Omar Yaakob

An analysis of shipboard waste heat availability for ballast water treatment

Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, Skudai, Malaysia Heat treatment of ballast water is one of the many treatment options being explored. This analysis has tried to assess the heat availability from the cooling water, exhaust gases of the engines and steam condensers based on design and operational data obtained from an existing crude oil carrier. Time requirements for ballasting and treatment using the seawater and condenser circulating pumps are projected. Heat balance exercises were also carried out on a testbed engine to verify attainable heat recoveries. It is seen that, although considerable heat is available, a longer time than that available during ballasting and normal ballast passages will be required for the treatment process.

Two chambers soft actuator realizing robotic gymnotiform swimmers fin

This paper shows a study on two chambers soft actuator development and its application to an artificial soft actuator fin. Simulations of two chambers actuator are conducted using finite element method software and the bending angles produced are computed. Eleven designs are proposed and compared which differ in separating wall thickness, actuator thickness, fiber location, fiber materials, and rubber materials to analyze the optimal bending angle produced by the actuator. Two actuators are then fabricated and embedded at the ends of soft actuator fin to produce a traveling wave along the soft actuator fin. Soft actuator fin propels like gymnotiform swimmers and shows good linear motion.

Analysis of noise behaviour for marine propellers under cavitating and non-cavitating conditions

In this study, the hydrodynamics and noise behaviour of marine propellers are examined through finite volume method under various operational conditions. The hydrodynamics of these propellers are studied both numerically and experimentally, and the characteristic curves are produced. Sheet cavitation inception and development conditions are also considered in order to understand the impact of different rotational speeds on propeller noise. Ffowcs Williams and Hawkings equations are used to extract the total sound pressure levels under non-cavitating and sheet cavitating conditions. Finally, the impact of cavitation on increasing the propeller noise is thoroughly explored and the results are presented.

Investigation of hydroelastic effect in analysis of high-speed craft

Hydroelastic effect in bottom slamming problem of high-speed craft is one of the most challenging issues in structural design. In this paper, numerical method is used to investigate the hydroelastic effect in bottom-water impact analysis of high-speed monohull craft. Slamming with two viewpoints of rigid and elastic structures (hydroelastic effect) is modelled by coupled computational fluid dynamic (CFD) and finite element method (FEM) techniques. The results showed that considering hydroelastic effect, especially in high-impact speed, reduces the structural deformations and stresses compared with quasi-statistic analysis. The effect of different parameters, such as boundary condition, plate properties, wedge deadrise angle, and impact velocity in slamming problem, was investigated. The results for aluminium and steel plate with the same bending strength showed that dynamic characteristic of plate material is a major parameter in hydroelastic analysis result. Finally, a simplified method is used to apply the effect of hydroelasticity in bottom plate design. This work is hoped to advance the hydroelastic analysis art in bottom structural design of high-speed monohull craft.

Numerical study on interference effects and wetted area pattern of asymmetric planing catamarans

Asymmetrical planing catamarans are increasingly used in moderate to very high-speed applications due to some tempting qualities such as less wetted surface and better seakeeping behavior. The present numerical study attempts to provide new insight into hydrodynamics of such vessels by highlighting the distinguishing aspects and employing novel appropriate approaches to deal with them. A systematic investigation has been carried out on a prismatic geometry at various demihull separations (including zero separation, that is, symmetric monohull) and different trim angles in a wide range of speed coefficients, using a computational fluid dynamics solver. Obtained numerical results of steady-state resistance and lift forces are compared against different empirical methods. In order to offer an adequate explanation about the nature of forces and interference mechanisms, an analysis has been performed on viscous and pressure resistance components. Furthermore, the ability of the employed numerical method in estimation of wetted area pattern at the bottom of the planing hulls has been evaluated to provide explanation for some observed hydrodynamic behaviors of the asymmetric planing catamarans. It is seen that a significant reduction is reached in wetted surface area of catamaran configuration in comparison with corresponding monohull.

Laboratory tests on heat treatment of ballast water using engine waste heat

ABSTRACT Waste heat recovery from shipboard machineries could be a potential source for heat treatment of ballast water. Similar to a shipboard schematic arrangement, a laboratory-scale engine-heat exchanger set-up harvesting waste heat from jacket water and exhaust gases was erected to test the level of species’ mortalities. Mortalities were also assessed under experimental conditions for cultured and natural plankton communities at laboratory level. Effect of pump impellers on species’ mortalities were also tested. Exposures between 60°C and 70°C for 60 sec resulted in 80–100% mortalities. Mortalities due to pump impeller effects were observed in the range of 70–100% for zooplankton. On the laboratory-scale arrangement, >95% mortalities of phytoplankton, zooplankton and bacteria were recorded. It was demonstrated that the temperature of tropical sea waters used as secondary coolant can be raised to cause species’ mortalities, employing engine exhaust gases. The results also indicated that pump impeller effects will enhance species’ mortalities. The limitations of the shipboard application of this method would be the large ballast volumes, flow rates and time for treatment. GRAPHICAL ABSTRACT

