KTa1-xNbxO3晶体生长过程中气泡与界面的相互作用
第32卷 第11期 无 机 材 料 学 报
Vol. 32
No. 11
2017年11月
Journal of Inorganic Materials Nov., 2017
Received date: 2017-02-14; Modified date: 2017-05-15
Foundation item: National Natural Science Foundation of China (51472263, 51602330); Shanghai Sailing Program (16YF1413100) Biography: LI Shu-Hui (1992-), female, candidate of master degree. E-mail: lishuhui@https://www.360docs.net/doc/098258146.html,
Corresponding author: LIU Yan, professor. E-mail: liuyan@https://www.360docs.net/doc/098258146.html,; PAN Xiu-Hong, associate professor. E-mail: xhpan@https://www.360docs.net/doc/098258146.html,
Article ID: 1000-324X(2017)11-1223-05 DOI: 10.15541/jim20170068
Interactions Between Bubble and Interface During KTa 1-x Nb x O 3 Crystal Growth
LI Shu-Hui 1,2, PAN Xiu-Hong 1, LIU Yan 1, JIN Wei-Qing 1, ZHANG Ming-Hui 1, YU Jian-Ding 1, CHEN Kun 1, AI Fei 1
(1. Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China; 2. University of Chinese Academy of Sciences, Beijing 100039, China)
Abstract: The generation of bubbles and its interaction with the interface during melting and growth process of po-tassium tantalate niobate (KTa 1-x Nb x O 3) crystals were visualized by a high temperature in-situ observation system. It was found that bubbles are generated mainly from the solid-liquid interface during melting, rather than from the melt. Bubbles with radii smaller than 0.7r (where r is the mean radius of bubbles) arise mostly from nucleation at the interface while radii larger than 1.5r are the result of coalescence. The existence of the bubble not only lowers the growth velocity of the near interface, but also affects the structure of the crystal. The effect of a bubble on the growing interface depends on their dimension ratio together with the moving speed of the interface. There are three typical kinds (hat-, sphere- and ellipsoid-shaped) of vapor inclusion morphologies being demonstrated. The analysis of the bubble behavior can promote the understanding of the formation of inclusion defects in KTN crystal growth process.
Key words: potassium tantalate niobate; crystal growth; bubble; in situ observation; computed tomography Potassium tantalate niobate, KTa 1-x Nb x O 3(KTN), which has the largest quadratic electro-optic effect, is one of the earliest discovered materials with photorefractive characteristics [1-2]. It has attracted much attention as a promising material for electro-optical applications in the past few years [3-5]. Although the unparalleled properties of KTN single crystals have been realized for more than half century [1,6-7], application is still extremely limited because of the rigorous growth conditions [2,6]. In order to find a relatively simply way to obtain KTN crystal, re-searchers have tried several methods [8-10]. But some growth defects, such as inclusion, crack and striation, still restrict the application of the crystal [11-13]. With the purpose of obtaining KTN single crystal with high qual-ity, it is imperative to strength the study on its growth defects [12]. However, due to the difficulty for real-time observation in a high temperature environment, few studies have been focused on the generation procedure of inclusions during KTN crystal growth from the melt. In this work, we try to study the generation of bubbles with the help of a high temperature in-situ observation sys-tem [14-18]. Furthermore, combined with the morphological analysis of bubbles-induced inclusions, the influence of the existing bubble on the crystal structure was discussed in detail.
1 Experiments
KTa 1-x Nb x O 3 crystals with x = 0.78 were obtained in a melt growth apparatus, then the melting and growth process were performed and visualized in a high tem-perature in-situ observation system. The system was comprised of a heating chamber and a loop-shaped Pt wire heater as shown in Fig. 1. The Pt wire (Φ 0.2 mm) as shown in Fig. 1(a) was employed to heat and suspend the melt during the in-situ observation experiment of crystals with high melting points. The inner diameter of the loop is ~1.20 mm. Pt-10% Rh thermocouple (Φ 0.08 mm) as shown in Fig. 1(b) located in one side of the loop is used to measure the temperature with the fluctuations of less than ±2 above 1000. The power ℃℃was applied to both the electrodes of the wire as shown in Fig. 1(c) and 1(d). The video of the crystal growth process was re-corded from the microscope by a camera.
