IMECH-IR  > 流固耦合系统力学重点实验室
混合边界条件下的空泡及约束界面响应研究
Alternative TitleBubble dynamics and boundary responses in complex constrained conditions
李泓辰
Thesis Advisor王一伟
2020-05-23
Degree Grantor中国科学院大学
Place of Conferral北京
Subtype硕士
Degree Discipline工程力学
Keyword空泡动力学,气液界面,射流,界面不稳定性,流固耦合
Abstract

空泡动力学作为一个历久弥新的研究方向,不仅在诸如水力机械、船舶与鱼雷减阻、舰船毁伤和海底勘探等传统领域中有着广泛的研究和应用背景,而且在许多新兴方向中扮演着越来越重要的角色,例如表面清洗、空化杀菌和生物医学等。在诸多实际应用场景中,空泡产生和脉动的环境往往是受复杂边界条件约束的。由于空泡动态行为与其附近边界属性紧密相关,进一步探索不同边界条件下的空泡脉动以及相应的界面响应尤为必要。因此,本文对三类约束条件,即刚性壁面、自由液面和柔性边界条件下的空泡脉动和相应的约束界面响应开展了实验和数值模拟研究。具体地,开展了自由液面和刚性壁面双边界条件下的空泡脉动和自由面射流、平板间液滴内的空泡动力学与界面射流、管道约束条件下的空泡动力学和维度效应以及柔性边界约束下的空泡动力学与柔性界面响应的研究。该工作可为进一步认识混合边界条件下气液界面演变、空蚀、液体射流和流固耦合行为,以及海洋工程、水力机械和生物医学等场景的相关应用提供参考。本文主要包含以下几方面工作:

1)对自由液面和刚性壁面双边界约束条件下的空泡动力学和自由面射流行为进行了研究。具体地,首先基于量纲分析方法对该问题的无量纲控制参数进行推导,并重点讨论无量纲距自由面距离和壁面距离对气泡脉动和自由面射流形态的影响。进一步地,基于OpenFOAM可压缩两相流求解器compressible-InterFoam对该问题进行了轴对称模型的数值模拟,模拟结果与实验结果吻合良好。另外,还对双边界影响下空泡脉动导致的复杂自由面射流行为进行了分类,并揭示了不同射流行为的形成机理。

2)为加深对限定几何流体域内刚性壁面对气液界面演化影响的认识,开展了激光诱导空化致板间液滴界面不稳定性和射流行为的实验和数值模拟工作。具体地,采用compressibleInterFoam求解器,结合大涡模拟方法,对该问题进行了三维对称模型的数值模拟。模拟得到的气液界面演化,包括液滴外缘界面和空泡界面的结果与实验结果吻合良好。针对上述两种气液界面,对冲击波和空泡体积振荡导致的界面射流形成机理进行了揭示,并依据射流行为,划分了三类界面不稳定状态。结合量纲分析结果,讨论了无量纲控制参数初始能量、接触角和表面曲率等对界面射流行为的影响。

3)开展了单开口刚性管道内激光空泡脉动及其溃灭维度效应的实验和数值模拟研究。其中,重点对空泡第一脉动周期的膨胀、收缩和溃灭行为进行了讨论,分析了收缩和溃灭阶段气液界面产生的不稳定性和撕裂现象。其次,主要对无量纲初始能量和管道长径比对空泡脉动的影响进行了讨论。根据空泡第一脉动周期收缩阶段后期和溃灭阶段的界面演化与射流特点,揭示了管道约束下空泡溃灭的维度效应,并结合精细化界面模拟结果和判别相图,对三类溃灭模式进行了分类。

4)开展了柔性材料约束条件下的空泡动力学及柔性边界响应的实验研究。重点探究了不同材料参数和空化发生位置条件下,电火花空泡同柔性膜的相互作用,讨论了相应的空泡迁移行为和射流特点,以及柔性膜的变形和空蚀行为。在此实验装置基础上,结合三维数字图像相关(3D-DIC)技术,创新性地搭建了空泡与软材料流固耦合行为的三维动态分析系统,实现了空泡脉动与固体材料应变场的同步捕捉。

