This report discusses topics on hydrodynamics instabilities in inertial confinement: linear analysis of Rayleigh-Taylor instability; ablation-surface instability; bubble rise in late-stage Rayleigh-Taylor instability; and saturation and multimode interactions in ...
Energy Citations Database
... Abstract : Techniques have been developed to improve the uniformity of the laser focal profile to reduce the ablative Rayleigh Taylor instability, and ...
DTIC Science & Technology
... Perturbations that seed Rayleigh-Taylor (RT) instability in laser-driven targets ... uniformity (laser imprint, surface ripple) are expected to oscillate. ...
... Abstract : Perturbations that seed Rayleigh-Taylor (RT) instability in laser-driven targets form during the early-time period. ...
... This process redistributes mass in the volume of the target, forming the feedout-generated seed for ablative Rayleigh-Taylor (RT) instability. ...
... Rayleigh-Taylor Instability in Compressible Media ... 11 TITLE (Include Security Classification) Rayleigh-Taylor Instability in Compressible Media 12. ...
This report discusses topics on hydrodynamics instabilities in inertial confinement: linear analysis of Rayleigh-Taylor instability; ablation-surface instability; bubble rise in late-stage Rayleigh-Taylor instability; and saturation and multimode interact...
National Technical Information Service (NTIS)
A laminated ablator is explored as an alternative concept for stabilizing the ablative Rayleigh-Taylor instability which develops in inertial fusion targets. Experiments measuring the growth of the Rayleigh-Taylor instability of laminated planar foils are reported. Consistent with both theory ...
PubMed
NASA Astrophysics Data System (ADS)
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. ...
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 ...
This article presents a theory of these instabilities and potential modes of failure caused by them. Discussions are given for the following: small amplitude growth of the outside surface instability; and modes of failure resulting from nonlinear development of the inside surface instability.
... Accession Number : ADA138544. Title : Rayleigh-Taylor Instability in the Presence of a Stratified Shear Layer. Descriptive ...
Numerical studies of the ablation-driven Rayleigh-Taylor instability in laser-accelerated targets show growth rates typically within a factor of 2 of the classical growth rate. The appearance of ''Kelvin-Helmholtz'' instability depends on the form of the initial perturbation and ...
A fully three-dimensional (3D) laser-matter interaction code is developed and used to investigate 3D mixing mechanisms in planar targets accelerated by single-sided laser illumination. While linear Rayleigh-Taylor growth rates from 3D perturbed simulations are identical to those obtained from 2D simulations, nonlinear evolution differs significantly. Vortex stretching alters ...
Linear theory of the ablative Rayleigh-Taylor instability in anisotropic diffusive materials is presented. This analysis indicates that enhancing diffusion in a plane transverse to the mean longitudinal flow can strongly reduce the growth of the instability. In the context of inertial confinement fusion, it is ...
The combined effect of viscosity and vorticity on the growth rate of the bubble associated with single mode Rayleigh-Taylor instability is investigated. It is shown that the effect of viscosity on the motion of the lighter fluid associated with vorticity accumulated inside the bubble due to mass ablation may be such as to reduce the ...
The evolution of the Rayleigh-Taylor (RT) instability in a compressible medium was investigated both at an accelerating embedded interface and at the ablation front in a new series of experiments on Nova. The x-ray drive generated in a hohlraum ablatively...
Techniques have been developed to improve the uniformity of the laser focal profile to reduce the ablative Rayleigh Taylor instability, and to suppress the various laser plasma instabilities. There are now three ignition target design concepts that utiliz...
A fully nonlinear sharp-boundary model of the ablative Rayleigh-Taylor instability is derived and closed in a similar way to the self-consistent closure of the linear theory. It contains the stabilizing effect of ablation and accurately reproduces the results of 2D DRACO simulations. The single-mode saturation ...
A model for the nonlinear spectrum of the ablative Rayleigh-Taylor instability in laser-accelerated planar plasmas has been developed for a wide range of Froude numbers and scale sizes. It is found that the spectrum can be characterized by an inverse power law with spectral index of approximately 2 in the limit of small-wavenumber ...
DOE Information Bridge
. How does the flame accelerate? � Flame instabilities (Landau-Darrieus, Rayleigh-Taylor) � Interaction Rayleigh-Taylor Instability Rayleigh-Taylor � Buoyancy driven instability. � Large amounts of surface area
E-print Network
The highly nonlinear evolution of the single-mode Rayleigh-Taylor instability (RTI) at the ablation front of an accelerated target is investigated in the parameter range typical of inertial confinement fusion implosions. A new phase of the nonlinear bubble evolution is discovered. After the linear growth phase and a short ...
... Accession Number : ADA145491. Title : Rayleigh-Taylor Instability in Compressible Media. Descriptive Note : Interim rept. ...
... Title : RAYLEIGH-TAYLOR INSTABILITY IN LIQUID-METAL SYNCHRONOUS MHD GENERATORS AND METHODS OF STABILIZING IT,. ...
... Accession Number : ADA047402. Title : Nonlinear Theory of the Collisional Rayleigh-Taylor Instability in Equatorial Spread F. ...
). Produces ~ 0.6 M 56 Ni. How does the flame accelerate? � Flame instabilities (Landau-Darrieus, Rayleigh-Taylor as subgrid models. R us #12;Reactive Rayleigh-Taylor Instability Rayleigh-Taylor � Buoyancy driven
We present the results of a series of detailed numerical simulations of the Rayleigh-Taylor instability in laser ablatively accelerated targets for a fairly wide range of initial conditions. It is shown that the Rayleigh-Taylor growth rate in an ablative ...
We report the formation of jet-like long spike in the nonlinear evolution of the ablative Rayleigh-Taylor instability (ARTI) experiments by numerical simulations. A preheating model ?(T) = ?SH[1 + f(T)], where ?SH is the Spitzer-H�rm (SH) electron conductivity and f(T) interprets the preheating tongue effect in the cold plasma ahead ...