A typical experimental procedure was carried out in the following way. Before each test, the amount of the test melt was precisely controlled until a thin transmis-sive flat film of about 300 μm thickness in the center of the loop-shaped heater was obtained. Turn on the power source, record the temperature as the melting temperature
万方数据
空气泡、气泡跑得快、缓慢的气泡、打气泡、气泡比赛、上升的气泡-科技馆展品概念深化方案-上海惯量自动化
空气泡/气泡跑得快/缓慢的气泡/打气泡/气泡比赛/上升的气泡 --科技馆推荐展品设计策划概念深化方案 展示内容 展项通过气泡在三组不同的密度液体中的运动状态的不同，展示波义耳定律。展台上有3个打气筒，分别对应3个容器。科技馆展品制作生产源头工厂-上海惯量自动化有限公司提示大家容器里面分别是不同密度的液体。操作台上的打气筒，于是打气装置向容器底部打气。观众可以看到，气泡上升过程中，分别装有水、石蜡油、煤油的容器中的气泡，由于压强逐渐减小，其体积逐渐增大。 科学原理 波义耳定律是由英国化学家波义耳在1662年根据实验结果提出：在密闭容器中的定量气体，在恒温下，气体的压强和体积成反比关系。科技馆展品制作生产源头工厂-上海惯量自动化有限公司提示大家这是人类历史上第一个被发现的定律。所以气泡上升过程中，由于压强逐渐减小，其体积逐渐增大。 操作说明 1.用力压打气筒； 2.对比不同管内气泡的上升观察现象。 表现形式 机械互动 Exhibits of Science Museum： AIR BUBBL According to Boyle’s law, when the temperature is constant, the air volume of a fixed amount is reversely proportional to pressu re intensity. Production source factory of exhibits in science museu m--Shanghai GuanLiang(inertia) Automation Co., Ltd reminds everyo ne that Because high density and high viscosity of the liquid, the in termolecular acting force is very big, so the air bubble formed has an adequate volume and the resisting force when the air bubble ris
KTa1-xNbxO3晶体生长过程中气泡与界面的相互作用
第32卷 第11期 无 机 材 料 学 报 Vol. 32 No. 11 2017年11月 Journal of Inorganic Materials Nov., 2017 Received date: 2017-02-14; Modified date: 2017-05-15 Foundation item: National Natural Science Foundation of China (51472263, 51602330); Shanghai Sailing Program (16YF1413100) Biography: LI Shu-Hui (1992-), female, candidate of master degree. E-mail: lishuhui@https://www.360docs.net/doc/098258146.html, Corresponding author: LIU Yan, professor. E-mail: liuyan@https://www.360docs.net/doc/098258146.html,; PAN Xiu-Hong, associate professor. E-mail: xhpan@https://www.360docs.net/doc/098258146.html, Article ID: 1000-324X(2017)11-1223-05 DOI: 10.15541/jim20170068 Interactions Between Bubble and Interface During KTa 1-x Nb x O 3 Crystal Growth LI Shu-Hui 1,2, PAN Xiu-Hong 1, LIU Yan 1, JIN Wei-Qing 1, ZHANG Ming-Hui 1, YU Jian-Ding 1, CHEN Kun 1, AI Fei 1 (1. Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China; 2. University of Chinese Academy of Sciences, Beijing 100039, China) Abstract: The generation of bubbles and its interaction with the interface during melting and growth process of po-tassium tantalate niobate (KTa 1-x Nb x O 3) crystals were visualized by a high temperature in-situ observation system. It was found that bubbles are generated mainly from the solid-liquid interface during melting, rather than from the melt. Bubbles with radii smaller than 0.7r (where r is the mean radius of bubbles) arise mostly from