钝头双锥喷流致冷流场结构及密度脉动特性

采用大涡模拟方法对钝头双锥喷流致冷流场开展了数值模拟,研究了超声速喷流混合流场结构特征及密度脉动特性。大涡模拟方法基于隐式亚格子模型,空间离散采用高精度通量限制型紧致格式,时间推进采用显式Runger-Kutta方法。数值模拟清晰地捕捉到了流场波系结构,精细地预测了流动发生失稳、转捩以及发展为充分发展湍流的物理过程,直接获得了流场密度脉动特性。通过有、无喷流状态对称面流场的对比,发现超声速喷流能够有效冷却光学窗口;喷流与主流形成的混合层不稳定,很快发生失稳和转捩,形成大尺度湍流结构,进而引起强烈的密度脉动。此外,获得了钝头双锥整体模型喷流致冷流场的空间发展形态特征。 

Flow field structures and density fluctuation characteristics around a blunted double cone with cooling jet

Large eddy simulation was utilized for the simulation of supersonic cooling jet flow filed around a blunted double cone, and the flow structures and density fluctuation characteristics were analyzed. The large eddy simulation method was based on the implicit sub-grid model, and the high-order flux limited compact scheme and explicit Runger-Kutta method were utilized for the spatial discretization and time advancing. The present simulation clearly captured the flow field discontinuity. The processes of flow becoming unstable and transiting to turbulence were predicted subtly. Besides, the characteristics of the flow field density fluctuation were obtained directly. By comparison with the none-jet state, it revealed that gas film formed by the supersonic jet can effectively cool the optical window, and the mixing layer formed by the main flow and jet flow became unstable, and transited to turbulence quickly, causing large scale turbulence structures and intense density fluctuation. In addition, the spatial development characteristics of cooling jet flow field around the whole model are obtained.