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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 Research Center for Fluid Dynamics, School of Science, PLA university of Science and technology, Nanjing 211101, china state key laboratory of structural analysis for industrial equipment Dalian University of Technology Dalian China Research Center for Fluid 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

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,Nanjing 211101,china 2 state key laboratory of structural analysis for industrial equipment,dalian university of technology,dalian 11602.,china 3 School of Aeronautics and Astronautics,dalian university of technology,dalian 11602.,china School of Science PLA University of Science and Technology Nanjing China state key laboratory of structural analysis for industrial equipment Dalian University of Technology Dalian China School of Aeronautics and Astronautics Dalian University of Technology Dalian 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

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 Research,Zhengzhou 450003,china 3 Research 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 China Yellow River Institute of Hydraulic Research Zhengzhou China Research Center for Fluid 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

Functions for patch test in finite element analysis of the Mindlin plate and the thin cylindrical shell

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Science china(Physics,Mechanics & Astronomy) 2009年第5期52卷 762-767页

作者： CHEN WanJi 1,2 ,wang JinZhi 1,3 &ZHAO Jie 1 1state key laboratory for structural analysis of industrial equipment,dalian university of technology,dalian 11602.,china 2Institute for structural analysis of Aerocraft,Shenyang Institute of Aeronautical Engineering,Shenyang 110136,china 3 College of Science,Institute of dalian Nationalities,dalian 11602.,china state key laboratory for structural analysis of industrial equipment Dalian University of Technology Dalian China Institute for structural analysis of Aerocraft Shenyang Institute of Aeronautical Engineering Shenyang China College of Science Institute of Dalian Nationalities Dalian China

Current patch test for Mindlin plate element only satisfies the zero shear deformation *** patch test of non-zero constant shear for Mindlin plate problem cannot be *** shell element, the patch test does not even *** on the theory of enhanced patch test proposed by Chen W J (2006),the authors proposed the enhanced patch test function for Mindlin plate and thin cylindrical shell *** enhanced patch test function can be used to assess the convergence of the Mindlin plate and cylindrical thin shell elements.

关键词： Mindlin plate thin cylindrical shell finite element enhanced patch test test function

The Micro/Nanostructure Characteristics and the Mechanical Properties of Hemifusus tuba Conch Shell

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Journal of Bionic Engineering 2010年第4期7卷 3+308-313页

作者： Yan liang~1,Jie Zhao~2,Chengwei wu~1 1.state key laboratory of structural analysis for industrial equipment,Department of Engineering Mechanics,dalian university of technology,dalian 11602.,P.R.china 2.School of Materials Science and Engineering,dalian university of technology,dalian 11602.,P.R.china state key laboratory of structural analysis for industrial equipment Department of Engineering Mechanics Dalian University of Technology Dalian P. R. China School of Materials Science and Engineering Dalian University of Technology Dalian P. R. China

The mollusk shell mobilizes calcium from environment for skeletal *** occurs through synthesizing solidsin solution in the presence of organic molecules of specific interior regions of the conch *** ultrastructure and microhardnessof the Hemifusus tuba conch shell living in the Huang/Bo sea area are investigated in the *** is shown that thecomposition and microstructure of the mollusk shell vary in different *** prodissoconch shell consists only of aragonitewith the crossed-lamellar *** the spiral shell and the body shell of the Hemifusus tuba conch shell arecomposed of one calcite layer and several aragonite *** calcite layer consists of cylindrical grains,but the aragonitelayers are crossed-lamellar ultrastructure at three size *** minimum structure size (the third-order lamella) is at about20 nm - 80 *** margin of shell aperture is only composed of calcite with cylindrical *** natural optimization of theshell microstructure is intimately due to the growth of the Organic *** different positions the microhardness of molluscshell is different due to different crystal structures and crystal *** growth process of shells allows a constantrenewal of the material,thus enabling their functional adaptation to external environments.

