A 3-D Reconstruction Method of Dense Bubbly Plume Based on Laser Scanning

Abstract

Bubbly flow widely exists in many industrial applications of energy, metallurgy, and chemistry, etc. Due to the clusters and overlap of dense bubbles at a high void fraction, it is nearly impossible to obtain the information of flow structures and characteristics in the spatial field with traditional measurement methods. In this paper, a novel laser scanning based 3-D reconstruction method for dense bubbly plume is developed. The measurement area is scanned by a laser sheet through a rotating hexagonal optical prism, and a high-speed camera captures the sequentially sliced images in the flow field, which is parallel to the scanning direction. Meanwhile, a scanning mathematic model is established, and its linearization is analyzed in detail. An image preprocessing method is developed to extract the features of the bubbly plume. To be specific, a method involves adaptive wavelet threshold denoising is developed to remove the noise. Moreover, methods regarding sliced image-matching and interpolation based on Log-polar transformation are presented to improve the spatial resolution effectively, and a set of image evaluation standards are designed to investigate the interpolation efficiency and accuracy. The experimental results conclude that the reported 3-D reconstruction method for dense bubbly flow based on laser scanning is valid with high precision, which explores a new way for the visualization of the 3-D structures and measurement of the volumetric flow field and the complex flow characteristics.