高温化学非平衡湍流边界层脉动量象限分析

Quadrant decomposition analysis of fluctuations in high-temperature turbulent boundary layer with chemical non-equilibrium

高超声速飞行器在较低空域以极高马赫数飞行时,表面会同时存在湍流与化学非平衡流动,但目前针对此类高温化学非平衡湍流边界层流动特性的研究工作还比较有限,对不同湍流特征的主导流动机制的认识还有待于进一步深入。选取高超声速楔形体头部斜激波后的流动状态,设置3种不同的壁面温度,通过直接数值模拟对比了不同壁温条件下的边界层参数分布特性,并采用象限分解技术分析了边界层不同象限流动事件对雷诺剪切应力、湍流热流、湍流质量扩散的贡献。结果显示:在整个边界层中上抛和下扫运动对雷诺剪切应力的贡献占优;冷壁效应会使得流向和法向湍流热流通量的主导流动事件在温度峰值两侧发生改变。O原子组分流向湍流组分扩散主要受到高质量分数流体慢速运动事件和低质量分数流体快速运动事件的影响,而法向湍流组分扩散则主要受到高质量分数流体向上运动事件和低质量分数流体向下运动事件的影响。

The surface of hypersonic vehicles will concurrently experience turbulence and chemical non-equilibrium flow during flight at a high Mach number and a low altitude.However,current research on the flow characteristics of such high-temperature turbulent boundary layers with chemical non-equilibrium is still limited,and understanding of the dominant flow mechanism of turbulence characteristics needs to be further deepened.Choosing the flow state after the leading shock of a cone,this study sets three different wall temperature to compare the distribution characteristics of boundary layer parameters through direct numerical simulation,and analyzes the contributions of different events to Reynolds shear stress,turbulent heat-flux,and turbulent mass diffusion using quadrant analysis.The results show that the contribution of ejections and sweeps to Reynolds shear stress is dominant in the entire boundary layer.The cold wall condition will cause change in the dominant events of both the streamwise and normalwise turbulent heat-flux on both sides of the temperature peak.The streamwise turbulent mass diffusion of O atom components is mainly affected by slow moving high-mass fraction motion and fast moving low-mass fraction motion,while that of the normalwise turbulent mass is dominated by upward moving high-mass fraction motion and inward moving low-mass fraction motion.