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PARTICLE SIZE DISTRIBUTION IN A planar jet FLOW UNDER-GOING SHEAR-INDUCED COAGULATION AND BREAKAGE

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Journal of Hydrodynamics 2010年第4期22卷 445-455页

作者： GAN Fu-jun LIN Jian-zhong YU Ming-zhou State Key Laboratory of Fluid Power Transmission and Control Zhejiang University Hangzhou 310027 China China Jiliang University Hangzhou 310018 China State Key Laboratory of Fluid Power Transmission and Control Zhejiang University Hangzhou 310027 China China Jiliang University Hangzhou 310018 China

A CFD simulation is performed for a particle-laden planar jet *** Reynolds number is 8300,and the initial particle diameter is 1 μ*** Eddy Simulation（LES） is employed to calculate the flow field,and the Taylor-series expansion moment method（TEMOM） is adopted to deal with the balance equation of particle coagulation and *** shear-induced coagulation kernel,power-law breakage kernel and symmetric fragment distribution function are *** prediction of the distribution of the mean streamwise velocity of the jet is in good agreement with experimental *** evolution of particle number concentration,volume concentration,polydispersity,particle diameter and standard geometric deviation is discussed in *** results show that as the jet travels downstream,the particle number concentration and volume concentration decrease,while their spans become *** polydispersity and particle diameter are very large in the shear layers at the upstream and in the core of vortex structures at the *** particle standard geometric deviation changes within the range of 1.32 ≤σg≤ 1.96,and increases sharply in the shear *** variables approach the steady-state as time progresses.

关键词： Taylor-series expansion moment method shear-induced coagulation breakage planar jet

Nanoparticle coagulation in a planar jet via moment method

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Applied Mathematics and Mechanics(English Edition) 2007年第11期28卷 1445-1453页

作者：于明州林建忠陈丽华 Department of Mechanics State Key Laboratory of Fluid Power Transmission and Control Zhejiang University

Large eddy simulations of nanoparticle coagulation in an incompressible planar jet were performed. The particle is described using a moment method to approximate the particle general dynarnics equations. The time-averaged results based on 3000 time steps for every case were obtained to explore the influence of the Schmidt number and the Damkohler number on the nanoparticle dynamics. The results show that the changes of Schmidt number have the influence on the number concentration of nanoparticles only when the particle diameter is less than 1 nm for the fixed gas parameters. The number concentration of particles for small particles decreases more rapidly along the flow direction, and the nanoparticles with larger Schmidt number have a narrower distribution along the transverse direction. The smaller nanoparticles Coagulate and disperse easily, grow rapidly hence show a stronger polydispersity. The smaller coagulation time scale can enhance the particle collision and coagulation. Frequented collision and coagulation bring a great increase in particle size. The larger the Damkohler number is, the higher the particle polydispersity is.

关键词： nanoparticles coagulation planar jet moment method large eddy simulation

Dynamics and geometry of developing planar jets based on the invariants of the velocity gradient tensor

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Journal of Hydrodynamics 2015年第6期27卷 894-906页

作者：吴楠楠 SAKAI Yasuhiko NAGATA Kouji ITO Yasumasa School of Electric Power Engineering China University of Mining and Technology Department of Mechanical Science and Engineering Nagoya University

Based on the direct numerical simulation （DNS）, the developing planar jets under different initial conditions, e.g., the con- ditions of the exit Reynolds number and the exit mean velocity profile, are investigated. We mainly focus on the characteristics of the invariants of the velocity gradient tensor, which provides insights into the evolution of the dynamics and the geometry of the planar jets along with the flow transition. The results show that the initial flow near the jet exit is strongly predominated by the dissipation over the enstrophy, the flow transition is accompanied by a severe rotation and straining of the flow elements, where the vortex structure evolves faster than the fluid element deformation, in the fully-developed state, the irrotational dissipation is dominant and the most probable geometry of the fluid elements should remain between the biaxial stretching and the axisymmetric stretching. In addition, with a small exit Re and a parabolic profile for the exit mean streamwise velocity, the decay of the mean flow field and the magnitude of the turbulent variables will be strengthened in the process of the flow transition, however, a large exit Re will promote the flow transition to the fully-developed state. The cross-impact between the exit Re and the exit mean velocity profile is also observed in the present study.

关键词： planar jet direct numerical simulation (DNS) velocity gradient tensor flow transition joint probability density function(joint pdf)