and others. The collection of papers in this volume is a selection of the presentations given at the Second International Symposium on Instability and Bifurcations in Fluid Dynamics, Technical University of Denmark, 15-18 August 2006. With more than 40 invited and contributed papers the symposium gave an overview of the state-of-the art of the field including experimental, theoretical, and computational approaches to problems related to convection, effects of magnetic fields, wake flows, rotating flows, and many others. The complete program can be found at the conference website http://www2.mat.dtu.dk/BIFD2006/. The symposium was the follow-up of a minisymposium held as a part of the `International Conference on Computational and Experimental Engineering and Sciences', 26-29 July 2004, Madeira, Portugal. We hope it will be possible to continue this series of highly successful events with a third symposium in 2008. P Z Bar Yoseph, M Brøns, A Gelfgat and J N Sørensen Editors
YouDash3D: exploring stereoscopic 3D gaming for 3D movie theaters
Schild, Jonas; Seele, Sven; Masuch, Maic
2012-03-01
Along with the success of the digitally revived stereoscopic cinema, events beyond 3D movies become attractive for movie theater operators, i.e. interactive 3D games. In this paper, we present a case that explores possible challenges and solutions for interactive 3D games to be played by a movie theater audience. We analyze the setting and showcase current issues related to lighting and interaction. Our second focus is to provide gameplay mechanics that make special use of stereoscopy, especially depth-based game design. Based on these results, we present YouDash3D, a game prototype that explores public stereoscopic gameplay in a reduced kiosk setup. It features live 3D HD video stream of a professional stereo camera rig rendered in a real-time game scene. We use the effect to place the stereoscopic effigies of players into the digital game. The game showcases how stereoscopic vision can provide for a novel depth-based game mechanic. Projected trigger zones and distributed clusters of the audience video allow for easy adaptation to larger audiences and 3D movie theater gaming.
Dagiuklas, Tasos
2014-01-01
This book describes recent innovations in 3D media and technologies, with coverage of 3D media capturing, processing, encoding, and adaptation, networking aspects for 3D Media, and quality of user experience (QoE). The main contributions are based on the results of the FP7 European Projects ROMEO, which focus on new methods for the compression and delivery of 3D multi-view video and spatial audio, as well as the optimization of networking and compression jointly across the Future Internet (www.ict-romeo.eu). The delivery of 3D media to individual users remains a highly challenging problem due to the large amount of data involved, diverse network characteristics and user terminal requirements, as well as the user’s context such as their preferences and location. As the number of visual views increases, current systems will struggle to meet the demanding requirements in terms of delivery of constant video quality to both fixed and mobile users. ROMEO will design and develop hybrid-networking solutions that co...
Materialedreven 3d digital formgivning
Hansen, Flemming Tvede
2010-01-01
Formålet med forskningsprojektet er for det første at understøtte keramikeren i at arbejde eksperimenterende med digital formgivning, og for det andet at bidrage til en tværfaglig diskurs om brugen af digital formgivning. Forskningsprojektet fokuserer på 3d formgivning og derved på 3d digital...... formgivning og Rapid Prototyping (RP). RP er en fællesbetegnelse for en række af de teknikker, der muliggør at overføre den digitale form til 3d fysisk form. Forskningsprojektet koncentrerer sig om to overordnede forskningsspørgsmål. Det første handler om, hvordan viden og erfaring indenfor det keramiske...... fagområde kan blive udnyttet i forhold til 3d digital formgivning. Det andet handler om, hvad en sådan tilgang kan bidrage med, og hvordan den kan blive udnyttet i et dynamisk samspil med det keramiske materiale i formgivningen af 3d keramiske artefakter. Materialedreven formgivning er karakteriseret af en...
Dagiuklas, Tasos
2015-01-01
This book describes recent innovations in 3D media and technologies, with coverage of 3D media capturing, processing, encoding, and adaptation, networking aspects for 3D Media, and quality of user experience (QoE). The contributions are based on the results of the FP7 European Project ROMEO, which focuses on new methods for the compression and delivery of 3D multi-view video and spatial audio, as well as the optimization of networking and compression jointly across the future Internet. The delivery of 3D media to individual users remains a highly challenging problem due to the large amount of data involved, diverse network characteristics and user terminal requirements, as well as the user’s context such as their preferences and location. As the number of visual views increases, current systems will struggle to meet the demanding requirements in terms of delivery of consistent video quality to fixed and mobile users. ROMEO will present hybrid networking solutions that combine the DVB-T2 and DVB-NGH broadcas...
2002-01-01
In 1999, Genex submitted a proposal to Stennis Space Center for a volumetric 3-D display technique that would provide multiple users with a 360-degree perspective to simultaneously view and analyze 3-D data. The futuristic capabilities of the VolumeViewer(R) have offered tremendous benefits to commercial users in the fields of medicine and surgery, air traffic control, pilot training and education, computer-aided design/computer-aided manufacturing, and military/battlefield management. The technology has also helped NASA to better analyze and assess the various data collected by its satellite and spacecraft sensors. Genex capitalized on its success with Stennis by introducing two separate products to the commercial market that incorporate key elements of the 3-D display technology designed under an SBIR contract. The company Rainbow 3D(R) imaging camera is a novel, three-dimensional surface profile measurement system that can obtain a full-frame 3-D image in less than 1 second. The third product is the 360-degree OmniEye(R) video system. Ideal for intrusion detection, surveillance, and situation management, this unique camera system offers a continuous, panoramic view of a scene in real time.
Modification of 3D milling machine to 3D printer
Halamíček, Lukáš
2015-01-01
Tato práce se zabývá přestavbou gravírovací frézky na 3D tiskárnu. V první části se práce zabývá možnými technologiemi 3D tisku a možností jejich využití u přestavby. Dále jsou popsány a vybrány vhodné součásti pro přestavbu. V další části je realizováno řízení ohřevu podložky, trysky a řízení posuvu drátu pomocí softwaru TwinCat od společnosti Beckhoff na průmyslovém počítači. Výsledkem práce by měla být oživená 3D tiskárna. This thesis deals with rebuilding of engraving machine to 3D pri...
Aspects of defects in 3d-3d correspondence
Gang, Dongmin; Kim, Nakwoo; Romo, Mauricio; Yamazaki, Masahito
2016-10-01
In this paper we study supersymmetric co-dimension 2 and 4 defects in the compactification of the 6d (2, 0) theory of type A N -1 on a 3-manifold M . The so-called 3d-3d correspondence is a relation between complexified Chern-Simons theory (with gauge group SL(N,C) ) on M and a 3d N=2 theory T N [ M ]. We study this correspondence in the presence of supersymmetric defects, which are knots/links inside the 3-manifold. Our study employs a number of different methods: state-integral models for complex Chern-Simons theory, cluster algebra techniques, domain wall theory T [SU( N )], 5d N=2 SYM, and also supergravity analysis through holography. These methods are complementary and we find agreement between them. In some cases the results lead to highly non-trivial predictions on the partition function. Our discussion includes a general expression for the cluster partition function, which can be used to compute in the presence of maximal and certain class of non-maximal punctures when N > 2. We also highlight the non-Abelian description of the 3d N=2 T N [ M ] theory with defect included, when such a description is available. This paper is a companion to our shorter paper [1], which summarizes our main results.
Holbek, Simon
studies and in vivo. Phantom measurements are compared with their corresponding reference value, whereas the in vivo measurement is validated against the current golden standard for non-invasive blood velocity estimates, based on magnetic resonance imaging (MRI). The study concludes, that a high precision......, if this significant reduction in the element count can still provide precise and robust 3-D vector flow estimates in a plane. The study concludes that the RC array is capable of estimating precise 3-D vector flow both in a plane and in a volume, despite the low channel count. However, some inherent new challenges......For the last decade, the field of ultrasonic vector flow imaging has gotten an increasingly attention, as the technique offers a variety of new applications for screening and diagnostics of cardiovascular pathologies. The main purpose of this PhD project was therefore to advance the field of 3-D...
Pihl, Michael Johannes
The main purpose of this PhD project is to develop an ultrasonic method for 3D vector flow imaging. The motivation is to advance the field of velocity estimation in ultrasound, which plays an important role in the clinic. The velocity of blood has components in all three spatial dimensions, yet...... conventional methods can estimate only the axial component. Several approaches for 3D vector velocity estimation have been suggested, but none of these methods have so far produced convincing in vivo results nor have they been adopted by commercial manufacturers. The basis for this project is the Transverse...... on the TO fields are suggested. They can be used to optimize the TO method. In the third part, a TO method for 3D vector velocity estimation is proposed. It employs a 2D phased array transducer and decouples the velocity estimation into three velocity components, which are estimated simultaneously based on 5...
Walder, Christian; Breidt, Martin; Bulthoff, Heinrich
2009-01-01
We present a novel algorithm for the markerless tracking of deforming surfaces such as faces. We acquire a sequence of 3D scans along with color images at 40Hz. The data is then represented by implicit surface and color functions, using a novel partition-of-unity type method of efficiently...... combining local regressors using nearest neighbor searches. Both these functions act on the 4D space of 3D plus time, and use temporal information to handle the noise in individual scans. After interactive registration of a template mesh to the first frame, it is then automatically deformed to track...... the scanned surface, using the variation of both shape and color as features in a dynamic energy minimization problem. Our prototype system yields high-quality animated 3D models in correspondence, at a rate of approximately twenty seconds per timestep. Tracking results for faces and other objects...
3D Printed Bionic Nanodevices.
Kong, Yong Lin; Gupta, Maneesh K; Johnson, Blake N; McAlpine, Michael C
2016-06-01
The ability to three-dimensionally interweave biological and functional materials could enable the creation of bionic devices possessing unique and compelling geometries, properties, and functionalities. Indeed, interfacing high performance active devices with biology could impact a variety of fields, including regenerative bioelectronic medicines, smart prosthetics, medical robotics, and human-machine interfaces. Biology, from the molecular scale of DNA and proteins, to the macroscopic scale of tissues and organs, is three-dimensional, often soft and stretchable, and temperature sensitive. This renders most biological platforms incompatible with the fabrication and materials processing methods that have been developed and optimized for functional electronics, which are typically planar, rigid and brittle. A number of strategies have been developed to overcome these dichotomies. One particularly novel approach is the use of extrusion-based multi-material 3D printing, which is an additive manufacturing technology that offers a freeform fabrication strategy. This approach addresses the dichotomies presented above by (1) using 3D printing and imaging for customized, hierarchical, and interwoven device architectures; (2) employing nanotechnology as an enabling route for introducing high performance materials, with the potential for exhibiting properties not found in the bulk; and (3) 3D printing a range of soft and nanoscale materials to enable the integration of a diverse palette of high quality functional nanomaterials with biology. Further, 3D printing is a multi-scale platform, allowing for the incorporation of functional nanoscale inks, the printing of microscale features, and ultimately the creation of macroscale devices. This blending of 3D printing, novel nanomaterial properties, and 'living' platforms may enable next-generation bionic systems. In this review, we highlight this synergistic integration of the unique properties of nanomaterials with the
Georgette B. Salieb-Beugelaar
2016-10-01
Full Text Available Polymeric microfluidic systems are well suited for miniaturized devices with complex functionality, and rapid prototyping methods for 3D microfluidic structures are increasingly used. Mixing at the microscale and performing chemical reactions at the microscale are important applications of such systems and we therefore explored feasibility, mixing characteristics and the ability to control a chemical reaction in helical 3D channels produced by the emerging thread template method. Mixing at the microscale is challenging because channel size reduction for improving solute diffusion comes at the price of a reduced Reynolds number that induces a strictly laminar flow regime and abolishes turbulence that would be desired for improved mixing. Microfluidic 3D helix mixers were rapidly prototyped in polydimethylsiloxane (PDMS using low-surface energy polymeric threads, twisted to form 2-channel and 3-channel helices. Structure and flow characteristics were assessed experimentally by microscopy, hydraulic measurements and chromogenic reaction, and were modeled by computational fluid dynamics. We found that helical 3D microfluidic systems produced by thread templating allow rapid prototyping, can be used for mixing and for controlled chemical reaction with two or three reaction partners at the microscale. Compared to the conventional T-shaped microfluidic system used as a control device, enhanced mixing and faster chemical reaction was found to occur due to the combination of diffusive mixing in small channels and flow folding due to the 3D helix shape. Thus, microfluidic 3D helix mixers can be rapidly prototyped using the thread template method and are an attractive and competitive method for fluid mixing and chemical reactions at the microscale.
Hydrodynamic Instability, Integrated Code, Laboratory Astrophysics, and Astrophysics
Takabe, Hideaki
2016-10-01
This is an article for the memorial lecture of Edward Teller Medal and is presented as memorial lecture at the IFSA03 conference held on September 12th, 2003, at Monterey, CA. The author focuses on his main contributions to fusion science and its extension to astrophysics in the field of theory and computation by picking up five topics. The first one is the anomalous resisitivity to hot electrons penetrating over-dense region through the ion wave turbulence driven by the return current compensating the current flow by the hot electrons. It is concluded that almost the same value of potential as the average kinetic energy of the hot electrons is realized to prevent the penetration of the hot electrons. The second is the ablative stabilization of Rayleigh-Taylor instability at ablation front and its dispersion relation so-called Takabe formula. This formula gave a principal guideline for stable target design. The author has developed an integrated code ILESTA (ID & 2D) for analyses and design of laser produced plasma including implosion dynamics. It is also applied to design high gain targets. The third is the development of the integrated code ILESTA. The forth is on Laboratory Astrophysics with intense lasers. This consists of two parts; one is review on its historical background and the other is on how we relate laser plasma to wide-ranging astrophysics and the purposes for promoting such research. In relation to one purpose, I gave a comment on anomalous transport of relativistic electrons in Fast Ignition laser fusion scheme. Finally, I briefly summarize recent activity in relation to application of the author's experience to the development of an integrated code for studying extreme phenomena in astrophysics.
Manos, Harry
2016-01-01
Visual aids are important to student learning, and they help make the teacher's job easier. Keeping with the "TPT" theme of "The Art, Craft, and Science of Physics Teaching," the purpose of this article is to show how teachers, lacking equipment and funds, can construct a durable 3-D model reference frame and a model gravity…
Pedersen, Pernille Klarskov; Strikwerda, Andrew; Wang, Tianwu
2013-01-01
We present a characterization of THz beams generated in both a two-color air plasma and in a LiNbO3 crystal. Using a commercial THz camera, we record intensity images as a function of distance through the beam waist, from which we extract 2D beam profiles and visualize our measurements into 3D beam...