Size invariance of the granular Rayleigh-Taylor instability Jan Ludvig Vinningland,1, �istein scaling behavior of the granular Rayleigh-Taylor instability [Phys. Rev. Lett. 99, 048001 (2007.70.Qj Keywords: granular flow, gravitational instability, Rayleigh-Taylor ...
In the frame of a CEA/US DOE collaboration, convergent experiments have been done on the Nova laser. Numerical simulations with our 2D Lagrangian code FCI2 led the analysis and correctly reproduced the experimental data. From single mode 2D perturbations, ablation front Rayleigh-Taylor instability growth is computed. Moderate and high ...
1 Modeling Rayleigh-Taylor Instability of a Sedimenting Suspension Arising in Direct Numerical gives rise to fingering which resembles Rayleigh-Taylor instability. The waves have a well- defined wavelength and growth rate which can be modeled as a conventional Rayleigh- ...
Center for Nonlinear Studies Rayleigh-Taylor Instability A heavy fluid (heavy) supported against gravity (g) by a lighter fluid (light) constitutes an unstable situation (Rayleigh-Taylor instability � RT of the turbulent Rayleigh-Taylor (RT) instability using ...
LEMTA UMR CNRS 7563 PREPRINT Crossover between Rayleigh-Taylor Instability and turbulent cascading-Plateau, Rayleigh-Taylor or Kelvin-Helmholtz mechanism) or to turbulent cascades similar to Richardson-Plateau mechanism), acceleration of a droplet in the ambient air (Rayleigh-Taylor mechanism) and shear ...
Granular Rayleigh-Taylor instability Jan Ludvig Vinningland1 , �istein Johnsen1 , Eirik G. Flekk�y1 reported by V�ltz shares its main qualitative characteristics with the classical Rayleigh- Taylor glass plates. The internal dimensions of the cell are 56 mm � #12;Granular ...
Granular Rayleigh-Taylor instability Jan Ludvig Vinningland , �istein Johnsen , Eirik G. Flekk�y of spatial scale. Keywords: granular flow, Rayleigh-Taylor instability, pattern formation, size invariance to the classical Rayleigh-Taylor insta- bility [11] the coarsening process observed in ...
It is vital to identify and control all perturbation sources that could trigger ablative Rayleigh-Taylor instability One obvious perturbation 'seed' is surface roughness computed perturbation growth, validated by experiments - Specification for allowable roughness of NIF ignition capsule' is based on But what ...
The growth rate of the ablative Rayleigh-Taylor instability is approximated by gamma = square root[kg/(1 + kL)] - beta km/rho(a), where k is the perturbation wave number, g the gravity, L the density scale length, m the mass ablation rate, and rho(a) the peak target density. The coefficient beta was evaluated for ...
Nonideal Rayleigh-Taylor Mixing H. Lim , J. Iwerks , J. Glimm , and D. H. Sharp Department States of America Rayleigh-Taylor mixing is a classical hydrodynamic instability, which occurs when. Introduction Rayleigh-Taylor (RT) instability is a classical hydrodynamic instabil- ity [4, 34] which ...
/2 =exp(y/L) Inverted-density fluid Rayleigh-Taylor Instability Instability #12;"Bad Curvature" instability in plasmas Inverted Pendulum / Rayleigh-Taylor Instability Top view of toroidal plasma: plasma = heavy fluid
A weakly nonlinear model is proposed for the Rayleigh-Taylor instability in presence of ablation and thermal transport. The nonlinear effects for a single-mode disturbance are computed, included the nonlinear correction to the exponential growth of the fundamental modulation. Mode coupling in the spectrum of a multimode disturbance is thoroughly analyzed ...
Techniques have been developed to improve the uniformity of the laser focal profile, to reduce the ablative Rayleigh-Taylor instability, and to suppress the various laser-plasma instabilities. There are now three direct-drive ignition target designs that utilize these techniques. Evaluation of these designs is ...
Perturbations that seed Rayleigh-Taylor (RT) instability in laser- driven targets form during the early-time period. This time includes a shock wave transit from the front to the rear surface of the target, and a rarefaction wave transit in the opposite d...
... Accession Number : AD0764119. Title : Viscous Effects in Rayleigh- Taylor Instability. Descriptive Note : Technical rept.,. ...
... INSTABILITIES, *RADIO WAVES, RAYLEIGH TAYLOR INSTABILITY, VERY LOW FREQUENCY, TSUNAMIS, IONOSONDES, EARTHQUAKES. ...
expansion, i.e., conditions arise for the growth of MHD Rayleigh-Taylor instability, which would lead, constituting a condition for the growth of MHD Rayleigh-Taylor instability. Development of MHD instabilities
Rayleigh-Taylor instability, the flow instability at a horizontal interface between two fluids with different densities, is demonstrated by a series of experiments that are suited for secondary and college level teaching. (c) 1999 American Institute of Physics.
The theoretical work previously done on Rayleigh Taylor instability in compressible fluids has been reviewed in a chapter written for the Encyclopedia of Fluid Mechanics, to be published by Gulf. The physical basis of the instability, the dependence of gr...
The nonlinear behavior of the collisional Rayleigh-Taylor instability is studied in equatorial Spread F by including a dominant two-dimensional nonlinearity. It is found that on account of this nonlinearity, the instability saturates by generating damped ...
The saturation of the hydromagnetic Rayleigh-Taylor instability is caused by the reduction of driving current in the bubble region between the spikes formed as the instability develops. For short wavelengths, linear magnetic-field diffusion provides the n...
Indirectly driven, ablative Rayleigh-Taylor instability growth measurements in Ge-doped plastic foils were studied using face-on and side-on x-ray radiography. Laminated samples consisting of alternating layers of Ge-doped and undoped plastic and homogeneous Ge-doped foils were considered. We show for the first time that hydrodynamics ...
