Abstract

An experimental method for determination of aerodynamic loads is presented. It is based on velocity vector field results obtained with Particle Image Velocimetry (PIV). As PIV is an optical measurement technique, the developed method for load determination can be defined as noninvasive. It is shown that the only information needed to estimate the lift and drag forces exerted on a body placed in the flow is a velocity distribution measured around the investigated object. Therefore, PIV results provide sufficient input experimental data to be used. Fundamental fluid mechanics theories were employed to develop algorithms for load estimation. Determination of the lift force is based on velocity circulation calculations. It is obtained by integrating the velocity field along a closed-loop encircling the body. An essential achievement made is the development of a procedure for finding an optimal size of the integration curve used for lift calculations. In the case of the drag force estimation, an analysis of fluid momentum changes has been used. The momentum deficit, within a given control volume containing the analysed aerofoil, is determined and related to the reaction drag force exerted on the body. Additionally, pressure field reconstruction based on velocity data, which enabled an application of small control surfaces and kept the drag estimation error at a satisfactorily low level, was introduced. The developed method was tested and verified with the reference computational fluid dynamics simulation results and applied further to the wind tunnel experimental data. A flow around the standard NACA0012 aerofoil at two flow regimes was investigated (Re=\(0.7\times 10^5\) and Re=\(1.4\times 10^5\)). Lift and drag coefficient characteristics as a function of the angle of attack were obtained. An exceptional agreement between the experimental and reference numerical lift characteristics was attained (relative differences no larger than 5%). In the case of drag estimation, an acceptable level of similarity was observed (max. discrepancies below 20%).

Graphic abstract

中文翻译：

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基于速度数据的机翼特性的循环和流体动量变化方法确定，包括控制面尺寸独立性测试

摘要

提出了一种确定空气动力载荷的实验方法。它基于通过粒子图像测速（PIV）获得的速度矢量场结果。由于PIV是一种光学测量技术，因此用于负载确定的已开发方法可以定义为非侵入性。结果表明，估计施加在流中物体上的升力和阻力的唯一信息是在被调查物体周围测得的速度分布。因此，PIV结果提供了足够的输入实验数据供使用。利用基本流体力学理论来开发负荷估算算法。提升力的确定基于速度循环计算。它是通过沿围绕人体的闭环对速度场积分而获得的。取得的一项重要成就是开发了一种程序，该程序可以找到用于升程计算的积分曲线的最佳尺寸。在阻力估计的情况下，已经使用了对流体动量变化的分析。确定在包含分析的机翼的给定控制体积内的动量赤字，并将其与施加在身体上的反作用力相关联。另外，引入了基于速度数据的压力场重构，该重构使得能够应用较小的控制面并将阻力估计误差保持在令人满意的较低水平。所开发的方法已通过参考流体动力学仿真结果进行了测试和验证，并进一步应用于风洞实验数据。\（0.7 \ times 10 ^ 5 \）和Re = \（1.4 \ times 10 ^ 5 \））。获得了升力和阻力系数特性与迎角的函数关系。在实验和参考数值升力特性之间达成了一个特殊的协议（相对差异不大于5％）。在阻力估计的情况下，观察到可接受的相似度（最大差异低于20％）。

图形摘要