Boundary Layer Transition Measurements on NLF(1)-0416 Airfoil using Infrared Thermography and Comparisons with 2D RANS Predictions

This study presents an experimental and numerical investigation on the boundary layer transition characteristics of the NLF(1)-0416 airfoil. The experiments are conducted in the large-scale subsonic wind tunnel of METU Center for Wind Energy Research (RUZGEM) using a 2D airfoil test model with 0.9 m chord and 2.5 m span. The experimental work includes Infrared Thermography (IRT) measurements for the transition location, while the numerical study is based on the 2D RANS simulations using two different CFD solvers with different turbulence and transition models as well as XFOIL predictions. The current IRT measurement results are consistent with previous transition measurement data from the NASA LTPT, obtained using oil flow and microphones. Results show that simulations with different transition models generally provide better agreement with experimental data compared to fully turbulent models in predicting lift, drag, and lift-to-drag ratio, with the GEKO model and XFOIL showing the best performance at Re = 2 x 106. The predicted transition locations are generally more downstream towards the trailing edge at any given angle of attack when compared with the NASA LTPT dataset and similarly with the new METU RUZGEM IRT dataset.