Flow-induced vibration of a head gimbal assembly under various conditions
The flow-induced vibration of a head gimbal assembly (HGA), known as windage, is an obstacle to achieving higher track densities in hard disk drives (HDDs). We examine the characteristics of windage in this paper with the goal of enabling the development of smaller-windage HGAs. We used a 14.5-mm-length (from swage hole center to dimple) HGA in our study. The windage was measured by a laser Doppler vibrometer in a spin stand under various conditions, such as different slider radius locations (inner diameter, medium diameter, and outer diameter), disk-rotational speeds, Z heights (distance from arm to disk), and temperatures. With respect to the slider radius location, windage was much greater when the slider was on the outer diameter rather than at other positions. When the slider was positioned at a fixed location, the windage was proportional to the square of the disk rotational speed. At high temperatures, the resonant frequencies decreased and their amplitudes increased. For some resonance modes, there was an optimal Z height. These findings will be useful for evaluating HGAs and optimizing HGAs through experimental design.
Flow-induced vibration reduction in HDD by using a spoiler
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.
Influence of the geometry on the structure of the flow between a pair of corotating disks
Constant-property laminar flow in the space between two coaxial disks corotating in a fixed cylindrical enclosure is investigated numerically over the Reynolds number range 0⩽Re⩽82 380 for interdisk spacing to disk radius aspect ratios in the range 0.05⩽S⩽0.20. Most of the 3D calculations correspond to regions in the (Re, S) map slightly above the 2D–3D transition, where the 2D (axisymmetric) steady flow can bifurcate into two different families of unsteady 3D flow; (a) at sufficiently large values of S or Re, into a flow that is asymmetric with respect to the interdisk midplane; (b) at intermediate values of S and Re, into a flow that displays shift-and-reflect symmetry with respect to the interdisk midplane. Qualitative and quantitative comparisons with previous experimental and numerical results are established. The structure of the 3D flow is analyzed as well as the jumps in wave frequency when it experiences a change in its circumferential wave length. It is shown that each family of 3D flows is char...