## 4 Conclusions and Prospect  
In this work, the bubble evolution behavior on aluminum electrolysis anodes was observed in a see-through cell. The bubble distribution on flat and slotted anodes were analyzed using image processing and the statistical analysis method. The following conclusions can be derived:  
* From the bubble distribution patterns on the anode bottom surface, the bubbles tend to generate and adhere to certain regions of the anode surface due to the heterogeneity of the carbon material, and the adhering regions would move when the apparent current density was changed;
* For the three kinds of anode as investigated in this work, with the increase in apparent current density, the size of the bubbles that adhered to the anode bottom surface showed an overall decreasing trend, indicating a faster generating rate and faster releasing rate of the bubble under a higher current density;
* A slot on the 50 mm \(\times\) 22 mm graphite anode could reduce the average bubble size greatly, therefore reducing the actual anode current density significantly;
* When the graphite anode bottom working surface increased from 11 cm\({}^{2}\) to 50 cm\({}^{2}\), the bubble coverage rate, average bubble size, and the actual current density on the anode significantly decreased. For the 11 cm\({}^{2}\) anode, the variation of anode coverage with time reflects the evolution character of a single or several bubbles, while for the \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Bubble Size, mm\({}^{2}\)**} & \multicolumn{3}{c}{**Percentage against the Total Bubble Area Counted within 60 s, \%**} \\ \cline{2-4}  & **50 mm \(\times\) 22 mm Flat Anode** & **50 mm \(\times\) 22 mm Slotted Anode** & **100 mm \(\times\) 50 mm Flat Anode** \\ \hline
0 \(<\) Size \(<\) 100 & 23.3 & 92.4 & 39.8 \\ \hline
100 \(<\) Size \(<\) 200 & 7.5 & 7.6 & 14.5 \\ \hline
200 \(<\) Size \(<\) 300 & 11.9 & 0 & 12.0 \\ \hline
300 \(<\) Size \(<\) 400 & 25.8 & 0 & 6.8 \\ \hline
400 \(<\) Size \(<\) 500 & 29.7 & 0 & 6.0 \\ \hline
500 \(<\) Size \(<\) 600 & 0.7 & 0 & 5.9 \\ \hline
600 \(<\) Size \(<\) 700 & 0 & 0 & 3.9 \\ \hline
700 \(<\) Size \(<\) 800 & 0 & 0 & 2.4 \\ \hline
800 \(<\) Size \(<\) 900 & 1.1 & 0 & 0.9 \\ \hline
900 \(<\) Size \(<\) 1000 & 0 & 0 & 0.5 \\ \hline Size \(>\) 1000 & 0 & 0 & 7.3 \\ \hline Average size, mm\({}^{2}\) & 324 & 40 & 160 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The size distribution of the bubbles obtained from the see-through cell experiments, apparent anode current density 0.9 A/cm\({}^{2}\). 50 cm\({}^{2}\) graphite anode, the anode coverage was affected by the group effect of many independent bubbles;
* The effect of slotting on a larger graphite anode (50 cm\({}^{2}\)) would probably be weakened compared to that on a smaller 11 cm\({}^{2}\) slotted anode; however, more details need to be investigated in the future study. Information on the size of released bubbles need to be collected in the next step to provide more data for the investigation of bubble-driven electrolyte flow. Conceptualization and methodology, Y.Y. ; software, Y.Y. and Y.Z. ; validation, Y.Y. and J.Y. ; formal analysis and supervision, Z.W. ; investigation, Y.Z. ; data curation, Y.Z. ; writing--original draft preparation, Y.Y. and Y.Z. ; writing--review and editing, Z.S. ; project administration and funding acquisition, Y.Y. and Z.W. All authors have read and agreed to the published version of the manuscript. This research was funded by the National Natural Science Foundation of China and the Fundamental Research Funds for the Central Universities [grant no. 51804069, N2025033, and 51974081]. The data presented in this study are available on request from the corresponding author. the data can also be found in [PERSON]. (one of the authors of this paper)'s graduation thesis, from Northeastern University's online library system ([[http://www.lib.neu.edu.cn/index.html](http://www.lib.neu.edu.cn/index.html)]([http://www.lib.neu.edu.cn/index.html](http://www.lib.neu.edu.cn/index.html))).