WC-CMPS法对溃坝溢流问题的数值模拟

无网格粒子法(拉格朗日法)是计算流体力学领域最新一代的计算方法,由于不需要生成网格,无网格粒子法能够模拟任意形状的界面及其变形和碎裂,尤其适用于计算如溃坝溢流及波浪破碎等具有复杂自由表面运动的流体力学问题。其中,光滑粒子流体动力学方法(SPH)和移动粒子半隐式法(MPS)是无网格计算方法的典型代表。本文采用基于MPS法的修正弱可压缩移动粒子半隐式(Weakly Compressible Corrected Moving Particle Semi-implicit Method)法构建了用于求解自由表面流问题的数值计算模型,并用于模拟干床面与湿床面上的溃坝溢流问题。计算结果与实验结果的对比分析表明,采用基于WC-CMPS无网格法建立的数值计算模型对干、湿床面上溃坝溢流的溢流形态、水柱高度以及波前速度等均给出了良好的计算结果。     

弱可压缩移动粒子半隐式方法对溃坝溢流问题的数值模拟

无网格粒子法(拉格朗日法)是计算流体力学领域最新一代的计算方法。由于不需要生成网格,无网格粒子法能够模拟任意形状的界面及其变形和碎裂,尤其适用于计算如溃坝溢流及波浪破碎等具有复杂自由表面运动的流体力学问题。其中,光滑粒子流体动力学方法(SPH)和移动粒子半隐式法(MPS)是无网格计算方法的典型代表。采用基于MPS法的修正弱可压缩移动粒子半隐式法(weakly compressible corrected moving particle semi-implicit method)构建了用于求解自由表面流问题的数值计算模型,并用于模拟干床面与湿床面上的溃坝溢流问题。计算结果与实验结果的对比分析表明,采用基于WCCMPS无网格法建立的数值计算模型对干、湿床面上溃坝溢流的溢流形态、水柱高度以及波前速度等均给出了良好的计算结果。     

水砂混相流运动的CIP-DEM耦合数值模型

为建立精确模拟水砂混合流(如:挟砂溃坝溢流)问题的数值计算方法,提出了模拟固液混相流运动的垂向二维CIPDEM法耦合数值计算模型。模型采用CIP(constrained interpolation profile scheme)法求解描述水体运动的Navier-Stokes流体运动方程,采用DEM(discrete element method)法求解描述泥沙粒子团运动的牛顿力学方程;并通过水砂间的相互作用关系将水-砂运动进行耦合。通过分别对溃坝溢流和砂体下落的单相体运动进行数值模拟并与前人的实验结果进行对比,验证了CIP法流体计算模型和DEM法砂体计算模型妥当。在此基础上,采用所建立的CIP-DEM水砂耦合数值计算模型对干床面上的挟砂溃坝溢流问题进行了数值模拟,计算得出的挟砂溃坝溢流中的水、砂运动形态和运动过程与Zhang(2009)等的实验结果吻合良好,表明提出的CIP-DEM耦合模型在对具有大自由表面变形的水砂运动问题的模拟中具有较好的适用性。     

二维溃坝的数值模拟研究

为了研究溃坝问题中流体的运动和自由液面的演变,针对简化的块状水坍塌进行了数值模拟。其中,流体控制方程通过有限体积法进行离散,方程的对流项和扩散项分别采用了一阶迎风格式和中心差分格式;对压力与速度耦合的离散方程以IDEAL算法进行求解;以流体体积分数法和PLIC方法进行自由液面捕捉和重构;对两相流问题中的表面张力通过连续表面力(CSF)模型进行转化。基于上,分别对有限空间内的二维溃坝和带障碍物溃坝问题进行了数值模拟,对不同时刻的自由液面进行了捕捉并与实验结果进行了对比,证明了所采用方法的精确性。     

孤立波在复合斜坡上浅水变形的CIP模拟

基于约束插值剖面(CIP)方法建立二维数值水槽,用更接近实际地形的复合斜坡来模拟岸坡,将波浪-岸坡-空气的相互作用问题通过多相流模型进行求解.运用双曲正切插值(THINC)法捕捉自由面,虚拟粒子法重构物体表面,对孤立波的近岸变形、破碎和水气掺混等强非线性复杂现象进行了分析.首先,对建立的数值水槽的造波性能进行了验证;然后,针对不同入射波高的孤立波在复合斜坡上的行进和演变展开了模拟,分析了孤立波在复合斜坡上的演变过程,并与相应的实验结果进行了对比,符合较好;最后,探究了复合斜坡的转折点对自由面抬升和速度场的影响.结果表明基于CIP法建立的数值模型可以很好地模拟孤立波在复合斜坡上复杂的浅水变形过程.     

