IMECH-IR  > 国家微重力实验室
内角毛细界面行为和平行板间隙内流动特性的研究
英文题名The Study of Capillary Surface Behavior in Interior Corners and Flow Characteristic Between Parallel Plates
韩志一1,2
导师段俐
2018-05-24
学位授予单位中国科学院大学
学位授予地点北京
学位名称硕士
学位专业一般力学与力学基础
关键词毛细界面 内角 毛细流动 平行板 壅塞
摘要

流体毛细界面行为和流动特性的研究在空间流体管理和材料制备等方面有着重要的应用价值。在微重力环境中,流体失去重力的约束后自由度增加,无疑给流体的储存、控制和传输增添了难度,我们只能利用内聚力、附着力、表面张力等次级力来管理流体。研究流体在内角处和平行板间隙内的界面行为和流动特性对空间流体管理有着重要的指导意义。

本文研究了液体在理想尖内角、圆内角和内角角度大于180度的内角(优角)处的毛细界面行为,分析了液体在平行板间隙内的毛细爬升规律,最后对平行板开口毛细流道的流动特性展开了研究。

对液滴在圆内角处的毛细界面行为进行了理论分析和数值模拟,并与理想尖内角处的液滴毛细界面行为做对比,得到了定性和定量的新规律,与理想尖内角不同的是,液滴的毛细界面行为不仅与与接触角θ、内角的角度2α有关,还与圆内角的圆角半径r、液滴的体积V有关。

对液滴在内角角度大于180度的内角处的毛细界面行为也进行了理论分析和数值模拟,得到了一些新的现象,液滴在大于180度的一种对称内角系统中,如果接触角和内角角度的一半满足θ+α<π,液滴就能稳定存在于对称内角系统的中心位置,反之,如果接触角和内角角度的一半满足θ+α>π,液滴将自发地向两侧中的任意一侧移动,接触角和内角角度的一半之和越大,液滴偏向一侧的程度越大。

对液体在平行板间隙内的毛细爬升问题进行了理论分析和数值模拟,液体在毛细力的驱动下在平行板间隙内自发地爬升,与圆管毛细爬升、多孔介质内的液体爬升进行对比,三者最开始进行毛细爬升那一刻都符合液体爬升高度与时间的平方成正比的规律。当毛细爬升很长一段时间后,液体在平行板间隙内的毛细流动和液体在圆管内的毛细流动都可以视作Poiseuille流动,可以求出液体爬升高度与时间的二分之一次方成正比的规律。

对于平行板开口毛细流道的流动研究,通过数值模拟获得流体在毛细流道内的流动信息和直观的流动图像,并发现了前人研究中尚未发现的新现象,即在超临界流量状态下,进入流道内的气泡的体积随着总体积流量的增大而增大。利用理论分析证实了本文数值模拟得到的气泡体积随总体积流量增大而增大这一规律的正确性。首次开展常重力环境下的平行板开口毛细流道实验,进一步验证了气泡体积随体积流量增大而增大的这一规律,充分说明了本文获得这一结论的可靠性。

英文摘要

To study the behavior of capillary surfaces and flow characteristic is very essential for Space Fluid Management, material preparation and many other industries. Under microgravity, the degree of freedom of fluids increases due to lose gravity, which becomes harder to storage, control and transport them. The only thing we can do is how to use adhesion, cohesion and surface tension to achieve fluid management. The study of flow characteristic and interfacial behavior of fluids in interior corners and between parallel plates provides important instruction significance in Space Fluid Management.

In this thesis, we studied the capillary surfaces of liquids in ideal sharp interior corner, rounded interior corner and reflex interior corner with a reflex angle. Also, we analyzed capillary rise of liquid between parallel plates and studied the flow characteristic in open capillary channels with parallel plates.

Theoretical analysis and numerical simulation are performed to research capillary surfaces of liquid drops in rounded interior corners. Comparing with sharp corners, there are some different characteristics of behaviors of capillary surfaces in rounded corners. The behaviors of capillary surfaces in rounded corners are depend on not only contact angle θ and the degree of interior corners 2α, but also the radius of rounded corners r and the volume of liquid drops V, which are dramatically different in sharp corners.

Theoretical analysis and numerical simulation are also performed to research capillary surfaces of liquid drops in reflex interior corners. Some new phenomena were found during simulation. There is a system with a liquid drop and two reflex interiors which are symmetrical distribution in a special way. If contact angle and the half of degree of interior corners satisfy θ+α<π, the liquid drop can be fixed in the center of system. Otherwise, If contact angle and the half of degree of interior corners satisfy θ+α>π, the liquid drop will move to either side of two sides of system. The bigger the sum of contact angle and the half of degree of interior corners is, the greater is the degree of bias to one side.

Theoretical analysis and numerical simulation are still performed to research capillary rise of liquid between parallel plates. Liquid rises automatically due to capillary force between parallel plates. At the beginning of capillary rise, the height of capillary rise is proportional to the square of time, which is the same with capillary rise in cylindrical tubes and porous media. After capillary rise for a very long time, capillary flow between parallel plates and in cylindrical tubes can be assumed as Poiseuille flow, which can lead that the height of capillary rise is proportional to the square root of time.

To study the open capillary channel flow, we use numerical simulation and obtain much information about flow. There is a phenomenon which is inconsistent with other people’s conclusion. We found that the volume of the ingested bubbles increases when the flow rate is increased in various supercritical flow rates. We prove that this phenomenon is reasonable theoretically. Furthermore, we perform experiment under normal gravity environment for the first time and again verify that phenomenon is reasonable, which illustrates our conclusion is correct and unbreakable.

语种中文
文献类型学位论文
条目标识符http://dspace.imech.ac.cn/handle/311007/73189
专题国家微重力实验室
作者单位1.中国科学院力学研究所
2.中国科学院大学
推荐引用方式
GB/T 7714
韩志一. 内角毛细界面行为和平行板间隙内流动特性的研究[D]. 北京. 中国科学院大学,2018.
条目包含的文件
文件名称/大小 文献类型 版本类型 开放类型 使用许可
The Study of Capilla(4935KB)学位论文 开放获取CC BY-NC-SA请求全文
个性服务
推荐该条目
保存到收藏夹
查看访问统计
导出为Endnote文件
谷歌学术
谷歌学术中相似的文章
[韩志一]的文章
百度学术
百度学术中相似的文章
[韩志一]的文章
必应学术
必应学术中相似的文章
[韩志一]的文章
相关权益政策
暂无数据
收藏/分享
所有评论 (0)
暂无评论
 

除非特别说明,本系统中所有内容都受版权保护,并保留所有权利。