SPE

Experimental Study On Behavior of Tandem And Side-by-side Moored Vessels

Hong, S.Y. (Korea Research Institute of Ships and Ocean Engineering, KORDI) | Kim, J.H. (Korea Research Institute of Ships and Ocean Engineering, KORDI) | Kim, H.J. (Korea Research Institute of Ships and Ocean Engineering, KORDI) | Choi, Y.R. (Korea Research Institute of Ships and Ocean Engineering, KORDI)

OnePetroMay, 2002

ABSTRACT Recently LNG FPSO is one of hot issues in offshore floating body dynamics, which requires accurate analysis of hydrodynamic interactions between two vessels; LNG FPSO and shuttle tanker. In many cases of conventional tandem mooring of FPSO and shuttle tanker, hydrodynamic interaction between FPSO and shuttle tanker was ignored under the assumption that the interactions are not so large to be accounted for. Such assumption implicitly presumed that ignorance of the hydrodynamic interaction gives conservative estimates of behaviors of both ships-FPSO and shuttle tanker. This paper aims to experimentally investigate basic interaction characteristics of tandem moored vessels and side-by-side moored vessels. Model tests were carried out for tandem moored tankers and side-by-side moored tankers in regular waves. Motion responses and drift forces of two vessels were measured and change of drift forces is mainly investigated. Interaction characteristics will also be investigated for change of distances between two vessels as well as types of mooring pattern; tandem and side-by-side moorings. All the cases of two-body interactions was compared with calculations using a higherorder boundary element method based on generalized multi-body interaction theory(Choi and Hong, 2001). INTRODUCTION Mooring pattern of conventional FPSO and shuttle tanker has been a tandem type in which offloading operation was carried out in such a way that shuttle tanker located sheltered region behind FPSO and distance between them is about l/4 to l/3 of ship length. While a new side-by-side mooring has been paid attention because of appearance of LNG FPSO-shuttle tanker system in which offloading operation is carried out under parallel position and distance between them is very close. In such a case of side-by-side mooring with very close distance between them, hydrodynamic interaction between FPSO and shuttle tanker becomes very important in operation as well as in design of mooring system.

OnePetro

ISOPE

ISOPE-I-02-389

The Twelfth International Offshore and Polar Engineering Conference

Genre:

Research Report > New Finding (0.40)
Research Report > Experimental Study (0.40)

Industry: Energy > Oil & Gas > Upstream (1.00)

SPE Disciplines: Facilities Design, Construction and Operation > Offshore Facilities and Subsea Systems > Floating production systems (1.00)

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Numerical Simulation of Float-Over Installation Under the Influence of Fender With Dynamically Positioned Vessel

Yi, Fan (Shanghai Jiao Tong University) | Liu, Tianfeng (Shanghai Jiao Tong University) | Wang, Lei (Shanghai Jiao Tong University)

OnePetroJune, 2018

ABSTRACT Dynamic positioning (DP) float-over installation is a new method for maritime structure installation, which uses a DP vessel to transport the topside of a jacket. When the DP vessel moves between the jacket leg, collision will happen because of environmental forces. To protect DP vessel and jacket, fenders are installed on the jacket leg. It is important to consider the collision between DP vessel and fenders. In this paper a numerical simulation for DP float-over installation is carried out, which simulates the dynamics of the DP vessel, and its collision with the fenders. The results are compared with model test. INTRODUCTION A dynamically positioned (DP) vessel is defined as a vessel that maintains its position and heading by means of active thrusters. (Zhao et al., 2002). Float-over installation is an offshore installation method. Topside is assembled on land and transported to the place of installation by vessel. Float-over installation is suitable for large platform installation. This method saves time and costs of installation. It has been widely used in recent years. DP float-over installation is a kind of installation method in which the vessel uses DP system to provide propulsion. In general DP float-over installation includes following process: standby operation, docking operation, mating operation and undocking operation. In docking operation, when the vessel moves between the jacket leg, the vessel will collide with jacket leg due to the influence of environmental forces. To protect the vessel and jacket leg, fenders will be installed on the jacket leg. The collision has a significant influence to the DP vessel. It is important to study the influence of fender force to the vessel. Wang et al. (2010) reviewed various floatover technologies based on the advancements in offshore installation and decommissioning technology. Applications of different float-over technologies is revealed. Maher et al. (2001) elaborated the process of float-over installation and carried out a numerical simulation and model test of float-over installation of SPAR. The technical feasibility of float-over installation is demonstrated. Hu et al. (2017) investigated nonlinear dynamics and impact loads during float-over installations. A more efficient model called state-space model is applied to evaluate part of the radiation force. The model, incorporating the multi-body interactions, is applied to study the nonlinear impact on Leg Mating Unit (LMU) by considering the sway, heave and roll motions of the float-over system. Serraris (2009) carried out a time-domain simulation for a drilling ship and compared the result with model test. The effects of different PID and Kalman coefficients are investigated. The choice of coeffcients has a significant influence on position keeping accuracy. Sun et al. (2012) investigated the interaction effects due to diffraction by a large volume substructure and an installation vessel. A two-stage hydrodynamic analysis was proposed. The multi-body diffraction problem is first solved without any constraints between the bodies, and in the second stage the constrained equations of motion are solved.