3D Printing: Exploring Capabilities
Samuels, Kyle; Flowers, Jim
2015-01-01
As 3D printers become more affordable, schools are using them in increasing numbers. They fit well with the emphasis on product design in technology and engineering education, allowing students to create high-fidelity physical models to see and test different iterations in their product designs. They may also help students to "think in three…
无
2011-01-01
The presentation of the vanguard work,My Dream3D,the innovative production by the China Disabled People’s Performing Art Troupe(CDPPAT),directed by Joy Joosang Park,provided the film’s domestic premiere at Beijing’s Olympic Park onApril7.The show provided an intriguing insight not
Priprava 3D modelov za 3D tisk
2015-01-01
Po mnenju nekaterih strokovnjakov bo aditivna proizvodnja (ali 3D tiskanje) spremenila proizvodnjo industrijo, saj si bo vsak posameznik lahko natisnil svoj objekt po želji. V diplomski nalogi so predstavljene nekatere tehnologije aditivne proizvodnje. V nadaljevanju diplomske naloge je predstavljena izdelava makete hiše v merilu 1:100, vse od modeliranja do tiskanja. Poseben poudarek je posvečen predelavi modela, da je primeren za tiskanje, kjer je razvit pristop za hitrejše i...
Post processing of 3D models for 3D printing
2015-01-01
According to the opinion of some experts the additive manufacturing or 3D printing will change manufacturing industry, because any individual could print their own model according to his or her wishes. In this graduation thesis some of the additive manufacturing technologies are presented. Furthermore in the production of house scale model in 1:100 is presented, starting from modeling to printing. Special attention is given to postprocessing of the building model elements us...
Forensic 3D Scene Reconstruction
LITTLE,CHARLES Q.; PETERS,RALPH R.; RIGDON,J. BRIAN; SMALL,DANIEL E.
1999-10-12
Traditionally law enforcement agencies have relied on basic measurement and imaging tools, such as tape measures and cameras, in recording a crime scene. A disadvantage of these methods is that they are slow and cumbersome. The development of a portable system that can rapidly record a crime scene with current camera imaging, 3D geometric surface maps, and contribute quantitative measurements such as accurate relative positioning of crime scene objects, would be an asset to law enforcement agents in collecting and recording significant forensic data. The purpose of this project is to develop a feasible prototype of a fast, accurate, 3D measurement and imaging system that would support law enforcement agents to quickly document and accurately record a crime scene.
Pizarro, Yaritzmar Rosario; Schuler, Jason M.; Lippitt, Thomas C.
2013-01-01
Dexterous robotic hands are changing the way robots and humans interact and use common tools. Unfortunately, the complexity of the joints and actuations drive up the manufacturing cost. Some cutting edge and commercially available rapid prototyping machines now have the ability to print multiple materials and even combine these materials in the same job. A 3D model of a robotic hand was designed using Creo Parametric 2.0. Combining "hard" and "soft" materials, the model was printed on the Object Connex350 3D printer with the purpose of resembling as much as possible the human appearance and mobility of a real hand while needing no assembly. After printing the prototype, strings where installed as actuators to test mobility. Based on printing materials, the manufacturing cost of the hand was $167, significantly lower than other robotic hands without the actuators since they have more complex assembly processes.
3D Printable Graphene Composite.
Wei, Xiaojun; Li, Dong; Jiang, Wei; Gu, Zheming; Wang, Xiaojuan; Zhang, Zengxing; Sun, Zhengzong
2015-07-08
In human being's history, both the Iron Age and Silicon Age thrived after a matured massive processing technology was developed. Graphene is the most recent superior material which could potentially initialize another new material Age. However, while being exploited to its full extent, conventional processing methods fail to provide a link to today's personalization tide. New technology should be ushered in. Three-dimensional (3D) printing fills the missing linkage between graphene materials and the digital mainstream. Their alliance could generate additional stream to push the graphene revolution into a new phase. Here we demonstrate for the first time, a graphene composite, with a graphene loading up to 5.6 wt%, can be 3D printable into computer-designed models. The composite's linear thermal coefficient is below 75 ppm·°C(-1) from room temperature to its glass transition temperature (Tg), which is crucial to build minute thermal stress during the printing process.
Medical 3D thermography system
GRUBIŠIĆ, IVAN
2011-01-01
Infrared (IR) thermography determines the surface temperature of an object or human body using thermal IR measurement camera. It is an imaging technology which is contactless and completely non-invasive. These propertiesmake IR thermography a useful method of analysis that is used in various industrial applications to detect, monitor and predict irregularities in many fields from engineering to medical and biological observations. This paper presents a conceptual model of Medical 3D Thermo...
Parzefall, Ulrich [Physikalisches Institut, Universitaet Freiburg, Hermann-Herder-Str. 3, D-79104 Freiburg (Germany)], E-mail: ulrich.parzefall@physik.uni-freiburg.de; Bates, Richard [University of Glasgow, Department of Physics and Astronomy, Glasgow G12 8QQ (United Kingdom); Boscardin, Maurizio [FBK-irst, Center for Materials and Microsystems, via Sommarive 18, 38050 Povo di Trento (Italy); Dalla Betta, Gian-Franco [INFN and Universita' di Trento, via Sommarive 14, 38050 Povo di Trento (Italy); Eckert, Simon [Physikalisches Institut, Universitaet Freiburg, Hermann-Herder-Str. 3, D-79104 Freiburg (Germany); Eklund, Lars; Fleta, Celeste [University of Glasgow, Department of Physics and Astronomy, Glasgow G12 8QQ (United Kingdom); Jakobs, Karl; Kuehn, Susanne [Physikalisches Institut, Universitaet Freiburg, Hermann-Herder-Str. 3, D-79104 Freiburg (Germany); Lozano, Manuel [Instituto de Microelectronica de Barcelona, IMB-CNM, CSIC, Barcelona (Spain); Pahn, Gregor [Physikalisches Institut, Universitaet Freiburg, Hermann-Herder-Str. 3, D-79104 Freiburg (Germany); Parkes, Chris [University of Glasgow, Department of Physics and Astronomy, Glasgow G12 8QQ (United Kingdom); Pellegrini, Giulio [Instituto de Microelectronica de Barcelona, IMB-CNM, CSIC, Barcelona (Spain); Pennicard, David [University of Glasgow, Department of Physics and Astronomy, Glasgow G12 8QQ (United Kingdom); Piemonte, Claudio; Ronchin, Sabina [FBK-irst, Center for Materials and Microsystems, via Sommarive 18, 38050 Povo di Trento (Italy); Szumlak, Tomasz [University of Glasgow, Department of Physics and Astronomy, Glasgow G12 8QQ (United Kingdom); Zoboli, Andrea [INFN and Universita' di Trento, via Sommarive 14, 38050 Povo di Trento (Italy); Zorzi, Nicola [FBK-irst, Center for Materials and Microsystems, via Sommarive 18, 38050 Povo di Trento (Italy)
2009-06-01
While the Large Hadron Collider (LHC) at CERN has started operation in autumn 2008, plans for a luminosity upgrade to the Super-LHC (sLHC) have already been developed for several years. This projected luminosity increase by an order of magnitude gives rise to a challenging radiation environment for tracking detectors at the LHC experiments. Significant improvements in radiation hardness are required with respect to the LHC. Using a strawman layout for the new tracker of the ATLAS experiment as an example, silicon strip detectors (SSDs) with short strips of 2-3 cm length are foreseen to cover the region from 28 to 60 cm distance to the beam. These SSD will be exposed to radiation levels up to 10{sup 15}N{sub eq}/cm{sup 2}, which makes radiation resistance a major concern for the upgraded ATLAS tracker. Several approaches to increasing the radiation hardness of silicon detectors exist. In this article, it is proposed to combine the radiation hard 3D-design originally conceived for pixel-style applications with the benefits of the established planar technology for strip detectors by using SSDs that have regularly spaced doped columns extending into the silicon bulk under the detector strips. The first 3D SSDs to become available for testing were made in the Single Type Column (STC) design, a technological simplification of the original 3D design. With such 3D SSDs, a small number of prototype sLHC detector modules with LHC-speed front-end electronics as used in the semiconductor tracking systems of present LHC experiments were built. Modules were tested before and after irradiation to fluences of 10{sup 15}N{sub eq}/cm{sup 2}. The tests were performed with three systems: a highly focused IR-laser with 5{mu}m spot size to make position-resolved scans of the charge collection efficiency, an Sr{sup 90}{beta}-source set-up to measure the signal levels for a minimum ionizing particle (MIP), and a beam test with 180 GeV pions at CERN. This article gives a brief overview of
FROILAN G. DESTREZA
2014-02-01
Full Text Available This study is for the BSHRM Students of Batangas State University (BatStateU ARASOF for the researchers believe that the Wireless 3D Chocolate Printer would be helpful in their degree program especially on making creative, artistic, personalized and decorative chocolate designs. The researchers used the Prototyping model as procedural method for the successful development and implementation of the hardware and software. This method has five phases which are the following: quick plan, quick design, prototype construction, delivery and feedback and communication. This study was evaluated by the BSHRM Students and the assessment of the respondents regarding the software and hardware application are all excellent in terms of Accuracy, Effecitveness, Efficiency, Maintainability, Reliability and User-friendliness. Also, the overall level of acceptability of the design project as evaluated by the respondents is excellent. With regard to the observation about the best raw material to use in 3D printing, the chocolate is good to use as the printed material is slightly distorted,durable and very easy to prepare; the icing is also good to use as the printed material is not distorted and is very durable but consumes time to prepare; the flour is not good as the printed material is distorted, not durable but it is easy to prepare. The computation of the economic viability level of 3d printer with reference to ROI is 37.14%. The recommendation of the researchers in the design project are as follows: adding a cooling system so that the raw material will be more durable, development of a more simplified version and improving the extrusion process wherein the user do not need to stop the printing process just to replace the empty syringe with a new one.
Interactive 3D Mars Visualization
Powell, Mark W.
2012-01-01
The Interactive 3D Mars Visualization system provides high-performance, immersive visualization of satellite and surface vehicle imagery of Mars. The software can be used in mission operations to provide the most accurate position information for the Mars rovers to date. When integrated into the mission data pipeline, this system allows mission planners to view the location of the rover on Mars to 0.01-meter accuracy with respect to satellite imagery, with dynamic updates to incorporate the latest position information. Given this information so early in the planning process, rover drivers are able to plan more accurate drive activities for the rover than ever before, increasing the execution of science activities significantly. Scientifically, this 3D mapping information puts all of the science analyses to date into geologic context on a daily basis instead of weeks or months, as was the norm prior to this contribution. This allows the science planners to judge the efficacy of their previously executed science observations much more efficiently, and achieve greater science return as a result. The Interactive 3D Mars surface view is a Mars terrain browsing software interface that encompasses the entire region of exploration for a Mars surface exploration mission. The view is interactive, allowing the user to pan in any direction by clicking and dragging, or to zoom in or out by scrolling the mouse or touchpad. This set currently includes tools for selecting a point of interest, and a ruler tool for displaying the distance between and positions of two points of interest. The mapping information can be harvested and shared through ubiquitous online mapping tools like Google Mars, NASA WorldWind, and Worldwide Telescope.
吕铁雄
2011-01-01
难度:★★★★☆词数:450 建议阅读时间:8分钟 Most people see out of two eyes. This is a basic fact of humanity,but it’s what makes possible the illusion of depth(纵深幻觉) that 3-D movies create. Human eyes are spaced about two inches apart, meaning that each eye gives the brain a slightly different perspective(透视感)on the same object. The brain then uses this variance to quickly determine an object’s distance.
Virtual 3-D Facial Reconstruction
Martin Paul Evison
2000-06-01
Full Text Available Facial reconstructions in archaeology allow empathy with people who lived in the past and enjoy considerable popularity with the public. It is a common misconception that facial reconstruction will produce an exact likeness; a resemblance is the best that can be hoped for. Research at Sheffield University is aimed at the development of a computer system for facial reconstruction that will be accurate, rapid, repeatable, accessible and flexible. This research is described and prototypical 3-D facial reconstructions are presented. Interpolation models simulating obesity, ageing and ethnic affiliation are also described. Some strengths and weaknesses in the models, and their potential for application in archaeology are discussed.
3D medical thermography device
Moghadam, Peyman
2015-05-01
In this paper, a novel handheld 3D medical thermography system is introduced. The proposed system consists of a thermal-infrared camera, a color camera and a depth camera rigidly attached in close proximity and mounted on an ergonomic handle. As a practitioner holding the device smoothly moves it around the human body parts, the proposed system generates and builds up a precise 3D thermogram model by incorporating information from each new measurement in real-time. The data is acquired in motion, thus it provides multiple points of view. When processed, these multiple points of view are adaptively combined by taking into account the reliability of each individual measurement which can vary due to a variety of factors such as angle of incidence, distance between the device and the subject and environmental sensor data or other factors influencing a confidence of the thermal-infrared data when captured. Finally, several case studies are presented to support the usability and performance of the proposed system.
3D Printable Graphene Composite
Wei, Xiaojun; Li, Dong; Jiang, Wei; Gu, Zheming; Wang, Xiaojuan; Zhang, Zengxing; Sun, Zhengzong
2015-07-01
In human being’s history, both the Iron Age and Silicon Age thrived after a matured massive processing technology was developed. Graphene is the most recent superior material which could potentially initialize another new material Age. However, while being exploited to its full extent, conventional processing methods fail to provide a link to today’s personalization tide. New technology should be ushered in. Three-dimensional (3D) printing fills the missing linkage between graphene materials and the digital mainstream. Their alliance could generate additional stream to push the graphene revolution into a new phase. Here we demonstrate for the first time, a graphene composite, with a graphene loading up to 5.6 wt%, can be 3D printable into computer-designed models. The composite’s linear thermal coefficient is below 75 ppm·°C-1 from room temperature to its glass transition temperature (Tg), which is crucial to build minute thermal stress during the printing process.
