A5103111435- Fluid Dynamics and Turbulent Flows
- Laser-Plasma Interactions and Diagnostics
- Particle physics theoretical and experimental studies
- Quantum Chromodynamics and Particle Interactions
- Computational Fluid Dynamics and Aerodynamics
- High-Energy Particle Collisions Research
- Gas Dynamics and Kinetic Theory
- Combustion and flame dynamics
- Particle Dynamics in Fluid Flows
- Magnetic confinement fusion research
- Wind and Air Flow Studies
- High-pressure geophysics and materials
- Laser-induced spectroscopy and plasma
- Dark Matter and Cosmic Phenomena
- Atomic and Molecular Physics
- Meteorological Phenomena and Simulations
- Atmospheric chemistry and aerosols
- Fusion materials and technologies
- Combustion and Detonation Processes
- Advanced Combustion Engine Technologies
- Parallel Computing and Optimization Techniques
- Theoretical and Computational Physics
- Gamma-ray bursts and supernovae
- Lattice Boltzmann Simulation Studies
- Advanced Numerical Methods in Computational Mathematics
Lawrence Livermore National Laboratory
2009-2024
University of Southampton
2023
University of Bristol
2012-2018
Centro Brasileiro de Pesquisas Físicas
2017
Centre for Process Innovation
2016
Stanford University
2011
Alberta Children's Hospital
2007
University of Calgary
2007
Office of Scientific and Technical Information
2003
National Technical Information Service
2003
A method is presented whereby the fast chemistry reaction, Fuel+(r)Oxidizer →(1+r) Product, may be modeled in context of a large eddy simulation (LES). The model based on presumed form for subgrid-scale probability density function (PDF) conserved scalar. nature statistics discussed and it shown that beta representation PDF appropriate. Data from both laboratory experiments direct numerical simulations (DNS) are used to show predictions very accurate, given exact values filtered scalar its...
A large-eddy simulation technique is described for computing Rayleigh–Taylor instability. The method based on high-wavenumber-preserving subgrid-scale models, combined with high-resolution numerical methods. verified to match linear stability theory and validated against direct data. used simulate instability at a grid resolution of . growth rate found depend the mixing rate. transition observed in flow, during which an inertial range begins form velocity spectrum zone temporarily reduced....
Direct numerical simulations (DNS) are presented of three-dimensional, Rayleigh–Taylor instability (RTI) between two incompressible, miscible fluids, with a 3:1 density ratio. Periodic boundary conditions imposed in the horizontal directions rectangular domain, no-slip top and bottom walls. Solutions obtained for Navier–Stokes equations, augmented by species transport-diffusion equation, various initial perturbations. The DNS achieved outer-scale Reynolds numbers, based on mixing-zone height...
An alternative methodology is described for large-eddy simulation (LES) of flows involving shocks, turbulence, and mixing. In lieu filtering the governing equations, it postulated that large-scale behavior a LES fluid, i.e., fluid with artificial properties, will be similar to real provided properties obey certain constraints. The consist modifications shear viscosity, bulk thermal conductivity, species diffusivity fluid. modified transport coefficients are designed damp out high wavenumber...
The enthalpy diffusion flux in the multicomponent energy equation is a well-known yet frequently neglected term. It accounts for changes associated with compositional resulting from species diffusion. term prevents local violations of entropy condition flows where significant mixing occurs between dissimilar molecular weight. In simulations nonpremixed combustion, omission can lead to anomalous temperature gradients, which may cause regions exceed ignition conditions. also play role...
Achieving ignition in inertial confinement fusion (ICF) requires the formation of a high-temperature ($>$10 keV) central hot spot. Turbulence has been suggested as mechanism for degrading hot-spot conditions by altering transport properties, introducing colder, mixed material, or reducing conversion radially directed kinetic energy to heating. We show, however, that spot is very viscous, and assumption turbulent incorrect. This work presents first high-resolution, three-dimensional...
The turbulence generated in the variable density Rayleigh–Taylor mixing layer is studied using high-Reynolds number fully resolved 30723 numerical simulation of Cabot and Cook (Nature Phys. 2 (2006), pp. 562–568). achieves bulk Reynolds number, Re = H [Hdot]/ν 32,000, turbulent t [ktilde] 2/νϵ 4600, Taylor R λ 170. Atwood A, 0.5, Schmidt Sc, 1. Typical fluctuations, while modest, being one quarter mean density, lead to non-Boussinesq effects. A comprehensive study energy budgets for kinetic...
