Asymmetric flame-vortex dynamics induced by self-excited transverse instability in a dual bluff-body spray burner

High-frequency thermoacoustic instabilities in spray flames are difficult to predict due to tightly coupled acoustics-flow-combustion-spray interactions. Focusing on a V-shaped dual bluff-body configuration, this study combines experiment and carrier-phase large-eddy simulation (CP-LES) to (i) assess whether LES can capture a self-excited transverse screeching mode in this complex setting and (ii) elucidate the oscillation characteristics and the underlying coupling mechanisms. Two flames are investigated: one stable and the other unstable, exhibiting self-excited oscillations at approximately 2000 Hz. The CP-LES results show good agreement with experimental measurements, including high-speed OH ∗ chemiluminescence, mid-plane velocity profiles, and acoustic pressure. Based on the LES results, the oscillation mode is extracted using Dynamic Mode Decomposition (DMD). The findings reveal a typical transverse mode, which closely matches the 3 L x -2 T y -0 T z intrinsic mode with a frequency of 1946 Hz predicted by the acoustic solver. The mode induces periodically asymmetric, corrugated flame fronts with phase offsets across the four shear layers. Further DMD of heat-release-rate and kerosene fields quantifies coupling between fuel–air mixing and flame oscillations, while wavenumber-domain decomposition links transverse velocity fluctuations to modulation of mixing. Overall, the demonstrated agreement shows that CP-LES can reproduce high-frequency transverse instability in a complex multi-holder spray system and advances understanding of the features and mechanisms of transverse oscillations. In addition, the high-fidelity, experiment-anchored dataset provides a useful benchmark for future validation and modeling of high-frequency thermoacoustic instabilities.