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Large-Eddy Simulations of turbulent flows with lattice Boltzmann dynamics and dynamical system sub-grid models

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science china(Technological sciences) 2009年第3期52卷 670-679页

作者： GUAN Hui1 & WU ChuiJie2.1 research center for {2. dynamics, pla University of science and technology, nanjing 2.1101, china 2.School of Aeronautics and Astronautics, Dalian University of technology, Dalian 11602., china research center for {2. dynamics PLA University of Science and Technology Nanjing China School of Aeronautics and Astronautics Dalian University of Technology Dalian China

In this paper, two sub-grid scale (SGS) models are introduced into the Lattice Boltzmann Method (LBM), i.e., the dynamics SGS model and the dynamical system SGS model, and applied to numerically solving three-dimensional high Re turbulent cavity flows. Results are compared with those obtained from the Smagorinsky model and direct numerical simulation for the same cases. It is shown that the method with LBM dynamics SGS model has advantages of fast computation speed, suitable to simulate high Re turbulent flows. In addition, it can capture detailed fine structures of turbulent flow fields. The method with LBM dynamical system SGS model dose not contain any adjustable parameters, and can be used in simulations of various complicated turbulent flows to obtain correct information of sub-grid flow field, such as the backscatter of energy transportation between large and small scales. A new average method of eliminating the inherent unphysical oscillation of LBM is also given in the paper.

关键词： Large-Eddy Simulation Lattice Boltzmann Method dynamics sub-grid scale model dynamical system sub-grid scale model parallel computation

A method of constructing a database-free optimal dynamical system and a global optimal dynamical system

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science china(Physics,Mechanics & Astronomy) 2008年第7期51卷 905-915页

作者： WU ChuiJie1? & WANG Liang2.1 State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of technology, Dalian 11602., china {2., School of science, pla University of science and technology, nanjing 2.1101, china State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology Dalian China research center for {2. dynamics School of Science PLA University of Science and Technology Nanjing China

In this paper, to overcome the drawbacks of POT which minimize the reminder, not only the optimal functional with minimal residual is put forward, but also the method of global optimization is used. Under the condition of large reminder, the optimal bases can also be obtained through the method of POTres without the approaching of initial conditions. In addition, compared with local optimization, the advantage of global optimization is remarkable. On the one hand, we can expect that the dynamical system based on the global optimal bases will include more information than the ones based on the local optimal bases, since the global optimal bases are much more precise than the local optimal bases. On the other hand, from the point of view of error, the global optimal bases are independent of the choice of the object functional and the initial bases.

关键词： dynamical system residual global optimization

Large-eddy simulation of formation of three-dimensional aeolian sand ripples in a turbulent field

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science china(Physics,Mechanics & Astronomy) 2008年第8期51卷 945-960页

作者： WU ChuiJie1,WANG Ming2.& WANG Liang3 1 State Key Laboratory of Structural Analysis for Industrial Equipment,Dalian University of technology,Dalian 11602.,china 2.Yellow River Institute of Hydraulic {2.,Zhengzhou 450003,china 3 {2. center for fluid dynamics,science School,pla University of science and technology,{12.,china State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology Dalian China Yellow River Institute of Hydraulic research Zhengzhou China research center for {2. dynamics Science School PLA University of Science and Technology Nanjing China

With the method of large-eddy simulation,the equation of spherule motion and the method of immersed boundary condition,numerical simulations of three-dimen-sional turbulent aeolian motion and the formation of sand ripples under three-di-mensional turbulent wind and the mutual actions of saltation and creeping motion were carried out. The resulting sand ripples have the form that is flat on the upwind side and steep on the leeward,which is identical to the sand ripples in nature. We also realized the self-restoration process of three-dimensional sand ripples,which shows the correctness of the method of numerical simulation and the models of saltation and creeping. Finally,We analyzed the influence of sand ripples on the three-dimensional turbulent wind field,and found that due to the appearance and development of sand ripples,in the normal direction of ground there exists stronger energy exchange,and moreover,there is close correspondence between the forms of sand ripples and the vorticity close to the ground surface.

