Frequency-Dependent Interfacial Instability and Vortex Dynamics of a Disturbed Liquid Jet in Crossflow

This study investigates the primary atomization dynamics of a sinusoidal-disturbed liquid jet in a gaseous crossflow, focusing on perturbation frequencies spanning 0 − 1500 kHz (Strouhal number S t = 0 − 5 ). A high-fidelity numerical framework combining the Volume of Fluid (VOF) interface capturing method and octree-based adaptive mesh refinement is employed to resolve interfacial instabilities, vortex dynamics, and droplet formation mechanisms. For the undisturbed jet, Rayleigh-Taylor (RT) instability dominates surface wave formation, producing characteristic “ Λ ”-shaped structures and governing ligament/droplet shedding. Under forced perturbations, four distinct frequencies are systematically analyzed to elucidate modulation effects. Key findings reveal that low-frequency disturbances ( S t = 0.22 ) induce periodic flapping, suppress RT-driven waves, and reduce breakup length remarkably, while frequency-matching RT instability ( S t = 1 ) amplifies surface undulations, accelerating column disintegration. High-frequency perturbations ( S t ≥ 2 ) exhibit rapid near-nozzle damping, restoring unperturbed breakup characteristics. Vorticity analysis identifies counter-rotating vortex pairs as critical drivers of interfacial destabilization, with perturbation frequency non-monotonically modulating annular vortex dynamics. Trajectory comparisons demonstrate breakup length minima at intermediate Strouhal numbers, linked to wavelength-dependent wave topology transitions. These insights establish a frequency-dependent mechanism for controlling jet atomization, offering direct applications for reducing combustion instabilities through targeted flow modulation in propulsion systems.