OnePetro

ISOPE

ISOPE-I-18-082

The 28th International Ocean and Polar Engineering Conference

Artificial Intelligence, collision, deviation, DP system, DP vessel, environmental force, fender force, float-over installation, jacket leg, model test, numerical simulation, operation, positioned vessel, subsea system, thruster, Upstream Oil & Gas, vessel model, wave angle

Country: Asia (0.47)

Industry: Energy > Oil & Gas > Upstream (1.00)

SPE Disciplines: Facilities Design, Construction and Operation > Offshore Facilities and Subsea Systems > Installation equipment and techniques (1.00)

Technology:

Information Technology > Mathematics of Computing (0.87)
Information Technology > Artificial Intelligence > Representation & Reasoning (0.54)

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Mooring of Surface Vessels to Piers

Chernjawski, Michael (M. Rosenblatt & Son, Inc.)

OnePetroJanuary, 1980

This paper presents a new analytical method of determining the tension forces in mooring lines of surface vessels. The method will aid the ship designer in developing fixed mooring systems with more accuracy than in the past. The analytical model developed considers the hull to be rigid and restrained broadside to a shallow-water pier with resilient fenders in use. The approach to the problem involves (a) determination of wind, current, and equivalent static wave forces at specified headings; (b) calculation of buoyant restoring forces caused by trim, heel, and immersion of the hull; (c) derivation of a combined mooring line stiffness matrix in terms of direction angles, lengths, cross-sectional properties, and nonlinear modulus of elasticity; and (d) derivation of generalized stiffness matrix for fixed mooring system and determination of tension forces in mooring lines using matrix algebra procedure and incremental load method. Special emphasis is placed on the cumulative elastic behavior of the mooring lines and on the manner in which the elasticity of the lines controls the vessel movement.

OnePetro

doi: 10.5957/mt1.1980.17.1.1

SNAME

SNAME-MTSN-1980-17-1-1

Marine Technology and SNAME News

Country: North America > United States (0.46)

Industry: Energy > Oil & Gas > Upstream (0.89)

SPE Disciplines: Facilities Design, Construction and Operation > Offshore Facilities and Subsea Systems > Mooring systems (1.00)

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Analysis of Vessels Moored in Shallow, Unprotected Waters

Schellin, Thomas E. (Germanischer Lloyd) | Scharrer, Manfred E. (Germanischer Lloyd) | Matthies, Hermann G. (Germanischer Lloyd)

