Makoto Sueyoshi

Application of CIP Method for Strongly Nonlinear Marine Hydrodynamics

Abstract A CFD approach based on the CIP (Constrained Interpolation Profile) method has been developed for predicting strongly nonlinear marine hydrodynamics. The numerical model uses a Cartesian grid for numerical solution and applies the CIP method for the flow solver and the free-surface interface capturing. An efficient interface capturing method by using a conservative CIP scheme is applied to two-dimensional sloshing. For strongly nonlinear wave-body interactions, a Cartesian grid method, in which the body surface is approximated by distributing virtual particles on it, treats the boundary condition at the body surface. A three-dimensional numerical simulation on a ship moving in large waves is presented.

Numerical Simulation Method for Damaged Ships Under Flooding Condition

Securing the survivability under flooding condition is one of the most important subjects in ship design. For realizing advanced assessment of damage stability, a numerical simulation method for damaged ships is developed by combining the moving particle semi-implicit method (MPS method) and the ordinary strip method based on potential flow theory. In this method, the flow field around the damaged hull including damaged compartments is solved by the MPS method and that around the intact hull is done by the strip method, separately. In order to validate the proposed method, model experiments are conducted for a damaged pure car and truck carrier in calm water and regular beam waves. Then numerical results of the ship motion and the flooding into the damaged compartment are compared with them. As a result, it is demonstrated that the proposed method has good potential for the prediction of dynamic behaviours of damaged ships under flooding condition.Copyright

Adaptation of a cyanobacterium to a biochemically rich environment in experimental evolution as an initial step toward a chloroplast-like state.

Chloroplasts originated from cyanobacteria through endosymbiosis. The original cyanobacterial endosymbiont evolved to adapt to the biochemically rich intracellular environment of the host cell while maintaining its photosynthetic function; however, no such process has been experimentally demonstrated. Here, we show the adaptation of a model cyanobacterium, Synechocystis sp. PCC 6803, to a biochemically rich environment by experimental evolution. Synechocystis sp. PCC 6803 does not grow in a biochemically rich, chemically defined medium because several amino acids are toxic to the cells at approximately 1 mM. We cultured the cyanobacteria in media with the toxic amino acids at 0.1 mM, then serially transferred the culture, gradually increasing the concentration of the toxic amino acids. The cells evolved to show approximately the same specific growth rate in media with 0 and 1 mM of the toxic amino acid in approximately 84 generations and evolved to grow faster in the media with 1 mM than in the media with 0 mM in approximately 181 generations. We did not detect a statistically significant decrease in the autotrophic growth of the evolved strain in an inorganic medium, indicating the maintenance of the photosynthetic function. Whole-genome resequencing revealed changes in the genes related to the cell membrane and the carboxysome. Moreover, we quantitatively analyzed the evolutionary changes by using simple mathematical models, which evaluated the evolution as an increase in the half-maximal inhibitory concentration (IC50) and estimated quantitative characteristics of the evolutionary process. Our results clearly demonstrate not only the potential of a model cyanobacterium to adapt to a biochemically rich environment without a significant decrease in photosynthetic function but also the properties of its evolutionary process, which sheds light of the evolution of chloroplasts at the initial stage.

Numerical and experimental study on a floating platform for offshore renewable energy

This paper presents recent experimental and numerical work on dynamic analysis and load prediction of a floating platform. A new offshore renewable energy platform is designed for the second stage on-sea experiment of Kyushu University. An experiment is carried out in the towing tank with a 1/50 scale model, to verify the hydrodynamic performance of the platform and to prepare a benchmark database for validation of the numerical simulation method. The in-house CFD code, RIAM-CMEN, is extended for numerical simulation of the platform in harsh sea conditions. Numerical simulation is carried out and validated against the experiment.Copyright

Numerical simulation of extreme motions of a floating body by MPS method

A numerical code based on the moving particle semiimplicit (MPS) method has been developed for time-domain simulations of extreme motions of a floating body. The MPS method is a gridless CFD technique that can treat incompressible flow with perfect conservation of mass and no numerical diffusion. The code can be applied to extreme motions of solid boundaries and large deformation of the free surface without numerical difficulties. There is no inconsistency even in handling the fragmentation and reunite of fluid. In this paper, an overview of the MPS method and details of the treatment in floating-body simulations are explained. Simulations of capsizing with flooding and porpoising with advance velocity are demonstrated as an application of the developed code.

