International Shipbuilding Progress - Volume 53, issue 2

Authors: Ekman, Philip

Article Type: Research Article

Abstract: A numerical model that simulates the launching of evacuation capsules from a ship in beam seas at Fn =0 has been developed and is presented in this paper. The model includes the motions of the ship and the wave climate in the vicinity of the ship. A boundary integral formulation in the frequency domain is used to calculate the wave climate, which includes radiated and diffracted waves, while the ship motions are determined using a strip-theory approach. The dynamics of the evacuation capsules during launching are simulated in the time domain. Launching can be performed with constant velocity as is …the case when launching lifeboats, or with constant acceleration which is used for fall-lifeboats. The motions of the mother ship, the positions and accelerations of the lifeboat or fall-lifeboat are constantly recorded and are validated by comparing the results to experimental model tests. The numerical results are shown to be in good agreement with experimental tests. Show more

Citation: International Shipbuilding Progress, vol. 53, no. 2, pp. 83-102, 2006

Authors: Stenius, I. | Rosén, A. | Kuttenkeuler, J.

Article Type: Research Article

Abstract: The paper considers explicit FE-modelling of fluid–structure interaction in hull–water impacts. To minimize the variables studied and to enable comparison with analytical methods, the problem is here idealised as a two-dimensional rigid wedge impacting on a calm water surface. A parameter study is performed, where the sensitivity in the mesh resolution and the contact parameter selection is investigated. It is concluded that a numerically stable non-leaking solution to the hull–water impact problem, with good correlation to analytical results, is achievable. It is however also concluded that application of this modelling technique can be costly and far from trivial. The solution …is for example highly dependent on the relation between mesh-density and contact-stiffness. Successful modelling hence requires rational approaches for determination of fluid discretization and contact parameters. By making reference to an analytical solution of the hull–water impact problem, the results from the parameter study are generalised, and a rational approach for determination of fluid discretization and contact parameters in the modelling of arbitrary hull–water impact situations is presented. The generality of the approach is favourably demonstrated for different impact angles and velocities. Show more

Keywords: Fluid–structure interaction, hull–water impact, high-speed craft, slamming, explicit FEA

Citation: International Shipbuilding Progress, vol. 53, no. 2, pp. 103-121, 2006

Authors: de Jong, Pepijn | Keuning, Jan Alexander

Article Type: Research Article

Abstract: In the last decade a growing interest can be observed in research aimed at the survivability of ships. Ship survivability is associated with larger amplitude motions and combined motions, such as capsizing (heave-roll) and broaching (sway-yaw-roll). Since large amplitude motions are inherently nonlinear, assessment of the seakeeping behaviour by the commonly used linear approach can be problematic. Complex effects, such as the viscosity dominated roll damping, submerged geometry variations and the coupling effects in the horizontal plane are disregarded. This may result in limited accuracy of these methods. The current research project is aimed at quantifying the importance of the …nonlinearities in the hydrodynamic reaction forces due to large amplitudes and nonlinear coupling effects at forward speed between simultaneously performed motions by means of forced oscillation tests. A segmented model of the Royal Netherlands Navy M-frigate was mounted to a newly developed 6-DOF forced oscillator in the towing tank of the Ship Hydrodynamics Laboratory at the Delft University of Technology. Each of the seven segments was fitted with a 6-component force transducer. The new oscillator renders the possibility of performing both large amplitude and arbitrary motions in six degrees of freedom. In this paper the results of this research will be presented, analysed, and the possible importance of nonlinear effects quantified. For now the scope will be limited to combined sway-yaw, heave-pitch and heave-roll motions. Significant nonlinearities, mostly related with submerged geometry variations, unsteady lift and viscous forces, will be quantified and qualified. Show more

Citation: International Shipbuilding Progress, vol. 53, no. 2, pp. 123-143, 2006

Authors: Iqbal, K. Shahriar | Rahim, Abdur

Article Type: Research Article

Abstract: This paper evaluates the environmental impact that is likely to be caused by modification of the hull form of traditional wooden country boat to ship shape, more suited to the speed range being encountered recently, in Bangladesh. For carrying out a comparative life cycle assessment (LCA), two major inventory items are considered; the material (steel) as well as the energy input required for building boats and the fuel consumed during operation a boat for a period of 5 years. Different compounds and substances consumed or released during the production and use of the transport were considered. The impact categories considered …are global warming, acid rain, eutrophication, and local air pollution. The analysis was based on assumptions such as the draft restrictions in the inland waterways, the economic speed of transportation combining fuel consumption and market demand, the steel fabrication standard in Bangladesh, etc. The analysis is based on impacts for unit ton-km since the number of vessels will change total number of crafts required to meet a specified demand with modification of the hull shape. The results show that such a transformation in the hull form of the inland vessels can reduce environmental burden up to 35% caused by the transport undertaken by vessels. Show more

Keywords: Country boat, life cycle impact assessment, hull shape modification

Citation: International Shipbuilding Progress, vol. 53, no. 2, pp. 145-154, 2006