Vortex generators (VGs) are known to delay separation and stall, allowing the design of airfoils with larger stall margins, particularly for thick airfoil sections in the inboard and midboard regions of modern slender wind turbine blades. Including VG effects in blade design studies requires accurate VG models for fast lower-order techniques, like integral boundary layer (IBL) methods. Previous VG models for IBL methods have used engineering approaches tuned on airfoil aerodynamic data. The accuracy of these models depends on the availability of wind tunnel aerodynamic polar datasets for tuning, which are limited and time-consuming to expand for the relevant wind conditions, airfoil sections, and VG configurations being used in continuously growing wind turbine blades. This work proposes a VG model using IBL equations derived from flat-plate boundary layers under the influence of VGs. The new VG model empirically models the shape factor of the boundary layer and the viscous dissipation coefficient in the IBL framework to account for the additional momentum and dissipation in the boundary layer mean flow due to VGs. The model is developed from a wide range of flat-plate boundary layers and VGs to account for variations in VG vane size and placement on the turbulent boundary layer development influencing the airfoil aerodynamic characteristics. The new VG model, called RFOILVogue, is implemented in an in-house code RFOIL, an improvement over XFOIL, and validated with computational fluid dynamics (CFD) data and wind tunnel measurements of flat plates and airfoil sections equipped with VGs. Since it is derived from vortex dynamics in turbulent boundary layers, RFOILVogue better predicts both airfoil performance characteristics, such as positive stall angle, maximum lift, and drag, and boundary layer flow parameters, such as the separation location, compared to the existing tuned VG models. The VG model still suffers from some inherent drawbacks of reduced-order models like RFOIL, and future research directions for thick airfoils are proposed to overcome these drawbacks in VG modelling.

As the demand for renewable energy increases, wind turbine rotors will become larger with slender blades. Vortex Generators (VGs) are used for passive flow control to avoid flow separation and reduce unsteady loading on the thick root section of slender blades due to their simplicity, inexpensiveness, and the ability to retrofit them to blades. Aerodynamic load calculations for VGs involve long experimental campaigns or resource intensive CFD calculations. Due to their inherent time-intensive nature aeroelastic optimisation and design tools prefer to use simplified but accurate analysis tools for aerodynamic load calculations of clean airfoils. One such class of tools are viscous-inviscid interaction solvers that use Integral Boundary Layer (IBL) methods for viscous calculations in the boundary layer coupled with an inviscid solver for the rest of the domain. The most popular example of this tool is XFOIL. An engineering model for VGs in IBL methods has previously been developed and implemented in XFOIL. In this research, the model parameters are tuned for implementation in another tool RFOIL based on XFOIL. RFOIL has been developed for accurate and robust analysis of wind turbine airfoils with improvements for thick airfoils and rotational corrections. The aerodynamic performance predicted the VG model in both XFOIL and RFOIL is then validated with an extensive database of airfoil data consisting of airfoils between 21% to 60% thickness, as well as Reynolds numbers between 1 million to 14 million, equipped with and without VGs. Finally, the computation time for the VG model is compared with that for a clean airfoil analysis in the same viscous-inviscid interaction solvers RFOIL and XFOIL. The investigation provides an overview of the usability of the engineering model in airfoil design methodologies in the wind turbine industry.