Dynamic behavior of air-oil interface in fluid dynamic bearings with a double sealing structure in a 2.5′′ hard disk drive due to non-operating axial shock

We propose a numerical procedure to investigate the oil leakage of FDBs with a double sealing structure in a 2.5′′ HDD due to non-operating axial shock. We confirm the validity of the proposed procedure via a drop test to observe oil leakage of FDBs from the motion of rotor and stator under axial shock. We simulate the two-phase flow of air and oil in FDBs using a finite-volume method and a volume of fluid method to investigate the unsteady motion and break-up of the air-oil interfaces during and after axial shock. Furthermore, we analyze the axial shock-induced motion of air-oil interfaces due to magnitude of shock, and various design variables of the FDBs and the capillary seal.