Potential Singularity of the Axisymmetric Euler Equations with $C^{\hat{I}}\pm$ Initial Vorticity for A Large Range of $\hat{I}\pm$. Part II: the $N$-Dimensional Case

Abstract

In Part II of this sequence to our previous paper for the 3-dimensional Euler equations \cite{zhang2022potential}, we investigate potential singularity of the $n$-diemnsional axisymmetric Euler equations with $C^{\hat{I}}\pm$ initial vorticity for a large range of $\hat{I}\pm$. We use the adaptive mesh method to solve the $n$-dimensional axisymmetric Euler equations and use the scaling analysis and dynamic rescaling method to examine the potential blow-up and capture its self-similar profile. Our study shows that the $n$-dimensional axisymmetric Euler equations with our initial data develop finite-time blow-up when the Hölder exponent $\hat{I}\pm <\hat{I}{\pm }^{\ast }$, and this upper bound $\hat{I}{\pm }^{\ast }$ can asymptotically approach $1-\frac{2}{n}$. Moreover, we introduce a stretching parameter $\hat{I}´$ along the $z$-direction. Based on a few assumptions inspired by our numerical experiments, we obtain $\hat{I}{\pm }^{\ast }=1-\frac{2}{n}$ by studying the limiting case of $\hat{I}´\to 0$. For the general case, we propose a relatively simple one-dimensional model and numerically verify its approximation to the $n$-dimensional Euler equations. This one-dimensional model sheds useful light to our understanding of the blowup mechanism for the $n$-dimensional Euler equations. As shown in \cite{zhang2022potential}, the scaling behavior and regularity properties of our initial data are quite different from those of the initial data considered by Elgindi in \cite{elgindi2021finite}.

This paper has been merged with its Part I series (arxiv:2212.11912). The merged new paper has been submitted to replace its Part I paper (arxiv:2212.11912), and therefore there is no need to keep this paper