Study of aerodynamic characteristics in hard disk drives by numerical simulation

Shimizu, Hayato; Tokuyama, M.; Imai, Satomitsu; Nakamura, Shinsaku; Sakai, Katsuhiro

doi:10.1109/20.917625

Cited by 52 publications

(26 citation statements)

References 4 publications

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“…The flow outside the HDI gap region is in the continuum regime and hence an appropriate multi-scale method is required to couple the continuum solutions to the DSMC solutions within the HDI region. The global airflow characteristics outside the HDI gap in the HDD enclosure have been previously investigated by various researchers [1][2][3][4] using conventional continuum flow models based on the incompressible Navier-Stokes (NS) equations. Previous applications of DSMC to compute flow within the HDI gap include those by Alexander et al [5] and Huang et al [6].…”

Section: Introductionmentioning

confidence: 99%

Computation of head–disk interface gap micro flowfields using DSMC and continuum–atomistic hybrid methods

John¹,

Damodaran²

2009

Numerical Methods in Fluids

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SUMMARYThis paper discusses computational modeling of micro flow in the head-disk interface (HDI) gap using the direct simulation Monte Carlo (DSMC) method. Modeling considerations are discussed in detail both for a stand-alone DSMC computation and for the case of a hybrid continuum-atomistic simulation that couples the Navier-Stokes (NS) equation to a DSMC solver. The impact of the number of particles and number of cells on the accuracy of a DSMC simulation of the HDI gap is investigated both for twoand three-dimensional configurations. An appropriate implicit boundary treatment method for modeling inflow and outflow boundaries is used in this work for a three-dimensional DSMC micro flow simulation. As the flow outside the slider is in the continuum regime, a hybrid continuum-atomistic method based on the Schwarz alternating method is used to couple the DSMC model in the slider bearing region to the flow outside the slider modeled by NS equation. Schwarz coupling is done in two dimensions by taking overlap regions along two directions and the Chapman-Enskog distribution is employed for imposing the boundary condition from the continuum region to the DSMC region. Converged hybrid flow solutions are obtained in about five iterations and the hybrid DSMC-NS solutions show good agreement with the exact solutions in the entire domain considered. An investigation on the impact of the size of the overlap region on the convergence behavior of the Schwarz method indicates that the hybrid coupling by the Schwarz method is weakly dependent on the size of the overlap region. However, the use of a finite overlap region will facilitate the exchange of boundary conditions as the hybrid solution has been found to diverge in the absence of an overlap region for coupling the two models.

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Section: Introductionmentioning

confidence: 99%

Computation of head–disk interface gap micro flowfields using DSMC and continuum–atomistic hybrid methods

John¹,

Damodaran²

2009

Numerical Methods in Fluids

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“…Another study also showed that airflow directed towards the outer circumference of the disks collides with the arm, creating a wake region. The velocity profile is distorted and causes pressure fluctuation [3]. The pressure difference created between the upstream and downstream of the arm and between pairs of facing suspensions cause disk vibration.…”

Section: Past Work On Hdd's a Flow-induced Vibration (Fiv)mentioning

confidence: 99%

“…The higher rotation speed causes increased airflow turbulence within the HDD and promotes structural vibration of the interior HDD components [3]. The vibration of the HDD arm and Head Gimbal Assembly (HGA) reduces the positioning accuracy of the magnetic head and results in track misregistration (TMR) and HDD errors [1].…”

Section: Introductionmentioning

confidence: 99%

Structure Optimization Study of Hard Disk Drives to Reduce Flow- Induced Vibration

Ng¹

2011

TONUMJ

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Abstract:In this paper, the effects of two flow-induced vibration (FIV) mitigation components on hard disk drive (HDD) airflow, vortex splitters and flow diverters, were verified. The edges of the components were also modified by filleting and the resulting effect on airflow determined. A perspective review on HDDs and their operation, and the mechanism and mitigation of FIV was discussed. Three suitable turbulent models from the commercial fluid flow solver FLUENT were briefly compared. A preliminary study was then carried out on a simplified HDD model to determine the mesh fineness required in HDD turbulent flow simulation in order to obtain accurate results. Another study was done to compare between the RNG k-and LES turbulent models in FLUENT. A full 3.5 inch commercial HDD model was used and results indicated that the LES model was suitable for turbulent flow modelling of a HDD. Lastly, flow simulation of three HDD models with different FIV mitigating features was carried out. Results showed that flow diverters are effective in reducing airflow turbulence in HDD for Re of 12.5x10 4 . The modification and filleting of component edges to make them more aerodynamic streamlining was shown to be less effective but further studies should be done to conclude on the effectiveness of filleting. An optimized HDD structure which includes both vortex splitters and flow diverters, with the filleting of component edges recommended but not mandatory was proposed.

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“…Ng et al [16] performed CFD calculations using CFX-5, Shimizu et al [17] used large eddy simulation (LES) to study flow induced disk flutter, and Shimizu et al used LES to study the airflow induced vibrations of the HGA. Tsuda et al [18] report DNS results, while Tatewaki et al [19] report LES results of airflows in realistic disk drives.…”

Section: A Prior Researchmentioning

confidence: 99%

A Study on the Efficacy of Flow Mitigation Devices in Hard Disk Drives

Kirpekar

Bogy

2006

IEEE Trans. Magn.

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We report on large eddy simulations of the turbulent flow of air in hard disk drives (HDDs) using a commercial CFD code. In particular, we focus on HDD casings in which flow-induced vibrations are reportedly reduced by small geometrical modifications. The modifications investigated are M1: a blocking plate situated between the disks, M2: a spoiler (or deflector) located behind (downstream of) the actuator arm, and M3: a similar deflector upstream of the arm. We observed that M1, M2, and M3 significantly modify the mean flow patterns in the drives. M1 reduces velocity magnitudes in most parts of the drive, the modification of M2 causes flow reversal in regions close to the hub, while M3 causes the shedding of vortices upstream of the actuator arm. Our analysis points to M1 as the best candidate for mitigating the effects of turbulent airflow. This is because M1 is more effective in reducing the root-mean-square velocity fluctuations near the suspension. M1 is also more effective in reducing the pressure fluctuations near the base-plate and suspension region. This reduction, however, is at the cost of approximately 20% higher windage. Finally, we note that M3 has the adverse effects of increasing velocity and pressure fluctuations and hence is not the ideal candidate for mitigating airflow effects, among the modifications considered here.

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Study of aerodynamic characteristics in hard disk drives by numerical simulation

Cited by 52 publications

References 4 publications

Computation of head–disk interface gap micro flowfields using DSMC and continuum–atomistic hybrid methods

Computation of head–disk interface gap micro flowfields using DSMC and continuum–atomistic hybrid methods

Structure Optimization Study of Hard Disk Drives to Reduce Flow- Induced Vibration

A Study on the Efficacy of Flow Mitigation Devices in Hard Disk Drives

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