Simultaneous Image Measurement of Unsteady Flying due to Interaction

利用由PIV和两个高速摄像机组成的MOFIA系统，同时测量了小薄盘在水中的下落运动及其周围的水流速度场。用PIV测量了圆盘周围的速度场。荧光示踪粒子被用来将其波长与激光的波长和用于CCD相机拍摄的图像的光的波长分开。以直径为10 mm的圆盘为标准，利用两台高速摄像机的图像重建了圆盘的三维运动。密度为1000~7800 kg/m~3，厚度为0.07~1 mm。此外，还对象限和正方形平板进行了研究。实验结果表明，圆盘的运动受其密度和厚度的影响。随着圆盘密度的增大，运动由二维之字形运动变为螺旋形运动。在高密度圆盘的情况下，观察到了一种混沌运动，特别是带有空翻的三维之字形运动。以圆盘象限模拟的机翼(半径为20 mm，厚度为0.3 mm)为例，采用MOFIA方法研究了机翼与周围流动的相互作用。当机翼向下扑动时，可以观察到涡旋的产生、旋涡的脱落以及扑翼引起的吸力或推力流动。还测量了一只菜心蝴蝶的翼面形状。

The motion of small thin disk falling down in water and its surrounding water velocity field were measured simultaneously by using the MOFIA system, which is composed by PIV and two high speed CCD cameras. The velocity field around disk was measured by PIV. The fluorescent tracer particles were used to separate its wavelength from both that of YAG laser and those of lights for images taken by the CCD cameras. The three dimensional motion of disk was reconstructed using the images of two high-speed cameras.Disks of 10 mm diameter were used as standard in the study. Their density and thickness were 1000 to 7800 kg/m^3 and 0.07 to 1 mm, respectively. Quadrantal and square plates were also investigated. The experimental results show that the motion of disk was affected by its density and thickness. The motion changed from two-dimensional zig-zag motion to spiral motion with density of disk. In the case of a high density disk, a chaotic motion, especially a three-dimensional zig-zag motion with somersault was observed.Using a wing (radius 20 mm and thickness 0.3 mm) modeled by quadrant of disk, the interaction between the wing and surrounding flow was investigated by use of MOFIA. With flapping-down of the wing, vortex generation, vortex shedding, and suction or pushing flow due to flapping of wings were observed. The shape of wing surface of a cabbage butterfly was also measured.