Mechanisms of Morphing Wall Flow Control by Traveling Waves over an Airfoil
Mechanisms of Morphing Wall Flow Control by Traveling Waves over an Airfoil
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DOI：
10.2514/1.j062449
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发表时间：
2023-01
期刊：
影响因子：
2.5
通讯作者：
Uchenna Emmanuel Ogunka;A. Akbarzadeh;I. Borazjani
中科院分区：
文献类型：
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作者：
Uchenna Emmanuel Ogunka;A. Akbarzadeh;I. Borazjani
变形壁面流动控制的两种主要机制是沿流向直接注入动量和通过触发不稳定性间接传递动量。行波已经被证明比驻波表现得更好，可能是因为它们可以使用两种机制。然而，这两种机制的相对重要性尚不清楚。为了区分这两种机制，在NACA 0018翼型上，在低雷诺数[公式：见正文]条件下，采用壁面分辨大涡模拟和锐界面曲线浸入边界法，对失速（15 °攻角）和过失速（20 °攻角）时的一系列参数（频率、振幅和起始位置）进行了测试。模拟结果表明，在失速和过失速迎角下，流动在无量纲频率、驱动振幅和振荡起始位置的范围内重新附着。在这些范围内还观察到显着的升力增强和阻力减小。流动再附着的无因次频率范围被发现是类似的主导无因次频率的未驱动翼型的前缘涡脱落。这表明动量的间接传递是主导机制，因为动量的直接注入随着振幅和频率的增加而增加;也就是说，分离应该随着振幅和频率的增加而减少。然而，直接注入的动量提高了性能相对于纯激发驻波时，不稳定性被触发。
The main two mechanisms of morphing wall flow control are direct injection of momentum in the streamwise direction and indirect momentum transfer via triggering instabilities. Traveling waves have been shown to perform better than standing waves, probably because they can use both mechanisms. However, the relative importance of the two mechanisms is not known. To differentiate between the mechanisms, a range of parameters (frequency, amplitude, and starting location) at stall (15 deg angle of attack) and poststall (20 deg angle of attack) is tested using wall-resolved large-eddy simulations with a sharp-interface curvilinear immersed boundary method at a low Reynolds number of [Formula: see text] over a NACA0018 airfoil. The results of the simulations demonstrate that the flow is reattached within a range of nondimensional frequencies, actuation amplitudes, and starting locations of oscillation at the stall and poststall angles of attack. Significant lift enhancement and drag reduction are also observed within these ranges. The nondimensional frequency range at which the flow is reattached is found to be similar to the dominant nondimensional frequencies of leading-edge vortex shedding of the unactuated airfoil. These indicate that the indirect transfer of momentum is the dominant mechanism because direct injection of momentum increases with the increase of amplitude and frequency; that is, separation should reduce as they increase. Nevertheless, direct injection of momentum improves the performance relative to pure excitations of standing waves when instabilities are triggered.