The onset of leading-edge stall on stationary, smooth, thin, two-dimensional airfoils with various blunt nose shapes of the form $y=\pm k{\left(ax\right)}^{\frac{1}{a}}$ (where $a\ge 2$ and $k$ is a constant) at moderately high chord Reynolds numbers (Re) is studied. A reduced-order, multiple-scale model problem is developed and is complimented by direct numerical simulations for low Re and numerical computations using a Reynolds-averaged Navier-Stokes (RANS) flow solver for moderately high Re. The asymptotic theory results in a description of the flow around a thin airfoil composed of an outer region about a majority of the airfoil's chord, and an inner region, surrounding the nose, that match each other. The classical thin airfoil theory dominates the outer region. The coordinates in the inner region are scaled with respect to a characteristic length of the nose and the Reynolds number is modified $\left({\text{Re}}_M\right)$ in order to account for the acute velocity changes in the inner region, where both near-stagnation and high-suction areas appear. The far field of the inner region is described by a symmetric effect due to nose shape and an asymmetric effect with a lumped circulation parameter $\left(\tilde{A}\right)$ due to angle of attack and camber. The inner flow problem is solved numerically using a transformation from the physical domain to a computational domain and a second-order finite-difference scheme for integrating the vorticity and stream function. The computed results demonstrate numerical convergence with mesh refinement. The inner region solutions reveal, for various values of $a$, the nature of the flow around the nose and the inception of global separation and stall as $\tilde{A}$ increases above a certain critical value, ${\tilde{A}}_s$, at fixed $a$ and ${\text{Re}}_M$. For $a\ge 2$, the value of ${\tilde{A}}_s$ decreases with ${\text{Re}}_M$ up to a limit value, ${\text{Re}}_{M,\lim }$, above which unsteady effects increase ${\tilde{A}}_s$ and delay the onset of stall. For airfoils with the same thickness ratio and position of maximum thickness, global stall is delayed to higher angles of attack as $a$ is increased above 2. The results of the RANS computations for various $a$ show matching with the asymptotic results in a certain region of ${\text{Re}}_M$ values, as well as extend the stall predictions of ${\tilde{A}}_s$ to higher ${\text{Re}}_M$. Parametric studies provide data for the design of novel airfoils with blunt noses and higher stall angles of attack at various Re.

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• Aerodynamics
• Boundary layers