Droplet formation from a pulsed vibrating micro-nozzle

Abstract

Micro-droplet formation from a passive vibrating micro-nozzle driven by a pulsed pressure wave is numerically simulated. The micro-nozzle is formed from an orifice in a thin walled plate that is allowed to freely vibrate due to the pressure loading on the plate. The analysis couples the fluid flow from the nozzle and the resultant droplet formation with the nozzle vibration calculated using large deflection theory. The problem is made nondimensional based on the capillary parameters of time, velocity and pressure. The applied pressure and nozzle material properties are varied to alter the vibration characteristics of the orifice plate used to form the nozzle. The initiation of drop formation is found to coincide with a threshold impulse input, defined as the product of the pressure magnitude and the pulse duration. Increasing the impulse can result in multiple satellite droplet formation, but the effect on the primary droplet size is minor. The vibration of the nozzle only weakly influences the droplet break-off time, but is shown to significantly affect the droplet volume, shape, and satellite droplet formation.