Airflow pressure and shear forces on a rotating, deformed disk in an open shroud

Abstract

The static pressure and surface shear forces on a rotating, umbrella-deformed disk in an open shroud are investigated numerically to develop a proper dynamical model for investigation of the self-excited vibration of the disk. The fluid force distributions along the radial direction of the rotating disk are obtained by use of a two-dimensional numerical model of the axisymmetric deformation of disk. It is observed that the effects of Reynolds number and deformation amplitude are very significant on the fluid forces. Once the rotating disk is deformed, the vortex asymmetry in the airflow patterns appears in the narrow and wide gaps between the rotating disk and the two fixed walls. With increasing deformation amplitude, the asymmetry becomes more obvious. The vortex becomes strong as Reynolds number increases. In addition, it is observed that the transition flow between the laminar and turbulent flows exists in the narrow-gap side. Such a transition flow causes the fluid forces to be non-smooth in the corresponding region, and the force discontinuity will lead to the complicated vibration of rotating disk. From this investigation, the fluid forces for different modes of the rotating disk should be further investigated analytically and numerically for a better understanding of the mechanism of self-excited vibration in hard-disk drive system.