On amplitudes of disk flutter vibrations in helium-air mixture gas filled hard disk drives with flow mitigation devices

Abstract

The experimental results which we had conducted in the past were synthesized to find universal characteristics of disk flutter which is commonly seen in various drive structures and internal gas conditions. Disk flutter vibrations in 3.5” and 2.5” hard drives equipped with different types of flow mitigation devices were measured under the various mixture ratios of internal helium-air mixture gas and disk speeds. It was found that the amplitudes of disk flutter vibrations showed the same trend with respect to the product of gas density and disk speed: At low gas densities and disk speeds, the vibration amplitudes were quite small. At high densities and speeds, they were large, and their variations were small. In the middle, meanwhile, they showed large amplitudes and variations. In conclusion, it looks to be associated with laminar and turbulent flow regimes. To explain the experimental results by Reynolds number, the characteristic length must take the similar values in the 3.5” and 2.5” drives, but the suitable one has not been found yet.