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Single point velocity distributions in homogeneous isotropic turbulence

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Chinese Physics B 2009年第10期18卷 4360-4365页

作者：燕秀林冉政 Shanghai Institute of Applied Mathematics and Mechanics Shanghai University

The starting point for this paper lies in the results obtained by Tatsumi （2004） for isotropic turbulence with the self-preserving hypothesis. A careful consideration of the mathematical structure of the one-point velocity distribution function equation obtained by Tatsumi （2004） leads to an exact ＂analysis of all possible cases and to all admissible solutions of the problem. This paper revisits this interesting problem from a new point of view, and obtains a new complete set of solutions. Based on these exact solutions, some physically significant consequences of recent advances in the theory of homogenous statistical solution of the Navier-Stokes equations are presented. The comparison with former theory was also made. The origin of non-Caussian character could be deduced from the above exact solutions.

关键词： isotropic turbulence probability distribution function

Nonlinear dynamical systems and bistability in linearly forced isotropic turbulence

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Acta Mechanica Sinica 2013年第6期29卷 823-826页

作者： Zheng Ran Xing-Jie Yuan Shanghai Institute of Applied Mathematics and Mechanics Shanghai University

In this paper, we present an extensive study of the linearly forced isotropic turbulence. By using analytical method, we identify two parametric choices, of which they seem to be new as far as our knowledge goes. We prove that the underlying nonlinear dynamical system for linearly forced isotropic turbulence is the general case of a cubic Lienard equation with linear damping. We also discuss a FokkerPlanck approach to this new dynamical system, which is bistable and exhibits two asymmetric and asymptotically stable stationary probability densities.

关键词： isotropic turbulence Nonlinear dynamical system Karman-Howarth equation

Second-order relative exponent of isotropic turbulence

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Theoretical & Applied Mechanics Letters 2011年第3期1卷 74-77页

作者： Shuxiao Wan,and Zheng Ran~(a) Shanghai Institute of Applied Mathematics and Mechanics,Shanghai University,Shanghai 200072,China Shanghai Institute of Applied Mathematics and Mechanics Shanghai University Shanghai 200072 China

Theoretical results on the scaling properties of turbulent velocity fields are reported in this *** on the Kolmogorov equation and typical models of the second-order statistical moments (energy spectrum and the second-order structure function),we have studied the relative scaling using the ESS *** is found that the relative EES scaling exponent Sis greater than the real or theoretical inertial range scaling exponentξ,which is attributed to an evident bump in the ESS range.

关键词： isotropic turbulence structure function EES scaling exponent

Assessment of the modulated gradient model in decaying isotropic turbulence

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Theoretical & Applied Mechanics Letters 2011年第4期1卷 23-27页

作者： Hao Lu a) Saint Anthony Falls Laboratory,Department of Civil Engineering,University of Minnesota-Twin Cities,2 3rd Ave.SE,Minneapolis,MN 55414,USA Saint Anthony Falls Laboratory Department of Civil Engineering University of Minnesota-Twin Cities 23rd Ave. SE Minneapolis MN 55414 USA

A recently introduced nonlinear model undergoes evaluations based on two isotropic turbulent cases:a University of Wiscosion-Madison case at a moderate Reynolds number and a Johns Hopkins University case at a high Reynolds *** model uses an estimation of the subgrid-scale(SGS) kinetic energy to model the magnitude of the SGS stress tensor,and uses the normalized velocity gradient tensor to model the structure of the SGS stress *** is performed for the first case through a comparison between direct numerical simulation(DNS) results and large eddy simulation(LES) results regarding resolved kinetic energy and energy *** the second case,we examine the resolved kinetic energy,the energy spectrum,as well as other key statistics including the probability density functions of velocities and velocity gradients,the skewness factors,and the flatness *** using the model are numerically stable,and results are satisfactorily compared with DNS results and consistent with statistical theories of turbulence.

关键词： large-eddy simulation subgrid-scale model isotropic turbulence

Analysis of Coherent Structures in isotropic turbulence with Polymer Additives

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Analysis of Coherent Structures in Isotropic Turbulence with...

Lagrangian statistics in isotropic turbulent flows with deterministic and stochastic forcing schemes

2011 World Congress on Engineering and Technology(CET 2011)

作者： Weihua. Cai Fengchen. Li Hongna. Zhang Lu Wang Zhiying Zheng School of Energy Science and Engineering Harbin Institute of Technology Harbin China 150001

Direct numerical simulation （DNS） of forcing homogeneous isotropic turbulence with polymers has been *** order to understand the polymers effect on turbulent coherent structures,proper orthogonal decomposition was performed to identify coherent structures based on DNS data,so as to analyze the remarkable difference due to the addition of *** results showed that,the amount of eigenmodes required for capturing coherent structures was 32 and 24 for the Newtonian fluid and polymer solution flows,respectively,which means the decrease of the complexity in polymer solution flow.

