Computationally fast harmonic balance methods for unsteady aerodynamic predictions of helicopter rotors
Computationally fast harmonic balance methods for unsteady aerodynamic predictions of helicopter rotors
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DOI：
10.1016/j.jcp.2008.02.028
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发表时间：
2008-01
期刊：
影响因子：
--
通讯作者：
K. Ekici;K. Hall;E. Dowell
中科院分区：
文献类型：
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作者：
K. Ekici;K. Hall;E. Dowell
本文提出了一种用于直升机旋翼前飞和悬停非定常流场分析的谐波平衡法。前飞的空气动力学是高度非线性的，前进叶片上有跨音速流，后退叶片上有亚音速流，旋翼内部有失速流。然而，非定常流在时间上基本上是周期性的，这使得它非常适合于频域分析。本方法使用周期性的边界条件，允许一个模型的流场的计算网格上围绕一个单一的直升机叶片，无论实际的叶片数量。使用这种方法，我们计算几个解决方案，每一个对应于一个时期的几个时刻之一。这些时间水平通过计算域内部的谱时间导数算子和域边界周围的远场和周期性边界条件彼此耦合。在本文中，我们将该方法应用于三维欧拉方程（尽管该方法也可应用于三维粘性流），并研究机翼和旋翼的定常和非定常空气动力学。
A harmonic balance technique for the analysis of unsteady flows about helicopter rotors in forward flight and hover is presented in this paper. The aerodynamics of forward flight are highly nonlinear, with transonic flow on the advancing blade, subsonic flow on the retreating blade, and stalled flow over the inner portion of the rotor. Nevertheless, the unsteady flow is essentially periodic in time making it well suited for frequency domain analysis. The present method uses periodic boundary conditions that allows one to model the flow field on a computational grid around a single helicopter blade, no matter the actual blade count. Using this approach, we compute several solutions, each one corresponding to one of several instants in time over one period. These time levels are coupled to each other through a spectral time derivative operator in the interior of the computational domain and through the far-field and periodic boundary conditions around the boundary of the domain. In this paper, we apply the method to the three-dimensional Euler equations (although the method can also be applied to three-dimensional viscous flows), and examine the steady and unsteady aerodynamics about wings and rotors.