Significant wave height assessment using multi mission satellite altimeter over Malaysian seas

Satellite altimeter is one of the useful technique to study the variation of ocean parameters with a good temporal and spatial measurements. In situ measurements such as buoy has own disadvantages in terms of spatial observations. Thus, with the combination of satellite altimeter and buoy can improve the significant wave height measurements for both spatial and temporal over the seas. Generally, the measurement of significant wave height from altimeter using the Ku-band signal, while SARAL is borne with Ka-band altimeter (AltiKa). The aim of this research is to study the reliability of wave height data from the satellite altimeter to support marine renewable energy development. This Significant wave height (Hs) is retrieved from multi mission satellite altimeter by Radar Altimeter Database System (RADS) and evaluated using in-situ measurement over the Malaysian seas (0°N - 14°N and 95°E - 126°E). A validation with selected buoys located at Sabah Sea (5.83 N, 114.39 E) and Sarawak Sea (5.15 N, 111.82 E) is performed by statistical approach and presenting good correlation of 0.92 and 0.18 for RMSE. A climatology assessment is performed by analyzing the condition of significant wave height during monsoons. This paper highlighted, collocation between altimeter and buoy are well-correlated and reliable to use for a marine analysis for renewable energy development.

Hydrodynamic Design of New Type of Artificial Reefs

The purpose of this research work is to study the hydrodynamic characteristics of a new type of artificial reef structure, in order to provide a structure with low flow resistance, which will be a more suitable shelter for fishes and marine organisms. The idea of the new artificial reef is based on the streamlined bicycle helmet design concept. The hydrodynamic characteristics of the helmet and hollow cube artificial reefs (ARs) of the same volume have been studied at different water depths and wave frequencies of Malaysia seas using Computational Fluid Dynamics (CFD) method. The finite volume RANSE (Reynolds-Averaged Navier-Stokes Eqs.) code Ansys CFX was used for calculating the reefs drag force (FD) and flow characteristics, while the potential flow code Ansys Aqwa was used for calculating the reefs inertia force (FI). The Shear Stress Transport (SST) turbulence model was used in the RANSE code. The results of the two ARs were then compared for studying the hydrodynamic improvement due to the use of streamlined helmet artificial reef on the flow pattern around it. The streamlined body of the helmet artificial reef enhances the flow pattern at the aft region of the reef and provides flow zones with moderate flow speed at this area, which can help fishes and marine organisms from finding good shelter. The special shape of the different openings in the body of the helmet artificial reef improves the condition of the flow velocity distribution inside the unit than that of the hollow cube unit, which can increase the amount of the nutrient to the living fishes and organisms inside the reef.

Experimental analysis of podded propulsor on naval vessel

This paper describes the effect of pod propulsor attachment to the existing Naval Vessel hull form which was designed for conventional propulsor in aspects of resistance and motion characteristics. These investigations were carried out on a 3.0 m model by experimental works in the towing tank 120m x 4m x 2.5m at the Marine Technology Centre (MTC), Universiti Teknologi Malaysia (UTM). The basis ship chosen for this study is Sealift class type MPCSS (Multi Purpose Command Support Ship). In this study, the design for the new pod propulsor is based on a proven design and scaled down to suit this type of hullform accordingly. This paper describes the resistance comparison between bare and podded hulls in calm water as well in waves. The seakeeping test for hull with and without pod in regular waves at service speed of 16.8 knots were carried out at wavelength to model length ratio, Lw/Lm between 0.2 and 1.2. The outcomes from this experimental works on hull with and without pod were compared.

Use of CFD to Study the Resistance of Sprint Master Canoe

The resistance and the hydrodynamic characteristics of the Sprint Master canoe that is used in Universiti Teknologi Malaysia (UTM) have been studied at different speeds using Computational Fluid Dynamics (CFD) method. The resistance of the canoe at different speeds has been measured in UTM marine technology center (MTC). The finite volume code Ansys CFX has been used for carrying out the numerical simulations for the hull form of the canoe at the same experimental speeds. The Volume of Fluid method (VOF) has been used with Ansys CFX for capturing the free surface flow around the canoe hull at the same experimental speeds. The Shear Stress Transport (SST) turbulence model has been used in the RANSE code. The grid generator ICEM CFD has been used for building the grids for the RANSE code solver. The numerical results compare very well with the experimental results at the different speeds.