nucleation at the interface while radii larger than 1.5r are the result of coalescence. The existence of the bubble not only lowers the growth velocity of the near interface, but also affects the structure of the crystal. The effect of a bubble on the growing interface depends on their dimension ratio together with the moving speed of the interface. There are three typical kinds (hat-, sphere- and ellipsoid-shaped) of vapor inclusion morphologies being demonstrated. The analysis of the bubble behavior can promote the understanding of the formation of inclusion defects in KTN crystal growth process. Key words: potassium tantalate niobate; crystal growth; bubble; in situ observation; computed tomography Potassium tantalate niobate, KTa 1-x Nb x O 3(KTN), which has the largest quadratic electro-optic effect, is one of the earliest discovered materials with photorefractive characteristics [1-2]. It has attracted much attention as a promising material for electro-optical applications in the past few years [3-5]. Although the unparalleled properties of KTN single crystals have been realized for more than half century [1,6-7], application is still extremely limited because of the rigorous growth conditions [2,6]. In order to find a relatively simply way to obtain KTN crystal, re-searchers have tried several methods [8-10]. But some growth defects, such as inclusion, crack and striation, still restrict the application of the crystal [11-13]. With the purpose of obtaining KTN single crystal with high qual-ity, it is imperative to strength the study on its growth defects [12]. However, due to the difficulty for real-time observation in a high temperature environment, few studies have been focused on the generation procedure of inclusions during KTN crystal growth from the melt. In this work, we try to study the generation of bubbles with the help of a high temperature in-situ observation sys-tem [14-18]. Furthermore, combined with the morphological analysis of bubbles-induced inclusions, the influence of the existing bubble on the crystal structure was discussed in detail. 1 Experiments KTa 1-x Nb x O 3 crystals with x = 0.78 were obtained in a melt growth apparatus, then the melting and growth process were performed and visualized in a high tem-perature in-situ observation system. The system was comprised of a heating chamber and a loop-shaped Pt wire heater as shown in Fig. 1. The Pt wire (Φ 0.2 mm) as shown in Fig. 1(a) was employed to heat and suspend the melt during the in-situ observation experiment of crystals with high melting points. The inner diameter of the loop is ~1.20 mm. Pt-10% Rh thermocouple (Φ 0.08 mm) as shown in Fig. 1(b) located in one side of the loop is used to measure the temperature with the fluctuations