半浮区热毛细对流的不稳定性与转捩

近二十年来,微重力流体开展了半浮区液桥热毛细对流的不稳定性与转捩的研究．文中给出了热毛细振荡对流发生的临界参数,分析了液桥几何位形（尺度比,体积比）、物理参数及传热参数对临界Ｍａｘａｎｇｏｎｉ的影响．报导了有关的地面模拟实验,微重力实验以及本问题的线性稳定性分析、能量分析和数值模拟结果,并介绍了定常轴对称热毛细对流通过非定常振荡热毛细对流到湍流的转捩过程和三种热毛细振荡对流的产生机理．     

半浮区热毛细对流的不稳定性与转捩

近二十年来,微重力流体开展了半浮区液桥热毛细对流的不稳定性与转捩的研究．文中给出了热毛细振荡对流发生的临界参数,分析了液桥几何位形（尺度比,体积比）、物理参数及传热参数对临界Ｍａｘａｎｇｏｎｉ的影响．报导了有关的地面模拟实验,微重力实验以及本问题的线性稳定性分析、能量分析和数值模拟结果,并介绍了定常轴对称热毛细对流通过非定常振荡热毛细对流到湍流的转捩过程和三种热毛细振荡对流的产生机理．      

Determination of cavitation noise limiting value

ＤＥＴＥＲＭＩＮＡＴＩＯＮＯＦＣＡＶＩＴＡＴＩＯＮＮＯＩＳＥＬＩＭＩＴＩＮＧＶＡＬＵＥＨｕａｎｇＪｉｎｇ－ｃｈｕａｎ（黄景泉）（ＮｏｒｔｈｗｅｓｔｅｒｎＰｏｌｙｔｅｃｈｎｉｃａｌＵｎｉｒｅｒｓｉｔｙ,Ｘｉａｎ）（ＲｅｃｅｉｖｅｄＮｏｖ．１６．１９９２...     

A comparison of four recent numerical schemes giving high resolution of shock wave and concentrated vortex

ＡＣＯＭＰＡＲＩＳＯＮＯＦＦＯＵＲＲＥＣＥＮＴＮＵＭＥＲＩＣＡＬＳＣＨＥＭＥＳＧＩＶｉＮＧＨＩＧＨＲＥＳＯＬＵＴＩＯＮＯＦＳＨＯＣＫＷＡＶＥＡＮＤＣＯＮＣＥＮＴＲＡＴＥＤＶＯＲＴＥＸＨｕａｎｇＤｕｎ（黄敦）（Ｄｅｐａｒｔ．ｏｆＭａｔｈ．ＰｅｋｉｎｇＵ...     

一种全耦合多相流分析的并行计算方法1)

研究了孔隙介质中热、水和汽流全耦合分析的并行计算方法.模型中采用了考虑毛细压力关系的修正有效应力概念,并考虑了相变和潜热传递.基本变量为位移、毛细压力、汽压和温度.并行程序是在国家高性能计算中心(北京)的曙光1000A上借助PVM(Parallel Virtual Machine)软件系统实现的,考题显示出较高的并行加速比和效率.     

2MeV有箔注入器的束流调试

为２０ＭｅＶ ＬＩＡ建造的２ＭｅＶ注入器的束流技术指标经过一年多实验调试已达到能量２ＭｅＶ、束流３ｋＡ、亮度大于或等于１０＾８Ａ／（ｍ．ｒａｄ）＾２。建立了二维数字模型，对注入器的电子发射和束流传输过程进行了模拟，用模拟结果指导实验调试，并同实验结果进行对照，重点分析了有箔情况下自有的聚焦作用。     

Tabor数、粘着数与微尺度粘着弹性接触理论

微电子机械系统（ＭＥＭＳ）等领域的飞速发展,促使我们迈进了一个表面效应在许多现象 中占主导地位的研究领域．本文重点介绍在ＭＥＭＳ中经常遇到的微尺度粘着弹性接触的相关理论． 通过对两个无量纲数——Ｔａｂｏｒ数μ（以及其相应形式）和粘着数θ的分析,以及考虑它们对于粘 着力的影响,指出了粘着弹性接触理论中所隐含的尺度效应,随着特征尺度的减小,粘着弹性接触中 的表面效应愈加明显．     

SPECTRAL METHOD IN TIME FOR KdV EQUATIONS

ＳＰＥＣＴＲＡＬＭＥＴＨＯＤＩＮＴＩＭＥＦＯＲＫｄＶＥＱＵＡＴＩＯＮＳＳＰＥＣＴＲＡＬＭＥＴＨＯＤＩＮＴＩＭＥＦＯＲＫｄＶＥＱＵＡＴＩＯＮＳ￥ＷｕＳｈｅｎｇｃｈａｎｇ（吴声昌）；ＬｉｕＸｉａｏｑｉｎｇ（刘小清）（ＲｅｃｅｉｖｅｄＦｅｂ．２２，１９９５...     

