N-S方程在非结构网格下的求解

在Ｒｏｅ的矢通量差分分裂的基础上，吸收了ＮＮＤ格式的优点，提出了一种非结构网格下求解Ｅｕｌｅｒ方程和Ｎ－Ｓ方程的高分辨率高精度迎风格式．这种格式具有捕捉强激波和滑移线的良好性能．在时间方向上采用了显式和隐式两种解法．文中还给出了自适应技术．最后，成功地完成了ＧＡＭＭ超音速前台阶绕流、二维平板无粘激波反射、三维Ｈｏｂｓｏｎ叶栅流动、ＶＫＩ叶栅流动、Ｃ３Ｘ叶栅流动的数值模拟，得到了满意的结果     

DSMC位置元方法中的表面元的程序标识及分子表面反射确定论判据

在直接模拟Ｍｏｎｔｅ－Ｃａｒｌｏ（ＤＳＭＣ）方法的位置元方法中,精确描述物面形状、准确判断分子是否与某一表面元相撞,直接关系着气动力热的计算精度,是该方法需要解决的关键问题．为解决此问题,给出了发展的ＤＳＭＣ方法在计算三维过渡领域的位置元方案的两个改进首先,编制了一个对所有外形描述均可做到标识表面元及计算表面元面积等工作的通用程序,并通过两个例子验证了该程序的快速性和有效性;其次,发展了分子表面反射确定论判据,代替了原有的几率判据,与圆球自由分子流准确解和过渡领域贴体网格ＤＳＭＣ结果进行比较,证明了上述判据的有效性．     

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

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

CCD automated polariscope system and the stress analysis methods

ＣＣＤＡＵＴＯＭＡＴＥＤＰＯＬＡＲＩＳＣＯＰＥＳＹＳＴＥＭＡＮＤＴＨＥＳＴＲＥＳＳＡＮＡＬＹＳＩＳＭＥＴＨＯＤＳＡｎＬｉ－ｑｉａｎ（安里千）（ＰｅｋｉｎｇＧｒａｄｕａｔｅＳｃｈｏｏｌ．ＣｈｉｎａＵｎｉｖｅｒｓｉｔｙｏｆＭｉｎｉｎｇ）Ｂｅｉｊｉｎｇ（Ｒ...     

Numerical studies for a model describing complexity

ＮＵＭＥＲＩＣＡＬＳＴＵＤＩＥＳＦＯＲＡＭＯＤＥＬＤＥＳＣＲＩＢＩＮＧＣＯＭＰＬＥＸＩＴＹＨｕａｎｇＸｉｎ（黄欣）ＬｉｕＺｅｎｇ－ｒｏｎｇ（刘曾荣）（Ｄｅｐｔ．ｏｆＭａｔｈ．ＳｕｚｈｏｕＵｎｉｖｅｒｓｉｔｙ,Ｓｕｚｈｏｕ,Ｊｉａｎｇｓｕ）（ＬＮＭ,Ｉ...     

THE REMAINDER－EFFECT ANALYSIS OF FINITE DIFFERENCE SCHEMES AND THE APPLICATIONS

ＴＨＥＲＥＭＡＩＮＤＥＲ－ＥＦＦＥＣＴＡＮＡＬＹＳＩＳＯＦＦＩＮＩＴＥＤＩＦＦＥＲＥＮＣＥＳＣＨＥＭＥＳＡＮＤＴＨＥＡＰＰＬＩＣＡＴＩＯＮＳＬｉｕＲｕ－ｘｕｎ（刘儒勋）ＺｈｏｕＺｈａｏ－ｈｕｉ（周朝晖）（Ｄｅｐｔ．ｏｆＭａｔｈ．Ｕｎｉｖｅｒｓｉｔｙｏ...     

PRINCIPAL AXIS INTRINSIC METHOD AND THE HIGH DIMENSIONAL TENSOR EQUATION AX－XA＝C

ＰＲＩＮＣＩＰＡＬＡＸＩＳＩＮＴＲＩＮＳＩＣＭＥＴＨＯＤＡＮＤＴＨＥＨＩＧＨＤＩＭＥＮＳＩＯＮＡＬＴＥＮＳＯＲＥＱＵＡＴＩＯＮＡＸ－ＸＡ＝ＣＬｉａｎｇＨａｏｙｕｎ（梁浩云）（ＷｕｙｉＵｎｉｖｅｒｓｉｔｙ，Ｊｉａｎｇｍｅｎ５２９０２０，Ｐ．Ｒ．Ｃｈｉｎ...     

OBLC domain decomposition for artificial compressible equation

ＯＢＬＣＤＯＭＡＩＮＤＥＣＯＭＰＯＳＩＴＩＯＮＦＯＲＡＲＴＩＦＩＣＩＡＬＣＯＭＰＲＥＳＳＩＢＬＥＥＱＵＡＴＩＯＮＬｉｎＭｉｎｇｓｅｎ（林明森）;ＨｕａｎｇＬａｎｃｈｉｅｈ（黄兰洁）（ＲｅｃｅｉｖｅｄＤｅｃ．１７,１９９４;Ｃｏｍｍｕｎｉｃａｔｅｄｂｙ...     