OnePetroMay, 1982

Abstract Safe mooring of structures such as construction vessels, crane barges or pipe laying barges in shallow, unprotected waters presents unique problems. This is a consequence of the limited allowable horizontal excursion of the moored vessel due to relatively small displacement capability of the mooring system on the one hand and relatively large horizontal vessel displacements induced by waves extending into the range of rapidly increasing nonlinear mooring restoring forces on the other. This can result in highly peaked line tensions. The mathematical model used in this analysis attempts to accurately account for this phenomenon. This precludes linear or linear zed methods and, therefore, the analysis presented here is done with two different nonlinear methods. The first method models the vessel behavior directly by solving the motion equations under the influence of the combined first-order wave and second-order wave (drift) forces. The second method calculates first-order oscillating wave motions and second-order drift motions of the moored vessel separately and superimposes them to obtain total vessel motions. Line tensions due to the total vessel motions are calculated quasistatically with both methods. A sample analysis of a crane barge moored in shallow, unprotected waters shows results obtained with the two methods. Both methods predict highly peaked line tensions of similar magnitude and occurrence frequency, yet the calculated horizontal motions of the moored vessel are significantly different with the two methods. Introduction This study is concerned with the analysis of moored vessels in shallow, unprotected waters. Such situations arise, for example, during the mooring of construction vessels, crane barges or pipe laying barges in areas in which not necessarily the worst environmental conditions are to be encountered, however, which pose unique problems that affect operating performance. In such an analysis the environmental forces acting on the vessel are of central consideration. These are usually due to wind, current and waves and they each have special characteristics. Although wind velocities can vary drastically over a few seconds (e.g. wind gusts), the vessel in general does not respond noticeably to these gusts except as they contribute to the average wind force. Winds tend to be unidirectional over periods of a storm and current forces do not generally vary greatly with time. Therefore, both wind and current forces are taken as constant in the present analysis. The forces due to the irregular seaway must be treated as dynamically acting forces. These forces can be divided into first-order wave forces, oscillating with frequencies of the passing waves, and second order slowly varying wave (drift) forces. In order to analyze the response of the moored vessel it is necessary to specify vessel response characteristics as follows:–wind and current force characteristics –frequency response functions of hydrodynamic first-order wave forces acting on the vessel –frequency response functions of first-order vessel motions in waves –second order wave (drift) force coefficients vessel mass and inertia, including hydrodynamic "added" mass –vessel damping coefficients –vessel restoring force coefficients –mooring system characteristics. The analysis of mooring systems used to station offshore vessels tends to be complicated. Mooring system characteristics are influenced by numerous parameters.

OnePetro

doi: 10.4043/4243-MS

OTC

OTC-4243-MS

Offshore Technology Conference

Country:

North America > United States > Texas (0.28)
Europe > Netherlands (0.28)

Industry: Energy > Oil & Gas > Upstream (1.00)

SPE Disciplines: Facilities Design, Construction and Operation > Offshore Facilities and Subsea Systems > Mooring systems (1.00)

Technology: Information Technology (0.67)

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A Model Test for Docking Operations of a Transportation Vessel During Float-Over Installation

Kwon, Y. J. (Korea Research Institute of Ships and Ocean Engineering (KRISO)) | Nam, B. W. (Korea Research Institute of Ships and Ocean Engineering (KRISO)) | Kim, N. W. (Korea Research Institute of Ships and Ocean Engineering (KRISO)) | Kwak, H. W. (Korea Research Institute of Ships and Ocean Engineering (KRISO)) | Park, I. B. (Korea Research Institute of Ships and Ocean Engineering (KRISO)) | Jung, D. H. (Korea Research Institute of Ships and Ocean Engineering (KRISO)) | Sung, H. G. (Korea Research Institute of Ships and Ocean Engineering (KRISO))

OnePetroJune, 2017

ABSTRACT This study investigates the performance of docking operation in float-over installation. A series of model tests were performed at the Ocean Engineering Basin of the Korea Research Institute of Ships and Ocean Engineering (KRISO). The condition that one-fourth of the transportation vessel carrying the topside enters the jacket slot was tested. During the test, the vessel motion, line tensions, and fender forces were measured under various irregular wave headings i.e. head sea and beam sea. The relation between the vessel surge motion and line tension was investigated under head sea waves. Wave period effects were also studied in the condition of peak period 5s to 8s. To validate the experimental data, numerical simulations were performed. Numerical additional damping was found the main factor for surge motion in head sea condition. The relation between the sway and yaw motion of the vessel and tension of lines was discussed in beam sea waves. Fender effects were also studied in these conditions. Response characteristics about fender forces and the vessel motion relatively well implemented in the numerical simulations. INTRODUCTION There are two methods for the installation of a topside in offshore. Due to the limitation of allowable lifting weight in lifting operations, float-over operations had been used to install the heavy integrated topside. Float-over scenarios are typically divided into five parts : Stand by, Alignment, Docking, Mating and Undocking stage. Mating stage is the most important stage in topside load transfer and dynamic load of hardware such as LMU, DSU. Docking stage is the significant stage like mating stage. It is the sensitive stages related to operability and workability in float-over installation. Mating, mooring lines and fenders were used to help the entry of a transportation vessel in docking stage. Jillian Duquesnay et al., (2013) addressed docking and undocking considerations for float-over analyses and operations. The considerations are float-over procedure, hardware, slot configuration, weather, workability, tides, mooring and mating lines. According to slot configuration i.e. tight slot and loose slot, complexity of float-over hardware and component can be different. A complex fender system is required in tight slot condition. Whereas LMUs, DSUs, mating lines and mooring system is less complex due to restricted lateral motion in this condition.

OnePetro

ISOPE

ISOPE-I-17-063

The 27th International Ocean and Polar Engineering Conference