检索结果-南通市图书馆

Unified stability condition for particulate and aggregative fluidization—Exploring energy dissipation with direct numerical simulation

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Particuology 2013年第2期11卷 232-241页

作者： Min Wei limin Wang jinghai li The EMMS Group State Key Laboratory of Multiphase Complex SystemsInstitute of Process EngineeringChinese Academy of Sciences University of Chinese Academy of Sciences

Fully resolved simulations of particulate and aggregative fluidization systems are performed suc-cessfully with the so-called combined lattice Boltzmann method and time-driven hard-sphere model （LBM-TDHS）. In this method, the discrete particle phase is described by time-driven hard-sphere model, and the governing equations of the continuous fluid phase are solved with lattice Boltz-mann method. Particle-fluid coupling is implemented by immersed moving boundary method. Time averaged flow structure of the simulated results show the formation of core-annulus structure and sigmoid distribution of voidage in the axial direction, which are typical phenomena in fluidization systems. Combining the results of the simulation, the energy consumption Nst for suspending and transporting solids is calculated from the direct numerical simulation （DNS） of fluidization, and the stability criterion Nst/NT = rain proposed in EMMS/bubbling model is verified numerically. Further-more the numerical results show that the value of Nst/NT in particulate fiuidization is much higher than that in aggregative fluidization, but Nst/NT = rain is effective for both particulate and aggregative fluidization.

关键词： Direct numerical simulation Fluidization Stability condition Lattice-Boltzmann method Time-driven hard-sphere model

Macro-scale pseudo-particle modeling for particle-fluid systems

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2001年第18期46卷 1503-1507,1585页

作者： Wei Ge jinghai li Chinese Acad Sci Inst Proc Engn Multiphase React Lab Beijing 100080 Peoples R China

Pseudo-particle modeling (PPM) is a particle method (PM) proposed in 1996. Though it is effective for the simulation of microscopic particle-fluid systems, its application to practical systems is still limited by computational cost. In this note, we speed up the computation by using a combination of weighted averaging with finite difference techniques to upgrade the particle interactions to a fluid element level, which conforms to the Navier-Stokes equation. The approach, abbreviated to MaPPM, is then applied to the problem of one-dimensional Poiseuille flow with a quantitative comparison to the results of another related PM--smoothed particle hydrodynamics (SPH), where the accuracy and efficiency of MaPPM is found to be much better than that of SPH. Flows around a cylinder and multiple freely moving particles are also simulated with the new model, resulting in reasonable flow pattern and drag coefficient. The convergence and robustness of the algorithm prove promising.

关键词： smoothed particle hydrodynamics computational fluid dynamics particle method multi-phase flow pseudo-particle modeling.

Molecular dynamics simulation of complex multiphase flow on a computer cluster with GPUs

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2009年第3期52卷 372-380页

作者： CHEN FeiGuo GE Wei li jinghai State Key Laboratory of Multi-Phase Complex Systems Institute of Process EngineeringChinese Academy of SciencesBeijing 100190China Graduate University of Chinese Academy of Sciences Beijing 100039China

Compute Unified Device Architecture (CUDA) was used to design and implement molecular dynamics (MD) simulations on graphics processing units (GPU). With an NVIDIA Tesla C870, a 20-60 fold speedup over that of one core of the Intel Xeon 5430 CPU was achieved, reaching up to 150 Gflops. MD simulation of cavity flow and particle-bubble interaction in liquid was implemented on multiple GPUs using a message passing interface (MPI). Up to 200 GPUs were tested on a special network topology, which achieves good scalability. The capability of GPU clusters for large-scale molecular dynamics simulation of meso-scale flow behavior was, therefore, uncovered.

关键词： multiphase flow molecular dynamics CUDA GPU parallel computing

Pattern formation in particle systems driven by color field

在线全文

学校读者我要写书评

暂无评论

Particuology 2008年第6期6卷 515-520页

作者： Xiaoxing liu Huabiao Qi Wei Ge jinghai li State Key Lab of Multi-phase Complex Systems Institute of Processing Engineering Chinese Academy of Sciences PO BOX 353 Beijing 100080 China Graduate University of the Chinese Academy of Sciences Beijing 100049 China

The structural evolution of systems with two kinds of particles driven in opposite directions, i.e., driven by a color field, is investigated by molecular dynamics simulations. Gaussian thermostat, a common treatment to restrict the thermal velocity of the particles in the systems, has been used so as to account for the dissipation of heat and allow the system to reach a steady state. It has been found that with the increase of the strength of driving force （F）, the system undergoes an obvious structural transition from an initially random mixing state to a state characterized by separate lanes and in each lane only one kind of particles exists. The analysis shows that the reason for the formation of lane structure is not only the increase of F but also the variation of particle friction coefficient. While using Gaussian thermostat the particle friction coefficient becomes a function of F. Increasing F leads to high particle friction coefficient and inevitably results in lane formation for strong enough driving force. When lifting the effect of F on friction coefficient and choosing a constant friction coefficient, our results show that for a given F there always exists a critical value of friction coefficient higher than which the system will develop into lane structure.