Mannoor, Manu S; Jiang, Ziwen; James, Teena; Kong, Yong Lin; Malatesta, Karen A; Soboyejo, Winston O; Verma, Naveen; Gracias, David H; McAlpine, Michael C
2013-06-12
The ability to three-dimensionally interweave biological tissue with functional electronics could enable the creation of bionic organs possessing enhanced functionalities over their human counterparts. Conventional electronic devices are inherently two-dimensional, preventing seamless multidimensional integration with synthetic biology, as the processes and materials are very different. Here, we present a novel strategy for overcoming these difficulties via additive manufacturing of biological cells with structural and nanoparticle derived electronic elements. As a proof of concept, we generated a bionic ear via 3D printing of a cell-seeded hydrogel matrix in the anatomic geometry of a human ear, along with an intertwined conducting polymer consisting of infused silver nanoparticles. This allowed for in vitro culturing of cartilage tissue around an inductive coil antenna in the ear, which subsequently enables readout of inductively-coupled signals from cochlea-shaped electrodes. The printed ear exhibits enhanced auditory sensing for radio frequency reception, and complementary left and right ears can listen to stereo audio music. Overall, our approach suggests a means to intricately merge biologic and nanoelectronic functionalities via 3D printing.
3D biometrics systems and applications
Zhang, David
2013-01-01
Includes discussions on popular 3D imaging technologies, combines them with biometric applications, and then presents real 3D biometric systems Introduces many efficient 3D feature extraction, matching, and fusion algorithms Techniques presented have been supported by experimental results using various 3D biometric classifications
3D Printing of Graphene Aerogels.
Zhang, Qiangqiang; Zhang, Feng; Medarametla, Sai Pradeep; Li, Hui; Zhou, Chi; Lin, Dong
2016-04-01
3D printing of a graphene aerogel with true 3D overhang structures is highlighted. The aerogel is fabricated by combining drop-on-demand 3D printing and freeze casting. The water-based GO ink is ejected and freeze-cast into designed 3D structures. The lightweight (<10 mg cm(-3) ) 3D printed graphene aerogel presents superelastic and high electrical conduction.
Gravitational instability due to the dissolution of carbon dioxide in a Hele-Shaw cell
Vreme, A.; Nadal, F.; Pouligny, B.; Jeandet, P.; Liger-Belair, G.; Meunier, P.
2016-10-01
We present an experimental study of the gravitational instability triggered by dissolution of carbon dioxide through a water-gas interface. We restrict the study to vertical parallelepipedic Hele-Shaw geometries, for which the thickness is smaller than the other dimensions. The partial pressure of carbon dioxide is quickly increased, leading to a denser layer of CO2-enriched water underneath the surface. This initially one-dimensional diffusive layer destabilizes through a convection-diffusion process. The concentration field of carbon dioxide, which is visualized by means of a pH-sensitive dye, shows a fingering pattern whose characteristics (wavelength and amplitude growth rate) are functions of the Rayleigh (Ra) and the Darcy (Da) numbers. At low Rayleigh numbers, the growth rate and the wave numbers are independent of the Rayleigh number and in excellent agreement with the classical results obtained numerically and theoretically in the Darcy regime. However, above a threshold of Ra√{Da} of the order of 10, the growth rate and the wave number strongly decrease due to the Brinkman term associated with the viscous diffusion in the vertical and longitudinal directions. In this Darcy-Brinkman regime, the growth rate and the wave number depend only on the thickness-based Rayleigh number Ra√{Da} . The classical Rayleigh-Taylor theory including the Brinkman term has been extended to this diffusive gravitational instability and gives an excellent prediction of the growth rate over four decades of Rayleigh numbers. However, the Brinkman regime seems to be valid only until Ra√{Da}=1000 . Above this threshold, the transverse velocity profile is no longer parabolic, which leads to an overestimation of the wave number by the theory.
Conducting Polymer 3D Microelectrodes
Jenny Emnéus
2010-12-01
Full Text Available Conducting polymer 3D microelectrodes have been fabricated for possible future neurological applications. A combination of micro-fabrication techniques and chemical polymerization methods has been used to create pillar electrodes in polyaniline and polypyrrole. The thin polymer films obtained showed uniformity and good adhesion to both horizontal and vertical surfaces. Electrodes in combination with metal/conducting polymer materials have been characterized by cyclic voltammetry and the presence of the conducting polymer film has shown to increase the electrochemical activity when compared with electrodes coated with only metal. An electrochemical characterization of gold/polypyrrole electrodes showed exceptional electrochemical behavior and activity. PC12 cells were finally cultured on the investigated materials as a preliminary biocompatibility assessment. These results show that the described electrodes are possibly suitable for future in-vitro neurological measurements.
2009-01-01
of the wavelength shift is related to the speed of motion, one can determine how fast the debris are moving in either direction. Because Cas A is the result of an explosion, the stellar debris is expanding radially outwards from the explosion center. Using simple geometry, the scientists were able to construct a 3-D model using all of this information. A program called 3-D Slicer modified for astronomical use by the Astronomical Medicine Project at Harvard University in Cambridge, Mass. was used to display and manipulate the 3-D model. Commercial software was then used to create the 3-D fly-through. The blue filaments defining the blast wave were not mapped using the Doppler effect because they emit a different kind of light synchrotron radiation that does not emit light at discrete wavelengths, but rather in a broad continuum. The blue filaments are only a representation of the actual filaments observed at the blast wave. This visualization shows that there are two main components to this supernova remnant: a spherical component in the outer parts of the remnant and a flattened (disk-like) component in the inner region. The spherical component consists of the outer layer of the star that exploded, probably made of helium and carbon. These layers drove a spherical blast wave into the diffuse gas surrounding the star. The flattened component that astronomers were unable to map into 3-D prior to these Spitzer observations consists of the inner layers of the star. It is made from various heavier elements, not all shown in the visualization, such as oxygen, neon, silicon, sulphur, argon and iron. High-velocity plumes, or jets, of this material are shooting out from the explosion in the plane of the disk-like component mentioned above. Plumes of silicon appear in the northeast and southwest, while those of iron are seen in the southeast and north. These jets were already known and Doppler velocity measurements have been made for these structures, but their orientation and
Olazabal-Loume, M.; Hallo, L. [Bordeaux-1 Univ., CELIA UMR 5107, 33 - Talence (France)
2006-06-15
This study deals with the hydrodynamic stability of a planar target in the context of inertial confinement fusion direct drive. Recently, different schemes have been proposed in order to reduce ablative Rayleigh-Taylor growth. They are based on the target adiabatic shaping in the ablation zone. In this work, we consider an adiabatic shaping scheme by relaxation: a prepulse is followed by a relaxation period where the laser is turned off. A numerical study is performed with a perturbation code dedicated to the linear stability analysis. The simulations show stabilizing effects of the relaxation scheme on the linear Rayleigh-Taylor growth rate. Influence of the picket parameters is also discussed. (authors)
Pathak, Naveen; Zhidkov, Alexei; Nakanii, Nobuhiko; Masuda, Shinichi; Hosokai, Tomonao; Kodama, Ryosuke
2016-03-01
Propagation of relativistically intense azimuthally or radially polarized laser pulses (RPP) is demonstrated, via 3D particle-in-cell simulations, to be unstable in uniform underdense plasma. Strong breaking of the pulse symmetry occurs for RPP with power exceeding the critical one for self-focusing in transversely uniform plasma with an increment, Γ, close to the well-known Rayleigh-Taylor-like instability depending on the acceleration, α, and the modulated density gradient length, L, as Γ≈(α/L) 1 /2 . In deeper plasma channels, the instability vanishes. Electron self-injection in the pulse wake and resulting acceleration is explored.
3D toroidal physics: testing the boundaries of symmetry breaking
Spong, Don
2014-10-01
Toroidal symmetry is an important concept for plasma confinement; it allows the existence of nested flux surface MHD equilibria and conserved invariants for particle motion. However, perfect symmetry is unachievable in realistic toroidal plasma devices. For example, tokamaks have toroidal ripple due to discrete field coils, optimized stellarators do not achieve exact quasi-symmetry, the plasma itself continually seeks lower energy states through helical 3D deformations, and reactors will likely have non-uniform distributions of ferritic steel near the plasma. Also, some level of designed-in 3D magnetic field structure is now anticipated for most concepts in order to lead to a stable, steady-state fusion reactor. Such planned 3D field structures can take many forms, ranging from tokamaks with weak 3D ELM-suppression fields to stellarators with more dominant 3D field structures. There is considerable interest in the development of unified physics models for the full range of 3D effects. Ultimately, the questions of how much symmetry breaking can be tolerated and how to optimize its design must be addressed for all fusion concepts. Fortunately, significant progress is underway in theory, computation and plasma diagnostics on many issues such as magnetic surface quality, plasma screening vs. amplification of 3D perturbations, 3D transport, influence on edge pedestal structures, MHD stability effects, modification of fast ion-driven instabilities, prediction of energetic particle heat loads on plasma-facing materials, effects of 3D fields on turbulence, and magnetic coil design. A closely coupled program of simulation, experimental validation, and design optimization is required to determine what forms and amplitudes of 3D shaping and symmetry breaking will be compatible with future fusion reactors. The development of models to address 3D physics and progress in these areas will be described. This work is supported both by the US Department of Energy under Contract DE
3D multiplexed immunoplasmonics microscopy
Bergeron, Éric; Patskovsky, Sergiy; Rioux, David; Meunier, Michel
2016-07-01
Selective labelling, identification and spatial distribution of cell surface biomarkers can provide important clinical information, such as distinction between healthy and diseased cells, evolution of a disease and selection of the optimal patient-specific treatment. Immunofluorescence is the gold standard for efficient detection of biomarkers expressed by cells. However, antibodies (Abs) conjugated to fluorescent dyes remain limited by their photobleaching, high sensitivity to the environment, low light intensity, and wide absorption and emission spectra. Immunoplasmonics is a novel microscopy method based on the visualization of Abs-functionalized plasmonic nanoparticles (fNPs) targeting cell surface biomarkers. Tunable fNPs should provide higher multiplexing capacity than immunofluorescence since NPs are photostable over time, strongly scatter light at their plasmon peak wavelengths and can be easily functionalized. In this article, we experimentally demonstrate accurate multiplexed detection based on the immunoplasmonics approach. First, we achieve the selective labelling of three targeted cell surface biomarkers (cluster of differentiation 44 (CD44), epidermal growth factor receptor (EGFR) and voltage-gated K+ channel subunit KV1.1) on human cancer CD44+ EGFR+ KV1.1+ MDA-MB-231 cells and reference CD44- EGFR- KV1.1+ 661W cells. The labelling efficiency with three stable specific immunoplasmonics labels (functionalized silver nanospheres (CD44-AgNSs), gold (Au) NSs (EGFR-AuNSs) and Au nanorods (KV1.1-AuNRs)) detected by reflected light microscopy (RLM) is similar to the one with immunofluorescence. Second, we introduce an improved method for 3D localization and spectral identification of fNPs based on fast z-scanning by RLM with three spectral filters corresponding to the plasmon peak wavelengths of the immunoplasmonics labels in the cellular environment (500 nm for 80 nm AgNSs, 580 nm for 100 nm AuNSs and 700 nm for 40 nm × 92 nm AuNRs). Third, the developed
LSWS linked with the low-latitude Es and its implications for the growth of the R-T instability
Joshi, L. M.
2016-07-01
A comprehensive investigation of spread F irregularities over the Indian sector has been carried out using VHF radar and ionosonde observations. Two different categories of spread F observations, one where the onset of the range spread F (RSF) was concurrent with the peak h'F (category 1) and another where the RSF onset happened ~90 min after the peak h'F time (category 2), are presented. RSF in category 2 was preceded by the presence of oblique echoes in ionograms, indicating the irregularity genesis westward of Sriharikota. The average peak h'F in category 1 was ~30 km higher than that in category 2 indicating the presence of standing large-scale wave structure (LSWS). Occurrence of the blanketing Es during 19:30 to 20:30 Indian Standard Time in category 1 (category 2) was 0% (>50%). Model computation is also carried out to further substantiate the observational results. Model computation indicates that zonal variation of low-latitude Es can generate zonal modulation in the F layer height rise. It is found that the modulation of the F layer height, linked with the low-latitude Es, assists the equatorial spread F onset by modifying both the growth rate of the collisional Rayleigh-Taylor (R-T) instability and also its efficiency. A predominant presence of low-latitude Es has been observed, but the increase in the F layer height and the R-T instability growth in the evening hours will maximize with complete absence of low-latitude Es. A new mechanism for the generation of LSWS and its implications on R-T instability is discussed.
Kuvaus 3D-tulostamisesta hammastekniikassa
Munne, Mauri; Mustonen, Tuomas; Vähäjylkkä, Jaakko
2013-01-01
3D-tulostaminen kehittyy nopeasti ja yleistyy koko ajan. Tulostimien tarkkuuksien kehittyessä 3D-tulostus on ottamassa myös jalansijaa hammastekniikan alalta. Tämän opinnäytetyön tarkoituksena on kuvata 3D-tulostamisen tilaa hammastekniikassa. 3D-tulostaminen on Suomessa vielä melko harvinaista, joten opinnäytetyön tavoitteena on koota yhteen kaikki mahdollinen tieto liittyen 3D-tulostamiseen hammastekniikassa. Tavoitteena on myös 3D-tulostimen testaaminen käytännössä aina suun skannaami...
Crowdsourcing Based 3d Modeling
Somogyi, A.; Barsi, A.; Molnar, B.; Lovas, T.
2016-06-01
Web-based photo albums that support organizing and viewing the users' images are widely used. These services provide a convenient solution for storing, editing and sharing images. In many cases, the users attach geotags to the images in order to enable using them e.g. in location based applications on social networks. Our paper discusses a procedure that collects open access images from a site frequently visited by tourists. Geotagged pictures showing the image of a sight or tourist attraction are selected and processed in photogrammetric processing software that produces the 3D model of the captured object. For the particular investigation we selected three attractions in Budapest. To assess the geometrical accuracy, we used laser scanner and DSLR as well as smart phone photography to derive reference values to enable verifying the spatial model obtained from the web-album images. The investigation shows how detailed and accurate models could be derived applying photogrammetric processing software, simply by using images of the community, without visiting the site.
The Origin and Kinematics of Cold Gas in Galactic Winds: Insight from Numerical Simulations
Fujita, Akimi; Mac Low, Mordecai-Mark; New, Kimberly C B; Weaver, Robert
2008-01-01
We study the origin of Na I absorbing gas in ultraluminous infrared galaxies motivated by the recent observations by Martin of extremely superthermal linewidths in this cool gas. We model the effects of repeated supernova explosions driving supershells in the central regions of molecular disks with M_d=10^{10} M_{\\odot}, using cylindrically symmetric gas dynamical simulations run with ZEUS-3D. The shocked swept-up shells quickly cool and fragment by Rayleigh-Taylor instability as they accelerate out of the dense, stratified disks. The numerical resolution of the cooling and compression at the shock fronts determines the peak shell density, and so the speed of Rayleigh-Taylor fragmentation. We identify cooled shells and shell fragments as Na I absorbing gas and study its kinematics along various sightlines across the grid. We find that simulations with a numerical resolution of \\le 0.2 pc produce multiple Rayleigh-Taylor fragmented shells in a given line of sight that appear to explain the observed kinematics....
