Controlling Flow Separation on a Thick Airfoil Using Backward Traveling Waves
Controlling Flow Separation on a Thick Airfoil Using Backward Traveling Waves
复制标题
DOI：
10.2514/1.j059428
复制
发表时间：
2020-09-01
期刊：
影响因子：
2.5
通讯作者：
Borazjani, I.
中科院分区：
文献类型：
--
作者：
Akbarzadeh, A. M.;Borazjani, I.
对 NACA0018 翼型上的低雷诺数流动 (Re=50,000) 进行大涡模拟 (LES)，以研究翼型吸力侧不同类型（向后/向前行波和驻波）的低振幅表面波（驱动）在失速迎角 (15 度) 下的流动控制。研究发现，受水中游泳者启发的向后（朝下游）行波比向前行波和驻波驱动更有效。仿真结果表明，降低频率f*=4（f*=fL/U，其中f为频率；L为弦长；U为自由流速度）、无量纲波长lambda*=0.2（lambda*=lambda/L，其中lambda为有量纲波长）和无量纲幅度a*=0.002（a*=a/L，其中有量纲幅度）的后向行波可以抑制失速。相反，在驻波或前行波驱动的情况下，翼型上的流动与基线类似地从前缘分离。因此，向后行波产生最高的升阻比。然而，对于较高振幅 (a*=0.008) 的行波，剪切层从驱动点开始变得不稳定，并产生周期性相干结构。因此，与低振幅情况相比，升力系数减小。
Large-eddy simulations (LESs) of low-Reynolds-number flow (Re=50,000) over a NACA0018 airfoil are performed to investigate flow control at the stall angle of attack (15 deg) by low-amplitude surface waves (actuations) of different types (backward/forward traveling and standing waves) on the airfoil's suction side. It is found that the backward (toward downstream) traveling waves, inspired from aquatic swimmers, are more effective than forward traveling and standing wave actuations. The results of simulations show that a backward traveling wave with a reduced frequency f*=4(f*=fL/U, wherefis frequency;L, chord length; andU, free flow velocity), a nondimensional wavelength lambda*=0.2(lambda*=lambda/L, where lambda is dimensional wavelength), and a nondimensional amplitude a*=0.002(a*=a/L, whereais dimensional amplitude) can suppress stall. In contrast, the flow over the airfoil with either standing or forward traveling wave actuations separates from the leading edge similar to the baseline. Consequently, the backward traveling wave creates the highest lift-to-drag ratio. For traveling waves at a higher amplitude (a*=0.008), however, the shear layer becomes unstable from the actuation point and creates periodic coherent structures. Therefore, the lift coefficient decreases compared with the low-amplitude case.