超声速喷流混合流场大涡模拟

以光学窗口外冷喷流为研究背景，采用大涡模拟方法对后台阶外形切向喷流混合流场进行了研究。数值方法基于隐式亚格子模型，采用高精度WENO格式进行空间离散，并通过超声速平面混合层流动对数值方法进行了考核验证。喷流混合流场计算模型与试验一致，来流和喷流马赫数分别为3.4和2.5。数值模拟清晰地捕捉到了流场波系以及混合剪切层、壁面边界层等典型流场结构，并精细预测了混合层发生失稳、转捩及发展为充分发展湍流的时空发展过程。数值模拟得到的湍流大尺度结构的位置和形态与实验图像一致。通过对瞬时流场、统计平均流场和脉动参数的分析，揭示了流场结构特征及其时空演化规律，并获得了流场密度脉动特性。 

Large eddy simulation of supersonic jet mixing flow

On the background of cooling jet flow on the optical window, the supersonic jet flow over a backward facing step was investigated via large-eddy simulation (LES). Based on the implicit sub-grid model, the numerical method utilized the seventh order WENO scheme for spatial discretion, which was validated by the simulation of the supersonic mixing layer. The computational model for supersonic jet mixing flow was identical to the wind tunnel experiment, and the Mach number of the free flow and jet flow were set as 3.4 and 2.5, respectively. The numerical simulation captured the complex flow structures of compressive and expansive waves, as well as the shearing mixing layer and boundary layers. The process of flow becoming unsteady and transiting to turbulence was predicted subtly. The position and shape of large-scale turbulent structures obtained from numerical simulation agreed with experimental images. By the analysis of instantaneous, averaged, and fluctuant flow field, the temporal and spatial evolution of flow structures were revealed, and the feature of density fluctuation was acquainted.