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Shibata K.,University of Tokyo | Koshizuka S.,University of Tokyo | Sakai M.,University of Tokyo | Tanizawa K.,Japan National Maritime Research Institute
Ocean Engineering | Year: 2012

A three-dimensional ship motion model was developed using the moving particle semi-implicit (MPS) method to calculate a ship motion under high wave height conditions where shipping water occurs. The ship's hull was assumed to be a rigid body, and the interaction between the rigid body and fluid was simulated on the basis of weak coupling. A numerical wave tank was also developed to calculate a ship motion with minimum calculation costs. The numerical wave tank was able to create a series of waves and express the ship's relative forward speed. Using the developed ship motion model and the numerical wave tank, towing tests were numerically performed for five typical wave conditions. The calculated ship motions were compared with the experimental results. As a result, the nonlinear effect of shipping water was successfully simulated by the MPS method, although there quantitative differences between the calculated and experimental results still remained. This study shows the potential of the MPS method as a new simulation tool for calculating a ship motion in high wave height conditions. © 2012 Elsevier Ltd. All rights reserved. Source


Ueno M.,Japan National Maritime Research Institute
Ocean Engineering | Year: 2010

A submersible surface ship (SSS) is based on a novel concept that the SSS goes on surface like conventional ships in moderate seas but goes underwater in rough seas to the depth sufficient to avoid wave effects. The SSS has a wing system that produces downward lift to go underwater with preserving the residual buoyancy for its safety. The SSS is expected to be able to keep both safety and punctuality even if it encounters unexpected bad weather. The motion of the SSS is studied. The equations of motion are formulated and the procedures for estimating hydrodynamic derivatives are presented. The hydrodynamic derivatives are estimated for a SSS having a configuration, a hull with a pair of main wings and a pair of horizontal tail wings. Using these estimated hydrodynamic derivatives, calculation of the SSS motion is carried out. The calculation results show some specific aspects of the SSS especially for effects of the elevator of main wings and horizontal tail wings, aileron of main wings, rudder and propeller revolution. It is confirmed that the existence of static roll restoring moment and having large hull comparing with wing area play important roles in the motion of the SSS. © 2010 Elsevier Ltd. All rights reserved. Source


Matsuo K.,Japan National Maritime Research Institute
Nihon Kikai Gakkai Ronbunshu, C Hen/Transactions of the Japan Society of Mechanical Engineers, Part C | Year: 2010

This paper discribes a new system for a curved shell plate forming which is usually regarded as a special skilled work in a shipyard. The system has a characteristic to support a workman be engaged in a shell plate forming by indicating the logical way where to perform a press or a gas heating. The system adopts a new method for developing a curved shell plate to its appropriate flat plate by using geometric curvature lines found on the curved shell plate. This method has been translated as a software system, and has been introduced in a production lines by a one of the major Japanese shipyard. The system shows a good performance for an improvement of time consuming and an accuracy of a curved shell plate forming, according to the results of data calculated in the factory. Also, this paper introduces an example of application of the system to other works for a ship construction. Source


Oka Y.,Yokohama National University | Oka H.,Japan National Maritime Research Institute
Tunnelling and Underground Space Technology | Year: 2016

A series of fire tests was conducted in a small-scale tunnel with dimensions of 10.0 m (L) × 0.75 m (W) × 0.45 m (H) and a rectangular cross-section. Detailed measurements of the velocity and temperature within a steady fire-driven ceiling-jet running along the centre of the ceiling were conducted. Referring to a theoretical derivation process described in the literature as a starting point, correlations representing the velocity and temperature attenuation along the tunnel axis were developed. The values of the coefficients included in the developed correlation for the velocity attenuation were measured using a particle image velocimetry system during the experiments conducted in the small-scale tunnel. The value of the Stanton number was determined by considering the ceiling-jet thickness, which was derived from the velocity distribution. The values of the coefficients included in the developed correlation for the temperature attenuation were also determined based on experimental results described in the literature, which were obtained in a large-scale tunnel constructed using good heat insulation properties. Through these correlations developed for the velocity and temperature attenuations along the tunnel axis, the variation in the Richardson number of the ceiling-jet based on the distance from the fire source position along the tunnel axis was examined, and the position where the ceiling-jet changed from a shooting flow to a tranquil flow was determined. The boundary positions between the shooting and tranquil flows were determined using correlations between the velocity and/or temperature attenuation, which were compared with the variation in the Richardson number along the tunnel axis to verify their appropriateness. © 2016 Elsevier Ltd. Source


Sato Y.,Paul Scherrer Institute | Hino T.,Yokohama National University | Ohashi K.,Japan National Maritime Research Institute
Computers and Fluids | Year: 2013

A multi-color ordering method has been developed for the Gauss-Seidel (GS) method in the framework of the unstructured-grid based Navier-Stokes equations solver using OpenMP. The multi-color ordering method is required to avoid the data race condition in do-loop parallelization and to achieve the uniqueness of a solution of GS. A coloring algorithm of painting neighbor cells with different colors is proposed for the multi-color ordering method. The method is tested for four sample simulation cases: one case of two-dimensional simulation and three cases of three-dimensional simulation. Through the sample simulations, the uniqueness of the solution of the Multi-Color ordering Gauss Seidel (MCGS) method is verified, and the convergence ratio of MCGS is found to be in the similar level to that of GS and better than the Jacobi method. The parallel efficiency is examined for workstations with two hexa-core CPUs or two octa-core CPUs. Although the parallel efficiency is dependent on computer systems and simulation cases, the speed up ratio of MCGS reaches 14 using two octa-core CPUs in the maximum case using 14 million cells. © 2013 Elsevier Ltd. Source

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