Numerical flow analysis of vertical axis wind turbines with morphing airfoils

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A morphing airfoil has the ability to change its geometry in order to optimize the aerodynamic forces for a specific operating flow condition. This technology can be very effective when applied to vertical axis wind turbines (VAWTs), because the blades of these turbines encounter different angles of attack as they rotate. Variable pitch technology has been investigated in the past for the same purpose, but it is mechanically more difficult to implement and offers less flexibility than morphing airfoils. Control of the morphing shape is easier to implement and has a greater potential for optimizing the instantaneous torque generated by each blade. The proposed research will investigate morphing airfoils that change the geometry of the trailing edge, and therefore the camber line of the airfoil. Changing the geometry can be used to prevent dynamic stall, to increase power extraction in the leeward portion of the rotation, to distribute the load over the rotation cycle or as a breaking system. This research plan proposes an approach to understand the influence of morphing the geometry, in particular during dynamics stall. It also includes the development of a computational tool for predicting the power extracted by a VAWT for different morphing strategies.****Computational Fluid Dynamics techniques are powerful tools to simulate fluid flow around complex geometries. Although computationally expensive, Large Eddy Simulation (LES) is a necessary model to study complex unsteady flows such as the one occurring during dynamic stall. Over the years, an in-house LES-CFD code has been developed by Prof. Paraschivoiu's research group, and validated for VAWTs. The objective of the current proposal is the further development of the numerical algorithms and software, and to use these to analyze flow over morphing wind turbine blades, as well as dynamic stall. Other important aspects of the research will be the investigation of an improved LES model and addition of new acceleration techniques that will reduce the significant computation time that LES typically requires.*********