Flow Visualization and Image Measurement on a Bubble Jet Flow and Its Post-Processing by Using POD

Abstract

Bubble jet flows are seen in a lot of industrial fields such as power plant, chemical plant and bio-reactor. PIV is very useful tool in order to investigate the bubble's behaviors and flow structures in liquid phase simultaneously. Because it is possible to measure two- or three-dimensional flow structures and the whole flow fields aren't disturbed by measurement instruments. Recently, Dynamic PIV system consisted of high-speed camera and high-repetition laser has been developed. It is possible to capture time-serial images with high temporal resolution. In this paper, a system combined dynamic PIV and IST (Infrared Shadow Technique) with single high-speed camera, a double-pulse laser for illumination of particles and a diode laser for illumination of bubbles is developed in order to capture particles and bubbles simultaneously. Some techniques about image pre-processing to separate particles and bubbles and velocity calculation by PIV/PTV are introduced. POD (Proper Orthogonal Decomposition) is furthermore applied to time-series liquid phase velocity vectors. It is revealed that the effect of spatio smooth filter is obtained by reconstructed velocity vectors in lower spatio mode by POD and it is changed from large vortex structures to small vortex structures as the spatio mode becomes higher.