A screw dislocation by nonlinear continuum mechanics

ＡＳＣＲＥＷＤＩＳＬＯＣＡＴＩＯＮＢＹＮＯＮＬＩＮＥＡＲＣＯＮＴＩＮＵＵＭＭＥＣＨＡＮＩＣＳＰａｎＫｅ－ｌｉｎ（潘客麟）（ＤｅｐａｒｔｍｅｎｔｏｆＥｎｇｉｎｅｅｒｉｎｇＭｅｃｈａｎｉｅｓ．ＴｏｎｇｊｉＵｎｉｖｅｒｓｉｔｙ,Ｓｈａｎｇｈａｉ）ＣｈｅｎＺ...     

时间发展平面混合流的三维演化

采用高精度差分方法和群速度控制方法，求解三维可压缩Ｎ Ｓ方程，直接数值模拟了时间发展的平面混合流．研究了平面混合流三维拟序结构的形成及发展．给出了流动失稳后涡的卷起，相邻两涡的对并，激波的形成及发展．指出，涡对并所诱导产生的激波对三维拟序结构的形成及发展过程是重要的．     

Computation of head–disk interface gap micro flowfields using DSMC and continuum–atomistic hybrid methods

This paper discusses computational modeling of micro flow in the head–disk interface (HDI) gap using the direct simulation Monte Carlo (DSMC) method. Modeling considerations are discussed in detail both for a stand‐alone DSMC computation and for the case of a hybrid continuum–atomistic simulation that couples the Navier–Stokes (NS) equation to a DSMC solver. The impact of the number of particles and number of cells on the accuracy of a DSMC simulation of the HDI gap is investigated both for two‐ and three‐dimensional configurations. An appropriate implicit boundary treatment method for modeling inflow and outflow boundaries is used in this work for a three‐dimensional DSMC micro flow simulation. As the flow outside the slider is in the continuum regime, a hybrid continuum–atomistic method based on the Schwarz alternating method is used to couple the DSMC model in the slider bearing region to the flow outside the slider modeled by NS equation. Schwarz coupling is done in two dimensions by taking overlap regions along two directions and the Chapman–Enskog distribution is employed for imposing the boundary condition from the continuum region to the DSMC region. Converged hybrid flow solutions are obtained in about five iterations and the hybrid DSMC–NS solutions show good agreement with the exact solutions in the entire domain considered. An investigation on the impact of the size of the overlap region on the convergence behavior of the Schwarz method indicates that the hybrid coupling by the Schwarz method is weakly dependent on the size of the overlap region. However, the use of a finite overlap region will facilitate the exchange of boundary conditions as the hybrid solution has been found to diverge in the absence of an overlap region for coupling the two models. Copyright © 2009 John Wiley & Sons, Ltd.     

开式空腔流动的蒙特卡罗直接模拟

蒙特卡罗直接模拟(Direct Simulation Monte-Carlo)方法是一种基于分子动力论的随机性数值模拟方法，它在各类稀薄气体流动模拟中得到了广泛应用。本文首先讨论了DSMC方法的基本原理，引用文献结果论述了DSMC方法与Boltzmann方程的内在一致性，采用DSMC方法从分子运动论层次对过渡区开式空腔流动进行精细模拟，再现空腔内旋涡的形成及发展过程，了解复杂流场的流场特性。模拟和分析了空腔的形状(展弦比)、壁温以及Knudsen数(稀薄性)等因素对空腔内流动和旋涡结构的影响。研究表明，空腔的展弦比、壁面温度以及流动Knudsen数等因素对空腔内旋涡的大小、形状、位置、个数都有极大的影响，应用DSMC方法可以真实再现稀薄条件下的开式空腔流动。     

高速流场气动光学RANS/DSMC混合数值模拟算法研究

提出了适用于高速流场气动光学数值模拟的RANS/DSMC混合算法.通过RANS对全局时均流场进行数值模拟,再对其中局部流场的脉动量采用DSMC进行数值模拟,以Maxwellian速度分布实现RANS宏观量信息向DSMC微观量信息的传递.采用超声速环境下尖劈模型对该混合算法进行校验,对比试验结果论证了算法的正确性.在计算...     

DSMC／EPSM混合算法研究

将EPSM算法与DSMC方法结合，构造了可模拟含近连续流区及过渡流区的DSMC/EPSM混合算法。运用混合算法模拟了马赫数等于5时超音速竖板绕流及马赫数等于4时超音速平板绕流，并将结果与DSMC算法的结果进行比较，证明了DSMC／EPSM混合算法的有效性，同时将EPSM算法与DSMC算法的效率进行了比较。     

