稀土金属表面的振动弛豫

用ＬＥＥＤ谱，研究了稀土金属表面的振动弛豫。结果表示出，对Ｓｃ｛０００１｝，原子层间距：ｄ１＝２．４１３±０．００１Ａ（收缩８．６％±０．００１Ａ）和ｄ２＝２．６８±０．０２Ａ（膨胀１．５％±０．０２Ａ）。对Ｇｄ｛０００１｝，原子层间距：ｄ１＝２．８０±０．０４Ａ（收缩３．１％±０．０４Ａ）和ｄ２＝２．９６±０．０３Ａ（膨胀２．４％±０．０３Ａ）。对Ｔｂ｛０００１｝，原子层间距：ｄ１＝２．７５±０．０３Ａ（收缩３．３％±０．０３Ａ），ｄ２＝２．８５±０．０１Ａ（膨胀０．１８％±０．０１Ａ）和ｄ３＝２．９８±０．０３Ａ（膨胀４．７％±０．０３Ａ）。对Ｔｂ｛１１２０｝，原子层间距：ｄ１＝１．６５±０．０２Ａ（收缩８．３％±０．０２Ａ）和ｄ２＝１．８０±０．０４Ａ（膨胀０．０６％±０．０４Ａ）     

竖直振动激励下的准二维容器中颗粒物质的对流运动

通过实验测量了准二维容器中颗粒物质对流运动的轨迹、流动区域、速率分布及周长和周期.实验结果表明:与流体的一般流动不同,准二维容器中颗粒物质的对流即使在流速不大的情况下也是非稳定流动.分析了影响对流非稳定性的因素,引入q因子,通过流量守恒定律半定量地确定了各因素对流动非稳定性的影响程度.     

振动斜板上下落液体薄膜的数值模拟

用Galerkin有限元法数值模拟了振动斜板上的下落液体薄膜流动,研究了流场中不同强迫频率和初始扰动频率的影响.结果表明由于它们之间的相互作用,流场中出现低频信号,其在流场中的非线性效应使得表面波发生合并,加速了表面波的发展.对较高的强迫频率,这种效应更明显,且可观察到孤立包的产生.     

液体对微振动的放大效应

根据表面波声光效应的原理,实验上建立了固体表面微振动的激光衍射测量系统.当激光斜入射到微振动引起的液体表面波上,观察到了清晰、反衬度非常高的衍射图样.利用MATLAB软件对拍摄的衍射图样进行扫描,得到了衍射光斑的光强分布图,并根据衍射图样宽度与表面波振幅的解析关系式,求出了液体表面波的振幅,其大小在微米量级.改变样品池中液体的深度,测得不同深度下液体表面波的振幅,给出了表面波振幅与液体深度之间的解析关系,并发现了液体对微振动的放大效应.利用液体对微振动的放大效应,求出了固体表面微振动的振幅,实现了固体表面微振动的探测.     

液体对微振动的放大效应

根据表面波声光效应的原理,实验上建立了固体表面微振动的激光衍射测量系统.当激光斜入射到微振动引起的液体表面波上,观察到了清晰、反衬度非常高的衍射图样.利用MATLAB软件对拍摄的衍射图样进行扫描,得到了衍射光斑的光强分布图,并根据衍射图样宽度与表面波振幅的解析关系式,求出了液体表面波的振幅,其大小在微米量级.改变样品池中液体的深度,测得不同深度下液体表面波的振幅,给出了表面波振幅与液体深度之间的解析关系,并发现了液体对微振动的放大效应.利用液体对微振动的放大效应,求出了固体表面微振动的振幅,实现了固体表面微振动的探测.     

表面纳米结构及其自由能对滴状冷凝传热的影响

通过抛光和氧化刻蚀方法在基体壁面形成微米和纳米尺度的微观结构,然后制备十八烷基硫醇分子自组装膜,从而得到空气中表观接触角为160°的SAM-1表面和空气中表观接触角为116°的SAM-2表面.实验研究了常压条件下两类表面的滴状冷凝传热特性.结果表明两种表面都能够有效提高冷凝传热效果.但是,具有表面纳米结构的SAM-1表面的滴状冷凝传热特性低于SAM-2表面.分析了纳米结构和液固自由能差效应对滴状冷凝传热影响的共同作用机理.     

