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Reachable set modeling and engagement analysis of exoatmospheric interceptor

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Chinese Journal of Aeronautics 2014年第6期27卷 1513-1526页

作者： chai hua Liang Yangang Chen Lei Tang Guojin College of Aerospace Science and Engineering National University of Defense Technology

A novel reachable set（RS） model is developed within a framework of exoatmospheric interceptor engagement analysis. The boost phase steering scheme and trajectory distortion mechanism of the interceptor are firstly explored. A mathematical model of the distorted RS is then formulated through a dimension–reduction analysis. By treating the outer boundary of the RS on sphere surface as a spherical convex hull, two relevant theorems are proposed and the RS envelope is depicted by the computational geometry theory. Based on RS model, the algorithms of intercept window analysis and launch parameters determination are proposed, and numerical simulations are carried out for interceptors with different energy or launch points. Results show that the proposed method can avoid intensive on-line computation and provide an accurate and effective approach for interceptor engagement analysis. The suggested RS model also serves as a ready reference to other related problems such as interceptor effectiveness evaluation and platform disposition.

关键词： Engagement analysis Flight dynamics Interception Reachable set Spherical convex hull

A pseudopotential-based multiple-relaxation-time lattice Boltzmann model for multicomponent/multiphase flows

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Acta Mechanica Sinica 2012年第4期28卷 983-992页

作者： Zhen-hua chai Tian-Shou Zhao Department of Mechanical Engineering Hong Kong University of Science and TechnologyClear Water Bay Kowloon Hong Kong China

In this paper, a pseudopotential-based multiplerelaxation-time lattice Boltzmann model is proposed for multicomponent/multiphase flow systems. Unlike previous models in the literature, the present model not only enables the study of multicomponent flows with different molecular weights, different viscosities and different Schmidt numbers, but also ensures that the distribution function of each component evolves on the same square lattice without invoking ad- ditional interpolations. Furthermore, the Chapman-Enskog analysis shows that the present model results in the correct hydrodynamic equations, and satisfies the indifferentiability principle. The numerical validation exercises further demonstrate that the favorable performance of the present model.

关键词： Lattice Boltzman method Multicomponent flows Multiphase flow Chapman-Enskog analysis

Interface reactions between TiAl alloys and diacetatozirconic acid-yttria molds differentiated by ammonium metatungstate addition

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Rare Metals 2023年第1期42卷 296-301页

作者： Yong-Shuang Cui De-Bo Liu Li-hua chai Zi-Yong Chen College of Materials Science and Engineering Beijing University of TechnologyBeijing100124China Beijing Institute of Astronautical Systems Engineering Beijing100076China

Two types of diacetatozirconic acid-yttria molds which were labeled as ZYW mold(diacetatozirconic acidyttria mold with traces of ammoium metatungstate in the slurry) and ZY mold(diacetatozirconic acid-yttria mold without ammonium metatungstate) were prepared by traditional investment *** ZYW and ZY molds were sintered in a carbon-reducing atmosphere and in air,respectively,at 1550℃ for 4 *** between Ti-47Al-2Cr-2Nb(at%) alloys and the molds at 1650℃ for 30 min were *** microstructures of the metalmold interfaces and the presence of inclusions and oxygen contamination in the TiAl bulk alloy were analyzed,and the influences of ammonium metatungstate were *** results indicate that WO_(3)releases O into the TiAl melt,introducing tungsten metal into the alloy *** TiAl alloy ingots cast in the ZY molds had the fewest inclusions and the lowest oxygen contamination.

关键词： TiAl-based alloys Diacetatozirconic acidyttria molds Ammonium metatungstate Interactions

Lattice Boltzmann Method for Simulating the Temperature Jump and Velocity Slip in Microchannels

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Communications in Computational Physics 2007年第6期2卷 1125-1138页

作者： Lin Zheng Bao-Chang Shi Zhen-hua chai Department of Mathematics Huazhong University of Science and TechnologyWuhan 430074China State Key Laboratory of Coal Combustion Huazhong University of Science and TechnologyWuhan 430074China.

The velocity slip and temperature jump in micro-Couette flow are investigated with the lattice Boltzmann method(LBM).A new slip boundary condition with the non-equilibrium extrapolation scheme is used in a thermal lattice Boltzmann model(TLBM)where double distribution functions are used to simulate the velocity and the temperature fields in order to capture the velocity slip and the temperature jump of the wall *** simulated velocity and temperature profiles are in good agreement with the analytic results,which shows the suitability of the present model and the new boundary treatment for describing thermal microflows with viscous heat dissipation.

关键词： Lattice Boltzmann velocity slip temperature jump.

Simulation research on a minimum root-mean-square error rotation-fitting algorithm for gravity matching navigation

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Science China Earth Sciences 2012年第1期55卷 90-97页

作者： WANG HuBiao WANG Yong FANG Jian chai hua ZHENG Hui Institute of Geodesy and Geophysics Chinese Academy of SciencesWuhan 430077China Graduate University of the Chinese Academy of Sciences Beijing 100049China

Gravity/inertial combination navigation is a leading issue in realizing passive navigation onboard a submarine. A new rotation-fitting gravity matching algorithm, based on the Terrain Contour Matching (TERCOM) algorithm, is proposed in this paper. The algorithm is based on the principle of least mean-square-error criterion, and searches for a certain matched trajectory that runs parallel to a trace indicated by an inertial navigation system on a gravity base map. A rotation is then made clockwise or counterclockwise through a certain angle around the matched trajectory to look for an optimal matched trajectory within a certain angle span range, and through weighted fitting with another eight suboptimal matched trajectories, the endpoint of the fitted trajectory is considered the optimal matched position. In analysis of the algorithm reliability and matching error, the results from simulation indicate that the optimal position can be obtained effectively in real time, and the positioning accuracy improves by 35% and up to 1.05 nautical miles using the proposed algorithm compared with using the widely employed TERCOM and SITAN methods. Current gravity-aided navigation can benefit from implementation of this new algorithm in terms of better reliability and positioning accuracy.

