“…The Navier-Stokes equations on spheres and more general manifolds with this kind of viscous term have been studied by many authors (see e.g. [43,36,33,31,9,21,5,7,39,40,35,22,37,38]). There are also several works on the Navier-Stokes equations on manifolds in which the viscous term is taken to be ν∆ H u by analogy of the flat domain case (see e.g.…”