Direct numerical simulations of three-component Rayleigh–Taylor mixing and an improved model for multicomponent reacting mixtures

Journal of Fluid Mechanics, Journal Year: 2024, Volume and Issue: 999

Published: Nov. 21, 2024

We present direct numerical simulations of a three-layer Rayleigh–Taylor instability (RTI) problem with configuration based on the experiments Suchandra & Ranjan ( J. Fluid Mech. , vol. 974, 2023, A35) and Jacobs Dalziel 542, 2005, pp. 251–279). The consists layer light fluid between two layers heavy an Atwood number 0.3. These are first validated through comparison available experimental data. then utilized to analyse statistics in this three-component flow. First, length scales examined utilizing spectra two-point spatial correlations velocity species concentration fluctuations. Next, joint probability density functions (p.d.f.s) compared against several model p.d.f.s representing generalizations bivariate beta distribution. Notably, do not appear be accurately described by Dirichlet distribution, indicating marginal distributions conform Finally, similarity mixing found inertial confinement fusion (ICF) applications is exploited develop validate improved for impact multicomponent thermonuclear (TN) reaction rates. A single time instant from chosen TN burn calculation under hypothetical assumption ICF materials temperatures. Total output second prediction model. new predict rates both premixed non-premixed configurations.

Language: Английский

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Lagrangian investigation of the interface dynamics in single-mode Rayleigh–Taylor instability

Physics of Fluids, Journal Year: 2023, Volume and Issue: 35(10)

Published: Oct. 1, 2023

We apply Lagrangian particle tracking to the two-dimensional single-mode Rayleigh–Taylor (RT) instability study dynamical evolution of fluid interface. At onset nonlinear RT stage, we select three ensembles tracer particles located at bubble tip, spike and inside spiral mushroom structure, which cover most interfacial region as develops. Conditional statistics performed on sets over different stages, such trajectory curvature, velocity, acceleration, reveals temporal spatial flow patterns characterizing growth. The probability density functions velocity curvature exhibit scalings compatible with local topology, swirling motion particles. Large-scale anisotropy flows, measured by ratio horizontal vertical kinetic energy, also varies for arising from differing acceleration. In addition, provide direct evidence connect re-acceleration its interaction transported side, due shear driven Kelvin–Helmholtz instability. Furthermore, reveal that secondary spiral, destabilizes spiraling induces complex structures, is generated centrifugal

Language: Английский

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Large-eddy simulations of compressible Rayleigh–Taylor turbulence with miscible fluids using spatial gradient model

Physics of Fluids, Journal Year: 2023, Volume and Issue: 35(10)

Published: Oct. 1, 2023

Large-eddy simulations (LES) and implicit LES (ILES) of three-dimensional compressible Rayleigh–Taylor turbulence with miscible fluids are performed compared direct numerical simulation (DNS) at the Atwood number At=0.5 stratification parameters Sr = 1.0 4.0. Three sub-grid-scale (SGS) models including constant-coefficient spatial gradient model (CSGM), dynamic Smagorinsky (DSM), mixed (DMM) considered. The CSGM achieves a high accuracy by using velocity gradients neighboring grids. priori tests show that has significantly higher correlation coefficients lower relative errors than traditional SGS models. In posteriori tests, probability density functions terms predicted consistent filtered DNS results. can accurately predict small bubble spike structures, resulting in good predictions mixing heights concentration fields. instantaneous spectra, statistics vorticity fields also examined, showing excellent performance to ILES, DSM, DMM Moreover, temperature pressure better ILES.

Language: Английский

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Particle acceleration by magnetic Rayleigh-Taylor instability: mechanism for flares in black-hole accretion flows

arXiv (Cornell University), Journal Year: 2023, Volume and Issue: unknown

Published: Jan. 1, 2023

We study the magnetic Rayleigh-Taylor instability in relativistic collisionless plasma, as an astrophysical process for nonthermal particle acceleration. consider dense plasma on top of a highly magnetized cavity with sheared field. Using particle-in-cell simulations, we show that small plumes grow and merge progressively to form large-scale plume, which broadens drive rapid reconnection cavity. find this leads efficient acceleration capable explaining flares from inner accretion flow onto black hole Sgr A*.

Language: Английский

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Energy transfer and scale dynamics in 2D and 3D laser-driven jets

Physics of Plasmas, Journal Year: 2023, Volume and Issue: 30(9)

Published: Sept. 1, 2023

We demonstrate a methodology for diagnosing the multiscale dynamics and energy transfer in complex HED flows with realistic driving boundary conditions. The approach separates incompressible, compressible, baropycnal contributions to scale-transfer quantifies direction of these transfers (generalized) wavenumber space. use this compare kinetic (KE) across scales simulations 2D axisymmetric vs fully 3D laser-driven plasma jets. Using FLASH code, we model turbulent jet ablated from an aluminum cone target configuration outlined by Liao et al. [Phys. Plasmas, 26 032306 (2019)]. show that, addition its well known bias underestimating hydrodynamic instability growth, modeling suffers significant spurious energization bulk flow upscale cascade. In 2D, arises as vorticity strain instabilities near jet's leading edge KE upscale, sustaining coherent circulation that helps propel farther (≈25% 3.5 ns) keep it collimated. 3D, are absent. presented here may also help inter-model comparison validation, including future efforts alleviate some artifacts highlighted study.

Language: Английский

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