Ignition capsule designs for the National Facility (NIF) [G. H. Miller, E. I. Moses, and C. R. Wuest, Opt. Eng. 443, 2841 (2004)] have continued to evolve in light of improved physical data inputs, improving simulation techniques, and, most recently, experimental from a growing number NIF sub-ignition experiments. This paper summarizes recent changes cryogenic design some our latest techniques simulating its performance. Specifically, results indicated harder x-ray drive spectra hohlraums...
The spatial structure and energy budget for Rayleigh-Taylor instability are examined using results from a 512 x 2040 point direct numerical simulation. outer-scale Reynolds number of the flow follows rough t(3) power law reaches final value about 5500. Taylor microscales numbers plotted to characterize anisotropy in document progress towards mixing transition. A parameter is defined which characterizes relative rates entrainment flow. spectrum each term kinetic equation plotted, at regular...
The deceleration stage of inertial confinement fusion implosions is modeled in detail using three-dimensional simulations designed to match experiments at the National Ignition Facility. In this final implosion, shocks rebound from center capsule, forming high-temperature, low-density hot spot and slowing incoming fuel. flow field that results process highly influences many aspects implosion. interior capsule has high-velocity motion, but viscous effects limit range scales develop. bulk...
The combined Rayleigh-Taylor/Kelvin-Helmholtz (RT/KH) instability is studied in the early nonlinear regime. Specifically, effect of adding shear to a gravitationally unstable configuration investigated. While linear stability theory predicts that any amount would increase growth rate beyond Rayleigh-Taylor value, numerical (large eddy) simulations show more complex and non-monotonic behavior where small amounts fact decrease rate. A velocity scale for proposed from arguments shown...
Turbulent hydrodynamic mixing induced by the Rayleigh–Taylor (RT) and Richtmyer–Meshkov (RM) instabilities occurs in settings as varied exploding stars (supernovae), inertial confinement fusion (ICF) capsule implosions, macroscopic flows fluid dynamics facilities such shock tubes. Turbulence theory modeling have been applied to RT RM developed into a quantitative description of turbulence from onset asymptotic end-state. The treatment, based on combined approach theory, direct numerical...
The Laser Inertial Fusion Energy (LIFE) concept is being designed to operate as either a pure fusion or hybrid fusion-fission system. present work focuses on the option. A key component of LIFE engine chamber subsystem. It must absorb energy, produce fuel replace that burned in previous targets, and enable both target laser beam transport ignition point. system also mitigate emissions, including ions, x-rays neutrons reset itself operation at 10-15 Hz. Finally, offer high level availability,...
Scale similarity models are discussed for the subgrid-scale stress tensor and variance of a passive scalar in turbulent flow. The modeling involves sampling resolved fields by applying spatial filter at scale greater than grid spacing computational mesh. A method is described determining constant proportionality present each model. model determined such that kinetic energy exact on average. shown to depend size filter, turbulence Reynolds number degree resolution large eddies.
Abstract We derive a growth-rate model for the Richtmyer–Meshkov mixing layer, given arbitrary but known initial conditions. The growth rate is determined by net mass flux through centre plane of perturbed interface immediately after shock passage. correlation between post-shock density and streamwise velocity. field computed from perturbations jump velocity via Biot–Savart integration vorticity field. deposited obtained baroclinic torque with an impulsive acceleration. Using characteristic...
Beginning from a state of hydrostatic equilibrium, in which heavy gas rests atop light constant gravitational field, Rayleigh–Taylor instability at the interface will launch shock wave into upper fluid. We have performed series large-eddy simulations suggest that rising bubbles fluid act like pistons, compressing ahead fronts and generating shocklets. These shocklets coalesce multidimensional fashion strong normal shock, increases strength as it propagates upwards. The demonstrate Mach...
We describe Miranda, a massively parallel spectral/compact solver for variabledensity incompressible flow, including viscosity and species diffusivity effects. Miranda utilizes FFTs band-diagonal matrix solvers to compute spatial derivatives at least 10th-order accuracy. have successfully ported this communicationintensive application BlueGene/L explored both direct block transpose-based parallelization strategies its implicit solvers. discovered mapping strategy which results in virtually...
A subgrid-scale model is discussed for the scalar dissipation rate in nonpremixed turbulent reacting flows. The contains a coefficient which determined by assuming form energy spectrum. tested priori using Direct Numerical Simulation (DNS) results temporal mixing layer. estimated rates are good agreement with computed directly from DNS data. Furthermore, assumed spectrum methodology found to accurately predict coefficient, including its spatial and variations.