Design of Semi-Submersible Platform using Computational Fluid Dynamics

This paper reports based on an experimental study to simulate flow due to irregular fluid flow in a semi-submersible platform using computational fluid dynamics. In this paper we use computational fluid dynamics tools which solve simple differential equations and finite volume method (FVM). A turbulence model is considered i.e. large eddy simulation (LES). The semi-submersible model is considered as pontoons, columns, horizontal brace and deck. The pontoons are horizontal placed stadium shaped structures which are submerged into the water. The columns are structures which connect the deck and pontoons in these model circular columns are considered. The horizontal braces are circular tube-like structures which connect the two or more columns which increases the rigidity of the columns. The deck is a flat surface which provides workable area. This paper is a comparison of fluid flow at different velocity magnitude. The velocity contour, pressure contour and streamline contour are simulated and graphically represented. The numerical simulations are compared with experimental solutions and focus on vicinity of the platform. The difference in pressure, temperature and streamline flow are tabulated and graphically represented. The average percentage difference in temperature and pressure are calculated to be 73% and 128% respectively. Thus, the causation is investigated for the case and several governing parameters are recognized.

Performance of pulsed-electrochemical honing and pulsed-electrochemical finishing in improving quality of bevel gears

This article presents a comparative study concerning performance of pulsed-electrochemical honing (PECH) and pulsed-electrochemical finishing (PECF) in straight bevel gear finishing. Performance of these processes were compared in terms of average percentage difference in the considered parameters of surface features of bevel gear namely average percentage differences in average surface roughness ‘PDRa’, maximum surface roughness ‘PDRmax’ and depth of surface roughness ‘PDRz’, micro-geometry (i.e. average percentage differences in single pitch error ‘PDfp’, adjacent pitch error ‘PDfu’, cumulative pitch error ‘PDFp’, and percentage difference in runout ‘PDFr’) and finishing productivity (i.e. material removal rate ‘MRR’). Microstructure and microhardness were also considered as measure for performance assessment. Observed results show PECH is proficient in simultaneously improving all the considered responses of bevel gears by more than 50% as compared to PECF. The PECH-finished gear additionally displayed unrivalled microstructure and better microhardness when contrasted with PECF-finished gear. These changes will upgrade the working-life and operating performance of the finished gear.

SIMULATION OF INTAKE AND EXHAUST VALVE TIMING ON INTERNAL COMBUSTION ENGINE

Internal combustion engine in automotive industry is widely researched to increase its efficiency and power output. Valve system in modern internal combustion engine control the opening and closing timing of intake and exhaust stroke. Its duration affects the performance of the engine at both power output and fuel efficiency. Therefore, this study discusses about the Miller cycle concept that alter the duration of both intake and exhaust valve opening and closing characteristics. The study focusses mainly on finding the optimum timing characteristics on Proton Iriz gasoline engine. A 1-dimensional model has been built using a commercial software called GT-POWER for engine simulation purpose. The engine is then calibrated with the simulation model. The optimization was run in this software to find the best optimum timing of intake and exhaust valve for two categories which are targeting performance and fuel consumption. The results show positive trends in the BSFC results with the maximum percentage difference of 26.27% at 6,250 rpm. The average percentage difference in the BSFC results is 14.12%. For targeting performance, the overall results show an increasing trend in the brake torque curves with maximum percentage difference is 9.83%. The average percentage difference in brake torque is found to be 3.12%. Therefore, this paper concludes that Miller cycle implementation give minimal performance increment. The targeting performance and fuel consumption optimization can also be implement for changing mode of driving. However, the increase compression ratio would also give adverse effects on engine performance and endurance. The Miller cycle is also more suitable to be implement on force induction system.

