Chaotic Regime Identification in Coupled Thermo-Fluid Oscillators Under Variable Boundary Forcing

Abstract

Coupled thermo-fluid oscillators are important in nonlinear thermal-flow systems where oscillation, heat transfer, and boundary effects interact under unsteady conditions. Existing studies have examined synchronization, bifurcation, forcing effects, and mode transition in thermoacoustic and thermofluidic oscillators, but they have not clearly identified chaotic regimes under variable boundary forcing. This study addresses that gap by developing a compact nonlinear oscillator model and a forcing-dependent regime-identification framework. The article analyzes time response, phase distortion, inter-oscillator interaction, and Lyapunov-based divergence to track the transition from regular motion to chaos. The results show that weak forcing maintains periodic behavior, while stronger forcing produces modulation, phase mismatch, response spreading, and finally chaotic motion. Overall, the study shows that forcing-sensitive nonlinear modeling is an effective framework for identifying instability transitions in coupled thermo-fluid oscillators.