SearcharxivSearch

arXiv subjects

Eleni Hübner-Rosenau

Publications and source records attributed to Eleni Hübner-Rosenau.

2 recordsLinked to original sources

Homogenization of the Navier-Stokes equations in a randomly perforated domain in the inviscid limit

We study the behaviour of the solution $u_\varepsilon$ to the Navier-Stokes equations with vanishing viscosity and a non-slip condition in a randomly perforated domain. We consider the space $\mathbb{R}^3$ where we remove $N$ holes that are i.i.d. distributed. The behaviour depends on the particle size $\varepsilon^\alpha=N^{-\alpha/3}$ and the viscosity $\varepsilon^\gamma=N^{-\gamma/3}$ of the fluid. We prove quantitative convergence results to a function $u$, provided that the local Reynolds number is small, in the subcritical ($\alpha+\gamma>3$) and critical ($\alpha+\gamma=3$) regime. In the first case, $u$ solves the Euler equations, whereas in the second case $u$ solves the Euler-Brinkman equations. This extends the results of https://doi.org/10.1088/1361-6544/acfe56 from the periodic to the random setting. We only treat the case $\alpha>2$ so that the particles do not overlap with overwhelming probability.

math.AP

One-dimensional inelastic collapse of four particles: asymmetric collision sequences and spherical billiard reduction

We consider a one-dimensional system of four inelastic hard spheres, colliding with a fixed restitution coefficient $r$, and we study the inelastic collapse phenomenon for such a particle system. We study a periodic, asymmetric collision pattern, proving that it can be realized, despite its instability. We prove that we can associate to the four-particle dynamical system another dynamical system of smaller dimension, acting on $\{1,2,3\} \times \mathbb{S}^2$, and that encodes the collision orders of each trajectory. We provide different representations of this new dynamical system, and study numerically its $ω$-limit sets. In particular, the numerical simulations suggest that the orbits of such a system might be quasi-periodic.

math.DS