Identifying location of flow excitation on rotating disks in low Reynolds number flow using gain/phase relationships between vibration modes

Abstract

It was found that frequency spectra of vibrations in rotating disks of a helium-air mixture gas filled HDD sometimes showed anti-resonances between disk mode frequencies. It indicates that the flow excitation forces were coherent and can be represented by a load on a single point. In this paper, the angular and radial positions were estimated by anti-resonances in the frequency spectrum of disk vibrations and the difference of vibration amplitudes between spindle and disk modes. Comparing the estimated locations and the drive structure, they were coincident to the end of disk shroud and the top of trailing edge of spoiler. Therefore, it is suspected that vortices generated in the wakes after these structures were the root cause of large disk vibration in the helium-air mixture gas filled HDD.