A perturbative approach to Lagrangian flow networks

TL;DR

This paper introduces a perturbative method to analyze how modifications in geophysical flow transport processes affect the steady state of Lagrangian flow networks, with applications in environmental contamination management.

Contribution

It develops a perturbation-theoretic framework for Lagrangian flow networks to analytically assess the impact of flow modifications on transport dynamics.

Findings

Analytical expressions for steady state changes derived from eigensystem analysis.

Applicable to scenarios like particle trapping, contamination, and flow perturbations.

Potential for improved environmental response strategies.

Abstract

Complex network approaches have been successfully applied for studying transport processes in complex systems ranging from road, railway or airline infrastructure over industrial manufacturing to fluid dynamics. Here, we utilize a generic framework for describing the dynamics of geophysical flows such as ocean currents or atmospheric wind fields in terms of Lagrangian flow networks. In this approach, information on the passive advection of particles is transformed into a Markov chain based on transition probabilities of particles between the volume elements of a given partition of space for a fixed time step. We employ perturbation-theoretic methods to investigate the effects of modifications of transport processes in the underlying flow for three different problem classes: efficient absorption (corresponding to particle trapping or leaking), constant input of particles (with additional source terms modeling, e.g., localized contamination), and shifts of the steady state under probability mass conservation (as arising if the background flow is perturbed itself). Our results demonstrate that in all three cases, changes to the steady state solution can be analytically expressed in terms of the eigensystem of the unperturbed flow and the perturbation itself. These results are potentially relevant for developing more efficient strategies for coping with contaminations of fluid or gaseous media such as ocean and atmosphere by oil spills, radioactive substances, non-reactive chemicals or volcanic aerosols.