Characterization of local energy transfer in large-scale intermittent stratified turbulent flows via coarse-graining

Physical Review Fluids, Journal Year: 2025, Volume and Issue: 10(4)

Published: April 30, 2025

Recent studies based on simulations of the Boussinesq equations indicate that stratified turbulent flows can develop large-scale intermittency in velocity and temperature fields, as detected atmosphere oceans. In particular, emerging powerful vertical drafts were found to generate local turbulence, proving necessary for dissipate energy efficiently homogeneous isotropic flows. The existence regions characterized by enhanced turbulence dissipation, observed, instance, ocean, requires appropriate tools assess how is transferred across scales at same time locally physical space. After refining a classical coarse-graining procedure, here we investigate feedback extreme transfer exchanges subdomains stably geophysical interest. Our analysis shows are indeed able trigger upscale downscale transfers, strengthening coupling between kinetic potential energies certain scales, depending intensity velocity. Published American Physical Society 2025

Language: Английский

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Multi-scale dynamics of scalar transfer in Rayleigh–Taylor turbulent mixing

Journal of Fluid Mechanics, Journal Year: 2025, Volume and Issue: 1011

Published: May 14, 2025

Miscible Rayleigh–Taylor (RT) turbulence exhibits a wide range of length scales in both the velocity and density fields, leading to complex deformations isoscalar surfaces enhanced mixing due nonlinear interactions among different scales. Through high-resolution numerical simulations coarse-graining analysis, we demonstrate that variance heavy fluid concentration, initially maximised by unstable stratification, progressively cascades from larger smaller scales, eventually dissipates at smallest scale. The transfer scalar variance, $\Pi ^Y$ , primarily governed filtered strain rate tensor, is effectively captured model links surface stretching. On other hand, backscatter transfer, represented negative component influenced vorticity field. Furthermore, examine directional anisotropy RT turbulence, enhancing accuracy separating horizontal mean mass fraction its fluctuating part.

Language: Английский

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Bubble re-acceleration behaviours in compressible Rayleigh–Taylor instability with isothermal stratification

Journal of Fluid Mechanics, Journal Year: 2023, Volume and Issue: 954

Published: Jan. 3, 2023

The highly nonlinear evolution of the single-mode stratified compressible Rayleigh–Taylor instability (RTI) is investigated via direct numerical simulation over a range Atwood numbers ( $A_T=0.1$ – $0.9$ ) and Mach $Ma=0.1$ $0.7$ for characterising isothermal background stratification. After potential stage, it found that bubble accelerated to velocity which well above saturation value predicted in flow model. Unlike re-acceleration behaviour quasi-incompressible RTI with uniform density, characteristics are driven by not only vorticity accumulation inside but also compressibility resulting from Specifically, case strong stratification high $A_T$ , dominates characters. To model effect compressibility, we propose novel reliably describe behaviours RTI, introducing dilatation into classical takes account accumulation.

Language: Английский

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Turbulence kinetic energy transfers in direct numerical simulation of shock-wave–turbulence interaction in a compression/expansion ramp

Journal of Fluid Mechanics, Journal Year: 2022, Volume and Issue: 935

Published: Feb. 3, 2022

A direct numerical simulation is performed for a supersonic turbulent boundary layer interacting with compression/expansion ramp at an angle $\alpha =24^{\circ }$ , matching the same operating conditions of by Priebe & Martín ( J. Fluid Mech. vol. 699, 2012, pp. 1–49). The adopted method relies on high-order spectral difference scheme coupled bulk-based, low-dissipative, artificial viscosity shock-capturing purposes (Tonicello et al. Comput. Fluids 197, 2020, 104357). Filtered and averaged fields are evaluated to study total kinetic energy transfers in presence non-negligible compressibility effects. compression motions shown promote forward transfer down cascade, whereas expansion regions more likely experience backscatter energy. standard decomposition subgrid scale tensor deviatoric spherical parts proposed compressible incompressible contributions across scales. On average, correlation between dissipation large-scale dilatation be caused entirely part Reynolds stresses (i.e. energy). other hand, subtracting contribution, mild still noticeable filtered fields. For flows, it seems reasonable assume that eddy-viscosity approximation can suitable model tensor, which exclusively causing cascade average. Instead, complex models needed part, which, even statistical provides important mechanism backscatter.

Language: Английский

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Measuring scale-dependent shape anisotropy by coarse-graining: Application to inhomogeneous Rayleigh-Taylor turbulence

Physical Review Fluids, Journal Year: 2023, Volume and Issue: 8(11)

Published: Nov. 7, 2023

A novel approach is introduced to measure flow anisotropy at all length scales. It valid for general fields, including inhomogeneous flows with complex boundaries where traditional Fourier approaches face difficulties. Application two- and three-dimensional Rayleigh-Taylor turbulence reveals the markedly distinct different scales due differing energy cascade directions.

