Dynamical Behavior for the Solutions of the Navier-Stokes Equation

TL;DR

This paper investigates the blowup behavior, profiles, and concentration phenomena of solutions to the Navier-Stokes equations in higher dimensions, providing conditions for global existence and characterizing minimal blowup solutions.

Contribution

It derives the blowup profile and concentration phenomena in $L^p$ spaces, establishes conditions for global solutions based on Fourier support, and constructs minimal blowup solutions in 3D.

Findings

Blowup rate estimates for solutions in $L^p$ spaces.

Conditions for global existence with specific Fourier support.

Existence of minimal blowup solutions with precise norm behavior.

Abstract

We study the Cauchy problem for the incompressible Navier-Stokes equations (NS) in three and higher spatial dimensions: \begin{align} u_t -\Delta u+u\cdot \nabla u +\nabla p=0, \ \ {\rm div} u=0, \ \ u(0,x)= u_0(x). \label{NSa} \end{align} Leray and Giga obtained that for the weak and mild solutions $u$ of NS in $L^p(\mathbb{R}^d)$ which blow up at finite time $T>0$, respectively, one has that for $d <p \leq \infty$, $$ \|u(t)\|_p \gtrsim ( T-t )^{-(1-d/p)/2}, \ \ 0< t<T. $$ We will obtain the blowup profile and the concentration phenomena in $L^p(\mathbb{R}^d)$ with $d\leq p\leq \infty$ for the blowup mild solution. On the other hand, if the Fourier support has the form ${\rm supp} \ \widehat{u_0} \subset \{\xi\in \mathbb{R}^n: \xi_1\geq L \}$ and $\|u_0\|_{\infty} \ll L$ for some $L >0$, then \eqref{NSa} has a unique global solution $u\in C(\mathbb{R}_+, L^\infty)$. Finally, if the blowup rate is of type I: $$ \|u(t)\|_p \sim ( T-t )^{-(1-d/p)/2}, \ for \ 0< t<T<\infty, \ d<p<\infty $$ in 3 dimensional case, then we can obtain a minimal blowup solution $\Phi$ for which $$ \inf \{\limsup_{t \to T}(T-t)^{(1-3/p)/2}\|u(t)\|_{L^p_x}: \ u\in C([0,T); L^p) \mbox{\ solves \eqref{NSa}}\} $$ is attainable at some $\Phi \in L^\infty (0,T; \ \dot B^{-1+6/p}_{p/2,\infty})$.