基于互相关的气泡速度的测量方法研究

Researches on the Measurement of Bubble Velocity Based on Cross-Correlation

通过对比互相关技术和多普勒技术的差别,从一个新的角度把互相关技术应用于尾流测速的研究中.实验中利用高速CCD相机拍摄模拟尾流图像.利用快速傅里叶变换实现互相关算法,为提高计算准确度采用高斯曲线拟合互相关函数的峰值并给出拟合公式,得到了亚像素级的运动速度.为标定互相关算法的准确度,文中采用图像平移的方法验证算法的可行性和可靠性.最后把算法应用于模拟尾流的实验中.该方法有望在舰船尾流速度信息的实时获取上起到重要的应用价值.

Through researching on the velocity vector of bubbly wall in the ship wake, the bubble movement character can be found out. Also, the research and realization of the ship wake self-guide torpedo is based upon this character. After comparing the differences between Cross-Correlation and Doppler method, the Cross-Correlation method has been applied to the measurement of bubbly wall parameters in ship wake from a new aspect. The high-speed CCD camera is used to acquire the images of simulating ship wake, the velocity of bubbles in the ship wake is computed from image post-processing. Through improving cross-correlation algorithm commonly used for analysis of flow field, the Fast Fourier Transform （FFT） has been used to compute the cross-correlation function rapidly. In order to enhance the computing accuracy,Gauss curve fitting is used to modify the location of the max value point,and the fitting formula is listed,so the bubble velocity with subpixel accuracy is obtained. In order to calibrate the algorithm, the image transition is used to validate its feasibility and dependability. It is also applied to the experiment of simulative ship wake. The algorithm is expected to be used in acquring the real-time velocity information in the ship wake.