PLASMAS I. Simple picture of plasma microinstabilities Inverted pendulum Rayleigh-Taylor Magnetic-density fluid Rayleigh-Taylor Instability Instability #12;"Bad Curvature" instability in plasmas Inverted Pendulum / Rayleigh-Taylor Instability Top view ...
aspects of the numerical modelling of Rayleigh- Taylor instabilities will be discussed. The quality by a harmonic with wavelength 2 and amplitude 0.01 (compare table 3.4). Table 4.1 Rayleigh-Taylor instability x Analytical 0.05313 #12;Rayleigh-Taylor ...
Due to the sensitivity of Rayleigh-Taylor instabilities to initial conditions and due to the difficulty of forming well controlled cylindrical or spherical fluid interfaces, Rayleigh-Taylor experiments are often performed with simple, planar interfaces. R...
The goal of the EZturb mix model in KULL is to predict the turbulent mixing process as it evolves from Rayleigh-Taylor, Richtmyer-Meshkov, or Kelvin-Helmholtz instabilities. In this report we focus on a simple example of the Rayleigh-Taylor instability (w...
The evolution of the multimode Rayleigh-Taylor instability of nearly incompressible fluids, with density ratio r = 2, is investigated by means of two-dimensional hydrodynamic simulations. The study focuses on the effect of the initial perturbation on the ...
The compressible Rayleigh-Taylor instability of a supersonic accelerated contact discontinuity between two gases is studied by numerically solving the two-dimensional Euler equations. The computed solutions exhibit a complicated set of nonlinear waves com...
An account is provided of preliminary flow visualization observations made in an unstably stratified
NASA Technical Reports Server (NTRS)
... blast waves contain a contact surface (denoting the interface between the detonation products and the air) which is Rayleigh- Taylor instability. ...
... Theory and Experimental Observations of the Local Collisional Rayleigh-Taylor Instability in a Descending Equatorial Spread-F Ionosphere. ...
... than limited by the usual diffusion processes appears to be controlled by dynamic mixing processes arising from Rayleigh-Taylor instabilities at, for ...
studied. PACS numbers: 47.27.wj, 47.27.tb, 47.27.-i Keywords: Rayleigh-Taylor instability, turbulent mixing, Kolmogorov scaling law, subgrid models I. INTRODUCTION Rayleigh-Taylor (RT) instability occurs simulation with physical mass diffusion8,9 models the Banerjee-Andrews air-helium ...
studied. PACS numbers: 47.27.wj, 47.27.tb, 47.27.-i Keywords: Rayleigh-Taylor instability, turbulent mixing, Kolmogorov scaling law, subgrid models I. INTRODUCTION Rayleigh-Taylor (RT) instability occurs,15 models the Banerjee-Andrews air-helium Rayleigh-Taylor experiments1 . In this ...
motivated by supernova and laser experiments, and a two-dimensional Rayleigh-Taylor instability problem are used as numerical test problems. For the two-dimensional Rayleigh-Taylor instability problem-dimensional Rayleigh-Taylor instability problem 5,6,4 as our numerical ...
ZHANGy Abstract. In this paper, we establish a Front Tracking method to solve Rayleigh-Taylor (RT, 76M20. Key words and phrases. Front Tracking, Rayleigh-Taylor Instability, Richtmyer #12;RAYLEIGH-TAYLOR AND RICHTMYER-MESHKOV INSTABILITIES 3 method is also a factor to a ect the quality
. How does the flame accelerate? � Flame instabilities (Landau-Darrieus, Rayleigh-Taylor) � Interaction flame models. Look for scaling relations that will act as subgrid models. R us #12;Reactive Rayleigh-Taylor Instability Rayleigh-Taylor � Buoyancy driven ...
. How does the flame accelerate? � Flame instabilities (Landau-Darrieus, Rayleigh-Taylor) � Interaction. Look for scaling relations that will act as subgrid models. R us #12;Reactive Rayleigh-Taylor Instability Rayleigh-Taylor � Buoyancy driven instability. � Large ...
) resorts to instability dynamics (through refinements of Rayleigh-Plateau, Rayleigh-Taylor or Kelvin mechanism), acceleration of a droplet in the ambient air (Rayleigh-Taylor mechanism) and shear instability, that for an industrial nozzle, in the bag-breakup regime, Rayleigh-Taylor ...
scheme. Rayleigh-Taylor instability results from the application of a pressure gradient e.g., a gradient, the objective of this paper is to study the effect of shock waves on the development of the Rayleigh- Taylor and complicated smooth flow features, such as the problem of Rayleigh- ...
Collisional Rayleigh-Taylor instability and shear-flow in equatorial Spread-F plasma N. Chakrabarti1 and G. S November 2002 � Accepted: 14 November 2002 Abstract. Collisional Rayleigh-Taylor (RT) instability and the perturbations. The influence of transverse velocity shear on Rayleigh- ...
was nearly flat, rather than the steep bottom- side, where Rayleigh-Taylor type instabilities are expected of free energy for ionospheric instability. The second was puzzling; Rayleigh-Taylor instabilities Pedersen conductivity existing in the E region. Layers produced by ...
With use of the fast2d laser-shell model, the acceleration of a 20-..mu..m-thick plastic foil up to 160 km/s has been simulated. It is possible to follow the Rayleigh-Taylor bubble-and-spike development far into the nonlinear regime and beyond the point of foil fragmentation. Strong shear flow develops which evolves into the Kelvin-Helmholtz instability. The Kelvin-Helmholtz ...
Beginning from a state of hydrostatic equilibrium, in which a heavy gas rests atop a light gas in a constant gravitational field, Rayleigh-Taylor instability at the interface will launch a shock wave into the upper fluid. The rising bubbles of lighter flu...
Convergent geometry Rayleigh-Taylor experiments have been performed with a 122-point detonation initiation system on cylinders having sinusoidal perturbations on the outer surface ranging from mode-6 to mode-36. Experiments were performed with various per...
