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Optical-Flow Method Based on Multi-scale Used in PIV

Author: SunLiZhi
Tutor: SunHeQuan；LiGuangWei
School: Dalian University of Technology
Course: Port, Coastal and Offshore Engineering
Keywords: PIV Cross-correlation Computer Vision Optical flow Multiscale Template
CLC: TV131.6
Type: Master's thesis
Year: 2006
Downloads: 225
Quote: 1
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Abstract


The flow rate measuring apparatus, or methods commonly used in hydrodynamic experiments, aerodynamic experiment, such as the ultrasonic Doppler velocimetry instrument (ADV), the laser Doppler velocimetry (LDV), etc., can only flow field a single point measurement, and the majority of instruments, the application needs to contact or enter the flow field, can not be carried out without disturbance measurements of two-dimensional flow field in the measurement area. Sensitive to external interference when the flow rate changes within the flow field and a dramatic change in the space, and the need to measure the two-dimensional flow field velocity distribution, the single point of contact type measuring instrument has been unable to meet the measurement requirements. PIV technology is a non-contact flow measurement techniques developed in the past 20 years, the cross-correlation analysis of Get motion information flow field, to overcome the limitations of single point of-contact measurement equipment, to the plane two-dimensional flow field by convection field image The test is a very promising no disturbance flow field measurement techniques have been successfully applied in the hydrodynamic experiments, two-dimensional flow field measurements of aerodynamic experiments for researchers insight into the velocity distribution of the flow field inside the an effective means. The vast majority of the traditional PIV algorithm is based on the area related to the cross-correlation algorithm. This method because the concept is simple, easy to implement, and the technology is mature and widely used. Cross-correlation algorithm have a lot of defects, the main results obtained by this algorithm mismatch are more, not smooth and continuous flow field, and thus require a lot of follow-up work to increase the workload at the same time reduces the computational results accurate degrees. Motion analysis theory in computer vision PIV image processing using optical flow algorithm PIV image processing. Smoothness constraint conditions and the technology of multi-scale image, the algorithm significantly improved the defects of the traditional cross-correlation algorithm to improve the quality of the results of the vector field. Optical flow algorithm is a computer vision approach abstract from fluid mechanics, the continuity equation of fluid mechanics abstract optical flow constraint equation, through local smooth conditions can be deduced from the optical flow constraint with this the velocity component of the two constraints iterative computation, each pixel can be obtained. When calculated using the pyramid data structures, changing the scale of the image processing calculations, the obtained result is more accurate, and the flow field is more continuous and smooth, but also can improve the calculation speed. Finally the results of the calculation of the optical flow algorithm and the traditional algorithm compared to verify the superiority of the optical flow algorithm. In program design, extensive use of the C program design features, such as templates and inline functions, which greatly improves the efficiency of the program running.

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CLC: > Industrial Technology > Hydraulic Engineering > The basic science of water resources project > Hydraulics > Hydraulic theory, calculation, experiment > Hydraulics Laboratory
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