International Shipbuilding Progress - Volume 65, issue 1

Authors: Abdul Ghani, Pauzi | Wilson, Philip

Article Type: Research Article

Abstract: This paper explores the effects of adding different forms of bulbous bows onto catamaran hulls and assesses the implications on the seakeeping performance. There has been a large body of work that assess’ the effect of wave wake wash and recently studies have been undertaken to determine the effects of bulbous bows on reducing wave wake wash. However, not much research has been published on the effects of bulbous bows on the seakeeping performance of catamarans fitted with bulbous bows. This paper presents experimental results that will allow a ship designer to understand the effects of bulbous bows on heave, …pitch and added resistance in waves. In conclusion it ranks the importance of different bulbous bows on the seakeeping performance. Show more

Keywords: Bulbous bow, seakeeping, added resistance, heave, pitch, waves

DOI: 10.3233/ISP-170140

Citation: International Shipbuilding Progress, vol. 65, no. 1, pp. 1-28, 2018

Authors: van Lieshout, P.S. | den Besten, J.H. | Kaminski, M.L.

Article Type: Research Article

Abstract: Structural geometry and stochastic loads such as swell and wind seas can typically induce multiaxial stress states in welded details of marine structures. It is known that such complex time varying stress states determine the fatigue resistance of welded steel joints. Therefore, it is of importance to account for them in fatigue lifetime estimation. Over the past few decades a wide variety of design guidelines and methods have been developed for multiaxial fatigue assessment, but so far there does not exist a general hypothesis applicable to all possible load cases. This study provides an overview of the current state-of-the-art in …academia and engineering practice in terms of multiaxial fatigue assessment, and is focusing on the application to welded joints in marine structures. The progress of different approaches and methods is elaborated and commented upon, taking their hypothesis and (physical) basis into consideration. The insights that are provided in this paper form a valuable foundation for future investigations and emphasize the necessity of experimental proofs and model validation. Show more

Keywords: Multiaxial fatigue, welded joints, marine structures, non-proportionality, variable amplitude loading

DOI: 10.3233/ISP-170141

Citation: International Shipbuilding Progress, vol. 65, no. 1, pp. 29-71, 2018

Authors: Pan, Dewei | Lin, Chengxin | Zhou, Zhaoxin | Sun, Yuqiang | Sun, Yuhao | Liu, Zhijie

Article Type: Research Article

Abstract: In the process of marine salvage, the capsized ship is normally required to go through a process of righting firstly, which essentially means bringing the deck to point upwards. Calculation of the righting force is the key to achieving success in designing schemes. At present, the righting force calculation relies on the use of empirical formulae. However, their accuracy and reliability is not high. In this paper, a mathematical model of the flooding quantity and righting force was established based on the hydrostatic theory applied to the ship. A three-dimensional ship model was built via General Hydrostatics software (GHS) to …simulate the uprighting process of a capsized and damaged ship. Four typical uprighting processes concerning capsized ships were simulated, namely the case where about 50% of the superstructure volume was filled with water (Case 1), where about 50% of the engine room volume was filled with water (Case 2), where the superstructure was detached (Case 3) and where a large amount of air in the damaged compartments existed (Case 4). Simulation results show that the proportion between the maximum righting moment and the maximum righting moment in the opposite direction is 0.459, 0.486, 0.424 and 0.346 for cases A, B, C and D, respectively. So a larger righting force moment in the opposite direction is needed to prevent the ship from being damaged again or from capsizing again. The shear force is not always increasing with the flooding quantity or displacement. The effect of flooding water distribution is more obvious than the flooding quantity and displacement for a ship with many damaged compartments when the trim angle variation is very small. Thus, the righting force can be efficiently reduced by designing reasonable uprighting schemes. Show more

Keywords: Hydrostatic, capsize, damaged ship, uprighting, righting force moment

DOI: 10.3233/ISP-180142

Citation: International Shipbuilding Progress, vol. 65, no. 1, pp. 73-92, 2018

Authors: Bordogna, G. | Keuning, J.A. | Huijsmans, R.H.M. | Belloli, M.

Article Type: Research Article

Abstract: Wind-assisted propulsion has recently attracted attention as one viable option to drastically reduce pollutant emissions produced by ships. Despite its potential, there is still a substantial lack of understanding of the physical aspects proper of wind-assisted ships, leading to unreliable fuel-saving claims. In the context of the development of a performance prediction program for such type of hybrid ships, the research presented herewith deals with the aerodynamic interaction between two rigid sails. Wind-tunnel experiments were carried out on a single sail and on a two-sail arrangement, during which force and pressure measurements were taken on each sail. For the two-sail …arrangement, two gap distances between the sails were investigated and the tests were performed at apparent wind angles ranging all typical sailing conditions. The results show that for an extended interval of moderate apparent wind angles the aerodynamic interaction has a positive effect on both sails. On the contrary, at smaller and at larger angles the interaction effects are detrimental for the downstream sail. The outcome of the present work indicates that the number of sails employed and their gap distance are important parameters to determine the aerodynamic interaction effects. Show more

Keywords: Green shipping, renewable energy, sailing vessels, sail aerodynamics, ship propulsion

DOI: 10.3233/ISP-180143

Citation: International Shipbuilding Progress, vol. 65, no. 1, pp. 93-125, 2018