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Acta Mechanica Sinica 2023年第5期39卷 76-82页

作者：张又升倪玮丹 Institute of Applied Physics and Computational Mathematics Beijing100094China Center for Applied Physics and Technology Key Laboratory of High Energy Density Physics Simulationand College of EngineeringPeking UniversityBeijing100871China

瑞利-泰勒(RT)湍流混合阶段的气泡统计直径d和高度h随时间的演化规律对许多自然现象和工程应用都至关重要.对于由多模短波扰动演化而来的RT问题,大量数值模拟和最新实验(*** et al.,2020)均表明,气泡统计直径d和高度h具有普适性的增长规... 详细信息

瑞利-泰勒(RT)湍流混合阶段的气泡统计直径d和高度h随时间的演化规律对许多自然现象和工程应用都至关重要.对于由多模短波扰动演化而来的RT问题,大量数值模拟和最新实验(*** et al.,2020)均表明,气泡统计直径d和高度h具有普适性的增长规律.但是,到目前为止,先前研究者仍然没有给出能够同时准确预测这两个特征量的自洽模型.在本文中,基于半约束思想和浮阻力模型,我们建立了一个能够同时适用于二维(2D)及三维(3D)流动的统一气泡融合模型.新模型表明:(1)气泡平均直径d呈自相似增长,相应的自相似结构参数β≡d/h≈(1+A)/2和(1+A)/4,其中阿特伍德数A是密度比的函数;(2)气泡高度h与时间呈二次增长关系,其中二次增长系数α≡h/(Agt^(2))≈0.05(2D)和0.025(3D),其中g为加速度,t为时间.结果表明,新模型的预测结果与先前的实验和数值模拟结果一致,对理解RT湍流混合具有重要意义.

关键词： Rayleigh-Taylor instability turbulent mixing Bubble merger model

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Application of Mechanical Similarity Laws to the Collection Efficiencies of Geometrically Types of Uni-Flow Cyclone Dust Collectors

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Journal of Thermal Science 1993年第2期2卷 87-87页

作者： Akira OGAWA Kazuya SUGIYAMA Department of Mechanical Engineering College of Engineering Nihon University T-963. Tokusada Tamura-machi Kooriyama-shi Japan Professor Dr. Sanyo-Electric Co. Ltd T-570. Kyosaka Hondori 2-18 Moriguchi-shi Oosaka-hu Japan

From the mechanical similarity point of view, the centrifugal effect, Ar, and the Stokes number, St, as well as the Reynolds number, Re_c for the motion of solid particles in the cyclone are the relevant parameters. In order to apply these similarity laws for the prediction of the characteristics of the collection efficiency, ηc, geometrically similar types of uni-flow cyclones were used. The body diameters of the cyclones were D_1=30, 50, 69 and 99 mm, respectively. The feed particle concentration of the fly-ash particles was up to C_o = 60g/m^3. From the experimental results: (1) the pressure drop, △pc, in the cyclones was a function of not only the Reynods number, Re_c, but also the body diameter, D_1; (2) the collection efficiency, η_c, did not always increase with decreasing body diameter but there existed an optimal body size; (3) application of the mechanical similarity laws to the collection efficiency was not always sufficient for estimating the collection efficiency, since the feed particle concentration was an additional important factor; (4) a new parameter which was the ratio, E_(pf), of the apparent separation energy, W_p, of the solid particles to the energy loss, E_c, of the gas flow in the cyclone was introduced for discussing the collection efficiency; (5) Fuchs theory, used to estimate the collection efficiency, was examined. Fuchs theory may be applied for high feed particle concentration.

关键词： vortex flow turbulent diffusion turbulent mixing cyclone dust collector collection efficiency mechanical similarity law fuchs theory

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Numerical Simulation of Hot Spot Growth in Detonation with Regard to the turbulent Mechanism of Energy Transfer

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Journal of Physical Science and Application 2015年第3期5卷 226-237页

作者： Yury Vasilyevich Yanilkin Vitaly Grigoryevich Morozov Irina Isorevna Karpenko Olga Nikolaevna Chernyshova Russian Federal Nuclear Centre VNIIEF Sarov 607200 Russia

The paper presents the results of numerical modeling of hot spot growth process in detonation with account for turbulent mixing. The performed investigation has shown that large-scale HE （High explosives） particles mix up and split down to smaller sizes in the result of shock wave impact, instability development on the HE-EP （Explosion product） interface and vortex flow; at these sizes, due to the developed surface of the HE-EP contact, HE has enough time to get heated （energy transfer from EP）, and the decomposition reaction effectively continues. Numerical modeling make the calculation of the hot spot growth rate （about 100-200 m/s） possible. This has proved the hypothesis saying that at mechanical material transport the turbulence in the reaction zone plays an important role and it must be taken into account in the detonation theory.