MULTIPLICITY RESULTS FOR A FOURTH-ORDER BOUNDARY VALUE PROBLEM

ＭＵＬＴＩＰＬＩＣＩＴＹＲＥＳＵＬＴＳＦＯＲＡＦＯＵＲＴＨ－ＯＲＤＥＲＢＯＵＮＤＡＲＹＶＡＬＵＦ．ＰＲＯＢＬＥＭＭａＲｕｙｕｎ（马如云）ＭａＱｉｎｓｈｅｎｇ（马勤生）（ＲｅｃｅｉｖｃｄＯｃｔ．５，１９９４．ＣｏｍｍｕｎｉｃａｌｅｄｂｙＬｉｎＺｏｎｇｃ...     

SMA短纤维增强复合材料在热载下的相交特性

在形状记忆合金（ＳＭＡ）复合材料研究中,相变特性的研究是一个主要的工作．基于Ｅｓｈｅｌｂｙ的等效夹杂模型和Ｍｏｒｉ和Ｔａｎａｋａ的场平均法,考虑到ＳＭＡ材料的强物理非线性,发展了增量型的等效夹杂模型（ＩｎｃｒｅｍｅｎｔａｌＥｑｕｉｖａｌｅｎｔＩｎｃｌｕｓｉｏｎＭｏｄｅｌ）．考虑在某一温度循环条件下讨论形状记忆合金短纤维增强的铝基复合材料在热载下的相变行为．特别研究了ＳＭＡ短纤维复合材料在变温过程中纤维几何尺寸、体积分数等参数对ＳＭＡ复合材料的相变行为和ＳＭＡ内残余应力等的影响．这些工作对于指导材料设计和了解ＳＭＡ复合材料热机械特性是颇有意义的．     

AN ALGEBRAIC MULTIGRID METHOD FOR COUPLED THERMO-HYDRO-MECHANICAL PROBLEMS

ＩｎｔｒｏｄｕｃｔｉｏｎＩｎｒｅｃｅｎｔｙｅａｒｓ,ａｇｒｅａｔｄｅａｌｏｆａｔｔｅｎｔｉｏｎｈａｓｂｅｅｎｄｉｒｅｃｔｅｄｔｏｗａｒｄｓｆｕｌｌｃｏｕｐｌｅｄｔｈｅｒｍｏ＿ｈｙｄｒｏ＿ｍｅｃｈａｎｉｃａｌａｎａｌｙｓｉｓｉｎｄｅｆｏｒｍｉｎｇｐｏｒｏｕｓｍｅｄｉａｄｕｅｔｏｅｘｔｒａｃｔｉｏｎｏｆｕｎｄｅｒｇｒｏｕｎｄｆｌｕｉｄｓ(ｗａｔｅｒ,ｐｅｔｒｏｌｅｕｍ ,ｎａｔｕｒａｌｇａｓ)ｉｎｒｅｓｅｒｖｏｉｒ,ｅｎｖｉｒｏｎｍｅｎｔａｎｄｃｏｎｓｔｒｕｃｔｉｏｎｅｎｇｉｎｅｅｒｉｎｇ (Ｌｅｗｉｓａｎ…     

Numerical simulation of coupled heat and mass transfer in wood dried at high temperature

The mutual effect between heat and mass transfer is investigated for wood dried at high temperature. A numerical model of coupled heat and mass transfer under the effect of the pressure gradient is presented. Based on the macroscopic viewpoint of continuum mechanics, the mathematical model with three independent variables (temperature, moisture content and gas pressure) is constructed. Mass transfer in the pores involves a diffusional flow driven by the gradient of moisture content, convectional flow of gaseous mixture governed by the gradient of gas pressure, the Soret effect and phase change of water. Energy gain or loss due to phase change of water is taken as the heat source. Numerical methods, the finite element method and the finite difference method are used to discretize the spatial and time dimension, respectively. A direct iteration method to solve the nonlinear problem without direct evaluation of the tangential matrix is introduced. The local convergence condition based on the contraction–mapping principle is discussed. The mathematical model is applied to a 3-D wood board dried at high temperature with the Neumann boundary conditions for both temperature and moisture content, and the Dirichlet boundary conditions for gas pressure.     

