This paper is devoted to the derivation and mathematical analysis of a wave-structure
interaction problem which can be reduced to a transmission problem for a Boussinesq
system. Initial boundary value problems and transmission problems in dimension
for
hyperbolic systems are well understood. However, for many applications, and
especially for the description of surface water waves, dispersive perturbations of
hyperbolic systems must be considered. We consider here a configuration where the
motion of the waves is governed by a Boussinesq system (a dispersive perturbation
of the hyperbolic nonlinear shallow water equations), and in the presence
of a fixed partially immersed obstacle. We shall insist on the differences
and similarities with respect to the standard hyperbolic case, and focus
our attention on a new phenomenon, namely, the apparition of a dispersive
boundary layer. In order to obtain existence and uniform bounds on the
solutions over the relevant time scale, a control of this dispersive boundary
layer and of the oscillations in time it generates is necessary. This analysis
leads to a new notion of compatibility condition that is shown to coincide
with the standard hyperbolic compatibility conditions when the dispersive
parameter is set to zero. To the authors’ knowledge, this is the first time
that these phenomena (likely to play a central role in the analysis of initial
boundary value problems for dispersive perturbations of hyperbolic systems) are
exhibited.
Keywords
wave-structure interaction, Boussinesq system, free
surface, transmission problem, local well-posedness,
dispersive boundary layer, oscillations in time,
compatibility conditions