Euler-Lagrange study of Microbubble-Laden Turbulent Flow over Superhydrophobic surfaces

For slow-speed ships, underwater vehicles, and pipe transportation systems, viscous resistance accounts for a large proportion of the total energy losses. As such, various technologies have been developed to reduce viscous resistance and enhance energy efficiency in these applications. Air injection and surface treatment are two representative drag reduction techniques. Additionally, efforts to combine multiple drag-reduction techniques have been the subject of extensive research. In this study, the synergistic effects of integrating microbubble injection and superhydrophobic Surface(SHS) drag reduction approaches were analyzed. A 2-way coupling Euler-Lagrange approach was used alongside direct numerical simulation, based on the spectral element method, to investigate the synergistic effects of applying two separate drag reduction methods. Three types of SHS were investigated in our simulations; post type, transverse ridge type, and ridge type. The drag reduction performances and flow characteristics of the various configurations, with and without microbubble injection, were compared in a turbulent horizontal channel flow with $Re_{\tau}=180$. The results of these tests showed that, combining post-type SHS with microbubbles was the most effective, producing a synergistic drag reduction effect. However, combining microbubble injection with ridge-type SHS increased drag relative to ridge-type SHS alone, showing the importance of carefully selecting wall type for the best possible performance.