of less than ±2 above 1000. The power ℃℃was applied to both the electrodes of the wire as shown in Fig. 1(c) and 1(d). The video of the crystal growth process was re-corded from the microscope by a camera. A typical experimental procedure was carried out in the following way. Before each test, the amount of the test melt was precisely controlled until a thin transmis-sive flat film of about 300 μm thickness in the center of the loop-shaped heater was obtained. Turn on the power source, record the temperature as the melting temperature 万方数据
发酵过程泡沫的形成与控制
发酵过程泡沫地形成与控制 西安道尔达化工有限公司 发酵过程起泡地利弊：气体分散、增加气液接触面积，但过多地泡沫是有害地 一、泡沫形成地基本理论 泡沫地定义：一般来说：泡沫是气体在液体中地粗分散体，属于气液非均相体系 （一）泡沫形成地原因 、气液接触 因为泡沫是气体在液体中地粗分散体，产生泡沫地首要条件是气体和液体发生接触.而且只有气体与液体连续、充分地接触才会产生过量地泡沫.气液接触大致有以下两类情况： （）气体从外部进入液体，如搅拌液体时混入气体 （）气体从液体内部产生.气体从液体内部产生时，形成地泡沫一般气泡较小、较稳定. 、含助泡剂 在未加助泡剂，但并不纯净地水中产生地泡沫，其寿命在秒之内，只能瞬间存在.摇荡纯溶剂不起泡，如蒸馏水，只有摇荡某种溶液才会起泡. 在纯净地气体、纯净地液体之外，必须存在第三种物质，才能产生气泡.对纯净液体来说，这第三种物质是助泡剂.当形成气泡时，液体中出现气液界面，这些助泡剂就会形成定向吸附层.与液体亲和性弱地一端朝 着气泡内部，与液体亲和性强地一端伸向液相，这样地定向吸附层起到稳定泡沫地作用. 、起泡速度高于破泡速度 起泡地难易，取决于液体地成分及所经受地条件；破泡地难易取决于气泡和泡破灭后形成地液滴在表面自 由能上地差别；同时还取决于泡沫破裂过程进行得多快这一速度因素. 高起泡地液体，产生地泡沫不一定稳定.体系地起泡程度是起泡难易和泡沫稳定性两个因素地综合效果. 泡沫产生速度小于泡沫破灭速度，则泡沫不断减少，最终呈不起泡状态；泡沫产生速度等于泡沫破灭速度，则泡沫数量将维持在某一平衡状态；泡沫产生速度高于泡沫破灭速度，泡沫量将不断增加. 、发酵过程泡沫产生地原因 （）通气搅拌地强烈程度 通气大、搅拌强烈可使泡沫增多，因此在发酵前期由于培养基营养成分消耗少，培养基成分丰富，易起泡.应先开小通气量，再逐步加大.搅拌转速也如此.也可在基础料中加入消泡剂. （）培养基配比与原料组成 培养基营养丰富，黏度大，产生泡沫多而持久，前期难开搅拌. 例：在罐中投料，成分为淀粉水解糖、豆饼水解液、玉米浆等，搅拌，通气，泡沫生成量为培养基地倍. 如培养基适当稀一些，接种量大一些，生长速度快些，前期就容易开搅拌. （）菌种、种子质量和接种量 菌种质量好，生长速度快，可溶性氮源较快被利用，泡沫产生几率也就少.菌种生长慢地可以加大接种量（）灭菌质量 培养基灭菌质量不好，糖氮被破坏，抑制微生物生长，使种子菌丝自溶，产生大量泡沫，加消泡剂也无效. （二）起泡地危害 、降低生产能力 在发酵罐中，为了容纳泡沫，防止溢出而降低装量 、引起原料浪费 如果设备容积不能留有容纳泡沫地余地，气泡会引起原料流失，造成浪费. 、影响菌地呼吸 如果气泡稳定，不破碎，那么随着微生物地呼吸，气泡中充满二氧化碳，而且又不能与空气中氧进行交换，
重建上升气泡与数字图像处理方法1
重建上升气泡与数字图像处理方法 边雨辰,冯栋，王弘毅 天津市重点实验室的过程测量与控制，学校的电气工程及其自动化 天津大学 中国天津 摘要 描述气泡上升对研究气体或液体两相流的原理是很重要的。 作为上升的气泡,重建气泡的形状可以成为进一步描述一个泡沫的坚实基础。气泡图像由两个摄像机采集；利用数字图像处理方法对图像进行预处理；模拟椭圆的参数运用霍夫转换来获取；气泡模拟椭圆模型的重建型基于这些提取参数。 关键字：数字图像处理；参数提取；气泡椭球；重建 一．介绍 在自然界和工业领域,特别是各种能源产业，例如石油和化工等行业,多相流发生频繁。两相流指的是一种特殊的流动模式混合流体力学的关系,其中他们之间一定有两种相共存和显式接口。最常见的类型是气体或液体两相流,其中最基本的模式是泡状流。泡状流在气/液两相流机制的研究中起着重要的作用，同样在泡沫柱的工业应用上也具有极大的价值。 随着科学技术的发展,各种各样的新技术应用于测量多相 流动参数。作为一种新兴的测量技术,数字图像处理广泛的应用于多
相流参数的测量,如泡沫变形、流速和天然气的分数。首先,进行初始图像处理,然后对图像中感兴趣的目标进行测定,并提取泡沫的投影参数,最后,泡沫模型的变形码，变形气泡模型运用气泡流动机制的进一步研究的参数来重建。基于数字图像处理单个图像的气泡,福特讨论了单气泡变形和运动,但泡沫的倾斜角度被忽视,水平宽度和垂直高度的气泡图像仅仅视为泡沫的轴。在研究气体高分泡沫流动中,穆雷运用数字图像处理重建了部分使用气体分布。 本文中，使用两个摄像机从垂直方向对上升的气泡进行监控，运用数字图像处理方法来处理图像，使其达到理想化的二进制图像；从泡沫图像的投影椭圆来提取参数；使两组的参数相匹配来计算三维参数和重建这个变形泡沫的椭球面模型。它提供了一条可行途径来进一步对泡沫的流动机理研究。 二．泡沫图像采集 从两个垂直的方向使用两个摄象机比使用单摄像机能更好的、更准确地对不断上升的泡沫进行监控。在这个研究中，两相流模拟实验装置是一个由200毫米×200毫米截面积和1.25米的高度的有机玻璃槽,如图1所示。它的小孔直径约2毫米，泡沫的流速、频率、大小运用 调节控制阀下面的孔隙可以控制。双摄像头的图像采集设备由两个从两个垂直的方向的摄象机组成，焦距8毫米。图像被这些是760(卧式)×575(垂直的)像素,帧速率是每秒30帧的相机拍摄。在这些条件,涂
