激波强度对多边形界面演化影响的研究

发布时间：2018-03-08 08:12

本文选题：Richymyer-Meshkov不稳定性　切入点：正方形界面　出处：《中国科学技术大学》2017年硕士论文　论文类型：学位论文

【摘要】：当一道激波穿过具有初始扰动的流体界面时,激波前后的压力梯度和界面前后的密度梯度不共线会导致流场中产生斜压涡量,涡量随时间不断积累,并促使界面上的扰动不断增长,界面逐渐失稳,最终发展为湍流混合,这种现象被称为Richtmyer-Meshkov不稳定性(简称RMI)。RMI在惯性约束核聚变、超燃冲压发动机等工程问题中有重要的应用价值,在流动不稳定性、可压缩流动、湍流等问题中也有重要的学术意义。自提出以来,RMI就引起了诸多关注,目前研究较多的是弱激波冲击下的RMI问题,界面形状多为气柱、球形气泡和单模界面,而实际工程应用中的激波强度可能较大,会给流场带来更强的压缩效应,而流体界面形状也较为复杂。本文主要围绕不同强度的平面激波与正方形界面相互作用以及汇聚激波与正方形/正六边形界面相互作用的RMI问题展开相关工作,以说明可压缩效应的影响。本文第一项工作是运用实验室已有的VAS2D程序对平面激波与正方形Air-SF6 和 Air-He界面的相互作用进行了数值研究,探究了不同压缩效应下的波系结构和界面的演化发展,定量研究了界面轴向和展向的变形情况,对不同强度激波冲击下流场的可压缩效应进行了分析;研究了上游涡对的运动,得出各工况下涡对轴向运动和涡间距的变化特点;对数值环量进行了研究,与经典模型进行对比,得出了匹配条件,进行了误差分析。本文第二项工作是利用实验室的半圆形激波管,初步研究了汇聚激波与正方形和正六边形Air-SF6界面相互作用的RMI问题,对波系的发展、界面位移和振幅随时间的变化特点进行了分析,并且与数值模拟进行对比,发现波系在中心汇聚前实验结果与数值结果吻合较好。
[Abstract]:When a shock wave passes through the interface of fluid with initial disturbance, the pressure gradient before and after the shock wave and the density gradient before and after the interface are not collinear, which will lead to baroclinic vorticity in the flow field, and the vorticity accumulates with time. This phenomenon is called Richtmyer-Meshkov instability (referred to as RMI).RMI in inertial confinement fusion). It has important application value in engineering problems such as scramjet, and also has important academic significance in flow instability, compressible flow, turbulence and so on. At present, much research is done on the RMI problem under the impact of weak shock waves. The interface shapes are mostly gas columns, spherical bubbles and single-mode interfaces. However, the intensity of shock waves may be larger in practical engineering applications, which will bring a stronger compression effect to the flow field. The shape of fluid interface is also complicated. This paper mainly focuses on the interaction between plane shock wave and square interface and the RMI problem of convergent shock wave interaction with square / hexagonal interface. In order to illustrate the effect of compressible effect, the first work of this paper is to study the interaction of plane shock wave with square Air-SF6 and Air-He interface by using VAS2D program. The evolution and development of wave system structure and interface under different compression effects are investigated, the axial and spanwise deformation of interface is quantitatively studied, the compressible effect of flow field under shock wave impact with different strength is analyzed, and the motion of upstream vortex pair is studied. The variation characteristics of vortex pair axial motion and vortex spacing under various working conditions are obtained, and the numerical annulus is studied and compared with the classical model, and the matching conditions are obtained. Error analysis is carried out. The second work in this paper is to study the RMI problem of convergent shock wave interacting with square and hexagonal Air-SF6 interface using semicircular shock tube in laboratory. The variation characteristics of the interface displacement and amplitude with time are analyzed and compared with the numerical simulation. It is found that the experimental results of the wave system before the central convergence are in good agreement with the numerical results.
【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O354.5

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