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CURRENT ISSUE
Vol. 6, No. 2; July 2010
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Hydrodynamic Response Characteristics of Non Circular Spar Hulls
by K. Muthuchelvi Thangam and S. Nallayarasu
Hydrodynamic performance of Jacket Spar platform under regular waves
by Sajini U S, Sundaravadivelu R & Ananthasubramanian V
A bubble population density spectrum model for the central Arabian Sea
by Uphar Saxena and Prasad K. Bhaskaran
Swot Analysis of Ship building Industries in Bangladesh and its Challenges to become Potential Ship-Exporting Nation
by N. M. Golam Zakaria, Kh. Akhter Hossain & Md. Shahidul Islam
Experimental Investigation of Characteristics of Dynamics of Ship to Ship Collision
by M. Rafiqul Islam, Omar Yaakob, Adi Maimun, Zobair Ibn Awal & Fahd Ezadee Jamaludin
Interpolation Procedures for Long Term Probability Prediction of Wave Induced Loads for Tankers and Container Ships
by Milorad D. Motok and Jasna Jovovic
BACK COVER, Vol. 6, No. 2, July 2010
Hydrodynamic Response Characteristics of Non Circular Spar Hulls
K. Muthuselvi Thangam and S. NallayarasuHydrodynamic
ABSTRACT
Spar is a large diameter floating vertical cylinder with adequate buoyancy to support the payload with sufficient space for storage. Though the circular Spars are in use, there is a need for an alternate concept to reduce the fabrication and installation difficulty of large diameter circular cylinders. In this paper, the hydrodynamic response characteristics of a circular Spar and non-circular Spar hulls are investigated both experimentally and numerically. The experimental investigations were carried out for three different model configurations for three different wave heading angles. The design of Spar hulls were carried out using environmental parameters for East and West Coast of India for a payload of 10,000 tonnes and it was moored at a water depth of 300m. A scale model of 1:100 of the prototype Spar hull is used for experimental investigations. The numerical analysis was carried out using the software WAMIT and OrcaFlex. The numerical analysis was carried out in two stages. The motion response characteristics of the Spar hulls were presented in the form of RAOs and compared with both experimental and numerical results. The experimental results compare well with the numerical methods for most range of wave periods and the maximum difference in peak response is found to be around 15%. The effects of hull shape on the RAOs based on experimental investigations were presented. The effect of wave heading angle and the mooring on the RAOs were also presented and discussed. The predicted response indicates that the proposed hull shapes are suitable for East and West Coast of India.
Keywords:SPAR hull, RAO, Hydrodynamic Response.
Hydrodynamic performance of Jacket Spar platform under regular waves
Sajini U S, Sundaravadivelu R & Ananthasubramanian V
ABSTRACT
This paper deals with the numerical study on the hydrodynamic behavior of a jacket spar platform designed for 10 MLD (million liters per day) desalination plant. The water depth and payload considered are 375 m and 50×103 kN respectively. The numerical simulations are validated by comparing the surge, heave and mooring line tension response with the experimental results.
Keywords: Jacket spar, desalination, payload, surge and heave.
A bubble population density spectrum model for the central Arabian Sea
Uphar Saxena and Prasad K. Bhaskaran
ABSTRACT
Breaking waves in the open sea generate bubble clouds which exhibits rapid variability in both space and time scales. The resultant bubble size, population and e-folding depth generated by wave breaking has a strong functional dependence on wind speed above the water surface. The bubble clouds so generated are quite in-homogeneous which evolves rapidly by inherent physical mechanisms. To the best of our knowledge, a bubble population model describing spatial variability of population density as a function of wind speed and categorized by bubble plumes is not reported so far in literature. The present work reports on the development of a spatial resolving bubble population model based on wind speed at 10m height above sea-surface for the central Arabian Sea. The model can be used for prediction of bubble population density in any arbitrary region and categorized by evolving bubble plumes in the open sea. The estimated bubble population density depends on the bubble spectral shape function and a depth dependent function. Based on a validation study for the spectral shape and integrated bubble population with reported available measurements, we propose with confidence the robustness and applicability of this model for any given arbitrary region in the open sea.
