Special Session 8: Recent Progress on Mathematical Analysis of PDEs Arising in Fluid Dynamics

Stability threshold of Couette flow for the 3D MHD equations

Ruizhao Zi
Central China Normal University
Peoples Rep of China
Co-Author(s):    
Abstract:
In this talk, we consider the stability of 3D Couette flow $(y,0,0)^\top$ in a uniform background magnetic field $\al(\sig, 0,1)^\top$. It is shown that if the background magnetic field $\al(\sig, 0,1)^\top$ with $\sig\in\mathbb{R}\backslash\mathbb{Q}$ satisfying a generic Diophantine condition is so strong that $|\al|\gg \fr{\nu+\mu}{\sqrt{\nu\mu}}$, and the initial perturbations $u_{\mathrm{in}}$ and $b_{\mathrm{in}}$ satisfy $ \left\|(u_{\mathrm{in}},b_{\mathrm{in}})\right\|_{H^{N+2}}\ll\min\left\{\nu, \mu\right\}$ for sufficiently large $N$, then the resulting solution remains close to the steady state in $L^2$ at the same order for all time. Compared with the result of Liss [Comm. Math. Phys., 377(2020), 859--908], we use a more general energy method to address the physically relevant case $\nu\ne\mu$ based on some new observations. This is based on a joint work with Yulin Rao and Zhifei Zhang.