The use of air bubbles injected into viscous fluid flows to reduce frictional drag has been extensively studied for industrial applications, especially in the marine industry. However, the lack of control over air bubble stability, size, and shape has limited its widespread adoption. This research explores the use of laser-based surface wettability modification techniques to enhance control over air bubble behavior in water flows.

Using nanosecond laser and chemical immersion, metal plates were processed to create wettability patterns consisting of superhydrophobic and superhydrophilic regions. Water tunnel experiments were conducted to observe the behavior of air bubbles over different wettability patterns. The results show that surface wettability can be used to control the size and spatial distribution of air bubbles, potentially enhancing the energy cost-benefit of drag reduction methods in the marine industry. Small circular bubbles were retained over untreated and hydrophilic surfaces, while immediate bubble coalescence was observed over superhydrophobic surfaces.

Computational fluid dynamics (CFD) modeling was also performed to verify and further understand the role of surface wettability. The results demonstrate the potential of laser-based surface wettability modification as a solution for improving the control of air bubble behavior in large-scale applications. This research provides insights into the feasibility of laser-based surface wettability modification as a novel approach for controlling air bubble behavior in water flows and improving the efficiency of drag reduction methods.