- driven Rayleigh-Taylor (RT) instability develops. At later stages, this unstable flow becomes turbulent on immiscible Rayleigh- Taylor turbulence, submitted to Phys. Rev. Lett. 09/2004. Contact Information: Michael
); kkadau@lanl.gov T he Rayleigh-Taylor (RT) instability occurs when a heavy fluid lies on top of a light quickly by the wave number corresponding Figure 1-- Rayleigh-Taylor mixing of 100,589,840 atoms
comparative study of the turbulent Rayleigh-Taylor instability using high-resolution 3D numerical simulations. Rosner, A. Alexakis, J. Truran and W. Hilderbrandt 14 . "On the miscible Rayleigh-Taylor instability: two 7. Young, Y.-N. "Numerical simulation of double-diffusive convection and miscible ...
, a nondimensional number Rt ("Rayleigh Taylor number.") is defined, which is analogous to the Rayleigh number, Ra (Rayleigh-Taylor) instabilities. Ra-Rt-space is explored up to Ra = 30000 and Rt = 10000. Several f10w; after one Rayleigh-Taylor overturn the f10w may become stable, it may ...
and well studied Rayleigh-Taylor and Richtmyer-Meshkov instabilities which involve acceleration driven acceleration driven instabilities (Rayleigh-Taylor for continuous acceleration and Richtmyer) to obtain these results. Commonly, Rayleigh-Taylor mixing simulations show a factor of two or more
shown in Fig. 8. The initial configuration is similar to the classical Rayleigh-Taylor mixing problem-order methods #12;144 L. Shunn & F. Ham Figure 8. 2-D Rayleigh-Taylor instability. The left figures use node EOS evaluations 145 Figure 9. 2-D Rayleigh-Taylor instability at t = 5.2. (left ...
in an impulsively accelerated free stream, and the 3D immiscible Rayleigh-Taylor instability. Conclusions are given�128�128 with a domain size of 5D�5D�5D. 5.2. Rayleigh-Taylor Problem The Rayleigh-Taylor instability refers. Recently, the miscible Rayleigh-Taylor problem has been ...
In this research, real gas effects on ablative Rayleigh-Taylor instability are investigated in a plastic target. The real gas effects are included by adopting the quotidian equation of state (QEOS) model. Theoretical solutions for both QEOS and ideal gas EOS are obtained and compared, based on a same set of ...
A new laser fusion target concept is presented with a predicted energy gain of 127 using a 1.3 MJ KrF laser. This energy gain is sufficiently high for an economically attractive fusion reactor. X rays from high- and low-Z materials are used in combination with a low-opacity ablator to spatially tune the isentrope, thereby providing both high fuel compression and a reduction of ...
The spatial-temporal evolution of the ablative Rayleigh-Taylor instability is studied in a finite thickness shell where the perturbation feeds through from the unstable to the stable surface. According to the classical theory of a constant-density, incompressible layer, two linear modes can be identified when the acceleration is ...
and to validate this algorithm through the simulation of 3D Rayleigh-Taylor mixing of miscible fluids, ob- taining The acceleration of the bubble envelope in multimode Rayleigh-Taylor (RT) instability is postulated to depend Rayleigh-Taylor multimode mixing simulations, based on improved physcics modeling and on an ...
simulations (DNS) in two configurations: a) classical Rayleigh-Taylor instability using a 30723 data set [3,4], and b) an idealized triply periodic Rayleigh-Taylor flow named hereafter homogeneous Rayleigh-Taylor
) and turbulent combustion. Classic acceleration-driven instabilities (Rayleigh- Taylor for continuous we provide. In comparing the Smeeton-Youngs to the Mueschke-Andrews fresh-salt water Rayleigh-Taylor perturbations. Thus a central conclusion of our study is that there is nothing universal about ...
. Several numerical tests are performed to show the scheme capabilities. In particular, the viscous Rayleigh-Taylor density flows, Finite Element method, Finite Volume method, Rayleigh-Taylor instability. AMS Subject. This is the configuration chosen for the following numerical test (see subsection 3.2). 20 #12;3.2 Viscous ...
-density layer. We interpret the intrusions as products of a gravitational (Rayleigh-Taylor) instability where al. [2005, Figure 1]. B01303 BRODSKY ET AL.: RAYLEIGH-TAYLOR IN FAULTS 2 of 14 B01303 #12;material and included in this paper. B01303 BRODSKY ET AL.: RAYLEIGH-TAYLOR IN FAULTS 3 of 14 B01303 #12;is ...
... An approximate closed form expression for the growth rate of fluid instabilities in a multi-layered laser-driven target is presented. (Author). ...
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.
... the long wavelength limit of several interchange instabilities (viz., Rayleigh-Taylor, E ... The scaling of these growth rates with wavenumber (k) and ...
Plasma arcs used to accelerate projectiles in railguns are examined to determine their susceptibility to the Rayleigh Taylor interchange instability. The model used is similar to that developed by Tsai, Liskow, and Wilcox, although a number of modificatio...
The cutoff wave number of the ablative Rayleigh--Taylor instability is calculated self-consistently by including the effects of finite thermal conduction. The derived cutoff wave number is quite different from the one obtained with the incompressible fluid ({del}{center_dot}{tilde v}=0) or sharp boundary models, and it is strongly ...
Perturbations on an ICF capsule ablator surface can seed Rayleigh-Taylor instability, which can lead to ablator material being injected into the hot spot, cooling it by radiation. If sufficient mass is injected, the radiative energy loss can be sufficient to quench ignition. Modal growth factors derived from ...
Gated X-ray images of laser-driven implosions can provide movies of typically 16 frames with {approximately} 80 ps time resolution and 10 {micro}m spatial resolution. Cylindrical implosions allow study of convergent hydrodynamics but with excellent diagnostic access down the axis of the cylinder. This example from a recent cylindrical implosion campaign on the OMEGA laser provides quantitative ...
Nonlinear growth of 3D broadband nonuniformities was measured near saturation levels using x-ray radiography in planar foils accelerated by laser light. The initial target modulations were seeded by laser nonuniformities and later amplified during acceleration by Rayleigh-Taylor instability. The nonlinear saturation velocities are measured for the first time and are found to ...
