Design And Flow Field Experiment Of The PIV Measuring System Based On Frame-straddling Technology

Particle Image Velocimetry(PIV) has become one of the most popular flow field measuring methods and has been applied in many research fields. As far as the related research is concerned in China, only the applications of the system and the PIV algorithm are still on the research. The research for PIV measuring system itself is very few among the Chinese researchers because of the complexity of the system. Fixed internal time delay for the adjacent image pairs is adopted in the traditional PIV measuring system. As for measuring the time varying flow field, the traditional way might reach the limit of dynamic measuring range and lose parts of the measuring accuracy. In this paper, we designed a new kind of frame-straddling PIV measuring system to deal with above problems in traditional PIV system based on the existing flow field measuring platform. We adopted a new method that the system could change the internal time delay for the adjacent image pairs dynamically in order to improve the measuring range and the accuracy for the time varying flow field. The concrete research contents are as follows:(1) A new kind of formation system is designed to meet the demand of the measuring flow field. The formation system concern about two cameras whose trigger control is external. The error of the adjacent image pairs is within one pixel after carefully optical designed base on the beam-split technique, accurate mechanical design and system calibration experiment.(2) A embedded image processing system is implemented parallel computing method. The system has implemented the function of image capturing, image processing, resulr shown and feedback control. An cross-correlation algorithm based on FFT change has been adopted to calculate the vector of the flow field.(3) Simulation experiments and flow field experiments have been implemented the results of the calculated vector for each experiment have been analyzed.The results show that the designed PIV measuring system could improve the dynamic measuring range as well as the measuring accuracy for the time varing flow field.