No abstract

Upon entering shallow waters, ships experience a number of changes due to the hydrodynamic interaction between the hull and the seabed. Some of these changes are expressed in a pronounced increase in sinkage, trim and resistance. In this paper, a numerical study is performed on the Duisburg Test Case (DTC) container ship using Computational Fluid Dynamics (CFD), the Slender-Body theory and various empirical methods. A parametric comparison of the behaviour and performance estimation techniques in shallow waters for varying channel cross-sections and ship speeds is performed. The main objective of this research is to quantify the effect a step in the channel topography on ship sinkage, trim and resistance. Significant differences are shown in the computed parameters for the DTC advancing through dredged channels and conventional shallow water topographies. The different techniques employed show good agreement, especially in the low speed range

A review is made of linear slender-body methods for predicting the squat of a ship in shallow open water, dredged channels or canals. The results are summarized into a general formula based on Fourier transforms, and the method is extended to cater to stepped canals. An approximate solution for canals of arbitrary cross-section is proposed.

Underwater sound of rigid-hulled inflatable boats was recorded 142 times in total, over 3 sites: 2 in southern British Columbia, Canada, and 1 off Western Australia. Underwater sound peaked between 70 and 400 Hz, exhibiting strong tones in this frequency range related to engine and propeller rotation. Sound propagation models were applied to compute monopole source levels, with the source assumed 1 m below the sea surface. Broadband source levels (10–48 000 Hz) increased from 134 to 171 dB re 1 μPa @ 1 m with speed from 3 to 16 m/s (10–56 km/h). Source power spectral density percentile levels and 1/3 octave band levels are given for use in predictive modeling of underwater sound of these boats as part of environmental impact assessments.

Smoothed Particle Hydrodynamics (SPH) is a mesh-free Lagrangian numerical method suited to modelling fluids with a freely deforming surface. A two-dimensional SPH algorithm has been developed and applied to the problem of ship keel and bow-flare slamming. Freely decelerating drop tests of a model flared hull section were used as a basis for an initial validation of the SPH model. Relative vertical velocity profiles measured during tow tank experiments were then imposed on two-dimensional SPH models and reasonable agreement between the experimental and numerical slamming pressures was found. Finally, relative vertical velocity profiles calculated using SEAWAY software were implemented in the SPH algorithm, so as to simulate slamming on a typical V-form hull model.