Thickness-induced wake transition and onset of new vortex modes in low-Re airfoils

This work presents a detailed computational analysis of wake transition and aerodynamic performance for the thin NACA0005 airfoil at low and moderate Reynolds numbers. Simulations are carried out for Re=500–6000 for fixed angles of attack (α=10° and α=13°). This extends the previous study, where a new vortex mode (k-mode was discovered for Re=5000. Here, the new variants of 4i and K-modes are unveiled. Mode-4i and its variant 4i-I, specific to the thin airfoil, dominated at moderate Reynolds numbers and higher angles of attack, while k-mode and k-mode-I appeared near α=10° for Re≥5000. Computational convergence is carried out by computing the grid convergence index (GCI). Global aerodynamic coefficients are also calculated. An optimal aerodynamic performance is observed near the onset of organized vortex dynamics. With changes in Reynolds number and angle of attack, visualizations of flow structure, such as vorticity, streamlines, and phase portraits, revealed rich diversity and subtle differences in wake topology. This study reveals that new vortex modes, which do not appear in higher thickness airfoils, are highly associated with lower thickness airfoils and Reynolds numbers. Thus, the study establishes airfoil thickness as a key parameter governing wake dynamics and mode transitions in low-Reynolds-number flows. It highlights the strong influence of thickness on wake behavior and flow instability mechanisms.