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To reduce the flow-induced vibration (FIV) of the head stack assembly (HSA) in the hard disk drive (HDD), we experimentally studied the spoiler, which is put between disks. This study was carried out using a laser doppler vibrometer (LDV) to measure the amplitude of the head slider vibration. We also measured the power consumption of the spindle motor.As parameters of the spoiler shape, the thickness and the length were selected. From the experimental result, these parameters effect significantly both the head's vibration and the power consumption. This result suggests that the flow rate reduction with the spoiler causes a reduction of the HSA's FIV, and the energy loss with the spoiler causes an increase of the power consumption.We defined the spoiler's FIV-reducing efficiency as a ratio of the amplitude reduction to the power consumption increase. The length change makes the peak value. This is caused by the fact that the FIV reduction becomes almost constant when the spoiler is longer than the carriage arm length inside disk region, although the spoiler length makes power consumption monotonically large.Index Terms-Flow-induced vibration, hard disk, head stack assembly, spoiler.

This paper elucidates the performance degradation and flow instability of an axial fan caused by the presence of disk-shaped obstacles upstream of the fan, such as wall surfaces. The increase in pressure loss and the decrease in shaft power coefficient due to inlet swirl flow, and the increase in pressure loss due to the outlet swirl flow, cause performance degradation. When the obstacle is closer to the fan, the strong swirl flow causes a negative pressure region between the fan and the obstacle, reversing the flow direction. This phenomenon is caused by the diffuser effect of the outward flow and the increase in pressure by acting as a multiblade centrifugal fan. At a low flow rate, a clockwise vortex is generated at the center of the obstacle and induces two counterclockwise rotating vortices. The vortices circumferentially separate the inward and outward flows along the fan's axis in a uniform manner, and their cores are circularly rotated by the clockwise vortex. These findings can contribute to the layout of fans under spatial restriction and suppression of flow instability due to obstacles.

Axial-flow fans have been used in various applications such as thermal control and ventilation. Fans are often used in narrow spaces around obstacles such as electric parts, areas near clogged of fan filters, and walls. These obstacles lead to decreased performance and increased noise and vibration in electric devices. This study attempts to experimentally clarify the influences of upstream/downstream-mounted blockage disks on the flow characteristics of an axial-flow fan. The important results are summarized as follows: (1) For the same relative distance, the pressure performance and efficiency curves of the fan owing to the upstream-mounted blockage disk completely differ from those owing to the downstream-mounted blockage disk. (2) For a small relative distance, the pressure coefficient owing to the upstream and downstream-mounted blockage disks decreases and increases, respectively. (3) The efficiency of the fan owing to the upstream-mounted blockage disk decreases. However, the efficiency owing to the downstream-mounted blockage disk increases for specific conditions.