Maritime Research Institute Netherlands

About: Maritime Research Institute Netherlands is a nonprofit organization based out in Wageningen, Netherlands. It is known for research contribution in the topics: Turbulence & Computational fluid dynamics. The organization has 200 authors who have published 279 publications receiving 4382 citations. The organization is also known as: MARIN.

Improvement of Resistance and Wake Field of an Underwater Vehicle by Optimising the Fin-Body Junction Flow With CFD

Abstract: To control underwater vehicles appendages such as rudders or fins are generally used. These appendages induce added resistance and deteriorate the quality of the inflow to aft control surfaces or propeller, due to the formation of amongst others horseshoe vortices.In this paper, CFD is used to study the flow around a typical wing-body junction and to obtain insight in how to suppress the horseshoe vortex. For a generic submarine the impact of a range of modifications of the sail on resistance, propulsion and wake field is investigated. Design guidelines regarding the most promising modifications will be given. It will be shown that quite significant improvements of the resistance as well as the wake quality can be obtained by properly designing the junction between the appendage and the hull.Copyright © 2014 by ASME

Validation of an approach to analyse and understand ship wave making

Abstract: This paper discusses a rational and systematic procedure for understanding and analysing steady ship wave patterns and their dependence on hull form. A stepwise procedure is proposed in which the pressure distribution around the hull is invoked to provide a qualitative understanding of the connection between hull form and wave making. In a recent publication it was shown how this understanding explains various known trends and, in combination with wave pattern computations by free-surface potential flow or Reynolds-averaged Navier–Stokes (RANS) methods, can often be exploited to reduce wave making by modifying the hull form. The present paper provides support for the guidelines given, validates the decomposition into different steps and indicates the connection with previous theoretical approaches.

FPSOs: Design Considerations for the Structural Interface Hull and Topsides

Abstract: This paper discusses the structural interface on FPSOs between the hull structure and the topsides modules. It identifies the most common topsides foundation concepts applied on FPSOs, and discusses the consequences of each configuration for the layout of the unit, the design of the hull structure and the topsides. The information needed by the hull designer and the topside designer is identified. Moreover, the differences between shipbuilding and offshore construction design practices are discussed, and it is identified where and how these fall short for FPSO purposes. Topics that are addressed are overall safety, operational aspects, such as tank entry and mechanical handling, and the design specifications for the hull and the topsides modules. In order to control the schedule and costs of FPSO projects, fabrication of the hull and topsides should be allowed without impractical or unduly strict specifications imposed on the shipyard or the topsides fabricator. At the same time the traditional design specifications for hull and topsides design may fall short to cover the functional needs for FPSO service. Introduction To date, FPSOs have been in operation for several decades. Initially this development concept was selected for marginal fields in remote and environmentally benign locations. With the further advancement of sub-sea completions, flexible risers and turret mooring systems, the FPSO made its way in the nineties to harsher environments and larger development schemes that were previously uneconomical. Comparatively little investment had to be made in productionand export facilities, whereas the investment still had a residual value after depletion of the field as it could be re-deployed * Formerly with Nevesbu B.V., The Netherlands elsewhere. Furthermore, contractors emerged that were offering lease schemes, lowering the up front investments even further. With the shift of new discoveries towards ever deeper water, the FPSO is becoming more and more the default development platform for deep water for the years to come. Traditionally, an FPSO consists of a converted tanker with the production facilities, or topsides, mounted on deck. After only a limited conversion the oil tanker will fulfil all functional demands for storage and offloading of the produced oil. The most common project strategy is to contract large blocks of work, such as hull conversion, topsides and mooring system, to independent specialized contractors parallel in time. This is possible since the concept of an FPSO is robust: space on a tanker deck is ample, and mono-hulls are relatively weight insensitive. The downside of this approach is that (contractual) interfaces are created that need to be carefully managed in order not to jeopardise the successful completion of the project. Over the years, two types of FPSO projects have evolved. Conversions the ‘classic’ approach is to convert a ‘vintage’ tanker. This comprises an extensive Repair and Life Extension (R&LE) program, after which a conversion will take place to accommodate the mooring system, production facilities, utility systems and offloading system. Key advantages of this concept are the low purchase cost of the hull and the short lead-time. A large number of conversion candidates is available, especially now that a major part of the world fleet is being phased out because of MARPOL 13G regulations [1]. Down side of this approach is the high uncertainty embedded in the conversion scope: only after the detailed inspections have taken place in the conversion yard, the exact extent of steel renewals and equipment overhauls / replacements can be determined. This makes such projects very susceptible to budget and, more important, schedule overruns. To overcome this disadvantage, some project teams have opted for converting a ‘new’ tanker. This can be either a unit that is just delivered, or is still under construction. An example of this approach is described in [2]. When a tanker contract can be secured before start of construction, limited possibilities may exist to tailor the tanker specification to the FPSO requirements, e.g. by increasing scantling or material grades in certain areas. The down sides of converting a ‘new’ OTC 13996 FPSOs: Design Considerations for the Structural Interface Hull and Topsides M.H. Krekel, Bluewater Offshore Production Systems (USA) Inc., M.L. Kaminski, Maritime Research Institute Netherlands (MARIN) 2 M. H. KREKEL, M. L. KAMINSKI OTC 13996 vessel are the high purchase costs, while the full conversion scope remains intact. New builds are the most logical approach to take when a tanker conversion can not meet the project requirements for, for instance sea keeping, strength, endurance or size. In theory, a purpose designed new build FPSO can be built by one contracting party, but to date most of these units were contracted out as a number of sub projects, leaving the interface problems intact. Time has proven that purpose designed FPSO units are considerably more expensive, and have longer schedules than conversions. This because their ‘non standard’ specification requires an extensive engineering effort by the shipyard, and because the owner’s requirements, regarding e.g. materials, fabrication and coating, interfere with normal ship production. An alternative to a purpose designed new build is to opt for a ‘standard specification’ new build. Such a unit would conform to a shipyard’s standard tanker design with only minimal modifications to its specification. Typically these would comprise the omission of the propulsionand associated auxiliary systems, specification of an improved coating system, increased scantlings and higher material grades in certain areas. Interfaces As a consequence of the split project execution, contractual interfaces arise. The control and resolution of these interfaces is beyond the scope of this paper but has been the subject of many other publications, for instance [3]. General consensus is to minimise the interfaces between the various parties by contracting systems either fully in the scope of the shipyard, or fully in the scope of the topsides’ fabricator. Moreover, the responsibility for a system should remain with one party and range from design up to (pre-) commissioning. ‘Hand-over’ work should be avoided as much as possible. Noteworthy exceptions to these rules are the safety systems and electric power distribution systems as these are integral to the whole unit. In this paper it is not so much the system interfaces we consider but the structural interface between the hull and topsides. The topsides are fitted using foundations at a certain elevation above the hull’s upper-deck as shown in Figure 1. For the foundations between the upper-deck and the underside of the topsides, the following functional requirements apply: support the topsides modules on the hull, provide space for all deck piping and hull equipment, provide space for safe (tank) access and mechanical handling operations on the hull’s upper-deck, allow for sufficient natural ventilation of the upper-deck in order to prevent build-up of explosive gaseous mixtures, create a fire division / barrier between the topsides and hull upper-deck, create a division in the hazardous area classification for electrical equipment selection. The elevation between the upper-deck and the topsides flooring depends on how much clear height is needed underneath the topsides to fulfil the above requirements. For an Aframax size hull, a typical value of 3750 mm at the centreline has proved sufficient but the elevation is dependent on the topside arrangement, i.e. the main girder height of the topsides deck. Topsides, Pre Assembled Unit