二氧化钛薄膜表面甲醇吸附的和频振动光谱

自行搭建了用于研究表面光催化的宽带红外和频振动光谱并可以原位紫外光激发的装置. 利用自制的结构紧凑小巧的高真空样品池,可以在10 kPa氧气氛围下经原位紫外光照除掉 射频磁控溅射制备的二氧化钛薄膜表面的有机污染物. 通过在室温下改变甲醇气压和指认吸附在薄膜表面的甲醇的和频振动光谱,发现薄膜表面有两种吸附的甲醇,分子形式吸附的甲醇(CH₃OH)和解离吸附的甲醇(CH₃O). 当甲醇的覆盖度由低变高时,分子形式吸附的甲醇的CH₃的对称伸缩振动和费米共振峰红移了6～8 cm^-1. 真空下,薄膜表面的甲氧基和表面的氢原子可以重新结合并以甲醇分子的形式脱附. 研究表明二氧化钛薄膜体系存在两个平衡：气相甲醇和表面吸附的甲醇分子之间,以及表面吸附的甲醇分子和甲氧基之间.     

疏水表面振动液滴模态演化与流场结构的数值模拟

为了研究疏水表面垂直振动液滴的运动规律,本文建立了振动液滴的三维模型,考虑了振动液滴的动态接触角变化过程,通过流体体积函数和连续表面张力(volume of fluid-continue surface force,VOF-CSF)方法实现了液滴受迫振动的数值模拟,得到了液滴的四种模态(2,4,6和8)动态演化过程、内...     

几种液体金属自由表面的MHD不稳定性实验研究

介绍了在核工业西南物理研究院的液态金属实验回路(LMEL)上获得的几种可供液态偏滤器-限制器系统选用的液体自由表面的磁流体动力学(MHD)效应不稳定性的实验结果。实验发现：自由表面射流在穿越梯度横磁场时射程变短、截面变扁平,但MHD效应稳定,调节射流与磁场的夹角可以控制射流的流动特性;自由表面膜流MHD效应存在三种现象,即层流、溪状流和湍流。层流是由多束射流打到固体表面产生的(简称“射-膜流”),从MHD效应角度考虑,“射-膜流”将是四种可选液态偏滤器-限制器系统的液体自由表面形式中最佳的选择。同时,探讨了从物理的角度来理解四种自由表面形式的MHD效应的现象。     

复杂地形下带自由表面水流的分离涡模拟

将分离涡模型(DES),即一种RANS和LES的混合模型,应用于带自由表面的地表水流运动,建立一套数值仿真模型.模型基于有限体积法,水平面内采用非结构计算网格,垂向为结构化网格,对流项离散格式采用二阶TVD格式,并行基于Open MP语言库.算例表明DES模型有助于揭示复杂地形条件下带自由表面水流的大涡拟序结构.     

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分析了磁流体力学效应对液态金属自由表面射流稳定性的影响。从射流的感应电势、电流、速度等方面,解释射流在磁场中稳定的原因。数值计算结果验证了理论分析。     

液态金属自由表面膜流MHD效应的数值模拟

对液态金属自由表面膜流在强磁场下的磁流体力学效应进行了数值模拟研究,获得了液态金属自由表面的形状、截面流速分布及截面上的电动势分布,从而能对膜流的一些磁流体动力学行为作出解释。数值计算结果与理论分析和实验结果符合较好。由实验和数值模拟结果可以得出,液态金属膜流通过强磁场时,磁场会阻碍膜流的运动。     

Series solution of non-similarity natural convection boundary-layer flows over permeable vertical surface

The non-similarity solution for natural convection from a permeable isothermal vertical wall is considered. The governing boundary-layer equations for non-similarity flow and temperature fields are solved using the homotopy analysis method. The homotopy-Pade' technique is applied to accelerate the convergence of the homotopy-series solution. The influence of physical parameters on the non-similarity flows is investigated in detail. Different from the previous analytic results,the homotopy-series solutions a...     

