The effects of nozzle geometry on waterjet breakup at high Reynolds numbers

Waterjet breakup is traditionally considered to follow the Ohnesorge classification. In this classification, high Reynolds number waterjets are considered to atomize quickly after discharge. By generating a constricted waterjet where the water flow stays detached all the way through the nozzle, we have observed the first wind-induced breakup mode at high Reynolds numbers. Such a peculiar behavior, however, was not observed in nonconstricted waterjets. Our results indicate that, constricted jets do not follow the Ohnesorge classification, in contrast to the non-constricted waterjets. We discuss the impact of nozzle geometry on the characteristics of waterjets and support our discussion by numerical simulations. List of symbols Z Ohnesorge number lL water dynamic viscosity r air–water surface tension qL water density qg air density dj waterjet diameter at the nozzle outlet d0 nozzle capillary diameter UL flow velocity WeL Weber number based on water density Weg Weber number based on air density ReL Reynolds number