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空间流体实验具有无人操作的特殊性,需要对监控图像进行实时处理,得到目标参数.本文研究了利用照相机捕捉到的液滴灰度图像,分析求取液滴的表面张力、接触角、体积等物理参数的方法.针对液滴的灰度图像,利用边界提取、域值分割等图像处理方法,得到液滴的基本轮廓.建立基于液面像素点坐标的拉普拉斯方程,运用牛顿-拉夫逊法、龙格-库塔法、坐标轮换法等多种数值方法,对液滴的边界进行拟合,寻求最优的轮廓拟合点.根据最优的拟合点,确定液滴的物理参数.提出了利用牛顿法与一维寻优相结合的算法进行轮廓拟合的方法,并与文献[1]提出的算法进行了比较,证明了该方法具有收敛速度较快,拟合精度较高的特点.该方法是实现空间蒸发液滴热毛细对流和接触角测量实验的一项关键技术,同时也可以运用到非接触测量的实验场合.
The space fluid experiment has the uniqueness of unmanned operation and needs to process the monitoring image in real time to obtain the target parameters.This paper studies the grayscale images of the droplets captured by the camera and analyzes the surface tension of the droplets, the contact angle, the volume And other physical parameters.For the grayscale image of the droplet, the basic contour of the droplet is obtained by using the image processing methods such as boundary extraction and domain value segmentation.Lablas equation based on the pixel coordinates of the liquid surface is established, the Newton- Raphson method, Runge-Kutta method, coordinate rotation method and other numerical methods to fit the boundary of the droplet to find the best contour fitting point.According to the best fitting point, determine the droplet’s Physical parameters. A method of contour fitting based on the combination of Newton method and one-dimensional optimization is proposed and compared with the algorithm proposed in [1]. It is proved that the proposed method has the advantages of fast convergence, This method is a key technology to realize the experiment of measuring capillary convection and contact angle of evaporating droplets in space, and can also be applied to the experiment of non-contact measurement.