Direct numerical simulation of hypersonic turbulent boundary layers: effect of spatial evolution and Reynolds number
Direct numerical simulation of hypersonic turbulent boundary layers: effect of spatial evolution and Reynolds number
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DOI：
10.1017/jfm.2022.80
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发表时间：
2022-02
影响因子：
3.7
通讯作者：
Junji Huang;L. Duan;Meelan Choudhari
中科院分区：
文献类型：
--
作者：
Junji Huang;L. Duan;Meelan Choudhari
采用直接数值模拟方法，研究了平板零压梯度湍流边界层在3种不同的马赫数($2.5$、$4.9$和$10.9$)、表面温度从绝热到高度冷却条件下的空间演化。无论是基于von Kármán积分方程式的满足程度，还是通过比较不同的入流湍流产生技术，都仔细监测了湍流统计数据进入充分发展的湍流边界层平衡状态的过程。所建立的数值模拟数据库用于描述高马赫数冷壁区域中多个重要变量的流向演化，包括壁面阻力、雷诺相似系数、形状因子、雷诺应力和壁量波动。这些数据证实了许多经典和较新的可压缩性变换在中等高雷诺数(最高可达摩擦雷诺数$Re_\tau\约1200$)下的有效性，并表明，在适当的尺度下，近壁条纹和超结构的尺寸对马赫数和壁面冷却条件不敏感。在高超声速冷壁情况下，强壁面冷却导致近壁涡的尺寸(相对于边界层厚度)显著增大，从而导致大小尺度的湍流尺度之间的分离减小，从而导致对数区域的流向速度展宽谱上没有外峰。
Abstract Direct numerical simulations (DNS) are performed to investigate the spatial evolution of flat-plate zero-pressure-gradient turbulent boundary layers over long streamwise domains (${>}300\delta _i$, with $\delta _i$ the inflow boundary-layer thickness) at three different Mach numbers, $2.5$, $4.9$ and $10.9$, with the surface temperatures ranging from quasiadiabatic to highly cooled conditions. The settlement of turbulence statistics into a fully developed equilibrium state of the turbulent boundary layer has been carefully monitored, either based on the satisfaction of the von Kármán integral equation or by comparing runs with different inflow turbulence generation techniques. The generated DNS database is used to characterize the streamwise evolution of multiple important variables in the high-Mach-number, cold-wall regime, including the skin friction, the Reynolds analogy factor, the shape factor, the Reynolds stresses, and the fluctuating wall quantities. The data confirm the validity of many classic and newer compressibility transformations at moderately high Reynolds numbers (up to friction Reynolds number $Re_\tau \approx 1200$) and show that, with proper scaling, the sizes of the near-wall streaks and superstructures are insensitive to the Mach number and wall cooling conditions. The strong wall cooling in the hypersonic cold-wall case is found to cause a significant increase in the size of the near-wall turbulence eddies (relative to the boundary-layer thickness), which leads to a reduced-scale separation between the large and small turbulence scales, and in turn to a lack of an outer peak in the spanwise spectra of the streamwise velocity in the logarithmic region.