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

Bubbly flow widely exists in many industrial applica-tions 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 char-acteristics in the spatial field with traditional measurement meth-ods. In this paper, a novel laser scanning based three-dimensional (3-D) reconstruction method for dense bubbly plume is developed. The measurement area is scanned by a laser sheet through a rotat-ing 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 pre-processing 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. Also, 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 recon-struction method for dense bubbly flow based on laser scanning is valid with high precision, which explores a new way for the visual-ization of the 3-D structures and measurement of the volumetric flow field and the complex flow characteristics