液体薄层Rayleigh-Taylor失稳混合中表面张力影响效应的实验研究

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 single interface formed with two semi-infinite layers. However, interfaces are more complex in practical situations, the thin fluid layer made up of two interfaces with every short distance is familiar such as the capsule in inertial-confinement-fusion (ICF) which has multilayer structure. The thin liquid layer breaks up during the instability evolution where interface intension is an important parameter and probably effects the turbulent mixing in late stage. Therefore, it is worthwhile to discuss the influence of interface intension effect associated with RTI in thin liquid layer, as well as the mechanism of turbulent mixing after breaking up. The present project is going to experimentally investigate RTI in thin liquid layer with high-speed shadow photograph, aiming to study the revolution of RTI in thin liquid layer. Based on the simultaneous velocity-concentration diagnostic technique adapted to double interfaces, the mechanism of turbulent mixing after breaking up is investigated by analyzing the evolution of the vortices combined with turbulent statistics (including both the density and velocity statistics). By changing the interface intension, of which, the underlying mechanism on thin layer instability and turbulent mixing will be explored. These investigations are expected to provide useful understanding for active control of turbulent mixing induced by RTI 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两侧为半无限厚度流体的单层界面的R-T不稳定性，但实际工程应用中界面更为复杂，往往存在着由相距较近的双层界面所构成的流体薄层，如惯性约束聚变（ICF）中具有多层结构的靶球。液体薄层在失稳演化中会出现破碎，薄层的界面张力是该过程中的一个重要参数，并可能对之后的湍流混合产生影响作用。因此流体薄层表面张力对R-T不稳定性及其湍流混合特性的影响规律是值得研究的课题。本申请以液体薄层作为研究对象，研究液体薄层的R-T失稳演化规律；拟建立适用于双层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，同时定量表征薄层流动的速度场和密度场并进行统计分析，分析薄层表面张力对薄层湍流混合区演化的影响机制，为实际工程应用中R-T不稳定性湍流混合的主动控制提供有益参考。

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。现有研究工作主要集中在两侧为半无限厚度流体的单层界面的R-T不稳定性，但实际工程应用中界面更为复杂，往往存在着由相距较近的双层界面所构成的流体薄层，如惯性约束聚变（ICF）中具有多层结构的靶球。为了认识表面张力对薄层界面的失稳演化特性的影响机制，特别是薄层破碎后湍流混合阶段的发展规律，项目组开展了以下研究内容：设计并建立了倾斜角度连续可调的液体薄层界面失稳可控加载实验装置，并优化了了PIV-PLIF联合测试技术；开展了多种状态下液-液斜界面R-T失稳演化及湍流混合实验研究，实验对象包括了单层界面、多种表面张力组合界面、不同液体薄层宽度下的双层界面等，获得了丰富的实验数据。进一步地，利用湍流统计分析技术对获得的速度场-浓度场同步测量数据进行了分析和解读。通过实验研究，认识了界面流体表面张力、液体薄层厚度等因素对液体薄层失稳过程及后期湍流混合的影响。上述工作为深入认识界面不稳定性湍流混合的内在物理机制打下了坚实基础。