Enhancement of Free Vortex Filament Method for Aerodynamic Loads on Rotor Blades

Abstract

The aerodynamics of a wind turbine is governed by the flow around the rotor, where the prediction of air loads on rotor blades in different operational conditions and its relation to rotor structural dynamics is one of the most important challenges in wind turbine rotor blade design. Because of the unsteady flow field around wind turbine blades, prediction of aerodynamic loads with high level of accuracy is difficult and increases the uncertainty of load calculations. An in-house vortex lattice free wake (VLFW) code, based on the inviscid, incompressible, and irrotational flow (potential flow), was developed to study the aerodynamic loads. Since it is based on the potential flow, it cannot be used to predict viscous phenomena such as drag and boundary layer separation. Therefore, it must be coupled to tabulated airfoil data to take the viscosity effects into account. Additionally, a dynamic approach must be introduced to modify the aerodynamic coefficients for unsteady operating conditions. This approach, which is called dynamic stall, adjusts the lift, the drag, and the moment coefficients for each blade element on the basis of the two-dimensional (2D) static airfoil data together with the correction for separated flow. Two different turbines, NREL and MEXICO, are used in the simulations. Predicted normal and tangential forces using the VLFW method are compared with the blade element momentum (BEM) method, the GENUVP code, and the MEXICO wind tunnel measurements. The results show that coupling to the 2D static airfoil data improves the load and power predictions while employing the dynamic stall model to take the time-varying operating conditions into consideration is crucial.

Linear Computational Fluid Dynamic Analysis of Dynamic Ground Effect of a Wing in Sink and Flare Maneuvers

“…(18) and (19), respectively, and the values obtained using ATHENA, PAN AIR and CMARC presented in Ref. [12].…”

“…Abedi 18 pointed out that different numerical schemes may be used to solve Eq. (17) such as the explicit Euler method, the implicit method, the Adams-Bashforth method, and the predictor-corrector method, but in terms of accuracy, stability and computational efficiency, the best is the predictor-corrector scheme, which was selected in this case.…”

Numerical Predictions of Propeller-Wing Interaction Induced Noise in Cruise and Off-Design Conditions

“…The aeroacoustic component is described in Section 2.3.2. While the details of the GENUVP aerodynamic code are detailed in references [40], [45]- [47], the main aspects of its formulation are presented below.…”

“…While the SmartRotor code has been extensively validated for rotorcraft and horizontal-axis wind turbines [40], [41], [46], [50], it was necessary to validate it for propellers with high axial flow speeds and rotation speeds. This validation further served to validate the changes made to the code to handle spanwise varying airfoils.…”

Dimensional Analysis in Power Predicting of a Real Scale Wind Turbine Based on Wind Tunnel Torque Measurement of Small Scaled Models

“…2 of 12 Kesler made a comparison between the experimental thrust and propeller thrust predicted by Prandtl's lifting line theory. Abedi developed a vortex filament method for aerodynamic loads on rotor blades, and de Oliveira et al investigated how does the presence of a body effect to the performance of an actuator disk [10][11][12].…”