Computational investigation on the effect of velocity modulation on low-velocity round liquid jets

The growth of perturbations on the surface of a liquid jet has been sought to be the major mechanism behind liquid jet disintegration and atomization. The contributing factors to the initiation of disturbances are predominantly present in the nozzle interior in the form of pressure oscillations, turbulence and cavitation. These perturbations are further enhanced by the interaction of liquid jets with ambient aerodynamic forces. In the present study, periodic disturbances in the form of well defined velocity modulation were imposed on a cylindrical liquid jet exiting a nozzle. The effect of such disturbances on the jet’s liquid-gas interface results in the formation of a wide variety of structures such as discs, bells and droplets. In the present paper, we investigate numerically the impact of these forced disturbances on the liquid jet behavior using a finite-volume-based code incorporating a Compressive Interface Capturing Scheme for Arbitrary Meshes (CICSAM) scheme on structured meshes to track the deformation of the liquid interface. The present study concerns low velocity jets and hence no turbulence model has been incorporated. For small modulation amplitudes in the appropriate frequency range, bulging of the liquid jets with finite periodicity is observed. Increasing the disturbance amplitude results in disc formation. Further increasing the modulation amplitude results in the break-up of the discs into rings that subsequently disintegrate into droplets due to the effect of aerodynamic forces. Computations with different combinations of modulation frequency, amplitude and liquid jet velocity are studied to identify their influence on liquid structures. Corresponding author