Asymptotic behaviour at the wall in compressible turbulent channels
Asymptotic behaviour at the wall in compressible turbulent channels
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DOI：
10.1017/jfm.2021.1087
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发表时间：
2021-12
影响因子：
3.7
通讯作者：
Akanksha Baranwal;D. Donzis;R. Bowersox
中科院分区：
文献类型：
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作者：
Akanksha Baranwal;D. Donzis;R. Bowersox
由于速度场的螺线管性质所施加的约束，在不可压缩流中，近壁雷诺应力的渐近行为是确定的。因此，对于可压缩流，人们可以期望一种不同的渐近行为，这在文献中确实已经指出。然而，从不可压缩到可压缩缩放的过渡，以及后者的限制行为，在很大程度上是未知的。因此，我们调查的近壁，湍流通量的渐近行为的压缩性的影响，使用一个大的直接数值模拟（DNS）数据库的湍流通道流在高于通常的壁正常的分辨率。我们改变马赫数在一个恒定的摩擦雷诺数直接评估压缩性的影响。我们观察到，即使考虑平均密度变化并使用半局部标度，可压缩湍流的近壁渐进行为也与相应的不可压缩流不同。对于马赫数接近不可压缩区域，近壁渐近行为遵循众所周知的理论行为。当马赫数增加时，由于膨胀效应的增加，包含壁面法向分量的湍流通量的斜率减小。我们观察到，R_{vv}$在比其它通量所需的马赫数更低的马赫数下接近其高马赫数渐近线。我们还介绍了一个过渡距离的壁湍流通量表现出的变化标度指数。墙模型的影响进行了简要介绍。
Abstract The asymptotic behaviour of Reynolds stresses close to walls is well established in incompressible flows owing to the constraint imposed by the solenoidal nature of the velocity field. For compressible flows, thus, one may expect a different asymptotic behaviour, which has indeed been noted in the literature. However, the transition from incompressible to compressible scaling, as well as the limiting behaviour for the latter, is largely unknown. Thus, we investigate the effects of compressibility on the near-wall, asymptotic behaviour of turbulent fluxes using a large direct numerical simulation (DNS) database of turbulent channel flow at higher than usual wall-normal resolutions. We vary the Mach number at a constant friction Reynolds number to directly assess compressibility effects. We observe that the near-wall asymptotic behaviour for compressible turbulent flow is different from the corresponding incompressible flow even if the mean density variations are taken into account and semi-local scalings are used. For Mach numbers near the incompressible regimes, the near-wall asymptotic behaviour follows the well-known theoretical behaviour. When the Mach number is increased, turbulent fluxes containing wall-normal components show a decrease in the slope owing to increased dilatation effects. We observe that $R_{vv}$ approaches its high-Mach-number asymptote at a lower Mach number than that required for the other fluxes. We also introduce a transition distance from the wall at which turbulent fluxes exhibit a change in scaling exponents. Implications for wall models are briefly presented.