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Science China(Technological Sciences) 2008年第8期51卷 1073-1086页

作者： ZHOU LiXing department of engineering mechanics, Tsinghua University, Beijing 100084, China department of engineering mechanics Tsinghua University Beijing China

The derivation and closure methods of the second-order moment (SOM) combus- tion model are proposed. The application of this model to Reynolds averaged (RANS) and large-eddy simulation (LES) of turbulent swirling diffusion combustion, jet diffusion combustion, and bluff-body stabilized premixed combustion is sum- marized. It is indicated that the SOM model is much better than the eddy-beak-up (EBU) and presumed PDF models widely used in commercial software and engi- neering. The SOM modeling results are close to those obtained using the most accurate but much more complex PDF equation model. Moreover, it can save much more computation time than the PDF equation model. Finally, the SOM model is validated by the direct numerical simulation (DNS) of turbulent reacting channel flows.

关键词： turbulent combustion second-order moment model Reynolds averaged simulation large-eddy simulation

Some variational principles in electroelastic media under finite deformation

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Science China(Physics,mechanics & Astronomy) 2008年第9期51卷 1390-1402页

作者： KUANG ZhenBang department of engineering mechanics,Shanghai Jiaotong University,Shanghai 200240,China department of engineering mechanics Shanghai Jiaotong University Shanghai China

It is proposed that the universal thermodynamic energy variational principle is in-cluded in the first law of thermodynamics. Some variational principles in the elec-troelastic media under finite deformation are derived from this universal thermo-dynamic variational principle. It is suggested that in the general electroelastic analysis the environment should be considered together with the discussed elec-troelastic medium. For the variational principle of nonlinear electroelastic media the variation of the electric potential is coupled with the virtual displacement,and the variation of the initial volume should be considered. The Maxwell stress in the initial configuration is naturally derived from this variational principle and it is unique in the second order precision.

关键词： first law of thermodynamics variational principle the electroelastic media the governing equation

AN EXACT SYMPLECTIC SOLUTION FOR THE DYNAMIC ANALYSIS OF SHEAR DEFORMABLE ANTISYMMETRIC ANGLE-PLY LAMINATED PLATES

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Acta Mechanica Solida Sinica 1996年第3期9卷 263-273页

作者： Zou Guiping (department of engineering mechanics,Tongji University,Shanghai 200092) department of engineering mechanics Tongji University Shanghai 200092 China

From the mixed variational principle, by the selection of the state variables and its dual variables, the Hamiltonian canonical equation for the dynamic analysis of shear deformable antisymmetric angle-ply laminated plates is derived, leading to the mathematical frame of symplectic geometry and algorithms, and the exact solution for the arbitrary boundary conditions is also derived by the adjoint orthonormalized symplectic expansion method. Numerical results are presented with the emphasis on the effects of length/thickness ratio, arbitrary boundary conditions, degrees of anisotropy, number of layers, ply-angles and the corrected coefficients of transverse shear.

关键词： Hamilton canonical equation symplectic free vibration analysis antisymmetric angle-ply laminated plates

Application and Comparison of Two SGS Models in Large Eddy Simulation of FreeTurbulent Jet Flow

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Communications in Nonlinear Science and Numerical Simulation 1999年第1期4卷 12-19页

作者： Hong YAN and Mingde SU (department of engineering mechanics, Tsinghua University, Beijing 100084, China) department of engineering mechanics Tsinghua University Beijing 100084 China

Large eddy simulations of spatially evolved turbulent round jets were presented. The two SGS models called the standard Smagorinsky’s eddy viscosity model and the non-eddy viscosity stimulated small scale(SSS) model developed by Shah & Ferziger were applied. The Reynolds number of the flow was taken as 10000 based on the orifice diameter and the axial velocity in the orifice. The comparison between these two models showed that the standard Smagorinsky’s viscosity model with Smagorinsky’s constant of 0.1 underestimated the turbulent intensity, while the SSS model showed a better agreement with the experiment. Also the SSS model was used to investigate the development of vortex. The convective boundary condition at the outflow boundary was adopted to ensure less effect of noise on the upstream.

关键词： stimulated small scale model smagorinsky’s eddy viscosity model Round jet, Large eddy simulation

Nonlinear constitutive law for ferroelectric/ferroelastic material and its finite element realization

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Science China(Physics,mechanics & Astronomy) 2007年第1期50卷 70-86页

作者： LI YaoChen department of Aerospace engineering and Applied mechanics,Tongji University,Shanghai 200092,China department of Aerospace engineering and Applied mechanics Tongji University Shanghai China

The hysteresis phenomena of ferroelectric/ferroelastic material in polarization procedure are investigated. Some assumptions are presented based on the published experimental data. The electrical yielding criterion, mechanical yielding criterion and isotropic hardening model are established. The flow theory in incremental forms in polarization procedure is presented. The nonlinear constitutive law for electrical-mechanical coupling is proposed phenomenologically. Finally, the nonlinear constitutive law expressed in a form of matrices and vectors, which is immediately associated with finite element analysis, is formulated. In the example problem of a rectangular specimen subjected to a uniaxial electric field, the procedure from virgin state to fully polarized state is simulated. Afterward, a uniaxial compressive loading is applied to depolarizing the specimen. Results are in agreement with the experimental data.