... FUSION, *LASER TARGET INTERACTIONS, STABILIZATION, ABLATION, GROWTH(GENERAL), BOUNDARY LAYER, TARGETS, LASERS, ...
The evolution of the Rayleigh-Taylor (RT) instability in a compressible medium was investigated both at an accelerating embedded interface and at the ablation front in a new series of experiments on Nova. The x-ray drive generated in a hohlraum ablatively accelerated a planar target consisting of a doped plastic pusher which was in ...
4, 2005 (DOI: will be inserted by hand later) Non-stationary Rayleigh-Taylor instability al.: Non-stationary Rayleigh-Taylor instability in supernova ejecta al. (Blondin et al. 2001 + C^r, (5) #12;X. Ribeyre et al.: Non-stationary Rayleigh-Taylor instability in supernova ...
.Willi, "Measurement and Simulation of Laser Imprinting and Consequent Rayleigh-Taylor growth", Phys.Rev.Lett.76, 1643 of three-dimensional Rayleigh-Taylor instability", Phys.Fluids A5, 1904 (1993); X.L.Li, "A numerical study of development of the #12;30 Rayleigh-Taylor instability in 3D ...
Rayleigh--Taylor instabilities of an accelerating plasma sheet are studied by application of normal mode analysis to the one-fluid magnetohydrodynamic equations. The equilibrium unperturbed states are determined by specifying the resistivity law of the current carrying plasma, although resistivity effects are neglected in the developing ...
A large number of volcanic features exist on Venus, ranging from tens of thousands of small domes to
... the stability of free capillary surfaces in rectangular containers against unfavorable disturbances (accelerations, i.e. Rayleigh-Taylor instability). ...
NASA Website
Several mechanisms that reduce the linear growth rate and severity of Rayleigh-Taylor instability in thin, inhomogeneous laser targets are discussed.
Nov 19, 2004 ... In this scenario the plasma instabilities that can occur during the accretion process (Rayleigh-Taylor, Kelvin-Helmoltz, ...
... The outer surface of the liner is driven by a plurality of radially-displaced free-pistons to eliminate high frequency Rayleigh-Taylor instability at the ...
... 1. INTRODUCTION ... relevance to such flows as those in lava lakes, the thermal ... The problem is illustrated in figure 1. Two layers of immiscible fluids ...
... a thin layer of very viscous fluid overlies a deep layer of less viscous, less dense fluid. ... (This conclusion also applies to fluids with power-law ...
... formulated. The new strategy should outperform traditional ones based solely on Rayleigh Taylor-type instability mechanisms. ...
... sunset ionospheric conductance near the South Atlantic Anomaly cause a decrease in growth rate for the generalized Rayleigh-Taylor instability. ...
... In particular, the turn-on conditions for the unmagnetized ion Rayleigh-Taylor instability are derived for both the fluid and kinetic regimes, as well as ...
Natalia Vladimirova, University of Chicago; Michael Chertkov, T-13 T he Rayleigh-Taylor (RT) instability
Issues with coupling efficiency, beam illumination symmetry and Rayleigh Taylor (RT) instability are discussed for spherical heavy-ion-beam-driven targets with and without hohlraums. Efficient coupling of heavy ion beams to compress direct-drive inertial fusion targets without hohlraums is found to require ion range increasing ...
We report the results of 3D piecewise-parabolic-method (PPM) simulations of compressible Rayleigh-Taylor instability and turbulent mixing, mostly for initial equilibria with a sharp density jump. The formation of bubbles and spikes, their subsequent growth and merging, and the evolution of the mean profiles towards a stably-stratified equilibrium are ...
A new wire array configuration has been used to create thin shell-like implosions in a cylindrical array. The setup introduces a ~5 kA, ~25 ns current prepulse followed by a ~140 ns current-free interval before the application of the main (~1 MA) current pulse. The prepulse volumetrically heats the wires which expand to ~1 mm diameter leaving no dense wire core and without development of ...
A new wire array configuration has been used to create thin shell-like implosions in a cylindrical array. The setup introduces a �5kA, �25ns current prepulse followed by a �140ns current-free interval before the application of the main (�1MA) current pulse. The prepulse volumetrically heats the wires which expand to �1mm diameter leaving no dense wire core and without development of ...
The evolution of the Rayleigh-Taylor (RT) instability in a compressible medium has been investigated at an accelerating embedded interface and at the ablation front in a series of experiments on the Nova laser. The x-ray drive generated in a gold hohlraum ablatively accelerated a planar target consisting of a doped plastic pusher ...
structures in Rayleigh- Taylor mixing" Phys.Rev.Lett. 80, 3507 (1998) 7. F.H.Harlow, J.E.Welch, "Numerical.Zemach, "Rayleigh-Taylor instability and the use of conformal maps for ideal fluid flow" Jour.Comp.Phys. 51, 28 of three-dimensional Rayleigh-Taylor instability" ...
During the past year an experimental study of the shock-wave initiated Rayleigh-Taylor instability, also known as the Richtmeyer-Meshkov instability, has been initiated at the shock tube laboratories of the Graduate Aeronautical Laboratories, California I...
The existence Rayleigh-Taylor instabilities, in laser heated plasmas, is shown. By means of the acceleration of flat three-layered Au-Al-Au targets, a mixing zone, under the concept of Rayteigh-Taylor instabilities, is observed. The Al emission spectra is...
A lattice Boltzmann model for multicomponent fluid flows is used to simulate the two-dimensional Rayleigh-Taylor instability. The dynamical processes of the instability, varying from linear growth to mixing, have been simulated. The results agree with experiments, analytical studies, and other numerical simulations. {copyright} {ital ...
The authors investigate hydrodynamic instability of accelerating ionization fronts with two dimensional hydrodynamic simulations. When recombination in the ionized region is turned off, Rayleigh-Taylor instability is effective. Perturbation grows up with classical Rayleigh-Taylor growth rate. In the case with ...
