Mesh-Free Interpolant Observables for Continuous Data Assimilation

TL;DR

This paper introduces a mesh-free interpolant observable framework for continuous data assimilation in 2D Navier-Stokes equations, enabling synchronization in higher-order Sobolev spaces with broader observational data types.

Contribution

It expands the class of interpolant observable operators for data assimilation, allowing for mesh-free observational data to achieve synchronization in stronger topologies.

Findings

Established synchronization in higher-order Sobolev norms.

Developed a broader class of mesh-free interpolant operators.

Provided bounds for the absorbing ball in all Sobolev norms.

Abstract

This paper considers a nudging-based scheme for data assimilation for the two-dimensional (2D) Navier-Stokes equations (NSE) with periodic boundary conditions and studies the synchronization of the signal produced by this algorithm with the true signal, to which the observations correspond, in all higher-order Sobolev topologies. This work complements previous results in the literature where conditions were identified under which synchronization is guaranteed either with respect to only the $H^1$--topology, in the case of general observables, or to the analytic Gevrey topology, in the case of spectral observables. To accommodate the property of synchronization in the stronger topologies, the framework of general interpolant observable operators, originally introduced by Azouani, Olson, and Titi, is expanded to a far richer class of operators. A significant effort is dedicated to the development of this more expanded framework, specifically, their basic approximation properties, the identification of subclasses of such operators relevant to obtaining synchronization, as well as the detailed relation between the structure of these operators and the system regarding the syncrhonization property. One of the main features of this framework is its "mesh-free" aspect, which allows the observational data itself to dictate the subdivision of the domain. Lastly, estimates for the radius of the absorbing ball of the 2D NSE in all higher-order Sobolev norms are obtained, thus properly generalizing previously known bounds; such estimates are required for establishing the synchronization property of the algorithm in the higher-order topologies.