revtex, 31 pages in English, after "\end{document}" of english part of tex-file original russian text is added; now we use more accurate definition of the temperature, Enskog mistake is considered in more details
In the article, correct method for the kinetic Boltzmann equation asymptotic solution is formulated, the Hilbert method and the Enskog error are considered. The equations system of multi-component nonequilibrium gas-dynamics is derived, that corresponds to the first order in the approximate method for solution of the kinetic Boltzmann equation within the Struminskii approach. It is shown, that velocity distribution functions, received by the proposed method and by the Enskog method within the Enskog approach to solving of kinetic Boltzmann equation for gas mixture, are equivalent to first infinitesimal order terms, but, generally speaking, differ in the next order. An interpretation of turbulent gas flow is proposed, as stratified to components gas flow, which is described by the derived equations system of multi-component nonequilibrium gas-dynamics.
Two mechanisms are considered responsible for the turbulence modification due to suspended particles in a turbulent gas-particle suspension. Turbulence augmentation is due to the enhancement of fluctuations by wakes behind particles, whereas turbulence attenuation is considered to result from the increased dissipation due to the particle drag. In order to examine the turbulence attenuation mechanism, Direct Numerical Simulations (DNS) of a particle-gas suspension are carried out at a Reynolds number of about 3333 based on the average gas velocity $\bar{u}$, channel width $h$, and the gas kinem…
Theory and computations have established that thermodynamic gradients created by hot spots in reactive gas mixtures can lead to spontaneous detonation initiation. However, the current laminar theory of the temperature-gradient mechanism for detonation initiation is restricted to idealized physical configurations. Thus, it only predicts conditions for the onset of detonations in quiescent gases, where an isolated hot spot is formed on a timescale shorter than the chemical and acoustic timescales of the gas. In this work, we extend the laminar temperature-gradient mechanism into a statistical mo…
In our recent works we proposed a theory of turbulence in inertial gas flow via the mean field effect of an intermolecular potential. We found that, in inertial flow, turbulence indeed spontaneously develops from a laminar initial condition, just as observed in nature and experiments. However, we also found that density and temperature in our inertial flow model behave unrealistically. The goal of the current work is to demonstrate technical possibility of modeling compressible, turbulent flow at low Mach number where both density and temperature behave in a more realistic fashion. Here we foc…
In recent works we developed a model of balanced gas flow where the momentum equation possesses an additional mean field forcing term, which originates from the hard sphere interaction potential between the gas particles. We demonstrated that, in our model, a turbulent gas flow with a Kolmogorov kinetic energy spectrum develops from an otherwise laminar initial jet. In the current work, we investigate the possibility of a similar turbulent flow developing in a large scale two-dimensional setting, where a strong external acceleration compresses the gas into a relatively thin slab along the thir…
We present Direct Numerical Simulation (DNS) of heavy inertial particles (dust) immersed in two-dimensional turbulent flow (gas). The dust are modeled as mono-dispersed heavy particles capable of modifying the flow through two-way coupling. By varying the Stokes number (St) and the mass-loading parameter $(ϕ_{\rm m})$, we study the clustering phenomenon and the gas phase kinetic energy spectra. We find that the dust-dust correlation dimension $(d_2)$ also depends on $ϕ_{\rm m}$. In particular, clustering decreases as mass-loading $(ϕ_{\rm m})$, is increased. In the kinetic energy spectra of ga…
Results of direct numerical simulations and laboratory experiments have been used in order to show that the buoyancy driven bubbly flows at high gas volume fraction are mixed by deterministic chaos with typical exponential spectrum of the liquid kinetic energy, whereas at moderate and small gas volume fraction it is a distributed chaos (turbulence or pseudo-turbulence) dominated by the third and second moments of helicity distribution with the stretched exponential spectra of the kinetic energy. Interaction of the bubbles with isotropic (behind an active grid) and near-wall turbulent flows has…
The bubble size distribution below a breaking wave is of paramount interest when quantifying mass exchanges between the atmosphere and oceans. Mass fluxes at the interface are driven by bubbles that are small compared to the Hinze scale $d_h$, the critical size below which bubbles are stable, even though individually these are negligible in volume. Combining experimental and numerical approaches, we report a power law scaling 3/2 of the diameter of small bubble size distribution, for sufficiently large separation of scales between the injection size and the Hinze scale. From an analysis of ind…
