The Experts below are selected from a list of 18 Experts worldwide ranked by ideXlab platform
Daeng Paroka - One of the best experts on this subject based on the ideXlab platform.
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Estimation of Effective Wave Slope Coefficient of Ships with Large Breadth and Draught Ratio
Kapal, 2020Co-Authors: Daeng Paroka, Andi Haris Muhammad, Sabaruddin RahmanAbstract:One of parameters to estimate heel angle of a ship in beam seas is effective wave slope coefficient. In the weather criterion of IMO, the effective wave slope coefficient is determined as function of Ratio between distance of center of gravity from the sea surface and the ship Draught. The others methods could be used to estimate the effective wave slope coefficient are simplified strip theory and model experiment. A ship with shallow Draught and large vertical center of gravity can have an effective wave slope coefficient larger than 1.0 if the coefficient is calculated by using the formulae of weather criterion. Therefore, an alternative method to estimate the coefficient is necessary when it is applied to ships with geometry characteristics different with those used to develop the formulae. This research conducts to estimate the effective wave slope coefficient using three different methods, namely the formulae of weather criterion, the simplified strip theory and model experiment. Results of the three methods may provide enough evidence about suitable method to estimate the effective wave slope coefficient of ships with breadth and Draught Ratio larger than 3.5 like the Indonesian ro-ro ferries. Results and discussion show that the effective wave slope coefficient obtained by using the formulae of weather criterion is larger compared to that obtained by using the simplified strip theory and the model experiment. Here, the result of simplified strip theory for wave frequency the same as the roll natural frequency of subject ship is similar with the result of model experiment. This results show that the simplified strip theory can be used as an alternative method to determine the effective wave slope of a ship with breadth and Draught Ratio larger than 3.5 if the result of model experiment does not available.
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ROLL MOTION CHARACTERISTICS OF SHIP WITH LARGE BREADTH AND Draught Ratio IN FOLLOWING WAVES
2013Co-Authors: Daeng Paroka, Syamsul AsriAbstract:Since the International Maritime Organization decided to revise its intact stability criteria from deterministic based criteria to be performance based one, some researches regarding the ship performance in waves have been conducted by several researches. One of the dangerous condition reccomended to be included in the criteria was the stability of ships in following waves especially for ship with small coefficient for vertical well-sidedness. Ships with large breadth and Draught Ratio tends to have large the coefficient for well-sidedness. However large roll angle may occur when the ships operate in large significant wave height. The forward speed also could have significant effect on the roll motion characteristics due to time spend of ship in a certain position relative to the wave. This paper discusses effect of restoring arm variation due to waves characteristics and ship speed on roll motion of ships with large breadth and Draught Ratio in following waves. The waves characteristics is modelled based on the Beaufort scale and the forward speed is estimated by changing the propeller revolution from 6 rps to 15 rps. The results of numerical simulation and discussions show that amplitude of roll motion significantly affected by variation of the waterline area of the ship in sugging and hogging condition. The large roll angle can be avoided by increasing the forward speed with considering the other dangerous condition such as pure loss of stability and broaching.
Syamsul Asri - One of the best experts on this subject based on the ideXlab platform.
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ROLL MOTION CHARACTERISTICS OF SHIP WITH LARGE BREADTH AND Draught Ratio IN FOLLOWING WAVES
2013Co-Authors: Daeng Paroka, Syamsul AsriAbstract:Since the International Maritime Organization decided to revise its intact stability criteria from deterministic based criteria to be performance based one, some researches regarding the ship performance in waves have been conducted by several researches. One of the dangerous condition reccomended to be included in the criteria was the stability of ships in following waves especially for ship with small coefficient for vertical well-sidedness. Ships with large breadth and Draught Ratio tends to have large the coefficient for well-sidedness. However large roll angle may occur when the ships operate in large significant wave height. The forward speed also could have significant effect on the roll motion characteristics due to time spend of ship in a certain position relative to the wave. This paper discusses effect of restoring arm variation due to waves characteristics and ship speed on roll motion of ships with large breadth and Draught Ratio in following waves. The waves characteristics is modelled based on the Beaufort scale and the forward speed is estimated by changing the propeller revolution from 6 rps to 15 rps. The results of numerical simulation and discussions show that amplitude of roll motion significantly affected by variation of the waterline area of the ship in sugging and hogging condition. The large roll angle can be avoided by increasing the forward speed with considering the other dangerous condition such as pure loss of stability and broaching.
Petersson Emil - One of the best experts on this subject based on the ideXlab platform.