3D Flash LIDAR Space Laser Project
National Aeronautics and Space Administration — Advanced Scientific Concepts, Inc. (ASC) is a small business that has developed 3D Flash LIDAR systems for space and terrestrial applications. 3D Flash LIDAR is...
Eesti 3D jaoks kitsas / Virge Haavasalu
Haavasalu, Virge
2009-01-01
Produktsioonifirma Digitaalne Sputnik: Kaur ja Kaspar Kallas tegelevad filmide produtseerimise ning 3D digitaalkaamerate tootearendusega (Silicon Imaging LLC). Vendade Kallaste 3D-kaamerast. Kommenteerib Eesti Filmi Sihtasutuse direktor Marge Liiske
Will 3D printers manufacture your meals?
Bommel, K.J.C. van
2013-01-01
These days, 3D printers are laying down plastics, metals, resins, and other materials in whatever configurations creative people can dream up. But when the next 3D printing revolution comes, you'll be able to eat it.
An interactive multiview 3D display system
Zhang, Zhaoxing; Geng, Zheng; Zhang, Mei; Dong, Hui
2013-03-01
The progresses in 3D display systems and user interaction technologies will help more effective 3D visualization of 3D information. They yield a realistic representation of 3D objects and simplifies our understanding to the complexity of 3D objects and spatial relationship among them. In this paper, we describe an autostereoscopic multiview 3D display system with capability of real-time user interaction. Design principle of this autostereoscopic multiview 3D display system is presented, together with the details of its hardware/software architecture. A prototype is built and tested based upon multi-projectors and horizontal optical anisotropic display structure. Experimental results illustrate the effectiveness of this novel 3D display and user interaction system.
Sliding Adjustment for 3D Video Representation
Galpin Franck
2002-01-01
Full Text Available This paper deals with video coding of static scenes viewed by a moving camera. We propose an automatic way to encode such video sequences using several 3D models. Contrary to prior art in model-based coding where 3D models have to be known, the 3D models are automatically computed from the original video sequence. We show that several independent 3D models provide the same functionalities as one single 3D model, and avoid some drawbacks of the previous approaches. To achieve this goal we propose a novel algorithm of sliding adjustment, which ensures consistency of successive 3D models. The paper presents a method to automatically extract the set of 3D models and associate camera positions. The obtained representation can be used for reconstructing the original sequence, or virtual ones. It also enables 3D functionalities such as synthetic object insertion, lightning modification, or stereoscopic visualization. Results on real video sequences are presented.
1997-01-01
Mars Pathfinder's forward rover ramp can be seen successfully unfurled in this image, taken in stereo by the Imager for Mars Pathfinder (IMP) on Sol 3. 3D glasses are necessary to identify surface detail. This ramp was not used for the deployment of the microrover Sojourner, which occurred at the end of Sol 2. When this image was taken, Sojourner was still latched to one of the lander's petals, waiting for the command sequence that would execute its descent off of the lander's petal.The image helped Pathfinder scientists determine whether to deploy the rover using the forward or backward ramps and the nature of the first rover traverse. The metallic object at the lower left of the image is the lander's low-gain antenna. The square at the end of the ramp is one of the spacecraft's magnetic targets. Dust that accumulates on the magnetic targets will later be examined by Sojourner's Alpha Proton X-Ray Spectrometer instrument for chemical analysis. At right, a lander petal is visible.The IMP is a stereo imaging system with color capability provided by 24 selectable filters -- twelve filters per 'eye.' It stands 1.8 meters above the Martian surface, and has a resolution of two millimeters at a range of two meters.Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is an operating division of the California Institute of Technology (Caltech). The Imager for Mars Pathfinder (IMP) was developed by the University of Arizona Lunar and Planetary Laboratory under contract to JPL. Peter Smith is the Principal Investigator.Click below to see the left and right views individually. [figure removed for brevity, see original site] Left [figure removed for brevity, see original site] Right
Laser Based 3D Volumetric Display System
1993-03-01
Literature, Costa Mesa, CA July 1983. 3. "A Real Time Autostereoscopic Multiplanar 3D Display System", Rodney Don Williams, Felix Garcia, Jr., Texas...8217 .- NUMBERS LASER BASED 3D VOLUMETRIC DISPLAY SYSTEM PR: CD13 0. AUTHOR(S) PE: N/AWIU: DN303151 P. Soltan, J. Trias, W. Robinson, W. Dahlke 7...laser generated 3D volumetric images on a rotating double helix, (where the 3D displays are computer controlled for group viewing with the naked eye
FOREWORD: Third International Symposium on Instability and Bifurcations in Fluid Dynamics
Bar-Yoseph, P. Z.; Brøns, M.; Cliffe, K. A.; Gelfgat, A.; Oron, A.
2010-01-01
Hydrodynamic stability is of fundamental importance in fluid dynamics and is a well-established subject of scientific investigation that continues to attract great interest of the fluid mechanics community. Bifurcations and instabilities are observed in all areas of fundamental and applied fluid dynamics and remain a challenge for experimental, theoretical and computational studies. Hydrodynamic instabilities of prototypical character are, for example, the Rayleigh-Bénard, the Taylor-Couette, the Bénard-Marangoni, the Rayleigh-Taylor, and the Kelvin-Helmholtz instabilities. A fundamental understanding of various patterns of bifurcations such as identifying the most dominant mechanisms responsible for the instability threshold is also required if one is to design reliable and efficient industrial processes and applications, such as melting, mixing, crystal growth, coating, welding, flow re-attachment over wings, and others. Modeling of various instability mechanisms in biological and biomedical systems is currently a very active and rapidly developing area of research with important biotechnological and medical applications (biofilm engineering, wound healing, etc). The understanding of breaking symmetry in hemodynamics could have important consequences for vascular biology and diseases and its implication for vascular interventions (grafting, stenting, etc). The collection of papers in this volume is a selection of the presentations given at the Third International Symposium on Instability and Bifurcations in Fluid Dynamics, University of Nottingham, UK, 10-13 August 2009. With more than 100 invited and contributed papers the symposium gave an overview of the state-of-the art of the field including experimental, theoretical, and computational approaches to problems related to convection, effects of magnetic fields, wake flows, rotating flows, and many others. The complete program can be found at the conference website. The symposium was the follow-up of two
3D Printing and Its Urologic Applications.
Soliman, Youssef; Feibus, Allison H; Baum, Neil
2015-01-01
3D printing is the development of 3D objects via an additive process in which successive layers of material are applied under computer control. This article discusses 3D printing, with an emphasis on its historical context and its potential use in the field of urology.
Engle, Rob
2008-02-01
This paper discusses the creative and technical challenges encountered during the production of "Beowulf 3D," director Robert Zemeckis' adaptation of the Old English epic poem and the first film to be simultaneously released in IMAX 3D and digital 3D formats.
3D Printing and Its Urologic Applications
Soliman, Youssef; Feibus, Allison H; Baum, Neil
2015-01-01
3D printing is the development of 3D objects via an additive process in which successive layers of material are applied under computer control. This article discusses 3D printing, with an emphasis on its historical context and its potential use in the field of urology. PMID:26028997
Expanding Geometry Understanding with 3D Printing
Cochran, Jill A.; Cochran, Zane; Laney, Kendra; Dean, Mandi
2016-01-01
With the rise of personal desktop 3D printing, a wide spectrum of educational opportunities has become available for educators to leverage this technology in their classrooms. Until recently, the ability to create physical 3D models was well beyond the scope, skill, and budget of many schools. However, since desktop 3D printers have become readily…
Investigating Mobile Stereoscopic 3D Touchscreen Interaction
Colley, Ashley; Hakkila, Jonna; SCHOENING, Johannes; Posti, Maaret
2013-01-01
3D output is no longer limited to large screens in cinemas or living rooms. Nowadays more and more mobile devices are equipped with autostereoscopic 3D (S3D) touchscreens. As a consequence interaction with 3D content now also happens whilst users are on the move. In this paper we carried out a user study with 27 participants to assess how mobile interaction, i.e. whilst walking, with mobile S3D devices, differs from interaction with 2D mobile touchscreens. We investigate the difference in tou...
Wafer level 3-D ICs process technology
Tan, Chuan Seng; Reif, L Rafael
2009-01-01
This book focuses on foundry-based process technology that enables the fabrication of 3-D ICs. The core of the book discusses the technology platform for pre-packaging wafer lever 3-D ICs. However, this book does not include a detailed discussion of 3-D ICs design and 3-D packaging. This is an edited book based on chapters contributed by various experts in the field of wafer-level 3-D ICs process technology. They are from academia, research labs and industry.
View-based 3-D object retrieval
Gao, Yue
2014-01-01
Content-based 3-D object retrieval has attracted extensive attention recently and has applications in a variety of fields, such as, computer-aided design, tele-medicine,mobile multimedia, virtual reality, and entertainment. The development of efficient and effective content-based 3-D object retrieval techniques has enabled the use of fast 3-D reconstruction and model design. Recent technical progress, such as the development of camera technologies, has made it possible to capture the views of 3-D objects. As a result, view-based 3-D object retrieval has become an essential but challenging res
Web-based interactive visualization of 3D video mosaics using X3D standard
CHON Jaechoon; LEE Yang-Won; SHIBASAKI Ryosuke
2006-01-01
We present a method of 3D image mosaicing for real 3D representation of roadside buildings, and implement a Web-based interactive visualization environment for the 3D video mosaics created by 3D image mosaicing. The 3D image mosaicing technique developed in our previous work is a very powerful method for creating textured 3D-GIS data without excessive data processing like the laser or stereo system. For the Web-based open access to the 3D video mosaics, we build an interactive visualization environment using X3D, the emerging standard of Web 3D. We conduct the data preprocessing for 3D video mosaics and the X3D modeling for textured 3D data. The data preprocessing includes the conversion of each frame of 3D video mosaics into concatenated image files that can be hyperlinked on the Web. The X3D modeling handles the representation of concatenated images using necessary X3D nodes. By employing X3D as the data format for 3D image mosaics, the real 3D representation of roadside buildings is extended to the Web and mobile service systems.
Case study: Beauty and the Beast 3D: benefits of 3D viewing for 2D to 3D conversion
Handy Turner, Tara
2010-02-01
From the earliest stages of the Beauty and the Beast 3D conversion project, the advantages of accurate desk-side 3D viewing was evident. While designing and testing the 2D to 3D conversion process, the engineering team at Walt Disney Animation Studios proposed a 3D viewing configuration that not only allowed artists to "compose" stereoscopic 3D but also improved efficiency by allowing artists to instantly detect which image features were essential to the stereoscopic appeal of a shot and which features had minimal or even negative impact. At a time when few commercial 3D monitors were available and few software packages provided 3D desk-side output, the team designed their own prototype devices and collaborated with vendors to create a "3D composing" workstation. This paper outlines the display technologies explored, final choices made for Beauty and the Beast 3D, wish-lists for future development and a few rules of thumb for composing compelling 2D to 3D conversions.
Intersecting D 3 -D3 ' -brane system at finite temperature
Cottrell, William; Hanson, James; Hashimoto, Akikazu; Loveridge, Andrew; Pettengill, Duncan
2017-02-01
We analyze the dynamics of the intersecting D 3 -D3 ' -brane system overlapping in 1 +1 dimensions, in a holographic treatment where N D3 branes are manifested as anti-de Sitter Schwartzschild geometry, and the D3 ' brane is treated as a probe. We extract the thermodynamic equation of state from the set of embedding solutions, and analyze the stability at the perturbative and the nonperturbative level. We review a systematic procedure to resolve local instabilities and multivaluedness in the equations of state based on classic ideas of convexity in the microcanonical ensemble. We then identify a runaway behavior which was not noticed previously for this system.
3D laptop for defense applications
Edmondson, Richard; Chenault, David
2012-06-01
Polaris Sensor Technologies has developed numerous 3D display systems using a US Army patented approach. These displays have been developed as prototypes for handheld controllers for robotic systems and closed hatch driving, and as part of a TALON robot upgrade for 3D vision, providing depth perception for the operator for improved manipulation and hazard avoidance. In this paper we discuss the prototype rugged 3D laptop computer and its applications to defense missions. The prototype 3D laptop combines full temporal and spatial resolution display with the rugged Amrel laptop computer. The display is viewed through protective passive polarized eyewear, and allows combined 2D and 3D content. Uses include robot tele-operation with live 3D video or synthetically rendered scenery, mission planning and rehearsal, enhanced 3D data interpretation, and simulation.
User-centered 3D geovisualisation
Nielsen, Anette Hougaard
2004-01-01
3D Geovisualisation is a multidisciplinary science mainly utilizing geographically related data, developing software systems for 3D visualisation and producing relevant models. In this paper the connection between geoinformation stored as 3D objects and the end user is of special interest....... In a broader perspective, the overall aim is to develop a language in 3D Geovisualisation gained through usability projects and the development of a theoretical background. A conceptual level of user-centered 3D Geovisualisation is introduced by applying a categorisation originating from Virtual Reality....... The conceptual level is used to structure and organise user-centered 3D Geovisualisation into four categories: representation, rendering, interface and interaction. The categories reflect a process of development of 3D Geovisualisation where objects can be represented verisimilar to the real world...
FROM 3D MODEL DATA TO SEMANTICS
My Abdellah Kassimi
2012-01-01
Full Text Available The semantic-based 3D models retrieval systems have become necessary since the increase of 3D modelsdatabases. In this paper, we propose a new method for the mapping problem between 3D model data andsemantic data involved in semantic based retrieval for 3D models given by polygonal meshes. First, wefocused on extracting invariant descriptors from the 3D models and analyzing them to efficient semanticannotation and to improve the retrieval accuracy. Selected shape descriptors provide a set of termscommonly used to describe visually a set of objects using linguistic terms and are used as semanticconcept to label 3D model. Second, spatial relationship representing directional, topological anddistance relationships are used to derive other high-level semantic features and to avoid the problem ofautomatic 3D model annotation. Based on the resulting semantic annotation and spatial concepts, anontology for 3D model retrieval is constructed and other concepts can be inferred. This ontology is usedto find similar 3D models for a given query model. We adopted the query by semantic example approach,in which the annotation is performed mostly automatically. The proposed method is implemented in our3D search engine (SB3DMR, tested using the Princeton Shape Benchmark Database.
