2006 Annual Conference of Chinese Society of Particuology cum Symposium on Particle Technology across Taiwan Straits

The 2006 Annual Conference of Chinese Society of Particuology cum Symposium on Particle Technology across Taiwan Straits, held in Beijing from August 18 to 21, 2006, was hosted by Chinese Society of Particuology and organized jointly by Institute of Process Engineering, CAS, and State Key Laboratory of Heavy Oil Processing, China University of Petroleum. This conference was record-breaking for its attendance by 284 registered participants from across the country, including 47 from …     

Fifth Sino-US Joint Conference of Chemical Engineering

The fifth Sino-US Joint Conference of Chemical Engineering of Chemical Industry & Engineering Society of China and the American Institute of Chemical Engineers, was held at the Fragrant Hill Hotel in     

PERSPECTIVES IN MECHANICS OF HETEROGENEOUS SOLIDS

The Microand Nano-mechanics Working Group of the Chinese Society of Theoretical and Applied Mechanics organized a forum to discuss the perspectives,trends,and directions in mechanics of heterogeneous materials in January 2010.The international journal,Acta Mechanica Solida Sinica,is devoted to all fields of solid mechanics and relevant disciplines in science,technology,and engineering,with a balanced coverage on analytical,experimental,numerical and applied investigations.On the occasion of the 30 th anniversary of Acta Mechanica Solida Sinica,its editor-in-chief,Professor Q.S.Zheng invited some of the forum participants to review the state-of-the-art of mechanics of heterogeneous solids,with a particular emphasis on the recent research development results of Chinese scientists.Their reviews are organized into five research areas as reported in different sections of this paper.§I firstly brings in focus on microand nano-mechanics,with regards to several selective topics,including multiscale coupled models and computational methods,nanocrystal superlattices,surface effects,micromechanical damage mechanics,and microstructural evolution of metals and shape memory alloys.§II shows discussions on multifield coupled mechanical phenomena,e.g.,multi-fields actuations of liquid crystal polymer networks,mechanical behavior of materials under radiations,and micromechanics of heterogeneous materials.In §III,we mainly address the multiscale mechanics of biological nanocomposites,biological adhesive surface mechanics,wetting and dewetting phenomena on microstructured solid surfaces.The phononic crystals and manipulation of elastic waves were elaborated in §IV.Finally,we conclude with a series of perspectives on solid mechanics.This review will set a primary goal of future science research and engineering application on solid mechanics with the effort of social and economic development.     

Structure of nonpremixed reaction zones in numerical isotropic turbulence

Results from direct numerical simulation of low heat release, turbulent nonpremixed reacting flows modeled using single-step reactions with constant and temperature-dependent rate laws are discussed, and compared with laminar predictions. The mixture fraction and its dissipation rate are statistically independent in regions of intense reaction, partially supporting a commonly made assumption in flamelet-based models. In the presence of a finite rate reverse reaction, the reaction zone spans the entire range of mixture fraction. The joint pdf of the reactive scalars evolves to an equilibrium that is dictated by a balance between the reactive and mixing fluxes in composition space. When the temperature-dependent rate law is implemented, strain-induced extinction is observed for a Zel'dovich (modified) number of 10. As the ratio of local flow to chemical time scale is decreased below unity, a larger fraction of the flow field experiences this mode of extinction. The critical turbulent scalar dissipation rate is compared with laminar values and asymptotic predictions.The first two authors express their acknowledgment to the donors of The Petroleum Research Fund, administered by the American Chemical Society for partial support of this work through a type G grant. We also acknowledge the Council for Research and Creative Writing at the University of Colorado for providing partial financial support.     

