QUANTITATIVE VISUALIZATION OF VELOCITY DISTRIBUTIONS IN MULTI-PHASE FLOW

The particle image displacement (PID) method is used for quantitative visualization of two dimensional (2D) velocity distributions. In this method, many image pairs of the seeded particles in the multiphase flow are photographed on a negative film by double exposure. The direction and the magnitude of velocities are measured from the direction and the spacing of Young's interference patterns, which are scattered from the negative film illuminated by the coherent laser beam. The map of equal velocity distribution is reconstructed by the partial light of Young's interferogram passing though a pinhole set at an arbitrary angle and distance from the center of the beam axis on the back focal plane of a Fourier transform lens. The technique using a pinhole set at the back focal plane has the shortcoming that the image of visualization is inaccurate and dark because of using partial light from Young's interferogram. Therefore, a new technique using the multiplexed matched spatial filtering (MMSF) method is proposed here to overcome these defects.