曲线坐标下波浪抛物型缓坡方程及近岸流数值模型研究

建立了曲线坐标系下的波浪抛物型缓坡方程及近岸流数值模型,对不规则岸线地形下的波浪传播变形及近岸流运动进行了数值模拟研究.首先基于曲线化抛物型缓坡方程建立了正交曲线坐标系下的近岸波浪传播数值模型;然后通过正交曲线变换建立了正交曲线坐标系下的近岸流数值模型;进而基于波浪辐射应力的概念,耦合上述数值模型,对Gourlay模型实验和Hamm模型实验中不规则岸线地形条件下的波浪传播变形及近岸流运动进行了数值模拟研究,并结合实测资料对数值模拟结果进行了验证分析;最后基于上述耦合数值模型对美国San Francisco海湾的Ocean Beach海岸波浪斜向入射所产生的波浪场及波浪破碎所形成的近岸流进行了数值模拟研究.对比分析表明,本文数值结果与实验结果或其它学者所得数值结果基本一致,从而验证了本文数值模型的有效性.     

基于改进MPS方法的弹性支撑侧壁对溃坝现象的影响分析

溃坝现象广泛存在于船舶与海洋工程、港口与航道工程,水利水电工程等领域,并具有巨大的破坏性。同时,溃坝过程是一种非常复杂的流动现象,常常伴有自由液面的翻卷、破碎和飞溅现象,传统网格法在处理这些问题中往往会因为网格大变形而导致数值模拟的失败。本文采用一种经过改进的基于拉格朗日粒子的无网格方法(MPS),首先对固定侧壁的溃坝现象进行模拟,在验证该方法的有效性的基础上,探究了弹性支撑侧壁对溃坝现象中的流动形态、侧壁受力以及表面波对侧壁的砰击压力的影响规律。     

非线性波作用下非对称沙纹床面流场特性数值分析

海床上的沙纹对泥沙输运和波浪衰减有着重要的影响.通过数值波浪水槽研究了非线性波作用下非对称沙纹床面底层的流动特性.控制方程为雷诺时均方程和 k-ε紊流模型.入射波为椭圆余弦波,采用PLIC-VOF法追踪自由表面.通过数值模拟得到了不同波浪条件下的瞬时速度场和涡量场.计算结果表明:非线性波作用下,非对称沙纹床面两侧的涡动强度不相等,涡量值与波浪参数密切相关;波浪非线性增强,涡量值增大,最大涡量值对应的相位角减小;涡量值大小的变化与外流场速度变化不同步达到最大,随着Ursell数增大,涡量值在小相角下达到最大值.     

基于SWE-SPH的下游为湿河床的溃坝水流模拟

为了更好地模拟溃坝水流状态,避免有限元等网格法中的网格缠结和扭曲问题,本文将光滑粒子流体动力学法应用在浅水波方程中,建立二维溃坝水流数值模型,依次模拟瞬时全溃、非对称局部溃坝、对称溃坝3种工况下的溃坝水流流动情况,仿真模拟结果表明:该方法合理准确,揭示出了溃坝水流流动细节,且自由表面处理简单。     

阶梯溢流坝滑行水流掺气过程的大涡模拟

阶梯滑行水流具有较强的紊动特征和复杂的水—气自由面,其数值模拟研究具有较高的难度。文中采用数值模拟方法对阶梯溢流坝的溢流过程与滑行水流的掺气过程进行研究,并探讨其掺气机理。采用体积分数(VOF)多相流模型和大涡模拟(LES)方法,对坡度为2.5∶-1的阶梯溢流坝模型进行计算。结果表明,计算结果与实验结果较为吻合,数值模型可靠,且能够生动地模拟阶梯溢流过程和掺气过程。进一步分析得出结论:足够大的湍动能和涡结构发展是自由面变形继而发生自掺气的内部原因。     

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.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

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     

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

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