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NUMERICAL STUDY ON TURBULENT COUNTER-GRADIENT-TRANSPORT PHENOMENA IN ASYMMETRIC TURBULENT CHANNEL FLOW

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Journal of Hydrodynamics 2003年第4期15卷 41-45页

作者： Wang Li-bing, liu yu-lu, Qiu Xiang Shanghai Institute of Applied Mathematics and Mechanics, Shanghai University, Shanghai 200072, China Inst. of Appl. Math. and Mech. Shanghai Univ. Shanghai 200072 China

In this paper, the turbulence characteristics were numerically investigatedin an asymmetric turbulent channel flow and the computational results were compared with therelevant experimental data. It shows that the results are consistent with the experiments and thereexist Counter-Gradient Momentum Transport (CGMT) phenomena in the central region near the smoothwall, and this region is as large as 6 percent of the channel width. In addition, a region, in whichCounter-Gradient-Transport (CGT) phenomena occur more evidently, is found close to the rough *** results can help to gain a deeper insight into the mechanism of CGT phenomena.

关键词： counter-gradient-transport phenomena turbulence characteristic asymmetricturbulent channel flow

Scale analysis of turbulent channel flow with varying pressure gradient

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Journal of Hydrodynamics 2014年第1期26卷 129-136页

作者：邱翔罗剑平黄永祥卢志明刘宇陆 School of Science Shanghai Institute of Technology School of Mechanical Engineering Shanghai Institute of Technology Shanghai Institute of Applied Mathematics and Mechanics Shanghai University

In this paper orthogonal wavelet transformations are applied to decompose experimental velocity signals in fully develo-ped channel flows with varying pressure gradient into scales. We analyze the time series from turbulent data, to obtain the statistical characteristics, correlations between the adjacent scales and the principal scale of coherent structures in different scales by wavelet transformations. The results show that, in the counter gradient transport （CGT） region, skewness factors and flatness factors deviate strongly from the corresponding values of Gaussian distribution on certain scales. PDFs on each scale confirm this observation. Scale-scale correlations show further that the fluctuations on some certain special scales are more intermittent than nearby. Principal scale of coherent structure is coincident with the scales on which the statistical properties depart from Gaussian distribution. These features are the same for different families of wavelets, and it also shows some different features in the region between favorable pressure gradient and adverse pressure gradient.

关键词： turbulence counter gradient transport (CGT) wavelet analysis pressure gradient channel flow

Analysis of temperature time series based on Hilbert-Huang Transform

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Journal of Hydrodynamics 2015年第4期27卷 587-592页

作者：马皓邱翔罗剑平顾品强刘宇陆 School of Mechanical Engineering Shanghai Institute of Technology School of Science Shanghai Institute of Technology Shanghai Meteorological Service in Fengxian District Shanghai Institute of Applied Mathematics and Mechanics Shanghai University

In this paper, with consideration of the nonlinear and non-stationary properties of the temperature time series, we employ the Hilbert-Huang Transform, based on the empirical mode decomposition（EMD）, to analyze the temperature time series from 1959 to 2012 in the Fengxian district of Shanghai, obtained from a certain monitoring station. The oscillating mode is drawn from the data, and its characteristics of the time series are investigated. The results show that the intrinsic modes of 1, 2 and 6 represent the periodic properties of 1 year, 2.5 years, and 27 years. The mean temperature shows periodic variations, but the main trend of this fluctuation is the rising of the temperature in the recent 50 years. The analysis of the reconstructed modes with the wave pattern shows that the variations are quite large from 1963 to 1964, from 1977 to 1982 and from 2003 to 2006, which indicates that the temperature rises and falls dramatically in these periods. The volatility from 1993 to 1994 is far more dramatic than in other periods. And the volatility is the most remarkable in recent 50 years. The log-linear plots of the mean time scales T and M show that each mode associated with a time scale almost twice as large as the time scale of the preceding mode. The Hilbert spectrum shows that the energy is concentrated in the range of low frequency from 0.05 to 0.1 Hz, and a very small amount of energy is distributed in the range of higher frequency over 0.1 Hz. In conclusion, the HHT is better than other traditional signal analysis methods in processing the nonlinear signals to obtain the periodic variation and volatility＇s properties of different time scales.

关键词： atmospheric turbulence temperature time series empirical mode decomposition(EMD) Hilbert Huang Transform

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Maccari系统的椭圆函数传播波

物理学报 2007年第9期56卷 5026-5032页

作者：黄文华刘宇陆湖州师范学院理学院上海大学应用数学和力学研究所上海200072 上海大学应用数学和力学研究所

基于多线性分离变量法所得(2+1)维Maccari非线性系统的精确解,在分离变量函数中引入雅克比椭圆函数,获得两类双周期传播波模式.椭圆函数波在不同模量取值下,具有不同的性状特点,特别是在模量极限情形下,可以约化为dromion和peakon激发形... 详细信息

基于多线性分离变量法所得(2+1)维Maccari非线性系统的精确解,在分离变量函数中引入雅克比椭圆函数,获得两类双周期传播波模式.椭圆函数波在不同模量取值下,具有不同的性状特点,特别是在模量极限情形下,可以约化为dromion和peakon激发形态.利用图示法对椭圆函数波的相互作用进行了探讨,发现其相互作用是非弹性的.

