Development Of A Semi-Swath Craft For Malaysian Waters

Small Waterplane Area Twin Hull (SWATH) and Catamaran vessels are known to have more stable platform as compared to mono-hulls. A further advantage of SWATH as compared to Catamaran is its smaller waterplane area that provides better seakeeping qualities. However, the significant drawback of the SWATH vessel is when encountering head-sea at high forward speed. Due to its low stiffness, it has a tendency for large pitch motions. Consequently, this may lead to excessive trim or even deck wetness. This phenomenon will not only degrade the comfortability but also results in structural damage with greater safety risks. In this research a modified SWATH design is proposed. The proposed design concept represents a combination of Catamaran and SWATH vessel hull features that will lead to reduce in bow-diving but still maintains good seakeeping capabilities. This is then called the Semi- SWATH vessel. In addition, the full-design of this vessel has been equipped by fixed fore fins and controllable aft fins attached on each lower hull. In the development of controllable aft fins, the PID controller system was applied to obtain an optimal vessel’s ride performance at speeds of 15 (medium) and 20 (high) knots. In this research work, the seakeeping performance of Semi-SWATH vessel was evaluated using time-domain simulation approach. The effect of fin stabilizer on the bare hull performance is considered. The validity of numerical evaluation was then compared with model experiments carried out in the Towing Tank at Marine Technology Laboratory, UTM. It is shown that the Semi-SWATH vessel with controllable fin stabilizer can have significantly reduction by about 42.57% of heave motion and 48.80% of pitch motion

Application of fuzzy logic controller to enhance the semi-SWATH performance in following seas

Semi-SWATH ship has a different characteristics compared to the common ship hull. The ship has a tendency to suffer bow-dive due to low restoring force at bow when running in following seas. In some conditions, the fore deck found to be immersed under the rear of wave. Acceleration motion to the trough increases the momentum force that pushing the ship to dive. The condition may cause the ship has a loss of control even the crew can feel thrown forward. In this research, fin stabilizer was applied to reduce the effect of those conditions with application of fuzzy logic controller. The controller calculates the angle for the fin stabilizer based on the pitch angle. The fin at both ends of the ship's hull increase the lift force, reduce the trim angle, and restrain the ship from dynamic high acceleration. A numeric time-domain program developed to analyze the ship sea keeping in following sea. The results showed the controller of the fin stabilizer has a significant effect in preventing the ship from the unsafe conditio

Computer Simulation of Current Forces on Motion of Floating Production Storage and Offloading in Irregular Waves

This paper presents the effect of current forces on the motion of forces on Floating Production Storage and Offloading (FPSO) in irregular waves. The objective of this research is to compute the motion of FPSO in irregular waves by time domain simulation including the effect of current forces. A study is made on the slowly varying oscillations of a moored single body system in a current and waves. Linear potential theory is used to describe the fluid motion, and three-dimensional source distribution techniques are applied to obtain the hydrodynamic forces and transfer function of the wave exciting forces. OCIMF (1994) data are used for estimation of the current forces. The non-linear time domain simulations have been carried out in irregular waves. Based on it, slowly varying motion responses are examined including the effect of the current forces. Several environmental conditions, such as the current angle of attack, current velocity, significant wave height and mean wave period are considered, which may significantly affect FPSO motion in surge, sway and yaw moments. It is found that the effect of current forces is quite significant when the current velocity is increased. In this simulation, while the current velocity is increased to 3.0 meter/seconds, the impact on FPSO motion is quite significant, which should be taken into consideration from the point of view of safety, failure of mooring systems, operating responses and the dynamic positioning of the FPSO

Port capacity forecasting and the impact of the dredging works on port sea operations using discrete event simulation

Continuous capacity expansion is vital for ports to handle future growth due to the increase in volume of maritime transport and size of the vessels. Some improvements and developments are required for the port to enhance its capacity throughput. In order to accommodate huge vessels without any restrictions, there is a need to deepen the channels. Furthermore, there is also need to widen the channel to prevent congestions. Ho wever, dredging work for deepening the harbour waters will reduce the utilization of the berths and navigational areas . This will significantly affect the port capacity and hence its income. In this paper a simulation program based on queuing theory and di screte event simulation is developed and used for forecasting port throughput and simulating dredging conditions. Data from a container port and an Automatic Identification System (AIS) were utilised to develop the simulation program in MATLAB - Simulink. Us ing this tool, port capacity was simulated and the effect of dredging on port capacity was studied. An appropriate period of time needed for dredging is determined by taking into considerations the blocking of some berths and limiting the number of vessels passing the channel s during the dredging operations. The results from the simulations could then be used for planning the dredging works

Static stability of a compound wing configuration in ground effect

The height static stability of a wing can be a main concern for conceptual design of wing-in-ground effect (WIG) crafts. In this research, the stability of a rectangular and compound wing was computationally predicted in ground effect. A realizable k-e turbulent model was used for simulation the flow filed over the wing surfaces. First, the drag coefficient and lift to drag ratio of numerical simulation were validated by experimental data of the rectangular wing. Next, the stability of the compound wing respect to different ground clearances will be determined and compared with rectangular wing. This study illustrated a deep understanding of static stability of present compound wing in ground effect, which eventually can be a guideline for researchers and designers of WIG craft

Effect of water current on underwater glider velocity and range

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

Hydrodynamic resistance analysis of new hull design for multipurpose amphibious vehicle applying with finite volume method

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 surfac

Performance of the lightning air terminal for the macro model of buildings

"Lightning is a natural occurring phenomenon having a very high voltage and current. Building protection from the effect of lightning stroke is one of the most important features. Lightning flash, nature changes with increasing the clearance between the ground structure and the cloud. Providing proper protection to the building, Frankling rod/Lightning air terminal is an essential element to receive the lightning flashes in order to make sure the protection of building. In this paper a down scaled building with four lightning rods has been chosen to see how the lightning rods with different air gap and view of the building perform, in lightning flash. The building is tested with three different views which are front, back and side views. The lightning rods provided different air gaps/clearance between the plain and the top plate. Single stage impulse generator is used. A voltage up to 90 kV is applied to analyze the lightning flash receiving ability of lightning rods. Through experimental work the lightning flash receiving ability is studied in detail for three views of the down scaled building.

Super yatch design study for Malaysian sea (Langkawi Island)

Malaysia as a country surrounded by water has a huge economic and geographical potential in the development of super yacht industry in South East Asia. There is lack of super yacht design study specifying to Malaysian marinas and seas. Most of the super yacht operates in Malaysia were built and bought directly from oversea, and chartered by foreign companies. It is hence the purpose of this study to survey on Malaysian sea water, particularly Langkawi Island, to introduce a design methodology in producing a preliminary design of super yacht that suits Langkawi Island, and serves as a guideline for future super yacht design for Malaysian sea in different marinas. Suitable dimensions of super yacht were derived by using dimensional relationship via statistical method. Two types of hull form designs (round bilge and V-bottom hull) were designed using Maxsurf Pro software. Resistance analysis on the two hull forms were carried out using Savitsky Pre-Planing and Compton methods via MaxsurfHullspeed software, and stability performance of the two hull forms was analyze using Hydromax software. VBottom hull form is found to have better resistance performance as compared to round bilge hull form, and both hull forms are found to be in stable conditions and comply with IMO requirements