关键词： Terrain Contour Matching algorithm minimum root-mean-square error rotation of coordinates weighted fit gravityaided navigation

A lattice Boltzmann–cellular automaton study on dendrite growth with melt convection in solidification of ternary alloys

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Chinese Physics B 2018年第8期27卷 582-592页

作者： Dong-Ke Sun Zhen-hua chai Qian Li Guang Lin School of Mechanical Engineering Southeast UniversityNanjing 211189China Open Project of State Key Laboratory of Advanced Special Steel Shanghai UniversityShanghai 2E0444China School of Mathematics and Statistics Huazhong University of Science and TechnologyWuhan 431）074China School of Materials Science and Engineering ＆ Materials Genome Institute Shanghai Uniwrsity Shanglmi 200444China Department of Mathematics School of Mechanical EngineeringPurdue UniversityVCesl LafityetteIV 47907USA

A lattice Boltzmann （LB）-cellular automaton （CA） model is employed to study the dendrite growth of A1-4.0 wt%Cu- 1.0 wt%Mg alloy. The effects of melt convection, solute diffusion, interface curvature, and preferred growth orientation are incorporated into the coupled model by coupling the LB-CA model and the CALPHAD-based phase equilibrium solver, PanEngine. The dendrite growth with single and multiple initial seeds was numerically studied under the conditions of pure diffusion and melt convection. Effects of initial seed number and melt convection strength were characterized by new- defined solidification and concentration entropies, The numerical result shows that the growth behavior of dendJ-ites, the final microstructure, and the micro-segregation are significantly influenced by melt convection during solidification of the ternary alloys. The proposed solidification and concentration entropies are useful characteristics bridging the solidification behavior and the microstructure evolution of alloys.

关键词： lattice Boltzmann dendritic growth numerical simulation melt convection

Deployment dynamics and control of spinning space web 36

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Deployment dynamics and control of spinning space web

Cole-Hopf Transformation Based Lattice Boltzmann Model for One-dimensional Burgers' Equation

第36届中国控制会议

作者： Liu Haitao Song Xumin Lin Qi chai hua The Department of Space Command The Academy of Equipment

ISBN: (纸本)9781538629185

Space web is lightweight membrane or cable net deployable in space. Deployment and stabilization of large space web by spin have gained interest because the rotational inertia forces are in the plane of rotation and the spin rate that determines the magnitude of the web tension can be chosen to meet the mission requirements. Nevertheless, during the development process, without control or inappropriate control may cause the severe wave of the web, even the dangerous situation such as reverse winding. Therefore, it is necessary to establish an accurate model and design a feasible control strategy. In this study, a simplified analytical model of the spinning web for the first step is established by using Lagrange equation, and the model validity is verified. Several control laws for the spinning web are tested, and an optimal control law is chosen in the view of deployment effect and energy consumption.

关键词： spinning space web deployment dynamics and control MK control law

来源： cnki会议评论

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Communications in Theoretical Physics 2018年第3期69卷 329-335页

作者： Xiao-Tong Qi Bao-Chang Shi Zhen-hua chai School of Mathematics and Statistics Huazhong University of Science and TechnologyWuhan 430074China Hubei Key Laboratory of Engineering Modeling and Scientific Computing Huazhong University of Science and TechnologyWuhan 430074China

In this paper,we present a Cole-Hopf transformation based lattice Boltzmann(LB)model for solving one-dimensional Burgers'equation,and compared to available LB models,the effect of nonlinear convection term can be *** Chapman-Enskog analysis,it can be found that the converted diffusion equation based on the Cole-Hopf transformation can be recovered correctly from present LB *** numerical tests are also performed to validate the present LB model,and the numerical results show that,similar to previous LB models,the present model also has a second-order convergence rate in space,but it is more accurate than the previous ones.

关键词： Burgers'equation Cole-Hopf transformation lattice Boltzmann model

Vertical Distribution of Soil Carbon, Nitrogen, and Phosphorus in Typical Chinese Terrestrial Ecosystems

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Chinese Geographical Science 2015年第5期25卷 549-560页

作者： chai hua YU Guirui HE Nianpeng WEN Ding LI Jie FANG Jiangping Key Laboratory of Ecosystem Network Observation and Modeling Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Agriculture and Animal Husbandry College of Tibet University

Characterization of the vertical distribution of soil organic carbon(C), nitrogen(N), and phosphorus(P) may improve our ability to accurately estimate soil C, N, and P storage. Based on a database of 21 354 records in 74 long-term monitoring plots from 2004 to 2013 in the Chinese Ecosystem Research Network(CERN), we built fitting functions to quantify the vertical distribution of soil C, N, and P(up to 100 cm depth) in the typical Chinese terrestrial ecosystems. The decrease of soil C, N, and P content with depth can be well fitted with various mathematical functions. The fitting functions differed greatly between artificial(agriculture) and natural(desert, forest, and grassland) ecosystems, and also differed with respect to soil C, N, and P content. In both the artificial and natural ecosystems, the best fitting functions were exponential functions for C, quadratic functions for N, and quadratic functions for P. Furthermore, the stoichiometric ratios of soil C, N, and P were ranked in descending order: grassland > forest > agriculture > desert, and were also associated with climate. This study is the first to build the fitting functions for the profile distribution of soil C, N, and P in China at a national scale. Our findings provide a scientific basis to accurately assess the storage of C, N, and P in soils at a large scale, especially for the integrative analysis of historical data.

关键词： soil profile storage stoichiometry vertical distribution China