关键词： conch shell microstructure aragonite calcite crossed-lamellar

Thermoelastic properties of sandwich materials with pin-reinforced foam cores

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Science china(Technological Sciences) 2008年第12期51卷 2059-2074页

作者： LU TianJian1,LIU Tao2,3 & DENG ZiChen2,4 1 MOE key laboratory of Strength and Vibration,School of Aerospace,Xi’an Jiaotong university,Xi’an 710049,china 2 Department of Engineering Mechanics,Northwestern Polytechnical university,Xi’an 710072,china 3 Department of Engineering,university of Cambridge,Cambridge CB2 1PZ,UK 4 state key laboratory of structural analysis of industrial equipment,dalian university of technology,dalian 11602.,china MOE key laboratory of Strength and Vibration School of Aerospace Xi’an Jiaotong University Xi’an China Department of Engineering Mechanics Northwestern Polytechnical University Xi’an China Department of Engineering University of Cambridge Cambridge UK state key laboratory of structural analysis of industrial equipment Dalian University of Technology Dalian China

Pin-reinforced foam is a novel type of sandwich core materials formed by inserting pins(trusses) into a foam matrix to create a truss-like network reinforced foam *** loading,the pins deform predominantly by local stretching whilst the deformation of foam is governed by local *** paper presents a theoretical study on the thermoelasticity of pin-reinforced foam sandwich *** calculate the effective thermoelastic properties of pin-reinforced foam cores,the energy-based homogenization approach is employed to develop a micromechanics-based model,calibrated by the existing experimental *** is found that the stiffness of the sandwich core is mainly governed by pin reinforcements:the foam matrix contributes little to sandwich *** with traditional foam cores without pin reinforcements,the changes in inplane thermal expansion coefficients are not vigorous as a result of pin reinforcements,while the through-thickness thermal expansion coefficient changes *** is also demonstrated that it is possible to design materials with zero or negative thermal expansion coefficients under such a context.

关键词： sandwich panel pin reinforcement analytical solutions homogenization thermoelasticity thermal expansion

Extended multiscale finite element method for mechanical analysis of heterogeneous materials

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Acta Mechanica Sinica 2010年第6期26卷 899-920页

作者： Hong-wu Zhang·Jing-Kai wu·Jun L·Zhen-Dong Fu state key laboratory of structural analysis for industrial equipment, Department of Engineering Mechanics, Faculty of Vehicle Engineering and Mechanics, dalian university of technology,dalian 11602.,china state key laboratory of structural analysis for industrial equipment Department of Engineering Mechanics Faculty of Vehicle Engineering and Mechanics Dalian University of Technology Dalian China

An extended multiscale finite element method （EMsFEM） is developed for solving the mechanical problems of heterogeneous materials in *** underlying idea of the method is to construct numerically the multiscale base functions to capture the small-scale features of the coarse elements in the multiscale finite element *** the basis of our existing work for periodic truss materials, the construction methods of the base functions for continuum heterogeneous materials are systematically introduced. Numerical experiments show that the choice of boundary conditions for the construction of the base functions has a big influence on the accuracy of the multiscale solutions, thus,different kinds of boundary conditions are proposed. The efficiency and accuracy of the developed method are validated and the results with different boundary conditions are verified through extensive numerical examples with both periodic and random heterogeneous ***, a consistency test of the method is performed numerically. The results show that the EMsFEM can effectively obtain the macro response of the heterogeneous structures as well as the response in micro-scale,especially under the periodic boundary conditions.

关键词： Extended multiscale finite element method Heterogeneous material Base function Downscaling computation

Modelling of multi-bodies in close proximity under water waves——Fluid resonance in narrow gaps

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Science china(Physics,Mechanics & Astronomy) 2011年第1期54卷 16-25页

