不同释放力组合下小型外挂物投放的数值模拟

将嵌套方法和结构网格相结合,提出了一种高效的时间精确数值计算方法,对不同释放力下小型外挂物的投放进行了数值模拟.该模拟在有实验验证算例的基础上进行.首先对马赫数Ma=0.95下从机翼上挂载投放弹体过程进行了分析,并将模拟结果与实验结果进行比较,二者具有很好的一致性,表明该方法的准确性和可靠性.利用上述方法对一小型弹药在不同释放力组合下的投放进行了数值模拟.结果表明,投放物和释放力的参数特性对投放后物体的运动影响较大,尤其是前端释放力的大小和作用位置对该弹药投放后的俯仰角影响显著.对同一投放物来说,释放力参数的准确程度决定着数值模拟的准确性.计算结果为气动设计及有控投放提供了依据.     

基于动态嵌套网格技术的微型共轴式双旋翼流场的数值模拟

运用动态嵌套网格技术和双时间推进算法,对微型共轴式双旋翼的非定常粘性绕流进行数值模拟和研究.针对上、下两层旋翼间距离较小和流动粘性影响较大的特点,在动态嵌套网格技术的基础上引入滑移网格技术,保证了流动信息交换的准确性.首先,模拟低雷诺数下单旋翼的流动,结果与实验数据吻合较好,验证了算法的有效性;然后,利用该方法实现对微型共轴式双旋翼流场的数值模拟.结果表明,微型共轴式双旋翼流场中,桨尖涡起主要作用,其以螺旋方式向下运动,同时与周期性运动的旋翼相互作用,使得作用在旋翼上的总体拉力呈现出周期性的变化规律.     

基于表面粗糙度修正的冷却风扇数值模拟方法研究

为了进一步提高冷却风扇多重参考坐标系(MRF)模型的数值模拟精度,结合壁面函数进行粗糙度修正,并分析MRF模型的影响因素。首先,以黏性底层中第一层网格离壁面的无因次速度u~+与距离y~+相等为依据,得到粗糙度常数、粗糙度高度与y~+之间的代数关系;根据实际壁面类型,得到修正后的y~+值与第一层网格高度,将其带入标准壁面函数进行近壁面修正。最后,以某型号冷却风扇为例,研究湍流模型、网格数量、表面粗糙度修正等因素对风扇数值模拟结果的影响。结果表明,模型可以更好地处理高应变率及流线弯曲程度较大的流动,更适合风扇的旋转流动,对风扇等旋转机械的模拟具有更高的准确性;过密的网格数量会使得计算结果出现波动;表面粗糙度修正改善了性能曲线上的一些畸点,在风扇常用工况范围内,使得试验值与仿真值的偏差由5%降低到修正后的3%以内。     

轴对称通道内超临界水对流换热数值模拟

为了研究高性能轻水堆堆芯冷却通道内超临界工质流动与换热特性,采用Fluent软件对竖直上升环形通道内超临界水与管壁间的换热过程进行数值模拟研究。通过计算结果与实验结果的对比,评估了不同网格数量、壁面第1层网格参考高度和湍流模型对数值模拟准确性的影响。对5个不同湍流模型进行对比计算。针对3种热流密度进行堆芯流动换热计算。模拟结果表明:随着网格数量的增加和壁面第1层网格参考高度的降低,预测准确度逐渐提高,但当壁面第1层网格参考高度小于0.07后,预测准确度与其无关;与其他湍流模型相比较,标准k-ω模型和剪切压力传输(SST)k-ω模型都能预测传热恶化现象,SST k-ω模型较标准k-ω模型计算结果更为准确;近壁面区域物性的剧烈变化是引起传热强化及传热恶化的主要原因。     

基于单流道和结构网格的湿式潜水泵数值模拟

采用流场模拟软件ANSYS-CFX对BQ1100-425型湿式潜水泵进行数值模拟,在完成网格无关性验证的基础上,分别研究了全流道与单流道模型,结构网格与非结构网格模型的数值模拟结果,如压力、速度等内流场和扬程、效率等外特性。结果表明:全流道数值模拟相比于单流道能更准确地反映真实流场的流动情况,但计算时间较长,计算效率低。单流道数值模拟在一定范围内能较好地反映真实流场的运行情况,且计算时间较短。结构网格与非结构网格都能准确反映实际流场的运行变化情况,但结构网格计算准确性更高,计算时间短,效率高。鉴于湿式潜水泵结构的复杂性,基于单流道结构网格的数值模拟方法能有效地模拟内流场并进行扬程、效率等性能预测。     

SPH方法在溃坝流动模拟中的应用

光滑粒子（smoothed particle hydrodynamics, SPH）方法是一种新近发展的可用于流动模拟的无网格数值方法，理论上能够适应任意变形，在模拟流体流动的剧烈变形时有显著的优势.但是流动的初始、边界条件和一些计算参数的选取都会对计算结果产生较大的影响.作者基于SPH方法的基本原理，全面考虑了各种定解条件的设置，独立发展了一套用于模拟不可压自由表面流动的SPH2D程序，并应用于溃坝流动的模拟之中.SPH模拟结果与Harlow和Welch经典的MAC（marker and cell）结果非常吻合，验证了方法的准确性，为SPH方法的进一步发展和广泛应用奠定了一定的基础.     

物性参数对封闭腔体自然对流数值模拟的影响

采用两种不同的物性参数处理方法对不同温差下的封闭方腔内自然对流进行数值计算,研究瑞利数Ra从103～106之间时,封闭方腔内空气的流动换热规律,将所得到的数值模拟结果与研究文献做了对比分析,验证了其方法的准确性,同时对比分析了利用多项式考虑气体物性参数随温度变化情况下的数值模拟结果.计算结果表明,在所计算的问题中,小温差下把热物性参数设置为常数可以一定程度上减小计算量,加快计算收敛速度,但在大温差下,物性参数设置为常数计算将造成计算结果相对误差较大.     

气体扩散CFD建模敏感性分析

 提出气体扩散计算流体力学建模敏感性分析的概念,即从众多影响模拟结果的不确定性因素中找出对建模有重要影响的方面,并监测、分析其对模拟结果的影响程度,进而选定最佳建模参数的一种不确定性分析方法。建议敏感性分析顺序应为网格依赖、边界条件、湍流模型及求解控制参数分析。重点对网格依赖和湍流模型敏感性分析的原理和方法进行了论证,并结合某高含硫集气站气体泄漏扩散建模进行了算例研究。研究结果表明,网格依赖分析可在模型预测精度和计算成本间获取平衡点;通过将各湍流模型预测结果与经验公式模型对比,可选取最适合的湍流描述方法。敏感性分析对构建合适的计算模型,提高计算精度,降低计算成本具有重要意义,是气体泄漏扩散建模中不可或缺的重要环节。     

基于正交试验方法的流动成像测井传感器优化设计

以电磁流动成像测井传感器的数值模拟为基础,在已有的正演仿真平台上,采用正交试验方法对传感器进行优化设计.根据对试验结果的统计分析和方差分析,得到传感器几何和材料参数对目标函数即全水/全油电压值变化的影响程度依次为管壁厚度>管壁介电常数>电极径向插入深度>电极张角,按优化后参数组合计算,在置信度为95%的情况下性能参数指标可达到原来的3.6301～5.8741倍.结果表明,正交试验方法可以有效地解决电磁流动成像测井传感器优化设计问题.     

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.     

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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