3D change detection - Approaches and applications
Qin, Rongjun; Tian, Jiaojiao; Reinartz, Peter
2016-12-01
Due to the unprecedented technology development of sensors, platforms and algorithms for 3D data acquisition and generation, 3D spaceborne, airborne and close-range data, in the form of image based, Light Detection and Ranging (LiDAR) based point clouds, Digital Elevation Models (DEM) and 3D city models, become more accessible than ever before. Change detection (CD) or time-series data analysis in 3D has gained great attention due to its capability of providing volumetric dynamics to facilitate more applications and provide more accurate results. The state-of-the-art CD reviews aim to provide a comprehensive synthesis and to simplify the taxonomy of the traditional remote sensing CD techniques, which mainly sit within the boundary of 2D image/spectrum analysis, largely ignoring the particularities of 3D aspects of the data. The inclusion of 3D data for change detection (termed 3D CD), not only provides a source with different modality for analysis, but also transcends the border of traditional top-view 2D pixel/object-based analysis to highly detailed, oblique view or voxel-based geometric analysis. This paper reviews the recent developments and applications of 3D CD using remote sensing and close-range data, in support of both academia and industry researchers who seek for solutions in detecting and analyzing 3D dynamics of various objects of interest. We first describe the general considerations of 3D CD problems in different processing stages and identify CD types based on the information used, being the geometric comparison and geometric-spectral analysis. We then summarize relevant works and practices in urban, environment, ecology and civil applications, etc. Given the broad spectrum of applications and different types of 3D data, we discuss important issues in 3D CD methods. Finally, we present concluding remarks in algorithmic aspects of 3D CD.
Budroni, M. A.
2015-12-01
Cross diffusion, whereby a flux of a given species entrains the diffusive transport of another species, can trigger buoyancy-driven hydrodynamic instabilities at the interface of initially stable stratifications. Starting from a simple three-component case, we introduce a theoretical framework to classify cross-diffusion-induced hydrodynamic phenomena in two-layer stratifications under the action of the gravitational field. A cross-diffusion-convection (CDC) model is derived by coupling the fickian diffusion formalism to Stokes equations. In order to isolate the effect of cross-diffusion in the convective destabilization of a double-layer system, we impose a starting concentration jump of one species in the bottom layer while the other one is homogeneously distributed over the spatial domain. This initial configuration avoids the concurrence of classic Rayleigh-Taylor or differential-diffusion convective instabilities, and it also allows us to activate selectively the cross-diffusion feedback by which the heterogeneously distributed species influences the diffusive transport of the other species. We identify two types of hydrodynamic modes [the negative cross-diffusion-driven convection (NCC) and the positive cross-diffusion-driven convection (PCC)], corresponding to the sign of this operational cross-diffusion term. By studying the space-time density profiles along the gravitational axis we obtain analytical conditions for the onset of convection in terms of two important parameters only: the operational cross-diffusivity and the buoyancy ratio, giving the relative contribution of the two species to the global density. The general classification of the NCC and PCC scenarios in such parameter space is supported by numerical simulations of the fully nonlinear CDC problem. The resulting convective patterns compare favorably with recent experimental results found in microemulsion systems.
Development of 3D beam-beam simulation for the Tevatron
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.
3D Systems” ‘Stuck in the Middle’ of the 3D Printer Boom?
A. Hoffmann (Alan)
2014-01-01
textabstract3D Systems, the pioneer of 3D printing, predicted a future where "kids from 8 to 80" could design and print their ideas at home. By 2013, 9 years after the creation of the first working 3D printer, there were more than 30 major 3D printing companies competing for market share. 3DS and it
Arvekari, Lassi
2013-01-01
Opinnäytetyön tavoitteena on selvittää 3D-tulostustekniikan perusteita ja 3D-tulostuksen nykytilannetta. 3D-tulostukseen sopivien mallien luomista tutkitaan ja mallin tekemiseen on etsitty toimivia ohjesääntöjä. Tärkeä osa työtä on tutkia mitä vaiheita 3D-tulostimen hankinnassa kotikäyttöön tulee vastaan. Käytännön kokeita varten opinnäytetyössä on case Printrbot, jossa on tutustuttu edulliseen 3D-tulostuslaitteeseen kokoonpanosta lähtien. Työn kuluessa selvisi että edulliset 3D-tulos...
Stability Criteria of 3D Inviscid Shears
Li, Y Charles
2009-01-01
The classical plane Couette flow, plane Poiseuille flow, and pipe Poiseuille flow share some universal 3D steady coherent structure in the form of "streak-roll-critical layer". As the Reynolds number approaches infinity, the steady coherent structure approaches a 3D limiting shear of the form ($U(y,z), 0, 0$) in velocity variables. All such 3D shears are steady states of the 3D Euler equations. This raises the importance of investigating the stability of such inviscid 3D shears in contrast to the classical Rayleigh theory of inviscid 2D shears. Several general criteria of stability for such inviscid 3D shears are derived. In the Appendix, an argument is given to show that a 2D limiting shear can only be the classical laminar shear.
Ultrasonic Sensor Based 3D Mapping & Localization
Shadman Fahim Ahmad
2016-04-01
Full Text Available This article provides a basic level introduction to 3D mapping using sonar sensors and localization. It describes the methods used to construct a low-cost autonomous robot along with the hardware and software used as well as an insight to the background of autonomous robotic 3D mapping and localization. We have also given an overview to what the future prospects of the robot may hold in 3D based mapping.
ERP system for 3D printing industry
Deaky Bogdan
2017-01-01
Full Text Available GOCREATE is an original cloud-based production management and optimization service which helps 3D printing service providers to use their resources better. The proposed Enterprise Resource Planning system can significantly increase income through improved productivity. With GOCREATE, the 3D printing service providers get a much higher production efficiency at a much lower licensing cost, to increase their competitiveness in the fast growing 3D printing market.
Reconhecimento de faces 3D com Kinect
Cardia Neto, João Baptista [UNESP
2014-01-01
For person identification, facil recognition has several advantages over other biometric traits due mostly to its high universelly, collectability, and acceptability. When dealing with 2D face images several problems arise related to pose, illumination, and facial expressions. To increase the performance of facial recognition, 3D mehtods have been proposed and developedm since working with 3D objects allow us to handle better the aforementioned problems. With 3D object, it is possible to rota...
Topology Dictionary for 3D Video Understanding
2012-01-01
This paper presents a novel approach that achieves 3D video understanding. 3D video consists of a stream of 3D models of subjects in motion. The acquisition of long sequences requires large storage space (2 GB for 1 min). Moreover, it is tedious to browse data sets and extract meaningful information. We propose the topology dictionary to encode and describe 3D video content. The model consists of a topology-based shape descriptor dictionary which can be generated from either extracted pattern...
Illustrating Mathematics using 3D Printers
Knill, Oliver; Slavkovsky, Elizabeth
2013-01-01
3D printing technology can help to visualize proofs in mathematics. In this document we aim to illustrate how 3D printing can help to visualize concepts and mathematical proofs. As already known to educators in ancient Greece, models allow to bring mathematics closer to the public. The new 3D printing technology makes the realization of such tools more accessible than ever. This is an updated version of a paper included in book Low-Cost 3D Printing for science, education and Sustainable Devel...
Calibration for 3D Structured Light Measurement
无
2007-01-01
A calibration procedure was developed for three-dimensional(3D) binocular structured light measurement systems. In virtue of a specially designed pattern, matching points in stereo images are extracted. And then sufficient 3D space points are obtained through pairs of images with the intrinsic and extrinsic parameters of each camera estimated prior and consequently some lights are calibrated by means of multi point fitting. Finally, a mathematical model is applied to interpolate and approximate all dynamic scanning lights based on geometry. The process of calibration method is successfully used in the binocular 3D measurement system based on structured lights and the 3D reconstruction results are satisfying.
Getting started in 3D with Maya
Watkins, Adam
2012-01-01
Deliver professional-level 3D content in no time with this comprehensive guide to 3D animation with Maya. With over 12 years of training experience, plus several award winning students under his belt, author Adam Watkins is the ideal mentor to get you up to speed with 3D in Maya. Using a structured and pragmatic approach Getting Started in 3D with Maya begins with basic theory of fundamental techniques, then builds on this knowledge using practical examples and projects to put your new skills to the test. Prepared so that you can learn in an organic fashion, each chapter builds on the know
Virtual Realization using 3D Password
A.B.Gadicha
2012-03-01
Full Text Available Current authentication systems suffer from many weaknesses. Textual passwords are commonly used; however, users do not follow their requirements. Users tend to choose meaningful words from dictionaries, which make textual passwords easy to break and vulnerable to dictionary or brute force attacks. Many available graphical passwords have a password space that is less than or equal to the textual password space. Smart cards or tokens can be stolen. Many biometric authentications have been proposed; however, users tend to resist using biometrics because of their intrusiveness and the effect on their privacy. Moreover, biometrics cannot be revoked. In this paper, we present and evaluate our contribution, i.e., the 3D password. The 3D password is a multifactor authentication scheme. To be authenticated, we present a 3D virtual environment where the user navigates and interacts with various objects. The sequence of actions and interactions toward the objects inside the 3D environment constructs the user’s 3D password. The 3D password can combine most existing authentication schemes such as textual passwords, graphical passwords, and various types of biometrics into a 3D virtual environment. The design of the 3D virtual environment and the type of objects selected determine the 3D password key space.
Ekologinen 3D-tulostettava asuste
Paulasaari, Laura
2014-01-01
Tämän opinnäytetyön aiheena oli ekologisuus 3D-tulostuksessa ja sen hyödynnettävyys erityisesti asustesuunnittelussa. Työn tarkoituksena oli selvittää, kuinka 3D-tulostusta voi tehdä ekologisemmin ja mitä vaihtoehtoja kuluttajalle tällä hetkellä on. Työ tehtiin Young skills –osuuskunnalle. 3D-tulostuksella on mahdollisuus antaa todella paljon tulevaisuuden tuotantomenetelmille ja se vapauttaa tuotteiden muotoilua täysin uudella tavalla. 3D-tulostuksen avulla voidaan keskittyä enemmän esim...
HIGH-MODE RAYLEIGH-TAYLOR GROWTH IN NIF IGNITION CAPSULES
Hammel, B A; Haan, S W; Clark, D; Edwards, M J; Langer, S H; Marinak, M; Patel, M; Salmonson, J; Scott, H A
2009-08-04
An assessment of short wavelength hydrodynamic stability is an essential component in the optimization of NIF ignition target designs. Using highly-resolved massively-parallel 2-D Hydra simulations, we routinely evaluate target designs up to mode numbers of 2000 ({lambda} {approx} 2 {micro}m). On the outer ablator surface, mode numbers up to {approx}300 ({lambda} {approx} 20 {micro}m) can have significant growth in CH capsule designs. At the internal fuel:ablator interface mode numbers up to {approx}2000 are important for both CH and Be designs. In addition, 'isolated features' on the capsule, such as the 'fill-tube' ({approx} 5 {micro}m scale-length) and defects, can seed short wavelength growth at the ablation front and the fuel:ablator interface, leading to the injection of {approx} 10's ng of ablator material into the central hot-spot. We are developing methods to measure high-mode mix on NIF implosion experiments. X-ray spectroscopic methods are appealing since mix into the hot-spot will result in x-ray emission from the high-Z dopant (Cu or Ge) in the ablator material (Be or CH).
Supernova hydrodynamics experiments using the Nova laser
Remington, B.A.; Glendinning, S.G.; Estabrook, K.; Wallace, R.J.; Rubenchik, A. [Lawrence Livermore National Lab., CA (United States); Kane, J.; Arnett, D. [Arizona Univ., Tucson, AZ (United States). Stewart Observatory; Drake, R.P. [Michigan Univ., Ann Arbor, MI (United States); McCray, R. [Colorado Univ., Boulder, CO (United States)
1997-04-01
We are developing experiments using the Nova laser to investigate two areas of physics relevant to core-collapse supernovae (SN): (1) compressible nonlinear hydrodynamic mixing and (2) radiative shock hydrodynamics. In the former, we are examining the differences between the 2D and 3D evolution of the Rayleigh-Taylor instability, an issue critical to the observables emerging from SN in the first year after exploding. In the latter, we are investigating the evolution of a colliding plasma system relevant to the ejecta-stellar wind interactions of the early stages of SN remnant formation. The experiments and astrophysical implications are discussed.
An aerial 3D printing test mission
Hirsch, Michael; McGuire, Thomas; Parsons, Michael; Leake, Skye; Straub, Jeremy
2016-05-01
This paper provides an overview of an aerial 3D printing technology, its development and its testing. This technology is potentially useful in its own right. In addition, this work advances the development of a related in-space 3D printing technology. A series of aerial 3D printing test missions, used to test the aerial printing technology, are discussed. Through completing these test missions, the design for an in-space 3D printer may be advanced. The current design for the in-space 3D printer involves focusing thermal energy to heat an extrusion head and allow for the extrusion of molten print material. Plastics can be used as well as composites including metal, allowing for the extrusion of conductive material. A variety of experiments will be used to test this initial 3D printer design. High altitude balloons will be used to test the effects of microgravity on 3D printing, as well as parabolic flight tests. Zero pressure balloons can be used to test the effect of long 3D printing missions subjected to low temperatures. Vacuum chambers will be used to test 3D printing in a vacuum environment. The results will be used to adapt a current prototype of an in-space 3D printer. Then, a small scale prototype can be sent into low-Earth orbit as a 3-U cube satellite. With the ability to 3D print in space demonstrated, future missions can launch production hardware through which the sustainability and durability of structures in space will be greatly improved.
Rasmussen, Henrik Koblitz
2000-01-01
The 3D-LIM has as yet been used to simulate the following two three-dimensional problems. First, the method has been used to simulete for viscoelastic end-plate instability that occurs under certain conditions in the transient filament stretching apparatus for pressure sensitive adhesives...... (polymeric melts) and polymeric solutions. Secondly, the 3D-LIM has also been applied to calculate the inflation of a thick sheet of a polymer melt into an elliptic cylinder. These problems all include free surfaces. As the governing equations are solved for the particle positions, the motion of surfaces can...... be followed easily even in 3D viscoelastic flow....
