UCLA

Superhydrophobic (SHPo) surfaces coated on the hulls of marine vessels are capable of passively producing drag reduction. This gives SHPo technology an exciting opportunity to dramatically reduce the fuel costs and pollutant emissions of large ships or increase the top speeds of racing boats. While the performance of SHPo surfaces in laminar flow is now well understood and predictable, their performance in turbulent conditions is still faced with lack of knowledges and many uncertainties. Furthermore, most experimental studies in turbulent flow have been conducted in laboratory conditions, which often produce over-optimistic results when compared to the open-water environment in the field conditions. This thesis creates a convenient method to test SHPo surfaces covering the hull of a watercraft in realistic conditions, by comparing the speeds of two identical model boats, whose hulls are attached with smooth or SHPo surfaces, under fully turbulent flows in the open water of a lake. With the molded SHPo samples the UCLA Micro & Nano Manufacturing Laboratory is developing in mind, this thesis aims to confirm that the boat operator can reliably drive the developed model boats at the same speed for a given throttle. At 75% throttle, the two model boats both travel steadily at 1.9�0.2 m/s with Rex = (7.2�0.9)�105, yielding a speed difference of 0%. At 100% throttle, the two boats travel steadily at 10.3�0.2 m/s with Rex = (3.6�0.2)�106 and 10.5�0.2 m/s with Rex = (3.7�0.2)�106, yielding a speed difference of 2%. Additionally, this research takes the first steps of considering the real-world potential of SHPo drag reduction by estimating the cost and value of the molded SHPo surfaces as a commercial product. The return on investment (ROI) for implementing SHPo surfaces on a cargo ship hull is estimated to be between 338% and 562%, depending on the material used to fabricate the SHPo surfaces.