作者： LU Lin1,2,TENG Bin3,CHENG liang 4,SUN liang5 & CHEN XiaoBo6 1 Center for Deepwater Engineering,dalian university of technology,dalian 11602.,china 2 state key laboratory of structural analysis for industrial equipment,dalian university of technology,dalian 11602.,china 3 state key laboratory of Coastal and Offshore Engineering,dalian university of technology,dalian 11602.,china 4 School of Civil and Resource Engineering,The university of Western Australia,Crawly 6003,Australia 5 Centre for Offshore Research and Engineering,Department of Civil Engineering,National university of Singapore,117576,Singapore 6 Research Department,Bureau Veritas,Neuilly-Sur-Seine,92570,France Center for Deepwater Engineering Dalian University of Technology Dalian China state key laboratory of structural analysis for industrial equipment Dalian University of Technology Dalian China state key laboratory of Coastal and Offshore Engineering Dalian University of Technology Dalian China School of Civil and Resource Engineering The University of Western Australia Crawly Australia Centre for Offshore Research and Engineering Department of Civil Engineering National University of Singapore Singapore Singapore Research Department Bureau Veritas Neuilly-Sur-Seine France

Viscous fluid model and potential flow model with and without artificial damping force(f=-μV,μ the damping coefficient and V the local averaging flow velocity) are employed in this work to investigate the phenomenon of fluid resonance in narrow gaps between multi-bodies in close proximity under water *** numerical results are compared with experimental data available in the *** comparison demonstrates that both the viscous fluid model and the potential flow model are able to predict the resonant frequency reasonably *** the conventional potential flow model(without artificial damping term) significantly over-predicts the wave height in narrow gaps around the resonant *** order to calibrate the appropriate damping coefficient used for the potential model and make it work as well as the viscous fluid model in predicting the resonant wave height in narrow gaps but with little computational efforts,the dependence of damping coefficient μ on the body geometric dimensions is examined considering the parameters of gap width Bg,body draft D,body breadth ratio Br and body number n(n = 2,3),where Br = BB/BA for the case of two bodies(Body A and Body B) with different breadths of BA and BB,*** was confirmed that the damping coefficient used for the potential flow model is not sensitive to the geometric dimensions and spatial *** was found that μ∈ [0.4,0.5] may guarantee the variation of Hg/H0 with kh to be generally in good agreement with the experimental data and the results of viscous fluid model,where Hg is the excited wave height in narrow gaps under various dimensionless incident wave frequencies kh,H0 is the incident wave height,k = 2π/L is the wave number and h is the water depth.

关键词： narrow gap fluid resonance water wave viscous fluid model potential flow model finite element method boundary element method

Topology Optimization of Metamaterial Microstructures for Negative Poisson’s Ratio under Large Deformation Using a Gradient-Free Method

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Computer Modeling in Engineering & Sciences 2024年第5期139卷 2001-2026页

作者： Weida wu Yiqiang wang Zhonghao Gao Pai Liu state key laboratory of structural analysis for industrial equipment Dalian University of TechnologyDalian116024China

Negative Poisson’s ratio(NPR)metamaterials are attractive for their unique mechanical behaviors and potential applications in deformation control and energy ***,when subjected to significant stretching,NPR metamaterials designed under small strain assumption may experience a rapid degradation in NPR *** address this issue,this study aims to design metamaterials maintaining a targeted NPR under large deformation by taking advantage of the geometry nonlinearity mechanism.A representative periodic unit cell is modeled considering geometry nonlinearity,and its topology is designed using a gradient-free *** unit cell microstructural topologies are described with the material-field series-expansion(MFSE)*** MFSE method assumes spatial correlation of the material distribution,which greatly reduces the number of required design *** conveniently design metamaterials with desired NPR under large deformation,we propose a two-stage gradient-free metamaterial topology optimization method,which fully takes advantage of the dimension reduction benefits of the MFSE method and the Kriging surrogate model ***,we use homogenization to find a preliminary NPR design under a small deformation *** the second stage,we begin with this preliminary design and minimize deviations in NPR from a targeted value under large *** this strategy and solution technique,we successfully obtain a group of NPR metamaterials that can sustain different desired NPRs in the range of[−0.8,−0.1]under uniaxial stretching up to 20% ***,typical microstructure designs are fabricated and tested through *** experimental results show good consistency with our numerical results,demonstrating the effectiveness of the present gradientfree NPR metamaterial design strategy.

关键词： Topology optimization microstructural design negative Poisson’s ratio large deformation