【论文翻译】求校正

The ability to model accurately and efficiently unsteady aerodynamic effects for actively controlled trailing-edge flaps (ACFs) is crucial for practical application of such systems for vibration and noise reduction as well as performance enhancement.Two-dimensional unsteady airloads due to oscillating flapmotion are calculated and compared using various computational fluid dynamics (CFD) codes and a CFD-based reduced-order model (ROM). This ROM is based on the rational function approximations approach, which yields a state-space, time-domain aerodynamic model suitable for incorporation into comprehensive rotorcraft simulation codes. The accuracy of this model is demonstrated across a practical range of unsteady flow conditions encountered by active flaps. Two Reynolds-averaged Navier–Stokes solvers (CFD++ and OVERFLOW) are employed in conjunction with various turbulence models, including large eddy simulation based models, so as to examine code independence. Flow physics associated with three-dimensional effects, flap hinge gap, as well as compressibility effects are also examined.

精确高效地对主动控制后缘襟翼（ACFs）进行非定常气动特性建模分析，对将此类系统实际运用到减震降噪、性能优化上来说至关重要。由襟翼振动引起的二维非定常气动载荷，使用多种计算流体力学（CFD）代码及一个基于CFD的降维模型（ROM）进行计算对比。此降维模型基于有理函数逼近法，这种方法提供了一种适合并入综合性旋翼机仿真代码的时域状态空间气动力模型。这种模型的准确性经由主动襟翼遭遇一系列非定常流状态试验证实。两个雷诺时均方程求解器（CFD++和OVERFLOW）与多种湍流模型结合，其中包括基于大涡模拟的模型，以便考察代码的独立性。与三维特性、襟翼铰链间隙及压缩性相联系的流体物理也进行了考察。

With the advent of actively controlled trailing edge flaps (ACFs) as a viable control device for vibration and noise reduction in helicopters, the requirement to accurately model and understand the aerodynamic effects of unsteady flap motion has become important (Refs. 1–8).The first studies on ACFs have employed classical quasisteady Theodorsen-type aerodynamics to represent the effect of the flaps for active vibration reduction (Ref. 9). Subsequently, more refined aerodynamic models were developed for use in comprehensive rotorcraft simulation codes, so as to account for unsteadiness, compressibility, as well as time-varying freestream effects. An example of such models is
that developed by Leishman based on indicial aerodynamics (Ref. 10). Approximate unsteady airloads due to arbitrary airfoil and flap motion were obtained via Duhamel superposition integral using Wagner’s indicial response functions. This model accounts for compressibility and can be extended to time-varying freestreams (Ref. 11). The Leishman
model has been incorporated in comprehensive rotorcraft codes such as UMARC.

随着主动控制襟翼（ACFs）成为一种可行的直升机减震降噪的控制装置，准确建模、认识襟翼非定常气动特性已经越来越重要[1-8]。在ACFs的最初研究中，已应用经典的半稳定西奥多尔森型空气动力学展现用于主动减震的襟翼的特性。随后，更多精确的气动模型被开发出来，用于综合性旋翼机仿真代码，以计入不稳定性、压缩性与时变来流的影响。这类模型的一个例子是利什曼开发的基于显示空气动力学的模型[10]。由旋翼和襟翼的任意运动引起的非定常气动载荷的近似值通过瓦格纳指数响应函数的杜哈梅积分得到。这个模型考虑了压缩性，可推广到时变来流[11]。利什曼模型已被并入诸如UMARC的综合性旋翼机代码。

The rational function approximation (RFA) approach has been used to generate a Laplace transform or state variable representation of the unsteady aerodynamics for fixed wing applications. The principal advantage of such an aerodynamic model is its compatibility with equations of motion with periodic coefficients that govern the rotary wing aeroelastic problem in forward flight. A time domain unsteady aerodynamic model based on the RFA approach has been developed for rotary wing applications by Myrtle and Friedmann (Ref. 5). This model was implemented in a comprehensive code AVINOR (active vibration and noise reduction) (Ref. 12) used in several studies focused on the use of active flaps for helicopter noise and vibration reduction (Refs. 5, 7, 13, 14) as well as performance enhancement for rotor power reduction (Ref. 15). The RFA model is an unsteady, compressible statespace aerodynamic model formulated in time domain. Its advantages are
that (1) it allows a convenient combination of the unsteady aerodynamics with the structural dynamic model, (2) it facilitates the solution procedure of the combined system using numerical integration, and (3) it yields a degree of computational efficiency required for the implementation of active control techniques using partial span trailing edge flaps.

