亚临界CO2在缩放喷管中降压膨胀的数值模拟

忽略两相间的滑移速度,采用Fluent中的混合模型对亚临界CO2过冷液体进入缩放喷管降压膨胀产生气泡的两相流动过程进行了二维数值模拟.其中,气液两相间单位体积内的质量传递率采用空化模型理论进行计算.计算工况如下:喷管液体CO2进口压力为61MPa,温度为29315K,喷管出口为两相状态.计算结果显示,CO2工质流经喉部时,压力急剧降低,相间的质量传递率达到最大值,CO2工质发生相变;工质进入扩散段后,随着压力降低,气体份额不断增大,喷管出口压力为165MPa时,气体体积份额约为093.数值模拟值与实验值对比结果为,计算压力与实测压力值最大误差不超过101%,计算温度与实测温度值最大误差不超过19%.数值模拟揭示了亚临界CO2在喷管中的气液两相膨胀过程.     

出口锯齿修形对轴对称喷管RCS的影响研究

为了研究出口边缘锯齿修形对轴对称喷管边缘绕射场和腔体内部散射场的影响,以轴对称喷管为基准模型,对其出口边缘进行8种不同齿角的锯齿修形,齿数均为12,采用迭代物理光学法和等效边缘电磁流法研究分析了基准喷管模型和8种出口锯齿修形喷管模型的边缘绕射场和腔体散射场的电磁散射特性。结果表明：对出口边缘进行锯齿修形可有效降低喷管全局探测角范围的绕射场RCS,且修齿齿角越小,效果越明显;但出口边缘锯齿修形对降低喷管腔体散射场RCS无明显作用。     

出口锯齿修形对轴对称喷管雷达散射截面的影响研究

为了研究出口边缘锯齿修形对轴对称喷管边缘绕射场和腔体内部散射场的影响,以轴对称喷管为基准模型,对其出口边缘进行8种不同齿角的锯齿修形,齿数均为12,采用迭代物理光学法和等效边缘电磁流法研究分析了基准喷管模型和8种出口锯齿修形喷管模型的边缘绕射场和腔体散射场的电磁散射特性。结果表明:对出口边缘进行锯齿修形可有效降低喷管全局探测角范围的绕射场雷达散射截面(RCS),且修齿齿角越小,效果越明显;但出口边缘锯齿修形对降低喷管腔体散射场RCS无明显作用。     

试油测试作业中天然气放喷管线求产极限探讨

目前试油测试作业过程中,天然气放喷测试管线的尺寸没有统一的标准,不同尺寸和长度天然气放喷管线的求产极限不明确。为确定天然气放喷管线的合理求产极限,在考虑天然气放喷出口呈现的不同流动状态基础上,建立更为合理的天然气放喷管线水力计算方程,求取不同流量大小天然气在不同尺寸和长度放喷管线流动过程中的沿程压力损耗值和局部压力损耗值等参数,进而得到放喷管线起点压力;并与测试分离器最高许可工作压力进行比较,从而确定出不同长度和尺寸天然气放喷管线条件下分离器的最大可测试产量。在此基础上对放喷管线的强度进行校核计算,判断放喷管线的安全状态。现场应用表明,采用推荐方法计算放喷管线起点压力和现场作业实际结果非常稳合,最大误差小于5%,说明在考虑放喷出口流动状态下的放喷管线起点压力计算方法较可靠,可为现场放喷测试管线尺寸选择和最大求产极限提供具体的指导标准。     

氧枪喷头内部流场的仿真研究

利用流体分析软件CFD对氧枪喷头内部流动状况进行了模拟计算,对喷头结构变化对喷头内部流场分布的影响和喷管内的壅塞现象进行了研究分析,为设计氧枪喷头和操作、使用氧枪提供参考依据。研究结果表明:喷管收缩段、扩张段、出口直径尺寸确定时,改变入口直径仅对收缩段内流场有影响,而对喉口和扩张段内流场无显著影响;喉口部位达到超音速时,仅增加入口滞止温度则出口质量流量减小,此时,发生热壅塞现象;若增加入口滞止压力则出口质量流量增大,因此工业生产中应适当提高入口滞止压力,来避免壅塞现象的发生。     