RANCANG BANGUN SISTEM PENGOLAHAN CITRA DIGITAL UNTUK MENENTUKAN BERAT BADAN IDEAL

In actual fact, there are many people who do not know whether their weight have been ideal or not due to unavailable device or machine that can be used to measure ideal weight practically. Therefore, in order to measure the ideal weight practically, the researcher is attempting to create a system based on image processing which is developed by using Matlab software. As a preliminary step, the researcher collects some samples data that will be used in the research. Furthermore, the calculation formula is analysed by the researcher to be used in the system. This research is using a formula namely Body Surface Area (BSA) with a tubular analogy of human body. Image processing is made by using the edge detection algorithm to know the height and width of objects in an image of the human body. In addition, by certain search algorithm the height and width of object in the image of human body will be known and used for measuring approximate height and weight. Besides, Body Mass Index (BMI) formula is used for measuring ideal weight. the research shows that the value of the average percentage difference deviation of the system is 1.63% for height and 11.6% for weight. At least but not last, for the level of system accuracy reaching up to 75% of the body actual condition by system calculating result.

A method for handlebars ballast calculation in order to reduce vibrations transmissibility in walk behind tractors

Walk behind tractors have some advantages over other agricultural machines, such as the cheapness and the easy to use, however the driver is exposed to high level of vibrations transmitted from handles to hand-arm system and to shoulders. The vibrations induce discomfort and early fatigue to the operator. In order to control the vibration transmissibility, a ballast mass may be added to the handles. Even if the determination of the appropriate ballast mass is a critical point in the handle design. The aim of this research was to study the influence of the handle mass modification, on the dynamic structure behaviour. Modal frequencies and subsequent transmissibility calculated by using an analytical approach and a finite elements model, were compared. A good agreement between the results obtained by the two methods was found (average percentage difference calculated on natural frequencies equal to 5.8±3.8%). Power tillers are made generally by small or medium-small size manufacturers that have difficulties in dealing with finite element codes or modal analysis techniques. As a consequence, the proposed analytical method could be used to find the optimal ballast mass in a simple and economic way, without experimental tests or complex finite element codes. A specific and very simple software or spreadsheet, developed on the base of the analytical method here discussed, could effectively to help the manufacturers in the handlebar design phase. The choice of the correct elastic mount, the dimensioning of the guide members and the ballast mass could be considerably simplified.

An Investigation on Bending Capacity of Support Stiffness Wall-Slab Structural System by Using Single Layer and Double Layer of Rebar for Residential Project

Wall-slab structural system is a system suitable for use in the field of high-rise building where the main load resisting system is in the form rigidly connected wall slab member. Concrete vertical walls may serve both architecturally partitions and structurally to carry gravity and lateral loading. Moment transfer of joint is an important aspect for proper structurally functioning of wall-slab system. Hence, the main aim of this study is to investigate experimentally the effect of reinforcement details in the wall on bending capacity for support stiffness in wall-slab system for residential project in Malaysia. A total of six wall specimens were tested based on the specification given by the project contractor. Three of this specimens consisted single layer of rebar while another three specimen consisted of double layer of rebar. The size of the wall-slab’s specimens is 1000mm in length (L), 1080mm in width (W), 1000mm in height (H) and 80mm in thickness (T). The average concrete strength was 23.49MPa with Grade 30N/mm2 and the average yield strength of R5 bar was 817MPa. The predicted bending capacity at failure is in the range from 5.36kNm to 7.12kNm, depending on actual concrete cover. The bending capacity at failure for single layered of rebar in wall for specimen 1, 2 and 3 were found to be 3.59kNm, 3.81kNm and 3.15kNm, respectively. The bending capacity at failure for double layered of rebar in wall for specimen 1, 2 and 3 were 5.50kNm, 6.31kNm and 7.00kNm, respectively. The average percentage difference in stiffness of double layered of rebar in wall based on load-deflection curve obtained is in the range from 116.17% to 289.88% higher than single layered of rebar in wall. Based on the experimental results, specimens consisted of double layered of rebar in wall is found to provide higher bending capacity to the joint of wall-slab structural system in the range from 56.25% to 98.86% compared with single layered of rebar in wall.