关键词： coherent structures polymer drag reduction proper orthogonal decomposition isotropic turbulence

来源： cnki会议评论

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cnki会议

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Acta Mechanica Sinica 2015年第1期31卷 25-31页

作者： Jin-Cai Chen Guo-Dong Jin Jian Zhang LNM Institute of MechanicsChinese Academy of Sciences

Artificial input of energy into the flow is neces sary to create and maintain a statistically stationary isotropic turbulence for sampling in studying the statistics. Due to the nonlinear coupling among different Fourier modes through the triadic interaction, whether or not various forc ing schemes affect the statistics in turbulence is an impor tant and open question. We present detailed comparison of Lagrangian statistics of fluids particles in forced isotropic turbulent flows in 1283, 2563, and 5123 simulations, with Taylorscale Reynolds numbers in the range of 64-171, us ing a deterministic and a stochastic forcing scheme, respec tively. Several Lagrangian statistics are compared, such as velocity and acceleration autocorrelations, and moments of Lagrangian velocity increments. The differences in the La grangian statistics obtained from the two forcing schemes are shown to be small, indicating that the isotropic forcing schemes used have little effects on the Lagrangian statistics in the isotropic turbulence.

关键词： isotropic turbulence Deterministic forcingscheme Stochastic forcing scheme Lagrangian statisticalquantities

AN ANALYSIS OF SUBGRID-RESOLVED SCALE INTERACTIONS WITH USE OF RESULTS FROM DIRECT NUMERICAL SIMULATIONS

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Acta Mechanica Sinica 1999年第2期15卷 108-115页

作者： H. Gong S. Chen G.W. He Environment Safety and Health Division and Center for Nonlinear Studies Los Alamos National Laboratory Los Alamos NM 87545 USA LNM Institute of Mechanics Chinese Academy of Sciences Beijing 100080 China

Subgrid nonlinear interaction and energy transfer are analyzed using direct numerical simulations of isotropic turbulence. Influences of cutoff wave number at different ranges of scale on the energetics and dynamics have been investigated. It is observed that subgrid-subgrid interaction dominates the turbulent dynamics when cut-off wave number locates in the energy-containing range while resolved-subgrid interaction dominates if it is in the dissipation range. By decomposing the subgrid energy transfer and nonlinear interaction into ‘forward’ and ‘backward’ groups according to the sign of triadic interaction, we find that individually each group has very large contribution, but the net of them is much smaller, implying that tremendous cancellation happens between these two groups.

关键词： subgrid nonlinear interaction energy transfer large eddy simulation (LES) subgrid scale (SGS) direct numerical simulation isotropic turbulence

Correlation Analysis on the SGS Velocity between Phases in an isotropic Gasparticle Two-phase Flow with FDF Model

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Journal of Thermal Science 2012年第5期21卷 447-451页

作者： Hanhui Jin Yuhui Chen Jianren Fan Kun Luo School of Aeronautics and Astronautics Zhejiang University Hangzhou 310027 China State Key Laboratory of Clean Energy Utilization Zhejiang University Hangzhou 310027 China

Correlation of the SGS (sub-grid scale) velocity between the two phases in an isotropic gas-particle two-phase flow was numerically investigated with FDF model. The results show the SGS gas velocity seen by the particles varies with the relative velocities between particle phase and gas phase. The relative velocity between the two phases produces the effect of the anisotropic turbulence on the particles. The variation of Stokes number influences the magnitude of the interaction between the two phases.

关键词： sub-grid scale velocity isotropic turbulence filtered density function model

Lagrangian and Eulerian Statistics from Direct Numerical Simulations of Turbulent Channel Flow

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Chinese Physics Letters 2006年第4期23卷 883-886页

作者：罗剑平 Tatsuo Ushijima Osami Kitoh Nagoya Institute of Technology Gokiso-cho Showa-ku Nagoya 466-8555 Japan

Lagrangian and Eulerian statistics are obtained from the direct numerical simulation of a turbulent channel flow. The Reynolds number is obtained to be Reτ = 100 （based on friction velocity and channel half-height）. The Lagrangian time microscales are compared to their Eulerian equivalents. It is found that the Lagrangian time microscales equal the Eulerian time microscales at the wall, but they are consistently larger than the Eulerian away from the wall. The Eulerian time scales are also found to be scaled by the propagation velocity rather than the mean velocity. The ratio of the Lagrangian to the Eulerian time microscales is found to be nearly constant away from the wall （y^＋〉 40）.

关键词： isotropic turbulence FLUID PARTICLES VELOCITY DISPERSION GRADIENT