Using the FAST2D laser-shell simulation model we have accelerated a 20 ..mu..m thick plastic foil up to 160 km/s. The foil maintained its integrity up to 10 ns giving an aspect ratio of 40. We are able to follow the Rayleigh-Taylor bubble-and-spike development far into the nonlinear regime and beyond the point of foil fragmentation. Strong shear flow develops at the interface between the ...
Two-dimensional Lagrangian hydrodynamics simulation techniques were used to study fluid instability in laser fusion pellets. A slab geometry comparison with classical Rayleigh-Taylor theory shows good agreement, as do other slab and spherical test problems over a wide range of accelerations and wavelengths. Isentropic ...
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 ...
The evolution of the Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) instabilities in the nonlinear regime of growth was investigated in indirect-drive experiments on the Nova laser. The RT experiments investigated the evolution of both single- and multimode perturbations at an embedded interface, isolated from the effects of ablation. This ``classical`` ...
Both the efficiency of an implosion and the growth rate of hydrodynamic instability increase with the aspect ratio of an implosion. In order to study the physics of implosions with high Rayleigh-Taylor growth factors, we use doped ablators which should minimize x-ray preheat and shell decompression, and hence increase in- flight aspect ...
Target designs for the National Ignition Facility include hohlraum-driven, beryllium alloy ablator capsules. In this type of design, a 1-2 Mbar shock preconditions the capsule wall before the main implosion pulse. Continuum mechanical simulations of the microstructural response have shown that, under certain conditions, the anisotropic behavior of beryllium can seed ...
Potential theory permits ideal fluid dynamics to be formulated in terms of boundary motion. In two dimension, the flow can then be found using conformal mapping. The evolution of some Rayleigh--Taylor instabilities is calculated well into the large amplitude nonlinear regime. The Rayleigh--Taylor calculation for Atwood ratio unity is used as a prototype ...
Effects of temporal density variation and spherical convergence on the nonlinear bubble evolution of single-mode, classical Rayleigh-Taylor instability are studied using an analytical model based on Layzer's theory.
Magnetic Rayleigh-Taylor instability is addressed in compressible hydrostatic media. A full model is presented and compared to numerical results from a linear perturbation code. A perfect agreement between both approaches is obtained in a wide range of parameters. Compressibility effects are examined and substantial deviations from classical Chandrasekhar ...
, CCS-2; Jimmy Fung, Mark Kenamond, Edward Dendy, X-3 T he Rayleigh-Taylor instability (RTI) is a fluid-Mode Rayleigh-Taylor Instability: RAGE and FLAG Hydrocode Comparisons Marianne M. Francois, Robert B. Lowrie.I. Taylor (1950) [2]. Because of the RTI importance in many applications and because it has been widely
The validity of gradient-diffusion closures for modeling turbulent transport in multi-mode Rayleigh Taylor and reshocked Richtmyer Meshkov instability-induced mixing is investigated using data from three dimensional spectral/tenth-order compact difference...
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 ...
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...
The Rayleigh-Taylor (R-T) Instability is studied in the Light Ion Beam (LIB) Inertial Confinement Fusion (ICF) pellet. The R-T instability is one of the problems in ICF. The nonuniform acceleration field and the radiation effects on the LIB-ICF pellet imp...
The instabilities induced by gravity on the interface separating two fluids of different densities (Rayleigh-Taylor instability), one of the two fluids being confined in a thin layer spread on a solid surface, is studied. In the simplest geometry (liquid ...
Heat-flow-induced dynamic overpressure at the perturbed ablation front of an inertial confinement fusion target can stabilize the ablative Richtmyer-Meshkov-like instability and mitigate the subsequent ablative Rayleigh-Taylor (RT) instability. A series of experiments was ...
Through a critical examination of the vortex dynamics of laser ablatively accelerated targets we are able to explain the inhibited linear Rayleigh-Taylor growth rates, clarify the role of the Kelvin-Helmholtz roll-up, explain the short wavelength cutoff, ...
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...
The purpose of this research program is to investigate fluid dynamic instabilities and mixing initiated by the interaction of shock waves with interfaces between light and heavy gases. In particular, the nonlinear stage of shock-initiated Rayleigh-Taylor instability (also known as the Richtmeyer-Meshkov ...
Here is a study about fluid flows (the hydrodynamic part of codes modeling the plasma dynamics) showing great gradients and unsteady flows (Rayleigh-Taylor, Richtmyer-Meshkov). The numerical resolution of these problems needs codes able to simulate the tr...
) T he Rayleigh-Taylor (RT) instability occurs when a heavy fluid lies on top of a light fluid cases Figure 1-- Rayleigh-Taylor mixing of 100,589,840 atoms by molecular dynamics of a heavy fluid (red
This is a report of the progress during the past year of the shock-tube study of the Richtmyer-Meshkov instability, initiated under the sponsorship of the Lawrence Livermore National Laboratory in September, 1982. The purpose of this research program, as stated in the original proposal, is: to investigate the nonlinear processes initiated by shock wave interaction with ...
Results of ablative Rayleigh-Taylor instability growth experiments performed in indirect drive on the OMEGA laser facility [T. R. Boehly, D. L. Brown, S. Craxton et al., Opt. Commun. 133, 495 (1997)] are reported. These experiments aim at benchmarking hydrocodes simulations and ablator ...
An ignition capsule with a nano-crystalline, high density, carbon ablator is emerging as a promising alternative target for NIF. There are four main advantages in using the HDC ablator. First, for a given outer radius, the HDC ablator absorbs more hohlraum-driven x-ray energy than for a beryllium ablator. Second, ...
Germanium-doped CH (CHGe) is the nominal ablator for LMJ target design. To investigate its properties we performed indirect drive experiments on the OMEGA laser facility. On each shot foil motion and modulations growth were simultaneously measured by side-on and face-on radiography, while drive was assessed by measuring radiation escaping hohlraum LEH. This allows to better ...
