合成射流控制下低压高负荷透平叶片边界层分离大涡模拟

为了研究合成射流对低压高负荷透平叶片边界层流动分离进行控制的效果及机理,采用大涡模拟方法对利用合成射流控制低压高负荷透平Pak-B叶栅内的非稳态流动分离特性进行了研究.在合成射流控制下的结果表明:Pak-B叶栅吸力面流动分离位置变化不大,再附位置明显提前,叶栅吸力面尾缘区域逆压梯度明显减小,总压损失系数降低,分离泡尺寸缩小;叶栅吸力面大部分剪切层黏附于壁面,也未出现大尺度二维展向涡,静压脉动特征频率向高频转移,低频脉动幅值降低,大尺度涡旋结构发生变化.通过研究还发现:在吹气过程中,边界层外部高能流体被射流卷吸进入边界层内,边界层内流体能量增大进而抑制了分离;在吸气过程中,射流孔上游区域边界层厚度减小,流速增大,从而抑制了下游流动分离.     

可压缩平板边界层的二次亚谐不稳定性

用二次稳定性理论研究可压缩平板边界层中三维扰动的产生及其非线性演化过程，揭示可压缩边界层转捩的内在机制．结果表明，可压缩边界层在较宽的波数带内存在亚谐不稳定性，其特性与不可压缩边界层相似；二次亚谐波在很宽频率和雷诺数范围内不稳定，其增长率和幅值放大因子都远大于初始波，二次亚谐共振是可压缩边界层转捩的内在机制．     

层流下不同扩张比对后向台阶流动和传热特性的影响（英文）

建立三维数值模型以研究低雷诺数范围内(50≤Re≤250)不同扩张比对后向台阶流动和传热特性的影响.在宽高比恒为16的条件下,改变扩张比分别为1.5,2.0,3.0,通过Fluent计算得到流场和温度场等.结果表明:扩张比为2.0时的数值模拟结果与先前的实验结果吻合的很好.三维后向台阶底面再附着点的分布呈抛物线状分布.当雷诺数Re=200时,随着扩张比的增大,三维后向台阶上壁面两个对称旋涡的尺寸逐渐增大,底面中心线上的Nu峰值逐渐增大,并且再附着点的位置更接近于台阶.与二维数值模拟相比,在同一扩张比下,三维后向台阶底面中心线上的Nu峰值小于二维后向台阶底面Nu的峰值.     

GCM模式中斜压波包的动力学特征

利用时间滞后相关和波包的复分解方法,分析了GCM模式资料300?hpa的经向风扰动.计算了波包的波长、波数、相速和群速等物理量,揭示了波包的基本动力学特征.斜压波包的波长为数千公里,相速为10?m/s左右.波包包络的传播速度为相速的2～3倍,下游发展仍是斜压波包的主要特征.同时,斜压波包在传播过程中显示出较好的相干性,即波包的包络能较长时间内维持其形状不变.详细分析了波包性质的季节变化和南北半球的差异,并将模式资料的结果与实测资料做了比较.     

旋转对风力涡轮叶片边界层的影响

基于经典二维叶素理论的水平轴风力涡轮设计与性能预估方法,在高风速（高能量输出）工况下得到的功率输出值通常小于实测值,即存在三维失速延迟现象。通过分析旋转对风力涡轮叶片边界层的影响,揭示产生这种失速延迟现象的物理机理。并在相同的运行条件下,比较二维工况与三维旋转工况下边界层各关键参数的差别,从而得到由于旋转的影响,边界层中气流分离点位置延迟以及动力输出增加等重要结论。     

计算旋转螺旋面三维边界层的一种积分方法

本文将计算二维层流边界层的Thwaites方法和计算二维湍流边界层的Truckenbrodt方法推广,用以求解旋转系统的“准三维”边界层方程,得到了计算旋转螺旋面上三维边界层的一种可迭代求解的积分方法.应用此方法进行了两例计算.计算结果与理论精确解或实验测量的对比表明,本文方法是有效的.     

湍流边界层Lagrangian拟序结构的辨识

用时间连续二维PIV测量充分发展湍流边界层,对测量得到的（x,y）平面速度场应用有限时间Lyapunov指数方法辨识Lagrangian拟序结构,发现湍流边界层中的典型Lagrangian拟序结构（LCS）是广义马蹄涡结构,其一端延伸至近壁流区,另一端向外层伸展,在头部具有明显的展向旋转趋势．对从FTLE场中辨识出的LCS的空间形态进行统计分析,发现LCS的倾斜角θ的概率密度分布在近壁区符合t分布,而在外层呈现为双峰分布,其概率峰分别对应马蹄涡的头部和颈部．空间相关分析表明,LCS的平均倾斜角靠沿法向先增加后减小,其数值和变动趋势与瞬时LCS倾斜角θ的均值相同．θ的最可几值在y^＋=100附近达到最大值24°,说明马蹄涡由涡颈过渡到涡头的位置最有可能出现在y^＋=100附近．最后对FTLE场进行了时间一空间相关分析,发现LCS的平均对流速度沿法向的分布在对数区与当地边界层的时均速度型基本一致,说明在湍流边界层中马蹄涡的对流决定了边界层内的流体输运特性．     

重力波波包在水平风场中非线性传播的数值模拟--Ⅰ.水平风场为均匀风场

采用全隐欧拉格式(FICE)对重力波波包在均匀风场中的三维非线性传播进行了数值模拟,给出了波包在三维空间中非线性传播的过程,分析了重力波的传播特性及风场对重力波传播的影响.计算结果表明:波振幅随高度的增加而增长,但比线性条件下的指数增长要慢;波包非线性传播的路径和能量传输速度不同于线性重力波理论给出的结果,非线性效应在顺风场中比在逆风场中更显著;风场会改变重力波传播的路径和速度.     

水力机械三维分离准则的探讨

水力机械的分离为三维流动，三维流动的侧向压力梯度产生边界层的二次流动。文中将边界层内的速度分布分为近壁粘性层和接近于主流的外层两部分，通过研究垂直于主流方向的二次流动和主流的相关性，结合三维分离线的邻近流动特性分析提出了通过主流流场参数和沿流向的二维边界层流动来判断三维流动分离的准则。在垂直于三维分离线的截面内，其流动性态和二维分离相类似。边界层的二次流动和侧向压力梯度，以及二者的相互作用是影响水力机械三维流动分离的重要因素。当主流逆压梯度的方向与二次流动的方向均在主流方向一侧时，流动的三维效应使得三维流动比二维流动不容易分离。当主流逆压梯度的方向与二次流动的方向分别在主流方向的两侧时，三维流动较易产生分离     

二维高超音速边界层扰动演化的数值研究及小激波的存在对流场结构的影响

采用三种不同的计算格式对Mach数为6, 8, 10的高超音速边界层中的二维扰动的扰动演化做了直接数值模拟. 在入口处引入不同幅值的第二模态T-S波, 研究了小激波开始生成时扰动幅值大小与Mach数的关系. 通过对扰动速度剖面与线性稳定性理论值的比较, 研究了小激波对流场结构的影响.     

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     

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