Unsteady Low Reynolds Number Aerodynamics

涉及非定常空气动力学的情况在各种大小的海洋、陆地和航空航天飞行器中都很常见。由于大气湍流和附近建筑物在低海拔地区的气流结构，飞机和汽车经常经历阵风。非定常空气动力学的进一步说明包括物体经历大的加速和拍打翅膀。不稳定现象会对这些车辆的性能和安全运行产生严重的不利影响。这对于在低速下飞行的小型飞行器来说尤其重要，因为在低速飞行时，流动的相对不稳定性更高，从而导致撞击和相对载荷的变化更大。尽管非定常空气动力学具有明显的重要性和众多的应用，但与定常空气动力学相比，对非定常空气动力学的理解非常有限。这部分是由于非定常流动的复杂性，以及在设计过程中经常使用定常和准定常假设的事实。然而，随着小型无人飞行器的使用越来越普遍，提高我们对非定常流动的理解变得越来越有必要。现有的非定常流动模型包括Kussner和Wagner开发的模型。这些模型将非定常气动载荷分为循环和非循环分量；涡量和附加质量。不幸的是，这些模型的应用受到相关假设的严重限制，包括小入射角和库塔条件的实施。本项目将利用实验设备来研究非定常、低雷诺数流体流动的性质。这项研究将寻求提高对具有显著附加质量和涡旋动力学效应的条件的理解。这项研究属于EPSRC的“流体动力学和空气动力学”研究领域。

Situations involving unsteady aerodynamics are common for marine, land andaerospace vehicles of all sizes. Gusts are frequently experienced by aircraft andautomobiles due to atmospheric turbulence and the flow structures shed by nearbybuildings at low altitudes. Further illustrations of unsteady aerodynamics includebodies undergoing large accelerations and flapping wings. The unsteadyphenomena can have a significant detrimental impact on the performance and safeoperation of these vehicles. This is particularly important for smaller flying vehiclestravelling at low speeds where the relative flow unsteadiness is higher, leading tolarger changes in incidences and relative loading.Despite the clear importance and numerous applications, understanding of unsteadyaerodynamics is greatly limited in comparison to that of steady aerodynamics. Thisis partly due to the increased complexity of unsteady flow as well as the fact thatsteady and quasi-steady state assumptions are routinely used in design processes.It is becoming increasingly necessary, however, to improve our understanding ofunsteady flows, as the use of smaller unmanned air vehicles becomes moreprevalent.Existing models for unsteady flow include those developed by Kussner and Wagner.These models divide the unsteady aerodynamic loading into circulatory and noncirculatory components; vorticity and added-mass. Unfortunately, the application ofthese models is severely restricted by the associated assumptions which includesmall angles of incidence and enforcement of the Kutta condition.This project will utilise experimental facilities to investigate the nature of unsteady,low Reynolds number fluid flows. The research will look to improve understanding ofconditions with significant added mass and vortex dynamics effects. This researchfalls within the EPSRC research area "Fluid dynamics and aerodynamics".