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

Abstract

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 St = 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 (St = 0.22) induce periodic flapping, suppress RT-driven waves, and reduce breakup length remarkably, while frequency-matching RT instability (St = 1) amplifies surface undulations, accelerating column disintegration. High-frequency perturbations (St ≥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.