数字粒子图象测速技术(DPIV-Digital Particle-Imaging Velocimetry)已在国内外得到广泛的重视和应用,但目前其最大的问题是精度问题.由于DPIV的图象数据是用CCD摄像机经相应的图象卡采集示踪粒子图象得到的,这样在实验过程中不可避免引入的噪声(主要是示踪粒子大小、示踪粒子数量、诊断窗口大小、诊断窗口内的速度梯度和量化效果等引入的噪声)降低了实验测量的精度.本文应用小波变换的多分辨率特性,对DPIV图象(模拟和实际图象)进行去噪处理,并与维纳去噪和中值去噪进行比较

DPIV (Digital Particle-Imaging Velocimetry) has been attached importance to and applied wisely interiorly and overseas. But at present, its most difficult problem is the precision. Because the tracer particle images of DPIV are sampled by CCD and image digitizer, the noise (mainly the noise of particle image size, the size of interrogation window, local velocity gradients, the number of particles within the sampling window and quantization effects) that is imported inevitably in the process of experiment falls the precision of DPIV experiment. This paper presents the image (simulative and practical image) noise removing in DPIV based on wavelet transform whose characteristic is the multiresolution. This method is compared with image noise removing by Wiener and median filter. The result shows that image noise removing in DPIV based on wavelet transform improves the precision of DPIV experiment, and it is the most precise to rebuild the velocity field based on cross-correlation after image noise removing in DPIV using wavelet transform.