关键词： ferroelectric/ferroelastic material constitutive law nonlinear finite element method.

Steady States of Some Models for Van derWaals Fluids

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Communications in Nonlinear Science and Numerical Simulation 1998年第3期3卷 163-167页

作者： Shaoqiang TANG(department of mechanics and engineering Science, Peking University, Beijing 100871,China) department of mechanics and engineering Science Peking University Beijing 100871 China

We study the steady states of some models for van der Waals fluid. Inparticular, for a mass viscosity model, we show that there is no "cavitation’ wave. Wealso consider the closed orbits, heterocliaic orbits, and the... 详细信息

关键词： steady state phase transition mixed-type problem

LARGE DEFLECTION THEORY OF NANOBEAMS

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Acta Mechanica Solida Sinica 2010年第5期23卷 394-399页

作者： Dujuan Zeng Quanshui Zheng 1(department of engineering mechanics,Tsinghua University,Beijing 100084,China) department of engineering mechanics Tsinghua University Beijing China

One-dimensional nanostructured materials are often used as beams in many applications such as ultrahigh-frequency resonators and ultrasensitive sensors. Compared with usual macroscopic beams, nanobeams have much higher surface/volume ratios so that their surface energies may play a significant role. Besides, they often bear large deflections due to their typically large slenderness ratios and larger elastic ranges. There is, however, lack of a theory that takes into account of both the above two features owned by nanobeams. In this paper, we present such a theory and give applied examples to show that surface energy and large deflection may individually or jointly have notable effects.

关键词： nanobeam surface energy large deflection

POLARIZED SPECKLE-PHOTOELASTICITY FOR 3-D STRESS ANALYSIS

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Acta Mechanica Sinica 1989年第1期5卷 70-76页

作者： Dai Fulong Fang Jing (department of engineering mechanics,Tsinghua University) department of engineering mechanics Tsinghua University China

Combining speckle interferometry with photoelasticity,the absolute retardation fringes in 3-D model are obtained by interference of the polarized rays reflected from the two surfaces of a sandwiched plate inside the *** method can avoid the troubles introduced by Poisson's ratio μ=0.5 and stress-optical constants ratio A/B=-2 of the photoelastic material in a stress-frozenstate,and yield the re- sults which provide necessary supplementary information for the completely-experimental solution of 3-D stress state.A comparison of experimental results with theoretical ones shoves the feasibility of the method proposed in the present paper.

关键词： speckle interferometry absolute retardation fringes in 3-D model

ARNOLDI REDUCTION ALGORITHM FOR LARGE SCALE GYROSCOPIC EIGENVALUE PROBLEM

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Acta Mechanica Solida Sinica 1996年第2期9卷 95-103页

作者： Zheng Zhaochang Ren Gexue, department of engineering mechanics, Tsinghua University, Beijing 100084 department of engineering mechanics Tsinghua University Beijing 100084

Based on Arnoldi's method, a version of generalized Arnoldi algorithm has been developed for the reduction of gyroscopic eigenvalue problems. By utilizing the skew symmetry of system matrix, a very simple recurrence scheme, named gyroscopic Arnoldi reduction algorithm has been obtained, which is even simpler than the Lanczos algorithm for symmetric eigenvalue problems. The complex number computation is completely avoided. A restart technique is used to enable the reduction algorithm to have iterative characteristics. It has been found that the restart technique is not only effective for the convergence of multiple eigenvalues but it also furnishes the reduction algorithm with a technique to check and compute missed eigenvalues. By combining it with the restart technique, the algorithm is made practical for large-scale gyroscopic eigenvalue problems. Numerical examples are given to demonstrate the effectiveness of the method proposed.

关键词： gyroscopic eigenvalue problem skew symmetry Arnoldi reduction algorithm restart technique

NUMERICAL STUDY OF TURBULENT FLOWS OVER WAVY BOUNDARIES

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Acta Mechanica Sinica 1989年第3期5卷 197-204页

作者： Zhang Zhaoshun Cheng Zhan (department of engineering mechanics,Tsinghua University) department of engineering Tsinghua University Tsinghua China

The fully developed túrbulent flows over wavy boundaries are investigated by means of the k-ε *** flow characteristics over rigid wavy walls are in good agreement with the availa- ble experimental *** drag reduction has been found in a 2-dimensional channel with periodi- cal wavy *** energy input from turbulent wind to regular waves is also studied in the paper by the same turbulence model with carefully posed boundary conditions at wind-wave *** agreement has been obtained in the prediction of the growth rates of wind waves as compared with the previous theoretical and numerical results.

关键词： turbulent flows wind wave generation drag reduction