Behavior of Micron-Sized Air Bubble in Operating FDBs by Using the Discrete Phase Modeling Method

2013 ◽  
Author(s):  
Y. H. Jung ◽  
G. H. Jang ◽  
K. M. Jung ◽  
C. H. Kang ◽  
H. H. Shin
Keyword(s):  
Fluid Dynamic ◽  
Disk Drive ◽  
Spindle Motor ◽  
Air Bubbles ◽  
Air Bubble ◽  
Discrete Phase Modeling ◽  
Discrete Phase ◽  
The Stability ◽  
Stiffness And Damping ◽  
Oil Injection

Fluid dynamic bearings (FDBs) have been applied to the spindle motor of a computer hard disk drive (HDD) because FDBs provide better dynamical characteristics of lower vibration and noise than ball bearings. However, one of the weaknesses of FBDs is the instability arising from the air bubble in oil lubricant of FDBs. Air bubbles are formed and trapped in oil lubricant by the inappropriate process of oil injection or the external shock. Trapped air bubbles decrease the rotational accuracy and the stability of a rotor-bearing system in such a way to generate non-repeatable run-out (NRRO) and to decrease the stiffness and damping coefficients of FDBs. It is important to predict the path of air bubbles in oil lubricant and to design FDBs in such a way to easily expel air bubbles out of operating FDBs.

Investigation of the 3D Flow in Hemodialysis Venous Air Traps

2014 ◽  
Vol 553 ◽  
pp. 156-161
Author(s):  
Gholamreza Keshavarzi ◽  
Tracie J. Barber ◽  
Guan Heng Yeoh ◽  
Anne Simmons
Keyword(s):  
Fluid Dynamic ◽  
Waste Product ◽  
The Body ◽  
Flow Structures ◽  
Air Bubbles ◽  
Health Issues ◽  
3D Flow ◽  
Air Bubble ◽  
Different Types ◽  
Flow Phenomena

Hemodialysis is an extracorporeal system which removes the waste product from kidneys for patients with kidney failure. Air bubbles within the system can cause several deficiencies to the system, and more importantly serious health issues to the patients. Therefore, different types of air traps (artery and venous side) are situated in the setup to prevent air bubbles passing through the system and being sent to the body. There have been evidence of the air trap deficiency. In order to understand these deficiencies the flow inside these air traps need to be understood. The investigation of the flow structures in air traps allow us to predict the efficiency of the air traps in capturing the air bubbles and preventing them from passing through. Computational fluid dynamic (CFD) has been used to compare the flow inside both these air traps. The results show interesting flow phenomena leading to explanations of the air bubble capturing effect.

Development of High Performance Multi-Lobe Fluid Dynamic Bearings Using a Sintered Material

2007 ◽  
Vol 534-536 ◽  
pp. 1437-1440 ◽  
Author(s):  
Hidekazu Tokushima
Keyword(s):  
High Performance ◽  
Data Transfer ◽  
Sintered Material ◽  
Fluid Dynamic ◽  
Disk Drive ◽  
Spindle Motor ◽  
High Density Recording ◽  
Bearing Stiffness ◽  
Bearing Loss ◽  
Herringbone Grooves

Recently, in spindle motors for hard disk drive (HDD) devices, fluid dynamic bearings (FDB) with herringbone grooves have come to be used instead of ball bearings due to the demand for high density recording of the devices, improvement in the speed of data transfer, and the quietness of the motor. In this study, a 5-lobe bearing with high bearing stiffness using a sintered material, as a new trial, was developed, and the bearing performance was examined by simulated calculations and experiments. As a result, it was clarified that the 5-lobe bearing had the required performance for practical use in the spindle motor for HDD by means of optimizing the bearing’s dimensions. In addition, bearing loss of the 5-lobe bearing is lower than that of the herringbone bearing, and the 5-lobe bearing showed clearly that it is effective in being used in the miniaturization of HDD spindle motors.