倾斜毛细管管口气泡生长及脱离的可视化实验
https://www.360docs.net/doc/098258146.html, 倾斜毛细管管口气泡生长及脱离的可视化实验 廖强*朱恂包立炯石泳 重庆大学工程热物理研究所，重庆400030，中国摘要：本文采用高速摄影仪对滞止流体中不同管径和倾斜角度的毛细管管口的气泡生长和脱离过程进行了可视化实验研究。实验结果表明：倾斜毛细管管口气泡生长过程中，气泡首先呈半球状生长，然后在浮升力的作用下非对称生长；气泡脱离时，气泡下侧首先脱离毛细管管壁，随后在上侧管端口断裂；气泡脱离将导致液体向毛细管内部回流。随着毛细管倾角的增大，气泡的脱离直径和生长脱离周期减小；倾斜毛细管管径越小，气泡的脱离直径和生长脱离周期越小。 关键词：倾斜毛细管，滞止流，气泡生长与脱离，可视化实验 中图分类号:O359 VISUAL EXPERIMENTS ON BUBBLE GROWTH AND DEPARTURE AT THE TIP OF INCLINED CAPILLARY TUBES IN STAGNANT LIQUID Liao Qiang* Zhu Xun Bao Lijiong Shi Yong Institute of Engineering Thermophysics, Chongqing University, Chongqing 400030, China Abstract: The bubble growth and departure at the tip of inclined capillary tubes in stagnant fluid was experimentally investigated by using a high-speed visual system. The visual experiments showed that the bubble growth experienced the sphere-like growth and the unsymmetric growth stages at the tip of an inclined capillary tube. In the period of bubble departure, the bubble firstly detaches from the lower side of capillary tube end and then, departs from the tube tip at the upper edge of the capillary tube end. The flow backwards of fluid into the tube is observed after bubble departing from the tip of capillary tube. It is found that the bubble departure diameter, the cycle period of bubble growth and departure, and the fluid volume of flow backwards into tube are decreased with an increase in the inclined angle of capillary tube. A smaller internal diameter of inclined capillary tube leads to a smaller bubble departure diameter and a shorter cycle period of bubble growth and departure. Key words: inclined capillary tube, stagnant fluid，bubble growth and departure, visualization experiment 引言 在化学、核能、热力发电以及石油等工业领域的换热设备以及化工和生化反应器中广泛存在气泡的生长及脱离现象，例如气泡动力学的研究对于探讨液体核态沸腾换热的机理具有重要的作用[1-3]。直接甲醇燃料电池阳极流道内气泡的生长和脱离特性对电池阳极的传输传质特性和电池的性能具有很大的影响[4-5]。现有的核池沸腾换热模型大部分是从研究单个气泡的形成、生长和脱离以及伴2007-11- 收到初稿. *国家自然科学基金项目（No. 90410005, 90510020）, 教育部新世纪优秀人才支持计划, 高等学校博士学科点 专项科研基金（项目批准号：20050611004）. **通讯作者：廖强, 男, 40岁, 博士, 教授. E-mail:lqzx@https://www.360docs.net/doc/098258146.html,
小气泡答疑
小气泡 小气泡的原理是什么？ 答：小气泡水磨头利用强压将水的超微小气泡作用于皮肤。由于小气泡直径只有10微米，可以很容易渗进毛孔并且带走污垢，同时大量气泡在水中溶解破裂，产生大量的能量和氧负离子，由此可以杀菌，改善痘痘的问题。整个过程像做保养一样，皮肤没有破损所以敏感皮肤也适用，也无需恢复时间！ 小气泡皮肤清洁有哪些优势？ 1、相比化学去角质，超微小气泡物理去除老化细胞更加温和。 2、提升毛孔吸收水的能力，减缓干性细纹，使补水更通透。 3、彻底清洁毛孔，使水油分泌平衡，由此可以改善痘痘的问题！ 小气泡皮肤深层清洁多久做一次？经常清洁会不会对皮肤让皮肤变薄？ 答：答：人体肌肤角质在17日-28日的周期会自动掉落，随着年龄的增长会留在皮肤上，是皮肤暗淡的原因，因此定期清洁尤为重要！但不建议过度经常清洁皮肤，如果过度清洁会使皮肤表皮变脆弱降低皮肤保护能力，因此建议的施术周期为两周一次，清洁后皮肤不会变薄，因为小气泡清洁的是角质以及毛孔内部垃圾，脸部皮肤不会因此而变薄。 2、夏季可以做小气泡吗？ 答：可以，因为夏天皮脂腺分泌旺盛，可能角质层也就相对厚一些，所以要经常做面部清洁以及面部护理，在效果上因为夏天毛孔张开，对脸部清洁有非常不错的帮助。 3、用仪器吸附角质后，毛孔会不会变大？