The Rayleigh-Taylor unstable growth of laser-seeded, 3D broadband perturbations was experimentally measured in the laser-accelerated, planar plastic foils. The first experimental observation showing the self-similar behavior of the bubble size and amplitude distributions under ablative conditions is presented. In the nonlinear regime, the modulation sigma(rms) grows as ...
This progress report contains discussion on the following topics: A high-bandwidth electrical-waveform generator based on aperture-coupled striplines for OMEGA pulse-shaping applications; sweep deflection circuit development using computer-aided circuit design for the OMEGA multichannel streak camera; D-{sup 3}He protons as a diagnostic for target {rho}R; growth rates of the ...
Rayleigh-Taylor instability of a rotating compressible inviscid fluid was investigated. The coriolis force for unstable configuration decreases the critical wavelength of perturbations that give rise to Rayleigh modes, while for stable configurations it increases this critical wavelength. (auth)
Manifestations of both Rayleigh-Taylor instability and Karman vortices in atmospheric flows are recognized, and existing theory is applied to infer some values for the horizontal and vertical eddy transport coefficients for momentum, (K sub h) and (K sub ...
This paper is concerned with the singularities in inviscid two dimensional finite amplitude water waves and inviscid Rayleigh-Taylor instability. For the deep water gravity waves of permanent form, through a combination of analytical and numerical methods...
The feedout process transfers mass perturbations from the rear to the front surface of a driven target, producing the seed for the Rayleigh- Taylor (RT) instability growth. The feedout mechanism is investigated analytically and numerically for the case of...
The model equations described in this paper are able to reproduce the qualitative behavior of the elastic-plastic Rayleigh-Taylor instability response seen in numerical experiments. Both elastic shear modulus and yield strength play important roles in the...
Modeling of the Three- Dimensional Viscous Rayleigh-Taylor Instability Boris J.P. Kaus and Yuri Y-difference/spectral method is used to model the 3D viscous Rayleigh-Taylor instability. Numerically calculated growth rate RAYLEIGH-TAYLOR INSTABILITY 0 0.005 0.01 0.015 0.02 ...
This volume of the LLE Review, covering AprilJune 2003, features Reduction of the Ablative RayleighTaylor Growth Rate with Gaussian Picket Pulses. This article reports on the seminal work to experimentally validate the reduction in the RayleighTaylor (RT)...
Experimental measurements of perturbation growth due to the Rayleigh-Taylor (RT) instability at the ablation interface have been used to try to understand the physical processes involved in ablative stabilization. The growth rate calculated from a dispersion relation and values for the acceleration and ablation ...
Computation of three-dimensional (3-D) Rayleigh--Taylor instability in compressible fluids is performed on a MIMD computer. A second-order TVD scheme is applied with a fully parallelized algorithm to the 3-D Euler equations. The computational program is implemented for a 3-D study of bubble evolution in the Rayleigh--Taylor instability ...
The magnetic Rayleigh-Taylor (RT) instability has been predicted and observed to cause breakup of the plasma sheath in imploding Z-pinches. In this work we show that for the type of density profile encountered in strongly radiating pinches, instability at very short wavelengths grows to the non-linear stage and seeds progressively ...
The Rayleigh-Taylor instability at the interface in an immiscible two-component Bose-Einstein condensate is investigated using the mean field and Bogoliubov theories. Rayleigh-Taylor fingers are found to grow from the interface and mushroom patterns are formed. Quantized vortex rings and vortex lines are then generated around the mushrooms. The ...
A numerical simulation of the nonlinear evolution of the collisional Rayleigh--Taylor instability using a set of equations appropriate for the equatorial F region ionosphere has been performed. The results show that the irregularities produced by the instability grow on the bottomside of the F region peak, as predicted by linear ...
A simplified analytic model is presented to describe the implosion of a plasma column by an azimuthal magnetic field of sufficient magnitude to drive a strong shock wave into the plasma. This model is employed together with buoyancy-drag-based models of nonlinear single-mode and turbulent multimode Rayleigh-Taylor (RT) growth to investigate the mixing process in such fast ...
A simplified analytic model is presented to describe the implosion of a plasma column by an azimuthal magnetic field of sufficient magnitude to drive a strong shock wave into the plasma. This model is employed together with buoyancy-drag-based models of nonlinear single-mode and turbulent multimode Rayleigh-Taylor growth to investigate the mixing process in such fast Z ...
Due to the sensitivity of Rayleigh-Taylor instabilities to initial conditions and due to the difficulty of forming well controlled cylindrical or spherical fluid interfaces, Rayleigh-Taylor experiments are often performed with simple, planar interfaces. Rayleigh-Taylor instability phenomena of practical interest, ...
Beginning from a state of hydrostatic equilibrium, in which a heavy gas rests atop a light gas in a constant gravitational field, Rayleigh-Taylor instability at the interface will launch a shock wave into the upper fluid. The rising bubbles of lighter fluid act like pistons, compressing the heavier fluid ahead of the fronts and generating shocklets. These ...
We study a general multiple layer Rayleigh-Taylor instability problem for both compressible and incompressible inviscid fluids. Our main result is that many features of a multilayer system are universal, in the sense they do not depend on such details as the number of layers, their thicknesses, equations of state for the fluids, and equilibrium density ...
We will present the results of experiments designed to study hydrodynamic instability growth in spherical targets imploded by the 30-kJ OMEGA laser system. Instability growth during the acceleration phase of the implosion can be diagnosed using the burnthrough technique. This method has been shown(D. K. Bradley et al.), Phys. Rev. Lett. 68, 2774 (1992); J. ...
Two superimposed miscible liquids are separated by a diffuse boundary layer providing a steady transition of density. If the heavy fluid is on top of the light one, Rayleigh-Taylor-instabilities develop and cause a rapid interchange and eventually an inte...
The three-dimensional Rayleigh-Taylor (RT) instability was simulated with the Front Tracking code Fron
The use of axially-moving free-pistons to drive rotating liquid liners is described. The advantages of this approach include simple synchronism of piston motion to avoid low frequency Rayleigh-Taylor instability, a great reduction in the number of moving ...