Factor Affecting Bubble Creation and Bubble Size

2011 ◽  
Author(s):  
Ammar A. T. Alkhalidi ◽  
Ryo S. Amano
Keyword(s):  
Flow Rate ◽  
Computational Fluid Dynamic ◽  
Bubble Size ◽  
Fluid Dynamic ◽  
Air Bubbles ◽  
Hole Size ◽  
Critical Factors ◽  
Water Pool ◽  
Factors Affecting ◽  
Air Bubble

This paper presents the factors affecting air bubble size when air is injected through a perforated membrane into a water pool. Critical factors that govern the size of air bubbles are the air pressure and the flow rate as well as the hole size of the diffuser membrane. In order to have a better understanding of how bubble size can be affected and what the most effecting conditions are, the study was conducted in a computational fluid dynamic (CFD) investigation, which was validated by the experimental results.

Multi-Stage Deep Drawing Process of Thin Sheets for the Sleeve Housing Component of a Spindle Motor in HDD

2013 ◽  
Vol 389 ◽  
pp. 359-363 ◽  
Author(s):  
S.M. Yeon ◽  
S. Choi ◽  
G.A. Lee ◽  
S.J. Park ◽  
J.H. Kim ◽  
...  
Keyword(s):  
Fluid Dynamic ◽  
Thin Sheet ◽  
Disk Drive ◽  
Spindle Motor ◽  
Low Noise ◽  
Drawing Process ◽  
Forming Process ◽  
Multi Stage ◽  
Metal Forming Process ◽  
Housing Component

High-precision micro-fluid dynamic bearing is the key part in a hard disk drive, as it offers low noise levels, high speeds and high rates of accuracy with low amount of vibration. To enhance the performance, a thin sheet component called sleeve housing are newly adopted in FDB. In this paper, multi-stage sheet metal forming process is utilized to fabricate the sleeve housing component. Multi-stage drawing simulations are conducted to investigate the adequate process parameters preventing wrinkling and tearing. From the simulation result, multi-stage drawing processes are conducted with progressive die sets in order to evaluate the forming accuracy. The results reveal that it is successful to fabricate the sleeve housing component with multi-stage drawing process.

Analysis of the oil injection process in fluid dynamic bearings of the spindle motor of computer hard disk drives

2013 ◽  
Vol 19 (9-10) ◽  
pp. 1465-1474 ◽  
Author(s):  
Yeonha Jung ◽  
Gunhee Jang ◽  
Kyungmoon Jung ◽  
Hokyung Jang
Keyword(s):  
Fluid Dynamic ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Spindle Motor ◽  
Disk Drives ◽  
Injection Process ◽  
Oil Injection

Effect of the Cross-Sectional Shape of Recirculation Channel on Expelling Air Bubbles in the FDBs of HDD Spindle Motors

2014 ◽  
Author(s):  
Y. H. Jung ◽  
G. H. Jang ◽  
C. H. Kang ◽  
H. H. Shin ◽  
J. Y. Jeong
Keyword(s):  
Fluid Dynamic ◽  
Hard Disk Drives ◽  
Navier Stokes ◽  
Air Bubbles ◽  
Navier Stokes Equation ◽  
Cross Sectional ◽  
Air Bubble ◽  
Trapped Air ◽  
Large Pressure ◽  
Fast Flow

Fluid dynamic bearings (FDBs) are applied to most of the spindle motors of computer hard disk drives (HDDs) since FDBs provide better dynamic characteristics, such as lower vibration and noise, than ball bearings. However, a weakness of FBDs is instability arising from air bubbles in the oil lubricant of FDBs. One possible solution to expel the trapped air bubbles out of FDBs is to include recirculation channel (RC). RC is designed to balance the pressures between upper and lower parts of FDBs and to circulate the oil lubricant as well as to expel air bubbles out of FDBs. This paper experimentally and numerically investigates the behavior of the air bubble in oil lubricant of operating FDBs due to the design of the RC. We created the FDBs with transparent cover and performed the experiment to visually observe the behavior of trapped air bubbles. Also, we numerically studied the phenomena of expelling the air bubble. The flow field of FDBs is calculated by the Navier-Stokes equation and the continuity equation. And we numerically explained that large pressure difference between upper and lower regions of RC and fast flow velocity along RC expel the air bubble out of FDBs. This research can be effectively utilized to develop robust FDBs by expelling the air bubbles out of FDBs.

