Dynamic ejection behaviour of water molecules passing through a nano-aperture nozzle

This study used molecular dynamics (MD) simulation to investigate the passage of water molecules through a composite graphene/Au nano-nozzle. Our focus was on the degree to which system temperature, extrusion speed, and nozzle diameter affect jet dynamics and the associated transient phenomena. Our findings show that high pressure and spatial confinement cause the nanojet from a small nozzle diameter (1.0 nm) to bend and twist, whereas the jets from a nozzle with a diameter of 1.5 nm present columns of greater stability. At 100 K, the H2O nanojet froze at the outlet of the nozzle in the form of condensed icicles. At 500 K, the H2O nanojet formed a loose spray and gaseous clusters. High extrusion speed of 55.824 m/s produced recirculating flow downstream from the nanojet with the appearance of an erupting volcano, which further prompted the jet column to thicken. Lower extrusion speeds produced jets with flow velocity insufficient to overcome the capillary force at the outlet of the nozzle, which subsequently manifests as unstable fluctuations in the flow rate.