答：在用小气泡施术前，我们会用热喷将毛孔扩大软化，这样有助于角质干净清除！进行清洁后，再给皮肤补充些养份，更有助于产品的吸收，反而会有缩小毛孔的效果。 4、脸上青春痘比较多，治疗的时候会不会有疼痛感？ 如果面部青春痘比较多的情况，在面部清洁后适当地挤压痘痘，再用敏感肌肤使用的药水来进行毛孔清洁，不会有明显的疼痛感。反而会抑制痘痘的生长。 5、治疗一次有效果吗？治疗次数应该是多久呢？ 小气泡主要是清洁毛孔，就好比是在为脸部做一次大扫除一样。整套护理不是除于功效类项目，是属于日常很有必要的护理类项目，只要你觉得皮肤脏了，堵了就需要好好清洁一下。对于黑头非常明显的朋友，做一次都会有超明显的效果。 6、它是怎样达到如此好的效果的？ 答：通过真空负压形成真空回路，将小气泡和营养液充分结合，通过特殊设计的小螺旋形洗头直接作用于皮肤，且能保持小气泡长时间接触皮肤，促进剥离作用，小气泡与吸附作用相结合，在安全没有疼痛的状态下，能深层洁面，祛除老化角质细胞，祛除皮脂，彻底清除毛囊漏斗部的各种杂质，毛囊虫及油脂残留物，同时使毛囊漏斗部充满营养物质，为皮肤提供持久的营养，使皮肤湿润细腻有光泽。 7、小气泡皮肤清洁前注意些什么？ 答：治疗当天，要仔细清洁面部，不能有化妆品残留。 8、小气泡多久做一次来进行皮肤清洁？
气泡动力学研究
气泡动力学研究 A.Shima Professor Emeritus of Tohoku University, 9-26 Higashi Kuromatsu, Izumi-ku, Sendai 981, Japan Received 17 June 1996 / Accepted 15 August 1996 摘要：为了弄清楚与空化现象密切相关的气泡的特性，气泡动力学的研究已经深入的进行并且建立了其研究领域。本文旨在结合激波动力学简单的介绍气泡动力学及其历史。 关键字：气泡、空化、脉冲压力、液体射流、冲击波、损害坑。 1引言 在1894年的英格兰，当船在高速螺旋桨推动下试运行的时候达不到设计速度。为了查清这种现象的原因而设计了一个试验并最终发现了空化现象。从那时起，空化现象的研究日益进展，因为空化现象是阻碍工作在流体环境中的水力机械性能提高的一个重要因素。 然而，现在为了根本的理解空化现象及其相关内容，人们已经意识到应该研究气泡动力学。作者研究空化现象和气泡动力学四十多年，本文简单介绍一些气泡动力学研究及其与冲击波动力学的联系。 2空化和气泡核 水在水轮机，水泵，螺旋桨和带有各种沟渠的水力机械中流过，当液体和固态水翼的表面或者沟槽壁的相对速度变得如此大以至于局部水流的静压力减小到极限压力以下时空化现象就出现了，这个极限压力被称为空化初始压力。 通常情况下当水中不满足空化条件时，称为气泡核的小气泡是不存在的，水能抵抗非常大的负压，空化现象不能轻易的发生。 然而，水中通常包含几个百分点的空气，因此在这种情况下气泡核生长称为可见的气泡和容易被告诉摄影观察到（Knapp and Hollander 1948）。这就是所谓的空化现象。 同样地，假设有一个气泡核半径为，在液体中随着温度变化而生长，气泡存在和稳 定的条件通过由静力平衡关系得到的公式给出（Daily and Johnson 1956）。 上式中σ是液体的表面张力，是液体饱和蒸汽压，P是液体压力。当上式中的值超过右 端或小于左端的值时，气泡核分别开始无限的膨胀或收缩。由此看来气泡表现出复杂的行为取决于气泡周围各种水力状况。由于这些状况存在于空化噪声，空泡腐蚀等许多现象中，所以空泡动力学的研究要澄清空化现象的机理。 3无限液体中气泡的行为 Besant (1859) 提出（在真空、无限的、非粘滞性的并且不能压缩的液体中运动的球形气泡）一个预测液体中各点压强和气泡溃灭时间的难题。 Rayleigh (1917)从理论上解决了这一难题并且得到了描述气泡运动的解析式。他的在无限的、非粘滞性的、不能压缩的液体中单个球形气泡运动公式如图示1所示。气泡的表面速 度V通过假定液体所做的功——当一个气泡由初始半径缩小到R——等于气泡运动的全部 动能获得。
气泡在液体中上升
物体和气泡在水中受到水的压强（只考虑水不考虑大气压强） P=ρ水gh 若深度相同物体和气泡在水中受到水的压强相等 物体和气泡在水中受到的压强（考虑大气压强） P=P0+ρ水gh 若深度相同物体和气泡在水中受到的压强相等 不明追问 物体所受压力的大小与受力面积之比叫做压强 定义式：p=F/S 液体压强公式推导过程：要想得到液面下某处的压强，可以设想这里有一个水平放置的“平面”，这个平面以上的液柱对平面的压力等于液柱所受的重力。 这个平面上方的液柱对平面的压力F=G=mg=ρVg=ρShg 平面受到的压强p=F/S=G/S=mg/S=ρVg/S=ρShg/S=ρgh（适用于液体） 产生浮力的原因 可用浸没在液体内的正立方体的物体来分析。该物体系全浸之物体，受到四面八方液体的压力，而且是随深度的增加而增大的。所以这个正立方体的前后、左右、上下六个面都受到液体的压力。因为作用在左右两个侧面上的力由于两侧面相对应，而且面积大小相等，又处于液体中相同的深度，所以两侧面上受到的压力大小相等，方向相反，两力彼此平衡。同理，作用在前后两个侧面上的压力也彼此平衡。但是上下两个面因为在液体中的深度不相同，所以受到的压强也不相等。上面的压强小，下面受到的压强大，下面受到向上的压力大于上面受到的向下的压力。液体对物体这个压力差，就是液体对物体的浮力。这个力等于被物体所排开的液体的重力。 水中大气泡和小气泡哪个上升的快？ 应该是大的上升的快 你可以把它们与雨点作一下对比 气泡的话,在水中受到的有水的浮力和粘滞力的作用(重力可以忽略), 气泡越大,受到的浮力越大, 气泡的速度越来越快,受到的粘性滞力也越来越大,当与浮力平衡时,气泡就匀速上升了,此时用公式表示就是F=Kv^2,KJ水的粘滞系数,F表示浮力,浮力越大,当然最后的速度也越大 牛顿粘滞定律： 对于实际流体，它是有粘滞性的。实际流体发生分层流动，因流速不同，相邻两层之间就有了相对滑动，之间存在与速度方向相切的相互作用力，我们称之为粘滞力或内摩擦力，实验表明： F=ηS（dv/dx） 此式称为牛顿粘滞定律，F为粘滞力，S为两流层之间的接触面积，dv/dx为该处的速度梯度，比例系数η叫做流体的粘度或粘滞系数，单位为Pa·s或P（1P=0.1Pa·s）。 粘滞系数（coefficient of viscosity）η： 流体粘滞性大小的量度。 流体具有粘滞性的原因： 分子力和分子的无规则热运动。 滞系数的决定因素： 粘滞系数大小由流体本身的性质、流体的温度决定。 对液体来说：温度越高，粘滞系数越小；温度越低，粘滞系数越大。
微细气泡生长及生成特性单因素影响规律研究
