Interaction Effects in Tandem Configurations of Airfoils with Pitch/Plunging Motion

在自然界中，无论是在游泳还是飞行中，气动涡旋相互作用都是经常遇到的，其性质和作用的特征是雷诺数Re和降频k。昆虫飞行区域（低Re和高k）已经广泛应用于微型飞行器（MAV），而鸟类飞行和鱼类游泳时遇到的Re和k的中间范围却很少受到关注，特别是在实验上。在这个项目中，在达姆施塔特工业大学的低速风洞中已经提出了这样一个串联翼-翼设施，这将允许研究大范围的干扰效应。通过采用带俯仰/俯冲运动的翼型，将问题简化为二维情况，这既有利于使用时间分辨粒子图像测速技术（PIV）进行实验可视化，也有利于使用大涡模拟（LES）进行数值模拟。该项目的目的是深入了解利用旋涡干涉效应和相关效率来提高升力或推力的可能性。这个相当技术性的目标被认为是解释自然界中空气动力涡旋相互作用发生的必要的初步步骤。然而，从流动中提取能量的可行条件也将被研究。初期的资助主要集中在实验设备的建设和鉴定以及数值代码。初步的实验方案已经概述，并提出了进一步研究的可能扩展。特别是在第二个资助期将强调对生物学上有趣的结构的调查。

Aerodynamic vortex interaction is encountered frequently in nature, either in swimming or flying and is characterized in its nature and effect by the Reynolds number (Re) and the reduced frequency (k). Whereas the region of insect flight (low Re and high k) has been extensively investigated with application to Micro Air Vehicles (MAV), the intermediate range of Re and k encountered with bird flight and fish swimming has received much less attention, especially experimentally. In this project such a tandem wing-wing facility for the low-speed wind tunnel at the TU Darmstadt has been proposed, which will allow investigation of a wide range of interference effects. By using airfoils with pitch/plunge motion the problem has been simplified to the two-dimensional case, which is advantageous both for the experimental visualization using the time-resolved particle image velocimetry technique (PIV) and for the proposed numerical simulations using Large Eddy Simulations (LES).The aim of the project is to provide insight into the potential augmentation of lift or thrust using vortex interference effects and the associated efficiency. This rather technically orientated goal is felt to be an essential preliminary step in interpreting occurrences of aerodynamic vortex interaction in nature. However also the conditions under which energy extraction from the flow is feasible will be investigated. The initial funding period concentrates on construction and qualification of the experimental facility and numerical code. An initial experimental program has been outlined and possible extensions for further studies have been proposed. In particular the investigation of biologically interesting configurations will be emphasized in the second funding period.