弹丸前体喷流的气动力干扰实验研究

对一种复合增程弹的气动力干扰特性进行了实验研究,这种复合增程弹的固体火箭发动机位于弹丸肩部,通过几个均匀分布于弹体园柱部起始处的喷咀侧后向喷气产生推力,从而达到增程的目的.实验是在超声速风洞中进行的,实验Ma数为2.5,攻角α=0°～6°,喷咀倾角θ=30°,喷流压力比ε=Poj/P∞=101.222,喷流介质为冷空气.实验结果表明,喷流后弹丸阻力系数下降,升力系数上升,压心后移.并对引起气动力变化的原因做了简要分析.     

用光学纹影技术观察发动机内天然气-空气混合过程的研究

研究制作了透明的混合器模型和定容装置，使用光学纹影技术把由高速CCD照相机拍摄的纹影画像送入画像处理装置进行处理，可以定量地确定混合器内部天然气－空气的分布特性以及从喷射阀喷出的天然气喷流的形状和贯穿距离。提出了促进天然气－空气混合的途径，得出了突发天然气喷流的贯穿距离与喷射时间的平方根成正比等结论。     

跨声速旋成体弹丸气动力的数值计算

用三阶MUSCL TVD格式解三维可压缩流动N-S方程组,湍流模式为Sparlart-Allmaras模型,数值模拟了来流马赫数Ma∞=0.96、攻角α=0°和Ma∞=0.91、攻角α=2°条件下的旋成体弹丸跨声速流场,获得的弹体表面压力系数分布数值结果与实验数据吻合良好。同时还给出了流场的马赫数等值线、弹丸底部流线分布图谱,并对计算的弹底涡流结构作了扼要的分析。     

纹影技术综述

纹影技术是一种无接触式光学技术,可以将不可见的相位分布转换为清晰的可见图像。该文将简述多种纹影技术的发展历程及各类纹影技术在国内外的发展现状,然后将阐述彩色纹影技术、激光纹影技术和背景纹影技术的基本光学原理以及各类纹影法在不同领域中的研究与应用,还总结了各种纹影技术在实际操作及其实验模拟等方面的具体应用方法,展示了其在不同领域的极高的普适性,列举了目前纹影技术的一系列优点与不足之处,并指出了纹影法在实际运用中所需要注意的问题。     

通风射流纹影成像可视化实验设计

针对通风工程中气流不可视、射流理论抽象,学生无法对气流分布形成直观认识的难点,该文利用纹影成像技术构思了自由射流理论的新实验方法,并进行了实验教学设计。实验利用纹影成像技术可视化效果突出、能够进行流场尺寸量化的优点,制作了一种基于纹影成像原理的Y型光学实验系统,在通风空调实验平台基础上配合传统热敏风速元件的测量,可充分展示通风射流的湍流发展和变化规律,并获得定量特征参数。该实验利用纹影可视化手段与通风射流理论相结合,实验结果形象直观,实验过程操作性强,有助于学生充分理解通风工程中的基础射流理论知识和难点,培养学生实践和创新能力。     

平板超音速侧喷流绕流场数值模拟

该文利用显式二阶迎风ＴＶＤ格式对含侧喷流平板流场进行数值模拟。其计算结果表明二阶迎风ＴＶＤ格式较好地模拟了波系和涡系结构,为研究含侧喷流炮弹的增程机理以及参数设计提供了一定的参考价值。     

水力喷射压裂孔内压力分布研究

水力喷射压裂工艺是集水力射孔和压裂一体的新型油田增产技术.在室内实验基础上,运用流体力学计算方法,对水力喷射压裂孔道内压力场进行计算,得到了井下水力射流在地层孔道内的压力及速度分布,揭示了喷嘴空间位置、喷嘴数量、孔道形状、喷嘴压降和喷嘴直径对孔道压力的影响规律结果表明:高速射流之间具有很强的独立性,喷嘴空间位置和喷嘴数...     

基于γ-Re_θ转捩模型的垂直轴风力机气动特性研究

在两方程的剪切应力输运SST k-w全湍流模型中添加γ-Re_θ转捩模型,以某两叶片垂直轴风力机为研究对象,数值计算得到叶片表面压力的分布规律,并与文献中的实验结果进行了对比.在此基础上,分析和对比了添加转捩模型后,风轮的转矩和推力系数、叶片表面极限流线分布和叶片表面摩擦阻力系数的变化规律.结果表明:相比SST k-w全湍流模型,添加γ-Re_θ转捩模型后的四方程Transition SST转捩模型预测得到的风轮的转矩系数和推力系数的均方根分别下降了6.13%和0.55%;计算时考虑γ-Re_θ转捩模型能够预测垂直轴风力机叶片表面边界层的转捩现象和更详细地捕捉叶片表面复杂的流动特征.     

非成岩水合物单喷嘴射流破碎规律实验研究

为了提高单喷嘴射流破碎采掘水合物的效率,推进海洋非成岩水合物固态流化开采的商业化进程,基于非成岩水合物替代试样,设计非成岩天然气水合物单喷嘴射流破碎实验方案,搭建单喷嘴射流破碎实验系统,研究射流时间、射流靶距、射流压力和喷嘴水平段直径等因素对替代样射流破碎深度和破碎体积的影响.研究结果表明:在所设的实验条件下,随时间增...     

DLR-F6翼身组合体跨声速阻力计算

采用美国航空航天学会阻力测试小组提供的多块对接网格,结合Spalart-Allmaras、Wilcox’sk-ω和Menter’s k-ω SST三种湍流模型,通过求解雷诺平均Navier-Stokes方程、数值模拟DLR-F6翼身组合体的流场来研究阻力计算精度,考查网格和湍流模型对翼身组合体构型气动特性的影响.结果表明:三种湍流模型得到的机翼表面压力系数分布与实验数据吻合良好,气动力随攻角的变化趋势与实验结果一致;Spalart-Allmaras模型得到了网格收敛结果,所得阻力优于其他软件的结果;网格密度对阻力有影响,对机翼表面压力系数分布无明显影响;湍流模型对机翼表面压力系数分布的影响主要体现在激波位置上,对升力影响较小,对阻力(尤其是摩擦阻力)影响显著,对翼根处的流动分离有一定影响;在跨声速流动中,Menter’s k-ω SST模型的结果最接近实验数据.     

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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