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preferential concentration in supersonic gas-particle two-phase transverse jets

Particuology 2024年第11期94卷 29-47页

作者： Likun Ma Luxi Xu Kangchun Zhao Pengnian Yang Yunchao Feng Binbin Chen Zhixun Xia Hypersonic Technology Laboratory National University of Defense TechnologyChangsha410073China

The supersonic gas-particle two-phase transverse jet is a typical flow process in many applications,such as solid rocket *** study carried out experimental tests as well as Large Eddy Simulation(LES)to investigate the evolution process of transverse gas-particle two-phase jets in supersonic crossflow,especially focusing on the phenomena called preferential *** simulation is based on the Eulerian-Lagrangian method,which successfully reproduces the characteristic phenomena observed in *** particle cloud forms three different characteristic distribution patterns:tooth-like waves near the jet port,quasi-ordered structures near counter-rotating vortex pairs(CVP),and filamentous clouds in the upper *** turbulence and small unstable shock play a suppressing role in mixing small-diameter particles,which tend to aggregate in regions of high density and low ***,it is found that there exists a specific range of particle sizes,as particles'sizes approach this specific range,the influence of compressibility of the airflow on particle distribution becomes increasingly ***,this study shed some light on the understanding of the complex and intricate nature of the supersonic gas-particle two-phase transverse jet.

关键词： Supersonic Crossflow Gas-particleflow preferential concentration

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Effect of turbulence-driven secondary flow on particle preferential concentration and clustering in turbulent square duct flows

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Particuology 2021年第2期19卷 70-83页

作者： Yanlin Zhao Yanzhi Wang Jun Yao International Joint Laboratory on Clean Energy Science and Technology Beijing Key Laboratory of Process Fluid Filtration and SeparationCollege of Mechanical and Transportation EngineeringChina University of Petroleum-BeijingBeijing 102249China

In this study,the preferential concentration and clustering of inertial particles in fully developed turbulent square duct flows are studied using large eddy simulations combined with Lagrangian approach,where the Reynolds number is equal to Reτ=600(based on the mean friction velocity and duct full height),and the particle Stokes number ranges from 0.0007 to *** results obtained for duct flows are compared with those for channel flows under the same working ***,the effect of the secondary flow on the particle concentration in duct flows is *** equation of particle motion is governed by the drag force,lift force,added mass force,pressure gradient force,and *** inter-phase interaction that was considered includes one-way and two-way *** simulations of a single phase are verified and in good agreement with the available literature *** the discrete phase,particles in the duct flow are found to be more dispersed in the vertical direction compared with the channel *** near-wall regions,a small fraction of particles tends to accumulate in duct corners,forming stable particle streaks under the effect of the secondary ***,most particles are likely to reside preferentially in the low-speed flow regions and form elongated particle streaks steadily in the middle region of duct or channel *** Voronoi diagram analysis shows that the near-wall secondary flows in the square duct could cause particle clusters to transfer from regions of high to low concentration,and this trend increases with particle *** addition,two-way coupling is found to enhance the near-wall particle accumulation and to promote particles to form more elongated streaks than one-way ***,the mechanism responsible for the particle preferential concentration in turbulent square duct flows is determined.

关键词： Secondary flow preferential concentration Turbulence Particles Square duct

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Particle behavior in homogeneous isotropic turbulence

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Acta Mechanica Sinica 2005年第2期21卷 112-120页

作者： ZhuHe ZhaohuiLiu ShengChen LeiWeng ChuguangZheng StateKeyLaboratoryofCoalCombustion HuazhongUniversityofScienceandTechnologyWuhan430074China

Direct numerical simulations were conducted to investigate the behavior of heavy particles in homogeneous isotropic turbulence. The present study focused on the effect of particle inertia and drift on the autocorrelations of the particle velocity and the fluid seen by particles and the dispersion characteristics of particles. The Lagrangian integral time scale of particles monotonically increased as the magnitude of the particle response time increased, while that of the fluid seen by particles remained relatively constant; it reached a maximum when the particle response time was close to the Kolmolgorov time scale of the flow. Particle dispersion increased as the particle inertia increased for small particles, while for larger particles, it decreased as particle inertia increased; particle eddy diffusion coefficient was maximal, and greater than that of the fluid by about 30%, at the preferential concentration. The concentration field of the particles with p/k1.0 showed that particles tend to collect in regions of low vorticity (high strain) due to preferential concentration. As the drift velocity of a particle is increased it crosses the paths of fluid elements more rapidly and will tend to lose correlation with its previous velocity faster than a fluid element will. And the correlation of particle velocities along the drift direction is more persistent than that perpendicular to the direction of drift. Simulations also showed that the continuity effect and the crossing-trajectory effect are weakened for particles with infinite inertia.

关键词： Direct numerical simulation Inertial effect Continuity effect Crossing-trajectory effect preferential concentration

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Analysis of solid particle clusters in coherent structures of turbulent channel flow

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Science China(Technological Sciences) 2013年第10期56卷 2525-2530页

作者： LU Hao WANG Bing ZHANG HuiQiang QIN JianXiu WANG XiLin School of Aerospace Tsinghua University

A particle-laden turbulent channel flow is investigated to study particle clusters in large-scale turbulent coherent structures. The fluid phase is calculated by large eddy simulation and particles are tracked using Lagrangian trajectory method. The flow Reynolds number is 180 based on the friction velocity and half-width of the channel. The particle is lycopodium with St=0.93 which may well follow the fluid phase. The mean and fluctuating velocities of both two phases are obtained, which are in good agreement with previous data. The strongest accumulations of particles in low-speed streak structures are observed at y~=l 1.3. Moreover, once particles are captured in low-speed streaks, most of them will reside there for a long period. Particles clustered in low-speed streaks obtain smaller instantaneous wall-normal and spanwise velocities than those out of there, which induce a larger particle flux into low-speed streaks than that out of there. The study is important for understanding particle dispersion mechanisms in gas-particle turbulent channel flows.

关键词： particle cluster preferential concentration low-speed streak coherent structure large eddy simulation Lagrangiontrajectory method

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