The characteristics and control of a wingtip vortex are of great significance when considering drag reduction and flight safety of transportation aircrafts. The associated aerodynamic phenomenon resulting from rolling up of a wingtip vortex includes boundary layer flow, shear layer separation, and vortex breakdown, while the interaction of a wingtip vortex with the airframe causes induced drag, wingtip noise, etc. This paper studies a normal blowing method utilized to control the wingtip vortex. Large eddy simulation (LES) technique applied to a straight NACA0012 wing having a chord length () of 0.4 m is adopted for this study. The Reynolds number based on the chord length is and the angle of attack is 12°. The computational approach utilized the dynamic Smagorinsky-Lilly subgrid model for 3D simulations. Normal blowing from a high aspect ratio jet from the wingtip lower surface was used to control the wingtip vortex. From 0.05c to 0.30c, the blowing slit width was 1 mm, with the slit exit treated as a velocity inlet boundary condition which supplied the blowing jet with a momentum coefficient of 0.28%. Results of axial velocity and span-wise pressure distribution of the clean airfoil presented good agreement with known experimental data. LES results indicate that normal blowing suppresses the primary vortex strength, while the vortex core radius, maximum induced velocity, axial vorticity flux, and pressure peak of the primary vortex are reduced by 25%, 28%, 46%, and 52%, respectively. Flow field structures before and after blowing show that blowing suppresses the shedding, coiling, and convergence of the free vortex layers near the primary vortex. This study also shows that normal blowing generates a jet-induced vortex at the location of the secondary vortex, while backflow, volume expansion, and spiral burst can be observed in the jet-induced vortex. The bursting jet-induced vortex destroys the jet-like flow structure of the primary vortex at the trailing edge.

中文翻译：

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LES控制翼尖涡旋正常吹气方法的研究

在考虑减阻和降低运输机的飞行安全性时，翼尖涡旋的特性和控制具有重要意义。翼尖涡旋卷起引起的相关空气动力学现象包括边界层流动，剪切层分离和涡旋破裂，而翼尖涡旋与机身的相互作用会引起感应阻力，翼尖噪声等。用于控制翼尖涡旋的方法。本研究采用弦长（）为0.4 m的直NACA0012机翼的大涡模拟（LES）技术。基于和弦长度的雷诺数为迎角为12° 该计算方法将动态Smagorinsky-Lilly子网格模型用于3D仿真。来自翼尖下表面的高纵横比射流的正常吹气用于控制翼尖涡旋。从0.05 c到0.30 c，吹缝宽度为1mm，缝出口作为速度入口边界条件，其为吹流提供了0.28％的动量系数。清洁翼型的轴向速度和翼展方向压力分布的结果与已知的实验数据非常吻合。LES结果表明，正常吹气会抑制一次涡旋强度，而一次涡旋的核心半径，最大感应速度，轴向涡旋通量和压力峰值分别降低了25％，28％，46％和52％。 。吹气前后的流场结构表明，吹气抑制了初级涡旋附近自由涡旋层的脱落，卷曲和会聚。这项研究还表明，正常吹气会在次级涡旋的位置产生射流诱发的涡旋，而回流时，射流诱发的涡旋中可以观察到体积膨胀和螺旋爆裂。爆发的射流诱发的涡旋破坏了尾缘处初级涡旋的射流状流动结构。