Laminar Separation Bubble and Flow Topology of NACA 0015 at Low Reynolds Number

Abstract

The development of sophisticated unmanned aerial vehicles and wind turbines for daily activities has triggered the interest of researchers. However, understanding the flow phenomena is a strenuous task due to the complexity of the flow field. The engaging topic calls for more research at low Reynolds numbers. The computational investigations on a two-dimensional (2D) airfoil are presented in this paper. Numerical simulation of unsteady, laminar-turbulent flow around NACA 0015 airfoil was performed by using shear-stress transport (SST) model at relatively low Reynolds number (8.4 × 104 to 1.7 × 105) and moderate angles of attack (0 ≤ α ≤ 6). In general, on the suction side, with increasing Reynolds number and angles of attack, separation, and reattachment point shifts upstream and concurrently shrinking the size of the laminar bubble. However, On the pressure side, the laminar bubble is seen to move toward the trailing edge at the relatively same size as the angle of attack increases. Moreover, the variations in the angle of attack have more influence on the laminar separation bubble characteristics as compared to the Reynolds number. The reattachment points were barely observed for the range of the angles of attack studied. At very high angles of attack, it is recommended to simulate the flow field using large eddy simulation or direct numerical simulation since the flow is considered three-dimensional and detached from the surface thus forming a complex phenomenon.