Journal Articles

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Author: search.filters.author.Sha, O. P.

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    CFD analysis for a ballast free ship design
    (NISCAIR-CSIR, India, 2014-11) Godey, Avinash; Misra, S. C.; Sha, O. P.
    Shipping transfers approximately 3 to 5 billion tonnes of ballast water internationally each year. This ballast water transferred between different ports is a serious environmental problem. There are many marine species like bacteria, small invertebrates and the eggs, etc., that are carried in ship’s ballast water which are small enough to pass through a ship’s intake at ports and when discharged, lead to severe ecological problems. To overcome this, a concept of ballast free ship has been developed in which ballast water exchange and treatment is avoided by providing flow-through longitudinal pipes in the double bottom instead of conventional ballast tank. During the design of the ballast free ship, different hull forms have been generated with various hull shapes of the vessel which have been studied with regard to hydrodynamic behaviour. Finally one hull form has been selected for further study. The present work aims to estimate the penalty on resistance using CFD techniques using SHIPFLOW® software. These results are validated by model experiments for the conventional and the proposed ballast Free form at loaded and ballast drafts in the Hydrodynamics Laboratory of the Department of Ocean Engineering and Naval Architecture, IIT Kharagpur.
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    Development of a four-bladed surface piercing propeller series
    (Naval Engineers Journal, 2012) Misra, S. C.; Gokarn, R. P.; Sha, O. P.; Suryanarayana, Ch.; Suresh, R. V.
    The intent of this work was to develop a methodical series of four-bladed propellers of the surface piercing type so as to be able to design a surface piercing propeller for a given operating condition. A test rig along with instrumentation was developed at NSTL to determine the open water characteristics of surface piercing propellers experimentally. Initially, four model propellers were designed and manufactured with four different section shapes with the same pitch ratio and blade area ratio. The diameter of all the model propellers was fixed at 250mm. These propellers were of two basic section shapes: wedge and diamond back. To study the effect of trailing edge inclination (cup shape) three different wedge shapes were developed with the trailing edge making angles of 0°, 30°, and 60° to the horizontal respectively. These four propellers were tested extensively in the High Speed Towing Tank of NSTL. Weber number effects were found to be small in the model tests that were carried out at 20rps for the 250mm diameter propellers. The best performance at all immersions was obtained from SPP-3, the propeller having wedge shaped sections with the trailing edge inclined at 60° to the horizontal. The astern performance of this propeller was found to be satisfactory from the limited number of tests that were conducted.
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    Development of a ballast free ship design
    (International Journal of Innovation Research & Development, 2012-12) Godey, Avinash; Misra, S. C.; Sha, O. P.
    Shipping transfers approximately 3 to 5 billion tonnes of ballast water internationally each year. Ballast water discharges non-native species leading to severe ecological problems. The present work aims at a design solution into the ballastless ship in which ballast water exchange and treatment is avoided by providing flow-through longitudinal pipes in the double bottom instead of conventional ballast tanks. During the design of the ballast less ship, different hull forms are generated with altering the hull shape in forward and aft out of which one was finalised. In addition to change in hull form the internal tank arrangement has been changed so that the propeller immersion and the minimum draft required in the ballast condition is achieved. Structural arrangement for the mid ship section was proposed for the modified hull form of ballast less ship as well as data on valves had been collected for the flow through condition. Finally, resistance tests were conducted on equivalent models of scale ratio 1:71 for the conventional and the proposed ballsatless form at the loaded and ballast drafts in the Hydrodynamic Towing Tank of the Department of Ocean Engineering and Naval Architecture, IIT Kharagpur. The model experiments on ballast less ship show an increase in resistance in ballast draft when compared to a conventional tanker due to the flow through pipes in double bottom.