Research On 2D PIV Of Liquid

Traditional movement measurement technique generally can only measure fixed point of flow field. Most instruments must be contacted or placed into flow field and cannot measure two-dimensional flow field. Fixed contact point measuring instruments cannot fulfill measuring requirement when the change of flow velocity is sensitive to exterior disturbance or fluctuates sharply in space, and when measurement of two-dimensional velocity distribution is needed. With the fast development of laser, as well as computer technique and image processing, flow measurement technique was developed quickly by using the laser as the light source, and PIV(Particle Image Velocimetry) technique came forth. PIV technique is a kind of non-contact flow field measurement, which can get the movement information of flow field by cross-correlation analysis of two flow field images. The great promising undisturbed flow field measurement technique gets over the limitation of the fixed contact point measurement instruments and can measure plane two-dimensional flow field. PIV technique has already been applied to two-dimensional flow field measurement of hydrodynamic experiments and aerodynamic experiments, and provides an effective way to study velocity distribution of flow field for scientific researchers.Many scholars have made a lot of research on PIV technique, but there is still much faultiness in theories and applications. As the density distribution of the particles in images is so asymmetrical that it usually brings imprecise correlation results. We bring forward systemic research on correlation algorithms which will promote the applications of PIV in projects, and that is the main purpose of this paper.In this paper, we focus on the cross-correlation analysis and the implementation of PIV. Their advantages and disadvantages are compared and analysed based on theories as well as experiments. Aiming at solving the asymmetry of the distribution of particles, we classified the particles in images by means of density clustering analysis. The area with higher particle density will be processed by traditional PIV technique, which lower density area will use PTV (Particle Tracking Velocimetry). This parallel method can increase the speed of processing and avoid the effect of the asymmetry. Then liquid velocity vector picture has been drawn which based on sorting the density of particles in this paper. The technique solves the asymmetry with good performance, and it is valuable for further consummation of 2D-PIV processing technique.