关键词： large-eddy simulation equation of spherule motion sand ripples saltation creep

Delayed Hopf bifurcation in time-delayed slow-fast systems

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science china(Technological sciences) 2010年第3期53卷 656-663页

作者： ZHENG YuanGuang1 & WANG ZaiHua1,2.1 Institute of Vibration Engineering research,nanjing University of Aeronautics and Astronautics,nanjing 2.0016,china 2.Institute of science,pla University of science and technology,nanjing 2.1101,china Institute of Vibration Engineering research Nanjing University of Aeronautics and Astronautics Nanjing China Institute of science PLA University of Science and Technology Nanjing China

This paper presents an investigation on the phenomenon of delayed bifurcation in time-delayed slow-fast differential *** the two delayed's have different *** delayed bifurcation means that the bifurcation does not happen immediately at the bifurcation point as the bifurcation parameter passes through some bifurcation point,but at some other point which is above the bifurcation point by an obvious *** a time-delayed system,the evolution of the system depends not only on the present state but also on past *** this paper,the time-delayed slow-fast system is firstly simplified to a slow-fast system without time delay by means of the center manifold reduction,and then the so-called entry-exit function is defined to characterize the delayed bifurcation on the basis of Neishtadt's *** shows that delayed Hopf bifurcation exists in time-delayed slow-fast systems,and the theoretical prediction on the exit-point is in good agreement with the numerical calculation,as illustrated in the two illustrative examples.

关键词： time delay delayed bifurcation Hopf bifurcation slow-fast systems exit-point entry-exit function

Energy dispersion of complex non-isolated vortices

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Chinese science Bulletin 2011年第25期56卷 2713-2717页

作者： LUO ZheXian 1,2.1 Key Laboratory of Meteorological Disaster of Ministry of Education, nanjing University of Information science and {2., nanjing 2.0044, china 2.Wuxi research center of Environmental science and {2., Wuxi 2.4031, china Key Laboratory of Meteorological Disaster of Ministry of Education Nanjing University of Information Science and Technology Nanjing China Wuxi research center of Environmental {2. and technology Wuxi China

Energy dispersion is a fundamental scientific problem in the study of natural disasters such as typhoons, heavy rain and earthquakes. The problem has been addressed by both multi-discipline research and forecast studies. The dynamics of isolated circular vortex energy dispersion have been solved. However, the disastrous results of typhoons and heavy rain often occur due to non-isolated circular vortices, the dynamics of which are explored in this paper. The energy dispersion characteristics of non-isolated vortices with complex structural patterns are examined using a linearized nondivergent barotropical vorticity equation model. In the initial field, a tropical cyclone (TC) vortex and a meso-scale vortex coexist, forming a complex structural pattern. An analytic solution based on a Fourier transform and simulations using a two-dimensional model show the following. (1) A wave train of TC-G-D may be created by the energy dispersion where the line connecting the three member centers of the wave train is parallel to the x axis in the case of an initial TC vortex without a meso-scale vortex. (2. A wave train of TC-G-D may also be created by energy dispersion. However, the line connecting the three member centers of the wave train would no longer be parallel to the x axis. Instead, they would form a triangle in the presence of the initial TC vortex with the meso-scale vortex. (3) There is a nonlinear relationship between the initial intensity of the meso-scale vortex and the base angle of the triangle. These results have the potential to be applied in the field of typhoon forecasting.

关键词：能量色散非隔离式旋涡非线性关系中尺度涡台风预报结构模式傅立叶变换

Experimental study on fire smoke movement in a multi-floor and multi-room building

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science china(Technological sciences) 2005年第3期48卷 292-304页

作者： ZHONG Maohua 1, 2., LI Peide 2., LIU Tiemin 1 , WEI Xing 1, 2.& LIAO Guangxuan 2.1. National center of Safety science and {2., State Administration of Work Safety, Beijing 10002., china 2. State Key Laboratory of Fire science, University of science and {2. of china, Hefei 2.002., china National center of Safety science and {2. State Administration of Work Safety Beijing China State Key Laboratory of Fire science University of Science and Technology of China Hefei China

Fire smoke movement of multi-floor and multi-room (MFMR) fire was studied at the model test building in State Key Laboratory of Fire science (SKLFS). The ingredient, temperature, air pressure difference and air velocity of smoke were measured and analyzed. Meanwhile, the hazard of smoke ingredient to exposed occupants was analyzed based on the national standard, Occupational Exposure Limit for Hazardous Agents in the Workplace (GBZ2.2.02.. The experimental results showed that the maximum temperature difference in MFMR fire was located along the vertical height from the fire source. With the spreading and diffusion of smoke, the temperature of smoke layer would tend to be no difference. In the fire of woodpile and kerosene, the main smoke ingredients such as SO 2., CO and CO 2.would first exceed human’s average physiological limit, while smoke ingredients such as NO and NO 2.would come behind. Because of the higher fluctuation range and frequency of air pressure difference of smoke in multi-layer building fire, the fire smoke would spread around everywhere of the passageway and made the human evacuation more difficult.