在固定翼领域，有理函数逼近法(RFA)已被用于生成拉普拉斯变换或说明气动变量表示。这类气动模型的主要优点在于，它与带周期参数的运动方程具有兼容性，这些周期参数对前飞时的旋翼气弹问题有影响。在旋翼领域，默特尔与弗里德曼已开发出一个基于RFA的时域非定常气动模型[5]。这个模型包含在一个应用于多个研究的综合性代码AVINOR(主动减振降噪)[12]中，这些研究集中于主动襟翼在直升机减振降噪[5,7,13,14]及以降低旋翼操纵力为目的的性能优化[15]方面的应用。这个RFA模型是一个时域内的非定常可压缩状态空间气动模型。其优点有：（1）它实现了非定常气动模型与结构动力模型的简便结合；（2）它促进了对结合而成的系统的数值积分求解程序的开发；（3）它给出了使用部分展长后缘襟翼的主动控制技术生效所需的计算效率。

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Two correlation studies employing RFA aerodynamics in a comprehensive rotorcraft simulation code have been conducted and compared with experiments (Refs. 13,16). Despite the relative simplicity of theRFA model, these correlation studies have produced reasonably good agreement with the experimental data. There is very limited amount of dependable experimental data that captures the effect of an oscillating flap on the unsteady aerodynamic loads on a two-dimensional airfoil/oscillating flap combination in compressible flow. A fundamental understanding of such configurations is required so that full-scale experiments with active flaps (e.g., NASA/Boeing/DARPA/Army 2008 SMART rotor tests (Ref. 17)) can be simulated with a high degree of accuracy and computational
efficiency. Therefore, the application of computational fluid dynamics (CFD)-based numerical experiments offers a means for providing additional details about the unsteady flow field that can shed light on the physics of the problem. It is also important to note that actively controlled flaps used for vibration reduction can produce a performance penalty due to the unsteady drag associated with flap deflection. Accurate estimation of this drag penalty and its reduction play a central role in the practical implementation of the ACF system. Accurate unsteady drag prediction on a blade/oscillating flap combination by CFD is influenced by several factors such as mesh sizing and turbulence models. Thus the use of multiple CFD codes is important to obtain a code-independent conclusion.

两个在综合性旋翼机模拟代码中采用RFA空气动力学法的相关研究已经开展，并与试验进行了对比[13,16]。尽管该RFA模型相对简单，这些研究与试验数据符合性已算较好。对处于可压缩流中的带振动襟翼的翼型,反映振动襟翼对其非定常气动载荷影响的可靠实验数据很少。为了使主动襟翼全范围试验（如2008年NASA、Boeing与美国国防部、美国陆军联合进行的SMART旋翼测试[17]）的模拟达到高精确度与高计算效率，需要对此类布局有根本的认识。因此，基于计算流体力学（CFD）的数值实验，给出了一种可提供非定常流场详细信息的方法，这一方法可阐明该问题的物理学原理。同样重要的是，要注意到由于非定常阻力与襟翼偏转有关，用于减振的主动控制襟翼会对性能不利。准确估计其在阻力方面的不利影响并减少这种影响，对实现ACF系统的实际应用起着核心作用。用CFD对带振动襟翼的桨叶非定常阻力进行预测的准确性，受多种因素影响，例如网格大小、湍流模型。因此，使用多种CFD代码对获取与代码无关的结果十分重要。

这项研究专注于对带振动襟翼翼型阻力和力矩的准确预测,是一项早期研究[18]的后续与扩展。 本文的总体目标是，建立一个计算效率高的降维模型，该模型基于RFA法及其与不同CFD代码所得CFD结果的比较。本文的具体目标如下：

simulation的翻译更正为仿真

橙字是有问题的地方