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Large-eddy simulations and vortex structures of turbulent jets in crossflow

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Science china(Physics,Mechanics & Astronomy) 2007年第1期50卷 118-132页

作者： GUAN Hui1,2 & WU ChuiJie2 1 School of Mechanical and Power Engineering,East china university of Science and technology,Shanghai 20023.,china 2 research center for fluid dynamics,pla university of Science and technology,nanjing 211101,china 1. School of Mechanical and Power Engineering East China University of Science and Technology Shanghai 200237 China 2. research center for fluid {3. PLA University of Science and Technology Nanjing 211101 China

Using the method of large-eddy simulation, the 3.dimensional turbulent jets in crossflow with stream-wise and transverse arrangements of nozzle are simulated, emphasizing on the dynamical process of generation and evolution of vortex structures in these flows. The results show that the basic vortex structures in literatures, such as the counter-rotating vortex pair, leading-edge vortices, lee-side vortices, hanging vortices, kidney vortices and anti-kidney vortices, are not independent physical substances, but local structures of the basic vortex structure of turbulent jets in crossflow-the 3.D stretching vortex rings originating from the orifice of the nozzle, which is discovered in this study. Therefore, the most important large-scale structures of turbulent jets in crossflow are unified to the 3.D vortex rings which stretch and twist in stream-wise and swing in transverse directions. We also found that the shedding frequencies of vortex rings are much lower than the one corresponding to the appearance of leading-edge and lee-side vortices in the turbulent jets.

关键词： turbulent jet in crossflow coherent structure large-eddy simulation

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 116024, china {3., School of Science, pla university of Science and technology, nanjing 211101, china 1. State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology Dalian 116024 China 2. research center for fluid {3. School of Science PLA University of Science and Technology Nanjing 211101 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 116024,china 2 Yellow River Institute of Hydraulic {3.,Zhengzhou 450003.china 3.{3. center for fluid dynamics,Science School,pla university of Science and technology,nanjing 211101,china State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology Dalian 116024 China Yellow River Institute of Hydraulic research Zhengzhou 450003 China research center for fluid {3. Science School PLA University of Science and Technology Nanjing 211101 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 210016,china 2 Institute of Science,pla university of Science and technology,nanjing 211101,china 1. Institute of Vibration Engineering research Nanjing University of Aeronautics and Astronautics Nanjing 210016 China2. Institute of Science PLA University of Science and Technology Nanjing 211101 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

Adsorption of surfactants onto acrylic ester resins with different pore size distribution

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Science china Chemistry 2006年第5期49卷 445-453页

作者： YANG Weiben1,2,3.LI Aimin1,3.CAI Jianguo1,3.MENG Guanhua1,3.& ZHANG Quanxing1,3.1. State Key Laboratory of Pollution Control and Resource Reuse,School of the Environment,nanjing university,nanjing 210093.{3. 2. nanjing College of Chemical technology,nanjing 210048,{3. 3. Jiangsu Engineering & technology research center for Organic Toxicant Control and Resource Reuse,nanjing 21003.,{3. 1. State Key Laboratory of Pollution Control and Resource Reuse School of the Environment Nanjing University Nanjing 210093 China 2. nanjing College of Chemical technology Nanjing 210048 China 3. Jiangsu Engineering & technology research center for Organic Toxicant Control and Resource Reuse Nanjing 210038 China

In this study, a series of acrylic ester resins with different pore size distribution were prepared successfully by varying the type and the amount of pore-forming agents. In order to inves-tigate the adsorption behavior and mechanism of surfactants on acrylic ester resins, three kinds of surfactants were utilized as adsorbates that were sodium 6-dodecyl benzenesulfonate (6-NaDBS), sodium 1-dodecyl benzene sulfonate (1-NaDBS) and sodium 1-dodecyl sulfonate, respectively. It was observed that the surface area was available in a particular pore size and an appropriate pore size of resins appeared to be more important for the adsorption of surfactants. As compared to commercial acrylic ester resins XAD-7 and HP2MG, 50# and 3.# resins exhibited more excellent adsorption properties toward 1-NaDBS and 6-NaDBS. The experimental equilibrium data were fitted to the Langmuir, and double-Langmuir models. Two models provided very good fittings for all resins over the temperature range studied. The investigation indicated that electrostatic attraction and hydrogen bond between resins and surfactants were the main forces and had an obvious effect on adsorption proc-ess.

关键词： acrylic ester resin, surfactant, adsorption, pore size distribution, isotherm.

