Investigation of transition flow over S809 airfoil using infrared thermography and numerical methods

This thesis presents the results of an experimental and numerical study that investigates the detection of boundary layer transitional flow using infrared thermography and Computational Fluid Dynamics analysis. The experimental part of this thesis involves wind tunnel experiments conducted in METUWIND large-scale multi-purpose wind tunnel. S809 laminar airfoil was used as a test object and experiments were conducted in the boundary layer test section (TS2) of METUWIND. Experiments were performed for different Reynolds numbers at 0° angle of attack and different angles of attack at a Reynolds number of 5×10^5. Thus, separate effects of Reynolds number and angle of attack on the variation of the separation, transition onset, and reattachment points on the chordwise position of the airfoil were examined. In addition, the effect transition strip was observed experimentally using a vortex generator. In the numerical part of the thesis, CFD simulations of the experimental cases were carried out. Effects of different turbulence transition models (k-ω-γ transition model, transition k-kl-ω model and transition SST model) were examined and implemented to the cases of the thesis using a commercial software. Afterwards, transition models were compared among themselves and with the standard k-ε turbulence model to highlight the difference. The experimental process and results were compared and discussed with the results of numerical methods. The chordwise positions of the separation, transition, and reattachment points were successfully determined using the IR thermography method and CFD analyses, and the results were consistent. As the Reynolds number changes within the range of 5×10^5, 6×10^5 and 7×10^5 for 0° angle of attack, the chordwise position of the transition onset point did not show significant variations because of the low variation of the Reynolds number. As the angle of attach changes within the range of 0°, 3°, 6° and 9° for 5×10^5 Reynolds number, the chordwise position of the transition onset point approached the leading edge of the airfoil.