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Study of semi-empirical methods for ship resistance calculations
Uppsala universitet Tillämpad mekanik, 2020Co-Authors: Petersson EmilAbstract:In the early ship design process a quick overview of which shipdesign that could be the optimal choice for the intended usage needsto be investigated. Therefore the feasibility and accuracy ofinterpolating between measurement data from model resistance serieswhen estimating unknown hulls were conducted. A parametric study wasundertaken in order to investigate which parameters carry the mostimportance in regard to calm water resistance for semi-displacinghulls. In order to asses the whole estimation process one semidisplacing ship (FDS-5) and one bulk carrier with a bulbous bow (JBC)were estimated in regard to calm water resistance by using semiempirical methods and were later compared with CFD results. The CFDresults came from a in part parallel conducted work. The resultsshowed that it is possible to estimate the total resistance withsemi-empirical methods to an unknown hull by linear interpolationwith an accuracy of below 5% in the designed speed interval both forFDS-5 and JBC. The CFD simulations achieved a lower accuracy comparedto the semi-empirical approach, however by furhter calibrating themodels, the accuracy could potentially be improved. Linearinterpolation between two hulls in order to estimate an unknown hull,is only advised when the hulls are nearly identical. Meaning that thehulls must be of the same ship type and that only one parameter isallowed to differ compared to the unknown hull. The parametric studyresulted in parameter importance in falling order: Slenderness Ratio,length-beam Ratio, longitudinal prismatic coefficient, blockcoefficient and beam-Draught Ratio. Even though the CFD approach notyet is completely reliable, it could still be a useful complement tothe semi-empirical approach by calculating parameters such as adynamic wetted surface, resistance due to appendages or airresistance of the full-scale ship. Simply by incrementally increasingthe accuracy of individual resistance components an overallimprovement could potentially be achieved
Sabaruddin Rahman - One of the best experts on this subject based on the ideXlab platform.
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Estimation of Effective Wave Slope Coefficient of Ships with Large Breadth and Draught Ratio
Kapal, 2020Co-Authors: Daeng Paroka, Andi Haris Muhammad, Sabaruddin RahmanAbstract:One of parameters to estimate heel angle of a ship in beam seas is effective wave slope coefficient. In the weather criterion of IMO, the effective wave slope coefficient is determined as function of Ratio between distance of center of gravity from the sea surface and the ship Draught. The others methods could be used to estimate the effective wave slope coefficient are simplified strip theory and model experiment. A ship with shallow Draught and large vertical center of gravity can have an effective wave slope coefficient larger than 1.0 if the coefficient is calculated by using the formulae of weather criterion. Therefore, an alternative method to estimate the coefficient is necessary when it is applied to ships with geometry characteristics different with those used to develop the formulae. This research conducts to estimate the effective wave slope coefficient using three different methods, namely the formulae of weather criterion, the simplified strip theory and model experiment. Results of the three methods may provide enough evidence about suitable method to estimate the effective wave slope coefficient of ships with breadth and Draught Ratio larger than 3.5 like the Indonesian ro-ro ferries. Results and discussion show that the effective wave slope coefficient obtained by using the formulae of weather criterion is larger compared to that obtained by using the simplified strip theory and the model experiment. Here, the result of simplified strip theory for wave frequency the same as the roll natural frequency of subject ship is similar with the result of model experiment. This results show that the simplified strip theory can be used as an alternative method to determine the effective wave slope of a ship with breadth and Draught Ratio larger than 3.5 if the result of model experiment does not available.
Kazuki Ikushima - One of the best experts on this subject based on the ideXlab platform.
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Effects of half breadth to Draught Ratio of hull under water surface on bilge-keel roll damping component
Ocean Engineering, 2019Co-Authors: Toru Katayama, Masaki Matsuoka, Toshiya Adachi, Kazuki IkushimaAbstract:Abstract Roll amplitudes of parametric roll in regular head waves are sometimes underestimated by motion calculations including Ikeda's roll damping prediction method, especially for the case of the large roll amplitude caused by high wave height. In this case, generally the ship has significant relative Draught changing because of its heave and pitch. It may be said that the effects of the change in relative Draught on roll damping is significant. However, in Ikeda's prediction method, the bilge-keel component which is the largest component of total roll damping does not take the effects of Draught. As the effects of Draught, there are at least two related significant effects on the bilge-keel roll damping component not fully considers for developing Ikeda's prediction method. They are the effects of underwater hull aspects (: half breadth to Draught Ratio) and the free surface effects. In this study, as a first attempt, the effects of Draught on the bilge-keel component are investigated experimentally and numerically by using a 2-dimensional model. And a prediction model of the effects of Draught on bilge-keel component to collect Ikeda's prediction method is proposed. Moreover, the calculated results by the proposed method are compared with some measured data including the effects of Draught and its validity is confirmed.
