Dynamics of Laminar Separation Bubbles Over NACA 0012 Airfoil

This study investigates the effects of angle of attack on flow dynamics around a NACA 0012 airfoil, with particular focus on the formation, size, and behavior of the leading-edge laminar separation bubble (LSB). Post-transitional conditions (���� = 500,000) with moderate compressibility effects are considered (�� = 0.5). Using scale-resolved simulations, we examine flow characteristics at angles of attack, �� = 4°, 8°, and �� = 12°, each highlighting distinct flow phenomena. At 4°, the flow remains attached without any LSB signature. At 8°, a small, stable LSB forms near the leading edge, indicating a moderate adverse pressure gradient. At 12°, the LSB exhibits a state-switching phenomenon, alternating between attached, transitional, and vortex-shedding phases. At high angles of attack, this state-switching behavior causes cyclic oscillations in lift and drag coefficients, which affects aerodynamic performance. Compressibility effects are also addressed, which highlight the formation of upstream compression waves at key flow stages that affect the LSB’s stability and structure. Frequency analysis identifies dominant oscillation modes associated with bubble state switching frequency, shear layer instability, bubble pitching, and vortex shedding, revealing information about unsteady flow dynamics. The findings are consistent with previous research on LSB behavior, emphasizing the importance of understanding these phenomena for optimizing airfoil performance across various operational regimes.