Velocity fidelity of flow tracer particles

Recent developments concerning the unsteady dynamic forces on a spherical particle at finite Reynolds number are reviewed for solid particles and clean micro-bubble. A particle frequency :response function and an energy transfer function are derived for a solid particle or a contaminated micro-bubble in gas or liquid flow. A simple, unified method for estimating the cut-off frequency, or cut-off size, of a solid particle or a contaminated bubble is developed. Particle motion in isotropic turbulence is examined. Responses of the tracer particle to integral length scale structure, to turbulence energy, and to Taylor micro-scale structure are discussed in terms of the particle turbulence diffusivity, the particle turbulence intensity, and the ensemble average of the second invariant of fluid turbulence deformation tensor evaluated on the particle trajectory.The author is grateful to R. J. Adrian and C. Kent for their encouragement and support in writing this paper. This work is supported by the Engineering Research Center (ERC) for Particle Science and Technology at the University of Florida, the National Science Foundation (EEC-9402989), and industrial partners of ERC.     

On the accuracy of velocity and vorticity measurements with PIV

A number of numerical techniques aimed at improving the accuracy of measurements using the correlation approach in Particle Image Velocimetry, PIV, are proposed and investigated. In this approach the velocity (displacement) is found as the location of a peak in the correlation map. Based on an experimental model the best performing peak finding approaches are selected among different strategies. Second, an algorithm is proposed which minimizes errors on the estimates of vorticity using velocity distributions obtained by means of PIV. The proposed methods are experimentally validated against a flow with known properties. Work supported by NASA Ames Research Center     

Promising Future, yet More Efforts Needed

The Research Collaboration Group on multi-scale methodology and complex systems was financed by the Chinese Academy of Sciences in recognition of the challenge of multi-scale spatio-temporal structure in the 21st-century chemical engineering science with the hope of possible breakthrough and new opportunities through better understanding and correlation of phenomena occurring at different scales.     

A new simple method of implicit time integration for dynamic problems of engineering structures

This paper presents a new simple method of implicit time integration with two control parameters for solving initial-value problems of dynamics such that its accuracy is at least of order two along with the conditional and unconditional stability regions of the parameters. When the control parameters in the method are optimally taken in their regions, the accuracy may be improved to reach of order three. It is found that the new scheme can achieve lower numerical amplitude dissipation and period dispersion than some of the existing methods, e.g. the Newmark method and Zhai’s approach, when the same time step size is used. The region of time step dependent on the parameters in the new scheme is explicitly obtained. Finally, some examples of dynamic problems are given to show the accuracy and efficiency of the proposed scheme applied in dynamic systems. The project supported by the National Key Basic Research and Development Foundation of the Ministry of Science and Technology of China (G2000048702, 2003CB716707), the National Science Fund for Distinguished Young Scholars (10025208), the National Natural Science Foundation of China (Key Program) (10532040), the Research Fund for Oversea Chinese (10228028). The English text was polished by Keren Wang.     

Prefacein：in dedication to Professors Yong Jin and Zhiqing Yu

This special issue of China PARTICUOLOGY is dedicated to Professors Yong Jin and Zhiqing Yu of Tsinghua University, China, to celebrate over five decades of their careers in chemical engineering research and education. Prof. Jin graduated in 1959 from Ural Polytechnic College in Svivdelovsk in the former USSR and then completed his post-graduate studies in Tianjin University in China in 1960. Thereafter, he taught at the Chinese University of Science and Technology for 13 years before joining Tsinghua University in 1973. Prof. Yu graduated in 1956 from Tianjin University in China and joined Tsinghua University thereafter. Between 1957 and 1959, Prof. Yu undertook more studies in Moscow Mendeleev Institute of Chemical Technology in the former USSR. During the 1970s, Professors Jin and Yu jointly created the Reaction Engineering Program in the Department of Chemical Engineering at Tsinghua University, which later became one of the largest fluidization research groups in the world, known as FLOTU - Fluidization Laboratory of Tsinghua University.     

