斜压效应对Rayleigh-Taylor不稳定性湍流混合影响的实验研究

Turbulent mixing induced by Rayleigh-Taylor instability (RTI) has attracted considerable interest because of its importance both in nature and engineering application, and is the present research front and hotspot. Current research is mainly focused on the turbulent mixing induced by RTI occurred on the horizontal/vertical interfaces. However, interfaces are more complex in practical situations, and the direction of density gradient is not always in alignment with the direction of pressure gradient. Therefore, it is worthwhile to discuss the influence of baroclinic effect associated with misalignment of density and pressure gradients, as well as the coupling of RTI and Kelvin-Helmholtz instability (KHI) on the turbulent mixing. The present project is going to develop simultaneous velocity-concentration diagnostic technique in order to investigate liquid-liquid inclined interface. This technique is based on particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF). Such technique would achieve simultaneous measurements of both velocity and concentration fields quantitatively for statistical analysis. Furthermore, vortex identification will be employed to identify vortices from velocity fields. And the mechanism of turbulent mixing is investigated by analyzing the evolution of the vortices combined with turbulent statistics (including both the density and velocity statistics).By changing the initial inclination angle and the acceleration history, the underlying mechanism of both the baroclinic effect and the RTI-KHI coupling effect on interfacial evolution and turbulent mixing will be explored. These investigations provide useful understanding for active control of turbulent mixing in practical engineering applications.

Rayleigh-Taylor (R-T)不稳定性诱导的湍流混合在自然界和工程应用中均具有重要作用，是目前学术界研究的前沿和热点。现有研究工作主要集中在水平或垂直界面上的R-T不稳定性湍流混合，但实际工程应用中界面更为复杂，密度梯度和压力梯度的方向通常是不共线的，与此相关的斜压效应及R-T不稳定性和Kelvin-Helmholtz (K-H)不稳定性的耦合对湍流混合的影响是值得研究的课题。本申请以液-液斜界面作为研究对象，拟建立适用于液-液界面的粒子图像测速(PIV)和平面激光诱导荧光(PLIF)同步测试技术，同步定量表征流动的速度场和密度场并进行统计分析，利用旋涡辨识技术辨识流场中的拟序结构，分析湍流混合区的演化特征和规律。通过改变斜界面初始倾角、加载强度等参数，探讨斜压效应及R-T不稳定性和K-H不稳定性的耦合对湍流混合的影响规律，为工程应用中不稳定性湍流混合的主动控制提供参考。

Rayleigh-Taylor (R-T)不稳定性诱导的湍流混合在自然界和工程应用中均具有重要作用，是目前学术界研究的前沿和热点。现有研究工作主要集中在水平或垂直界面上的R-T不稳定性湍流混合，但实际工程应用中界面更为复杂，密度梯度和压力梯度的方向通常是不共线的，与此相关的斜压效应及R-T不稳定性和Kelvin-Helmholtz (K-H)不稳定性的耦合对湍流混合的影响是值得研究的课题。本项目设计并建立了倾斜角度连续可调的液-液界面R-T不稳定性实验装置，建立了适用于液-液界面的粒子图像测速（PIV）和平面激光诱导荧光（PLIF）同步测试技术，开展了不同倾斜角度和加载强度下的液-液斜界面R-T失稳及湍流混合实验研究，获得了丰富的实验数据。利用湍流统计理论对获得的速度场-浓度场同步测量数据进行了分析和解读，定量揭示了斜压效应对界面失稳诱导湍流混合的影响规律，同时讨论了在该过程中R-T不稳定性与K-H不稳定性的耦合效应。本项目研究工作为工程应用中不稳定性诱导湍流混合的主动控制提供了有益参考。