# Hydrodynamic models and confinement effects by horizontal boundaries

## TL;DR

This paper investigates how rigid horizontal boundaries influence ideal fluid dynamics, revealing that contact with boundaries can cause finite-time singularities in the models, with analysis supported by numerical simulations.

## Contribution

It analyzes the effects of boundary contact on long-wave models and Euler systems, highlighting conditions leading to singularities and providing numerical validation.

## Key findings

- Contact with boundaries can cause finite-time singularities.
- Models predict qualitative and quantitative effects of confinement.
- Numerical simulations support theoretical predictions.

## Abstract

Confinement effects by rigid boundaries in the dynamics of ideal fluids are considered from the perspective of long-wave models and their parent Euler systems, with the focus on the consequences of establishing contacts of material surfaces with the confining boundaries. When contact happens, we show that the model evolution can lead to the dependent variables developing singularities in finite time. The conditions and the nature of these singularities are illustrated in several cases, progressing from a single layer homogeneous fluid with a constant pressure free surface and flat bottom, to the case of a two-fluid system contained between two horizontal rigid plates, and finally, through numerical simulations, to the full Euler stratified system. These demonstrate the qualitative and quantitative predictions of the models within a set of examples chosen to illustrate the theoretical results.