STEADY-STATE AIRFLOW AND PARTICLE TRAJECTORIES INSIDE

A HARD DISK DRIVE

CHANCHAL SAHA

THESIS PRESENTATION

Contents

Background1

Objectives2

Model analysis3

Conclusions4

Background

Hard disk drive

• Data storage device

• Data read-write ability

• Form factor

Performance

• Disk rotational speed

• Head positioning accuracy

Degradation factor

• Contaminated particles

• Sliding born : 14 to 200 nm

• Manufacturing-born: near few microns

Current practice

OBJECTIVES

• Airflow without filter

• Airflow with filter

• Particle trajectory

• Factorial analysis

• Velocity, residence time & travel distance relationships

• Verification

How did we proceed?Reverse engineeringCAD modelMesh modelAirflow modelParticle trajectory model

Objectives

• Airflow without filter

• Airflow with filter

• Particle trajectory

• Factorial analysis

• Velocity, residence time & travel distance relationships

• Verification

Airflow model without filter medium

0 m/s

4 m/s

10 m/s

18 m/s

14 m/s

Objectives

• Airflow without filter

• Airflow with filter

• Particle trajectory

• Factorial analysis

• Velocity, residence time & travel distance relationships

• Verification

Airflow model with filter medium

Filter inlet interface

Filter

Filter outlet interface

Airflow model with filter medium

Velocity plot at filter interfaces

Filter inlet normal velocity

Filter out normal velocity

Objectives

• Airflow without filter

• Airflow with filter

• Particle trajectory

• Factorial analysis

• Velocity, residence time & travel distance relationships

• Verification

Particle injection position

Center diameter

Mid diameter

Outer diameter

Near filter cavity

Near actuator arm

Near filter medium

Particle trajectory models

• Travel in a circular pattern

• Top disk particles do not touch inlet interface

• Top disk particle trajectory behavior

• Base disk particles enter inside cavity, very rare touch interface

• Base disk particles trajectory behavior

Trajectory models•Diameter 0.1 & density 1050• Diameter 0.1 & density 2100• Diameter 0.3 & density 1050• Diameter 0.3 & density 2100

• Touch filter inlet interface: none

• Travel: mostly over rotating disks

• Settle downs: bottom of base boundary

Model-1

• Diameter: .1 to .3 μm • Density: 2100 kg/m3

• Injected particles: 4

Model-2

• Diameter: .1 to .3 μm • Density: 2100 kg/m3

• Injected particles: 6

• Touch filter inlet interface: none

• Trajectory: mostly around injection points

• Settle downs: either there or bottom of base boundary near cavity

DISCUSSIONS: TOP DISK LEVEL

Discussions: base disk level

Discussions: near actuator arm

Touch the filter inlet interface

• Impossible for top disk level injected particles• Very less possibility for base disk level injected

particles

Touch the filter inlet interface

• Impossible for top disk level injected particles• Very less possibility for base disk level injected

particles

Summary on discussions

• Particles movement follow the velocity field vector• Inside the cavity, velocity varies in different depths

Explanation of particles behavior

• Narrow cavity & airflow direction

• Low velocity magnitude

• Top disk: a loop of airflow

• Base disk: an inward-outward airflow

• High velocity flow from outlet interface

Objectives

• Airflow without filter

• Airflow with filter

• Particle trajectory

• Factorial analysis

• Velocity, residence time & travel distance relationships

• Verification

Factorial analysis

Filter medium model:• 2-level, 3-factor, and 3-replicate factorial analysis • Pressure and velocity magnitude data across filter interfaces• 24 runs

• Factorial analysis for pressure drop data• Factorial analysis for face velocity lift data

OUTCOME

High level parameters

• Porosity: 0.8• Inertial resistance: 125.81 kg/m4

• Viscous resistance: 637.82 kg/m3-s

Input parameters

Low level parameters

• Porosity: 0.4• Inertial resistance: 28.842 kg/m4

• Viscous resistance: 158.13kg/m3-s

Outcome

PorosityPorosityLow level (0.4) is suitable for pressure dropHigh level (0.8) is preferable for face velocity lift

Inertial Inertial resistanceresistance

No impact on pressure drop and face velocity lift across filter interfaces

Viscous Viscous resistanceresistance

High level (637.82 kg/m3-s) is a good choice

Objectives

• Airflow without filter

• Airflow with filter

• Particle trajectory

• Factorial analysis

• Velocity, residence time & travel distance relationships

• Verification

AIR FLOW MODELVERIFICATION

Here, f=5400/60=90 rps r=0.0325 m

= 565.488 radian/s

V = 565.488×0.0325 m/sV = 18.4 m/s

Calculation:

Airflow model without filter medium

Airflow model with filter medium

Bernoulli’s equations

• Ding, W., & Kumar, M. Bloomington: Donaldson Co. Inc.

• Song, H., Murali, D., & Ng, Q. Y. (2004). Massachusetts: DSpace@MIT.

Reference

Trajectory model verification…

Conclusions

Without filter medium airflow model

• Linearly increase of velocity

• Base disk has higher velocity

Filter medium airflow model

• Higher velocity at bottom and left

• Higher pressure at right corner of interfaces

Particle trajectory model

• Follow directions of airflow model

• Travel in a random pattern

• Scarcely touch FII

• Base disk injected particles have higher tendency to touch FII

Acknowledgements

• Special thanks• Industrial System Engineering• Centre of Excellence-Nanotechnology• Donaldson Company

•Admiration and gratitude• Dr. H.T. Luong• Prof Joydeep Dutta• Dr. Pisut Koomsap• Mr. Dan Tuma

• Sincere thanks • Faculty members, staff and students of ISE

• Deepest acknowledgement • Family and friends

Recommendations

• Use very high configuration computer

• Mesh size should be improved & mesh type can be changed

• Physics parameter level can be increased

• Geometric size & position can be changed

• Volumetric airflow and PCU time

• Varying disk speeds & removal of disk separator

• Particle sizes and diameters should be varied more

• One test run:

Particle injection position: top disk-MD, size:10μm & density:7000 kg/m3

EXPERIMENTAL SETUP

VELOCITY PLOTTop disk Base disk

PARTICLE TRAJECTORY MODEL

PARTICLE TRAJECTORY MODEL…

Two models1.Near filter medium injected particles2.Particle injection point similar to PCU test

Trajectory models•Diameter 0.1 & density 1050• Diameter 0.1 & density 2100• Diameter 0.3 & density 1050• Diameter 0.3 & density 2100

24 runs

6 runs