封闭管道内瓦斯爆炸传播过程中障碍物形状影响效果研究

为研究封闭管道内不同形状障碍物对瓦斯爆炸的影响,运用数值模拟软件Fluent,对比分析不同形状障碍物影响下火焰传播速度、最大超压以及爆炸流场结构的变化;运用中尺度激波管道和激光纹影系统,研究封闭管道内无障碍物和矩形障碍物存在时,冲击波和火焰传播,最大超压和火焰传播速度变化情况,对数值模拟结果进行补充。研究发现,封闭管道内最大超压随传播距离的增加而增大,火焰经历“加速-减速”过程。障碍物对火焰的加速作用主要存在于障碍物附近,火焰经历“加速-减速-再加速-再减速”过程。火焰越过障碍物前受流动压缩影响产生加速,在障碍物上方受剪切层影响,火焰下侧产生湍流扰动,加速传播;火焰越过障碍物后,与障碍物下游涡旋相互作用,形成湍流火焰,加速向下游传播。薄板障碍物对火焰传播速度和最大超压的提升效果最大,其次为长方形,三角形和圆形障碍物。在障碍物附近和其下游,最大超压相较于无障碍物情况下有明显提升。     

单缝流体推力矢量喷管的气动特性

流体矢量喷管重量轻,便于维修,应用前景可观。但二次流的存在造成了流场振荡,因此研究矢量喷管的流动特性具有重要的理论和工程意义。运用数值模拟方法,通过在二元收扩(2DCD)喷管的扩张段引入二次流,研究激波控制的流体推力矢量喷管的气动特性。利用分离涡模拟(DES)湍流模型进行矢量喷管非定常流场的数值计算,先后得到了流场的流线、涡量系数、密度梯度和熵的分布。结果表明:随着流动的发展,激波不断发生振荡,上、下壁面唇口处生成的涡沿着剪切层外侧不断向下游脱落;尾流内上剪切层的摆动角度和熵增皆大于下剪切层。     

预混火焰面附近的湍流特性测量

为考察预混火焰面附近的湍流特性,以及湍流与化学反应相互作用的机理,采用激光多普勒技术(laser Doppler anemometry,LDA)对本生火焰和V型火焰的流场进行了诊断。分别通过固体粉末和雾化硅油液滴进行无条件和条件示踪,研究了全场及反应物来流的流动特性。无条件示踪的测量结果表明,火焰区的流场存在湍流度迅速增大然后衰减的现象,而速度的测值呈现双峰分布。条件示踪测量结果表明,在火焰区内反应物来流的流动特性并没有发生明显的改变。在剪切流场中,火焰面的脉动和皱褶不显著影响上游反应物的流动特性。     

预混火焰面附近的湍流特性测量

为考察预混火焰面附近的湍流特性,以及湍流与化学反应相互作用的机理,采用激光多普勒技术(laser Doppleranem ometry,LDA)对本生火焰和V型火焰的流场进行了诊断。分别通过固体粉末和雾化硅油液滴进行无条件和条件示踪,研究了全场及反应物来流的流动特性。无条件示踪的测量结果表明,火焰区的流场存在湍流度迅速增大然后衰减的现象,而速度的测值呈现双峰分布。条件示踪测量结果表明,在火焰区内反应物来流的流动特性并没有发生明显的改变。在剪切流场中,火焰面的脉动和皱褶不显著影响上游反应物的流动特性。     

不同入射激波条件下激波与湍流边界层干扰的实验研究

本文在Ma=3.4超声速低噪声风洞中开展了不同入射激波条件下激波与来流壁面湍流边界层干扰的相关实验研究,得到了不同入射激波条件下的精细流场结构、壁面压力、壁面温度分布以及他们之间的相互关系.利用基于纳米示踪的平面激光散射技术(NPLS)在单位雷诺数6.30×10~6m~(-1)条件下获得了激波与湍流边界层干扰典型流场精细的瞬态流动结构图像,并对瞬态流动图像进行统计分析,得到的诱导激波振荡位置满足正态分布.同时利用大气数据系统得到了不同入射激波条件下干扰区的壁面压力分布,以及不同入射激波强度下分离区流动结构与壁面压力变化的关系.利用温敏漆(TSP)技术,得到不同入射激波条件下干扰区模型壁面温度分布,分析了激波与湍流边界层干扰过程中出现G?rtler涡引起的条带结构与入射激波强度的关系.     