Reliability analysis of FRP laminated plates with consideration of both initial imperfection and failure sequence

A probabilistic progressive failure analyzing method is applied to estimating the reliability of a simply supported laminated composite plate with an initial imperfection under bi-axial compression load. The initial imperfection and the strength parameters are considered as random variables. Ply-level failure probability is evaluated by the first order reliability method (FORM) together with the Tsai-Wu strength criterion and Tan criterion. Current stresses in the laminated structure are calculated by the classical lamination theory with the stiffness modified based on the last step ply failure. Probabilistically dominant ply-level failure sequences leading to overall system failure are identified, based on which the system failure probability is estimated. A numerical example is presented to demonstrate the methodology proposed. Through parameter studies it is shown that the deviation of the initial imperfection and some of the strength parameters largely influence the system reliability. Project supported by the Scientific Research Foundation for Returned Overseas Chinese Scholars, State Education Ministry, and the Research Foundation of Huazhong University of Science and Technology.     

Algorithms for fully automated three-dimensional particle tracking velocimetry

A three-dimensional Particle Tracking Velocimetry (3-D PTV) technique has been developed to provide time-resolved, three-dimensional velocity field measurements throughout a finite volume. This technique offers many advantages for fundamental research in turbulence and applied research in areas such as mixing and combustion. The data acquired in 3-D PTV is a time sequence of stereo images of flow tracer particles suspended in the fluid. In this paper, the implementation of the technique is discussed in detail, as well as the results of an extensive statistical investigation of the performance of the algorithms. The technique has been optimized to allow fully automatic processing of long sequences of image pairs in a computationally efficient manner, hereby providing a viable, practical tool for the study of complex flows.List of symbols x, y, z Particle position - u, v, w Particle velocity This work was supported by a grant from Ford Motor Company, Powertrain Research Department. Their support is gratefully acknowledged.     

Propagation of a thermal detonation wave in a water-corium system

The problem of the unsteady propagation of a thermal detonation wave in a high-temperature-melt-water system up to the steady-state regime is considered on the basis of the three-dimensional and three-temperature vapor explosion model. The basic laws of wave evolution are analyzed and the wave structure is studied. Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 4, pp. 115–125, July–August, 2000. The work was supported by the Russian Foundation for Basic Research (project No. 98-02-17766) and the International Science and Technology Center (project No. 408).     

Flow statistics in plate and shell heat exchangers measured with PTV

Particle tracking velocimetry (PTV) measurements have provided inner flow features within plate and shell heat exchangers (PSHE). Measurements have been performed at Reynolds number 3450, based on the bulk velocity and the PSHE geometry at the channel mid-section. Particle trajectories have been measured. Organized flow features prevail in the channel inlet, whereas a highly turbulent flow field occurs at the channel outlet. A recirculation zone characterizes the turbulent flow field at the outlet. Gravity has been shown not to affect flow and heat transfer at this Reynolds number. The mean velocity profile is non-uniform at a given channel cross section. Friction factors developed for Plate Heat Exchanger (PHE) applied to the PSHE geometry with the bulk velocity at the channel mid-plane were found appropriate for design purposes. Furthermore, friction factor, Nusselt number and forces due to shear stresses were locally estimated for the whole channel area. Potential break-down locations have been identified.     

应用PIV技术测试涡旋波流场

涡旋波流动作为一种特殊的流动现象,可以使流体在相对较宽的槽道中产生较强的波动和对流混合,从而在小Re数条件下起到强化传质的效果。本文利用PIV流场显示技术,对振荡流在非对称槽道中所形成的涡旋波的产生机理和发展规律进行了实验研究和定量分析,测得了涡旋波流场的速度矢量图,阐明了涡旋波流场周期性变化的特点。分析了Re数和St数对涡旋波流动的影响,并得出了旋涡涡心位置以及涡心处涡量的动态变化规律。     

Interpretation of PIV autocorrelation mesurements in complex particle-laden flows

Particle image velocimetry (PIV) was used to measure instantaneous and average particle velocity fields near the stagnation zone of a particle-laden impinging air jet. The results were compared with Lagrangian particle tracking measurements. Ensemble averages from the two methods agree well except in regions where particles have different histories, and a specific trajectory is dominant but not exclusive. The PIV autocorrelation method loses information regarding non-dominant particle trajectories. Thus, although instantaneous PIV measurements yield the dominant particle velocities correctly, the averaged measurements are biased in some regions.This work was supported by the Electric Power Research Institute under Contract RP 8034-01. We thank the 3M Corporation for their generous materials support.     

