Implicit computational fluid dynamics methods for fast analysis of rotor flows
Implicit computational fluid dynamics methods for fast analysis of rotor flows
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DOI：
10.2514/1.j051155
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发表时间：
2012-08
期刊：
影响因子：
2.5
通讯作者：
M. Woodgate;G. Barakos
中科院分区：
文献类型：
--
作者：
M. Woodgate;G. Barakos
基于Navier-Stokes方程的计算流体动力学（CFD）是目前直升机分析和设计中最有用的预测方法。计算流体动力学的主要缺点，也许是直升机制造商的设计部门接受它缓慢的原因，显然是由于CPU时间的大量要求和与低阶方法相比相对较慢的周转时间。然而，随着CFD算法和并行计算的发展，CFD分析的使用变得更加常规。典型的应用包括为旋翼性能代码提供翼型数据的计算和悬停飞行中旋翼的分析。然而，非定常流情况的计算仍然具有挑战性。本文提出了解决旋翼机非定常流问题的其他方法，这些方法的目的是将时间推进非定常计算减少到更易于管理的稳态解。到目前为止，利物浦CFD实验室研究的技术包括时间线性化和谐波平衡法。这些方法的细节沿着在直升机多块计算流体动力学求解器的框架中给出。从俯仰/平移翼型到完整的转子，得到了几种流动情况的结果。结果突出了时间线性化方法的局限性和谐波平衡技术的潜力。结果发现，时间线性化的方法可以提供足够的结果的情况下，非定常流是一个相当小的扰动的一个已知的平均值。谐波平衡法具有较大的适用范围，为非定常流动的分析提供了足够的结果。所需的CPU时间减少，所需的核心计算机内存增加。总的来说，谐波平衡法似乎是一个可能的替代时间计算流体动力学的广泛的问题。
Computational fluid dynamics (CFD) based on the Navier–Stokes equations is by far the most useful predictive method available today for helicopter analysis and design. The main drawback of CFD, and perhaps the reason for its slow acceptance by design offices of helicopter manufacturers, is apparently due to the substantial requirements of CPU time and the relatively slow turnaround times in comparison to lower-order methods. However, progress with CFD algorithms and parallel computing has allowed CFD analyses to be used more routinely. Typical applications include computations of aerofoil data that feed rotor performance codes and analyses of rotors in hovering flight. The computation of unsteady flow cases is, however, still challenging. This paper presents alternative ways of tackling unsteady flow problems pertinent to rotorcraft using methods that aim to reduce the time-marching unsteady computations to more manageable steady-state solutions. The techniques investigated so far by the CFD laboratory of Liverpool include time-linearized and harmonic-balance methods. The details of the methods are presented along with their implementation in the framework of the helicopter multiblock CFD solver. Results were obtained for several flow cases, ranging from pitching/translating aerofoils to complete rotors. The results highlight some of the limitations of the time-linearized method and the potential of the harmonic-balance technique. It was found that the time-linearized method can provide adequate results for cases where the unsteady flow is a rather small perturbation of a known mean. The harmonic-balance method proved to have a larger range of applicability and provided adequate results for the analysis of unsteady flows. The required CPU time was reduced, and the required core computer memory was increased. Overall, the harmonic-balance method appears to be a possible alternative to timemarching CFD for a wide range of problems.