Optimum Design of Thrust Oil Bearing for Hard Disk Drive

This paper presents the application of optimization method developed by Hashimoto to design oil lubricated thrust bearing for 2.5 inch form factor hard disk drive (HDD). The designing involves optimization of groove geometry and dimensions. Calculation is carried out to maximize the dynamic stiffness of the thrust bearing spindle motor. Static and dynamic characteristics of the modeled thrust bearing are calculated using the divergence formulation method. Results show that by using the proposed optimization method, dynamic stiffnesses values can be well improved with the bearing geometries not being fixed to conventional grooves

Macro-surface Modification through Exploitation of Rivets and Dimples –Numerical and Experimental

Research related to rivets and dimples has been conducted as early as the 1930s. The irregularities of surfaces have believed to be a factor to fuel consumption increase of airplanes. NASA reported that it is vital to eliminate the surface irregularities or other protuberances from the surface that is exposed to the airflow [1]. This is believed to due to the extreme increase of the drag coefficient

Radiant Times Series (RTS) For Equatorial Climates

Air conditioning units are the most significant energy user in a building. Therefore, an accurate cooling load calculation is important to optimize the design of these air conditioning units for a better system for the building energy load. American Society of Heating, Refrigerating and Air Conditioning (ASHRAE) has developed a method called Radiant Times Series (RTS) to improve the accuracy of cooling load calculation. There are several traditional cooling load calculation methods commonly practiced by designers in Malaysia especially Rules of Thumbs, CLTD (Cooling Load Temperature Difference) and TFM (Transfer Function Method). Designer may considered higher safety factor for conventional method because of constraint in initial parameter consideration, thus this will promote higher loading and over designed air conditioning system. This study will discuss the various types of cooling load methods in equatorial climates (hot and humid), where buildings in Malaysia is used as a subject in this paper. The results would be useful for Mechanical, Ventilation and Air Conditioning (MVAC) designer to consider and design a better and optimum system for the building. The finding shows that the huge convocation hall with estimated occupant of 5000 tenants shall be design between the ranges of Cooling Load per Square Feet, of 70 Btu/Hr.ft2 to 125 Btu/Hr.ft2 based on RTS method and CLTD method respectively. Meanwhile, for office building the design shall be between the ranges of Cooling Load per Square Feet, of 33.81 Btu/Hr.ft2 to 46.79 Btu/Hr.ft2 based on RTS method and CLTD method respectively. These values are to be achieved comfort cooling for the respective building. The results also showed that the accuracy of cooling load will be determined by the considered parameter of the cooling load methods. It's important to use this method in Malaysian perspectives because of the accuracy and recommended for other hot and humid countries

HDDs with Better Heat Dissipation Systems Designed for Search Engines Servers

The usage of search engines such as Google, Yahoo and Bing for information seeking is inevitable and important for our daily lives. Google claims that users conduct over a billion searches a day, not including numerous downloads and queries. These search engines have hard disk drives (HDDs) as their core part for data storage. HDDs operating on average 7,200 rotation per minute (rpm) are the norm. However, high-end HDDs meant for fast responses and feedbacks require higher rotational speed and higher track density. These type of HDDs simultaneously need smart countermeasures for excessive heat rise; HDDs’ flow-induced vibration (FIV) such as arm vibrations and disk flutters, without increasing its power consumptions. Gigantic search engines or even cloud computing servers used in nowadays smart computing actually involve numerous HDDs to store these data and information for our convenience. By decreasing the heat generated by these vital core parts of the servers; the HDDs, the authors aim at a lesser energy consumption HDD. Out of the total energy consumed by these servers, only 40 to 45 percent are being used for operation. The remaining energy is consumed for cooling the server and database systems. In this paper, the authors propose a new actuator arm with a better window that will improve the heat dissipation of the HDDs system. The HDD’s actuator arm is designed using AutoDesk and exported to Comsol Multiphysics for numerical simulation. Each arm has a large windowed area for a better dissipation of heat generated due to air frictions. Another improvement that the authors proposed is by designing a novel S-shaped arm to promote better air flow. This will eventually lead to less heat generating HDDs meant for search engines servers of the internet

Measurements of Film Thickness and Pressure Distribution for Optimized Thrust Air Bearing

In this paper, we describe the film thickness and pressure measurement of the optimized thrust air bearing. In our recent study, a new optimization technique of the bearing groove geometry of the hydrodynamic thrust air bearings was proposed and a new groove geometry having a bending curve in outer vicinity of the bearing surface was obtained. Furthermore, in this study, the drastic improvement of the bearing dynamic stiffness was verified by the dynamic characteristic experiment using the original high-speed bearing test rig. However the relative error of the film thickness between the theory and experiment is large compared with that of dynamic stiffness. Consequently, it has been considered that the improvement of the measurement accuracy for film thickness is one of the most important problems. On the other hand, the generation of the negative pressure on the optimized bearing surface has not been confirmed experimentally, and it is also important to verify the negative pressure generation by measurement. Therefore, in this study, we examined the improvement of the measurement accuracy of the film thickness and the pressure measurement of the optimized bearing. As a result, the accuracy of air film thickness is drastically improved applying a newly proposed compensation method and the negative pressure on the optimized bearing can be found experimentally

Streamlined vessels for speedboats: Macro modifications of shark skin design applications

Functional properties of shark denticles have caught the attention of engineers and scientist today due to the hydrodynamic effects of its skin surface roughness. The skin of a fast swimming shark reveals riblet structures that help to reduce skin friction drag, shear stresses, making its movement to be more efficient and faster. Inspired by the structure of the shark skin denticles, our team has conducted a study on alternative on improving the hydrodynamic design of marine vessels by applying the simplified version of shark skin skin denticles on the surface hull of the vessels. Models used for this study are constructed and computational fluid dynamic (CFD) simulations are then carried out to predict the effectiveness of the hydrodynamic effects of the biomimetic shark skins on those models. Interestingly, the numerical calculated results obtained shows that the presence of biomimetic shark skin implemented on the vessels give improvements in the maximum speed as well as reducing the drag force experience by the vessels. The pattern of the wave generated post cruising area behind the vessels can also be observed to reduce the wakes and eddies. Theoretically, reduction of drag force provides a more efficient vessel with a better cruising speed. To further improve on this study, the authors are now actively arranging an experimental procedure in order to verify the numerical results obtained by CFD. The experimental test will be carried out using an 8 metre flow channel provided by University Malaysia Sarawak, Malaysia. © 2018 Author(s)

Macro-Surface Modifications of Subsonic Flow on Airplane Winglets

Airplane winglets are used to improve the efficiency and noise or vibrations of fixed-wing aircraft. In this paper, the surface modification involves alteration on surface’s features to improve the performance of a product is being conducted. The surface modification was implemented on winglet surface in order to investigate whether the modified winglets provide better performance or not compared to the conventional wing designs. Two types of models were used which is a rectangular plane and airplane winglet, each with different types of surface modifications. For rectangular plane, four surfaces were introduced which is smooth plane, dimpled plane, riveted plane and extruded rivet plane. As for winglets, three surfaces were used which is the smooth winglet, dimpled winglet and riveted winglet. The parameters used for the simulations were based on the actual cruising flight and zero degree angle of attack. From the results, both show that the surface with rivets is better. The flow trajectories show that the flow velocity across riveted surface modified winglet is 5% higher than the smooth conventional winglet