Random dynamics and invariant measures for a class of non-Newtonian fluids of differential type on 2D and 3D Poincar\'e domains

TL;DR

This paper studies the well-posedness and long-term behavior of stochastic non-Newtonian third-grade fluids on 2D and 3D Poincaré domains, proving existence of unique solutions, random attractors, and invariant measures.

Contribution

It establishes the existence of unique weak solutions, random attractors, and invariant measures for stochastic non-Newtonian fluids on bounded and unbounded Poincaré domains, using novel techniques for unbounded cases.

Findings

Existence of unique weak solutions under Dirichlet boundary conditions.

Existence of unique random attractors on bounded and unbounded domains.

Demonstration of invariant measures for the system.

Abstract

In this article, we consider a class of incompressible stochastic third-grade fluids (non-Newtonian fluids) equations on two- as well as three-dimensional Poincar\'e domains $\mathcal{O}$ (which may be bounded or unbounded). Our aims are to study the well-posedness and asymptotic analysis for the solutions of the underlying system. Firstly, we prove that the underlying system defined on $\mathcal{O}$ has a unique weak solution (in the analytic sense) under Dirichlet boundary condition and it also generates random dynamical system $\Psi$. Secondly, we consider the underlying system on bounded domains. Using the compact Sobolev embedding $\mathbb{H}^1(\mathcal{O}) \hookrightarrow\mathbb{L}^2(\mathcal{O})$, we prove the existence of a unique random attractor for the underlying system on bounded domains with external forcing in $\mathbb{H}^{-1}(\mathcal{O})+\mathbb{W}^{-1,\frac{4}{3}}(\mathcal{O})$. Thirdly, we consider the underlying system on unbounded Poincar\'e domains with external forcing in $\mathbb{L}^{2}(\mathcal{O})$ and show the existence of a unique random attractor. In order to obtain the existence of a unique random attractor on unbounded domains, due to the lack of compact Sobolev embedding $\mathbb{H}^1(\mathcal{O}) \hookrightarrow\mathbb{L}^2(\mathcal{O})$, we use the uniform-tail estimates method which helps us to demonstrate the asymptotic compactness of $\Psi$. Note that due to the presence of several nonlinear terms in the underlying system, we are not able to use the energy equality method to obtain the asymptotic compactness of $\Psi$ in unbounded domains, which makes the analysis of this work in unbounded domains more difficult and interesting. Finally, as a consequence of the existence of random attractors, we address the existence of invariant measures for underlying system.