Particle size characterization by ultrasonic attenuation spectra

This paper contributes to extracting information from signals of broadband ultrasonic attenuation spectrum for effective utilization in particle size characterization. The single particle scattering model and the coupled-phase model are formulated simultaneously, the relationship between particle size distribution and ultrasonic spectrum is established, and a convergence criterion for calculation is quantified. Demonsa'ation inversion by the optimum regularization factor method is carded out to yield typical numerical results for discussion. With the experimental set-up developed by the Institute of Particle and Two-Phase Flow Measurement (IPTFM) at the University of Shanghai for Science and Technology, sand sediment particle size is measured by attenuation spectrum and analyzed using the above inversion algorithm and theoretical models. To validate the proposed ultrasonic spectrum particle sizing method, results are compared with those obtained by microscopy.     

A spatiotemporal decomposition of a fully inhomogeneous turbulent flow field

The three-dimensional orthogonal spatial modes and their temporal counterparts have been extracted from a large-eddy simulation of turbulent flow over a surface-mounted cube, using a space-time symmetric version of proper orthogonal decomposition (POD), proposed by Aubry et al. (1991). A relatively small domain of interest, located immediately above the top face of the flow obstacle, has been selected for the application of POD. Within that volume of interest, time records of the velocity field have been sampled at 6000 locations simultaneously. The space-time duality of POD can be demonstrated by deriving two alternative eigenvalue problems for either the orthogonal spatial modes or the orthogonal temporal modes. For a particular case, the choice between the two alternatives can be done on the basis of computational convenience and of data-storage requirements. The results show that the first spatiotemporal mode can be identified with the mean flow. The second spatiotemporal mode is dominated by the alternating vortex shedding from the side edges of the flow obstacle. A Fourier analysis of the second temporal mode leads to a Strouhal number of S=0.125 which corresponds to the measured Strouhal number for the vortex shedding (Martinuzzi, 1992). The third and the fourth spatiotemporal modes are connected with the rolls created at the horizontal leading edge of the cube. For the flow field investigated, the dual space-time point of view of POD is rather realistic in the sense that the first four spatiotemporal modes can actually be observed in the flow.This work is currently supported by the German Research Society (DFG), Priority Research Program, Project No. We 705/3 (Wengle /Römer). We also gratefully acknowledge the support by the Universität der Bundeswehr München (UniBwM) and by the Leibniz Computing Center of the Bavarian Academy of Sciences (LRZ).     

Incompressibility approximation in magnetohydrodynamics

With reference to the problem of the development of tiring instability in a helical geometry it is shown that, as distinct from traditional gas dynamics, in plasma dynamics the incompressibility approximation cannot generally be used for describing slow flows. This is associated with the fact that several types of disturbances whose interaction results in possible density variations of the order of unity can propagate in plasma. Novosibirsk. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 145–149, January–February, 1999. The work was carried out with partial support from the Russian Foundation for Basic Research (project No. 96-01-01572) and the German Research Society (DFG).     

Mapping closure approximation for reactive scalars in random flows

The Mapping Closure Approximation (MCA) approach is developed to describe the statistics of both conserved and reactive scalars in random flows. The statistics include Probability Density Function (PDF), Conditional Dissipation Rate (CDR) and Conditional Laplacian (CL). The statistical quantities are calculated using the MCA and compared with the results of the Direct Numerical Simulation (DNS). The results obtained from the MCA are in agreement with those from the DNS. It is shown that the MCA approach can predict the statistics of reactive scalars in random flows. The project supported by the National Committee of Science and Technology, China, under the Special Funds for Major Basic Research Project (G2000077305 and G1999032801), and the National Natural Science Foundation of China (10325211)