Numerical Modeling and Investigation of Rotary Wing Aerodynamics using Free Vortex Wake Methods

Date

2026-1-07

Author

Öztürk Ergin, İldeniz

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Accurate predictions and understanding of rotary wing aerodynamics for helicopters and wind turbines are important for efficient transportation and clean energy generation. It is also essential to predict the aerodynamic loads and performance of rotors accurately with low computational cost during design, usage, and control of such rotor systems. In this thesis study, an in-house parallel unsteady three-dimensional rotor aerodynamics code written in C and OpenMP and called as AeroROTOR has been developed, which is based on the Blade Element Theory (BET) and Lifting Line (LL) theory with two different free wake methods: Free Vortex Wake (FVW) model and free Vortex Ring Wake (VRW) model. The aerodynamic performance and wake characteristics of both helicopter and wind turbine rotors under different conditions are investigated using both free wake models, and the comparative evaluation and capabilities of the models are presented. The results highlight the potential of the three-dimensional free VRW model for rapid aerodynamic predictions of rotary-wing systems. The simulations for the HVAB helicopter rotor model are performed as a test and validation case for different flight conditions in hover and vertical descent with Vortex Ring State (VRS) condition, considering both steady and unsteady wake flow conditions. Then, the simulations for the UNAFLOW wind turbine rotor as a test and validation case are performed in steady axial and yaw wind conditions, and also with unsteady sway motions of the rotor again in both axial and yaw wind conditions. After showing the applicability of the VRW model with detailed comparisons with the FVW model, the helical tip vortex geometries are obtained by interpolating the ring points from the solutions of the wind turbine rotor with the VRW model. The helical wake solutions are then used to construct a new prescribed wake model by fitting simplified analytical expressions for the tip vortex trajectories as functions of tip-speed ratio and yaw angle. The resulting new prescribed wake model successfully reproduces the wake geometry in steady axial and yaw wind conditions, enabling efficient and accurate calculations of induced velocities and aerodynamic loads with negligible loss of accuracy, thus offering a practical and computationally efficient alternative for rotor aerodynamic performance predictions.

Subject Keywords

Wind Turbine Rotor Aerodynamics, Helicopter Rotor Aerodynamics, Free Vortex Wake Model, Vortex Ring Wake Model, Prescribed Wake Model

URI

https://hdl.handle.net/11511/118422

Collections

Graduate School of Natural and Applied Sciences, Thesis