## Weakly Singular Waves and Blow-up for a Regularization of the Shallow-water System

thesis

posted on 01.08.2018 by Yue Pu#### thesis

In order to distinguish essays and pre-prints from academic theses, we have a separate category. These are often much longer text based documents than a paper.

This thesis studies a regularization of the classical Saint-Venant (shallow-water) system, namely the regularized shallow-water (Airy or Saint-Venant) system, recently

introduced by D. Clamond and D. Dutykh. This regularization is non-dispersive and formally conserves mass, momentum and energy. We show that for every classical shock wave, this system admits a corresponding

non-oscillatory traveling wave solution which is continuous and piecewise smooth, having a weak singularity at a single point where the energy is dissipated as it is for the classical

shock. This system also admits cusped solitary waves of both elevation and depression. The Hs (s > 2) large time existence with respect to the scaling of initial data and

uniqueness are established using an iteration scheme. The solution exists so long as the first derivatives are bounded in L1. When the energy is small, the height of water admits a positive lower bound dictated by the smallness of the energy. Lastly, we show that there exists smooth initial data with which the L1 norm of the first derivatives go unbounded in finite amount of time. This is proved by a Riccati-type

analysis with the help from Landau-Kolmogorov inequality that addresses the nonlocal part.

introduced by D. Clamond and D. Dutykh. This regularization is non-dispersive and formally conserves mass, momentum and energy. We show that for every classical shock wave, this system admits a corresponding

non-oscillatory traveling wave solution which is continuous and piecewise smooth, having a weak singularity at a single point where the energy is dissipated as it is for the classical

shock. This system also admits cusped solitary waves of both elevation and depression. The Hs (s > 2) large time existence with respect to the scaling of initial data and

uniqueness are established using an iteration scheme. The solution exists so long as the first derivatives are bounded in L1. When the energy is small, the height of water admits a positive lower bound dictated by the smallness of the energy. Lastly, we show that there exists smooth initial data with which the L1 norm of the first derivatives go unbounded in finite amount of time. This is proved by a Riccati-type

analysis with the help from Landau-Kolmogorov inequality that addresses the nonlocal part.

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### History

#### Date

01/08/2018#### Degree Type

Dissertation#### Department

Mathematical Sciences#### Degree Name

- Doctor of Philosophy (PhD)