In this paper, using aerodynamic numerical analysis, we investigate mechani
sms causing disk nutter in hard disk drives. A computer simulation model of
three stacked disks was calculated using the finite-difference method with
the LES model of turbulence. As a result, secondary airflows were found to
move upward and downward though a shroud gap around the outer edge of the
disk. This inference from this discovery is that a phase difference of spat
ial pressure patterns between the top surface and bottom surface of a disk
causes disk flutter.