风洞试验模型表面的荧光油膜路径运动速度测量

Velocity measurement of fluorescent oil film path movement on wind tunnel testing model surface

风洞试验模型在气流脉动作用下小幅振动,导致光流法从荧光油膜时序图像中解得的荧光油膜路径运动速度含有模型运动速度,降低了荧光油膜全局摩阻测量准度。为此,提出试验模型表面的荧光油膜路径运动速度测量方法,将模型表面的背景纹理(如人工网格线或其他典型特征)作为基准,利用图像相关法离散匹配,获得相邻时序图像中背景纹理的(几何位姿)映射矩阵;基于模型运动的连续性,推导了映射矩阵的全局优化方程,并结合光流法,实现了模型振动与其表面荧光油膜路径运动的解耦。Oseen涡对的荧光油膜路径运动速度场仿真试验结果表明:在给定的平移旋转条件下,本文方法的计算结果(沿Oseen涡核连线分布的测量速度)与理论值的最大相对误差为4.1%,较无平移旋转条件下的光流计算结果最大相对误差仅增加0.6%。2m量级高速风洞某空腔试验与机翼试验的荧光油膜路径运动速度测量结果进一步显示:本文方法测得的流动现象正确,能得到定量、清晰的表面摩擦应力线图谱与油膜路径运动速度场,较传统方法优势明显,工程应用价值大。

The vibration of the wind tunnel testing model under the flow pulsation leads to the inclusion of the model movement velocity in the fluorescent oil film path velocity directly computed by optical flow method,decreasing the accuracy of surface friction measurement.Therefore,a velocity measurement for fluorescent oil film on a testing model surface is presented.The method uses the background texture(such as artificial grid lines or other typical features)as benchmark to obtain the map matrix(geometric posture)based on the image correlation method and the discretion match for the adjacent timing images.The global optimization equation is also derived based on the continuity of the model movement,and then the movements of the testing model and the fluorescent oil film are decoupled.The simulation of the fluorescent oil film movement for a Oseen vortex pair has demonstrated that the maximum relative velocity error along Oseen vortex cores is 4.1%for the given parameters of translation and rotation.It has only 0.6%increment compared with that of the optical flow method tackling no translation and rotation images.The measurement of fluorescent oil film on a cavity testing model in 2 mscale high-speed wind tunnels has further showed that not only the measured flow phenomenon is correct,but also it is capable to obtain the quantitative and clear surface friction line map and oil film velocity field.Therefore,its advantages are obvious comparing with the tradition methods,and its engineering application value is high.