On the effects of rotation on stationary Navier--Stokes equations in the half spaces in scale-critical spaces

In this paper, we study the three-dimensional incompressible stationary Navier–Stokes equations with the Coriolis force in the half space with the inhomogeneous Dirichlet boundary condition. We show the existence of a unique small solution in the scale-critical Besov spaces. In particular, for any boundary data with only the normal component assumed to be sufficiently small, and for any external forces, we establish the well-posedness of the inhomogeneous Dirichlet boundary value problem when the speed of rotation is sufficiently large. In the proof, to exploit the stabilizing effect of the Coriolis term, we employ two explicit formulas depending on the relation between the horizontal frequency and the magnitude of the rotation speed.