Large global solutions to 3-D inhomogeneous Navier–Stokes equations slowly varying in one variable

Abstract

Motivated by Chemin and Gallagher (2010) [8], we consider the global wellposedness to the 3-D incompressible inhomogeneous Navier–Stokes equations with large initial velocity slowly varying in one space variable. In particular, we proved that when the initial density is close enough to a positive constant, then given divergence free initial velocity field of the type ( v 0 h + ϵ w 0 h , w 0 3 ) ( x h , ϵ x 3 ) , as that in Chemin and Gallagher (2010) [8] for the classical Navier–Stokes system, we shall prove the global wellposedness of (INS) for ϵ sufficiently small. The main difficulty here lies in the fact that we will have to obtain the L 1 ( R + ; Lip ( R 3 ) ) estimate for convection velocity in the transport equation of (INS). Toward this and due to the strong anisotropic properties of the approximate solutions, we will have to work in the framework of anisotropic type Besov spaces here.