Experimental study of thermocapillary convection on a liquid bridge consisting of fluid with low Prandtl number in a floating half-zone

A device of mercury liquid bridge of floating half-zone is designed to experimentally explore thermo-capillary convection and its instability of a low Prandtl number liquid. Noncontacted diagnostic techniques were developed to monitor surface flow and surface deformation. The surface flow and the influence of a growing surface film (or skin) on the flow were observed It is shown that the film is a key factor in changing the behavior associated with the thermocapillary convection. The experiment indicates that the critical Marangoni number should be much higher than that expected by the numerical simulation. The condition and process of surface film growth are discussed. The surface oscillation of the mercury bridge wrapped with "dirt-film" was observed, and the characteristics and the frequency associated with this oscillation are given.     

Space experimental device on Marangoni drop migrations of large Reynolds numbers

The space experimental device for testing the Marangoni drop migrations has been discussed in the present paper. The experiment is one of the spaceship projects of China, In comparison with similar devices, it has the ability of completing all the scientific experiments by both auto controlling and telescience methods. It not only can perform drop migration experiments of large Reynolds numbers but also has an equi-thick interferential system.     

Numerical investigation of thermocapillary migration of the drop for large Marangoni numbers

An axisymmetric model is adopted to simulate the problem of unsteady drop thermocapillary motion for large Marangoni numbers. Front tracking methods are used in the investigation. It is found that the non-dimensional drop migration velocity will decrease with increasing Marangoni number. This agrees well with the experimental results obtained from the 4th Shen-Zhou space ship. In the meanwhile, this is also the first time for numerical simulations to verify the experimental phenomenon under large Marangoni numbers. Recommended by Prof. WANG ZhanGuo, Member of Editorial Committee of Science in China, Series E: Technological Sciences Supported by Chinese Academy of Sciencer Innovation Program and the National Natural Science Foundation of China (Grant Nos. G10502054, G10432060)     

Characters of surface deformation and surface wave in thermal capillary convection

In the field of fluid mechanics, free surface phenomena is one of the most important physical processes. In the present research work, the surface deformation and surface wave caused by temperature difference of sidewalls in a rectangular cavity have been investigated. The horizontal cross-section of the container is 52 mm×42 mm, and there is a silicon oil layer of height 3.5 mm in the experimental cavity. Temperature differ- ence between the two side walls of the cavity is increased gradually, and the flow on the liquid layer will develop from stable convection to un-stable convection. An optical diag- nostic system consisting of a modified Michelson interferometer and image processor has been developed for study of the surface deformation and surface wave of thermal capillary convection. The Fourier transformation method is used to interferometer fringe analysis. The quantitative results of surface deformation and surface wave have been calculated from a serial of the interference fringe patterns. The characters of surface deformation and surface wave have been obtained. They are related with temperature gradient and surface tension. Surface deformation is fluctuant with time, which shows the character of surface wave. The cycle period of the wave is 4.8 s, and the amplitudes are from 0 to 0.55 μm. The phase of the wave near the cool side of the cavity is opposite and correlative to that near the hot side. The present experiment proves that the surface wave of thermal capillary convection exists on liquid free surface, and it is wrapped in surface deformation.     

存在垂直加热时的矩形池内热毛细对流的数值模拟

为了了解垂直加热对矩形浅液池内稳态热毛细对流的影响,利用有限容积法进行了二维直接数值模拟,液池左、右壁分别维持恒定温度Th和Tc,且ThTc,底部被加热,自由表面存在散热,液池宽深比为(20~30),流体为1cSt硅油。结果表明,随着底部加热热流密度的增大,矩形液池内的流动会由单胞或多胞流动转化为旋转方向相反的非对称双胞流动,流动转化过程的临界热流密度随Marangoni数和Biot数的增加而增大,随液池宽深比的增加而减小,液池内的最高温度会随Marangoni数和宽深比的增大而减小。     

一种抑制热对流不稳定方法

本研究中建立了以晶体生长系统为基础的数学物理模型,该模型为一个长高比为2∶1的方腔内的热对流,该热对流由两种驱动力引起,即浮力(由Grashof数来描述)与表面张力(由Marangoni数来描述)。大量的数值模拟显示,不同的Grashof数与Marangoni数组合产生不同的流动情况,且一个合适的表面张力能够抑制由浮力引起的热对流不稳定性。     

Growth of Czochralski silicon under magnetic field

DuringthegrowthofCZsilicon,polycrystallinesiliconrawmaterialsinquartzcruciblesbecomeheavierandheavierwiththeincreaseinthediameterofsiliconsinglecrystal.Therefore,thethermalconvectionofsiliconmeltplaysmoreandmoreimportantrolesincontrollingsiliconcrystalquality.Ingeneral,thedrivingforceofthermalconvectioncanbeexpressedbytheRayleighnumber(R)as3/,RgbTVbk=D(1)wherebisthebulkexpandingcoefficientofmelt,gthegravityaccelerator,DTtheradialtemperaturedifferenceonthefreesurfaceofmelt,bthecharacteristi…     

Cesaro-Orlicz 序列空间的对偶空间

本文主要研究了Cesaro-Orlicz序列空间的对偶空间.证明了Cesaro-Orlicz序列空间的对偶空间Cesφ实际上就是Orlicz序列空间Lφ.     

某类Orlicz序列空间的非方常数问题

在一定条件下给出了Orlicz序列空间及其对偶空间非方常数之间的关系,利用相关结果可对更广泛的空间类的非方常数进行表示,估计及高精确度的近似计算.     

