Kunihiro Hoshino

Slamming load on a very large floating structure with shallow draft

The objective of this paper is to estimate the slamming load acting on a pontoon-type very large floating structure with a shallow draft. Experiments were carried out using elastic models with different rigidities in regular waves. The results revealed that the slamming load was strongly influenced by the rigidity of the model. The conditions under which slamming occurs depended on the extent of the bottom emergence and the velocity of the relative wave height at the bow of the model. These results were related to a simple procedure for estimating slamming load.

Development of three-dimensional shape measurement of the object in water

The purpose of this study is to develop the technology of measuring three-dimensional shapes precisely such as sunken ships and undersea harbor structure. The visible image acquired by the sound measurement and TV camera mounted on the ROV is used for measurement of the submarine topography and investigation of the sunken ship, etc.. However, the more detailed three-dimensional shape information compared to the ultrasonic image analysis is required concerning the inspection of the accident cause of the sunken ship. In this paper, the method for irradiating the object with dot matrix pattern of the green laser as a three-dimensional shape measurement method with small attenuation in water is proposed together with the technique which measures the three-dimensional shape of submerged object by scanning the single dot point at high speed on the object surface.

Real time measurements of air bubble and oil leakage in water using the 3D acoustic imaging instrument

On the seabed all over the world, the ships which sank during the war and marine disaster exist in great number. The cargo and fuel oil remain inside many wrecks. The wrecks become attenuated for long years. Then the oil is gradually discharged from the ship hull and rarely spouts resulting in a serious marine pollution. This paper describes the possibility of applying the Echoscope to the oil leakage monitoring and measurement method of the quantity of remained oil inside the tank using ultrasonic wave.

On the Quantity Measurement of Remained Oil inside a Sunken Ship Using the Ultrasonic Pulse-echo

A detecting method on quantity and oil existence in a model tank using ultrasonic pulse echo method have been assuming the remained oil inside sunken ships. C scope which is one of the method of the pulse-echo method was used for the construction of image. This experiment showed that the measurement of the remained oil inside the sunken ship was possible using ultrasonic pulse echo. The goal of this research will be the establishment of this technology to can measure remained oil inside sunken ships quantitatively and three-dimensionally by tomography-method using many measuring points.

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.

Flow Measurement by PIV around the Corner of the Box-shaped Very Large Floating Structure with Shallow Draft

For the structural feature of the Box-shaped Very Large Floating Structure(VLFS) with shallow draft, the VLFS may be subject to the large slamming load when its bottom happens to emergence in the state of the severe sea condition. Therefore, the safety of the VLSF against the slamming load has to be fully examined on its design stage.This paper describes the flow measurement using PIV concerning the deck wetness around the comer of VLFS in rough seas and the slamming due to the emergence of its bottom.