Other Abstract

As a long-lasting research area, bubble dynamics does not only have an extensive research background in traditional fields such as hydraulic machinery, drag reduction of ship and torpedo, warship damage, and underwater exploring, but also plays an increasingly important role in many emerging directions, such as surface cleaning, cavitation-induced sterilization, biomedical engineering and so on. In the practical application scenarios, the generation and pulsation of bubbles are often constrained by complex boundary conditions. Due to the close relationship between bubbles and its nearby boundaries, it is necessary to further explore bubbles’ behaviors and the corresponding boundary responses under the influences of different boundary conditions. Therefore, in this thesis, experiments and numerical simulations are performed to investigate the bubble oscillation and boundary responses on three types of constraints, namely, the rigid wall, the free surface, and soft solids. Specifically, four typical cases are discussed, i.e., bubble dynamics and liquid jet behaviors under the combined restriction of a rigid wall and free surface, bubble dynamics and interfacial jets within a droplet between plates, bubble pulsation and its dimensional effect under the constraint of a rigid tube, and bubble dynamics and responses of soft materials influenced by the soft constraint. These works can provide references for a better understanding of issues related to the evolution of gas-liquid interface, cavitation erosion, liquid jets and fluid-solid interaction under complex boundary conditions, and provide support for relevant applications such as marine engineering, hydraulic machinery, and biomedical engineering. The thesis includes the following aspects:

(1) The bubble dynamics and liquid jets on free surface under the combined constraints of a rigid wall and the free surface are studied. Particularly, the dimensionless controlling parameters are derived based on the dimensional analysis method, and effects of the dimensionless distance away from the free surface and the dimensionless distance away from the rigid wall are discussed on aspects of bubble pulsation and the jet morphology. Further, the compressible two-phase solver CompressibleInterFoam in OpenFOAM is used for an axisymmetric numerical simulation. The simulation results agree well with the experimental observation. In addition, the complex jet behaviors caused by bubble pulsation are classified and the mechanism of the formation of various jet behaviors is revealed.

(2) In order to deepen the understanding of interfacial gas-liquid evolution in a limited geometric fluid domain under the influence of rigid walls, experiments and simulations are carried out for the cavitation-induced interfacial instability and jet behaviors of a droplet between plates. Specifically, combining the large eddy simulation, the compressibleInterFoam is still used to simulate this progress in a three-dimensional symmetrical model. Simulation agrees well with experiments on both the evolution of the outer edge of the droplet and the interface between the bubble and droplet. For the above two kinds of gas-liquid interfaces, the formation mechanism of interfacial jets caused by shock waves and volume oscillations is revealed, and effects of dimensionless controlling parameters such as initial energy, contact angle ,and interfacial curvature on the interfacial jet behaviors are discussed.

(3) The pulsation of a laser-induced bubble in a rigid tube with a single opening and the dimensional effect during collapse are studied experimentally and numerically. Remarkably, the first cycle of bubble pulsation is mainly discussed on expansion, contraction, and collapse stages, and the instabilities on the gas-liquid interface and the detachment phenomenon are analyzed. Secondly, effects of the dimensionless initial energy and tube’s length-to-diameter ratio on bubble’s oscillation are discussed. Furthermore, the dimensional effect during bubble collapse under the constraint of a tube is revealed based on the characteristics of the interfacial evolution and jet behaviors in the late contraction and collapse stages of bubble’s first pulsating cycle. At last, three regimes of collapse are classified according to the refined interfacial simulation and a classification phase diagram.

(4) Experimental research is developed on bubble dynamics and boundary responses under the constraint of soft materials. Remarkably, the investigation is performed on the interaction of the EDM-induced bubble and soft membranes, the characteristics of bubble’s migration and jet behaviors, and the corresponding deformation and erosion behaviors of soft solids in different conditions of martial properties and initial cavitation position are discussed. Further, on the basis of the above experimental setup, a three-dimensional dynamic analysis system for the fluid-solid interaction of cavitation bubbles and soft materials is innovatively constructed combing three-dimensional digital image correlation (3D-DIC) method, and thus the synchronous observations of bubble pulsation and the strain filed of solid materials are obtained based on this experimental system.

Language中文
Document Type学位论文
Identifierhttp://dspace.imech.ac.cn/handle/311007/81931
Collection流固耦合系统力学重点实验室
Recommended Citation
GB/T 7714
李泓辰. 混合边界条件下的空泡及约束界面响应研究[D]. 北京. 中国科学院大学,2020.
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