Research on PIV Image Matching Algorithm of Turbulent Velocity Field Based on Circular Projection

Abstract

Based on the complexity and particularity of the images processed by the particle image velocimetry technology and the non-rigid motion mode of the fluid, a particle image matching algorithm with low complexity, high accuracy, anti-deformation, anti-rotation, high robustness to illumination and wide measuring range of velocity is proposed by combining the nature of the rotation invariance of circle and the theory of image warping. The algorithm uses transformation of circular projection instead of FFT to ensure that the information of interpretation window and the search area has sufficient similarity; the complexity of the algorithm proposed is greatly reduced by setting the quarter circle and establishing relative coordinate system; the size of the interpretation window can be changed with the characteristics of the flow field by setting the threshold of the number of particles and the threshold of the window size, which improves the accuracy and applicability of the algorithm; it makes the algorithm suitable for turbulent flow fields with high Reynolds number and large deformation by warping the image iteratively. Experiments have proved that the algorithm is suitable for matching images of turbulent flow which with rotational transformation, the matching rate is over 99%, and the complexity of the algorithm is the same order of magnitude as the cross-correlation algorithm based on fast Fourier transform.

Keywords

• Particle image velocimetry
• turbulent flow
• image warping
• adaptive window
• circular projection
• curl