Global existence of strong solution for viscous shallow water system with large initial data on the irrotational part
Résumé
We are interested in studying the Cauchy problem for the viscous shallow-water system in dimension $N\geq 2$, we show the existence of global strong solutions with \textit{large} initial data on the irrotational part of the velocity for the scaling of the equations. More precisely our smallness assumption on the initial data is supercritical for the scaling of the equations. It allows us to give a first kind of answer to the problem of the existence of global strong solution with large initial energy data in dimension $N=2$. To do this, we introduce the notion of \textit{quasi-solutions} which consists in solving the pressureless viscous shallow water system. We can obtain such solutions at least for irrotationnal data which exhibit regularizing effects both on the velocity and also on the density. This smoothing effect is purely non linear and is crucial in order to build solution of the viscous shallow water system as perturbations of the "quasi-solutions". Indeed the pressure term remainder becomes small in high frequencies for the scaling of the equations. To finish we prove the existence of global strong solution with large initial data when $N\geq 2$ for the viscous shallow water system provided that the Mach number is sufficiently large.
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