湍流的压缩性效应及其数值模拟

综述了可压缩流体中湍流流动的研究现状,重点针对快速大变形情况下湍流的特性进行论述。讨论了可压缩湍流扰动的三种模态和能量的转换与平衡关系,对快速畸变理论和可压缩湍流的数值模拟方法作了简要介绍。     

橡皮轴对称大变形分析

本文给出了下可压缩Ｍｏｏｎｅｙ像皮材料轴对称大变形的分析步骤。提出了可以节省存储的位移和静水压力分组联立求解的方法，并给出了大变形不可压缩材料切线刚度阵是奇异的二个定理．最后给出一个例题，其结果和解析解符合的很好．     

动车组横风环境下的交会气动效应

采用三维、可压缩、非定常N-S方程的数值计算方法,对8辆编组的动车组在20 m/s横风下以250 km/h速度交会时列车表面瞬变压力和车体所受气动力及力矩进行分析,并采用间接验证方法,将风洞实验、动模型实验得到的结果分别与数值模拟结果进行对比。研究结果表明:间接验证方法下所得气动效应实验结果和数值模拟结果变化规律一致,压力幅值相对误差在5%以内;动车组横风下交会时,车体头、尾处测点压力差别较大,中部位于同侧测点压力差异较小,同一高度、不同纵向测点的压力变化波形及幅值基本一致,车体顶部测点压力始终为负;对于车体所受横向气动力及倾覆力矩,头车比中间车和尾车的大,背风车比迎风车的大;随着横风风速的增加,列车所受横向气动力及倾覆力矩峰值也迅速增加,严重威胁着动车组的安全运行。     

非均匀动压引起的瞬时局部重联

非均匀动压冲击和冲击突然停止,可能是引起等离子体边界层的局部瞬时重联的一种新机制.用二维可压缩磁流体力学数值模拟方法研究了这两个过程.根据模拟结果,提出了一种新的瞬时重联模型,称为"横向剪切流驱动重联"模型.对这种重联过程在磁层物理中可能的应用进行了讨论.     

弱可压缩SPH方法压力初始赋值方法比较

为研究不同初始流场压力赋值方法对于弱可压缩SPH方法数值结果稳定性的影响,采用静水压力赋值方法以及弱可压缩假设赋值方法,结合不同物理模型及不同数值影响因素对弱可压缩SPH方法的初始流场压力稳定性问题进行对比分析.对粒子数的比较研究表明,相同粒子数下,弱可压缩法在流场稳定速率及流场稳定性上均优于静水压力法.对人工声速的研究表明,弱可压缩法的自身稳定性及对人工声速的不敏感性显著优于静水压力法.对人工黏性的比较表明,静水压力法较弱可压缩法对人工黏性系数的敏感性较高,易受人工黏性变化而产生压力波动.弱可压缩假设赋值方法具有良好的鲁棒性,有利于提高初始流场收敛速度,提升流场数值稳定性,对于弱可压缩SPH方法流场初始赋值方法选择具有一定意义.     

自由表面流动的移动粒子半隐式模拟方法

引入可压缩因子，对移动粒子半隐式方法（MPS）进行了改进，解决了MPS方法在计算中容易出现的不稳定问题．使用改进后的方法对液柱倒塌算例进行了模拟计算，并将计算结果与实验及其他数值计算结果进行了比较．计算表明，引入可压缩因子大大提高了计算的稳定性，且方法简单易于实现，在液柱与挡板发生碰撞、流体发生大变形时依然能进行有效地模拟。     

沥青路面黏弹性泊松比近似方法的比较

为了准确应用黏弹性泊松比分析沥青路面在车轮荷载作用下的动态响应,针对3种常用的黏弹性泊松比近似方法进行了比较研究.推导了这3种黏弹性泊松比(随时间变化泊松比、不可压缩泊松比和常数泊松比)的数值关系,进而建立了一种三维沥青路面黏弹性有限元模型,比较分析了不同温度、不同加载时间下,3种黏弹性泊松比近似方法对沥青路面横向正应力响应的影响.结果表明:不可压缩泊松比始终保持为0.5,适用于高温、低频加载条件;常数泊松比始终保持为0.1,适用于低温、高频加载条件;随时间变化泊松比在0.1～0.5之间变化,应用不受温度与加载模式的限制.采用正确的黏弹性泊松比近似方法对于流动性车辙的研究有重要意义.     

粘性流体的加罚节点展开法

应用希尔伯特空间和有限元理论，把中子扩散方程的节点展开用于粘性不可压缩流体的计算，并通过人工加罚的方法，对粘性不可压缩流体的Ｎａｖｉｅｒ—Ｓｔｏｋｅｓ方程的求解提出了一类新的数值方法—加罚节点展开有限元法有从而在保证精度的基础上使计算量大为减小，论证了数值解的存在性、唯一性及收敛性，并用实例进行了验证     

平面叶栅亚音速可压缩流场计算的三种边界元法途径

研究了平面叶栅在线性化小扰动范围的亚音速可压缩位势流场的三种边界元法计算途径。其一是移用正交异性域位势问题的边界元法;其二是先把物理平面内的亚音速可压缩流场变换成计算平面内的不可压缩流场,再用边界元法进行计算;方法之三是用压缩性修正法对不可压缩流场的边界元法计算结果进行修正。算例表明了这三种处理方法各自的特点。     

带有滑动边界的可压缩磁流体方程解的局部存在性

研究了在有界区域Ω?R~3中带有滑动边界条件的可压缩磁流体方程解的局部存在性.首先构造可压缩磁流体方程组的线性化方程组,然后利用Galerkin逼近方法证明线性化可压缩磁流体方程组解的局部存在性,最后通过对线性化可压缩磁流体方程的解进行迭代,构造原方程组的逼近解序列,利用能量估计和二阶椭圆估计证明逼近解收敛,从而证明可压缩磁流体方程组解的局部存在性。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

正~~