在BARC试验情况下角锐度的重要性：数值研究
The importance of corner sharpness in the BARC test case: a numerical study
摘要：
在较低的湍流雷诺数下，通过直接数值模拟研究了BARC流动，重点是前缘（LE）拐角的几何表示。这项研究有助于进一步了解现有的数值和实验BARC数据之间的差异。在第一部分中，考虑具有小曲率半径的圆形LE拐角。结果表明，少量的圆化并不会导致平均场的突变，但这种影响随着曲率半径的增大而增大。剪切层以较低的角度从圆形LE分离，这减小了气缸侧上方的主要再循环区域的尺寸。相反，后缘（TE）后面的回流区的纵向尺寸增加，作为TE剪切层加速。讨论了曲率半径对湍流动能及其产生、耗散和输运的影响。当前结果应与Rocchio等人（JWEIA 2020）的近期工作进行对比，Rocchio等人通过隐式大涡模拟发现，在雷诺数大于甚至小曲率半径的情况下，平均流会发生显著变化。在第二部分中，LE角是完全尖锐的，并且在角的邻域中的Stokes问题的精确解析解用于局部恢复由奇异性降低的解精度。平均流量的变化表明，分析修正会导致更好地遵循拐角的流线。流动以较小的角度从LE分离，导致略微较小的再循环区域。角校正方法是有价值的，一般来说，并预计将有助于开发高品质的数值模拟在高雷诺数的典型实验与合理的网格要求。
英文摘要：
The BARC flow is studied via Direct Numerical Simulation at a relatively low turbulent Reynolds number, with focus on the geometrical representation of the leading-edge (LE) corners. The study contributes to further our understanding of the discrepancies between existing numerical and experimental BARC data. In a first part, rounded LE corners with small curvature radii are considered. Results show that a small amount of rounding does not lead to abrupt changes of the mean fields, but that the effects increase with the curvature radius. The shear layer separates from the rounded LE at a lower angle, which reduces the size of the main recirculating region over the cylinder side. In contrast, the longitudinal size of the recirculating region behind the trailing edge (TE) increases, as the TE shear layer is accelerated. The effect of the curvature radii on the turbulent kinetic energy and on its production, dissipation and transport are addressed. The present results should be contrasted with the recent work of Rocchio et al, JWEIA 2020, who found via implicit Large-Eddy Simulations at larger Reynolds numbers than even a small curvature radius leads to significant changes of the mean flow. In a second part, the LE corners are fully sharp and the exact analytical solution of the Stokes problem in the neighborhood of the corner is used to locally restore the solution accuracy degraded by the singularity. Changes in the mean flow reveal that the analytical correction leads to streamlines that better follow the corners. The flow separates from the LE with a lower angle, resulting in a slightly smaller recirculating region. The corner-correction approach is valuable in general, and is expected to help developing high-quality numerical simulations at the high Reynolds numbers typical of the experiments with reasonable meshing requirements.
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