Expansion shock waves in regularised shallow water theory
journal contributionposted on 29.04.2016 by Gennady El, M.A. Hoefer, Michael Shearer
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We identify a new type of shock wave by constructing a stationary expansion shock solution of a class of regularised shallow water equations that include the Benjamin-Bona-Mahoney (BBM) and Boussinesq equations. An expansion shock exhibits divergent characteristics, thereby contravening the classical Lax entropy condition. The persistence of the expansion shock in initial value problems is analysed and justified using matched asymptotic expansions and numerical simulations. The expansion shock’s existence is traced to the presence of a non-local dispersive term in the governing equation. We establish the algebraic decay of the shock as it is gradually eroded by a simple wave on either side. More generally, we observe a robustness of the expansion shock in the presence of weak dissipation and in simulations of asymmetric initial conditions where a train of solitary waves is shed from one side of the shock.
This work was supported by the Royal Society International Exchanges Scheme IE131353 (all authors), NSF CAREER DMS-1255422 (MAH), and NSF DMS-1517291 (MS).
- Mathematical Sciences