Research Article
Ilyas Karasu, M. Serdar Gen
Abstract
This study is a numerical investigation on laminar separation bubble over a NACA2415 aerofoil at low Reynolds numbers and various angles of attack. The numerical results were compared with the experimental results of our previous study. Oil flow visualization technique, an external three-component balance system and pressure measurements were used for the experiments. In the experimental results, stall angle was 12°, 13° and 15° for Re=0.5x105, Re=1x105 and Re=3x105, respectively. The flow separation, reattachment and forming the laminar separation bubble were clearly seen by using the aforementioned experimental methods. It was indicated that the point of separation moved towards the leading edge as the angle of attack increased. Moreover, the flow visualization results showed that as the angle of attack increased further, the bubble burst and the separated flow was not able to reattach to the aerofoil surface, which indicated stall. In the numerical results, the transition models are shown to accurately predict the location of the separation bubble experimentally determined at lower angles of attack. Furthermore, the numerical prediction using the transition models are more successful than the turbulence model suitable for low Re number flows.