## 4 Results and Discussion
### First Query: Use of AI on CFD
#### 4.1.1 Analysis of Countries  
Additionally, an analysis of the country of origin of the retrieved publications was conducted. After excluding entries without a defined country (497 publications), administrative regions of other nations, and non-UN-recognized entities [65], a total of 103 countries were identified as contributors to AI and CFD research. Figure 3 presents the ten countries with the highest number of publications, with China leading (34% of the total), followed by the United States (16%). Below 1000 publications, India and the United Kingdom rank next.  
Figure 3: Geographical distribution of countries with the highest number of publications for the first query on the use of AI in CFD.  
Figure 2: Distribution by number of publications of the different languages used for their drafting. The ‘Other’ region has been expanded for more visibility.  
Among the top 10 countries, 3 belong to the European Union [66]: Germany (541 publications), Italy (263 publications), and France (237 publications). If the European Union was considered a single entity in terms of publication output in this field, it would rank second, with a total of 1812 publications.  
Based on publication volume in this research area, China and the United States emerged as the leading countries in the field. These results aligned with previous studies, highlighting their dominance in AI investment and model development in recent years [60; 67].  
Figure 4a illustrates the co-authorship relationships among the top 10 publishing countries. It revealed a strong collaboration between the United States and China in joint publications, as well as their capacity to engage with any of the ten most productive countries. Within Europe, the close cooperation among the European Union Member States was evident, but there was also a lack of stronger collaborations with Asian countries. Additionally, Figure 4a shows the temporal evolution with respect to the average year of publication of co-authorship for each country, highlighting China's emergence as a modern leader in this field, the increasing contributions of Asian countries in recent years [60], and the continued relevance of Europe as a significant research force.  
Figure 4b provides a broader perspective on collaboration networks, measured through co-authorship, including countries with at least ten publications. The generated clusters generated using the VOS method are displayed in different colors, emphasizing the strongest collaborations. Three major clusters stand out: the yellow cluster, including China and the United States; the red cluster, comprising India, Turkey, and other nations; and the green cluster, featuring the United Kingdom, Germany, and Italy.  
Unlike the yellow cluster, where intercontinental collaboration is evident, the red and green clusters exhibited a more regional focus. The green cluster included many European countries, with the United Kingdom and Germany maintaining strong collaborations with non-European countries, while nations with fewer publications, such as Italy and Spain, had more limited international connections. Additionally, the green cluster demonstrated stronger collaboration with Latin American countries, such as Chile and Ecuador, than with Asian or Oceanian nations. The red cluster, led by India, predominantly consisted of Asian countries but also included African and Oceanian nations, reflecting robust collaboration across these regions.  
Figure 4: Analysis of the co-authorship relationship between countries for the first query carried out. (**a**) Analysis with a temporal focus on the co-authorship of the first 10 countries with the highest number of publications. (**b**) Analysis by clusters of countries with publications (minimum 10 publications).