International Shipbuilding Progress - Volume 58, issue 1

Authors: den Besten, J.H. | Huijsmans, R.H.M. | Vredeveldt, A.

Article Type: Research Article

Abstract: Foam filled hull structures show, especially for high speed crafts like RIB's, new opportunities. These hull structures, sandwich structures with aluminium or fibre reinforced plastic face sheets and a flexible foam core, large compared to the face sheet thickness, have the advantage of low density, high strength, water penetration resistance, high corrosion resistance and promising vibration isolation and structural damping characteristics. Particular advantage is expected in case of dynamic loading in environmental severe conditions. Primary objective is to develop an analytical, 2D, mathematical model for the local structural response of a hydrodynamic impact loaded sandwich structure with vibration isolation …and structural damping properties. The structural response is determined by solving semi-analytically a hydro-elastic coupled sandwich flexible core model and a hydrodynamic impact model in modal space, verified by results found in literature and FEM calculations. Beyond structural weight savings and increased buoyancy, an increased comfort level and less fatigue damage sensitivity compared to stiffened panel hull structures may be obtained. Show more

Keywords: Slamming, hydro-elasticity, sandwich structure, flexible core, structural damping

DOI: 10.3233/ISP-2011-0068

Citation: International Shipbuilding Progress, vol. 58, no. 1, pp. 1-57, 2011

Authors: Abusedra, L. | Belmont, M.R.

Article Type: Research Article

Abstract: Early in the development of the new discipline of short term deterministic sea wave prediction (DSWP) the prediction region diagram was introduced. This was intended to provide information on the region in space and time where a propagating wave system arose from waves that had been previously totally measured. This diagram is compared here with a space time plot that also incorporates the accuracy of the prediction achievable by the prediction algorithms. In this context certain issues raised in the literature about the relative roles of group and phase velocity are examined. It is shown that the stationary phase approximation, …which predicts wave packets propagate at the group velocity, does not hold under the conditions applying to practical DSWP. The numerical work presented introduces a new frequency domain prediction technique termed the data extension method. This is derived from the Papoulis–Gerchberg iteration scheme and reduces prediction errors associated with periodicity artefacts. A method is described for deriving analytic guidelines that allow estimates of prediction performance to be made for standard sea types, with illustrative results being presented for the Pierson–Moskowitz power density spectrum. Show more

Keywords: Wave prediction, stationary phase

DOI: 10.3233/ISP-2011-0069

Citation: International Shipbuilding Progress, vol. 58, no. 1, pp. 59-81, 2011