Integration of real-time 3D image acquisition and multiview 3D display
Zhang, Zhaoxing; Geng, Zheng; Li, Tuotuo; Li, Wei; Wang, Jingyi; Liu, Yongchun
2014-03-01
Seamless integration of 3D acquisition and 3D display systems offers enhanced experience in 3D visualization of the real world objects or scenes. The vivid representation of captured 3D objects displayed on a glasses-free 3D display screen could bring the realistic viewing experience to viewers as if they are viewing real-world scene. Although the technologies in 3D acquisition and 3D display have advanced rapidly in recent years, effort is lacking in studying the seamless integration of these two different aspects of 3D technologies. In this paper, we describe our recent progress on integrating a light-field 3D acquisition system and an autostereoscopic multiview 3D display for real-time light field capture and display. This paper focuses on both the architecture design and the implementation of the hardware and the software of this integrated 3D system. A prototype of the integrated 3D system is built to demonstrate the real-time 3D acquisition and 3D display capability of our proposed system.
3D Printed Block Copolymer Nanostructures
Scalfani, Vincent F.; Turner, C. Heath; Rupar, Paul A.; Jenkins, Alexander H.; Bara, Jason E.
2015-01-01
The emergence of 3D printing has dramatically advanced the availability of tangible molecular and extended solid models. Interestingly, there are few nanostructure models available both commercially and through other do-it-yourself approaches such as 3D printing. This is unfortunate given the importance of nanotechnology in science today. In this…
Parametrizable cameras for 3D computational steering
Mulder, J.D.; Wijk, J.J. van
1997-01-01
We present a method for the definition of multiple views in 3D interfaces for computational steering. The method uses the concept of a point-based parametrizable camera object. This concept enables a user to create and configure multiple views on his custom 3D interface in an intuitive graphical man
3D elastic control for mobile devices.
Hachet, Martin; Pouderoux, Joachim; Guitton, Pascal
2008-01-01
To increase the input space of mobile devices, the authors developed a proof-of-concept 3D elastic controller that easily adapts to mobile devices. This embedded device improves the completion of high-level interaction tasks such as visualization of large documents and navigation in 3D environments. It also opens new directions for tomorrow's mobile applications.
3D printing of functional structures
Krijnen, G.J.M.
2016-01-01
The technology colloquial known as ‘3D printing’ has developed in such diversity in printing technologies and application fields that meanwhile it seems anything is possible. However, clearly the ideal 3D Printer, with high resolution, multi-material capability, fast printing, etc. is yet to be deve
Norbury, Keith
2012-01-01
It may be too soon for students to be showing up for class with popcorn and gummy bears, but technology similar to that behind the 3D blockbuster movie "Avatar" is slowly finding its way into college classrooms. 3D classroom projectors are taking students on fantastic voyages inside the human body, to the ruins of ancient Greece--even to faraway…
Holmgren, Steen; Rüdiger, Bjarne; Tournay, Bruno
2001-01-01
We have worked with the construction and use of 3D city models for about ten years. This work has given us valuable experience concerning model methodology. In addition to this collection of knowledge, our perception of the concept of city models has changed radically. In order to explain...... of 3D city models....
3D Printing of Molecular Models
Gardner, Adam; Olson, Arthur
2016-01-01
Physical molecular models have played a valuable role in our understanding of the invisible nano-scale world. We discuss 3D printing and its use in producing models of the molecules of life. Complex biomolecular models, produced from 3D printed parts, can demonstrate characteristics of molecular structure and function, such as viral self-assembly,…
Love, Tyler S.; Roy, Ken
2016-01-01
Health concerns from 3D printing were first documented by Stephens, Azimi, Orch, and Ramos (2013), who found that commercially available 3D printers were producing hazardous levels of ultrafine particles (UFPs) and volatile organic compounds (VOCs) when plastic materials were melted through the extruder. UFPs are particles less than 100 nanometers…
Topology dictionary for 3D video understanding.
Tung, Tony; Matsuyama, Takashi
2012-08-01
This paper presents a novel approach that achieves 3D video understanding. 3D video consists of a stream of 3D models of subjects in motion. The acquisition of long sequences requires large storage space (2 GB for 1 min). Moreover, it is tedious to browse data sets and extract meaningful information. We propose the topology dictionary to encode and describe 3D video content. The model consists of a topology-based shape descriptor dictionary which can be generated from either extracted patterns or training sequences. The model relies on 1) topology description and classification using Reeb graphs, and 2) a Markov motion graph to represent topology change states. We show that the use of Reeb graphs as the high-level topology descriptor is relevant. It allows the dictionary to automatically model complex sequences, whereas other strategies would require prior knowledge on the shape and topology of the captured subjects. Our approach serves to encode 3D video sequences, and can be applied for content-based description and summarization of 3D video sequences. Furthermore, topology class labeling during a learning process enables the system to perform content-based event recognition. Experiments were carried out on various 3D videos. We showcase an application for 3D video progressive summarization using the topology dictionary.
3D background aerodynamics using CFD
Sørensen, Niels N.
2002-01-01
3D rotor computations for the Greek Geovilogiki (GEO) 44 meter rotor equipped with 19 meters blades are performed. The lift and drag polars are extracted at five spanvise locations r/R= (.37, .55, .71, .82, .93) based on identification of stagnationpoints between 2D and 3D computations. The inner...
Limited Feedback for 3D Massive MIMO under 3D-UMa and 3D-UMi Scenarios
Zheng Hu
2015-01-01
Full Text Available For three-dimensional (3D massive MIMO utilizing the uniform rectangular array (URA in the base station (BS, we propose a limited feedback transmission scheme in which the channel state information (CSI feedback operations for horizontal domain and vertical domain are separate. Compared to the traditional feedback scheme, the scheme can reduce the feedback overhead, code word index search complexity, and storage requirement. Also, based on the zenith of departure angle (ZoD distribution in 3D-Urban Macro Cell (3D-UMa and 3D-Urban Micro Cell (3D-UMi scenarios, we propose the angle quantization codebook for vertical domain, while the codebook of long term evolution-advanced (LTE-Advanced is still adopted in horizontal domain to preserve compatibility with the LTE-Advanced. Based on the angle quantization codebook, the subsampled 3-bit DFT codebook is designed for vertical domain. The system-level simulation results reveal that, to compromise the feedback overhead and system performance, 2-bit codebook for 3D-UMa scenario and 3-bit codebook for 3D-UMi scenario can meet requirements in vertical domain. The feedback period for vertical domain can also be extended appropriately to reduce the feedback overhead.
Fabrication of 3D Silicon Sensors
Kok, A.; Hansen, T.E.; Hansen, T.A.; Lietaer, N.; Summanwar, A.; /SINTEF, Oslo; Kenney, C.; Hasi, J.; /SLAC; Da Via, C.; /Manchester U.; Parker, S.I.; /Hawaii U.
2012-06-06
Silicon sensors with a three-dimensional (3-D) architecture, in which the n and p electrodes penetrate through the entire substrate, have many advantages over planar silicon sensors including radiation hardness, fast time response, active edge and dual readout capabilities. The fabrication of 3D sensors is however rather complex. In recent years, there have been worldwide activities on 3D fabrication. SINTEF in collaboration with Stanford Nanofabrication Facility have successfully fabricated the original (single sided double column type) 3D detectors in two prototype runs and the third run is now on-going. This paper reports the status of this fabrication work and the resulted yield. The work of other groups such as the development of double sided 3D detectors is also briefly reported.
Maintaining and troubleshooting your 3D printer
Bell, Charles
2014-01-01
Maintaining and Troubleshooting Your 3D Printer by Charles Bell is your guide to keeping your 3D printer running through preventive maintenance, repair, and diagnosing and solving problems in 3D printing. If you've bought or built a 3D printer such as a MakerBot only to be confounded by jagged edges, corner lift, top layers that aren't solid, or any of a myriad of other problems that plague 3D printer enthusiasts, then here is the book to help you get past all that and recapture the joy of creative fabrication. The book also includes valuable tips for builders and those who want to modify the
Dekker, T.; de Zwart, S. T.; Willemsen, O. H.; Hiddink, M. G. H.; IJzerman, W. L.
2006-02-01
A prerequisite for a wide market acceptance of 3D displays is the ability to switch between 3D and full resolution 2D. In this paper we present a robust and cost effective concept for an auto-stereoscopic switchable 2D/3D display. The display is based on an LCD panel, equipped with switchable LC-filled lenticular lenses. We will discuss 3D image quality, with the focus on display uniformity. We show that slanting the lenticulars in combination with a good lens design can minimize non-uniformities in our 20" 2D/3D monitors. Furthermore, we introduce fractional viewing systems as a very robust concept to further improve uniformity in the case slanting the lenticulars and optimizing the lens design are not sufficient. We will discuss measurements and numerical simulations of the key optical characteristics of this display. Finally, we discuss 2D image quality, the switching characteristics and the residual lens effect.
6D Interpretation of 3D Gravity
Herfray, Yannick; Krasnov, Kirill; Scarinci, Carlos
2017-02-01
We show that 3D gravity, in its pure connection formulation, admits a natural 6D interpretation. The 3D field equations for the connection are equivalent to 6D Hitchin equations for the Chern–Simons 3-form in the total space of the principal bundle over the 3-dimensional base. Turning this construction around one gets an explanation of why the pure connection formulation of 3D gravity exists. More generally, we interpret 3D gravity as the dimensional reduction of the 6D Hitchin theory. To this end, we show that any \\text{SU}(2) invariant closed 3-form in the total space of the principal \\text{SU}(2) bundle can be parametrised by a connection together with a 2-form field on the base. The dimensional reduction of the 6D Hitchin theory then gives rise to 3D gravity coupled to a topological 2-form field.
3D Visualization Development of SIUE Campus
Nellutla, Shravya
Geographic Information Systems (GIS) has progressed from the traditional map-making to the modern technology where the information can be created, edited, managed and analyzed. Like any other models, maps are simplified representations of real world. Hence visualization plays an essential role in the applications of GIS. The use of sophisticated visualization tools and methods, especially three dimensional (3D) modeling, has been rising considerably due to the advancement of technology. There are currently many off-the-shelf technologies available in the market to build 3D GIS models. One of the objectives of this research was to examine the available ArcGIS and its extensions for 3D modeling and visualization and use them to depict a real world scenario. Furthermore, with the advent of the web, a platform for accessing and sharing spatial information on the Internet, it is possible to generate interactive online maps. Integrating Internet capacity with GIS functionality redefines the process of sharing and processing the spatial information. Enabling a 3D map online requires off-the-shelf GIS software, 3D model builders, web server, web applications and client server technologies. Such environments are either complicated or expensive because of the amount of hardware and software involved. Therefore, the second objective of this research was to investigate and develop simpler yet cost-effective 3D modeling approach that uses available ArcGIS suite products and the free 3D computer graphics software for designing 3D world scenes. Both ArcGIS Explorer and ArcGIS Online will be used to demonstrate the way of sharing and distributing 3D geographic information on the Internet. A case study of the development of 3D campus for the Southern Illinois University Edwardsville is demonstrated.
The psychology of the 3D experience
Janicke, Sophie H.; Ellis, Andrew
2013-03-01
With 3D televisions expected to reach 50% home saturation as early as 2016, understanding the psychological mechanisms underlying the user response to 3D technology is critical for content providers, educators and academics. Unfortunately, research examining the effects of 3D technology has not kept pace with the technology's rapid adoption, resulting in large-scale use of a technology about which very little is actually known. Recognizing this need for new research, we conducted a series of studies measuring and comparing many of the variables and processes underlying both 2D and 3D media experiences. In our first study, we found narratives within primetime dramas had the power to shift viewer attitudes in both 2D and 3D settings. However, we found no difference in persuasive power between 2D and 3D content. We contend this lack of effect was the result of poor conversion quality and the unique demands of 3D production. In our second study, we found 3D technology significantly increased enjoyment when viewing sports content, yet offered no added enjoyment when viewing a movie trailer. The enhanced enjoyment of the sports content was shown to be the result of heightened emotional arousal and attention in the 3D condition. We believe the lack of effect found for the movie trailer may be genre-related. In our final study, we found 3D technology significantly enhanced enjoyment of two video games from different genres. The added enjoyment was found to be the result of an increased sense of presence.
Seeing a Stellar Explosion in 3D
2010-08-01
faster in some directions than others, leading to an irregular shape with some parts stretching out further into space. The first material to be ejected from the explosion travelled at an incredible 100 million km per hour, which is about a tenth of the speed of light or around 100 000 times faster than a passenger jet. Even at this breakneck speed it has taken 10 years to reach a previously existing ring of gas and dust puffed out from the dying star. The images also demonstrate that another wave of material is travelling ten times more slowly and is being heated by radioactive elements created in the explosion. "We have established the velocity distribution of the inner ejecta of Supernova 1987A," says lead author Karina Kjær. "Just how a supernova explodes is not very well understood, but the way the star exploded is imprinted on this inner material. We can see that this material was not ejected symmetrically in all directions, but rather seems to have had a preferred direction. Besides, this direction is different to what was expected from the position of the ring." Such asymmetric behaviour was predicted by some of the most recent computer models of supernovae, which found that large-scale instabilities take place during the explosion. The new observations are thus the first direct confirmation of such models. SINFONI is the leading instrument of its kind, and only the level of detail it affords allowed the team to draw their conclusions. Advanced adaptive optics systems counteracted the blurring effects of the Earth's atmosphere while a technique called integral field spectroscopy allowed the astronomers to study several parts of the supernova's chaotic core simultaneously, leading to the build-up of the 3D image. "Integral field spectroscopy is a special technique where for each pixel we get information about the nature and velocity of the gas," says Kjær. "This means that besides the normal picture we also have the velocity along the line of sight. Because we
Gorgon simulations of Magnetized Liner Inertial Fusion
Roeltgen, Jonathan; Jennings, Christopher; Sefkow, Adam; Slutz, Stephen
2012-10-01
Substantial fusion yields are predicted with pulsed power machines driving cylindrical liner implosions with preheated and magnetized deuterium-tritium [S.A. Slutz et al Phys. Plasmas 17, 056303 (2010)]. The Rayleigh-Taylor instability is the most likely mechanism that could degrade the fusion yield of this concept which we call Magnetized Liner Inertial Fusion (MagLIF). Gorgon is a 3D magnetohydrodynamics code that is well suited to simulating the effects of 3D Magneto-Rayleigh-Taylor instabilities. It has successfully simulated wire array z-pinches in 3D. We plan to use Gorgon to simulate the MagLIF concept in 3D, but first we are performing 1D simulations to test the essential physics necessary to simulate the MagLIF concept, for example bremsstrahlung losses from the fuel and the inhibition of transport by the magnetic field. We will present 1D Gorgon results of optimized MagLIF yields as a function of drive current.
