This person’s namesake number is low for tracers in PIV and equals the ratio between a particle’s characteristic response time and an obstacle's response time. The Oseen equations build upon a flow regime named for this person that exhibits a low Reynolds number, where no creeping flow can occur around a disk in this person’s namesake paradox. 6 pi times viscosity times radius (10[1])times flow velocity equals (10[1])a sphere’s drag according to a law named for this person, who also names a 3D analog of Green’s theorem. This person is the second namesake of a set of equations whose solutions’ existence and smoothness are a Millenium Prize problem and describe viscous fluid flow. For 10 points, name this Irish scientist who names those equations with Claude-Louis Navier. ■END■