Abstract Microbubbles refer to bubbles whose diameter is hundreds of microns.They are small in sizeThey have many characteristics that conventional bubbles do not have,such as small size,slow rise speed,and high mass transfer efficiency.So,microbubbles have considerable potential application value in many fields,such as wastewater treatment, ultrasonic imaging,and skin cleaning.The single-factor inflencing laws of microbubble growth and formation characteristics in the PDMS chip are studied aims to stduy the inflencing laws of microbubble growth and formation characteristics based on the application of microbubbles in sewage treatment and astronauts bathing. The theory model of microbubble formation surrounded by co-flowing liquid was investigated.The mechanics conditions of the microbubble during its growth process are analyzed in detail based on the ellipsoidal assumptions.The mechanical equation of the surface tension,liquid flow tension,gas power and microbubble inertial force are established.The calculation of above-mentioned model was completed to predict the detachment volume of microbubbles in different environments based on the MATLAB and the fourth-order Runge-Kutta method. The numerical simulation experiment of microbubble formation surrounded by co-flowing liquid was investigated.The numerical simulation model was established based on the two-phase flow theory and the level set equations in COMSOL Multiphysics.The detachment volume and formation time in different environments were predicted.And the prediction of the change of the volume in the growth process of the microbubble was completed. The experiments of generation characteristics of the microbubble surrounded by co-flowing liquid was investigated.The PDMS chip based on coaxial flow focusing was processed.A microbubble generation test system was set up to study the generation characteristics of the microbubble surrounded by co-flowing liquid based on the professionally-constucted high-speed microscopic camera system(HSMCS).Image-Pro Plus,Photoshop,and MATLAB are used to process the images in the process of the microbubble generation.The characteristic parameters of the microbubble such as the detachment volume,formation time,and the centroid displacement under different conditions were obtained to investigate the influence of the liquid flow,liquid viscosity, gas pressure and the width of gas channel on generation characteristics of the microbubble.The effect of the prediction of the theoretical model and the simulation model on the detachment volume and the formation time were verified. The experiments of generation characteristics of the microbubble in microfluidic -II-
晃荡条件下气泡上升速度特性研究
