Steady State Statistics of Emergent Patterns in a Ring of Oscillators

TL;DR

This paper analyzes the emergent synchronization patterns in a ring of coupled Van der Pol oscillators under stochastic forcing, providing a low-order model that explains acoustic phenomena in gas turbines.

Contribution

It introduces an analytical and numerical framework for understanding pattern formation and synchronization in a symmetric ring of oscillators with stochastic influences, applicable to combustion acoustics.

Findings

Derived the stationary probability density function for the system.

Identified conditions for synchronization and desynchronization transitions.

Explained features of acoustic pressure spectrograms in gas turbines.

Abstract

Networks of coupled nonlinear oscillators model a broad class of physical, chemical and biological systems. Understanding emergent patterns in such networks is an ongoing effort with profound implications for different fields. In this work, we analytically and numerically study a symmetric ring of N coupled self-oscillators of Van der Pol type under external stochastic forcing. The system is proposed as a model of the thermo- and aeroacoustic interactions of sound fields in rigid enclosures with compact source regions in a can-annular combustor. The oscillators are connected via linear resistive coupling with nonlinear saturation. After transforming the system to amplitude-phase coordinates, deterministic and stochastic averaging is performed to eliminate the fast oscillating terms. By projecting the potential of the slow-flow dynamics onto the phase-locked quasi-limit cycle solutions, we obtain a compact, low-order description of the (de-)synchronization transition for an arbitrary number of oscillators. The stationary probability density function of the state variables is derived from the Fokker--Planck equation, studied for varying parameter values and compared to time series simulations. We leverage our analysis to offer explanations for features of acoustic pressure spectrograms observed in real-world gas turbines.