Passive control of marine hydrokinetic turbine blades

Marine hydrokinetic (MHK) turbine blades are generally constructed from fiber reinforced polymer composites and are subject to large, highly dynamic fluid forces. The bend-twist deformation coupling behavior of these materials can be hydroelastically tailored to improve system performance over the expected life of the turbine by way of rapid, passive pitch control that can increase lifetime power generation, reduce hydrodynamic instabilities, and improve load shedding and structural performance. There are practical concerns, however, that make the design of these devices complex. Constraints on system components such as the rated power of the generator system, maximum rotational speed, or material degradation can affect the extent to which passive control can enhance performance. Using a previously validated boundary element method-finite element method solver, this paper examines the capabilities of passive pitch adaptation under both instantaneous and long-term variable amplitude loading to better describe potential benefits while considering practical design and operational restrictions.