关键词： Maccari系统多线性分离变量法雅克比椭圆函数周期波

Lagrangian Structure Function＇s Scaling Exponents in Turbulent Channel Flow

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Chinese Physics Letters 2010年第2期27卷 169-171页

作者：罗剑平卢志明牛岛连夫鬼頭修己刘宇陆 Shanghai Institute of Technology Shanghai 200235 Shanghai Institute of Applied Mathematics and Mechanics Shanghai University Shanghai 200072 Nagoya Institute of Technology Gokiso-cho Showa-ku Nagoya 466-8555 Japan

The Lagrangian structure function＇s scaling exponents and intermittency of three-dimensional incompressible turbulent channel flow are investigated by using direct numerical simulation. The intermittency in streamwise velocity increments is found to increase in the near-wall region, which can be attributed to the presence of strong mean shear and organized motions in the near-wall region. It is found that the intermittency of transverse velocity increments is weaker than that of longitudinal ones. The present ESS evaluation of ζL（q） for the structure function of the streamwise velocity component in the channel centre is fairly close to experimental estimates of isotropic turbulence.

关键词： Fluid dynamics

A DELAY-DIFFUSION DESCRIPTION FOR TWO-DIMENSIONAL CONTAMINANT DISPERSION

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Journal of Hydrodynamics 1993年第3期5卷 55-64页

作者： liu yu-lu Shanghai Inst.of Appl.Math.& Mech.,Shanghai Univ.of Tech.,Shanghai 200072,P.R.China

In the earlier stage of dispersion process,the rate of dispersion associated with earlier discharge is relatively large because the memory term extends further back in *** or- der to investigate the early properties of two-dimensional dispersion,we propose the delay-diffu- sion equation as follows: (?)integral from o to ∞(?) (x-integral from n=1 to τ (?),y-integral from n=1 to τ (?),t-τ)dτ=(?) which is based on the equation derived by Smith (1981).The D_(xz),D_(yz),D_(zy),D_(yy) and (?),(?) had been obtained.

关键词： shear dispersion contaminant diffusion analytical solution eigenvalue problem memory

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基于序号索引的空间关联规则挖掘算法

计算机工程 2010年第16期36卷 54-56,59页

作者：刘雨露重庆三峡学院数学与计算机科学学院万州404000

针对空间关联规则挖掘算法的冗余计算问题,提出一种基于序号索引的空间关联规则挖掘算法。该算法适用于挖掘单层横向空间的关联规则,在自底向上和自顶向下的搜索过程中,用定序操作产生序号索引,通过序号索引在双向挖掘过程中修剪重复候... 详细信息

针对空间关联规则挖掘算法的冗余计算问题,提出一种基于序号索引的空间关联规则挖掘算法。该算法适用于挖掘单层横向空间的关联规则,在自底向上和自顶向下的搜索过程中,用定序操作产生序号索引,通过序号索引在双向挖掘过程中修剪重复候选项和删除冗余计算,以提高算法效率。实验结果证明该算法比现有的算法更快速有效。

关键词：空间数据挖掘空间关联规则二进制双向挖掘序号索引

EXPERIMENTAL STUDY OF UNSTEADY CHARACTERISTICS OF TURBULENT MIXING LAYER FLOW OVER AN OPEN STEP AND A SQUARE-EDGED RIB

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Journal of Hydrodynamics 2007年第6期19卷 786-786页

作者： KE Feng Chen Han-ping liu Ying-zheng He You-sheng Wu Ming-lan Zhou Lian-di Tao Ming-de liu yu-lu School of Mechancial Engineering Shanghai Jiaotong University （SJTU） Shanghai 200240 China Fudan University

Spatio-temporal characteristics of the wall-bounded turbulent mixing layer flow over an open step and a square-edged rib were extensively studied in a low-speed wind tunnel. Simultaneous measurements of wall-pressure ... 详细信息

关键词： entrainment turbulent flow unsteady wall pressure fluctuations large-scale vortical structures

Compressive behavior and energy absorption of metal porous polymer composite with interpenetrating network structure

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Transactions of Nonferrous Metals Society of China 2006年第S2期 439-443页

作者： liu yu, GONG Xiao-lu Institut Charles Delaunay, CNRS FRE 2848, LASMIS, UTT 12, rue Marie Curie, BP 2060, 10010 Troyes, France

Interpenetrating phase composites (IPCs) are a new class of composite materials with improved combinations of mechanical and physical properties. This study was performed on a new type of IPC called metal porous polymer composite (MPPC) with an interpenetrating network structure. Aluminum-polypropylene (AI-PE) and Aluminum-epoxy resin (Al-Ep) composites were produced by infiltrating the polymer in the aluminum foam. The composite microstructures were characterized using SEM observation. The compressive behavior and energy absorption characteristics of MPPC were investigated and compared with the aluminum foams. The compressive modulus of composite was compared with the VOIGT-REUSS bounds and HASHIN-SHTRIKMAN (H-S) bounds models. The experimental modulus of compressive tests falls well within the theoretical models.

关键词： MPPC composite micro structure compressive behavior energy modulus