Research Of Real-time Adaptive PIV Measurement Technique Oriented To Unsteady Flow Field

As a new measurement technique that intergrates computer,optical and image processing technology,PIV(Particle Image Velocimetry)has developed greatly since 1980 s,and it gradually becomes one of the main methods of flow field measurement.The velocity of flow field changes with time in unsteady flow,and the time interval between the images acquired by the traditional PIV is fixed,which can not meet the demands of high precision and the big dynamic range of unsteady flow field measurement.Aiming at this limitation,a real-time adaptive PIV(RTA-PIV)measurement technique has been proposed in the thesis.According to the requirement of real time adaptive PIV,a set of embedded hardware platform is designed,and the firmware of the hardware platform is designed to realize the measurement of real time adaptive PIV.Main research work is as follows:(1)The present PIV measurement system uses open loop control and off-line processing.In view of the situation,a real-time adaptive PIV measurement technique is proposed,in which the time interval of frames in next moment is adjusted according to the current velocity calculated by system.With this technique,on line measurement and closed-loop control of time varying flow field measurement can be realized;(2)An embedded hardware platform is designed for the real-time adaptive PIV,which includes an image acquisition unit and an image processing unit.The image acquisition unit is based on framing technology with Camera Link protocol,in which two scientific CMOSs are used as image sensors and FPGA is used as the processor.It can achieve the adjustment of time interval between frames.The image processing unit is based on the integrated architechture of one FPFA and two DSPs,in which the SRIO(Serial Rapid IO)is used for data exchange to achieve high-speed data transmission and real-time processing;(3)The firmware system is designed on the hardware platform which includes the firmeware of power supply chip on FPGA,the control and processing of the image data on FPGA,firmware of SRIO protocol on FPGA,firmware of power supply chip and clock chip on DSP,DSP booting,programming of SRIO and Ethernet on DSP.The firmware design is verified,which provides support for real-time adaptive PIV measurement technique;(4)The algorithm of real-time adaptive PIV is proposed.The PIV measurement experiment of the unsteady flow field is carried out by using the whole system.The results show that the real time adaptive PIV measurement technology is effective.