Computation of Fully Nonlinear Wave Loads on a Large Container Ship by CIP Based Cartesian Grid Method

A Cartesian grid method with CIP (Constraint Interpolation Profile [1]) based flow solver has been developed and applied to many strongly nonlinear free surface problems. In this paper we present a research on applying the method to predict nonlinear wave loads on a container ship, which is advancing at a constant forward speed in regular waves with large amplitudes. Numerical computations are carried out on a head sea case and a bow sea case. The computed frequency response characteristics for the ship motions and the wave loads including vertical bending moments on the cross-sections and hydrodynamic pressures on the hull, are compared to a model test result and the result obtained by two potential flow based numerical methods. The nonlinear features of the numerical results are discussed.Copyright

Modelling and attitude control of a shrouded floating offshore wind turbine with hinged structure in extreme conditions

This paper addresses the modeling and attitude control of a novel shrouded floating wind turbine with hinged structure in harsh environmental conditions. Firstly, SimMechanics™ is applied to model the mechanical components of the wind turbine system. Secondly, the wave- and wind-loads acting on the system are respectively calculated based on Morisons equation and blade element momentum theory. Controllers of the elevator and the rudder located at the upwind side are designed based on linearized models to enhance the stability of the system. Numerical examples with three extreme weather conditions are finally performed to verify the effectiveness of the controllers. The results demonstrate that the pitching motion of the nacelle can be regulated to be within 3 degrees in the examples. In addition, the wind turbine could yaw itself stably toward the wind direction.

Three-dimensional Free Surface Flows Modeled by Lattice Boltzmann Method: A Comparison with Experimental Data

Three-dimensional numerical simulations of strongly nonlinear free surface flows are performed by lattice Boltzmann method (LBM), which features a number of performance-related advantages, particularly concerning data locality and parallel computing. A Multi-Passage-Interface (MPI) multicore processors parallelized free surface LBM solver is applied for the present three-dimensional numerical simulations. A Smagorinsky LES turbulent model serves to capture the small-scale turbulent structures of the flow. Experiments on dam breaking from previous articles are used to compare and verify two-dimensional (2D) and three-dimensional (3D) LBM model. A new experimental setup is also developed in order to observe the three-dimensionality effect. The findings demonstrated that the free surface LBM simulation agrees well with the experiments.

Lattice boltzmann method for free surface impacting on vertical cylinder: A comparison with experimental data

The purpose of the present research is to study three-dimensional lattice Boltzmann method (LBM) simulation on free surface impact phenomena with the validation on a newly performed dam breaking experiment. Large eddy simulation (LES) is implemented in the LBM to enhance the computational efficiency and to relax the restriction of the computational stability. The LBM method involves a surface-tracking technique with free surface algorithm. In this study, the present numerical simulation is validated by comparing wave front propagation and water level elevation with the experimental measurements. A three dimensional numerical simulation on dam breaking with vertical cylinder obstacles are performed and qualitative comparison with the experimental measurement has been made. Good qualitative agreement between numerical simulations and the experiments has been obtained in terms of free surface development, splash pattern and splash distance. For the square cross section cylinder, the water impacts on the cylinder violently and the flow is directed to the sides of the tank. For the circular cross section cylinder, the water flows smoothly around the cylinder and impacts tank wall violently. The results show that the free surface lattice Boltzmann method is efficient for dealing with complex geometrical problems.

Numerical Simulation of Deck Wetness for a 2D Pontoon-type Floating Structure

Numerical simulation of deck wetness for a 2D pontoon-type floating structure is carried out and the numerical results are compared with experimental ones. We use MPS(Moving Particle Semi-implicit) method which is a kind of fully Lagrangian type particle methods suitable for highly nonlinear wave-body interaction problems. In this paper, the numerical implementation of the particle method for floating body problems is explained briefly and some numerical results including comparison with experimental ones.