Proper Orthogonal Decomposition Analysis of Flow Characteristics of an Airfoil with Leading Edge Protuberances

A numerical investigation of the aerodynamic performances and flow mechanisms of an airfoil with leading-edge protuberances is presented within stall region at a Reynolds number of . In detail, a large-eddy simulation has been conducted and then validated through quantitative comparisons with previous experimental and numerical investigations. Based on the numerical results, a proper orthogonal decomposition (POD) analysis has been carried out. The flow control mechanisms within stall regime and physical backgrounds of corresponding POD modes have been uncovered from the view of flow energy. It has been found that the improved aerodynamic characteristics of modified airfoil might be attributed to different flow mechanisms at peaks and troughs, including spanwise momentum transfer process and flow transition within laminar separation bubble. In addition, the fluctuating characteristics of airfoil flow field have also been investigated. Consequently, it has been found that the Karman vortices dominate the rear wake of the smooth airfoil and the first four POD modes are closely related with the shedding process. In contrast, the corresponding vortex shedding process is suppressed by the modified airfoil according to the results of POD analysis.