This work describes an experimental investigation on the mixing induced by a swarm of high Reynolds number air bubbles rising through a nearly homogeneous and isotropic turbulent flow. The gas volume fraction $α$ and the velocity fluctuations $u'_0$ of the carrier flow before bubble injection are varied, respectively, in the ranges $0\leq α\leq 0.93\%$ and 2.3 cm/s $\leq u'_0 \leq 5.5$ cm/s, resulting in a variation of the bubblance parameter $b$ in the range [0, 1.3] ($b = \frac{V_r^2 α}{{u'}_0^2}$, where $V_r$ is the relative rising velocity). Mixing in the horizontal direction can be modell…
In this paper, we intend to address the high-order gas-kinetic scheme (HGKS) in the direct numerical simulation (DNS) of compressible isotropic turbulence up to the supersonic regime. With the consideration of robustness and accuracy, the WENO-Z scheme is adopted for spatial reconstruction in the current higher-order scheme. Statistical quantities are compared with the high-order compact finite difference scheme to determine the spatial and temporal criterion for DNS. According to the grid and time convergence study, it can be concluded that the minimum spatial resolution parameter $κ_{max} η_…
Nonthermal fixed points, vortex statistics, and superfluid turbulence in an ultracold Bose gas
在二维和三维空间中分析了远离热平衡的稀薄简并玻色气体动力学的非热不动点。详细研究了以前在非微扰量子场论方法中发现的、最近被证明与涡旋动力学和超流湍流有关的普适幂律分布[Phys. Rev. B 84，020506（R）（2011）]。结果意味着解释的标度行为的独立涡激发的超流体和拓扑激发的统计可以描述的波动湍流的框架。发现在单粒子动量分布中观察到的特定标度指数与不可逆性以及波相互作用所遵守的守恒定律是一致的。此外，长波长的声学激励的涡旋轴承冷凝物，驱动的涡旋湮灭，发现遵循非热幂律。在统计模式中考虑涡的相关性，长时间偏离非热不动点与涡-反涡配对有关。所研究的非热不动点可在冷气体实验中得到。这些结果揭示了超流湍流的基本方面，并对相关现象具有很强的潜在影响，例如，在早期宇宙膨胀或夸克-胶子等离子体动力学中。
In recent years, coupled with traditional turbulence models, the second-order gas-kinetic scheme (GKS) has been used in the turbulent flow simulations. At the same time, high-order GKS has been developed, such as the two-stage fourth-order scheme (S2O4) GKS, and used for laminar flow calculations. In this paper, targeting on the high-Reynolds number engineering turbulent flows, an implicit high-order GKS with Lower-Upper Symmetric Gauss-Seidel (LU-SGS) technique is developed under the S2O4 framework. Based on Vreman-type LES model and $k - ω$ SST model, a turbulent relaxation time is obtained …
Supernova explosions, active galactic nuclei jets, galaxy--galaxy interactions and cluster mergers can drive turbulence in the circumgalactic medium (CGM) and in the intracluster medium (ICM). However, the exact nature of turbulence forced by these sources and its impact on the different statistical properties of the CGM/ICM and their global thermodynamics is still unclear. To investigate the effects of different types of forcing, we conduct high resolution ($1008^3$ resolution elements) idealised hydrodynamic simulations with purely solenoidal (divergence-free) forcing, purely compressive (cu…
We develop a tractable interaction model for a polyatomic gas, whose kinetic equation combines a Vlasov-type mean field forcing due to an intermolecular potential, and a Boltzmann-type collision integral due to rotational interactions. We construct a velocity moment hierarchy for the new kinetic equation, and find that, under the high Reynolds number condition, the pressure equation becomes decoupled from the angular momentum and stress. For the heat flux, we propose a novel closure by prescribing the specific heat capacity of the gas flow. Setting the specific heat capacity to that of a const…
A new Jeans resolution criterion for (M)HD simulations of self-gravitating gas: Application to magnetic field amplification by gravity-driven turbulence
We develop the theory of weak wave turbulence in systems described by the Schrödinger-Helmholtz equations in two and three dimensions. This model contains as limits both the familiar cubic nonlinear Schrödinger equation, and the Schrödinger-Newton equations. The latter, in three dimensions, are a nonrelativistic model of fuzzy dark matter which has a nonlocal gravitational self-potential, and in two dimensions they describe nonlocal nonlinear optics in the paraxial approximation. We show that in the weakly nonlinear limit the Schrödinger-Helmholtz equations have a simultaneous inverse cascade …
The mean state of the atmosphere and ocean is set through a balance between external forcing (winds, radiation, heat and freshwater fluxes) and the emergent turbulence, which transfers energy to dissipative structures. The forcing gives rise to jets in the atmosphere and currents in the ocean, which spontaneously develop turbulent eddies through the baroclinic instability. A critical step in the development of a theory of climate is to properly include the resulting eddy-induced turbulent transport of properties like heat, moisture, and carbon. The baroclinic instability generates flow structu…
Kolmogorov turbulence across multi-fractal gas in Polaris Flare
Shanghai Astronomical Observatory, Chinese Academy of Sciences（中国科学院上海天文台）；Leiden Observatory, Leiden University（莱顿大学莱顿天文台）；School of Physics and Astronomy, Shanghai Jiao Tong University（上海交通大学物理与天文学院）
