本文選題：擴散型界面 + R-M不穩(wěn)定性　； 參考：《力學學報》2016年05期

【摘要】：Richtmyer-Meshkov(R-M)不穩(wěn)定性普遍存在于眾多工程問題中,激波管實驗是研究R-M失穩(wěn)問題的主要手段.高精度的平面激光誘導熒光(planar laser-induced fluorescence,PLIF)技術具有分子量級的示蹤能力,可獲得界面氣體濃度(摩爾分數)分布,為研究界面失穩(wěn)混合問題提供了有力工具.在弱激波(Ma=1.25)沖擊擴散型氣柱界面實驗中,采用PLIF技術對R-M失穩(wěn)引起的SF6-Air界面混合問題進行了研究.通過改變橢圓形初始界面的長短軸比,得到了3種擴散型初始界面失穩(wěn)演化過程中氣體摩爾分數,觀察到了斜壓機制下界面的簡單拉伸、二次不穩(wěn)定性、擠壓射流等現象.利用濃度分布進一步得到了界面的瞬時混合率,通過瞬時混合率、界面整體平均混合率以及混合率的概率密度分布,分析了界面在不同演化階段的界面混合特征,初步討論了界面失穩(wěn)混合的機制.演化初期,界面在斜壓渦的作用下發(fā)生拉伸卷曲,通過增大濃度梯度來促進界面的混合.當演化進一步發(fā)展,二次不穩(wěn)定性出現后,界面通過小尺度對流的方式達到湍流混合狀態(tài),而濃度梯度驅使的分子間混合逐漸減弱.由濃度梯度引起的擴散與由二次不穩(wěn)定性引起的對流存在著"競爭"關系,二者共同主導了界面的混合.
[Abstract]:Richtmyer-Meshkov-R-M) instability exists in many engineering problems, and shock tube experiment is the main method to study R-M instability. The planar laser-induced fluorescence technique has molecular tracer ability and can obtain the interfacial gas concentration (molar fraction) distribution, which provides a powerful tool for the study of the interfacial instability mixing problem. In the experiment of impact-diffusion gas column interface, the mixing problem of SF6-Air interface caused by R-M instability was studied by PLIF technique. By changing the long-axis ratio of the elliptical initial interface, the molar fraction of gas in the evolution process of three diffusion-type initial interfaces is obtained. The phenomena of simple tension, secondary instability and extrusion jet are observed under baroclinic mechanism. The instantaneous mixing rate of the interface is obtained by using the concentration distribution. Through the instantaneous mixing rate, the overall average mixing rate of the interface and the probability density distribution of the mixing rate, the interfacial mixing characteristics at different evolution stages are analyzed. The mechanism of interfacial instability mixing is discussed. In the early stage of evolution, the interface was stretched and curled under the action of baroclinic vortices, and the mixing of the interface was promoted by increasing the concentration gradient. With the further development of evolution and the emergence of secondary instability, the interfacial turbulent mixing state is achieved by small scale convection, while the intermolecular mixing driven by concentration gradient weakens gradually. There is a "competitive" relationship between the diffusion caused by the concentration gradient and the convection caused by the secondary instability, both of which dominate the interfacial mixing.
【作者單位】： 中國工程物理研究院流體物理研究所沖擊波物理與爆轟物理國防科技重點實驗室;
【基金】：國家自然科學基金資助項目(11172278,11302201,11472253)
【分類號】：O354.5

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