Update on marine turbine research at the Atlantic Marine Energy Center – University of New Hampshire

Axial-flow turbines (AFTs) and cross-flow turbines (CFTs) are being investigated for marine energy applications, with studies conducted at a 1-m lab scale a 3-m open-water scale. CFTs, which are inherently unsteady fluid energy conversion devices due to their operating principle, are shown to be sensitive to surface roughness. CFT performance can be correlated by surface roughness viscous heights calculated from operating conditions, which can indicate the presence of rough wall boundary layers. The effects of varying foil thickness and foil trailing edge thickness on the performance of CFTs were investigated for a range of symmetrical NACA foils. Thicker foils resulted in higher power coefficients at slightly lower tip speed ratios, while thicker trailing edges resulted in decreased power coefficients. Continuous fiberoptic blade strain measurements on operating CFTs provided insight into CFT design choices regarding blade materials and blade supports, while foil-gauge blade strain measurements on a CFT blade in a real tidal flow provided dynamic loading data that enabled a fatigue analysis. Work with AFT reference models in the lab and open water is ongoing, including a new AFT towing tank test bed and the highly instrumented DOE Open-Source Tidal Energy Converter (OSTEC) turbine, which is being readied for deployment at the AMEC-UNH Tidal Energy Test Site.