Behavior of a micron-sized air bubble in operating FDBs using the discrete phase modeling method

2014 ◽  
Vol 20 (8-9) ◽  
pp. 1511-1521 ◽  
Author(s):  
Yeonha Jung ◽  
Gunhee Jang ◽  
Kyungmoon Jung ◽  
Chiho Kang ◽  
Hyunho Shin
Keyword(s):  
Modeling Method ◽  
Air Bubble ◽  
Discrete Phase Modeling ◽  
Discrete Phase

The Behavior of Automobile Shredder Residue Chips in a Precalciner for Cement Manufacturing Process

2007 ◽  
Vol 544-545 ◽  
pp. 885-888 ◽  
Author(s):  
Sea Cheon Oh ◽  
Cheol Min Jin ◽  
John Hee Hong ◽  
Woo Teck Kwon ◽  
Soo Ryong Kim
Keyword(s):  
Fluid Dynamic ◽  
Combustion Process ◽  
Finite Rate ◽  
Shredder Residue ◽  
Automobile Shredder Residue ◽  
Discrete Phase Modeling ◽  
Discrete Phase ◽  
Flow Heat ◽  
Cement Manufacturing ◽  
Combustion Behaviors

This paper presents a numerical simulation of Automobile Shredder Residue (ASR) chips motion and combustion in a cement works precalciner. The work was done using the commercial computational fluid dynamic (CFD) code FLUENT. The aim of this work is to develop an understanding of the processes within the percalciner to aid in the prediction of ASR chip aerodynamic and combustion behaviors for its use as an alternative fuel. The effects of the mutual interactions between ASR chips were simulated by discrete phase modeling approach, while ASR combustion was simulated by the finite rate devolatilization models. A useful approach to simulate the characteristics of turbulent gas-particle flow, heat transfer and ASR combustion process in a precalciner has been demonstrated.

scholarly journals Effect of cannulation site on emboli travel during cardiac surgery

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Mira Puthettu ◽  
Stijn Vandenberghe ◽  
Stefanos Demertzis
Keyword(s):  
Cardiac Surgery ◽  
In Vitro Study ◽  
Blood Stream ◽  
Air Bubbles ◽  
Arterial Tree ◽  
Air Bubble ◽  
Cannulation Site ◽  
The Brain

Abstract Background During cardiac surgery, micro-air emboli regularly enter the blood stream and can cause cognitive impairment or stroke. It is not clearly understood whether the most threatening air emboli are generated by the heart-lung machine (HLM) or by the blood-air contact when opening the heart. We performed an in vitro study to assess, for the two sources, air emboli distribution in the arterial tree, especially in the brain region, during cardiac surgery with different cannulation sites. Methods A model of the arterial tree was 3D printed and included in a hydraulic circuit, divided such that flow going to the brain was separated from the rest of the circuit. Air micro-emboli were injected either in the HLM (“ECC Bubbles”) or in the mock left ventricle (“Heart Bubbles”) to simulate the two sources. Emboli distribution was measured with an ultrasonic bubble counter. Five repetitions were performed for each combination of injection site and cannulation site, where air bubble counts and volumes were recorded. Air bubbles were separated in three categories based on size. Results For both injection sites, it was possible to identify statistically significant differences between cannulation sites. For ECC Bubbles, axillary cannulation led to a higher amount of air bubbles in the brain with medium-sized bubbles. For Heart Bubbles, aortic cannulation showed a significantly bigger embolic load in the brain with large bubbles. Conclusions These preliminary in vitro findings showed that air embolic load in the brain may be dependent on the cannulation site, which deserves further in vivo exploration.

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