导流块深度对圆弧形凹面腔内激波聚焦过程的影响

为研究导流块深度对圆弧形凹面腔内径向入射激波聚焦过程的影响,对马赫数为1.4的径向入射激波在导流块深度分别为0、5、10、15、17.5、20、25 mm的凹面腔内反射聚焦过程进行了实验研究。用高速CCD拍摄了圆弧形凹面腔中气流流场纹影照片,并用动态压力传感器测量了聚焦过程中流场的压力变化,对径向入射激波在凹面腔内的反射聚焦过程进行了描述。通过对比不同导流块深度下激波反射聚焦过程,发现随着导流块深度的增加,凹面腔出口宽度减少,气流的排出受到限制,导致凹面腔内部的湍流度增强,由于受到湍流的较强影响,内部激波结构减弱,从而对于激波聚焦产生高温高压区产生影响,不利于激波触发爆震。     

马赫数及间距对串列双圆柱超声速绕流的影响

为揭示不同条件下超声速圆柱绕流流动机理，该文对等直径串列双圆柱超声速绕流进行了数值研究。该文基于有限体积法和欧拉方程，结合5阶高精度加权本质无振荡格式，对不同马赫数及不同圆柱间距对流场的影响规律进行了数值研究，获得了超声速串列双圆柱绕流流场稳定后的流场特性和升力、阻力系数变化规律。结果表明，计算域内的复杂波系主要由弓形激波、反射激波以及弱激波组成；马赫数的增加会使激波结构被拉伸，改变弓形激波在壁面发生的反射类型，并造成计算域出口壅塞进而影响升力、阻力系数的稳定；圆柱间距的增加使得圆柱后方速度剪切层发生摆动，并造成不同间距条件下升力、阻力系数间的差异。     

超燃冲压发动机凹腔内补氧的强化点火试验

在超燃冲压发动机扩张型燃烧室中,对凹腔内局部补氧的点火强化方法进行了试验研究。采用高速摄影手段研究了不同的补氧方式对凹腔内火焰分布特征和燃烧强度的影响,并针对并联双凹腔燃烧室构型,研究了在单侧凹腔补氧条件下向异侧凹腔的火焰传播过程。试验结果表明,采用凹腔内补氧的方式能调节凹腔内的燃料浓度分布、改善凹腔内的燃烧过程,控制燃烧放热强度;稳态燃烧情况下,观察到凹腔驻留火焰的两种存在特征,分别表现为:由回流区热量反馈机制作用下的凹腔局部驻留火焰和燃烧室全局压力反馈影响下的凹腔剪切层火焰。只有在单侧凹腔燃烧建立了全局压力反馈的条件下才能实现凹腔火焰的异侧传播。      

超音速风洞扩压器激波串现象的数值模拟

超音速扩压器性能研究具有非常重要的工程实际应用价值。该文为加深对超音速风洞扩压器内流场结构的理解,采用Fluent软件对“收缩段等直段扩张段”型扩压器流场进行了数值计算,较好模拟了扩压器中由激波/边界层干扰诱导的复杂流场的流场特性,再现了流场中的“激波串”和“伪激波”现象,与文献结果吻合较好。并以比较精细的二维网格计算结果对激波串的形成机理和典型流动结构进行了分析,同时应用于实际工程,对某超音速风洞扩压器不同二喉道长度状态下的扩压效率进行了比较。     

H-S管对超声速欠膨胀自由射流的激励

将激励装置Hartmann-Sprenger(H-S)管集成到传统物超声速射流装置中,来激励射流剪切层中的大尺度结构,并利用纹影成像对其进行实验研究.通过对瞬态纹影图和时均纹影图的分析表明有激励射流可以有效增大射流的扩散宽度,并且在2.2kHz以上激励频率的情况下均有明显的激励效果,扩散宽度相对于无激励情况,增大了近70%.     

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.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

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.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

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