FIGURE 2 3D model of internals with (A) one-baffle, (B) Three-baffle, and (C) Four-baffle; (D) 3D printed internals based on 3D model

2.2 Image and Data Processing

All images were analyzed by Image J (version: 1.8.0) to determine the size and quantity of bubbles. The evaluation of the performance of the CMGD was based on the average diameter (d av) of bubbles. The bubble diameter was measured by the following steps: (1) setting scale, (2) selecting measurement area (15×15 mm), (3) calculating the equivalent diameter of bubbles. As shown in Figure 3A, the marked 4 chord lengths pass through the center of mass of the bubble as far as possible, and the final equivalent diameter of the bubble is the average of all chord lengths.27 The diameter(di ) of a single bubble is obtained by the above method, and the dav of bubbles was calculated by eq (1):
\begin{equation} d_{\text{av}}=\frac{1}{n}\sum_{i=1}^{n}d_{i}\ \ (n>300)\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ (1)\nonumber \\ \end{equation}