三峡机组蜗壳内紊流的三维数值分析

报导了三峡混流式机组模型蜗壳内紊流的三维数值分析结果。文中基于Ｎ－Ｓ方程和标准的ｋ－ε紊流模型，采用贴体座标和交错网格系统，用ＳＩＭＰＬＥＣ算法对蜗壳内部的流动进行数值模拟，提出设计工况时蜗壳内部的紊流特性。数值分析结果表明：在设计工况，蜗壳内部的流动符合速度矩为常数的设计理论。文中提出的数值方法，可用于改进和优化蜗壳设计，从而提高水轮机的效率，改善水轮机的性能。     

水轮机蜗壳和固定导叶内部流动的数值模拟

为探求蜗壳内部的流动规律 ,优化蜗壳设计 ,对三峡混流式水轮机组模型蜗壳和固定导叶内部的流动进行了紊流解和 Euler解的全三维数值模拟。文中基于 Navier-Stokes方程的标准 k-ε紊流模型、Euler方程模型 ,采用贴体座标和交错网格系统 ,用 SIMPL EC算法 ,对蜗壳和固定导叶内部流动的联合计算结果进行对比分析 ,并与实验值进行了比较。还对流动的不均匀性进行分析 ,提出了改进和优化蜗壳和固定导叶设计的较为可信的解决方案     

高比转速混流式水轮机引水部件水流特性研究

对ｎｓ＝２６０ｍ·ｋＷ的混流式水轮机引水部件流场测试结果作了介绍。通过在蜗壳进口、出口、导叶出口３个断面布置五孔探针进行测量，揭示水轮机引水部件内部的流动特性。结果表明：各断面流动均具有较好的轴对称性；蜗壳进口断面基本上为轴向均匀流动；蜗壳出口断面上的环量基本上为常数；导叶出口断面的环量沿导叶高度分布不均匀，由上冠至下环逐渐增大。进行了初步分析，对改进水轮机设计提出了建议。     

蜗壳型线二维设计的理论研究及分析

介绍并补充完善了１种蜗壳型线二维逆命题设计方法，该方法能够按照蜗壳进口圆周上流动参数的不同分布形式，设计出不同的蜗壳型线．对２台性能优良的离心风机蜗壳型线进行了拟合计算，对设计中蜗壳进口流动参数理论分布形式的影响规律做了初步探讨，提出了一些新的思想和观点     

隔舌对离心泵压力脉动特性及内部流场的影响

为了明确隔舌对离心泵内部流场影响,采用滑移网格技术,对离心泵不同隔舌蜗壳情况下的外特性进行数值模拟,并结合试验分析隔舌形状对离心泵效率和扬程的影响。同时,对不同工况下单隔舌蜗壳、双隔舌蜗壳离心泵压水室各截面上压力脉动特性及其内部流场特性进行研究。研究结果表明:双隔舌蜗壳相比于单隔舌蜗壳对离心泵外特性的影响很小;单隔舌蜗壳、双隔舌蜗壳离心泵压水室各截面的压力脉动频率以叶片通过频率为主,各压力脉动幅值以近隔舌处尤为激烈;采用双隔舌蜗壳时压水室各截面压力脉动幅值明显减小,压力脉动频率多集中在中低频;在偏离设计工况下,单隔舌蜗壳离心泵的某些截面上压力脉动幅值有锐增现象,双隔舌蜗壳时其压力脉动最大降幅达45.5%;双隔舌蜗壳离心泵内部流场流动状态较好,隔舌处速度梯度变化均匀,更利于流体流动。     

小流量工况下离心风机蜗壳内部的三维流动测量分析

利用五孔探针对小流量工况下离心通风机大宽度矩形截面蜗壳内部的三维流动进行了详细的测量，给出了蜗壳螺旋通道部分的3－8个横截面内比较清晰的时均速度，静压和总压的分布图形，结果表明，在小流量工况下，蜗壳内部的二次旋涡在蜗舌处就开始形成，在一个横截面内，由开始有1个涡发展成2个，甚至3个涡，速度沿径向的分布与动量矩守恒规律经较明显的差别，特别是蜗舌附件区域的速度和压力分布与通常的分析有限大不同，蜗壳内的损失可初步归纳为4种；二次流损失，内泄漏损失，冲击损失和磨擦损失，在小流量工况下，二次流损失和内泄漏损失相对最为严重。     

叶轮时序对两级离心泵内部流动的影响研究

对离心泵而言,叶轮时序位置的改变对泵水力性能和压力脉动影响较大。本文对某两级离心泵首级和次级叶轮在七种不同时序位置下的内部流动进行了数值模拟,并对叶轮和蜗壳内部的流场和压力脉动特性进行了分析。结果表明:在设计流量下随着次级叶轮时序位置的变化,离心泵的扬程和效率分别上升了2.9%和2.4%;同时时序位置的改变影响了叶轮进口相对液流角和出口环量,改善了蜗壳隔舌处的流态,漩涡区域减小,从而降低了次级叶轮和蜗壳内部的流动损失;时序效应对次级叶轮和蜗壳压力脉动影响较大,各测点主频均无变化,但次级叶轮内测点压力脉动主频幅值降低了20.16%,蜗壳隔舌处降低了2.24%。综合比较分析不同时序位置下两级离心泵的性能,当次级叶轮旋转至首级叶轮流道中间时,离心泵的水力性能及压力脉动特性较好,研究结果可为两级离心泵设计提供参考。     

双蜗壳离心泵启动过程瞬态流动特性与隔板处压力脉动特性

为了研究双蜗壳离心泵在启动过程中蜗壳内部液体瞬态流动特性和隔板处的压力脉动特性,以一台比转速为90的双蜗壳离心泵作为研究对象,建立了一套循环管路系统,选用RNG k-ε湍流模型,应用ANSYS CFX软件对双蜗壳离心泵及循环管路系统进行了三维非定常数值计算,分析了启动过程中蜗壳内部流场演化规律和外特性变化趋势,并对隔板...     

蜗壳通道面积对离心压气机性能的影响

为了探索离心压气机蜗壳通道面积对低比速离心压气机性能及内部流动畸变的影响规律,文章建立了某离心压气机三维仿真模型,对具有5种不同通道面积蜗壳的离心压气机进行了流动仿真.结果表明,蜗壳通道面积的变化导致了压气机整体性能的改变,并影响了其内部流场畸变.压气机的近堵塞点在蜗壳通道面积较小时流场畸变增大,部分叶轮通道出现超声速...     

蜗壳进口周向非均匀流动的一种迭代计算方法

提出了通过叶轮与蜗壳 工计算来求解蜗壳内流场的方法，该方法边界条件处理简单，并能在并不增加很多计算量的基础上模拟出蜗壳进口周向流动的非均匀性，从而突破了在计算单个蜗壳时，其进口只能给均匀边界条件的局限性，通过对一蜗壳的试算结果表明，在设计工况下，蜗壳进口周向流动比较均匀，而在变工况下，特别在蜗舌附近，流动的非均匀性要强烈得多。     

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