关键词： Hot spot detonation turbulent mixing numerical simulation.

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Effects of a two-equation turbulence model on the simulation of the internal lee waves

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Atmospheric and Oceanic Science Letters 2021年第5期14卷 30-36页

作者： Xuhui Hu Xuefeng Zhang Lei Lin Lianxin Zhang Shifan Wang School of Marine Science and Technology Tianjin UniversityTianjinChina College of Ocean Science and Engineering Shandong University of Science and TechnologyQingdaoChina Key Laboratory of Marine Environmental Information Technology National Marine Data and Information ServiceMinistry of Natural ResourcesTianjinChina

In order to understand the wave-turbulence interaction under non-hydrostatic conditions to prepare future ad-vanced very-high-resolution ocean reanalysis data,an𝜎-coordinate ocean model-namely,the Marine Environ-ment Research and Forecasting(MERF)model-with an idealized supercritical slope topography is applied to conduct a series of high-resolution numerical experiments with and without the non-hydrostatic *** popular Mellor-Yamada two-equation turbulence model(MY2.5)is enclosed in MERF to validate its effect on small-scale internal lee *** results show that the internal lee-wave processes are relaxed through employment of the MY2.5 scheme,whether or not in the non-hydrostatic *** averaged results suggest the influences of the vertical mixing parameterization scheme on the numerical results are more dominant than the non-hydrostatic/hydrostatic selection for the large-scale dynamic ***,diagnostic analyses of the energy budget show that the spread of internal lee waves at the slope is dramatically suppressed by the vertical turbulent mixing,indicating more tidal energy is able to be converted into the irreversible mixing when the two-equation turbulence model is employed.

关键词： Non-hydrostatic MERF Internal wave turbulent mixing

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Dynamic criterion for the formation of surface water-blooms

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Theoretical & Applied Mechanics Letters 2013年第4期3卷 29-31页

作者： Yong Gao Qingquan Liu Key Laboratory for Mechanics in Fluid Solid Coupling Systems Institute of Mechanics Chinese Academy of Sciences

Surface water-blooms （SWBs） is usually explained as a buoyant migration of blue-green algae to the water surface under the conditions of reduced turbulence. Wind-induced turbulent mixing can cause considerable heterogeneity in the vertical concentration distribution of algal cells. There exists a criterion below which cell buoyancy can overcome the turbulent mixing. Former researchers regarded a certain wind speed as this criterion, but this wind speed differs in value. In this research, we propose a new criterion, nondimensional entrainment number （En）, which represents the ratio of the intrinsic velocity of algal cells relative to the characteristic velocity of wind-induced mixing. Observation in Taihu Lake demonstrates that this new criterion is more suitable for the description of hydrodynamic effect on the formation of surface water-blooms.

关键词： SWBs microcystis turbulent mixing wind speed entrainment number

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Numerical Study on Turbulence mixing of Planar Shock Accelerated Triangular Heavy Gases Interface

Numerical Study on Turbulence mixing of Planar Shock Acceler...

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2016海峡两岸流体力学研讨会

作者： Wei-Gang Zeng Jian-Hua Pan Yu-Tao Sun Yu-Xin Ren School of Aerospace Engineering Tsinghua University Beijing Institute of Applied Physics and Computational Mathematics

The interaction of a planar shock wave with a sulfur hexafluoride(SF6) triangular surrounded by air is numerically studied based on high resolution finite volume method with Minimum Dispersion and Controllable Dissipation(MDCD) reconstruction. The vortex dynamics of Richtmyer-Meshkov instability(RMI) and the turbulent mixing during the evolution of Kelvin–Helmholtz instability(KHI) are discussed. The typical processes of shock driven interfacial instability until turbulent mixing transition are identified in this study. The spectral analysis of turbulent kinetic energy(TKE) shows that the merging process of the primary Kelvin–Helmholtz billows will extend the region with a broadband spectrum of motion, and consequently, enhance the overall mixing of fluids. Both analysis of the TKE spectra and the variable-density energy spectra manifests the inertial range by the latter stages. Additionally, length scale analysis shows that the Liepmann-Taylor scale is decoupled from the inner-viscous scale during the evolution, which implies that there is a turbulent mixing transition. A further analysis of energy transfer in Fourier space indicates the nonlinear transfer term is of significance while the physical dissipation term is negligible. The detailed analysis for the nonlinear transfer term implies that the quadratic and pressure components are dominant terms, but the dilatation component is of less significance due to the weak compressibility. It is observed that the quadratic and pressure components tend to cancel each other in most part of the mixing region. The underlining mechanism is studied and its relation with the transition to turbulence is identified.

关键词： MDCD Richtmyer-Meshkov instability Kelvin–Helmholtz instability Length scale turbulent mixing

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