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An autonomous underwater glider speed and range is influenced by water currents. This is compounded by a weak actuation system for controlling its movement. In this work, the effects of water currents on the speed and range of an underwater glider at steady state glide conditions are investigated. Extensive numerical simulations have been performed to determine the speed and range of a glider with and without water current at different net buoyancies. The results show that the effect of water current on the glider speed and range depends on the current relative motion and direction. In the presence of water current, for a given glide angle, glide speed can be increased by increasing the net buoyancy of the glider.

Now a day, increasing energy demand and environmental effect of fossil fuel cause to replacing fossil fuel with renewable energy. This paper presented novel design of turbine to generate more torque to capture more energy of water and hence cause to high output power. In this work Computational Fluid Dynamics (CFD) using realize k-e turbulence model, have been used to analyses the effect of arm on the static torque and the contours of pressure in different angle of direction for vertical vane turbine. Investigation of arm effect on static torque of vertical vane turbine and comparison between turbine with arm and without arm showed the average torque in vertical vane turbine is higher than without arm. The model settings of validation study was accomplished by comparing simulation of performance of turbine Cp and Cm with the experimental data taken from Hayashi and Hara (2005),that showed realize k-e has good agreement with experimental data.

This paper numerically investigated the hydrodynamic resistance of Multipurpose Amphibious Vehicles (MAV) in three bow shapes to approach the better hull bow shape design. This type of vehicle and other blunt-shaped floating vehicles encounter the problem of a large bow wave forming at high speeds. This wave formation is accompanied by higher resistance and at a critical speed results in bow submergence or swamping. Three new shapes of hull bow design for the multipurpose amphibious vehicle were conducted at several speeds to investigate the hydrodynamic phenomena using Computational Fluid Dynamics (CFD, RANS code) which is applied by Ansys-CFX14.0 and Maxsurf. The vehicle’s hydrodynamic bow shapes were able to break up induced waves and avoid swamping. Comparative results with the vehicle fitted with U-shape, V-shape and Flat-shape of hull bow, showed that the U-shape of the hull bow has reduced the total resistance to 20.3% and 13.6% compared with the V-shape and flat shape respectively. Though, the U-shape of hull bow is capable to increase the amphibious operating life and speed of vehicle in calm water. Also it has ability to reduce the vehicle’s required power, fossil fuel consumption and wetted hull surface.

Wake wash has become a significant issue in the ship design industry due to its impact on the environment in terms of erosion of natural shoreline wetlands. Many ideas for reducing wake wash have been introduced. This research work presents the development of a low wake wash catamaran hull form. In particular, the study is focused on the effectiveness of specially designed fin in order to reduce the wake wash produced by the ship. The fin was attached vertically along the centerline of the catamaran model and the model was tested in the towing tank of Marine Technology Center (MTC) to assess its wake wash. The fin was located at three different positions, which are at bow, center and stern of the ship. The results based on wave height measurements at the various fin locations showed that the fin located at the stern position produces lower wake wash compared to other positions.

The presentarticle focuses on the hydrodynamic resistance reduction of Multipurpose Amphibious Vehicles (MAV) usingthe air lubrication layer effect. The use of air cushions to support marine vehicles, heavy floating structures and in other operation is well known. The main problem in Multi-purpose Amphibious Vehicles (MAV) is the amount of power needed in order to overcome the hydrodynamic resistance acting on the hull which is included the frictional and pressure resistances. Therefore, more power is needed to move the MAV forward. In this respect, more fuel will be required to operate the amphibious vehicles. This problem could be effectively reduced by the introduction of the air cushion concept. With the air being drawn from top of craft to the cavity below the hull will produce some cushioning effect and also help to reduce skin friction drag. In this paper, air cushion effect will be studied in rigid surface cavity instead of using flexible skirts. This would avoid the problem of high maintenance due to replacement of damaged skirts. Finally, the MAV will be supported using air cavity and bubbles generated by an air pump (compressor and air pressure vessel) to pushes the hull of multi-purpose amphibious vehicle up and reduce the frictional resistance due to draft and wetted surface reduction and layer of air between hull surface and water. This research would be done via CFD (ANSYS-CFX 14.0) and analyzed the hydrodynamic resistance.

Hydropower energy is one of the most suitable and efficient source of renewable energy which depends on more than century of experience for this issue. The power capacity and facility are two criteria required for the classification of hydropower plant. The first one consists of five technologies: dammed reservoir, run of river, pumped storage, in stream technology and new technology gravitational vortex. The other one is classified according to power scale is Large, Small, Mini, Micro and Pico Hydropower. Nowadays most of rural areas in developed and developing countries use the hydropower plant for producing electricity, it is cheap and effective. This paper gives a review of hydropower technologies and turbines; it is focusing on the categories and performance of hydro power systems and the most suitable turbines which can be used.

In order to lower down the fuel consumption and to achieve higher speed of ship, reduction in ship resistance has been the major topic of research for a long time. The most important factor in ship resistance is skin friction resistance. Micro-bubble has been shown to be able to reduce skin friction. This micro-bubble method gives the possibility to lower the friction without any change in the present hull form of a ship. The application of the micro-bubble technique reduces the surface friction by a variation of the viscosity of the fluid around the ship and makes a modification in the structure of the turbulent boundary layer. However, not much is known about the correct size, quantity, area of coverage which can effectively form a skin friction reducing mechanism. There are many established methods, such as Venturi tube type generator, tangential water-jet and forming of dissolve air and also a chemical process, such as electrolysis, may result in bubble production [1]. The use of micro-bubble as reducing agent of drag can lead to the creation of bubbly mixture near the flow surface that can significantly advances in the understanding of the underlying physical process of drag reduction. The current applications of these techniques to surface ships are discussed.

