Researches on the Measurement of Bubble Velocity Based on Cross-Correlation
基于互相关的气泡速度的测量方法研究

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.