A method for recognizing overlapping elliptical bubbles in bubble image

Direct imaging technology is an effective and convenient method for the estimation of bubble size distribution (BSD). However, overlapping bubble has an influence on BSD when gas holdup is more than 1%. In this paper, we present a new method of overlapping elliptical bubble recognition to determine bubble size. The method mainly includes two steps: contour segmentation and segment grouping. Contour segmentation is on the assumption that the concave points in the dominant point sequence are always the connecting points, and segment grouping is mainly based on the average distance deviation criterion. Both simulated images and real bubble images are used to evaluate this new method. The results show that it is effective in the recognition of overlapping elliptical bubbles and have a potential in other elliptical object recognition. In the last, two methods are used for BSD estimation. It is found that the bubble size (such d10 or d32) estimated by the ignore method is slightly smaller than that estimated by the recognition method.

► The method mainly includes two steps: contour segmentation and segment grouping.
► Contour segmentation is based on the concave points in the dominant point sequence
► Segment grouping is mainly based on the average distance deviation criterion.
► BSD estimated by the ignore method and the recognition method is different.