Hiroshi Sawada

Model Experiment on Parametric Rolling of a Post-Panamax Containership in Head Waves

Parametric rolling resonance in head waves was investigated experimentally. An experiment using a scale model of a post-Panamax containership was carried out in regular head waves at the 80 metres square basin of NMRI. In the experiment the wavelength, the wave height, the model speed and the encounter angle were widely varied to clarify overall property of parametric rolling resonance in head waves. As a result, conditions in which the head wave parametric rolling resonance is likely to occur and effects of the encounter period, the wave height and the encounter angle on parametric rolling amplitude were clarified. Moreover numerical simulations of roll motion of a ship in pure head waves were also carried out to investigate the property of parametric rolling resonance further.

Evaluation of the Weather Criterion by Experiments and its Effect to the Design of a RoPax Ferry

The guidelines of experiments for alternative assessment of the weather criterion in the intact stability code were established in IMO/SLF48, 2005. Following the guidelines, wind tunnel tests and drifting tests for evaluating wind heeling lever, \( l_{wl},\) and roll tests in waves for evaluating the roll angle, \( \phi_{1},\) were conducted. The results showed some difference from the current estimation, for example the wind heeling moment depended on heel angle and the centre of drift force existed higher than half draft. The weather criterion was assessed for allowable combinations of these results and the effect of experiment-supported assessment on the critical KG and so forth was discussed.

Study of Ship Responses and Wave Loads in the Freak Wave

In this study, we conducted tank experiment to measure ship responses to the Freak wave, Quasi Freak waves were generated utilizing focusing wave packet superposed on a regular wave train. Motion of the wave maker was determined in reference to wave simulations by our fully nonlinear numerical wave tank, NWT2D. An elastic model of a container ship was used to measure ship motions and whipping response. A time domain nonlinear strip method, SRSLAM, was used to simulate ship responses in the same incident waves. In this paper, the experimental and numerical results are presented and ship responses to the Freak wave are discussed.

A visualization technique of shipping water on running ship in regular head seas

Visualization of three-dimensional shipping water flow on running ship foredeck was conducted at the wave basin of NMRI. Two high speed video cameras, a mirror and synchronous stroboscopic sheet light were mounted on starboard deck and the shipping water on portside deck was observed through the transparent current plate attached along the centerline of the model ship. In this paper, the experimental technique for flow visualization is briefed and high speed video images are presented to show three dimensional features of shipping water motions.

Measurement of Shipping Water Flow by High-Speed Camera and Image Analysis based on PIV and PTV.

Flow visualization of shipping water was conducted to obtain the detailed experimental data for accuracy check of numerical simulation methods such as MPS and SPH. As simple models of foredeck of ships, two types of platform were installed in the two dimensional wave tank. One has a simple rectangular shape and another has a semi-cylindrical front shape. Using these models, 2D and 3D transient flow of shipping water was observed by high speed digital video cameras and synchronous stroboscopic sheet light. PIV and PTV were applied to obtain the velocity field. Outline of the work is reported in this short article.