Dynamic Stall over a Pitching Natural-Laminar-Flow Airfoil

Abstract

High-fidelity large-eddy simulations are performed to study the unsteady boundary layer sensitivity of a natural-laminar-flow airfoil (NLF-0414) undergoing dynamic stall in comparison to two traditional airfoil sections (NACA 0012 and SD 7003). In this work, the natural-laminar-flow airfoil at and pitches with a constant nondimensional rate of from an initial incidence angle of 4 deg to angles of attack beyond the onset of dynamic stall. It is found that the transition of the NLF-0414’s unsteady boundary layer during the pitchup is much more abrupt than the standard airfoil sections before the formation of the laminar separation bubble. Once the laminar separation bubble is established near the leading edge, the overall dynamic stall process of the NLF-0414 evolves very similarly to that of the SD 7003 and the NACA 0012. Minor differences are observed in the formation of the turbulent separation vortex near the trailing edge and convection of the dynamic stall and shear-layer vortices. The dynamic stall of the NLF-0414 airfoil more closely resembles that of the SD 7003 and the NACA 0012 at reduced Reynolds numbers, suggesting that the extended laminar flow acts to delay Reynolds number effects of traditional airfoil profiles.