Mach8的平板可压缩湍流边界层直接数值模拟及分析

对来流马赫数等于8,壁温等于10.03倍来流参考温度的平板可压缩湍流边界层做了直接数值模拟,计算涵盖了从层流到转捩以及最终充分发展湍流的全空间演化过程.对湍流的统计特征做了详细的分析,结果表明,在当前的计算工况下,湍流边界层核心区平均速度剖面仍然满足对数率,且卡门常数基本不变;可压缩效应明显增强,由于采用近似恢复温度的等温壁条件,使得近壁区温度较高,导致当地声速增大,使得湍流马赫数绝对值较低,造成内在压缩性效应不强,与经典强雷诺比拟相比,除在数量上产生一些偏差外,强雷诺比拟关系近似成立,且Morkovin假设依然有效;对扩展自相似性和标度率分析表明,对于平板可压缩湍流边界层而言,高马赫数流动使得其适用范围减小;压缩性效应对近壁湍动能,条带结构,涡等值面分布的影响得到分析.

DNS and analysis of a spatially evolving hypersonic turbulent boundary layer over a flat plate at Mach 8

Direct numerical simulation is investigated for hypersonic flat plate with Ma~=8 and Tw/T∞=10.03. Present computation covers the procedure from laminar flow to final full developed turbulent flow. A deliberate analysis of turbulent statistics characteristics has been presented in this paper. The results show that, with present computational conditions, mean velocity profile in core region of turbulence satisfies logarithm law, and Karman constant is kept here. Because of the wall temperature is high, so the local sound speed increases and turbulent Mach number decrease, as the results that intrinsic compressible effects is not strong. The strong Reynolds analogy is still validity with small deviation of value compare to traditional results. And Morkovin＇s hypothesis is still true in present study. Extended self-similarity is also tested and verified, The shrinking of the ESS range of scales is captured by comparing to low Mach number flow. Finally, near-wall streaks and iso-vorticity are also tested and analyzed.