International Shipbuilding Progress - Volume 39, issue 420

Authors: Haddara, M.R. | Cumming, D.

Article Type: Research Article

Abstract: The results of an extensive experimental program to study the roll damping characteristics of a warship model are reported. The simple free decay curves obtained for a towed as well as a self-propelled nine metre model, fitted with and without bilge keels, rudder and propellers, were analyzed using an energy approach. A new nondimensionalization scheme is used for the representation of the results and used to derive relationships relating the damping coefficient to the value of the metacentric height of the model. The nonlinearity of the damping with forward speed is explained.

DOI: 10.3233/ISP-1992-3942001

Citation: International Shipbuilding Progress, vol. 39, no. 420, pp. 323-343, 1992

Authors: Hua, Jianbo

Article Type: Research Article

Abstract: In this work computer-simulation has been used to study the behaviour of a RoRo-ship subjected to parametrically excited roll motion in longitudinal waves. The influence of parameters such as ship speed, KG-value. wave amplitude etc. on this kind of roll motion has been investigated.

DOI: 10.3233/ISP-1992-3942002

Citation: International Shipbuilding Progress, vol. 39, no. 420, pp. 345-366, 1992

Authors: Adegeest, L.J.M.

Article Type: Research Article

Abstract: Linear and nonlinear hydrodynamic reaction forces are investigated by using a ship model, heaving with large amplitudes on a free surface, with forward speed. The ship model used is a mathematically described segmented Wigley model. The hydrodynamic reaction forces are measured and from these the first-, second- and third-order force components are obtained by using Fourier analysis. The first-order components are compared with the theoretical added mass- and damping-distribution. The computations are based on 3-D potential theory. The second-order components are compared with a theoretical approximation based on an extension of the linear potential theory. The calculated first-order forces …as well as the second-order forces compare well with the experimental values. The relative importance of the various force components is discussed. Show more

DOI: 10.3233/ISP-1992-3942003

Citation: International Shipbuilding Progress, vol. 39, no. 420, pp. 367-389, 1992

Authors: Deliporanides, G.

Article Type: Research Article

Abstract: Increased ship dimensions and installed propulsion power require still heavier shaft systems. As a consequence, in a shaft alignment process, even higher accuracy has to be achieved. A serious problem in a shafting system comes from the fact that less bearings lead to high bearing pressures and thus to higher deflections due to elasticity of the bearing foundation. The elasticity of bearings is rarely accounted for because of the complications it implies both in its simulation through a stiffness coefficient and in treating the resulting differential equation. A FE (Finite Element) code capable of being applied on a personal computer …has been developed in order to deal with the alignment of main propulsion shafting systems. Show more

DOI: 10.3233/ISP-1992-3942004

Citation: International Shipbuilding Progress, vol. 39, no. 420, pp. 391-397, 1992

Authors: Radev, D. | Beukelman, W.

Article Type: Research Article

Abstract: As follow-up of former research forced vertical oscillation experiments have been performed to determine peak pressures and rise times for four metal wedges with different dead rise angles. These pressures have been measured as function of vertical oscillation speed, trim angle and forward speed. The results, in general, show that the peak values of the impact pressures are proportional to the squared value of the vertical speed, however, also the influence of forward speed appeared to be significant. In most of the existing mathematical models this relation has unsufficiently accounted for as shown here. Application of the prediction models in …this respect is urgently required. Show more

DOI: 10.3233/ISP-1992-3942005

Citation: International Shipbuilding Progress, vol. 39, no. 420, pp. 399-422, 1992

Authors: Nibbering, J.J.W.

Article Type: Research Article

Abstract: The high stress level in ships – largely due to the use of higher strength steels – has made fatigue a major problem for ship-owners and classification societies. It will be discussed that fatigue cracks are not merely a nuisance (leakage and repairs), but that they constitute a and probably the main danger for the safety of ships against (brittle) fracture. It is doubtful whether sophisticated fatigue and reliability calculations are of much use in this respect. Rather they may give a false feeling of safety. Better design of details and especially improved workmanship (welding), are more valuable. Examples will …be given. Show more

DOI: 10.3233/ISP-1992-3942006

Citation: International Shipbuilding Progress, vol. 39, no. 420, pp. 423-435, 1992

Article Type: Other

DOI: 10.3233/ISP-1992-3942007

Citation: International Shipbuilding Progress, vol. 39, no. 420, pp. 437-438, 1992