RM不稳定性诱发湍流混合数值模拟和确认

RM instability is an important physical-mechanical problem in the primary implosion process of nuclear weapon, which has significant influence on the performance of nuclear weapon, and as well as in other fields such as the inertial confinement fusion (ICF), astrophysics and high-speed combustion, therefore it is also a much more fundamental one. In order to study the whole development process of RM instability, especially the interface evolution, fragmentation of bubble and spike, and its induced turbulent mixing in the late times, the high precision large-eddy simulation method and corresponding three dimensional parallel program based on the compressible multiple viscous fluids and turbulence Navier-Stokes equations are to be developed. At the same time, some benchmark membraneless experiment (such as gas cylinder or curtain)and membrane experiment need to be conducted on shock tube. The technique of particle-image velocimetry (PIV) is appiled to measure the velocity field, the technique of planar laser-induced fluorescence (PLIF) combined with high-speed photography is applied to capture the fine interface structures in flow field. The quantitative and qualitative experimental results are used to validate the effectiveness and reliability of numerical method and program. Then the evolution character and intrinsic physical law of turbulent mixing zone are to be investigated numerically to advance the development of some corresponding disciplines.

RM不稳定性是核武器初级内爆过程中的一个重要物理力学问题，对核武器性能有重大影响，同时在其它领域如惯性约束聚变（ICF）、天体物理学、超音速燃烧等领域也有重要作用，所以RM不稳定性是一个基础性很强的问题。本项目主要针对RM不稳定性发展全过程，特别是后期的界面演化、气泡和尖钉的破碎及诱发的湍流混合，开展基于可压缩多介质粘性流动和湍流Navier-Stokes方程组的高精度大涡数值模拟方法研究，并研制相应的三维并行计算程序。同时在激波管装置上开展无膜（气柱或气帘）和有膜的RM不稳定性实验，并利用粒子图像测速（PIV）技术定量地测量二维速度场，利用平面激光诱发荧光（PLIF）技术结合高速摄影技术测量界面发展过程中流场的精细结构，获取定量的实验数据对数值模拟方法和计算程序的有效性和可靠性进行确认。通过数值模拟，研究分析湍流混合区的特征演化、内在的物理规律，促进相关领域内学科的发展。

利用分裂技术、分段抛物插值、流体体积分数方法、并行计算技术等，发展了适用于可压缩多介质粘性流动和湍流的三维大涡模拟方法和程序MVFT，并通过实验确认了程序的可靠性和有效性。然后利用该程序数值模拟研究了多次冲击作用下RM不稳定性及湍流混合长时间演化的动力学行为及对初始条件的依赖性。（1）湍流混合区宽度在不同的冲击阶段具有不同的增长规律，而湍流混合区统计量以相似的规律衰减，即湍流混合区的发展具有统计相似性；（2）湍流混合区的发展在前期具有强的各向异性，但是随着混合湍流逐渐进入完全湍流状态，其也逐渐趋于各向同性；（3）湍流混合区的发展对初始条件有很强的依赖性，但这主要体现在初始冲击后-反射冲击前和反射冲击后-反射稀疏波作用这两个阶段，第一次反射稀疏波作用后，湍流混合区的发展基本不受初始条件的影响。