This article reports an investigation into dynamic characteristics of the laminar separation bubbles (LSBs) associated with aerodynamic loads unsteadiness of a cambered thin airfoil in pitching-up motions at low Reynolds number flows. Unsteady Reynolds-averaged Navier–Stokes (URANS) simulations were conducted for a 4%c cambered thin airfoil at Reynolds number of 30,000 and 60,000. The airfoil pitches up from 0° to 25°angles of attack at dimensionless pitch rate $\dot{\alpha }$ of 0.0398 and 0.0199. The $\mathit{k}-\mathit{\omega }$ SST $\gamma -\tilde{R}{e}_{\mathit{\theta t}}$ turbulence transition model was used to account for the effect of transition on LSBs’ development. The LSBs are shown to evolve in their shape and size during the pitching motion. The influence of the LSBs on the airfoil upper surface during pitching motion continues to a higher incidence in comparison with that under static conditions before developing into a fully detached flow. Vortex merging is observed in the rear part of the LSBs in the turbulent portion for a Reynolds number of 30,000. At Reynolds number 60,000, the changing of the LSB length during pitching-up motion is similar to that of steady cases, except a delayed transition is observed as incidence increases. The results show further insight into the dynamic characteristics of the LSBs and their relation to the aerodynamic performance of the airfoil.

本文报道了在低雷诺数流量下向上运动时，与薄弯翼型的气动载荷不稳定性相关的层流分离气泡（LSB）的动力学特性的研究。雷诺数为30,000和60,000的4％c弧度薄机翼的非稳态雷诺平均Navier-Stokes（URANS）模拟。机翼以无量纲的俯仰角从0°到25°的迎角俯仰$\dot{\alpha }$分别为0.0398和0.0199。这$\mathit{ķ}-\mathit{\omega }$ SST $\gamma -\stackrel{〜}{\mathrm{[R}}{Ë}_{\mathit{t}}$湍流过渡模型用于解释过渡对LSB发育的影响。LSB在俯仰运动过程中会在形状和大小上发生变化。与在形成完全分离的气流之前的静态条件下相比，俯仰运动期间LSB对机翼上表面的影响继续以较高的入射率发生。在湍流部分的LSB的后部观察到涡旋合并，雷诺数为30,000。在雷诺数为60,000的情况下，向上倾斜运动期间LSB长度的变化与稳定情况相似，不同的是随着入射率的增加，观察到了延迟过渡。结果显示出对LSB的动力学特性及其与翼型气动性能之间关系的进一步了解。