A mathematical clue to the separation phenomena on the two-dimensional Navier-Stokes equation

In general, before separating from a boundary, the flow moves toward reverse direction near the boundary against the laminar flow direction. Here in this paper, a clue to such reverse flow phenomena (in the mathematical sense) is observed. More precisely, the non-stationary two-dimensional Navier-Stokes equation with an initial datum having a parallel laminar flow (we define it rigorously in the paper) is considered. We show that the direction of the material differentiation is opposite to the initial flow direction and effect of the material differentiation (inducing the reverse flow) becomes bigger when the curvature of the boundary becomes bigger. We also show that the parallel laminar flow cannot be a stationary Navier-Stokes flow near a portion of the boundary with nonzero curvature

Long-time solvability of the Navier-Stokes-Boussinesq equations with almost periodic initial large data

We investigate large time existence of solutions of the Navier-Stokes-Boussinesq equations with spatially almost periodic large data when the density stratification is sufficiently large. In 1996, Kimura and Herring \cite{KH} examined numerical simulations to show a stabilizing effect due to the stratification. They observed scattered two-dimensional pancake-shaped vortex patches lying almost in the horizontal plane. Our result is a mathematical justification of the presence of such two-dimensional pancakes. To show the existence of solutions for large times, we use $\ell^1$-norm of amplitudes. Existence for large times is then proven using techniques of fast singular oscillating limits and bootstrapping argument from a global-in-time unique solution of the system of limit equations

On dispersive effect of the Coriolis force for the stationary Navier-Stokes equations

The dispersive effect of the Coriolis force for the stationary Navier-Stokes equations is investigated. The effect is of a different nature than the one shown for the non-stationary case by J. Y. Chemin, B. Desjardins, I. Gallagher and E. Grenier. Existence of a unique solution is shown for arbitrary large external force provided the Coriolis force is large enough. The analysis is carried out in a new framework of the Fourier-Besov spaces. In addition to the stationary case counterparts of several classical results for the non-stationary Navier-Stokes problem have been proven