Keywords: Bubble population, wave breaking, wind speed, spectral shape, bubble plumes.
Swot Analysis of Ship building Industries in Bangladesh and its Challenges to become Potential Ship-Exporting Nation
N. M. Golam Zakaria, Kh. Akhter Hossain & Md. Shahidul Islam
ABSTRACT
Bangladesh has got glorious history & heritage as a shipbuilding nation since crafted bodies have floated on water in ancient time. Recently some shipyards of Bangladesh have come to limelight by exporting ocean-going vessels to the foreign countries. On the other hand, due to the unprecedented shipping boom and over burdened existing shipbuilding nations, shipowners and shipbuilders are interested in building smaller ships of DWT less than 25,000 in Bangladesh. Therefore they are exploring the possibilities of Bangladeshi shipbuilding industries. But, unfortunately, the reliable and updated data related to these potential industries are almost rare which makes it difficult to assess the overall status of this industry. In this paper, an effort has been made to evaluate status of the present shipbuilding industries in Bangladesh. At first an overall picture of this industries has been depicted by reviewing the actual shipbuilding practice in public and private sector. Relevant data have been explored and existing and upcoming yards have been identified and categorized by describing the shipyard in terms of modern shipbuilding requirements. Strength, weakness, threat and opportunity (SWOT) have been analyzed on the basis of the data collection as well as looking internal and external market. Finally some recommendations have been put forward in line with this study for sustainable of development of this industry in the long run.
Keywords: Ship building, SWOT, shipyards, ship-exporting nation, potentiality etc.
Experimental Investigation of Characteristics of Dynamics of Ship to Ship Collision
M. Rafiqul Islam, Omar Yaakob, Adi Maimun, Zobair Ibn Awal & Fahd Ezadee Jamaludin
ABSTRACT
This paper investigates the characteristics of dynamics of ship to ship collisions. Model experiments were conducted using two ship models of similar size. The models are a 2.38 m tanker as the struck ship and a 2.25 m container ship as the striking ship. The parameters considered for the experiments include the speed of the striking ship, angle between the ships and the point of collision at the struck ship. Data collected are the amplitude of rolling, pitching and yawing motion of the struck ship. Dynamic characteristics of the striking ship model are observed. The experimental results for yaw
are also compared with the numerical simulation results. The outcome of the research shows that when two ships collide with one another ship, they experience significant yawing motion risking dangerous ports and canals accidents. It is also found that collision angle and speed of the striking ship play a vital role for the dynamic characteristics of the struck ship.
Keywords: Collision, Dynamics, Yaw Motion, Roll motion, Capsize
Interpolation Procedures for Long Term Probability Prediction of Wave Induced Loads for Tankers and Container Ships
Sangeeta Sonak, Asha Giriyan and Prajwala Pangam
ABSTRACT
The basic idea of this paper was to develop straightforward procedures for predicting the long term probability distribution of wave induced loads on ships - more accurate than existing rule formulas but less demanding and time consuming than true direct calculations. For series of 14 container ships and 11 tankers motion equations for combined heave and pitch are solved and RMS values of maximum wave induced vertical shear force and bending moment calculated for whole scope of 156 sea states in scatter diagram for North Atlantic. Comparison of thus found probability distributions of force and moment reveals considerable disagreement with corresponding IACS Unified Longitudinal Strength Requirements S11. Consequently some interpolation routines based on herein obtained results are proposed as possible improvement. This study is the continuation of the research, the first part results of which were presented at RINA International Conference Developments in classification & international regulations in January 2007.
Keywords: Wave induced bending moment, wave induced shear force, long term probability distribution of wave induced loads on ships, Unified Longitudinal Strength Requirements S11.
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