Flame response to transverse velocity excitation leading to frequency doubling and modal coupling

Transverse thermoacoustic modes may occur in gas turbines, aero-engines, and rocket engines. Various scenarios of flame excitation can be observed, depending on the type transverse mode location relative to shape. If an acoustically compact, symmetric is exposed velocity fluctuations uniform strength direction, resulting modulation overall heat release rate invariant direction perturbation. It follows that dominant response occurs at twice forcing frequency, even for infinitesimally small oscillation amplitude. The present study proposes a modeling framework this inherently non-linear phenomenon, which relies second-order kernel Volterra series. As possible realization series, ad-hoc model proposed validated with CFD mono-frequency forcing. Furthermore, mechanism modal interaction established by frequency doubling causes unstable drive higher order stable mode, such near-resonance conditions exhibits elevated This explain observations made Urbano et al. (2016) small-scale thrust chamber, where radial appears exactly mode. A simple representative setup cylindrical combustion chamber used analytically.