Abstract

This study aims to isolate and evaluate the influence of a corrugation on flow structures and aerodynamics under compressible low Reynolds number conditions, and to compare it to simpler but well-known model: the flat plate. The simplified corrugated model was made by a flat surface with only two corrugations on the leading edge. The models only differ for the corrugations on the leading edge. Force values were measured at a Reynolds number ranging from 10,000 to 25,000 and at a Mach number from 0.2 to 0.6. Pressure sensitive paint was used at the same flow conditions and the pressure distribution over the models was obtained. Schlieren visualization was also conducted and flow characteristics were observed. Detailed analysis showed that the corrugated model experiences strong depression on the leading edge caused by the separation of the boundary layer. Because of the presence of the corrugation, the shear layer transitions to turbulent rapidly and reattaches to the surface before reaching the summit of the first corrugation, separating again at its peak. Instabilities in the shear layer were dissipated thanks to the shape of the corrugation allowing pressure recovery and discouraging flow separation. The flow reattaches before reaching the trailing edge. The results showed that the transition of the boundary layer was accelerated as the Reynolds number increases on corrugated model, leading to a stronger negative pressure zone in the leading edge. Due to pressure recovery being less effective, lead to similar performances for the range of studied Reynolds numbers. The compressibility effects resulted in a delay on the transition of the instability of the shear layer, negatively affecting the intensity of the pressure gradients as well as pressure recovery. This contributed to the variation in the performance of the wing. As a result, the corrugated model has a better aerodynamic performance compared to the flat plate at low Reynolds numbers, but not for higher Mach numbers.

Graphic abstract

中文翻译：

---

可压缩性和雷诺数对简化波纹形翼型空气动力学的影响

摘要

这项研究旨在分离和评估波纹在可压缩的低雷诺数条件下对流动结构和空气动力学的影响，并将其与更简单但众所周知的模型：平板进行比较。简化的瓦楞纸模型是由一个在前边缘只有两个瓦楞纸的平坦表面制成的。型号仅针对前缘的波纹有所不同。在10,000至25,000的雷诺数和0.2至0.6的马赫数下测得力值。在相同的流量条件下使用压敏涂料，并获得了模型上的压力分布。还进行了Schlieren可视化，并观察了流动特性。详细分析表明，由于边界层的分离，瓦楞纸模型在前缘处经历了强烈的凹陷。由于存在波纹，剪切层会迅速转变为湍流，并在到达第一个波纹的顶点之前重新附着到表面，并在其峰值处再次分离。由于波纹的形状，可以消除剪切层中的不稳定性，从而可以恢复压力并阻止流动分离。流量在到达后缘之前重新附着。结果表明，在瓦楞纸模型中，随着雷诺数的增加，边界层的过渡加速，导致前缘的负压区更强。由于压力恢复效果较差，在所研究的雷诺数范围内导致相似的性能。可压缩性效应导致剪切层不稳定性转变的延迟，对压力梯度的强度以及压力恢复产生负面影响。这导致机翼性能的变化。结果，相比于低雷诺数的平板，波纹模型具有更好的空气动力学性能，但对于较高的马赫数则没有。

图形摘要