关键词： Color field Molecular dynamics (MD) Simulation Lane formation Driven system

Focusing on the meso-scales of multi-scale phenomena-In search for a new paradigm in chemical engineering

在线全文

学校读者我要写书评

暂无评论

Particuology 2010年第6期8卷 634-639页

作者： jinghai li Wei Ge Wei Wang Ning Yang The EMMS Group State Key Laboratory of Multiphase Complex Systems Institute of Process Engineering Chinese Academy of Sciences Beijing 100190 China

To celebrate the 90th birthday of Professor Mooson Kwauk, who supervised the multi-scale research at this Institute in the last three decades, we dedicate this paper outlining our thoughts on this subject accumulated from our previous studies. In the process of developing, improving and extending the energy- minimization multi-scale （EMMS） method, we have gradually recognized that meso-scales are critical to the understanding of the different kinds of multi-scale structures and systems. It is a common challenge not only for chemical engineering but also for almost all disciplines of science and engineering, due to its importance in bridging micro- and macro-behaviors and in displaying complexity and diversity. It is believed that there may exist a common law behind meso-scales of different problems, possibly even in different fields. Therefore, a breakthrough in the understanding of meso-scales will help materialize a revolutionary progress, with respect to modeling, computation and application.

关键词： Meso-scale Multi-scale Complex system EMMS Multi-phase High performance computation

Mesoscience: exploring the common principle at mesoscales

在线全文

学校读者我要写书评

暂无评论

National Science Review 2018年第3期5卷 321-326页

作者： Wenlai Huang jinghai li Peter P.Edwards State Key Laboratory of Multiphase Complex Systems Institute of Process Engineering Chinese Academy of Sciences Department of Chemistry University of Oxford

BACKGROUND OF THE EMERGING MESOSCIENCE In studying a complex system in science,engineering or society,we usually observe its macroscale(system-scale)behavior first,then go deep into mechanisms at the microscale(unit-scale)and finally try to correlate these two scales to reach a complete ***,it is increasingly recognized that correlating these two scales is quite difficult,and some common principles are inevitably missing in between these two extrema[1,2].

关键词： Mesoscience exploring the common principle at mesoscales

Virtual experimentation through 3D full-loop simulation of a circulating fluidized bed

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Particuology 2008年第6期6卷 529-539页

作者： Nan Zhang Bona Lu Wei Wang jinghai li State Key Laboratory of Multiphase Complex Systems Institute of Process Engineering Chinese Academy of Sciences Beijing 100190 China Graduate University of the Chinese Academy of Sciences Beijing 100049 China

Eulerian granular multiphase model with a drag coefficient correction based on the energy-minimization multi-scale （EMMS） model was used to simulate a semi-industry scale circulating fluidized bed （CFB）. Three-dimensional （3D）, time-dependent simulation of a full-loop CFB revealed that the axial profiles of cross-sectionally averaged solid volume fraction, and the radial profiles of solid axial velocity and solid volume fraction were in reasonable agreement with experimental data. Based on this agreement, database derived from experiments not yet accomplished was replenished with such simulations, and fluid regime diagrams and pressure balance around the CFB loop were derived accordingly. This work presents an integrated viewpoint on CFB and unfolds a fresh paradigm for CFB modeling, which can be expected to help resolve certain issues long in dispute but bard for experiments.

关键词： CFD Circulating fluidized bed Multiphase flow Simulation Choking Cluster

General approach for discrete simulation of complex systems

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2002年第14期47卷 1172-1175,1233页

作者： Wei Ge jinghai li Chinese Acad Sci Inst Proc Engn Beijing 100080 Peoples R China

By applying a general algorithm to different particle models, i.e. molecular dynamic (MD) and macro-scale pseudo-particle models (MaPPM), two physical phenomena of distinct nature and scale differences, i.e. the mutual diffusion of two gases and the instability on the interface between two fluids, are simulated successfully. It demonstrates the possibility that the general algorithms of good parallelism and software of modular architecture can be established for complex physical systems based on the particle methods (PMs), which will thereby develop into a mainstream approach as finite element (FE) and finite difference (FD) approaches.

关键词： complex systems parallel computation particle methods pseudo-particle modeling.

A stability condition for turbulence model:From EMMS model to EMMS-based turbulence model

在线全文

学校读者我要写书评

暂无评论

Particuology 2014年第5期12卷 142-154页

作者： lin Zhang Xiaoping Qiu limin Wang jinghai li The EMMS Group State Key Laboratory of Multiphase Complex SystemsInstitute of Process EngineeringChinese Academy of Sciences University of Chinese Academy of Sciences

The closure problem of turbulence is still a challenging issue in turbulence modeling. In this work, a stability condition is used to close turbulence. Specifically, we regard single-phase flow as a mixture of turbulent and non-turbulent fluids, separating the structure of turbulence. Subsequently, according to the picture of the turbulent eddy cascade, the energy contained in turbulent flow is decomposed into different parts and then quantified. A turbulence stability condition, similar to the principle of the energy-minimization multi-scale （EMMS） model for gas-solid systems, is formulated to close the dynamic constraint equa- tions of turbulence, allowing the inhomogeneous structural parameters of turbulence to be optimized. We name this model as the ＂EMMS-based turbulence model＂, and use it to construct the corresponding turbulent viscosity coefficient. To validate the EMMS-based turbulence model, it is used to simulate two classical benchmark problems, lid-driven cavity flow and turbulent flow with forced convection in an empty room, The numerical results show that the EMMS-hased turbulence model improves the accuracy of turbulence modeling due to it considers the principle of compromise in competition between viscosity and inertia.

关键词： Stability condition Mathematical modeling Turbulence EMMS Hydrodynamics Computational fluid dynamics