Behavior of synchronous and asynchronous spatially oscillating planar liquid jets in tandem

Understanding the behavior of oscillating liquid jets in tandem is vital for improving the efficacy of numerous industrial applications. An interpretation of their behavior in the terms of development, associated instability, and interactions when used in tandem remains unclear. Therefore, the present study reports the numerical investigations on spatially oscillating liquid jets in tandem. Numerical simulations are carried out by solving Navier-Stokes equations coupled with volume of fluid method to track the air-water interface. The development of the tandem jets, growth in amplitude of oscillation, and interaction between the coherent structures is analyzed for both synchronous and asynchronous liquid jets in tandem. Moreover, the effect of nozzle spacing on these parameters is also reported in the present study. It is demonstrated that a decrease in the nozzle spacing destabilizes these jets and promotes an early merging between them. This decrease in nozzle spacing also improves the stream-wise entrainment of the surrounding fluid. Furthermore, synchronous jets are found to be more stable as compared to asynchronous jets owing to a relatively constant spacing between the two jets. Asynchronous jets provide better fluid entrainment than synchronous jets owing to their higher amplitude of oscillation and stronger jet front interactions. Moreover, it is demonstrated that these interactions at the jet front give rise to a staggered vortex front in asynchronous jets, whereas the vortex front remains symmetric in synchronous jets.