Micron Size Particle Image Velocimetry by Fast Fourier Transform

In this paper, a non-intrusive, unique optical measurement technique of seeding polystyrene granular beads image velocimetry has been described. The flows of seeded particles are illuminated by laser light and double frame-single exposure images are captured at a specified interval of time. Images are segmented into sub interrogation domain and cross correlation of images are evaluated by Fast Fourier Transform method. From the captured images, particle displacement is calculated and then magnitude of the velocity of micron size seeds in the plane is estimated. This technique is most suitable for high density concentration of seeded particles. Laser speckle velocimetry has wide range of pulse separation time and reduction of noise in the estimation of fluid velocity without directional ambiguity.