Microbubble Drag Reduction Demonstration

Cortana Corporation, ARL/PSU, and NAVATEK, propose to address the feasibility of performing a large-scale, seaborne demonstration of microbubble drag reduction (MBDR). A Cortana-led team has successfully demonstrated that a well-designed ejector and acarefully selected ejectant can increase the effectiveness of polymer ejection by a factor of two and reduce historical additive expenditure rates by about two orders of magnitude. We propose to extend this to microbubble drag reduction to determine thescale-up and seawater effects on bubble and ejection parameters, as well as on the efficacy and robustness of the MBDR technique. We will evaluate/select a bubble generator that can provide narrow distributions between 20-400 microns. Using our unique,non-disruptive ejector design, we will investigate effects of bubble size, concentration, and location on drag reduction. The benefits of combining MBDR with polymer drag reduction in terms of systems efficiency and risk mitigation will be examined. Wewill examine the feasibility of quantifying MBDR persistence and effects of full-scale platform operation during the Phase II work by identifying potential test platforms and the instrument package necessary to develop a database of performance. The PhaseI final product will be a detailed design of the at-sea test system.The technology to be demonstrated as a result of the successful completion of the proposed STTR research will be most relevant for new hull forms that have low wave drag. Hence, weenvision the initial market to be the