Özge Sinem Özçakmak

Transition Modeling for Wind Turbine Rotors/TRMOD

The main objective of the project is to validate and improve the existing laminar/turbulent transition model in DTU in-house CFD EllipSys code for modern wind turbine applications considering the atmospheric inflow turbulence and roughness effects in comparison with the DANAERO experiments.

Background

As the wind turbine technology develops and the size of modern wind turbines grows steadily, the design process becomes highly dependent on the availability of accurate aerodynamic prediction tools. The most widespread approach is to model the entire boundary layer on airfoils/ blade section by fully turbulent calculations, ignoring the transitional process from laminar to turbulent flow on the boundary layer. However, as found out in this PhD project, the transitional flow can occupy a significance percentage of the chord. Therefore, accurate prediction of the laminar-turbulent transition process is critical for development of the design and aerodynamic prediction tools, particularly for the high Reynolds numbers experienced by modern wind turbines.

Method & Outcomes

High-frequency microphone measurements from 2-D wind tunnel and 3-D field experiments of the DANAERO project are used to analyze the transition characteristics of the airfoil and wind turbine blade sections. An autonomous method is established for transition detection on airfoil sections by the data from the high frequency microphone measurements. This method can be applied to all future experimental data obtained from high-frequency chordwise measurements.

Further, the inflow turbulence and surface roughness effects are analyzed from the experimental and numerical results. Inflow turbulence and rotational effects are analyzed by comparing the transition behavior of the 2-D airfoil from the wind tunnel and 3-D wind turbine blade section from the field measurements. The experimental results are compared with the XFOIL and EllipSyS computations for different amplification factors corresponding to several turbulence intensities of the incoming flow.

The last step of the projects is to validate and improve the existing transition models (Drela-Giles, correlation based and the bypass model) in the EllipSys code.  By the improved model for the laminar-turbulent transition detection, the performance, design and power production of the wind turbines can be estimated more accurately.

Contact

Özge Sinem Özçakmak
PhD student
DTU Wind Energy
+4593 51 15 65