Numerical study of condensing a small concentration of vapour inside a vertical tube

The purpose of this study is to analyse the combined heat and mass transfer of liquid film condensation from a small steam–air mixtures flowing downward along a vertical tube. Both liquid and gas stream are approached by two coupled laminar boundary layer. An implicit finite difference method is employed to solve the coupled governing equations for liquid film and gas flow together with the interfacial matching conditions. The effects of a wide range of changes of three independent variables (inlet pressure, inlet Reynolds number and wall temperature) on the concentration at exit tube, local Nusselt and Sherwood numbers, film thickness, accumulated condensate rate and temperature are carefully examined. The numerical results indicate that in the case of condensing a small concentration of vapours from a mixture, the resistance to heat and mass transfer by non-condensable gas becomes very intense. The comparisons of average Nusselt number and local condensate heat transfer coefficient with the literature results are in good agreement.     

Melting heat transfer in steady laminar flow over a moving surface

The steady laminar boundary layer flow and heat transfer from a warm, laminar liquid flow to a melting surface moving parallel to a constant free stream is studied in this paper. The continuity, momentum and energy equations, which are coupled nonlinear partial differential equations are reduced to a set of two nonlinear ordinary differential equations, before being solved numerically using the Runge–Kutta–Fehlberg method. Results for the skin friction coefficient, local Nusselt number, velocity profiles as well as temperature profiles are presented for different values of the governing parameters. Effects of the melting parameter, moving parameter and Prandtl number on the flow and heat transfer characteristics are thoroughly examined. It is found that the problem admits dual solutions.     

Large eddy simulation of natural convection along a vertical isothermal surface

Large eddy simulations of natural convection along a vertical isothermal surface have been carried out using a parallel CFD code SMAFS (Smoke Movement And Flame Spread) developed by the first author to study the dynamics of the natural convection flow and the associated convective heat transfer, with sub-grid scale turbulence modeled using the Smagorinsky model. In the computation, the filtered governing equations are discretized using finite volume method, with the variables at the cell faces in the finite volume discrete equations approximated by a second order bounded QUICK scheme and the diffusion term computed based on central difference scheme. The computation was time marched explicitly, with momentum equations solved based on a second order fractional-step Adams–Bashford scheme and enthalpy computed using a second order Runge–Kutta scheme. The Poisson equation for pressure from the continuity equation was solved using a multi-grid solver. The results including the temperature and velocity profiles of the boundary layer and the local heat transfer rate are analyzed. Comparison is made with experimental data and good agreement is found.     

Theoretical and Numerical Investigation of Gas Lubrication Processes on the Basis of Aerodynamic Equations

The dimensionless parameters of the complete system of Navier-Stokes equations of a compressible gas are estimated with reference to a typical gas bearing. It is found that the three-dimensional compressible boundary layer equations should be used as the determining equations for describing gas lubrication processes. After introducing certain assumptions with respect to the dimensionless parameters in the determining equations, an equation for the pressure, the generalized Reynolds equation, is obtained.Use of the spectral method of analysis makes it possible to transform the generalized Reynolds equation into a system of ordinary differential equations. An analytic solution of the entire boundary value problem is obtained for a journal bearing with fairly small eccentricity. By comparing the numerical results obtained using both the solution of the generalized Reynolds equation and the traditional theory it is possible to estimate the effect of the inertia forces, dissipation processes, and heat transfer.     

带源参数的二维热传导反问题的无网格方法

利用无网格有限点法求解带源参数的二维热传导反问题，推导了相应的离散方程. 与 其它基于网格的方法相比，有限点法采用移动最小二乘法构造形函数，只需要节点信息，不 需要划分网格，用配点法离散控制方程，可以直接施加边界条件，不需要在区域内部求积分. 用有限点法求解二维热传导反问题具有数值实现简单、计算量小、可以任意布置节点等优点. 最后通过算例验证了该方法的有效性.     

The fundamental equations in finite element method of coupled thermo-elastic plane problem

The fundamental equations in finite element method for unsteady temperature field elastic plane problem are derived on the bases of variational principle of coupled thermoelastic problems. In these derivations, elastic plane is divided into three nodes triangular elements, and time interval is divided into linear time elements, in which all the variables, including displacements and temperatures at various nodal points, are varied linearly with time. Two coupled sets of linear algebraic equations of all the unknown displacements and temperatures at every nodal point in every instant (i.e. the terminal values of time elements) are obtained. They are the fundamental equations of the said problem.The total energy in elastic body not only contains the potential energy and heat energy but also contains the kinetic energy, if the rate of change of temperature field with respect to the time in thermoelastic problem is large enough. And the change of displacement is included in the equations of heat conduction. For this reason the variational principle of coupled thermoelastic problems is employed. [1] In this paper, expressions of this principle for plane problems are given. The discretization is carried on then, and Hamilton's action and the potential action of heat flow of elements are derived. Finally they are assembled, so as to get the polar value of the action. And thus the groups of linear algebraic equations in matrix form are obtained.