Meniscus Shape and Splashing of Magnetic Fluid in a Magnetic Fluid Seal

Magnetic fluid splashing from a magnetic fluid seal due to high-speed rotation of the seal ring was experimentally investigated in relation to clearance and magnetic field strength around a gap to be sealed. Meniscus deformation, owing to fluid rotation, was accurately observed by a silhouette formed when the meniscus was illuminated with a bold laser beam from behind. Deformation was found to occur in three stages. In the first stage, the meniscus static width shrank while the meniscus rotation height remained essentially unchanged. In the second stage, rotational height increased slightly and then returned to equilibrium. In the third stage, there was an abrupt entire shrinkage accompanied by splashing at the back side of the gap. With a further increase in rotation speed, splashing at the front side of the gap occurred, which resulted in irreversible loss of fluid. Relationships between the splashing initiation speed at the front gap and meniscus size just before the occurrence of splashing were clarified with the clearance and magnetic field strength as parameters. A useful simple indicator of splashing initiation was established based on these results.