Search

This article deals with the development of a numerical tool based on an integrated synthesis model to carry out the first project cycle of floating liquefied natural gas (FLNG) platforms to produce, process, store, and export liquefied natural gas (LNG). The topside configuration, tank geometry and capacity, production levels, equipment list, environmental and operating conditions, classification society requirements, structure, stability, and seakeeping are considered in a single synthesis model, generating a sufficiently large number of solutions. The case generation and the evaluation process are performed hierarchically, dividing the parameters into groups to better solve the solution space, which cannot be achieved with conventional techniques such as traditional point-based design. This methodology is applied as a case study to design three FLNG platforms with different production levels (2, 3, and 4 million metric tons per year). Performance parameters are defined and evaluated, optimizing downtime, structural mass, and load capacity. The resulting platforms are compared to existing FLNG dimensions. Essential conclusions are drawn about design improvements, such as key dimensions, quantity, and configuration of tanks, freeboard specifications, and operating draft. The developed synthesis framework proved to be a quick and useful tool for the early stages of the FLNG project.

This paper presents a new challenge under study in Brazil: the offshore storage of natural gas and CO2 in salt (halite) caverns opened by solution mining in shallow and ultradeep water. The salt rock mechanics in Brazil started with the underground mining of sylvinite (NaCl.KCL) overlying tachyhydrite (CaCl2.MgCl2.12H2O) and research initiated in the 1970s (Costa 1984), to enable the mining of this ore. Applying a numerical simulation of drilling and excavation, the exploration and operation of mines were possible for more than 35 years. The same technology has also been used in the stability analysis of several salt caverns opened by solution mining of halite (NaCl). With the discovery of the giant pre-salt reservoirs in Brazil, underlying about 2000 m of stratified salt rocks, with the presence of tachyhydrite, all the knowledge acquired in the conventional and solution mining designs was ready to be used. More than 200 pre-salt wells have been designed and drilled successfully using the same methodology and computer codes. These approaches are proposed here as a solution to the presented challenge.

This paper presents a proposal for an experimental salt cavern in offshore ultra-deep water for CO2 abatement, including the instrumentation plan and well conceptual design evaluated for carbon capture and storage (CCS) application. These studies are based on applied computational mechanics associated with field experimentation that has contributed to the technical feasibility of the underground potash mine at the State of Sergipe in Brazil. This knowhow allowed the stability analysis of several salt caverns for brine production at the State of Alagoas in Brazil and to the drilling through stratified thick layers of salt of the pre-salt reservoirs in Santos Basin. