The Lagrangian picture of heat transfer in convective turbulence
Maik Boltes, Herwig Zilken, Joerg Schumacher
我们提出了一个流体动力学的视频，说明了拉格朗日方面的局部热传递在湍流瑞利-贝纳德对流。数据是从直接数值模拟中获得的。
We present a fluid dynamics video which illustrates the Lagrangian aspects of local heat transfer in turbulent Rayleigh-Benard convection. The data are obtained from a direct numerical simulation.
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Experimental study of turbulent thermal diffusion of particles in an inhomogeneous forced convective turbulence
本研究通过实验探究振荡网格驱动的非均匀对流湍流中微米颗粒的湍流热扩散现象，对比稳定分层湍流的相关结果，验证了颗粒在低温区聚集的效应及有效扩散系数，结果符合理论预测。
Bifurcations of blowup in inviscid shell models of convective turbulence
我们分析了对流湍流的无粘壳模型中的爆破（有限时间奇异性）。我们证明了在壳模型参数变化的情况下，爆破是存在的，并且其内部结构经历了一系列的分岔。各种爆破结构的观察和解释，从自相似的周期，准周期和混沌制度。虽然爆破采取复杂的形式，其渐近小尺度结构是独立的初始条件，即，普遍的。最后，我们讨论了所获得的结果的影响，在无粘流的爆破和湍流理论的公开问题。
Critical Fluctuation of Wind Reversals in Convective Turbulence
对流湍流中风向的不规则逆转被发现有波动的时间间隔，可以与临界行为。结果表明，净磁化强度的二维伊辛晶格的有限大小的波动以同样的方式。风逆转时间序列的去趋势波动分析结果的缩放行为，同意与伊辛问题。发现的性质表明，风逆转现象表现出自组织临界性的迹象。
The characterization of heat and momentum fluxes in wall-bounded turbulence is of paramount importance for a plethora of applications, ranging from engineering to Earth sciences. However, how the turbulent structures associated with velocity and temperature fluctuations interact to produce the emergent flux signatures, is not evident till date. In this work, we investigate this fundamental issue by studying the switching patterns of intermittently occurring turbulent fluctuations from one state to another, a phenomenon called persistence. We discover that the persistence patterns for heat and …
Convective turbulence in a Rayleigh-Benard system with and without rotation in the infinite Prandtl number limit
Rayleigh Benard系统中的对流湍流在能量谱或熵谱中表现出明显的不情愿。最近的Pandey，Verma和Mishra的数值模拟显示了在无限普朗特数极限下标度的明显更好的证据。这促使我们分析地看待这个极限。我们发现，不可避免的存在清扫有助于给一个很好的理解的结果Pandey等。在存在旋转的情况下，在最近的实验和模拟中，在有限的普朗特数下，Nusselt数的瑞利数依赖性显示出斜率的强烈增加。在无限普朗特数的情况下，我们发现，这种陡峭不会发生任何转速和我们的结果满足Doering-Constantin界。
Lagrangian dispersion and heat transport in convective turbulence
基于三维直接数值模拟，对湍流Rayleigh-Benard对流中的局部温度混合和热输运进行了拉格朗日研究。与垂直对距离相反，横向对距离的时间增长符合理查森定律，但由于羽流中的相关对运动，产生较小的理查森常数。因此，我们的研究结果意味着理查森色散也被发现在各向异性湍流。我们发现，非常大的垂直加速度出现频率低于横向的，并没有连接到上升或下降的热羽流。高度相关的联合拉格朗日统计的垂直加速度和局部热传递，使我们能够确定一个区域，这是由热羽混合为主。
The minimal seed for transition to convective turbulence in heated pipe flow
本研究通过DNS和非线性非模态稳定性分析，发现加热管道流中浮力抑制湍流，最小种子随浮力数C增大而变薄，临界能量增加，并揭示对流湍流维持的三个典型过程。
Modelling the transition from shear-driven turbulence to convective turbulence in a vertical heated pipe
本研究针对加热管道流中浮力引发的流动间歇性问题，构建时变背景轴向温度梯度模型，通过DNS探究不同管长与边界条件下的流动转变规律，证实局部剪切湍流衰减的无记忆特性及对流湍流的触发机制。
The vectoral wind structure of daytime atmospheric boundary layer (ABL) turbulence is strongly dependent on the balance between shear-driven turbulence production of horizontal fluctuations (driven by winds at the mesoscale), and buoyancy-driven turbulence production of vertical velocity fluctuations (driven by solar heating), characterized by the global instability state parameter $-z_i/L > 0$. In the fully shear-driven neutral limit $-z_i/L \rightarrow 0$, the surface layer is dominated by coherent streamwise-elongated concentrations of negative streamwise fluctuating velocity (low-speed str…
Dynamics of diffusive-convective staircases in the ocean
本文综述扩散-对流阶梯理论，分析层合并与界面分裂机制及背景湍流影响，指出弱湍流下阶梯可维持而强湍流下被破坏，并强调小尺度过程与大尺度相干性关联的挑战。
Large-scale intermittency is a widely observed phenomenon in convective surface layer turbulence that induces non-Gaussian temperature statistics, while such signature is not observed for velocity signals. Although approaches based on probability density functions have been used so far, those are not able to explain to what extent the signals' temporal structure impacts the statistical characteristics of the velocity and temperature fluctuations. To tackle this issue, a visibility network analysis is carried out on a field-experimental dataset from a convective atmospheric surface layer flow. …
A Shell Model for Buoyancy-Driven Turbulence
本文提出了一个适用于稳定层结和对流湍流的统一壳模型。对稳定分层流的数值模拟表明，该模型的动能谱按$k^{-11/5}$形式变化，符合Bolgiano-Obukhbov标度。我们还观察到一个双缩放（$k^{-11/5}$和$k^{-5/3}$）的参数范围有限。对流湍流的壳模型产生Kolmogorov谱。这些结果与浮力引起的能量通量和能量供给是一致的，并且与Kumar { \em et al.} [Phys. Rev. E { \bf 90}，023016（2014）]。
We perform experimental study of turbulent transport of nanoparticles in convective turbulence with the Rayleigh number $\sim 10^8$ in the air flow. We measure temperature field in many locations by a temperature probe equipped with 11 E-thermocouples. Nanoparticles of the size $\sim 70$ nm in diameter are produced by Advanced Electrospray Aerosol Generator. To determine the number density of nanoparticles, we use Condensation Particle Counter. We demonstrate that the joint action of turbulent effects (which are important in the core flow) and molecular effects (which are essential near the bo…
Nonstandard picture of turbulence(the second revised)
本文给出了湍流场的非标准图象。用非标准数学的概念描述了湍流的层次结构，揭示了湍流场中出现涨落的机理。指出了测量的不确定度。给出了湍流的基本方程。在这幅图中，可以获得合理的闭合方法，并且看起来是精确的，这是很自然的。
The energy- and flux budget theory for surface layers in atmospheric convective and stably stratified turbulence
本研究基于布辛涅斯克近似建立大气对流与稳定分层近地面层的EFB湍流闭合理论，揭示近地面层上下部湍流产生机制的差异，推导了可用于建模的多类湍流特征量垂直廓线的理论关系。
Direct numerical simulations have been performed for turbulent thermal convection between horizontal no-slip, permeable walls with a distance $H$ and a constant temperature difference $ΔT$ at the Rayleigh number $Ra=3\times10^{3}-10^{10}$. On the no-slip wall surfaces $z=0$, $H$ the wall-normal (vertical) transpiration velocity is assumed to be proportional to the local pressure fluctuation, i.e. $w=-βp'/ρ, +βp'/ρ$ (Jiménez et al., J. Fluid Mech., vol. 442, 2001, pp. 89-117), and the property of the permeable wall is given by the permeability parameter $βU$ normalised with the buoyancy-induced…
Laminar and turbulence forced heat transfer convection correlations inside tubes. A review
本文综述了管内层流和湍流强制对流传热关联式，系统评估了公开文献中实验与计算研究的既有及最新成果，涵盖不同管形与纳米流体建模，旨在优化热设计并提升性能。
Multi-range fractional model for convective atmospheric surface-layer turbulence
提出多范围分数（MRF）模型捕捉受多种效应影响的多自相似范围湍流谱，利用青土湖高雷诺数观测数据验证，更新了多点Monin-Obukhov理论量化，并提出了流向速度方差垂直依赖关系新表达式，为湍流数据分析与合成生成提供新方法。
Plumes in a convective flow are considered to be relevant to the turbulent transport in convection. The effective mass, momentum, and heat transports in the convective turbulence are investigated in the framework of time--space double averaging procedure, where a field quantity is decomposed into three parts: the spatiotemporal mean (spatial average of the time-averaged) field, the dispersion or coherent fluctuation, and the random or incoherent fluctuation. With this framework, turbulent correlations in the mean-field equations are divided into the dispersion/coherent and random/incoherent co…
The orientational dynamics of inertialess anisotropic particles transported by two-dimensional convective turbulent flows display a coexistence of regular and chaotic features. We numerically demonstrate that very elongated particles (rods) align preferentially with the direction of the fluid flow, i.e., horizontally close to the isothermal walls and dominantly vertically in the bulk. This behaviour is due to the the presence of a persistent large scale circulation flow structure, which induces strong shear at wall boundaries and in up/down-welling regions. The near-wall horizontal alignment o…
Many geophysical and astrophysical phenomena are driven by turbulent fluid dynamics, containing behaviors separated by tens of orders of magnitude in scale. While direct simulations have made large strides toward understanding geophysical systems, such models still inhabit modest ranges of the governing parameters that are difficult to extrapolate to planetary settings. The canonical problem of rotating Rayleigh-Bénard convection provides an alternate approach - isolating the fundamental physics in a reduced setting. Theoretical studies and asymptotically-reduced simulations in rotating convec…
Thermal plumes are the energy containing eddy motions that carry heat and momentum in a convective boundary layer. The detailed understanding of their structure is of fundamental interest for a range of applications, from wall-bounded engineering flows to quantifying surface-atmosphere flux exchanges. We address the aspect of Reynolds stress anisotropy associated with the intermittent nature of heat transport in thermal plumes by performing an invariant analysis of the Reynolds stress tensor in an unstable atmospheric surface layer flow, using a field-experimental dataset. Given the intermitte…
Studying the atmospheric Planetary Boundary Layer (PBL) is crucial to understand the climate of a planet. The meteorological measurements by the instruments onboard InSight at a latitude of 4.5$^{\circ}$N make a uniquely rich dataset to study the active turbulent dynamics of the daytime PBL on Mars. Here we use the high-sensitivity continuous pressure, wind, temperature measurements in the first 400 sols of InSight operations (from northern late winter to midsummer) to analyze wind gusts, convective cells and vortices in Mars' daytime PBL. We compare InSight measurements to turbulence-resolvin…
Lagrangian studies in convective turbulence
我们提出了高分辨率的直接数值模拟湍流三维瑞利-贝纳德对流的拉格朗日性质的流动的重点。该体积是一个笛卡尔板，纵横比为4，由顶部和底部的自由滑动平面和周期性的侧壁界定。湍流在垂直方向上是不均匀的。这体现在不同的横向和垂直的两个粒子的分散和分散的初始示踪剂的位置上的短期和中期的依赖性。类似于均匀各向同性湍流，色散特性取决于另外的初始对分离，并产生一个短程Richardson样的缩放制度的初始分离接近Kolmogorov耗散长度的两粒子色散。Richardson常数大约是均匀各向同性湍流值的一半。多粒子统计非常接近均匀各向同性的情况。四个拉格朗日示踪剂的集群显示出明显的趋势，形成平坦的，几乎共面的对象在长时间限制和偏离高斯预测。已经采取了重大的努力，以解决正确的四阶加速度分量的统计。我们发现，垂直加速度比横向的间歇性少。垂直加速度与当地对流和传导热通量的联合统计表明，上升和下降的热羽流与最大的加速度幅度无关。事实证明，在拉格朗日框架中计算的努塞尔数在时间上缓慢地收敛到标准欧拉数。
Scale-invariance and characteristic length scale for the large-scale vortices in geostrophic convective turbulence with friction
通过直接数值模拟研究线性摩擦对旋转瑞利-贝纳德对流中大尺度涡旋尺寸的影响，发现涡旋半径遵循R_LSV~α^{-1/2}，并揭示其源于正压模态的k^{-3}能谱及非局域逆能量传递机制。
Large-scale circulations in a shear-free convective turbulence: Mean-field simulations
本研究通过无剪切对流的平均场数值模拟，验证了非均匀大尺度流动对湍流通量的修正作用，揭示了其在大尺度半组织化对流胞形成中的关键机制及相关参数影响规律。
Time-dependent Turbulence in Stars
壳体氧燃烧的三维（3D）流体动力学模拟（Meakin和Arnett 2007）显示出湍流动能的突发性、周期性波动。这些被证明是由于在对流区的全球不稳定性，这已被抑制在计算恒星演化使用混合长度理论（MLT）。Lorenz（1963）的对流卷（细胞）模型中也出现了类似的量子行为，该模型具有奇异吸引子，会引起时间上的随机波动。Lorenz模型的扩展，包括Kolmogorov阻尼和核燃烧，显示出与3D模拟中看到的一样的突发性周期性波动。一个简单的对流层模型（由多个洛伦兹胞组成）给出了亮度波动，这暗示着不规则变量（红巨星和超巨星，Schwarzschild 1975）。Arnett、Meakin和Young（2009）与Nordlund、Stein和Asplund（2009）关于对流驱动性质的明显不一致已经得到解决，并进行了讨论。
Fine-scale statistics of temperature and its derivatives in convective turbulence
本文研究了湍流Rayleigh-Benard对流中温度及其导数的细尺度统计。直接数值模拟是在一个圆柱形单元中进行的，该单元具有单位的长宽比，填充有流体，当瑞利数在10^7和10^9之间时，普朗特数等于0.7。发现温度或其波动的概率密度函数总是非高斯的。从高斯分布的不对称性和强度的偏差被量化为细胞高度的函数。从局部各向同性的温度波动的偏差，作为测量的倾斜度的垂直导数的温度波动，减少在散装，但增加的热边界层的瑞利数，分别。与被动标量混合类似，热耗散率的概率密度函数明显偏离对数正态分布。分布拟合良好的拉伸指数形式。随着Rayleigh数的增加，尾部变得更加延伸，这显示了体积和热边界层的热耗散场的小尺度不稳定性的增加程度。我们发现，由于温度波动的热耗散率不仅占主导地位的对流单体的体积，但也产生了显着的贡献，总的热耗散的热边界层。这与标度理论中使用的近似相反，并且可以解释总热耗散率相对于瑞利数的标度的差异。
Experimental study of turbulent thermal diffusion of inertial particles in a convective turbulence forced by oscillating grids
通过振荡网格强迫对流湍流实验，研究惯性固体颗粒的湍流热扩散现象，发现有效漂移速度与理论预测一致，且惯性颗粒（直径10 μm）的漂移速度是非惯性颗粒（0.7 μm）的1.5-2.5倍。
Geostrophic convective turbulence: The effect of boundary layers
Rayleigh-Bénard（RB）对流，从下面加热和从上面冷却的流体层中的流动，被用来分析热对流向地转制度的转变。在地转制度，这是直接相关的大多数地球和天体物理流动，系统强烈旋转，同时保持足够大的热驱动产生湍流。我们直接模拟了两个热强迫值$Ra=10^{10}$和$Ra=5\cdot10^{10}$的Navier-Stokes方程，普朗特数$Pr=1$为常数，Ekman数在$Ek=1.3\cdot10^{-7}$到$Ek=2\cdot10^{-6}$范围内变化，满足了超临界和强旋转的要求。重点讨论了无滑移边界条件与无应力边界条件在水平板上应用的差异。对于两种边界条件，在大致相同的参数值处发现过渡，即对于~ $Ra=1\times 10^{10}$在~ $Ek\approx 9\times 10^{-7}$处，对于~ $Ra=5\times 10^{10}$在~ $Ek\approx 3\times 10^{-7}$处。然而，过渡是渐进的，并且对于不同的流量指示器，其在~ $Ek$中并不完全一致。特别是，我们报告的传热标度律，边界层的厚度，散逸的体积/边界层分布和平均温度梯度在散装的过渡的特性。对于无滑移和无应力的板块，地转区的流动现象演化是不同的。在无应力条件下，一个大尺度正压涡旋的形成和相应的逆能量级联是明显的。对于无滑移板，没有大规模的相干结构的湍流状态被发现，没有大规模的…
A closure theory is developed for inhomogeneous turbulent flow, which enables a systematic derivation of the turbulence constitutive relations without relying on any empirical parameters. Renormalized-perturbation approximation is performed in the convective coordinate frame based on the mean flow, successfully incorporating the convective integration in generally covariant manner.
Formation and evolution of turbulence in convectively unstable internal solitary waves of depression shoaling over gentle slopes in the South China Sea
研究南海低斜坡上下沉内孤立波的形成与演变，揭示了对流与剪切不稳定性相互作用及湍流发展过程。
Horizontally extended turbulent convection, termed mesoscale convection in natural systems, remains a challenge to investigate in both experiments and simulations. This is particularly so for very low molecular Prandtl numbers as in stellar convection and in Earth's outer core. The present study reports three-dimensional direct numerical simulations of turbulent Rayleigh-Bénard convection in square boxes of side length $L$ and height $H$ with the aspect ratio $Γ=L/H$ of 25, for Prandtl numbers that span almost 4 orders of magnitude, $10^{-3}\le Pr \le 7$, and Rayleigh numbers $10^5 \le Ra \le …
Finite Vertical Windows: Seeing Only Part of the Picture in Rotating Turbulence
研究通过高分辨率测量快速旋转流体中的三维湍流，发现湍流中二维和三维成分在不同频率范围主导，这一分离依赖于测量的垂直跨度，挑战了纯二维流体概念在旋转湍流理论中的使用。
Persistence is defined as the probability that the local value of a fluctuating field remains at a particular state for a certain amount of time, before being switched to another state. The concept of persistence has been found to have many diverse practical applications, ranging from non-equilibrium statistical mechanics to financial dynamics to distribution of time scales in turbulent flows and many more. In this study, we carry out a detailed analysis of the statistical characteristics of the persistence probability density functions (PDFs) of velocity and temperature fluctuations in the su…
Recently, the nature of viscoelastic drag-reducing turbulence (DRT), especially maximum drag reduction (MDR) state, has become a focus of controversy. It has long been regarded as polymers-modulated inertial turbulence (IT), but is challenged by the newly proposed concept of elasto-inertial turbulence (EIT). This study is to re-picture DRT in parallel plane channels by introducing dynamics of EIT based on statistical and budget analysis for a series of flow regimes from the onset of DR to EIT. Energy conversion between velocity fluctuations and polymers as well as polymeric pressure redistribu…
Rotating convective turbulence in moderate to high Prandtl number fluids
针对高普朗特数旋转对流研究不足的问题，开展多Pr值旋转对流实验，发现斜压扭矩平衡的普适性及湍流尺度特征，建立可推广至地球物理场景的流速标度关系。
Angular dynamics of a small particle in turbulence
我们计算了一个中性浮力近球形粒子浸没在不稳定流体的角动力学。我们假设粒子是小的，它的平移滑移速度可以忽略不计，非定常和对流惯性是小扰动。我们推导出一个近似的扭矩的粒子，确定第一惯性修正杰弗里的方程。这些修正是由于局部涡拉伸而产生的，并且在局部涡拉伸很强并且与湍流的不可逆性密切相关的湍流中可能很大。
Large-scale semi-organized rolls in a sheared convective turbulence: Mean-field simulations
本研究基于非旋转湍流对流平均场理论开展剪切对流平均场模拟，揭示了大尺度半组织卷状结构的形成机制与时空特征，为理解相关大气、数值及实验中的大尺度卷起源提供参考。
To understand turbulent convection at very high Rayleigh numbers typical of natural phenomena, computational studies in slender cells are an option if the needed resources have to be optimized within available limits. However, the accompanying horizontal confinement affects some properties of the flow. Here, we explore the characteristics of turbulent fluctuations in the velocity and temperature fields in a cylindrical convection cell of aspect ratio 0.1 by varying the Prandtl number $Pr$ between 0.1 and 200 at a fixed Rayleigh number $Ra = 3 \times 10^{10}$, and find that the fluctuations wea…
Semi-organized structures and turbulence in the atmospheric convection
本研究将能量与通量收支（EFB）理论拓展至大气对流边界层核心区，推导得到半组织结构的动能、热能及全局湍流特征与相关参数的关系，可应用于建模及相关实验与模拟分析。
Self-consistent closure theory for passive-scalar turbulence has been developed on the basis of the Hessian of the scalar field. As a primitive indicator of spatial structure of the scalar, we employ the Hessian into the core of the theory to properly characterize the time scale intrinsic to the scalar field itself. The resultant closure model is now endowed with several realistic features, i.e. the scale-locality of the interscale interaction, the detailed conservation, and the memory-fading effect. Applying the current theory to the inertial-convective range eventually leads to self-consiste…
Direct Numerical Simulations of Ice-Ocean Boundary Turbulence
研究冰-海洋边界湍流中热和淡水输送机制，通过数值模拟揭示温度、盐度等参数对冰川融化速率的影响，发现对流过程在近水平坡度下仍具重要作用。
Classically studied coherent structures only paint a partial picture of wall-bounded turbulence
本文提出一种基于深度学习和SHAP可解释性的数据驱动方法，客观识别壁面湍流中的高重要性区域，发现其与经典相干结构部分吻合但又不完全对应，为理解湍流机制提供新视角。
Generating buoyant magnetic flux ropes in solar-like convective dynamos
我们的太阳表现出强烈的对流发电机作用，导致磁通量束通过恒星表面出现的磁点。全球尺度的发电机作用被认为通过对流、旋转和剪切的相互作用在太阳内部深处产生大尺度的磁结构。这些大规模的磁结构的一部分被认为会穿过对流层上升，形成磁环，然后穿透光球层成为太阳黑子对。以前的全球模拟旋转球壳中的3D MHD对流已经证明了大规模的磁环可以在对流区的大部分产生的机制。我们最近的模拟已经实现了足够高的湍流水平，允许这些花圈的部分成为磁浮力和上升通过模拟的对流层通过磁浮力和对流巨细胞平流的组合。这些浮力磁环是在对流层的大部分中产生的，因为磁环核心中的强洛伦兹力反馈抑制了小规模的对流运动，允许将局部磁能放大到局部动能的100倍以上。虽然磁环主要是由轴对称极向磁场的轴对称旋转剪切（$Ω$效应）产生的，但在开始上升之前，磁环被放大到其峰值场强。这进一步扩展和增强了一个新的范例，产生紧急磁通量束，我们称之为顺磁性使能磁浮力。
Nonuniqueness and Turbulence
湍流被认为是由微分方程描述的唯一性失败最大的可能性，至少在某些限制。在昂萨格提出的湍流应该用负的绝对温度来描述的背景下，无粘伯格斯方程就是这样一个极限。在这幅图中，湍流的开始与奇点的扩散相吻合，而奇点的扩散是唯一性失效的特征。
From Geostrophic to Magnetically-Damped Turbulence in Liquid Metal Rotating Magnetoconvection
本研究通过液态镓实验首次测量磁地转状态下的旋转磁对流，揭示了洛伦兹力与惯性力相对大小对流动标度律的影响，发现磁阻尼区传热增强，并外推得到地球核对流的参数区间。
We study the properties of various Eulerian contributions to fluid particle acceleration by using well-resolved direct numerical simulations of isotropic turbulence, with the grid resolution as high as $12288^3$ and the Taylor-scale Reynolds number $R_λ$ in the range between 140 and 1300. The variance of convective acceleration, when normalized by Kolmogorov scales, increases linearly with $R_λ$, consistent with simple theoretical arguments, but very strongly differing from phenomenological predictions of Kolmogorov's hypothesis as well as Eulerian multifractal models. The scaling of the local…
Unifying constitutive law of vibroconvective turbulence in microgravity
该研究通过直接数值模拟发现微重力下振动对流湍流存在普适热输运标度律，揭示了边界层竞争对标度指数的调控机制，明确其为独特的对流湍流普适类，为微重力环境可控热输运提供新思路。
Rapidly rotating radiatively driven convection: experimental and numerical validation of the `geostrophic turbulence' scaling predictions
本研究通过实验和直接数值模拟验证了快速旋转辐射驱动热对流在'地转湍流'区域的热传输、温度涨落、流速和流动结构标度预测，证明其是观察地球物理和天体物理扩散无关对流区域的有效实验装置。
