本文選題：Richymyer-Meshkov不穩(wěn)定性　切入點：正方形界面　出處：《中國科學技術大學》2017年碩士論文　論文類型：學位論文

【摘要】：當一道激波穿過具有初始擾動的流體界面時,激波前后的壓力梯度和界面前后的密度梯度不共線會導致流場中產(chǎn)生斜壓渦量,渦量隨時間不斷積累,并促使界面上的擾動不斷增長,界面逐漸失穩(wěn),最終發(fā)展為湍流混合,這種現(xiàn)象被稱為Richtmyer-Meshkov不穩(wěn)定性(簡稱RMI)。RMI在慣性約束核聚變、超燃沖壓發(fā)動機等工程問題中有重要的應用價值,在流動不穩(wěn)定性、可壓縮流動、湍流等問題中也有重要的學術意義。自提出以來,RMI就引起了諸多關注,目前研究較多的是弱激波沖擊下的RMI問題,界面形狀多為氣柱、球形氣泡和單模界面,而實際工程應用中的激波強度可能較大,會給流場帶來更強的壓縮效應,而流體界面形狀也較為復雜。本文主要圍繞不同強度的平面激波與正方形界面相互作用以及匯聚激波與正方形/正六邊形界面相互作用的RMI問題展開相關工作,以說明可壓縮效應的影響。本文第一項工作是運用實驗室已有的VAS2D程序?qū)ζ矫婕げㄅc正方形Air-SF6 和 Air-He界面的相互作用進行了數(shù)值研究,探究了不同壓縮效應下的波系結構和界面的演化發(fā)展,定量研究了界面軸向和展向的變形情況,對不同強度激波沖擊下流場的可壓縮效應進行了分析;研究了上游渦對的運動,得出各工況下渦對軸向運動和渦間距的變化特點;對數(shù)值環(huán)量進行了研究,與經(jīng)典模型進行對比,得出了匹配條件,進行了誤差分析。本文第二項工作是利用實驗室的半圓形激波管,初步研究了匯聚激波與正方形和正六邊形Air-SF6界面相互作用的RMI問題,對波系的發(fā)展、界面位移和振幅隨時間的變化特點進行了分析,并且與數(shù)值模擬進行對比,發(fā)現(xiàn)波系在中心匯聚前實驗結果與數(shù)值結果吻合較好。
[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.
【學位授予單位】：中國科學技術大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：O354.5

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