Outline of project description:
The proposed research will investigate the effect of unsteady onset flow on the blade loads of horizontal-axis tidal turbines. Specifically it will aim to quantify the effect of added mass and dynamic inflow, which are two components of the force which arise when the flow is accelerating. Literature1 has indicated that the total added mass component can be an order of magnitude greater than the structural mass of the rotor, and hence can have a significant influence on the blade dynamic loads. There is a need to gain greater confidence in accounting for such an effect in analytical models for load prediction purposes. Recently Mr. Milne has conducted a set of experimental trials on an instrumented scale model tidal turbine, where the blade root bending moment response was measured under a range of unsteady onset flow conditions. The benefit of using the blade root bending moment over the thrust force as in the case of the aforementioned study1, is that the effect can be measured directly at the blade without the influence of the hub and shaft. In this research it is proposed to compare these experimental measurements with two numerical models; one based on a dynamic blade element momentum theory and commonly implemented in industrial codes; and an alternative, higher order, vortex model which incorporates a lifting surface technique. Between these two models, the added mass and dynamic inflow effect are treated differently, the former using an empirical correction, with the latter model inherently including the effect. It is envisaged to quantify the magnitude of any difference between these models as a function of the degree of unsteadiness present in the onset flow.
- Contact information
- Duncan McNae (Imperial College, London, United Kingdom)
Ian Milne (The University of Auckland, New Zealand)
- Contact email
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