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Unsteady Aerodynamics of Wings at Low Reynolds Numbers

低雷诺数下机翼的非定常空气动力学

基本信息

批准号：
157369417
负责人：
Dr.-Ing. Robert Konrath
金额：
--
依托单位：
Institut für Aeordynamik und Strömungstechnik (IAS)
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2009
资助国家：
德国
起止时间：
2008-12-31 至 2015-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/157369417?language=en
关键词：
Unsteady Aerodynamics Wings Low Reynolds

项目摘要

The research project aims to analyse comprehensively the unsteady flow development around plunging and pitching wings of low aspect ratio at low Reynolds numbers, i.e. below 100 000. The obtained results can be used for the development of new design methods of flapping flight mechanisms for an efficient generation of lift and trust in the low Reynolds number regime. Additionally, the project addresses also aspects of manoeuvrability and gust sensitivity of small air vehicles. As the Reynolds number reduces the wing aerodynamics are increasingly determined by large vortical flow structures. Therefore, the project places emphasis on a description of the three-dimensional unsteady flow fields, for which experimental as well as numerical simulation methods are adapted and further developed.In the first funding period of this project, flat plate wings of elliptical and rectangular planforms and aspect ratios of one and two are investigated while undergoing harmonic plunge and pitch motions. For the calculation of the aerodynamic loads from data of an internal force balance, different methods are investigated to determine inertial forces including a new optical measurement approach. Flow fields measured with PIV in several planes give insight in the three-dimensional flow development and are used for comparisons with results of accompanying flow simulations. Tomographic PIV measurements are planned as well to measure the three-dimensional flow fields at the wing tips showing the interaction of leading edges vortices of separation regions with the wing tip vortices.In the forthcoming funding period it is initially planned to analyse the harmonic cases quantitatively using the data obtained in the first funding period. Developed vortex identification methods allow a tracking as well as a calculation of the circulation strengths of individual vortices, with which the growing of vortices and vortex interactions can be quantitatively analysed . The major part of this funding period, however, concentrates on the investigation of non-harmonic wing motions. First, transient cases of impulsive plunge motions are considered that allow for an analysis of the influence of vertical gusts on the wing loads and flow topology which constitute a major issue for small air vehicles. Second, periodic motions are considered by means of applying long phases of constant angle of attack and plunge velocity with short turning phases in the upper and lower dead centre of the motion. For this case the higher efficiencies of thrust generation in comparison to the sinusoidal cases of the first funding period are of interest as well as the forced generation of vortices during the turning phases. A careful adjustment of kinematic parameters can lead to improved performances and, therefore, the underlying flow physics will be investigated as well.

本课题旨在综合分析低雷诺数（即低于10万）下低展弦比俯冲翼和俯仰翼周围的非定常流动发展。所得结果可用于在低雷诺数条件下高效产生升力和信任的扑翼飞行机构的新设计方法的开发。此外，该项目还解决了小型飞行器的机动性和阵风敏感性问题。随着雷诺数的减小，大涡结构对机翼气动性能的影响越来越大。因此，本项目注重对三维非定常流场的描述，采用实验方法和数值模拟方法，并对其进行进一步的发展。在本项目的第一个资助期内，研究了椭圆和矩形平台的平板翼以及一和二的宽高比，同时进行了谐波跳水和俯仰运动。为了利用内力天平的数据计算气动载荷，研究了确定惯性力的不同方法，其中包括一种新的光学测量方法。用PIV在几个平面上测量的流场可以深入了解三维流动的发展，并用于与随附的流动模拟结果进行比较。此外，还计划进行层析PIV测量，以测量翼尖处的三维流场，显示分离区前缘涡与翼尖涡的相互作用。在即将到来的供资期内，初步计划利用第一个供资期内获得的数据定量地分析谐波情况。发达的涡旋识别方法可以跟踪和计算单个涡旋的环流强度，从而可以定量分析涡旋的发展和涡旋的相互作用。然而，这一资助期的主要部分集中在非谐波机翼运动的研究上。首先，考虑了脉冲俯冲运动的瞬态情况，允许分析垂直阵风对机翼载荷和流动拓扑的影响，这构成了小型飞行器的主要问题。其次，通过在运动的上下止点处应用恒定攻角和俯冲速度的长相位和短转弯相位来考虑周期运动。在这种情况下，与第一个资助期的正弦情况相比，推力产生的效率更高，以及在转弯阶段被迫产生涡流，都是令人感兴趣的。仔细调整运动参数可以提高性能，因此，也将研究潜在的流动物理。