NUMERICAL STUDY OF AIR FLOW IN HARD DISK DRIVES

Abstract

The rotating disk flow model has been studied extensively due to its close relation to the hard disk drive (HDD) assembly. As the speed of rotation of disk increases, the enclosed air in HDD spins faster. This introduces new problems such as vibration and windage loss. The model used in both experiment and simulation is a simplification of HDD configuration in the form of a partially shrouded model. The removal of shroud alters the flow pattern significantly as shown by Yip et al [2003] in terms of velocity magnitude and Reynolds stresses. Using a similar set-up as the reference above, FLUENT models were constructed and computed for the flow pattern and characteristics. The speed of rotation of the corotating disk is set at 10000rpm and computation was carried out to determine the magnitude of velocity and Reynolds' shear stress. From the computation carried out, the flow of corotating disk with obstruction (actuator) shows the presence of Reynolds' stress gradients of opposite sign close to the obstruction. As shown by Tennekes and Lumley [1971], this corresponds directly to the velocity-vorticity fluctuation interaction and contributes towards the fluctuating force acting on the obstructions. Meanwhile, a similar approach in computation for the unobstructed model did not reproduce the experimental results. However, in the model without obstruction, characteristics such as detached shear region and influence of the empty space where the shroud used to be were detected. Therefore, this complex interaction needs to be studied further.