Temporal-Spatial Evolution of Kinetic and Thermal Energy Dissipation Rates in a Three-Dimensional Turbulent Rayleigh-Taylor Mixing Zone.
Temporal-Spatial Evolution of Kinetic and Thermal Energy Dissipation Rates in a Three-Dimensional Turbulent Rayleigh-Taylor Mixing Zone.
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三维湍流瑞利泰勒混合区动能和热能耗散率的时空演化
DOI：
10.3390/e22060652
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发表时间：
2020-06-12
期刊：
影响因子：
--
通讯作者：
Zhang Y
中科院分区：
文献类型：
--
作者：
Guo W;Guo X;Wei Y;Zhang Y
本文采用晶格玻尔兹曼方法对三维（3D）湍流瑞利-泰勒（RT）混合过程中动能耗散率和热能耗散率的时空演化进行了数值研究。详细分析了三维湍流瑞利-泰勒混合区的温度场、动能耗散率和热能耗散率随时空演化的变化规律、概率密度函数、混合界面分形维数、动能耗散率和热能耗散率的结构函数空间标度规律，从而提高了对三维湍流瑞利-泰勒混合区的时空耗散率特征的物理认识。数值结果表明，随着时间的推移，动能耗散率和热能耗散率分别集中在速度和温度梯度较大的区域，这与理论假设一致。随着时间的推移，在半垂直高度段开始的小尺度热羽逐渐发展为大尺度热羽。随着时间的演化，热耗散的概率密度函数尾部逐渐上升，逼近拉伸指数函数。分形维数的斜率在早期增大，但在t/τ≥2时，流体界面的分形维数为2.4，表明湍流RT混合区在三维空间中具有自相似性。进一步证明了速度和温度结构函数的二阶、四阶和六阶结构函数在惯性范围内具有线性标度。
In this work, the temporal–spatial evolution of kinetic and thermal energy dissipation rates in three-dimensional (3D) turbulent Rayleigh–Taylor (RT) mixing are investigated numerically by the lattice Boltzmann method. The temperature fields, kinetic and thermal energy dissipation rates with temporal–spatial evolution, the probability density functions, the fractal dimension of mixing interface, spatial scaling law of structure function for the kinetic and the thermal energy dissipation rates in 3D space are analysed in detail to provide an improved physical understanding of the temporal–spatial dissipation-rate characteristic in the 3D turbulent Rayleigh–Taylor mixing zone. Our numerical results indicate that the kinetic and thermal energy dissipation rates are concentrated in areas with large gradients of velocity and temperature with temporal evolution, respectively, which is consistent with the theoretical assumption. However, small scale thermal plumes initially at the section of half vertical height increasingly develop large scale plumes with time evolution. The probability density function tail of thermal energy dissipation gradually rises and approaches the stretched exponent function with temporal evolution. The slope of fractal dimension increases at an early time, however, the fractal dimension for the fluid interfaces is 2.4 at times t/τ ≥ 2, which demonstrates the self-similarity of the turbulent RT mixing zone in 3D space. It is further demonstrated that the second, fourth and sixth-order structure functions for velocity and temperature structure functions have a linear scaling within the inertial range.
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