Lagrangian Analysis of 2D Airfoils

Velocity fields of flows over NACA 0012 airfoil and Eppler 423 airfoil with different angles of attack are obtained by direct numerical simulation. Attracting LCSs (unstable manifolds) are extracted by calculating backward finite-time Lyapunov exponent (FTLE) fields through integrating the trajectories of a uniform mesh of fluid particles backward in time. We also utilize Lagrangian-averaged vorticity deviation (LAVD) method to acquire coherent vortex boundaries and explore their evolution.

NACA 0012 airfoil, Re=1000, AOA=10 deg, backward FTLE field.

NACA 0012 airfoil, Re=1000, AOA=15 deg, backward FTLE field.

NACA 0012 airfoil, Re=1000, AOA=20 deg, backward FTLE field.