supercritical-airfoillisted

# Supercritical Airfoil Design and Analysis (aerodynamics/high-speed/supercritical-airfoil) Use when the task is supercritical airfoil design and analysis: the flat upper surface, aft loading, drag-divergence Mach, wave-drag reduction, terminating shock strength, and the cruise lift coefficient of the section. ## Domain quick reference - Supercritical airfoil: a section whose nearly flat upper surface keeps the local Mach number barely supersonic over a long region. The weak supersonic pocket replaces the strong suction peak of a conventional section, so the terminating shock at its rear is weaker and wave drag at high subsonic Mach is reduced. - Terminating shock strength: the static pressure ratio p2/p1 across the normal shock that closes the supersonic pocket, p2/p1 = 1 + 2*gamma/(gamma+1)*(M^2 - 1), evaluated at the local Mach just ahead of the shock (gamma = 1.4). A conventional section at M 0.8 accelerates the upper surface to about M 1.3, ratio about 1.81; the flat top of a supercritical section holds it near M 1.15, ratio about 1.38. Weaker shock means less wave drag and less shock/boundary-layer separation risk. - Wave-drag penalty: above drag divergence, wave drag grows roughly with the cube of (M - M_DD). The penalty index (M - M_DD)^3 is zero at or below M_DD and rises steeply above it. - Drag-divergence Mach (Korn rule of thumb): M_DD = 0.95 - t/c - C_L/10 for a supercritical section and M_DD = 0.90 - t/c - C_L/10 for a convention