1. STEADY-STATE AIRFLOW AND PARTICLE TRAJECTORIES INSIDE A HARD DISK DRIVE CHANCHAL SAHA THESIS PRESENTATION

2. Contents Background 1 Objectives 2 Model analysis 3 Conclusions 4

3. 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

4. Current practice

5. OBJECTIVES Airflow without filter Airflow with filter P article trajectory F actorial analysis V elocity, residence time & travel distance relationships Verification

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

7. Objectives Airflow without filter Airflow with filter Particle trajectory Factorial analysis Velocity, residence time & travel distance relationships Verification

8. Airflow model without filter medium 0 m/s 4 m/s 10 m/s 18 m/s 14 m/s Z-axis

9. Objectives A irflow without filter A irflow with filter P article trajectory F actorial analysis V elocity, residence time & travel distance relationships V erification

10. Airflow model with filter medium Filter inlet interface Filter Filter outlet interface

11. Airflow model with filter medium

12. Velocity plot at filter interfaces Filter inlet normal velocity Filter out normal velocity

13. Objectives A irflow without filter A irflow with filter P article trajectory F actorial analysis V elocity, residence time & travel distance relationships V erification

14. Particle injection position Center diameter Mid diameter Outer diameter Near filter cavity Near actuator arm Near filter medium

15. 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 Trajectory models Diameter 0.1 & density 1050 Diameter 0.1 & density 2100 Diameter 0.3 & density 1050 Diameter 0.3 & density 2100

16. 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/m 3 Injected particles: 4 D iameter:.1 to.3 μm D ensity: 2100 kg/m 3 I njected particles: 4

17. Model-2 Diameter:.1 to.3 μm Density: 2100 kg/m 3 Injected particles: 6 D iameter:.1 to.3 μm D ensity: 2100 kg/m 3 I njected particles: 6 Touch filter inlet interface: none Trajectory: mostly around injection points Settle downs: either there or bottom of base boundary near cavity

18. DISCUSSIONS: TOP DISK LEVEL

19. Discussions: base disk level

20. Discussions: near actuator arm

21. 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 airflowairflow Base disk: an inward-outward airflowairflow High velocity flow from outlet interface

22. Objectives A irflow without filter A irflow with filter P article trajectory F actorial analysis V elocity, residence time & travel distance relationships V erification

23. Factorial analysis Filter medium model: 2-level, 3-factor, and 3-replicate factorial analysis Pressure and velocity magnitude data across filter interfaces 24 runs 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 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/m 4 Viscous resistance: 637.82 kg/m 3 -s Input parameters Low level parameters Porosity: 0.4 Inertial resistance: 28.842 kg/m 4 Viscous resistance: 158.13kg/m 3 -s

24. Outcome Porosity Low level (0.4) is suitable for pressure drop High level (0.8) is preferable for face velocity lift Inertial resistance No impact on pressure drop and face velocity lift across filter interfaces Viscous resistance High level (637.82 kg/m 3 -s) is a good choice

25. Objectives A irflow without filter A irflow with filter P article trajectory F actorial analysis V elocity, residence time & travel distance relationships V erification

26. AIR FLOW MODELVERIFICATION Study Disk size (cm) Rotation speed (rpm) Maximum velocity (m/s) Ding & Kumar4.842008.9 Ding & Kumar9.5720018.1 Song, Murali, & Ng, (2004) 10540026.4 Current study6.5540018.403 Current study6.5720024.54 Here, f=5400/60=90 rps r=0.0325 m = 565.488 radian/s V = 565.488×0.0325 m/s V = 18.4 m/s Calculation: Airflow model without filter medium Airflow model with filter medium Velocity lift Pressure drop Energy gain Energy loss Energy balance Bernoulli’s equations Ding, W., & Kumar, M. Bloomington: Donaldson Co. Inc. Song, H., Murali, D., & Ng, Q. Y. (2004). Massachusetts: DSpace@MIT. Reference

27. Trajectory model verification… ParametersSong, Murali, & Ng, (2004)Current study Diameter (μm) 0.1 to 0.5 Injection point OD, MD & CD No. of Particles 99 Material (kg/m 3 ) TitaniumFerretic stainless steel (1050) Disk speed 5400 Disk size (cm) 106.5

28. Conclusions Without filter medium airflow model Linearly increase of velocityvelocity Base disk has higher velocityvelocity Filter medium airflow model Higher velocity at bottom and leftvelocity Higher pressure at right corner of interfacespressure Particle trajectory model Follow directions of airflow modeldirections Travel in a random patternpattern Scarcely touch FIItouch Base disk injected particles have higher tendency to touch FIItouch

29. 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

31. 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/m 3

32. EXPERIMENTAL SETUP ParametersValues Disk drive unoccupied space volume (mm 3 ) 23783 Disk rotational velocity (RPM) 5400 Disk diameter (mm)65 Disk thickness (mm)1.25 Space between two disks (mm) 1.94 Rotor diameter (mm)30 Filter medium specifications (mm) 15×7.65×2.05 Filter medium inlet interface (mm 2 ) 64.579 Filter medium outlet interface (mm 2 ) 56.191

33. VELOCITY PLOT Top disk Base disk

34. PARTICLE TRAJECTORY MODEL Names of Injector parametersSpecificationValues InjectorPart injector3 to 5 points Particle specification Constant density1050 & 2100 kg/m 3 Constant diameter0.1 & 0.3 μm Flow rate distributionTotal inclusion probability1 Flow rate specificationParticle flow rate1 /sec Velocity SpecificationComponentsVelocity field function Model assumption: Particle material: ferretic stainless steel (UNSS44600) R ound shape particle I njection point: over top and base disks surface level M odel run on step mode

35. PARTICLE TRAJECTORY MODEL… Two models 1.Near filter medium injected particles 2.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 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