Hydrodynamic analysis models for the design of Darrieus-type vertical-axis marine current turbines

Abstract

This work reviews hydrodynamic analysis models developed for the design of Darrieus-type vertical axis marine current turbines, with particular emphasis on the prediction of hydrodynamic rotor performance, as well as their suitability for aiding the optimization process, either directly, or as a fast filter of potential blade profiles. In order to improve the performance of a marine current turbine it is necessary accurately to model the flow passing the turbine’s blades. Several types of models exist for Darrieus-type turbines, from momentum-based streamtube models to complex computational fluids dynamics (CFD) simulations. With continuously varying large angles of attack on the blades, the main issue is accurate prediction of the flow field around the rotor and thus its loads and torque. This is further complicated by the significant inherent unsteady hydrodynamic characteristics and potential for dynamic stall. Comparisons of the analytical results with experimental data are presented to compare these different models and thus illustrate their areas of suitability in this context. In conclusion, vertical axis machines have the potential of high power capture compared with that of their horizontal counterparts but this will depend on blade profile and design configuration, solidity, and tip speed ratio. None of the existing theoretical methods really captures the actual performance of the machines except for detailed CFD simulations, which are inevitably computational time intensive.