Can water flow over a surface with less friction, almost as if it is sliding on air? This study explores that question by studying superhydrophobic surfaces—water-repellent surfaces inspired by lotus leaves and aquatic organisms. These surfaces can trap tiny pockets of air and reduce the contact between water and solid walls, offering a promising way to reduce drag in marine, microfluidic, and biomedical applications.

To study this phenomenon, we develop a high-resolution optical measurement system for micro-PIV experiments. The system combines a custom water tunnel, laser illumination, fluorescent tracer particles, high-magnification optics, and a double-shutter high-speed camera. This setup allows us to observe near-wall flow structures at submicron-scale resolution, especially within the thin viscous layer where drag is generated.

The study also uses a Single-Pixel Ensemble Average Correlation algorithm to improve PIV resolution beyond conventional interrogation-window methods. By analyzing particle motion at the pixel level over many image pairs, the algorithm can extract mean velocity, velocity fluctuations, Reynolds stresses, and slip behavior with very high spatial resolution. This helps us understand how superhydrophobic surfaces interact with turbulent flow and how they can be designed for more stable drag reduction.

Flowing water and wind contain energy that can be captured not only by traditional turbines, but also through structural vibration. This research studies vortex-induced vibration (VIV), a fluid–structure interaction phenomenon in which alternating vortices shed from a cylinder and cause it to oscillate. By converting this motion into electrical energy, VIV energy harvesters offer a simple, low-cost, and environmentally friendly approach for harvesting energy from low-speed water currents, tidal flows, low-altitude wind, and remote-area fluid flows.

This research focuses on finite-span pivoted cylinders, which are closer to practical VIV energy harvesters than ideal two-dimensional cylinder models. Using water-channel experiments, motion tracking, digital particle image velocimetry, and computational fluid dynamics simulations, the study examines how cylinder geometry, mass properties, aspect ratio, and tip effects influence vibration amplitude, wake structure, and energy-harvesting performance.

Another important goal of this research is to understand how multiple VIV energy harvesters interact when arranged in close formation. The wake generated by upstream cylinders may enhance the vibration of downstream cylinders, potentially increasing the total power output within a compact area. By studying both single cylinders and cylinder arrays, this research aims to reveal the flow physics behind VIV-based energy harvesting and support the design of high-density renewable-energy harvester systems.