IMECH-IR  > 国家微重力实验室
环状流稳定性的实验研究
Alternative TitleExperimental research on the hydrodynamic instability of Annular Flow
段隆盛
Thesis Advisor段俐
2019-05-31
Degree Grantor中国科学院大学
Place of Conferral北京
Subtype博士
Degree Discipline一般力学与力学基础
Keyword环形液池,热毛细对流,转捩途径,流动稳定性,混沌,旋转-热毛细对流,波动特性
Abstract

  空间晶体材料制备具有广阔的应用前景,微重力条件下由表面张力不均匀驱动的热毛细对流是影响晶体质量的主要因素,环形液池是提拉法晶体生长的微重力流体力学研究模型。对热毛细对流流动稳定性的研究有助于促进对其振荡特征、转捩及转捩途径、波动结构等非线性特性的认知。配合实践十号空间实验以及空间站首选项目,本文通过地面实验在多种模型系统中开展了热毛细对流振荡及转捩特性的研究,分析了对流通向混沌的转捩途径及波动特性,创新性的研究了内加热柱旋转与热毛细对流耦合作用(后文统称旋转-热毛细对流)时的波动结构,总结得到了一系列有价值和创新性的实验成果,主要的工作内容有:

  设计并搭建了四种模型系统,利用这些模型研究了不同加热方式下热毛细对流流动失稳的临界条件及振荡特性;配合实践十号空间实验开展地面实验研究,探讨了热毛细对流的振荡转捩途径;结合空间站首批项目的要求,设计并搭建了中心柱转速及转向可控的地面实验模型,开展了旋转-热毛细对流耦合作用时环状流流动稳定性的研究。

  利用热电偶对流体内部特征点的温度信号进行测量,对热毛细对流失稳的临界条件及振荡特性进行研究,通过改变实验介质的Prandtl数及环状流的高径比Ar开展实验,得到了内加热及内制冷两种不同加热方式模型中流动失稳的临界条件。在小Bond数浅液层的环状流体系中,临界Ma数与Bo数间呈正相关的关系,浮力对流的存在能够起到稳定流动的作用,两种不同加热方式模型中的流动有着相似的规律。加热方式对热毛细对流稳定性的影响主要体现为波动结构的差异,内加热模型中,随着Ma数的增加,热毛细对流失稳时温度场结构首先转变为沿着径向传播的驻波,依次经历:稳态-驻波-单向行波-双向行波-行波耦合叠加的转变过程;内制冷模型中,热毛细对流失稳时的波动结构为沿着周向传播的行波,其转变规律遵循:稳态-单向行波-双向行波-行波叠加。

  配合实践十号空间实验,通过热电偶对流场内特征点的温度信号进行测量,分析得到了内加热模型中热毛细对流失稳并发展为混沌状态的三种转捩途径,分别为准周期转捩途径、含有倍周期分岔的转捩途径及含有切分岔的转捩途径;利用功率谱和时频分析的方法得到了热毛细对流的振荡转捩特性;同时比较了同一区域温度振荡和位移振荡的关系,环形液池内热毛细对流失稳主要表现为温度振荡和自由面位移振荡,二者在转捩途径上具有较好的一致性;借助混沌理论的最大李雅普诺夫指数和排列熵定量分析了热毛细对流转捩过程的混沌特性,李雅普诺夫指数的非负性反映了液池内的流动具有混沌特性而不是随机状态,最大李雅普诺夫指数和排列熵均随着Ma数的增加而增大,表明液池内的流动正逐渐向更加复杂的混沌状态发展。

  配合空间站首批项目,通过红外热像仪对流体自由面温度场进行观测,探讨旋转-热毛细对流耦合作用时的波动特性,分析了中心柱转动速率及转动方向对温度场波动结构的影响。实验得到了两类流动不稳定性规律,在小转速流动不稳定中,较小转速条件下(0)流动失稳时首先发展为沿周向传播的行波,并且行波的传播方向与中心柱的转动方向相反;大转速流动不稳定规律是指当中心柱的旋转速率较大时(10rpm),温度场的波动结构首先表现为传播方向与中心柱转动方向一致的行波;分析了转动速率及转动方向对临界条件的影响,通过图像处理及时空演化等手段对流动模式转变过程中包括传播角及波数等波动特性进行了研究,总结了旋转-热毛细对流耦合作用时温度场波动结构的转变规律。