3D imaging in forensic odontology.
Evans, Sam; Jones, Carl; Plassmann, Peter
2010-06-16
This paper describes the investigation of a new 3D capture method for acquiring and subsequent forensic analysis of bite mark injuries on human skin. When documenting bite marks with standard 2D cameras errors in photographic technique can occur if best practice is not followed. Subsequent forensic analysis of the mark is problematic when a 3D structure is recorded into a 2D space. Although strict guidelines (BAFO) exist, these are time-consuming to follow and, due to their complexity, may produce errors. A 3D image capture and processing system might avoid the problems resulting from the 2D reduction process, simplifying the guidelines and reducing errors. Proposed Solution: a series of experiments are described in this paper to demonstrate that the potential of a 3D system might produce suitable results. The experiments tested precision and accuracy of the traditional 2D and 3D methods. A 3D image capture device minimises the amount of angular distortion, therefore such a system has the potential to create more robust forensic evidence for use in courts. A first set of experiments tested and demonstrated which method of forensic analysis creates the least amount of intra-operator error. A second set tested and demonstrated which method of image capture creates the least amount of inter-operator error and visual distortion. In a third set the effects of angular distortion on 2D and 3D methods of image capture were evaluated.
Medical 3D Printing for the Radiologist.
Mitsouras, Dimitris; Liacouras, Peter; Imanzadeh, Amir; Giannopoulos, Andreas A; Cai, Tianrun; Kumamaru, Kanako K; George, Elizabeth; Wake, Nicole; Caterson, Edward J; Pomahac, Bohdan; Ho, Vincent B; Grant, Gerald T; Rybicki, Frank J
2015-01-01
While use of advanced visualization in radiology is instrumental in diagnosis and communication with referring clinicians, there is an unmet need to render Digital Imaging and Communications in Medicine (DICOM) images as three-dimensional (3D) printed models capable of providing both tactile feedback and tangible depth information about anatomic and pathologic states. Three-dimensional printed models, already entrenched in the nonmedical sciences, are rapidly being embraced in medicine as well as in the lay community. Incorporating 3D printing from images generated and interpreted by radiologists presents particular challenges, including training, materials and equipment, and guidelines. The overall costs of a 3D printing laboratory must be balanced by the clinical benefits. It is expected that the number of 3D-printed models generated from DICOM images for planning interventions and fabricating implants will grow exponentially. Radiologists should at a minimum be familiar with 3D printing as it relates to their field, including types of 3D printing technologies and materials used to create 3D-printed anatomic models, published applications of models to date, and clinical benefits in radiology. Online supplemental material is available for this article.
Digital relief generation from 3D models
Wang, Meili; Sun, Yu; Zhang, Hongming; Qian, Kun; Chang, Jian; He, Dongjian
2016-09-01
It is difficult to extend image-based relief generation to high-relief generation, as the images contain insufficient height information. To generate reliefs from three-dimensional (3D) models, it is necessary to extract the height fields from the model, but this can only generate bas-reliefs. To overcome this problem, an efficient method is proposed to generate bas-reliefs and high-reliefs directly from 3D meshes. To produce relief features that are visually appropriate, the 3D meshes are first scaled. 3D unsharp masking is used to enhance the visual features in the 3D mesh, and average smoothing and Laplacian smoothing are implemented to achieve better smoothing results. A nonlinear variable scaling scheme is then employed to generate the final bas-reliefs and high-reliefs. Using the proposed method, relief models can be generated from arbitrary viewing positions with different gestures and combinations of multiple 3D models. The generated relief models can be printed by 3D printers. The proposed method provides a means of generating both high-reliefs and bas-reliefs in an efficient and effective way under the appropriate scaling factors.
3D Reconstruction Technique for Tomographic PIV
姜楠; 包全; 杨绍琼
2015-01-01
Tomographic particle image velocimetry(Tomo-PIV) is a state-of-the-art experimental technique based on a method of optical tomography to achieve the three-dimensional(3D) reconstruction for three-dimensional three-component(3D-3C) flow velocity measurements. 3D reconstruction for Tomo-PIV is carried out herein. Meanwhile, a 3D simplified tomographic reconstruction model reduced from a 3D volume light inten-sity field with 2D projection images into a 2D Tomo-slice plane with 1D projecting lines, i.e., simplifying this 3D reconstruction into a problem of 2D Tomo-slice plane reconstruction, is applied thereafter. Two kinds of the most well-known algebraic reconstruction techniques, algebraic reconstruction technique(ART) and multiple algebraic reconstruction technique(MART), are compared as well. The principles of the two reconstruction algorithms are discussed in detail, which has been performed by a series of simulation images, yielding the corresponding recon-struction images that show different features between the ART and MART algorithm, and then their advantages and disadvantages are discussed. Further discussions are made for the standard particle image reconstruction when the background noise of the pre-initial particle image has been removed. Results show that the particle image recon-struction has been greatly improved. The MART algorithm is much better than the ART. Furthermore, the computa-tional analyses of two parameters(the particle density and the number of cameras), are performed to study their effects on the reconstruction. Lastly, the 3D volume particle field is reconstructed by using the improved algorithm based on the simplified 3D tomographic reconstruction model, which proves that the algorithm simplification is feasible and it can be applied to the reconstruction of 3D volume particle field in a Tomo-PIV system.
3D object-oriented image analysis in 3D geophysical modelling
Fadel, I.; van der Meijde, M.; Kerle, N.
2015-01-01
Non-uniqueness of satellite gravity interpretation has traditionally been reduced by using a priori information from seismic tomography models. This reduction in the non-uniqueness has been based on velocity-density conversion formulas or user interpretation of the 3D subsurface structures (objects......) based on the seismic tomography models and then forward modelling these objects. However, this form of object-based approach has been done without a standardized methodology on how to extract the subsurface structures from the 3D models. In this research, a 3D object-oriented image analysis (3D OOA......) approach was implemented to extract the 3D subsurface structures from geophysical data. The approach was applied on a 3D shear wave seismic tomography model of the central part of the East African Rift System. Subsequently, the extracted 3D objects from the tomography model were reconstructed in the 3D...
3-D Human Modeling and Animation
Ratner, Peter
2012-01-01
3-D Human Modeling and Animation Third Edition All the tools and techniques you need to bring human figures to 3-D life Thanks to today's remarkable technology, artists can create and animate realistic, three-dimensional human figures that were not possible just a few years ago. This easy-to-follow book guides you through all the necessary steps to adapt your own artistic skill in figure drawing, painting, and sculpture to this exciting digital canvas. 3-D Human Modeling and Animation, Third Edition starts you off with simple modeling, then prepares you for more advanced techniques for crea
FIT3D: Fitting optical spectra
Sánchez, S. F.; Pérez, E.; Sánchez-Blázquez, P.; González, J. J.; Rosales-Ortega, F. F.; Cano-Díaz, M.; López-Cobá, C.; Marino, R. A.; Gil de Paz, A.; Mollá, M.; López-Sánchez, A. R.; Ascasibar, Y.; Barrera-Ballesteros, J.
2016-09-01
FIT3D fits optical spectra to deblend the underlying stellar population and the ionized gas, and extract physical information from each component. FIT3D is focused on the analysis of Integral Field Spectroscopy data, but is not restricted to it, and is the basis of Pipe3D, a pipeline used in the analysis of datasets like CALIFA, MaNGA, and SAMI. It can run iteratively or in an automatic way to derive the parameters of a large set of spectra.
3D Immersive Visualization with Astrophysical Data
Kent, Brian R.
2017-01-01
We present the refinement of a new 3D immersion technique for astrophysical data visualization.Methodology to create 360 degree spherical panoramas is reviewed. The 3D software package Blender coupled with Python and the Google Spatial Media module are used together to create the final data products. Data can be viewed interactively with a mobile phone or tablet or in a web browser. The technique can apply to different kinds of astronomical data including 3D stellar and galaxy catalogs, images, and planetary maps.
3D Printing the ATLAS' barrel toroid
Goncalves, Tiago Barreiro
2016-01-01
The present report summarizes my work as part of the Summer Student Programme 2016 in the CERN IR-ECO-TSP department (International Relations – Education, Communication & Outreach – Teacher and Student Programmes). Particularly, I worked closely with the S’Cool LAB team on a science education project. This project included the 3D designing, 3D printing, and assembling of a model of the ATLAS’ barrel toroid. A detailed description of the project' development is presented and a short manual on how to use 3D printing software and hardware is attached.
3D face modeling, analysis and recognition
Daoudi, Mohamed; Veltkamp, Remco
2013-01-01
3D Face Modeling, Analysis and Recognition presents methodologies for analyzing shapes of facial surfaces, develops computational tools for analyzing 3D face data, and illustrates them using state-of-the-art applications. The methodologies chosen are based on efficient representations, metrics, comparisons, and classifications of features that are especially relevant in the context of 3D measurements of human faces. These frameworks have a long-term utility in face analysis, taking into account the anticipated improvements in data collection, data storage, processing speeds, and application s
A high capacity 3D steganography algorithm.
Chao, Min-Wen; Lin, Chao-hung; Yu, Cheng-Wei; Lee, Tong-Yee
2009-01-01
In this paper, we present a very high-capacity and low-distortion 3D steganography scheme. Our steganography approach is based on a novel multilayered embedding scheme to hide secret messages in the vertices of 3D polygon models. Experimental results show that the cover model distortion is very small as the number of hiding layers ranges from 7 to 13 layers. To the best of our knowledge, this novel approach can provide much higher hiding capacity than other state-of-the-art approaches, while obeying the low distortion and security basic requirements for steganography on 3D models.
RHOCUBE: 3D density distributions modeling code
Nikutta, Robert; Agliozzo, Claudia
2016-11-01
RHOCUBE models 3D density distributions on a discrete Cartesian grid and their integrated 2D maps. It can be used for a range of applications, including modeling the electron number density in LBV shells and computing the emission measure. The RHOCUBE Python package provides several 3D density distributions, including a powerlaw shell, truncated Gaussian shell, constant-density torus, dual cones, and spiralling helical tubes, and can accept additional distributions. RHOCUBE provides convenient methods for shifts and rotations in 3D, and if necessary, an arbitrary number of density distributions can be combined into the same model cube and the integration ∫ dz performed through the joint density field.
Computer Modelling of 3D Geological Surface
Kodge, B G
2011-01-01
The geological surveying presently uses methods and tools for the computer modeling of 3D-structures of the geographical subsurface and geotechnical characterization as well as the application of geoinformation systems for management and analysis of spatial data, and their cartographic presentation. The objectives of this paper are to present a 3D geological surface model of Latur district in Maharashtra state of India. This study is undertaken through the several processes which are discussed in this paper to generate and visualize the automated 3D geological surface model of a projected area.
Biedron, Robert T.; Carlson, Jan-Renee; Derlaga, Joseph M.; Gnoffo, Peter A.; Hammond, Dana P.; Jones, William T.; Kleb, Bil; Lee-Rausch, Elizabeth M.; Nielsen, Eric J.; Park, Michael A.; Rumsey, Christopher L.; Thomas, James L.; Wood, William A.
2015-01-01
This manual describes the installation and execution of FUN3D version 12.8, including optional dependent packages. FUN3D is a suite of computational fluid dynamics simulation and design tools that uses mixed-element unstructured grids in a large number of formats, including structured multiblock and overset grid systems. A discretely-exact adjoint solver enables efficient gradient-based design and grid adaptation to reduce estimated discretization error. FUN3D is available with and without a reacting, real-gas capability. This generic gas option is available only for those persons that qualify for its beta release status.
Biedron, Robert T.; Derlaga, Joseph M.; Gnoffo, Peter A.; Hammond, Dana P.; Jones, William T.; Kleb, William L.; Lee-Rausch, Elizabeth M.; Nielsen, Eric J.; Park, Michael A.; Rumsey, Christopher L.; Thomas, James L.; Wood, William A.
2015-01-01
This manual describes the installation and execution of FUN3D version 12.6, including optional dependent packages. FUN3D is a suite of computational fluid dynamics simulation and design tools that uses mixed-element unstructured grids in a large number of formats, including structured multiblock and overset grid systems. A discretely-exact adjoint solver enables efficient gradient-based design and grid adaptation to reduce estimated discretization error. FUN3D is available with and without a reacting, real-gas capability. This generic gas option is available only for those persons that qualify for its beta release status.
Biedron, Robert T.; Derlaga, Joseph M.; Gnoffo, Peter A.; Hammond, Dana P.; Jones, William T.; Kleb, William L.; Lee-Rausch, Elizabeth M.; Nielsen, Eric J.; Park, Michael A.; Rumsey, Christopher L.; Thomas, James L.; Wood, William A.
2014-01-01
This manual describes the installation and execution of FUN3D version 12.5, including optional dependent packages. FUN3D is a suite of computational uid dynamics simulation and design tools that uses mixed-element unstructured grids in a large number of formats, including structured multiblock and overset grid systems. A discretely-exact adjoint solver enables ecient gradient-based design and grid adaptation to reduce estimated discretization error. FUN3D is available with and without a reacting, real-gas capability. This generic gas option is available only for those persons that qualify for its beta release status.
Biedron, Robert T.; Carlson, Jan-Renee; Derlaga, Joseph M.; Gnoffo, Peter A.; Hammond, Dana P.; Jones, William T.; Kleb, Bil; Lee-Rausch, Elizabeth M.; Nielsen, Eric J.; Park, Michael A.; Rumsey, Christopher L.; Thomas, James L.; Wood, William A.
2017-01-01
This manual describes the installation and execution of FUN3D version 13.1, including optional dependent packages. FUN3D is a suite of computational fluid dynamics simulation and design tools that uses mixed-element unstructured grids in a large number of formats, including structured multiblock and overset grid systems. A discretely-exact adjoint solver enables efficient gradient-based design and grid adaptation to reduce estimated discretization error. FUN3D is available with and without a reacting, real-gas capability. This generic gas option is available only for those persons that qualify for its beta release status.
Biedron, Robert T.; Derlaga, Joseph M.; Gnoffo, Peter A.; Hammond, Dana P.; Jones, William T.; Kleb, Bil; Lee-Rausch, Elizabeth M.; Nielsen, Eric J.; Park, Michael A.; Rumsey, Christopher L.; Thomas, James L.; Wood, William A.
