Experimental and CFD modelling of a vortex-driven turbine

Abstract

Much research has been conducted into fluid-structure interaction phenomena as methods of generating clean power, but there is a gap in knowledge regarding horizontal axis wind turbines directly powered by vortices attaching to or shedding from radial blades. This study provides two outputs; it examines the characteristics of a novel vortex-powered horizontal axis wind turbine with various blade configurations using both CFD and wind tunnel testing methods, and it provides information on how the CFD model performs in a turbulence-dominated flow scenario. Analyzing the turbine blades with the ANSYS Fluent simulation package, the peak efficiency, Cₚ, occurred at a tip speed ratio, Cₛ, of approximately 0.2 for 50.44mm cross section blades, and 0.4 for 25.28mm cross section blades. These results reasonably agreed with validation trials performed in a wind tunnel where peak Cₚ occurred at Cₛ of approximately 0.22 for 50.44mm cross section blades, and 0.35 for 25.28mm cross section blades. However, the magnitude of the values returned in the CFD simulations were significantly lower than those measured in the wind tunnel trials, indicating that the CFD turbulence model may not be accurate for this turbulence-dominated simulation. Turbine efficiency did not approach the Betz limit, being <1% efficient in all cases. This indicates that such turbines are not a practical technology. However similar turbines may be useful in rudimentary applications, and knowledge of the effect may be applicable in similar geometry, such as radially spoked structures operating in open flows. The comparison of the CFD model output and the experimental data indicates that the CFD closely maps the data trends observed in the experiments but differs in absolute values. A number of possible improvements in the CFD modelling are suggested tor reduce this gap in absolute values.