EXPERIMENTAL AND NUMERICAL INVESTIGATION OF BOUNDARY LAYER TRANSITION ON AIRFOILS

Date

2025-7-7

Author

Kalaycı, Ahmet Çağdaş

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Accurate determination of boundary layer transition location is critical for engineering applications such as natural laminar flow wing design and wind-turbine blade optimization. Despite advancements in transition prediction methods, further improvements in accuracy remain crucial. This study investigates boundary layer transition behavior on airfoils through experimental and numerical methods, focusing on two main geometries: the natural laminar flow airfoil NLF(1)-0416 and the DU00-W-212 wind-turbine airfoil. The NLF(1)-0416, designed in the early 1980s with 16% thickness, was previously tested at NASA Langley Low Turbulence Pressure Tunnel (LTPT) across a Reynolds number range of 1x10^6 to 9x10^6 and Mach numbers between 0.1 and 0.4, using oil flow visualization and microphone-based transition detection. In this thesis, boundary layer transition is detected using infrared thermography in the large-scale wind tunnel at the METU Center for Wind Energy Research (RÜZGEM), which features a 2.5 m × 2.5 m test section and accommodates a full-span model with 0.9 m chord and 2.5 m span, tested under Reynolds numbers from 1x10^6 to 4x10^6. Numerical simulations using RANS models, along with linear stability-based predictions using XFOIL, are performed to support the experimental findings. For the DU00-W-212 airfoil, numerical simulations are conducted, validated by earlier experiments carried out at RÜZGEM. Comparative analyses between experimental results, numerical predictions, and existing literature confirm that infrared thermography effectively captures transition behavior, as current IRT measurements align well with prior datasets. Transition models provide close agreement with experiments, particularly the SST-LM and GEKO-gamma with accurate predictions of transition locations and aerodynamic coefficients.

Subject Keywords

Transition, Boundary-layer, Infrared, Airfoil, Turbulence

URI

https://hdl.handle.net/11511/115444

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Graduate School of Natural and Applied Sciences, Thesis