Other Abstract

Space crystal material preparation has a broad application prospect. Thermocapillary convection which driven by uneven surface tension under microgravity is the main factor to affect crystal quality. Annular liquid pool is a microgravity hydrodynamics research model for crystal growth by Cz method. The study on the stability of thermocapillary convection is helpful to promote the cognition of the characteristics of thermocapillary oscillation, transition and transition route, as well as the nonlinear characteristics of wave structure. Preferred with experiment and SJ-10 and Space station project, we conducted a variety of experiments for thermocapillary convection oscillation and transition characteristics, analyzed the osicillation transition routes and wave characteristics, the innovative research have innner heating and rotating coupling with thermocapillary convection (later referred rotation - thermal convection) and analyzed the wave structrue, summed a series of valuable and innovative experiment results, the main work contents are as follows:

Four model systems are designed and constructed, and the critical conditions and oscillation characteristics of thermocapillary convection under different heating modes are studied.The ground experiment was carried out in cooperation with the SJ-10 space experiment to explore the oscillation transition routes of thermocapillary convection. According to the requirements of the project of the Space station, a ground experimental model with controllable rotation speed and steering of the central column was designed and built.

We measured temperature signals of feature points inner the fluid by thermocouples, the critical condition and oscillation properties were studied. Experiments were carried out by changing the experimental medium's Prandtl number as well as Ar number, and obtained the critical condition of oscillation in two different heating modes. In the annular flow system with shallow liquid layer and small Bond number, the critical Ma number is positively correlated with the Bo number, and the existence of buoyancy convection can play a role in stabilizing the convection. The two models with different heating modes share similar laws. Heating mode's influence on the stability of thermocapillary convection mainly embodied in volatility structure differences, in internal heating model, with the increase of number of Ma, thermocapillary drain steady temperature field structure of the first into a standing wave along the radial distribution, and follows: steady state - standing wave - one-way traveling wave - bidirectional traveling wave - traveling wave superposition. In the internal refrigeration model, the wave structure corresponding to the steady loss of thermocapillary convection is the traveling wave propagating along the circumferential direction. The transformation rule of the wave structure follows: steady-state - one-way traveling wave - bidirectional traveling wave - traveling wave superposition.

In order to cooperate with SJ-10 space experiments, based on thermocouples, the temperature signals inner the fluid were measured, three oscillation transition routes of thermocapillary convecton were obtained respectively, quasi-bifurcation transition route, containing the period-doubling bifurcation transition route and contains tangent bifurcation transition route. Oscillation transition characteristics of thermocapillary convection were obtained by power spectrum and time frequency analysis. At the same time, the relationship between temperature oscillation and displacement oscillation in the same region was compared. The oscillation of thermocapillary convection in the annular liquid layers was mainly characterized by temperature oscillation and displacement oscillation. By using chaos theory of the maximum lyapunov index and permutation entropy, we quantitative analyzed the transition routes. Lyapunov index was negative showed that the flow of the liquid pool have chaotic characteristic instead of random state, maximum lyapunov index and permutation entropy increased with Ma number, showed that the flow of the liquid pool is developing gradually to a more complex chaotic state.

In cooperation with the Space station project, the temperature field of free surface was observed by the infrared thermal imager.Two kinds of flow instability laws were obtained in the experiments. In the flow instability at a small rotating speed, the convection at a small rotating speed condition (0

Language中文
Document Type学位论文
Identifierhttp://dspace.imech.ac.cn/handle/311007/79107
Collection国家微重力实验室
Recommended Citation
GB/T 7714
段隆盛. 环状流稳定性的实验研究[D]. 北京. 中国科学院大学,2019.
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