Takayuki Asanuma

Experimental Evaluation of VIM on MPSO in Combined Environmental Conditions for Waves and Current

MPSO, mono-column hull type FPSO, is attracting the interest as a floating production system which has high performance for motion and large tank capacity in recent years.The authors had performed a mooring system safety evaluation of a MPSO named ‘MONOBR’ which was assumed to be installed at the Gulf of Mexico in the international collaborative research and development project between PETROBRAS and JOGMEC.There exists a strong current called the Loop current in the Gulf of Mexico. It is known that cylindrical floaters like SPARs or MPSOs sway with the long period and large amplitude in the transverse direction of the current. The motion is called Vortex Induced Motion (VIM), and is caused by vortex shedding from the sidewall of the floater. VIM is one of the important issues in the safety evaluation of mooring system of MPSO.Generally, the combined environmental conditions in which wind, waves and current exist are concerned for the safety evaluation of mooring systems. Therefore, it needs to estimate VIM in waves and current. The authors had performed the VIM measurement tests in order to investigate the estimation method of VIM in waves and current. The results of the VIM measurement test in waves and current and the results of the mooring safety evaluation method using the estimation method of VIM in waves and current are described in this paper.© 2012 ASME

Numerical Analysis for Hydrodynamic Motions of Floating Structure Using MPS Method

The authors started this research on estimation method of responses for floating structures using Computational Fluid Dynamics (CFD). This paper is first step, which has potential to be very valuable to the engineering community. The numerical method used in this study is the Moving Particle Semi-implicit (MPS) method

A Prediction Method for Horizontal Plane Behavior of FPSO Under the Single Point Mooring

It is well known that in single point mooring or anchoring the slowly varying oscillation of a ship is caused by action of current and wind. During the slowly varying oscillation, extraordinary tension occurs in the mooring line when the ship’s yaw angle becomes nearly maximum, and incurs, as the case may be, in breakdown of mooring lines or unforeseen drift of anchors. Floating Production, Storage and Offloading (FPSO) systems are often moored as Single Point Mooring (SPM) systems. SPM systems can be Catenary Anchor Leg Mooring (CALM) systems or Single Anchor Leg Mooring (SALM) systems. It has been required to predict and evaluate performance of horizontal plane behavior of FPSO in current, wind and waves, since the workability and safety of FPSO become important from the stand point of the Life Cycle Engineering. Numerical simulation is one of the practical methods for prediction of FPSO performance and it needs quite accurate values of hydrodynamic coefficients in the mathematical model. Recently some attempts on improvement of accuracy in prediction of the hydrodynamic coefficients were made and approximate formulae for hydrodynamic derivatives including the interaction effect of main hull form and appendages were also proposed. Recently extensive studies for numerical models which describe components of hull, propeller, rudder, thruster, wind and waves separately, and these interactions have been made successively. In this paper, first, the basic equations of maneuvering motion are explained. And, an estimation method of slender body theory for hydrodynamic force acting on the hull is outlined. The authors explain numerical models to obtain FPSO coefficients for the horizontal plane behavior from mathematical model of ship maneuverability. And, numerical test of FPSO under the slowly varying oscillation is carried out. Finally, a new mathematical model is proposed to describe the current forces acting on FPSO under the slowly varying oscillation.Copyright

PMM Test Analysis for Added Mass Coefficients of Asymmetric Bodies

Abstract PMM (Planar Motion Mechanism) test for an FPSO (Floating Production, Storage and Offloading) model of which form is asymmetric were carried out in order to obtain added mass coefficients of the model. Analysis procedure for calculating added mass coefficients of asymmetric bodies is presented. This procedure uses oblique motion test data. The procedure is applied to the PMM test data of the FPSO model. Added mass characteristics of the FPSO model confirm applicability of the procedure to analysis of PMM test data for calculating added mass coefficients of asymmetric bodies.

A Model Experiment of a Free Standing Riser in the Deep-Sea Basin

An experiment using a 1/70 reduced scale model of a Free Standing Riser (FSR) was carried in the Deep-Sea Basin of the National Maritime Research Institute in Japan. For instance, the model’s vertical pipe was about 32m long and the jumper was about 8m long. The FSR model had several measurement stations attached along the vertical pipe, subsurface buoy and jumper; and the motion of each station was measured in 3D by the Visual Measurement System. During the experiment, the effects of the jumper’s top end oscillation on the whole system were investigated. In this case, the top oscillation had propagated along the jumper; however the top oscillation had a reduced effect on the dynamics of the subsurface buoy and vertical pipe. In another experimental case, a current was generated in order to investigate the Vortex Induced Motion (VIM) on the FSR’s Subsurface Buoy. The VIM experiment was repeated for two different buoy models (a smooth cylinder and a cylinder with 3-start heli-coidally strakes) and the results were compared. In this article, some of the experimental results are presented and discussed.Copyright

Simulation of a Free Standing Riser Model and Validation With Experimental Results

In this article, we present the numerical analysis of a Free Standing Riser. The numerical simulation was carried out using a commercial riser analysis software suit. The numerical model’s dimensions were the same of a 1/70 reduced scale model deployed in a previous experiment. The numerical results were compared with experimental results presented in a previous article [1]. Discussion about the model and limitations of the numerical analysis is included.Copyright

Research on Low-Cost Design Method of Offshore Platform DPS before Construction

In this paper a description is given about the implementation of the Dynamic positioning system in the Seabex (special model ship) software of ship. The effectiveness of DPS is confirmed by numerical simulation and tank test using a model ship. This research is an effective approach to design an offshore platform DPS at one-tenth of cost of conventional method.

Research on the next generation dynamic positioning system of offshore platform in Japan

Abstract This paper describes dynamic positioning system developed for 20 years through research and development by Japan Oil, Gas and Metals National Corporation. It summaries a basic concept of design, simulator, tank test, and real applications. Also, the next generation system of Japan and its basic research is mentioned in the paper.