Chapter 59: τ-Navier–Stokes: Viscous Flow

Real fluids are not inviscid. Molecules interact, shear layers develop, energy dissipates. The Navier–Stokes equations extend the Euler equations by adding a viscous stress term that converts ordered kinetic energy into disordered thermal motion. In τ³, viscosity is not a phenomenological parameter pasted onto the equations: it is the inter-mode friction on T², a structural consequence of the non-orthogonality of distinct defect modes. This chapter derives the τ-Navier–Stokes equation, introduces the Reynolds number as a defect-tuple ratio, and previews the connection to the Millennium Problem that will be resolved in the relevant chapter.