发表机构
Indian Institute of Technology Dhanbad; Georgia Institute of Technology（印度技术学院丹巴德; 佐治亚理工学院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
通过直接数值模拟研究多层瑞利-泰勒不稳定性，揭示界面阿特伍德数对不稳定性增长、界面耦合及湍流混合的影响，发现强分层导致双混合层耦合合并及-11/5谱标度。
AI 中文摘要
对热分层多层瑞利-泰勒不稳定性进行了直接数值模拟，以研究界面阿特伍德数（At）对不稳定性增长、界面耦合、湍流混合和谱特性的影响。采用全可压缩、三维、高保真纳维-斯托克斯求解器，模拟了覆盖广泛界面At范围的十个案例，以考察耦合不稳定性动力学的演化。构型由三个叠加流体层组成，通过温度变化在两个界面上产生不稳定的密度分层。使用最大涡量、混合层增长、密度涨落、湍动能以及重力势能、湍动能和耗散之间的能量分配来表征流动的时间演化。所有构型的不稳定性演化均经历明显的起始、准指数增长和非线性饱和阶段。界面At的增加导致不稳定性更早起始、涡量放大增强以及湍流混合层发展加速。弱分层构型表现出类似于有效单界面瑞利-泰勒不稳定性（RTI）的动力学，而强分层案例则发展出两个同时活跃的混合层，随后相互作用并合并成一个耦合湍流区域。密度涨落和湍动能的壁面法向分布表明，随着分层强度的增加，混合区域逐渐拓宽，湍流活动重新分布加剧。后期谱在中间波数范围内表现出近似-11/5的标度律，与浮力主导的湍流输运一致。
英文摘要
Direct numerical simulations of thermally stratified multi-layer Rayleigh-Taylor instability are performed to investigate the influence of interfacial Atwood number (At) on instability growth, interfacial coupling, turbulent mixing, and spectral characteristics. A fully compressible, three-dimensional, high-fidelity Navier-Stokes solver has been used to simulate ten cases spanning a broad range of interfacial $At$ to examine the evolution of coupled instability dynamics. The configuration consists of three superposed fluid layers with unstable density stratification across two interfaces generated through temperature variations. The temporal evolution of the flow is characterized using the maximum vorticity, mixing-layer growth, density fluctuations, turbulent kinetic energy, and energy partitioning between gravitational potential energy, TKE, and dissipation. The instability evolution is shown to proceed through distinct onset, quasi-exponential growth, and nonlinear saturation stages for all configurations. Increasing interfacial At leads to earlier instability onset, enhanced vorticity amplification, and accelerated development of turbulent mixing layers. The weakly stratified configurations exhibit dynamics resembling effectively single-interface RTI, whereas the strongly stratified cases develop two simultaneously active mixing layers that subsequently interact and merge into a coupled turbulent region. The wall-normal distributions of density fluctuations and TKE demonstrate progressive broadening of the mixing region and increasing redistribution of turbulent activity with increasing stratification strength. The late-stage spectra exhibit an approximate -11/5 scaling over an intermediate range of wavenumbers, consistent with buoyancy-dominated turbulent transport.
