Flow Diverting to prevent Aerodynamic Buffeting in Hard Disk Drives

Industrial Presenter: Ferdinand Hendriks, Hitachi GST

The ability to follow data tracks in today’s fastest spinning hard disk drives is strongly limited by high-frequency aerodynamic buffeting of the – typically non-streamlined - arm and suspension carrying the magnetic read/write transducer. The offending displacements are minute: of the order of a few nanometer. An effective way to combat aerodynamic buffeting of the arm is to provide a region of low flow energy in its immediate surroundings without much increase in the drive’s spindle power. This can be done by diverting the airstream ahead of the arm and reintroducing it downstream from the arm in order to conserve flow momentum (bypass approach). The air diversion process can be enhanced with a flow diverter placed between adjacent disks. However, complete blockage of air flow to the slider-arm region is not viable for reasons of manufacturability. The goal of the week is to come up with efficient (high drag) shapes for the flow diverter.

Figure 1: Top: Ultrastar 15K147 disk drive. Bottom: Comparison of pressure field for a Ultrastar 15K147 disk drive. Notice that the pressure amplitude is lower with the partial bypass, and the vortex shedding from the arm has been reduced. From the ISPS 2005 conference in Santa Clara, CA, in collaboration with Andre Chan.