绕翼型低雷诺数流动的数值仿真

层流转捩到湍流及翼型表面分离泡的产生是绕翼型低雷诺数流动的重要特征,对流场产生很大影响。针对这一流动现象,选取E387翼型为研究对象,采用求解雷诺平均N-S方程的有限体积法,结合当前应用较广泛的Spalart-Allmaras,SST k-ω,Realizable k-ε三种湍流模型,对雷诺数为300000时翼型绕流流场进行了数值模拟,并将结果与Selig等人的风洞实验数据进行对比,评估三种湍流模型对绕翼型低雷诺数流动的模拟能力。基于对翼型阻力计算不准原因的分析,提出了一种基于Michel转捩判据的数值模拟方法,分别从分离泡的模拟、壁面摩阻分布、翼型阻力系数等方面与实验数据进行对比,结果表明该方法可以较好的模拟低雷诺翼型绕流流场。     

基于RNG k-ε湍流模型钝体绕流的数值模拟

采用RNG k-ε湍流模型对钝体绕流流场进行了数值模拟．计算采用非交错网格的有限体积法求解二维不可压N-S方程．计算结果表明，RNG k-ε湍流模型可以成功地模拟绕钝体的不稳定、非定常和剧烈分离流动。     

醇烃聚结分离数值模拟中湍流模型的选择

针对目前醇烃分离的聚结板在数值模拟时湍流模型难以选择的问题,通过实验和数值模拟结合的方法,将聚结板流道上部沉积的油相厚度作为分析指标,对Standard k-ω、SST k-ω、Standard k-ε、Realizable k-ε、Realizable k-ε及RNG k-ε6种常用的湍流模型的模拟结果对比,发现Standard k-ω模型与实验值之间的相对误差最小,优于文献中常用的k-ε模型。     

采用不同湍流模型对半封闭狭缝湍流冲击射流的数值模拟

针对海洋石油工程中废弃平台切割技术的需要,采用充分发展的入口条件结合标准壁面函数,将标准k-ε模型、RNG k-ε模型、Realizable k-ε模型和雷诺应力模型应用于半封闭狭缝湍流冲击射流的数值模拟,采用减小网格尺寸和提高差分格式精度等措施来减小数值伪扩散对冲击射流流动的影响.结果表明:雷诺应力模型和Realizable k-ε湍流模型在湍流冲击射流的数值模拟中具有一定的优越性,Realizable k-ε模型的计算量较小;减小网格尺寸并不能降低数值黏性对计算结果的影响;提高差分格式的精度可以在一定程度上降低数值黏性对计算结果的影响,MUSCL格式并没有显著提高计算结果的精度.     

考虑当地流动特征的Zwart-Gerbera-Belamri空化模型改进及应用

为减小Zwart-Gerbera-Belamri空化模型中经验参数取值对数值模拟结果的影响,基于当地流动特征修正了Zwart-Gerbera-Belamri空化模型.联立Realizable k-ε湍流模型,分别采用修正前后的Zwart-Gerbera-Belamri空化模型对二维NACA0009 MOD水翼空化流场进行了数值模拟,空化数范围为0.75~0.90.并采用修正前后的Zwart-Gerbera-Belamri空化模型对二维Clark-Y水翼的初生空化、片状空化、云空化进行非定常数值模拟,空化数范围为3.00~0.55.将数值模拟结果与已有实验结果进行对比,结果表明:引入当地流动特征可以有效减小Zwart-Gerbera-Belamri空化模型中的气泡半径及气核体积分数的取值对数值模拟结果的影响,且修正后的空化模型能够捕捉不同空化数下绕Clark-Y翼型的时均升阻力系数的变化趋势.      

湍流模型在NexGen燃烧器出口流场模拟中的应用

Nex Gen燃烧器是美国联邦航空管理局(federal aviation administration,FAA)指定用于开展防火试验的燃烧器。采用商用Ansys Fluent软件对NexGen燃烧器进行三维定常数值模拟,研究其出口流场,为防火试验试验方案的设计提供参考和指导。首先,分别利用冷态流场和燃烧反应的实验数据验证计算模型的有效性;其次,由于燃烧问题和NexGen燃烧器结构的复杂性,为寻求一种能够捕捉其流场变化特性的湍流模型,研究不同湍流模型对出口流场的影响。分别选用Standard k-ε模型、RNG k-ε模型和Realizable k-ε模型进行数值模拟。结果表明,采用不同湍流模型时,计算得到的速度场和温度场不同;而Realizable k-ε模型计算得到的燃烧器出口下游101.6 mm处校准面上的温度分布、七点平均温度和平均热流密度与实验值吻合较好,因此更适用于防火试验的模拟研究。     

不同湍流模型在列车外流场计算中的比较

通过对简化缩比的列车模型在无侧偏角工况下分别进行模型风洞试验和数值模拟,评估了5种常用湍流模型在列车外流场模拟中的计算精度.数值模拟与风洞试验结果的分析对比表明:Realizable(可实现)k-ε在阻力的计算上精度最高,误差最小为2.5%;SST(剪切应力输运)k-w在升力的计算上更为精确,误差最小为0.5%.Standard(标准)k-w和SST k-w对准二维分离的捕捉与油流显示试验最接近,Realizable k-ε则对三维分离位置的预测更准确.     

弹丸湍流流场数值计算研究

该文对弹丸粘性绕流流进行了数值模拟研究。 数值模拟的出发方程为雷诺平均的Navier-Stokes方程,湍流模型采用了高雷诺数k-ε两方程模型,应用二阶的TVD格式,给出了SOC形弹丸的流场波系结构和湍流粘性系数的分布规律。结果表明,该数值计算方法可以取得高精度清晰度的流场结构。     

不同湍流模型比较模拟撞击流

构造了计算撞击流流场分布的数值简化模型,并用有限容积法对间距为H的两个对置平板喷嘴间的湍流作用区域进行数值模拟研究．数值模拟采用了三种湍流模型：标准的k-ε模型、RNG k-ε模型（renormalization group k-ε model）以及雷诺应力模型．数值模拟数据的有效性通过将模拟结果与由对环境温度下两对置喷嘴之间的撞击流试验的结果比较得到证实．通过与实验数据的比较发现,由于考虑了平均流动中的旋转及旋流流动情况,RNG k-ε模型在撞击流区域获得的结果要好于用标准k-ε模型和雷诺应力模型获得的结果．     

基于不同湍流模型的离心泵叶轮内部流场分析

基于计算流体力学数值模拟技术,对一个低比转速离心泵叶轮内部流场流动情况进行分析研究。分别采用4种湍流模型:标准k-ε模型、RNGk-ε模型、Realizable k-ε模型和雷诺应力模型(RSM)及SIMPLE算法,对不同湍流模型及不同工况下的扬程预测曲线,比较计算时间的差别,在此基础上,比较不同模型在设计工况下的流场,并与实验结果进行了对比分析。     

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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