跨音速变质量槽式喷管的设计研究

喷管是风洞实现高速均匀稳定气流的核心部件,变质量喷管可通过扩散段管壁的缝隙流出部分气流来实现在不同背压下得到不同的出口马赫数.基于空气动力学原理,采用三维N-S方程以及可实现k-ε湍流模型,对喷管内流场进行了数值模拟.结果表明:收缩段型线、扩散段长度及壁缝尺寸对喷管流场特性具有重要影响,合理的型线和几何尺寸可使喷管出口具有宽阔的马赫数范围、且流场均匀稳定.     

送粉气流对冷喷涂流场及粒子速度影响的数值模拟

通过建立二维数值模型,利用计算流体力学软件进行数值模拟,研究了送粉气流压力和温度对冷喷涂过程中流场及粒子速度的影响.结果表明:喷涂中不可忽略送粉气流对流场及粒子速度的影响;为将粉末注入喷管,送粉气流的出口压力不能小于出口处的主气流压力,但增大送粉气流压力会使得进入喷管渐缩段的送粉冷气体流量增大,从而排挤高温主气流,同时也降低喷管气体流动的滞止焓,导致喷管喉部声速减小,不利于粒子加速;增加主气流温度对粒子加速效果不明显,而增加送粉气流温度可有效提高粒子撞击基板的速度,进而提高粉末粒子的沉积效率.     

喷口修形对二元喷管红外特征影响的数值研究

为降低排气系统的红外特征,以轴对称喷管为基准,设计了一种出口宽高比为4∶1的二元喷管;并对二元喷管出口型面进行不同尾缘修形。在商业软件中计算了二元喷管的温度场、速度场、压力场和组分浓度场的分布,采用自主开发的红外软件NUAA-IRSE,用反向蒙特卡罗法计算各喷管的红外辐射特征;并与基准轴对称喷管的计算结果进行对比。计算结果表明:二元喷管及对其尾缘修形后,遮挡了部分排气系统内部的高温部件,强化了尾喷流的掺混,在大部分探测方向上抑制了排气系统的红外特征;在喷管推力系数下降小于2%前提下,尾喷流红外最大降低36%,高温壁面红外最大降低28%。     

电弧风洞半椭圆喷管流场测试分析

在电弧风洞试验中,半椭圆喷管试验技术为平板模型提供了较宽的试验流场,可以有效提高电弧加热器的能量利用率,应用于热结构考核试验。以总温、皮托压力、模型表面热流、表面压力、红外热图温度、背温等多参数测试结合数值模拟的方法分析了流场均匀性及参数分布,试验区总温、皮托压力测试表明,波动小于3%的宽度均匀区可达喷管出口长边的75%以上。     

喷管入口气温影响下的射流流场及声场特性

为了研究亚声速喷管入口气温对射流流场及声场的影响,建立了亚声速喷管计算模型,在与实验及模拟数据对比验证的基础上,分别计算了不同喷管入口气温作用下的喷管外流场和远场噪声,探究了喷管入口气温改变时喷管出口射流速度沿轴向及径向的分布规律以及喷管出口轴线上射流温度的变化特性,同时也分析了喷管入口气温对射流流场发展和远场噪声的影响。研究结果表明:射流温度增加会较为显著地缩短势流核心区域长度,势流核心区域宽度会有少许降低;射流轴线上的静温和总温在喷管后一定距离存在一个温度上升过程,各工况静温最高处比总温最高处有延后,且射流温度越高,温度开始上升位置越接近喷管出口;温度的升高对不同频率噪声影响有很大差别,降低工质入口温度有利于降噪。该研究内容为进一步探究射流噪声形成机制打下基础,同时也可为喷流噪声的控制提供新的思路。     

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.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

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.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

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.     

海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

《Chinese Science Bulletin》SUBJECT INDEX TO VOLUME 59(2014)

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Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to