关键词： multi-floor and multi-room,fire experiment,smoke spread,smoke toxicity.

Study on the unified algorithm for three-dimensional complex problems covering various flow regimes using Boltzmann model equation

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science china(Physics,Mechanics & Astronomy) 2009年第1期52卷 124-138页

作者： LI ZhiHui1,2.& ZHANG HanXin1 1 National Laboratory for Computational fluid dynamics, Beijing 100083, {2. 2.{2. Aerodynamics research and Development center, Hypervelocity Aerodynamics Institute, Mianyang 62.000, {2. National Laboratory for Computational fluid dynamics Beijing China china Aerodynamics {2. and Development center Hypervelocity Aerodynamics Institute Mianyang China

The Boltzmann simplified velocity distribution function equation describing the gas transfer phenomena from various flow regimes will be explored and solved numerically in this study. The discrete velocity ordinate method of the gas kinetic theory is studied and applied to simulate the complex multi-scale flows. Based on the uncoupling technique on molecular movement and colliding in the DSMC method, the gas-kinetic finite difference scheme is constructed to directly solve the discrete velocity distribution functions by extending and applying the unsteady time-splitting method from computational fluid dynamics. The Gauss-type discrete velocity numerical quadrature technique for different Mach number flows is developed to evaluate the macroscopic flow parameters in the physical space. As a result, the gas-kinetic numerical algorithm is established to study the three-dimensional complex flows from rarefied transition to continuum regimes. The parallel strategy adapted to the gas-kinetic numerical algorithm is investigated by analyzing the inner parallel degree of the algorithm, and then the HPF parallel processing program is developed. To test the reliability of the present gas-kinetic numerical method, the three-dimensional complex flows around sphere and spacecraft shape with various Knudsen numbers are simulated by HPF parallel computing. The computational results are found in high resolution of the flow fields and good agreement with the theoretical and experimental data. The computing practice has confirmed that the present gas-kinetic algorithm probably provides a promising approach to resolve the hypersonic aerothermodynamic problems with the complete spectrum of flow regimes from the gas-kinetic point of view of solving the Boltzmann model equation.

关键词： Boltzmann model equation kinetic theory velocity distribution function discrete velocity ordinate technique hypersonic flow parallel computing numerical methods

Numerical simulations of self-propelled swimming of 3D bionic fish school

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science china(Technological sciences) 2009年第3期52卷 658-669页

作者： WU ChuiJie1 & WANG Liang2.1 State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of technology, Dalian 11602., china {2., People’s Liberation Army University of science and technology, nanjing 2.1101, china State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology Dalian China research center for {2. dynamics People’s Liberation Army University of Science and Technology Nanjing China

Numerical simulations of self-propelled swimming of a three dimensional bionic fish and fish school in a viscous fluid are carried out. This is done with the assistance of a parallel software package produced for 3D moving boundary problems. This computational fluid {2. package combines the adaptive multi-grid finite volume method, the immersed boundary method and VOF (volume of fluid) method. By using the package results of the self-propelled swimming of a 3D bionic fish and fish school in a vis- cous fluid are obtained. With comparison to the existing experimental measurements of living fishes, the predicted structure of vortical wakes is in good agreement with the measurements.

关键词： adaptive multi-grid immersed boundary method self-propelled swimming fish school 3D bionic fish

Molecular dynamics simulation study on zwitterionic structure to maintain the normal conformations of Glutathione

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science china Chemistry 2007年第5期50卷 660-664页

作者： YAN Han1, ZHU HaoMiao2.& SHEN Jian1,2.1 Jiangsu research center of Surface and Interface Chemical Engineering and {2., nanjing University, nanjing 2.0093, china 2.Jiangsu Engineering research center for Bio-medical function Materials, nanjing Normal University, nanjing 2.0097, china Jiangsu research center of Surface and Interface Chemical Engineering and {2. Nanjing University Nanjing China Jiangsu Engineering research center for Bio-medical function Materials Nanjing Normal University Nanjing China

Molecular dynamics simulations were applied to normal conformational Glutathione (GSH) and GSH over zwitterionic and hydrophobic surfaces respectively. Conformational analysis of GSH during the simulation time on RMSD, conformational flexibility and dihedral distribution were performed. The re- sults showed that zwitterionic structure maintains the normal conformations of GSH to a better extent, which should be a first good proof of the hypothesis of "maintain of normal structure".

关键词： protein-surface interactions, molecular dynamics simulation, zwitterionic structure, Glutathione, conformational changes, antithrombotic material