We present an investigation of the root-mean-square (rms) temperature $σ_T$ and the rms velocity $σ_w$ in the bulk of Rayleigh-Bénard turbulence, using new experimental data from the current study and experimental and numerical data from previous studies. We find that, once scaled by the convective temperature $θ_*$, the value of $σ_T$ at the cell centre is a constant, i.e. $σ_{T,c}/θ_* \approx 0.85$, over a wide range of the Rayleigh number ($10^{8}\leq Ra\leq 10^{15}$) and the Prandtl number ($0.7\leq Pr \leq 23.34$), and is independent of the surface topographies of the top and bottom plate…
Comparing velocity and passive scalar statistics in fluid turbulence at high Schmidt numbers and Reynolds numbers
本文通过纳入施密特数高达512的文献数据，反驳了先前关于高雷诺数和施密特数下速度与被动标量统计量趋同的结论，证明两者本质差异始终存在。
Conductive and convective heat transfer in fluid flows between differentially heated and rotating cylinders
旋转加热圆柱与静止冷却圆柱之间的流体流动是工程上研究传热的一个典型实验。如果假设圆柱体在轴向方向上是无限长的或周期性的，在这种情况下，热传递仅通过固体中的传导发生，则该系统的理论处理被大大简化。在这里，我们调查数值传热和湍流的发病在这样的流动中，通过使用周期性和无滑移边界条件在轴向方向。我们得到一个简单的线性准则，确定是否可以采用无限圆柱假设。圆柱体的曲率通过斜率和附加常数进入这种线性关系。对于给定的长度与间隙的纵横比，存在一个临界瑞利数，超过该临界瑞利数，有限系统中的层流是对流的，因此其行为与周期性情况完全不同。该标准不依赖于普朗特数，并出现相当强大的雷诺数。特别是，它继续在动荡的政权中合理地发挥作用。
Mean-Lagrangian formalism and covariance of fluid turbulence
基于平均场的拉格朗日框架的流体湍流理论的发展。从平均速度中自然地引入了时空矢量流，它以与瞬时场完全等价的方式提供了基于平均场的拉格朗日图像。该框架一方面应用于单点闭合模型，给出了湍流粘弹性效应的客观表达式;另一方面，还讨论了两点闭合的应用，其中已知的拉格朗日相关的自然扩展是在扩展协方差组的基础上发现的。
Quad-cascade picture of electrokinetic turbulence
针对外体积力影响下湍流标度行为无法被柯尔莫哥洛夫定律充分描述的问题，研究提出耦合动能与标量方差通量的通用四级联湍流框架，经微流控电动湍流实验验证吻合良好，深化了相关级联过程的理解。
Assessing passive scalar dynamics in bubble-induced turbulence using DNS
本研究通过DNS分析气泡诱导湍流中的被动标量，发现标量谱从k^-5/3到k^-3的转变，并揭示其机制与气泡直径尺度相关，同时探讨了对流扩散率的影响。
Motivated by understanding the dynamics of stellar and planetary interiors, we have performed a set of direct numerical simulations of Boussinesq convection in a rotating full sphere. The domain is internally heated with fixed temperature and stress-free boundary conditions, but fixed heat flux and no-slip boundary conditions are also briefly considered. We particularly focus on the large-scale coherent structures and the mean zonal flows that can develop in the system. At Prandtl number of unity, as the thermal forcing (measured by the Rayleigh number) is increased above the value for the ons…
Kolmogorov and Bolgiano scaling in thermal convection: the case of Rayleigh-Taylor turbulence
本文研究了一个长宽比较大的对流单体中Rayleigh-Taylor湍流的统计特性。我们发现，限制的规模决定了系统的Bolgiano规模，在演化的后期阶段，其特征在于Kolmogorov-Obukhov和Bolgiano-Obukhov现象在小尺度和大尺度，分别。这些制度的共存与三维到二维的过渡时发生的湍流混合层的宽度变得更大的限制的规模的系统。
Elastic wave-turbulence and intermittency
弱波湍流理论是一种强有力的理论，可以预测各种相关物理现象的统计观测值，如海浪，磁流体力学和非线性光学。该理论是基于小的非线性极限允许的渐近封闭。在这里，我们探讨了从这个平均场框架的可能偏差，在异常标度，专注于弹性板的情况下。我们建立的图片可能的行为在不同程度的非线性，我们表明，平均场论是适当的，当所有的激发尺度仍然占主导地位的线性动力学。另一幅图是不平凡的，我们的研究结果表明，当大尺度包含大量的能量，级联维持极端事件在小尺度和系统显示不稳定性。
Small scale quasi-geostrophic convective turbulence at large Rayleigh number
本研究通过数值模拟探究大瑞利数下小尺度准地转对流湍流，发现无扩散标度律趋势、粘性控制的长度尺度及非局域CIA力平衡特征，修正了对高瑞利数区对流动力学的传统认知。
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