squire-young-profile-draglisted

# Squire-Young Profile Drag (aerodynamics/boundary-layer/squire-young-profile-drag) Use when you must compute the section profile-drag coefficient of a two-dimensional body or airfoil from the boundary-layer momentum state at its trailing edge with the Squire-Young formula (Squire and Young, ARC R&M 1838, 1938; Schlichting, Boundary-Layer Theory, 7th ed., pp. 158-162; validated against surface-integrated CFD within 2-3 percent in the low-drag range by Coder and Maughmer, Journal of Aircraft 52(3), 2015): c_d,p = 2*(theta_TE/c)*(U_TE/U_inf)**((H_TE+5)/2). This leaf evaluates the trailing-edge factor, maps a known TE momentum state to the profile-drag coefficient, grows the laminar momentum thickness to the trailing edge on the integral growth relation for the fully laminar chain, and reproduces the Blasius flat-plate drag exactly at zero pressure gradient. It is the TE-to-drag member of the boundary-layer pack, complementing the traverses of boundary-layer-separation and boundary-layer-transition, which stop at their separation and transition signals and never map the TE momentum state to drag. It does not do Thwaites lambda traverses, separation or transition criteria, flat-plate skin-friction or thickness correlations, whole-aircraft drag buildup, XFOIL-style polar runs, rotor-blade profile power, or wake-survey instrumentation: incompressible clean 2-D attached flow only, one surface of the section at a time. ## Domain quick reference Module constants (fixed numbers): NU