2014-01-01
This manual describes the installation and execution of FUN3D version 12.4, including optional dependent packages. FUN3D is a suite of computational fluid dynamics simulation and design tools that uses mixedelement unstructured grids in a large number of formats, including structured multiblock and overset grid systems. A discretely-exact adjoint solver enables efficient gradient-based design and grid adaptation to reduce estimated discretization error. FUN3D is available with and without a reacting, real-gas capability. This generic gas option is available only for those persons that qualify for its beta release status.
Biedron, Robert T.; Carlson, Jan-Renee; Derlaga, Joseph M.; Gnoffo, Peter A.; Hammond, Dana P.; Jones, William T.; Kleb, Bil; Lee-Rausch, Elizabeth M.; Nielsen, Eric J.; Park, Michael A.; Rumsey, Christopher L.; Thomas, James L.; Wood, William A.
2015-01-01
This manual describes the installation and execution of FUN3D version 12.7, including optional dependent packages. FUN3D is a suite of computational fluid dynamics simulation and design tools that uses mixed-element unstructured grids in a large number of formats, including structured multiblock and overset grid systems. A discretely-exact adjoint solver enables efficient gradient-based design and grid adaptation to reduce estimated discretization error. FUN3D is available with and without a reacting, real-gas capability. This generic gas option is available only for those persons that qualify for its beta release status.
Automatic balancing of 3D models
Christiansen, Asger Nyman; Schmidt, Ryan; Bærentzen, Jakob Andreas
2014-01-01
3D printing technologies allow for more diverse shapes than are possible with molds and the cost of making just one single object is negligible compared to traditional production methods. However, not all shapes are suitable for 3D print. One of the remaining costs is therefore human time spent......, in these cases, we will apply a rotation of the object which only deforms the shape a little near the base. No user input is required but it is possible to specify manufacturing constraints related to specific 3D print technologies. Several models have successfully been balanced and printed using both polyjet...
Participation and 3D Visualization Tools
Mullins, Michael; Jensen, Mikkel Holm; Henriksen, Sune
2004-01-01
With a departure point in a workshop held at the VR Media Lab at Aalborg University , this paper deals with aspects of public participation and the use of 3D visualisation tools. The workshop grew from a desire to involve a broad collaboration between the many actors in the city through using new...... perceptions of architectural representation in urban design where 3D visualisation techniques are used. It is the authors? general finding that, while 3D visualisation media have the potential to increase understanding of virtual space for the lay public, as well as for professionals, the lay public require...
The reactor dynamics code DYN3D
Kliem, Soeren; Bilodid, Yuri; Fridman, Emil; Baier, Silvio; Grahn, Alexander; Gommlich, Andre; Nikitin, Evgeny; Rohde, Ulrich [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany)
2016-05-15
The article provides an overview on the code DYN3D which is a three-dimensional core model for steady-state, dynamic and depletion calculations in reactor cores with quadratic or hexagonal fuel assembly geometry being developed by the Helmholtz-Zentrum Dresden-Rossendorf for more than 20 years. The current paper gives an overview on the basic DYN3D models and the available code couplings. The verification and validation status is shortly outlined. The paper concludes with the current developments of the DYN3D code. For more detailed information the reader is referred to the publications cited in the corresponding chapters.
3D jet printer of edible gels for food creation
Serizawa, Ryo; Shitara, Mariko; Gong, Jin; Makino, Masato; Kabir, M. Hasnat; Furukawa, Hidemitsu
2014-03-01
In recent years, aging is progressing in Japan. Elderly people can't swallow the food well. So, the need of soft food is increasing greatly with the aging of the population. There are so few satisfying foods for the elderly to enjoy a meal. An equipment of printing soft food gives the elderly a big dream and is promising. In this study, we aim at developing a 3D edible gel printer in order to make soft food for the elderly. We made a prototype of the 3D edible gel printer. The printer consists of syringe pump and dispenser. The syringe pump extrudes the solution. The dispenser allows to model threedimensional objects. We use agar solution as the ink to carry out the printing. Agar's gelation deeply depends on temperature. Therefore temperature control of the solution is important to mold optimal shapes because the physical crosslinking network of agar's solution is instable. We succeeded in making the gels and plate-shape gel using the 3D edible gel printer. Further more, in order to increase the gelation speed agar's solution, we changed the dispenser and the printing test is being done now. 4 kinds of soft food prepared from agar and gelatin were printed by the 3D edible gel printer. The compression tests of the printed soft food samples were done and their hardness is measured because the hardness is one of very important factors which influence the food texture greatly. In the future, the viscosity of the agar solution or other food ink should be adjusted to suitable for printing.
Do-It-Yourself: 3D Models of Hydrogenic Orbitals through 3D Printing
Griffith, Kaitlyn M.; de Cataldo, Riccardo; Fogarty, Keir H.
2016-01-01
Introductory chemistry students often have difficulty visualizing the 3-dimensional shapes of the hydrogenic electron orbitals without the aid of physical 3D models. Unfortunately, commercially available models can be quite expensive. 3D printing offers a solution for producing models of hydrogenic orbitals. 3D printing technology is widely…
3D presentatie van geluid in de cockpit [3D sound presentation in the cockpit
Bronkhorst, A.W.
2003-01-01
A.W. Bronkhorst, 3D-presentatie van geluid in de cockpit 1 Using virtual acoustics, sound can be presented from virtual sources located in the 3D space around the listener. This 3D sound has interesting applications in the cockpit. Sounds can be used to convey directional information, and interferen
Hydrodynamic growth experiments with the 3-D, “native-roughness” modulations on NIF
Smalyuk, V. A.; Weber, S. V.; Casey, D.; Clark, D. S.; Coppari, F.; Field, J. E.; Haan, S. W.; Hammel, B. A.; Hamza, A.; Hsing, W.; Landen, O.; Nikroo, A.; Robey, H. F.; Weber, C. R.
2016-05-01
Hydrodynamic instability growth experiments with threedimensional (3-D) surface-roughness modulations were performed on plastic (CH) shell spherical implosions at the National Ignition Facility (NIF). The initial capsule outer-surface roughness was similar to the standard specifications (“native roughness”) used in a majority of implosions on NIF. At a convergence ratio of ∼3, the measured tent modulations were close to those predicted by 3-D simulations (within ∼15-20%), while measured 3-D, broadband modulations were ∼3-4 times larger than those simulated based on the growth of the known imposed initial surface modulations. One of the hypotheses to explain the results is based on the increased instability amplitudes due to modulations of the oxygen content in the bulk of the capsule. These new experiments results have prompted looking for ways to reduce UV light exposure during target fabrication.
Networked 3D Virtual Museum System
无
2003-01-01
Virtual heritage has become increasingly important in the conservation, preservation, and interpretation of our cultural and natural history. Moreover, rapid advances in digital technologies in recent years offer virtual heritage new direction. This paper introduces our approach toward a networked 3D virtual museum system, especially, how to model, manage, present virtual heritages and furthermore how to use computer network for the share of virtual heritage in the networked virtual environment. This paper first addresses a 3D acquisition and processing technique for virtual heritage modeling and shows some illustrative examples. Then, this paper describes a management of virtual heritage assets that are composed by various rich media. This paper introduces our schemes to present the virtual heritages, which include 3D virtual heritage browser system, CAVE system, and immersive VR theater. Finally, this paper presents the new direction of networked 3D virtual museum of which main idea is remote guide of the virtual heritage using the mixed reality technique.
Two Accelerating Techniques for 3D Reconstruction
刘世霞; 胡事民; 孙家广
2002-01-01
Automatic reconstruction of 3D objects from 2D orthographic views has been a major research issue in CAD/CAM. In this paper, two accelerating techniques to improve the efficiency of reconstruction are presented. First, some pseudo elements are removed by depth and topology information as soon as the wire-frame is constructed, which reduces the searching space. Second, the proposed algorithm does not establish all possible surfaces in the process of generating 3D faces. The surfaces and edge loops are generated by using the relationship between the boundaries of 3D faces and their projections. This avoids the growth in combinational complexity of previous methods that have to check all possible pairs of 3D candidate edges.
3D-FPA Hybridization Improvements Project
National Aeronautics and Space Administration — Advanced Scientific Concepts, Inc. (ASC) is a small business, which has developed a compact, eye-safe 3D Flash LIDARTM Camera (FLC) well suited for real-time...
The 3-d view of planetary nebulae
Hugo E. Schwarz
2006-01-01
Full Text Available Considerando las nebulosas planetarias (PNe de manera tridimensional (3-D, demonstramos que se pueden reducir las grandes incertidumbres asociadas con los m etodos cl asicos de modelar y observar PNe para obtener sus estructuras 3-D y distancias. Usando espectrofotometr a de ranura larga o empleando un Integral Field Unit para restringir los modelos de fotoionizaci on 3-D de PNe y as eliminar dicha incertidumbre de la densidad y de la fracci on del volumen que emite radiaci on ( lling factor, determinamos las detalladas estructuras 3-D, los par ametros de las estrellas centrales y las distancias con una precisi on de 10-20%. Los m etodos cl asicos t picamente daban estos par ametros con una incertidumbre de un factor 3 o m as.
Nonlaser-based 3D surface imaging
Lu, Shin-yee; Johnson, R.K.; Sherwood, R.J. [Lawrence Livermore National Lab., CA (United States)
1994-11-15
3D surface imaging refers to methods that generate a 3D surface representation of objects of a scene under viewing. Laser-based 3D surface imaging systems are commonly used in manufacturing, robotics and biomedical research. Although laser-based systems provide satisfactory solutions for most applications, there are situations where non laser-based approaches are preferred. The issues that make alternative methods sometimes more attractive are: (1) real-time data capturing, (2) eye-safety, (3) portability, and (4) work distance. The focus of this presentation is on generating a 3D surface from multiple 2D projected images using CCD cameras, without a laser light source. Two methods are presented: stereo vision and depth-from-focus. Their applications are described.
Designing Biomaterials for 3D Printing.
Guvendiren, Murat; Molde, Joseph; Soares, Rosane M D; Kohn, Joachim
2016-10-10
Three-dimensional (3D) printing is becoming an increasingly common technique to fabricate scaffolds and devices for tissue engineering applications. This is due to the potential of 3D printing to provide patient-specific designs, high structural complexity, rapid on-demand fabrication at a low-cost. One of the major bottlenecks that limits the widespread acceptance of 3D printing in biomanufacturing is the lack of diversity in "biomaterial inks". Printability of a biomaterial is determined by the printing technique. Although a wide range of biomaterial inks including polymers, ceramics, hydrogels and composites have been developed, the field is still struggling with processing of these materials into self-supporting devices with tunable mechanics, degradation, and bioactivity. This review aims to highlight the past and recent advances in biomaterial ink development and design considerations moving forward. A brief overview of 3D printing technologies focusing on ink design parameters is also included.
DNA biosensing with 3D printing technology.
Loo, Adeline Huiling; Chua, Chun Kiang; Pumera, Martin
2017-01-16
3D printing, an upcoming technology, has vast potential to transform conventional fabrication processes due to the numerous improvements it can offer to the current methods. To date, the employment of 3D printing technology has been examined for applications in the fields of engineering, manufacturing and biological sciences. In this study, we examined the potential of adopting 3D printing technology for a novel application, electrochemical DNA biosensing. Metal 3D printing was utilized to construct helical-shaped stainless steel electrodes which functioned as a transducing platform for the detection of DNA hybridization. The ability of electroactive methylene blue to intercalate into the double helix structure of double-stranded DNA was then exploited to monitor the DNA hybridization process, with its inherent reduction peak serving as an analytical signal. The designed biosensing approach was found to demonstrate superior selectivity against a non-complementary DNA target, with a detection range of 1-1000 nM.
Cubical Cohomology Ring of 3D Photographs
Gonzalez-Diaz, Rocio; Medrano, Belen; 10.1002/ima.20271
2011-01-01
Cohomology and cohomology ring of three-dimensional (3D) objects are topological invariants that characterize holes and their relations. Cohomology ring has been traditionally computed on simplicial complexes. Nevertheless, cubical complexes deal directly with the voxels in 3D images, no additional triangulation is necessary, facilitating efficient algorithms for the computation of topological invariants in the image context. In this paper, we present formulas to directly compute the cohomology ring of 3D cubical complexes without making use of any additional triangulation. Starting from a cubical complex $Q$ that represents a 3D binary-valued digital picture whose foreground has one connected component, we compute first the cohomological information on the boundary of the object, $\\partial Q$ by an incremental technique; then, using a face reduction algorithm, we compute it on the whole object; finally, applying the mentioned formulas, the cohomology ring is computed from such information.
3D scanning particle tracking velocimetry
Hoyer, Klaus; Holzner, Markus; Lüthi, Beat; Guala, Michele; Liberzon, Alexander; Kinzelbach, Wolfgang
2005-11-01
In this article, we present an experimental setup and data processing schemes for 3D scanning particle tracking velocimetry (SPTV), which expands on the classical 3D particle tracking velocimetry (PTV) through changes in the illumination, image acquisition and analysis. 3D PTV is a flexible flow measurement technique based on the processing of stereoscopic images of flow tracer particles. The technique allows obtaining Lagrangian flow information directly from measured 3D trajectories of individual particles. While for a classical PTV the entire region of interest is simultaneously illuminated and recorded, in SPTV the flow field is recorded by sequential tomographic high-speed imaging of the region of interest. The advantage of the presented method is a considerable increase in maximum feasible seeding density. Results are shown for an experiment in homogenous turbulence and compared with PTV. SPTV yielded an average 3,500 tracked particles per time step, which implies a significant enhancement of the spatial resolution for Lagrangian flow measurements.
Lightning fast animation in Element 3D
Audronis, Ty
2014-01-01
An easy-to-follow and all-inclusive guide, in which the underlying principles of 3D animation as well as their importance are explained in detail. The lessons are designed to teach you how to think of 3D animation in such a way that you can troubleshoot any problem, or animate any scene that comes your way.If you are a Digital Artist, Animation Artist, or a Game Programmer and you want to become an expert in Element 3D, this is the book for you. Although there are a lot of basics for beginners in this book, it includes some advanced techniques for both animating in Element 3D, and overcoming i
Advanced 3D Object Identification System Project
National Aeronautics and Space Administration — Optra will build an Advanced 3D Object Identification System utilizing three or more high resolution imagers spaced around a launch platform. Data from each imager...