第３６卷第６期一一一一一一一一一一一哈一尔一滨一工一程一大一学一学一报一一一一一一一一一一Ｖｏｌ．３６?．６ ２０１５年６月一一一一一 一一 一一一 ＪｏｕｒｎａｌｏｆＨａｒｂｉｎＥｎｇｉｎｅｅｒｉｎｇＵｎｉｖｅｒｓｉｔｙ一一一一一一一一一一一Ｊｕｎ．２０１５ 晃荡条件下气泡上升速度特性研究 宋禹林１，谭思超１，付学宽１，李小辉２ （１．哈尔滨工程大学核安全与仿真技术国防重点学科实验室，黑龙江哈尔滨１５０００１；２．中国舰船研究设计中心，湖北武汉４３００６４） 摘一要：海浪二地震等条件都会导致核动力设备中储存自由液面的设备产生剧烈的晃荡三为了分析晃荡条件下液体中的气泡行为特性，本文运用ＣＬＳＶＯＦ（ｃｏｕｐｌｅｄｌｅｖｅｌ?ｓｅｔａｎｄｖｏｌｕｍｅ?ｏｆ?ｆｌｕｉｄ）模型追踪两相流体交界面，数值模拟气泡在液体中受余弦简谐激励和自由液面影响的上升过程三计算结果显示余弦简谐激励降低了气泡纵向运动速度，而横向速度略大于激励速度；自由液面的波动在纵向上会使气泡上升速度骤然降低，甚至出现负速度，越接近自由液面横向速度峰值越大三计算结果表明晃荡运动的影响是余弦简谐激励与自由液面波动影响的叠加，晃荡条件下自由液面波动是气泡速度变化的主要因素，气泡的本身属性起次要作用三关键词：上升气泡；晃荡；ＣＬＳＶＯＦ；大空间ｄｏｉ：１０．３９６９／ｊ．ｉｓｓｎ．１００６?７０４３．２０１４０４０２３ 网络出版地址：ｈｔｔｐ：／／ｗｗｗ．ｃｎｋｉ．ｎｅｔ／ｋｃｍｓ／ｄｅｔａｉｌ／２３．１３９０．ｕ．２０１５０４２８．１１１５．０１７．ｈｔｍｌ中图分类号：ＴＬ３３４一文献标志码：Ａ一文章编号：１００６?７０４３（２０１５）０６?０８６５?０６ Ｓｔｕｄｙｏｎｔｈｅｃｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆｓｉｎｇｌｅｂｕｂｂｌｅｒｉｓｉｎｇｖｅｌｏｃｉｔｙｕｎｄｅｒｓｌｏｓｈｉｎｇｃｏｎｄｉｔｉｏｎｓ ＳＯＮＧＹｕｌｉｎ１，ＴＡＮＳｉｃｈａｏ１，ＦＵＸｕｅｋｕａｎ１，ＬＩＸｉａｏｈｕｉ２ （１．ＦｕｎｄａｍｅｎｔａｌＳｃｉｅｎｃｅｏｎＮｕｃｌｅａｒＳａｆｅｔｙａｎｄＳｉｍｕｌａｔｉｏｎＴｅｃｈｎｏｌｏｇｙＬａｂｏｒａｔｏｒｙ，ＨａｒｂｉｎＥｎｇｉｎｅｅｒｉｎｇＵｎｉｖｅｒｓｉｔｙ，ＨａｒｂｉｎＥｎｇｉｎｅｅｒｉｎｇＵｎｉｖｅｒｓｉｔｙ，Ｈａｒｂｉｎ１５０００１，Ｃｈｉｎａ；２．ＣｈｉｎａＳｈｉｐｄＥｖｅｌｏｐｍｅｎｔａｎｄＤｅｓｉｇｎＣｅｎｔｅｒ，Ｗｕｈａｎ４３００６４，Ｃｈｉｎａ） Ａｂｓｔｒａｃｔ：Ｏｃｅａｎｗａｖｅｓａｎｄｓｅｉｓｍｉｃｗａｖｅｓｃａｎｃａｕｓｅｖｉｏｌｅｎｔｌｙｓｌｏｓｈｉｎｇｏｆｔｈｅｆｒｅｅｌｉｑｕｉｄｓｕｒｆａｃｅｉｎａｃｏｎｔａｉｎｅｒ．Ｉｎｏｒｄｅｒｔｏａｎａｌｙｚｅｔｈｅｂｅｈａｖｉｏｒｏｆｒｉｓｉｎｇｂｕｂｂｌｅｉｎｌｉｑｕｉｄｕｎｄｅｒｔｈｅｃｏｎｄｉｔｉｏｎｏｆｓｌｏｓｈｉｎｇ，ｔｈｉｓｐａｐｅｒｕｓｅｓｔｈｅＣＬＳＶＯＦ（ｃｏｕｐｌｅｄｌｅｖｅｌ?ｓｅｔｔｈｅｖｏｌｕｍｅ?ａｎｄ?ｆｌｕｉｄ）ｍｏｄｅｌｔｏｓｉｍｕｌａｔｅｔｈｅｔｗｏ?ｐｈａｓｅｆｌｕｉｄｉｎｔｅｒｆａｃｅ，ｏｂｔａｉｎｉｎｇｔｈｅｒｉｓｉｎｇｂｕｂ?ｂｌｅｉｎｔｈｅｌｉｑｕｉｄｗｉｔｈｃｏｓｉｎｅｈａｒｍｏｎｉｃｅｘｃｉｔａｔｉｏｎｃｏｎｄｉｔｉｏｎｏｒｗａｖｅｏｆｆｒｅｅｓｕｒｆａｃｅｃｏｎｄｉｔｉｏｎ．Ｃａｌｃｕｌａｔｉｏｎｒｅｓｕｌｔｓｓｈｏｗｔｈａｔｃｏｓｉｎｅｈａｒｍｏｎｉｃｅｘｃｉｔａｔｉｏｎｒｅｄｕｃｅｓｔｈｅｂｕｂｂｌｅｌｏｎｇｉｔｕｄｉｎａｌｖｅｌｏｃｉｔｙｔｒａｎｓｖｅｒｓｅｖｅｌｏｃｉｔｙｉｓｓｌｉｇｈｔｌｙｂｉｇｇｅｒｔｈａｎｔｈｅｍｏｔｉｖａｔｉｏｎｓｐｅｅｄａｎｄｔｈｅｗａｖｅｏｆｆｒｅｅｓｕｒｆａｃｅｗｉｌｌｍａｋｅｔｈｅｂｕｂｂｌｅｒｉｓｉｎｇｖｅｌｏｃｉｔｙｐｌｕｍｍｅｔａｎｄｅｖｅｎｌｅａｄｔｏｎｅｇａ?ｔｉｖｅｓｐｅｅｄ．Ｔｈｅｌａｔｅｒａｌｖｅｌｏｃｉｔｙｐｅａｋｉｎｃｒｅａｓｅｓｇｒａｄｕａｌｌｙｃｌｏｓｅｒｔｏｔｈｅｆｒｅｅｓｕｒｆａｃｅ．Ｃａｌｃｕｌａｔｉｏｎｒｅｓｕｌｔｓｐｒｏｖｅｔｈａｔｓｌｏｓｈｉｎｇｉｓｔｈｅｏｕｔｃｏｍｅｏｆｓｕｐｅｒｐｏｓｉｔｉｏｎｗｉｔｈｃｏｓｉｎｅｈａｒｍｏｎｉｃｅｘｃｉｔａｔｉｏｎａｎｄｗａｖｅｏｆｆｒｅｅｓｕｒｆａｃｅａｎｄｔｈｅｄｅｎｓｉｔｙｄｉｆｆｅｒｅｎｃｅｂｅｔｗｅｅｎａｉｒａｎｄｗａｔｅｒｉｓｏｎｅｏｆｔｈｅｄｒｉｖｉｎｇｆｏｒｃｅｓｏｆｂｕｂｂｌｅｍｏｔｉｏｎ．Ｉｎｓｌｏｓｈｉｎｇｃｏｎｄｉｔｉｏｎ，ｆｌｕｃｔｕａｔｉｏｎｏｆｆｒｅｅｓｕｒｆａｃｅｉｓｔｈｅｍａｉｎｆａｃｔｏｒｏｆｃｈａｎｇｅｓｉｎｂｕｂｂｌｅｖｅｌｏｃｉｔｙ，ｗｈｉｃｈｐｒｏｖｅｄｔｈａｔｔｈｅａｔｔｒｉｂｕｔｅｏｆｂｕｂｂｌｅｉｓｔｈｅｗｅａ?ｋｅｓｔｆａｃｔｏｒ． Ｋｅｙｗｏｒｄｓ：ｒｉｓｉｎｇｂｕｂｂｌｅ；ｓｌｏｓｈｉｎｇ；ＣＬＳＶＯＦ；ｌａｒｇｅｓｐａｃｅ收稿日期：２０１４?０４?０７．网络出版时间：２０１５?０４?２８．基金项目：黑龙江省青年学术骨干支持计划资助项目（１２５４Ｇ０１７）； 核安全与仿真技术国防重点学科实验室基金资助项目（ＨＥＵＦＮ１３０５）． 作者简介：谭思超（１９７９?），男，教授，博士生导师．通信作者：谭思超，Ｅ?ｍａｉｌ：ｔａｎｓｉｃｈａｏ＠ｈｒｂｅｕ．ｅｄｕ．ｃｎ． 一一行驶在海洋中的船舶二运行在陆地上的核电站，在遇到风浪二地震等外界激励时，会使存在自由液面的容器产生剧烈的晃荡三强烈的晃荡产生的复杂流场必然对气泡的运动有着不可忽视的影响三正常工况下运行的蒸汽发生器二除氧器还有事故工况下未停止运行的反应堆都存在大量的气泡，气泡的大小二形状及运动规律等对气液传热传质都有这种影响，因此晃荡对气泡运动行为的影响或危机设备的安全运行三而这方面的研究却未见诸公开报道，因此有必要对晃荡条件下气泡的运动行为特性进行研究三 １一数值计算方法与静水中气泡的上升 气泡运动的数值模拟主要通过界面追踪法来实现，ＬｅｖｅｌＳｅｔ和ＶＯＦ都是优秀的界面跟踪方法，Ｃ．Ｗ．Ｈｉｒｔ［１］首次将ＶＯＦ方法应用到数值模拟晃荡现象中，ＳｕｓｓｍａｎＭ［２］等将ＬｅｖｅｌＳｅｔ方法应用于数值模拟气泡的上升运动三ＳｏｎＧ［３］等完善了ＣＬＳＶＯＦ方法，相比其他两相流界面追踪方法，ＣＬＳＶＯＦ方法计算得更精准并且收敛的更快三耦合ＬｅｖｅｌＳｅｔ方法与ＶＯＦ方法关键的过程在于相函数的耦合方法三相函数耦合又分为以ＬｅｖｅｌＳｅｔ方法为主还是以ＶＯＦ方法为主，这里选以ＬｅｖｅｌＳｅｔ为主的ＬｅｖｅｌＳｅｔ－相界面法为例，式（１）是一种最基本的耦合方法，利用Ｈｅａｖｉｓｉｄｅ函数建立了ＬｅｖｅｌＳｅｔ函数φ（ｘ，ｙ，ｚ，ｔ）和ＶＯＦ流体体积函数ｆ（Ω，ｔ）的关系［４］：