A numerical analysis was carried out on the stability of targets designed to produce fusion energy gains close to 100 when irradiated with an appropriate heavy ion beam. To reach such performances, it was found that a high-Z radiation shield was necessary...
Growth rates of Rayleigh-Taylor modes, particularly those of long wavelength, are reduced at fluid interfaces in inhomogeneous laser-driven targets by the density gradients occurring naturally as a result of the acceleration. Growth rates can be reduced f...
Direct numerical simulation and large eddy simulations are powerful tools for studying turbulent flows. Unfortunately, they are computationally demanding in terms of run times, storage, and accuracy of the numerical method used. In particular, high order ...
The nonlinear evolution of the local collisional Rayleigh-Taylor instability in downward-moving equatorial F layers has been studied in a coordinated theoretical and experimental program dealing with actual conditions of bottomside spread F. For ambient bottomside electron density gradient scale lengths L=8 and 25 km, we find large percentage depletions ...
The evolution of the Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) instabilities in the nonlinear regime of growth was investigated in indirect- drive experiments on the Nova laser. The RT experiments investigated the evolution of both single- and multi...
Recently, attention has focused on the effects of spherical convergence on the nonlinear phase of Rayleigh-Taylor growth. In particular, for instability growth on spherically converging interfaces, modifications to the predictions of the Layzer model for ...
this paper, we will illustrate this program by discussing its implementation in examples drawn from the authors' work and that of collaborators. This work as well as collateral work of others can be traced from the survey articles [2,3] and from [1]. 2 Rayleigh-Taylor Instability
Perturbations on an interface driven by a strong blast wave grow in time due to a combination of Rayleigh-Taylor, Richtmyer-Meshkov, and decompression effects. In this paper, we present the first results from a computational study of such a system under d...
A modification of a boundary-integral method is used to study the single-scale Rayleigh-Taylor instability for arbitrary Atwood number. Smoothing the Green's function using vortex blobs suppresses singularities in the curvature and other modifications are...
The nonlinear evolutions of the Rayleigh-Taylor instability (RTI) with preheat is investigated by numerical simulation (NS). A new phase of the spike deceleration evolution in the nonlinear ablative RTI (ARTI) is discovered. It is found that nonlinear evolution of the RTI can be divided into the weakly nonlinear regime (WNR) and the highly nonlinear regime ...
The goal of the EZturb mix model in KULL is to predict the turbulent mixing process as it evolves from Rayleigh-Taylor, Richtmyer-Meshkov, or Kelvin-Helmholtz instabilities. In this report we focus on a simple example of the Rayleigh-Taylor instability (which occurs when a heavy fluid lies above a light fluid, and we perturb the ...
The theory of the deceleration phase of an imploding ICF capsule is carried out analytically by solving the conservation equations in Lagrangian coordinates inside the hot-spot region. The evolution of the hot-spot mass and temperature are calculated. The hot-spot mass increases in time because of the ablation flow off the shell's inner surface. Such a flow is caused by the ...
Planar burnthrough experiments were performed on OMEGA to relate the onset of the characteristic line emission from a signature layer buried under a plastic ablator to the single-mode Rayleigh-Taylor (RT) instability growth. The single-mode RT growth was measured by observing the modulation in optical depth of laser-driven CH foils ...
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 ...
Single-mode experiments have been conducted on the Nova laser to examine the effect of perturbation shape on ablation front Rayleigh-Taylor growth. The perturbations investigated had the same magnitude wave vector k=(k{sub x}{sup 2}+k{sub y}{sup 2}){sup 1/2} and the same initial amplitude. The shapes corresponded to 2D {lambda}=50 {mu}m, 3D square k{sub ...
Both the efficiency of an implosion and the growth rate of hydrodynamic instability increase with the aspect ratio of an implosion. In order to study the physics of implosions with high Rayleigh-Taylor growth factors, we use doped ablators which should minimize x-ray preheat and shell decompression, and hence increase in-flight aspect ...
This paper is devoted to the study of the deceleration phase of inertial confinement capsules. First the self-similar flow exhibited by Betti et al. [Phys. Plasmas 8, 5257 (2001)] is proved to be an attractor in the sense that arbitrary initial conditions converge towards this solution. The convergence rate depends on the ablation process and heat conductivity and it is shown ...
Convergent geometry Rayleigh-Taylor experiments have been performed with a 122-point detonation initiation system on cylinders having sinusoidal perturbations on the outer surface ranging from mode-6 to mode-36. Experiments were performed with various perturbation mode numbers, perturbation amplitudes, and ring accelerations. Feedthrough perturbation growth on the inner ...
Eight beams carrying a shaped pulse from the NOVA laser were focused into a hohlraum with a total energy of about 25 kJ. A planar foil was placed on the side of the hohlraum with perturbations facing away from the hohlraum. All perturbations were 4 {micro}m in amplitude and 50 {micro}m in wavelength. Three foils of pure aluminum were shot with thicknesses and pulse lengths respectively of 86 ...
Issues with coupling efficiency, beam illumination symmetry, and Rayleigh-Taylor instability are discussed for spherical heavy-ion-beam-driven targets with and without hohlraums. Efficient coupling of heavy-ion beams to compress direct-drive inertial fusion targets without hohlraums is found to require ion range increasing several-fold during the drive pulse. One-dimensional ...
The evolution of the Rayleigh-Taylor (RT) instability at an embedded, or classical, interface is examined in a series of experiments at the Nova laserfacility .[reference for Nova] These experiments focused on the transition from the linear to nonlinear regimes for both single- and multimode initialperturbations. The development of a single mode at the embedded interface is ...
The Richtmyer-Meshkov instability (RMI) at the ablation front of laser-irradiated planar targets is investigated by two-dimensional numerical hydrodynamics simulations. The linear evolution of perturbations seeded either by surface roughness or target inhomogeneity is studied for perturbation wavelengths in the range 10<=?<=400 ?m and laser intensity ...