Size-dependent surface tension of cylindrical nano-bubble in liquid Ar

In view of the continued disputes on the fundamental question whether the surface tension of vapour bubble in liquid argon increases, or decreases, or remains unchanged with the increase of curvature radius, the cylindrical vapour bubble of argon is studied by molecular dynamics simulation in this paper instead of spherical vapour bubble so as to reduce the statistical error. So far the surface tension of the cylindrical vapour bubble has not been studied by molecular dynamics simulation in the literature. Our results show that the surface tension decreases with radius increasing. By fitting Tolman equation with our data, the Tolman length δ =-0.6225 sigma is given under cut-off radius 2.5σ, where σ =0.3405 nm is the diameter of argon atom. The Tolman length of Ar being negative is affirmed and the Tolman length of Ar being approximately zero given in the literature is negated, and it is pointed that this error is attributed to the application of the inapplicable empirical equation of state and the neglect of the difference between surface of tension and equimolar surface.     

Size-dependent surface tension of a cylindrical nanobubble in liquid Ar

In view of the continued disputes on the fundamental question of whether the surface tension of a vapour bubble in liquid argon increases,or decreases,or remains unchanged with the increase of curvature radius,a cylindrical vapour bubble of argon is studied by molecular dynamics simulation in this paper instead of spherical vapour bubble so as to reduce the statistical error.So far,the surface tension of the cylindrical vapour bubble has not been studied by molecular dynamics simulation in the literature.Our results show that the surface tension decreases with radius increasing.By fitting the Tolman equation with our data,the Tolman length δ = -0.6225 sigma is given under cut-off radius 2.5σ,where σ = 0.3405 nm is the diameter of an argon atom.The Tolman length of Ar being negative is affirmed and the Tolman length of Ar being approximately zero given in the literature is negated,and it is pointed out that this error is attributed to the application of the inapplicable empirical equation of state and the neglect of the difference between surface tension and an equimolar surface.     

非均匀磁场中自由表面液态射流的MHD稳定性分析

基于在液态金属实验回路上的实验,对非均匀磁场中液态金属射流的MHD稳定性进行了研究,建立了一个描述射流性能的简化模型。由此简化模型所得的结果与从实验获得的结果相比较表明,它们相当吻合,并发现在此液态金属射流中存在一个固有稳定性区域。     

Soret效应对具有自由表面的圆柱形浅池内双组分溶液热对流影响的实验研究

为了探究Soret效应对具有自由表面的圆柱形浅液池内双组分溶液热对流过程的影响, 通过实验观察了质量分数为50%的正癸烷/正己烷混合溶液在不同深宽比的液池内流动失稳后的自由表面耗散结构及液池内的温度波动. 结果表明, 双组分溶液流动失稳的临界热毛细Reynolds数小于纯工质的值, 且其随液层深宽比的变化规律与纯工质相同. 当深宽比小于0.0848时, 流动失稳后在自由表面观察到热流体波, 监测点处温度波动主频随热毛细Reynolds数增大而增加; 当深宽比大于0.0848时, 随热毛细Reynolds数的增大, 流动失稳后自由表面依次呈现轮辐状、花苞状、分离-合并-分离交替变化的条纹状结构.     

Effect of surface tension on the mode selection of vertically excited surface waves in a circular cylindrical vessel

Singular perturbation theory of two-time-scale expansions was developed in inviscid fluids to investigate patternforming, structure of the single surface standing wave, and its evolution with time in a circular cylindrical vessel subject to a vertical oscillation. A nonlinear slowly varying complex amplitude equation, which involves a cubic nonlinear term,an external excitation and the influence of surface tension, was derived from the potential flow equation. Surface tensionwas introduced by the boundary condition of the free surface in an ideal and incompressible fluid. The results show that when forced frequency is low, the effect of surface tension on the mode selection of surface waves is not important.However, when the forced frequency is high, the surface tension cannot be neglected. This manifests that the function of surface tension is to cause the free surface to return to its equilibrium configuration. In addition, the effect of surface tension seems to make the theoretical results much closer to experimental results.