Off-axis Revise of PIV Watertunnel Flow Display and Analysis System

Particle image velocimetry(PIV) is a novel flow field measuring technology.PIV system takes picture of the flow tracer particles twice or more and use software processing the particles images.Then the velocity of each position in the measured area will be calculated then the whole flow field information in this area can be obtained.In PIV common use,the laser slice and the CCD screen orientation are vertical.For the limitation in some special application condition,off-axis detecting may be adopted,in which way the laser slice and the CCD screen orientation are not vertical.So in PIV off-axis detecting,the camera optical system,the tracer particle used and the particle image processing are different from PIV common use.To improve the system measurement precision in off-axis detecting,some methods are adopted.The tracer particles are wrapped with silver coating to improve the reflectivity.Scheimpflug focus,adjusting the angle between the imaging lens and CCD target to fit Scheimpflug condition,is used in the experiments to achieve high definition particles images.Then standard Grid board and the processing software are used to revise the images to display and analyse the measured flow field.