An adaptive version of ghost-cell immersed boundary method for incompressible flows with complex stationary and moving boundaries

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Science china(Physics,Mechanics & Astronomy) 2010年第5期53卷 923-932页

作者： WANG Liang1 & WU ChuiJie2,3.1 School of Science,pla university of Science and technology,{3.,china 2 State Key Laboratory of Structural Analysis for Industrial Equipment,Dalian university of technology,Dalian 116024,china 3.School of Aeronautics and Astronautics,Dalian university of technology,Dalian 116024,china 1. School of Science PLA University of Science and Technology Nanjing 211101 China2. State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology Dalian 116024 China3. School of Aeronautics and Astronautics Dalian University of Technology Dalian 116024 China

An adaptive version of immersed boundary method for simulating flows with complex stationary and moving boundaries is *** method employs a ghost-cell methodology which allows for a sharp representation of the immersed *** simplify the implementation of the methodology,a volume-of-fluid method is introduced to identify the immersed *** addition,the domain is spatially discretized using a tree-based discretization which is relatively simple to implement a fully flexible adaptive refinement ***,the methodology is validated by comparing it with numerical and experimental results on three cases:(1) the flow passing a circular cylinder at Re=40 and Re=100,(2) a periodic oscillation of a circular cylinder in fluid at rest and(3. the self-propelled fish-like swimming at Re=6400.

关键词： adaptive mesh refinement ghost-cell immersed boundary method moving boundaries

Numerical simulations of self-propelled swimming of 3. 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 116024, china {3., People’s Liberation Army university of Science and technology, nanjing 211101, china State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology Dalian 116024 China research center for fluid {3. People’s Liberation Army University of Science and Technology Nanjing 211101 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 3. moving boundary problems. This computational fluid dynamics 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 3. 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 3. bionic fish

Prediction method for October 2003.solar storm

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Science china(Technological Sciences) 2006年第5期49卷 629-640页

作者： XIE Yanqiong1, 2, 3. WEI Fengsi1, FENG Xueshang1 & ZHONG Dingkun1, 2 1. State Key Laboratory of Space Weather, center for Space Science and Applied research, Chinese Academy of Sciences, Beijing 100080, china 2. Graduate School, Chinese Academy of Sciences, Beijing 10003., china 3. Institute of Meteorology, pla university of Science and technology, nanjing 211101, china State Key Laboratory of Space Weather Center for Space Science Applied research Chinese Academy of Sciences Beijing 100080 China Graduate School Chinese Academy of Sciences Beijing 100039 China Institute of Meteorology PLA University of Science technology Nanjing 211101 China

Aiming at two intense shock events on October 28 and 29, 2003. this paper presents a two-step method, which combines synoptic analysis of space weather ——“observing” and quantitative prediction ——“palpating”, and then uses it to test predictions. In the first step of “observing”, on the basis of observations of the solar source surface magnetic field, interplanetary scintillation (IPS) and ACE spacecraft, we find that the propagation of the shocks is asymmetric relative to the normal direction of their solar sources, and the Earth is located near the direction of the fastest speed and the greatest energy of the shocks. As the two fast ejection shock events, the fast explosion of coronal mass of the extremely high temperature, the strong magnetic field, and the high speed background solar wind are also helpful to their rapid propagation. In the second step of “palpating”, we adopt a new membership function of the fast shock events for the ISF method. The predicted results show that for the onset time of the geomagnetic disturbance, the relative errors between the observational and the predicted results are 1.8% and 6.7%; and for the magnetic disturbance magnitude, the relative errors are 4.1% and 3.1%, re- spectively. Furthermore, the comparison among the predicted results of our two-step method with those of five other prevailing methods shows that the two-step method is advantageous. The results tell us that understanding the physical features of shock propagation thoroughly is of great importance in improving the prediction precision.

关键词： solar storm, interplanetary shock, interplanetary scintillation, two-step method, ISF method.

Absolute scaling law for temperature data in Rayleigh-Benard convection

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Science china(Technological Sciences) 2009年第3期52卷 684-687页

作者： FU Qiang research center of fluid Mechanics, Institute of Science of, People’s Liberation Army {3. of Science and technology, Nan- jing 211101, china research center of fluid Mechanics Institute of Science of People’s Liberation Army University of Science and Technology Nanjing 211101 China

In addition to the hierarchical-structure (H-S) model, this paper further explores the most intensive intermittent structure of Rayleigh-Bénard convection at the high Ra numbers proportional to temperature. With respect to the discovery and by means of the scale, both of Bolgiano, there are two regions of the structure holding the absolute scaling law given by Ching’s paper. Through theoretic analysis of data, this paper indicates that the regions act as two local intensive intermittent structures, by which the statistical absolute scaling performance of region is induced, rather than the statistical result of the entire time series in belief since 1941. In terms of statistical theory, the local structure in fluid, therefore, is the essence governing the absolute scaling performance of region, especially in high intensity.

关键词： Rayleigh-Benard convection Bolgiano scale the most intensive structure absolute scaling law local structure