Language: Английский

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Radiation and heat transport in divergent shock–bubble interactions

Physics of Plasmas, Journal Year: 2024, Volume and Issue: 31(3)

Published: March 1, 2024

Shock–bubble interactions (SBIs) are important across a wide range of physical systems. In inertial confinement fusion, between laser-driven shocks and micro-voids in both ablators foam targets generate instabilities that major obstacle achieving ignition. Experiments imaging the collapse such voids at high energy densities (HED) constrained by spatial temporal resolution, making simulations vital tool understanding these this study, we benchmark several radiation thermal transport models xRAGE hydrodynamic code against experimental images collapsing mesoscale void during passage 300 GPa shock. We also quantitatively examine role physics evolution SBI. This allows us to understand dynamics interaction timescales shorter than framerates. find all examined reproduce empirical shock velocities within error. Radiation is found reduce pressures providing an additional pathway ablation region, but effect small (∼1% total pressure). Employing flux-limited Spitzer model for heat conduction, flux limiters 0.03 0.10 produce agreement with velocities, suggesting system well-within regime. Higher conduction lower temperatures ablated plasma prevent secondary front, resulting weaker primary shocks. Finally, confirm SBI-driven observed HED regime baroclinically driven, as low case.

Language: Английский

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Mixing and inter-scale energy transfer in Richtmyer–Meshkov turbulence

Journal of Fluid Mechanics, Journal Year: 2024, Volume and Issue: 984

Published: April 8, 2024

This work investigates the compressible turbulence induced by Richtmyer–Meshkov (RM) instability using high-resolution Navier–Stokes simulations. Special attention is paid to characteristics of RM including mixing width growth, turbulent kinetic energy (TKE) decay, degree, inhomogeneity and anisotropy. Three distinct initial perturbation spectra are designed at interface reveal condition imprint on turbulence. Results show that cases with large-scale perturbations present a stronger statistical also quicker growth width, whereas small-scale faster TKE greater level, higher isotropy homogeneity. A thorough analysis inter-scale transfer in presented coarse-graining approach exposes two subfilter-scale (SFS) fluxes (i.e. deformation baropycnal work). strong correlation between nonlinear model ( Fluids , 4 (2), 2019) simulation results confirmed for first time, demonstrating its potential modelling Two primary mechanisms (the straining baroclinic generation processes) explored this model. The evolutions SFS exhibit behaviours various filter scales, different flow regions under motions (strain rotation). It found all three share common dynamics, which important

Language: Английский

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Investigation of strong isothermal stratification effects on multi-mode compressible Rayleigh–Taylor instability

Physics of Fluids, Journal Year: 2023, Volume and Issue: 35(8)

Published: Aug. 1, 2023

Rayleigh–Taylor instability, RTI, occurs at the interface separating two fluids subjected to acceleration when density gradient and are in opposite directions. Previous scientific research primarily considered RTI under incompressible assumption, which may not be valid many high-energy-density engineering applications astrophysical phenomena. In this study, compressibility effects of background isothermal stratification strength on multi-mode two-dimensional explored using fully compressible multi-species direct numerical simulations. Cases three different Mach numbers – Ma=0.15, 0.3, 0.45 investigated explore weakly, moderately, strongly stratified respectively, an Atwood number 0.04. Unlike increase flow through can suppress growth lead a termination mixing layer with highly molecularly mixed state. Our findings suggest that even chosen relatively low number, variable-density significantly enhanced due for as spatial profiles become noticeably asymmetric across case. addition, study compares chaotic behavior cases by studying transport turbulent kinetic energy well vortex dynamics. The Reynolds dependence results is also examined numbers, large-scale quantities interest shown universal range studied.

Language: Английский

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Mixing and energy transfer in compressible Rayleigh-Taylor turbulence for initial isothermal stratification

Physical Review Fluids, Journal Year: 2022, Volume and Issue: 7(10)

Published: Oct. 25, 2022

In compressible Rayleigh--Taylor instability, flow compressibility plays an important role in the generation of large-scale kinetic energy, which mainly comes from conversion potential energy for small stratification parameter (Sr) and internal through pressure-dilatation work large Sr. The latter leads to bubble heights increasing rapidly bubbles that are bigger at overall statistics normalized subgrid-scale (SGS) flux is nearly independent Sr, but reverse SGS increases significantly with increase compression motions enhance direct expansion strengthen flux.

Language: Английский

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Wavelet-based wavenumber spectral estimate of eddy kinetic energy: Application to the North Atlantic

Ocean Modelling, Journal Year: 2024, Volume and Issue: 190, P. 102392 - 102392

Published: May 31, 2024

An ensemble of eddy-rich North Atlantic simulations is analyzed, providing estimates eddy kinetic energy (EKE) wavenumber spectra and spectral budgets below the mixed layer where input from surface convection wind stress are negligible. A wavelet transform technique used to estimate a spatially localized 'pseudo-Fourier' spectrum (Uchidaet al., 2023b), permitting comparisons be made between at different locations in highly inhomogeneous anisotropic environment. The EKE tend stable time but dependent. We find evidence Gulf Stream imprint on near field appearing as enhanced levels (nominally) North-South direction relative East-West direction. Surprisingly, this signature anisotropy holds into quiescent interior with tendency orientation aligned maximum being associated shallower slopes elevated inverse cascade. Conversely, angle minimum steeper slope forward cascade EKE. Our results also indicate that vertical motion non-negligibly affects summary conclusion characteristics eddies wind-driven gyre submesoscale dynamics expected weak diverge expectations built inertial-range assumptions, which stationary horizontally isotropic space.

Language: Английский

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