基于Boltzmann模型方程的气体运动论统一算法研究

模型方程出发,研究确立含流态控制参数可描述不同流域气体流动特征的气体分子速度分布函数方程; 研究发展气体运动论离散速度坐标法, 借助非定常时间分裂数值计算方法和NND差分格式, 结合DSMC方法关于分子运动与碰撞去耦技术, 发展直接求解速度分布函数的气体运动论耦合迭代数值格式; 研制可用于物理空间各点宏观流动取矩的离散速度数值积分方法, 由此提出一套能有效模拟稀薄流到连续流不同流域气体流动问题统一算法. 通过对不同Knudsen数下一维激波内流动、二维圆柱、三维球体绕流数值计算表明, 计算结果与有关实验数据及其它途径研究结果(如DSMC模拟值、N-S数值解)吻合较好, 证实气体运动论统一算法求解各流域气体流动问题的可行性. 尝试将统一算法进行HPF并行化程序设计, 基于对球体绕流及类``神舟'返回舱外形绕流问题进行HPF初步并行试算, 显示出统一算法具有很好的并行可扩展性, 可望建立起新型的能有效模拟各流域飞行器绕流HPF并行算法研究方向. 通过将气体运动论统一算法推广应用于微槽道流动计算研究, 已初步发展起可靠模拟二维短微槽道流动数值算法; 通过对Couette流、Poiseuille流、压力驱动的二维短槽道流数值模拟, 证实该算法对微槽道气体流动问题具有较强的模拟能力, 可望发展起基于Boltzmann模型方程能可靠模拟MEMS微流动问题气体运动论数值计算方法研究途径.      

DSMC (direct simulation Monte Carlo) analysis of microchannel flow with gas–liquid boundary

High heat capacity and constant operation temperature make a 2-phase heat remover tool promising for solving high heat dissipation problems in MEMS devices. However, microscale analysis of the flow with the conventional Navier–Stokes equation is inadequate, because the non-continuum effect is important when the characteristic dimension is comparable to the local mean free path. DSMC is a direct, particle-based numerical simulation method that uses no continuum assumption. In this paper, the gas–liquid boundary effects in microchannel flow are studied using this method. Modified DSMC code is used to simulate low-speed flow—under which viscous heating produces no significant temperature change—and MD results are incorporated into the DSMC boundary condition. Steady Couette flow simulation results show that the gas–liquid boundary affects the density distribution and the temperature dependence of the slip velocity. Unsteady simulation results show that mass transfer by diffusion is faster than momentum transfer by collision.     

稀薄气体动力学: 进展与应用

简要回顾了稀薄气体动力学的发展历程; 重点介绍了该领域最近二三十年的主要进展, 这突出表现在分子模拟方法(DSMC 方法、信息保存方法等) 的迅速发展与成功应用; 概述了航天工业、真空技术、微机电系统等尖端技术中的稀薄气流问题, 以及最近几届国际稀薄气体动力学会议的主题. 在此基础上指出了学科前沿问题, 以及几个与实际应用有关的重大问题, 如过渡流区高超声速三维非平衡流场的精细预测和实验验证、热层大气的时空演化规律与探测、以气体为介质的微机电系统设计与优化、真空环境下原子水平的材料制备工艺的定量设计.     

不同形状微管道中的气体流动

不同形状微尺度管道(圆形、六边形、半圆形、不同宽高比的矩形)中的气体流动特性是微机电系统设计最为关心的问题之一.文中利用信息保存(IP)方法和直接模拟Monte Carlo(DSMC)方法进行研究,给出两种方法的计算结果相互符合,并与其它研究者的BGK模型方程计算结果进行了比较.对于微尺度管道中关心的低Mach数流动, IP方法的统计收敛效率明显优于DSMC方法.通过拟合IP和DSMC结果,给出了圆形、六边形、半圆形、不同宽高比的矩形截面情况下无量纲质量流率与等效Knudsen数的关系.     

气体化学反应流动的DSMC／EPSM混合算法研究

发展了平衡粒子模拟方法(EPSM)，建立了与高温气体化学反应动力学理论相匹配的：EPSM耦合模型，并通过混合参数进行流区的自动识别，将：EPSM方法与蒙特卡罗直接模拟方法(OSMC)结合，构造了可模拟化学反应流动的DSMC／EPSM混合算法。应用该算法对汲及化学反应的二维高超音速竖板绕流流场进行模拟，将结果与DSMC方法的结果进行比较，验证了新算法对求解化学反应流动的可行性。将混合算法的计算效率与DSMC方法的计算效率进行比较，发现混合算法能够大大提高计算效率。     

DSMC approach to nonstationary Mach reflection of strong incoming shock waves using a smoothing technique

The direct simulation Monte Carlo (DSMC) method is applied to simulation of nonstationary Mach reflection of strong shock waves. Normally the DSMC method is very time consuming in solving unsteady flow field problems especially for high Mach numbers, because of the necessity of iterative calculations to eliminate the inherent statistical fluctuation caused by a finite sample size. A central weighted smoothing technique is introduced to process the DSMC results, so that the iteration time can be significantly reduced. In spite of some relaxations of the shock wave structure, the smoothing technique is verified to be useful to estima te the flow fields qualitatively and even quantitatively by using a relatively small sample size. The comparison between the present approach and the kineticmodel approach (Xu et al. 1991a, 1991b) on the application to unsteady rarefied flow fields was also carried out.This article was processed using Springer-Verlag T_EX Shock Waves macro package 1.0 and the AMS fonts, developed by the American Mathematical Society.