热传导效应影响下瑞利-泰勒不稳定性诱导湍流混合的直接数值模拟研究

RTI-induced turbulent mixing plays an important role in the field of high energy density such as ICF, weapon physics, and astrophysics. Under the condition of high energy density, knowledge of nonlinear effect and the turbulent mixing stage in the late stage of RTI evolution if far from enough. Basic problems such as the whether mixed transition can take place under the influence of strong thermal flow caused by electron heat conduction and radiation effect need to be solved. In recent years, experiments performed using the megajoule-level lasers have obtained some physical images at this stage, and direct numerical simulation studies are expected to provide more systematic and detailed information of this stage. Based on the framework of direct numerical simulation used for classical turbulence simulation, we take into electron and radiant heat conduction, the key effects making the high energy density problem distinct from others, into account. Direct numerical simulations of RTI-induced turbulent mixing processes under different heat transfer intensities will be performed. The aim of the study is to obtain an overall physical image of the RTI-induced turbulent mixing problem under the influence of thermal conduction effects, with the main focus on the quantitative relationship between the transition time and the final physical state of the RTI with thermal conduction intensity. Based on the understanding of the physical laws, modification on the existing turbulent mixing model will be proposed, which can correctly characterize the heat conduction effect and shall be applied to solve high energy density engineering problems.

瑞利-泰勒不稳定性（RTI）诱导的湍流混合是ICF、武器物理、天体物理等高能量密度领域中的重要问题。高能量密度条件下RTI演化后期的非线性作用和湍流混合阶段研究不足，在电子热传导和辐射效应导致的强能流影响下混合转捩能否发生等基础性问题亟待解决。近年来基于兆焦耳级激光器发展的实验平台获得了该阶段的一些物理图像，直接数值模拟研究有望提供更系统、精细的图像。本项目在经典流体直接数值模拟框架下，引入电子和辐射热传导效应这两项高能密度问题区别于经典问题的关键因素。对不同热传导强度下，RTI诱导湍流混合过程开展直接数值模拟研究。研究旨在获得热传导效应影响下RTI诱导湍流混合问题的总体物理图像，并重点关注混合转捩时间、RTI的演化最终状态的关键物理量与热传导强度间的定量关系。基于对该过程物理规律的认识，提出对现有湍流混合模型的改进方案，使其可以正确反映热传导效应对影响，并将其应用到高能量密度工程问题

瑞利-泰勒不稳定性（RTI）诱导的湍流问题是众多工程领域中的关键问题。特别地，对于激光惯性约束聚变（ICF）以及武器物理等高能量密度应用领域，湍流发生在极高温度的等离子中，当前的物理认识不足以支撑工程应用的需求。本项目基于数值模拟的方法考察了由电子或辐射引起的高温热传导对于RTI湍流的影响。重点关注了热传导效应对于RTI湍流转捩及后期演化规律的影响，研究并发展了可以正确考虑热传导效应的湍流模型。取得的主要进展包括：发展了可以考虑高温热传导效应的湍流模拟能力，在此基础上模拟获得了热传导影响下RTI湍流发展的序列化数据；研究认识到热传导引起的高强度能流影响下，流动仍能转捩到湍流状态；热传导对湍流发展的影响包括改变气泡、尖钉增长速度，抑制小尺度温度和密度脉动，促进涡量在尖钉一侧聚集，影响流动各向异性等；研究发现原K-L湍流模型无法正确反映热传导效应的影响，本项目提出了模型的改进方案。相关研究给出了高温热传导效应影响的规律性认识，发展了湍流模型的改进方案，对工程应用中正确模拟极端条件下的湍流问题提供了支撑。