Demand on High Speed Craft (HSC) is increasing due to development of inland transportation. Therefore, many analysis have been conducted to evaluate performance of this modern ship. One of the important analysis is calm water resistance test. Resistance component of the hull and wave pattern around the hull are obtained from the calm water test. These criteria are important in analyzing flow around hull, especially on wave interference between the hulls. In this paper, flow around hull has been studied for one model of Semi SWATH hull form with fin stabilizers installation by performing calm water resistance test in deep water. The fore fin angle is fixed to zero degree while the aft fin angle is varied to 0, 5 and 15 degree. The effects of fin angle to resistance criteria and flow around hull are investigated. Wave height has been recorded using longitudinal wave probe during resistance test. For each configuration, the investigation is conducted with range of Length Froude Number from 0.34 to 0.69. From the analysis, it is found that flow around the hull of Semi SWATH is affected by fin angle and the effect is various depend on the Froude number.

Reynolds Averaged Navier-Stokes (RANS) computations are conducted with general purpose CFD solver Fluent to examine the resistance and viscous free surface flow of Liquefied Natural Gas (LNG) carrier hull form in calm water. Shear-stress transport k-w turbulence model and multiphase volume of fluid (VOF) free surface employed. The resistance characteristics and wave profile of the LNG model also investigated. Model tests were conducted in towing tank for validation of the computed results. Overall results agree fairly well with experimental data, reveals the feasibility of RANS method in practical prediction of LNG resistance characteristics.

Remotely operated underwater vehicles which are also known as ROVs are a type of underwater robot vehicle which is widely used in the offshore industry or other applications. The main purpose of this type of tethered underwater mobile robots are tosupersede human to work at hard-to-access or jeopardizing underwater region to do certain specific tasks like to survey a site, search for an item or person that has tremendous value. The remote control of ROV is usually carried out through copper or fiber optic cables which are known as umbilical cables. In this research work a low cost ROV unit has been designed and constructed at UniversitiTeknologi Malaysia (UTM). The ROV was constructed by low cost material like commercial grade polyvinyl chloride (PVC) pipes. The low cost ROV is equipped with a network camera and manoeuvred by three motors through 12 volts battery power supply. The ROV is controlled by joystick controller through network cable and is able to submerge up to 20meters intowater to perform underwater observation operation.

Study of vibrations due to vortex shedding (VIV) in the wake of a cylinder that is exposed to current or oscillatory flow is very important, especially for marine risers which are used to extract oil and gas from the sea bed. The phenomenon of vortex induced vibration (VIV) has been one of the major concerns for hydrodynamic researchers due to its potential ability to cause severe fatigue damage. The hydrodynamics of VIV is very complex and still not fully understood. In this paper, some results (amplitude over diameter, lift and drag coefficients) of high Reynolds VIV experiments that are performed in UTM towing tank with an in-house test set-up are presented. A circular cylinder of 114 mm in diameter and 3 min length was towed at constant speed through the basin at Reynolds numbers up to 1.1x105. Model tests with a stationary cylinder and tests with a freely vibrating cylinder were carried out to investigate the influence of VIV on drag coefficient. Later these results are compared with results obtained through 3D numerical simulation, LES is used to solve turbulence flow. It was found that CFD results showed similar trends with experimental results. Results of this paper can be very important to design riser system and future endeavor to perform similar kind of experiments. Successful numerical study of the VIV can also be fruitful for designing efficient VIV suppression devices.

Marine propeller blade geometries, especially LNG carriers, are very complicated and determining the hydrodynamic performance of these propellers using experimental work is very expensive, time consuming and has many difficulties in calibration of marine laboratory facilities. This paper presents the assessment on the effect of turbulent model and mesh density on propeller hydrodynamic parameters. Besides that, this paper focuses on the LNG carrier Tanaga class propeller hydrodynamic performance coefficients such as Kt, Kq and η, with respect to the different advance coefficient (j). Finally, the results from numerical simulation that were calculated based on RANS (Reynolds Averaged Navier Stocks) equations, were compared with existing experimental results, followed by analysis and discussion sections. As a result the maximum hydrodynamic propeller efficiency occurred when j=0.84.

Generated wave pattern of twin hull ship is important in analyzing wave interference between hulls. As each hull will generate own wave pattern, which might be identical for both hulls, the interference of wave generated can be either amplification or reduction factor for wave making resistance of the twin hull ship. Free Surface Flow is important to be considered in wave making resistance analysis of twin hull including hull with fin stabilizer, especially for ship operates in shallow water condition. Computational analysis using Computational Fluid Dynamics (CFD) simulation is performed using Reynolds Average Navier-Stokes (RANS) to solve free surface effect problem. The method which applied is Volume of Fluid method, considering two phase condition. The objective of simulation is to predict the wave making resistance and flow pattern of catamaran with and without fin stabilizer, considering the relationship between wave interference and fins stabilizer. The analysis is performed in two configurations, bare hulls and hulls attached with fins. For both configurations, the investigation was conducted with range of model speed from 10 to 20 knots using k-epsilon turbulence model in shallow water condition. The results were based on pressure resistance (Rp) and flow pattern around hulls.