stokes-creeping-flow-draglisted

# Stokes Creeping-Flow Drag (aerodynamics/boundary-layer/stokes-creeping-flow-drag) Use when you must compute the steady creeping (Stokes, 1851) flow of a viscous fluid past a sphere at Reynolds number well below one: the slow-motion solution of the full Navier-Stokes equations with the inertia terms dropped, in the form Schlichting Boundary-Layer Theory section 4 presents it. This leaf implements the Stokes streamfunction and the velocity field about the sphere, the surface pressure and wall shear, the total drag F = 6*pi*mu*a*U with its exact one-third pressure (form) to two-thirds friction split, the drag coefficient Cd = 24/Re_D, the Oseen first-order drag correction and the terminal settling velocity, in pure Python stdlib, closed form, no iteration. It is the steady low-Reynolds-number member of the exact-viscous family, complementing the time-dependent plate Stokes layers of unsteady-laminar-stokes-layers, and it anchors low-Reynolds-number body-drag estimates for particle drift and droplet settling checks. It does not do time-dependent plate Stokes layers, high-Mach compressible sphere drag, flat-plate boundary layers or parachute descent balances: incompressible constant-property laminar flow only, uniform mu and nu, Reynolds numbers in the creeping range. ## Domain quick reference Spherical polar coordinates (r, theta) with theta measured from the downstream pole: the uniform stream U runs along +z toward theta = 0 and the windward stagnation point sits at theta