Wide domain simulations of flow over an unswept laminar wing section undergoing transonic buffet
Wide domain simulations of flow over an unswept laminar wing section undergoing transonic buffet
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DOI：
10.1103/physrevfluids.5.083903
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发表时间：
2020-08
影响因子：
2.7
通讯作者：
M. Zauner;N. Sandham
中科院分区：
文献类型：
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作者：
M. Zauner;N. Sandham
跨音速抖振是一种限制现代飞机安全飞行包线的非定常流动现象。采用跨度周期边界条件的尺度分辨模拟可以提供与抖振相关的流动物理的详细见解，并有助于校准所需的简化模型，例如，基于层流超临界截面开发更高效的机翼。然而，这种模拟通常只对严格受限的跨域是可行的。在目前的贡献中，我们分析了(达索航空公司V2C剖面的)未掠过层流机翼截面，在中等雷诺数Re=500,000和马赫数M=0.7下，展向区域分别等于翼型弦的5%和100%。一种隐式大涡模拟方法，使用谱误差估计器来控制高阶滤波器的作用，首先通过直接数值模拟进行验证，然后用于域宽研究。由于域大小的不同，量化差异包括在更宽的域中抖动的幅度和规律性的增加。然而，时空分析表明，上游传播的激波等关键物理现象在窄域内得到了很好的描述，并且对气动系数的区域大小的敏感性有限。即使在非常宽的区域，比在后缘测量的最大湍流结构宽一个数量级，某些特征仍然是二维的，包括与过渡上游边界层相互作用的激波和膨胀波。在一个典型的抖振周期中，跃迁机制发生了微妙的变化，在低升力阶段，Kelvin-Helmholtz结构突出，而在高升力阶段，斜模在激波/边界层相互作用之后发展。为了进一步研究抖振机理，利用宽域数据的可用性，考虑了相位平均数据和瞬时流场，以显示抖振的整体结构。
Transonic buffet is an unsteady flow phenomenon that limits the safe flight envelope of modern aircraft. Scale-resolving simulations with span-periodic boundary conditions can provide detailed insight into the flow physics associated with buffet and can help to calibrate simplified models that are needed, for example, to develop more efficient wings based on laminar-flow supercritical sections. However, such simulations are often feasible only for severely restricted spanwise domains. In the current contribution, we analyse an unswept laminar-flow wing section (of Dassault Aviation’s V2C profile) at a moderate Reynolds number of Re = 500,000 and a Mach number of M = 0.7 with spanwise domains equal to 5% and 100% of the airfoil chord. An implicit large-eddy simulation methodology, using a spectral error estimator to control the action of a high-order filter, is first validated against direct numerical simulations and then used for the domain width study. Quantitative differences, due to domain size, include an increase in amplitude and regularity of the buffet oscillations in the wider domain. Nevertheless, space-time analysis shows that key physical phenomena such as upstream-propagating shock waves are properly represented in the narrow domain and there is limited sensitivity to domain size of the aerodynamic coefficients. Even in the very wide domain, which is an order of magnitude wider than the largest turbulent structures measured at the trailing edge, certain features remain two-dimensional, including the shock and expansion waves that interact with the boundary layer upstream of transition. The transition mechanism is found to have subtle variations during a typical buffet cycle, with Kelvin-Helmholtz structures prominent during low-lift phases and oblique modes developing behind shock/boundarylayer interactions during high-lift phases. The availability of the wide-domain data is used for further study of the buffet mechanism, considering phase-averaged data and instantaneous flow fields to show the global structure of the buffet oscillation.