Aerodynamic modeling of horizontal axis wind turbines

The paper presents the development of a vortex lattice aerodynamic modeling routine for SAMCEF for Wind Turbine (S4WT). S4WT is a general-purpose commercial code for wind turbine design and analysis. At present, it uses blade element momentum theory (BEM) for the estimation of the aerodynamics loads on HAWT rotor blades. BEM is a simple aerodynamic modeling approach that is currently used by several software packages for wind turbine design (as well as other rotor-based applications). It is based on the assumption that the flow can be treated as quasi-steady and quasi-2D, so that the steady, 2D aerodynamic loads acting on a strip of a rotor blade are used to estimate the instantaneous unsteady, 3D loads acting on a complete blade. This approach ignores the effect of the unsteady wake of the blades on the aerodynamic loads and simplifies the true 3D load distribution over the blades.
A higher fidelity calculation of the time varying aerodynamic forces and moments acting on the blades is the main focus of this work. A good compromise between speed and accuracy to calculate these forces is the 3D unsteady vortex lattice method with a freely deforming wake. The vortex lattice results are compared to the BEM results from S4WT. The ultimate aim is to integrate the vortex lattice calculation as a subroutine in S4WT in order to calculate the unsteady aerodynamic forces on the rotor blades during the design process. This new method in S4WT will provide more representative results to the user, which can be very important for designing a more efficient wind turbine.