An overlapping bubbles partition method in aerated water flows

The main step of water characteristic analysis by image measurement is counting the number of bubbles accurately and quantitative analysis of the bubble characteristics. One of the main reasons which influence the accuracy of analysis is the existence of overlapping bubbles. An overlapping bubble splitting method is proposed in this paper. Firstly, the convex hull of the overlapping objects is obtained. Secondly, the candidate concavities are founded on the contour of the object in each concave residuum after the iterated search, and then, the departing point pairs of the overlapping bubbles are then obtained by matching based on middle axis (MA). Finally, an optimal splitting conic can be gained by minimum mean square error (MMSE) ellipse fitting with constrains of concavities, which ensures the accuracy of the overlapping area calculation. Experimental results show that the method can split the overlapping bubbles efficiently and improve the accuracy of the bubble characteristic analysis in aerated water flows.