二元复杂等离子体系统中密度波的研究

发布时间：2018-03-14 11:14

本文选题：二元复杂等离子体　切入点：微重力　出处：《东华大学》2017年硕士论文　论文类型：学位论文

【摘要】：复杂等离子体实验作为一门新兴的研究课题正吸引着研究学者们越来越多的关注。随着复杂等离子体系统中各种物理现象及结构的发现,作为一个可以从原子层面模拟物理性质的媒介,其独特的优势逐渐突显。复杂等离子体实验由最初的地面实验发展到微重力条件下的实验,从单元系统发展到二元以及多元系统,经历了卓越的成长。较为经典的国际空间站实验装置PK-3 Plus服役多年,研究成果丰富。复杂等离子体系统在研究晶格、密度波、分相等相关动力学过程中,给学者们提供了独特的视角以及不一样的发现。实验中发现了波传递的现象,且这些波是自激产生的,由此引发了人们对复杂等离子体自激密度波的实验探索。在一定的实验条件下,自由能的存在是激发密度波的前提条件。一元复杂等离子体系统中波的传播会出现波纹的断裂、分叉等现象,这些现象的微观研究对许多宏观现象的解释有着重要作用。二元复杂等离子体系统由于不同大小颗粒在系统中的受力不同而出现自主分相的过程,较小的颗粒会占据尘埃粒子云的内圈空间,较大颗粒与较小颗粒分相并占据尘埃云的外部空间。分据不同区域的两种颗粒之间存在着一圈较为明显的分界面。复杂等离子体系统中的密度波由于其所在的传播介质即尘埃颗粒的不同而具有不同的传播频率,因此二元系统中的波在小颗粒所在的内圈以及大颗粒所在的外圈具有不同的传播频率。密度波的传播方向由尘埃云中间的空洞向周围呈球面状传播,当以小颗粒为传播介质的波以一定的频率向外传播至界面时,分界面前后不同大小的颗粒相互碰撞,导致密度波以后者即波在大颗粒中传播的频率反射回小颗粒所在的内圈区域。又由于整个系统的耗散性,以小颗粒为介质的波在传播到大颗粒的区域后渐渐耗散消失。为了验证反射波的存在,我们辨别颗粒,做出了颗粒动能周期图,从中我们可以清楚的看到颗粒动能的反向变化趋势。另一方面为了了解介质即尘埃颗粒在波传播中的运动学过程我们进行了颗粒的追踪,追踪发现一个波前传播周期内,大颗粒振动一个周期,而小颗粒却表现出两个不同振幅,不同频率的周期。颗粒的振动形式受到波的影响,当单一形式的波传播到介质时,介质以该波的频率以及传递到它的能量大小(振幅)振动;当同时有两种形式的波当波的一种形式(实验中以正方向传播的入射波)传播到介质时,介质以该波的频率及能量大小(振幅)来振动,而后当另一种波(实验中的反射波)传播到该介质时,反射波与入射波耦合,介质同时表现出这两种振动的特征。整个过程很好的说明了分界面上密度波传播的特点以及波在传播的过程中介质的作用。
[Abstract]:As a new research subject, complex plasma experiment is attracting more and more attention of researchers. With the discovery of various physical phenomena and structures in complex plasma systems, As a medium capable of simulating physical properties at the atomic level, its unique advantages have gradually emerged. Complex plasma experiments have evolved from initial ground experiments to experiments under microgravity. The development from element system to binary and multivariate system has experienced remarkable growth. PK-3 Plus, a more classical experimental device of the International Space Station, has been in service for many years, with rich research results. Complex plasma system is studying lattice, density wave, In the process of equalization correlation dynamics, it provides a unique angle of view and a different discovery for scholars. The phenomenon of wave transfer has been found in the experiment, and these waves are generated by self-excitation. Under certain experimental conditions, the existence of free energy is the prerequisite for the excitation of density waves. The microscopic study of these phenomena plays an important role in the explanation of many macroscopic phenomena. Due to the different forces of particles of different sizes in the system, the binary complex plasma system appears the process of independent phase separation. Smaller particles occupy the inner ring of the dust cloud, The larger and smaller particles separate and occupy the outer space of the dust cloud. There is a more obvious interfacial between the two particles in different regions. The density wave in the complex plasma system is due to its propagation. The seeding medium, that is, the dust particles, has different propagation frequencies. Therefore, the waves in binary system have different propagation frequencies in the inner circle of small particles and the outer circle of large particles. The propagation direction of density wave is spherical from the hole in the middle of dust cloud to the surrounding area. When waves with small particles as propagation medium propagate outward at a certain frequency to the interface, particles of different sizes collide with each other before and after the interface. The density wave is reflected back to the inner circle of the small particle by the frequency of the latter wave propagating in the large particle, and because of the dissipation of the whole system, Waves in the medium of small particles gradually dissipate and disappear as they travel to the region of large particles. In order to verify the existence of the reflected waves, we identify particles and make a kinetic energy periodic map of the particles. On the other hand, in order to understand the kinematics of the dust particles in the wave propagation, we have tracked the particles, and found that in a wave front propagation period, Large particles vibrate in a period, while small particles exhibit two periods of different amplitudes and different frequencies. The vibrational form of particles is affected by waves, when a single form of wave propagates to the medium, The medium vibrates at the frequency of the wave and the magnitude (amplitude) of the energy transmitted to it; when there are two forms of wave at the same time (the incident wave propagating in a positive direction in the experiment), The medium vibrates at the frequency and energy level (amplitude) of the wave, and then when another wave (the reflected wave in the experiment) propagates to the medium, the reflected wave is coupled with the incident wave. The whole process shows the characteristics of density wave propagation on the boundary surface and the function of the medium in the process of wave propagation.
【学位授予单位】：东华大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O53

【相似文献】