Flow instability of buoyant-Marangoni convection in the LEC GaAs melt

Flow transitions and instabilities have significant effects on the quality of the crystals. The flow and heat transfer in the LEC GaAs melt are numerically studied by a time-dependent and three-dimensional turbulent flow model. The effects of the change of the buoyancy and Marangoni force on the flow state are analyzed by changing the temperature difference between the crystal and the crucible walls. The results show that the flow will transform from axisymmetric steady flow to non-axisymmetric oscillatory flow when the temperature difference exceeds the critical value, and that the mechanism of the transition is attributed to the Marangoni instability. The critical temperature differences for the flow transitions corresponding to different melt depth H are numerically predicted. Several important characteristics of the non-axisymmetric buoyant-Marangoni convection are numerically observed and compared with that of the non-axisymmetric mixed convection coupled with crystal rotation. Supported by the National Natural Science Foundation of China (Grant No. 50376078)     

空间平台在空间对抗中的应用研究

天基空间对抗武器是空间力量的重要组成部分，空间站等大型空间平台在未来空间对抗中将发挥越来越大的作用；简要分析了国外空间对抗武器的发展状况，大型空间平台在空间对抗中的优越性，介绍了国外大型空间平台的军事应用情况；提出了基于空间平台的空间对抗系统的初步方案和天基空间对抗力量的主要运用要求。     

从国际空间法看空间攻防对抗

随着现代战争对空间依赖性的增强,空间攻防对抗已受到越来越多国家的重视。为防止外层空间军事化,国际上出台了相应的空间法律、法规来约束、限制这种行为,但由于国际空间法本身存在一定缺陷以及其他国家对国际空间法持有不同态度,这种约束力表现得明显不足。通过对国际空间法的研究,指出了国际空间法存在的问题,分析了在国际空间法有限的制约范围内空间攻防对抗的发展趋势。得出:防止外空军事化和外空军备竞赛,有效地限制空间攻防对抗,完善现有国际空间法,制定顺应时代需要的空间法已是大势所趋。     

水火弯板数值模拟中的水冷换热边界条件研究

在水火弯板过程数值模拟中,对流换热边界条件尤其是水冷对流换热边界条件对数值模拟的结果影响很大,其水冷对流换热系数的求解一直是水火弯板数值模拟中的一大难题.这里采用流动沸腾换热理论对水火弯板数值模拟中的水冷对流换热边界条件进行了研究,通过求得过冷水流动泡态沸腾起始点(ONB)和过冷水流动泡态沸腾临界点(CHF)的壁面过热度,比较水火弯板过程中钢板表面各处的温度和这2个壁面温度以确定冷却水的状态,根据冷却水的状态分别求其对应的过冷水单相流动对流换热系数和过冷水流动泡态沸腾换热系数.采用沸腾曲线对流换热边界条件和流动沸腾换热边界条件的数值模拟结果进行比较,结果表明流动沸腾换热边界条件的数值模拟结果精度明显提高,具有较高的研究价值.     

多元Paley-Wiener空间的离散性

Eoff证明了单元Paley-Wiener空间Bπ,p(R)与离散的Hardy空间HP(Z),0＜p≤1是同构的,当p=1时对于多元Paley--Wiener空间,前期工作得出了类似的结果.本文作者在前期工作的基础上,证明了多元Paley-Wiener空间Bπ,p(Rn)与离散的Hardy空间HP(Zn),0＜p＜1是同构的,因而填补了我们前期工作与Eoff的结果之间的空白.     

竖直加热平板对流边界层的数值模拟

为了研究壁面温度和来流速度对边界层特性的影响,采用计算流体动力学(computational fluid dynamics,CFD)软件对空气流过竖直加热平板的对流边界层特性进行数值模拟.采用k-ε模型和SIMPLE算法分别对不同壁面温度的自然对流和不同来流速度的混合对流进行模拟计算,得到温度分布和速度分布,通过分析结果表明:高温对边界层特性的影响很小,而随着空气来流速度的增大,速度边界层和热边界层的厚度减小,最大速度增大.     

空间目标特征信息在空间作战中的作用分析

为提高对空间目标特征研究必要性的认识，对空间目标特征信息在空间作战中的作用进行了分析；在详细研究了空间目标特征的概念、分类情况以及研究现状的基础上，对空间目标特征信息在空间作战不同阶段中所发挥的信息支持作用进行了深入分析；最后，依据对空间目标特征信息在空间作战中的作用的分析，提出了对开展空间目标特征研究的建议。     

丹东城市软空间的构想

从建设地理学的角度出发,以城市软空间为突破口,对城市进行环境建设、规划设计,使自然环境与人工建筑很好地融合,并通过绿色对灰色的不断溶解,使城市能容纳更多的野生动物类群,最终使城市居民置身于良好的生态环境。     

LF拓扑空间中半开集和S—集

在格拓扑上给出了ＬＦ半开集定义的一种更为简便的等价形式，讨论了它的一些重要性质，作为其一方面的应用，与其相关的另一个重要内容ＬＦＳ－集在本文中也进行了研究，并得到了一些较好的结果。     

Hilbert空间的自反广义逆算子

本文主要借鉴Moore-Penrose广义逆,给出Hilber空间自反广义逆算子的定义,并讨论了自反广义逆算子的存在性和它的一些性质.     

关于Banach空间之原空间的存在性研究

本文考虑了共轭空间的逆问题,即求一个Banach空间的原空间。我们引进了空间集F_1与F_2,并对其性质进行了研究。在此基础上,我们证明了F_1的极小元之存在性与Banach空间之原空间的存在性等价。同时,我们还证明了F_2的极大元之存在性亦与Banach空间之原空间的存在性等价,从而将找原空间转化成找F_1之极小元或找F_2之极大元。