Injecting a Liquid in Weightlessness: Droplet or Geyser Formation

Injecting a liquid into a gas-filled vessel while in weightlessness can result in at least two conditions–a droplet attached to the wall around the injection orifice and a geyser in which the liquid propagates away from the orifice in a continuous jet. The need to design injection of liquid to accomplish one condition or the other shows up in both zero-g fluids research geometries and spaceflight systems. Previous experiments by others assumed the rim of the injection orifice to be sharp. Liquid flow out of orifices with chamfered and rounded rims during the weightlessness of parabolic aircraft flight are studied in this work. When compared to previous work, results indicate that chamfered and rounded rims have little effect on the value of Weber number dividing the wall-bound droplet and geyser behaviors. Because any manufactured orifice will have finite bluntness, this conclusion is useful for both research and spaceflight systems.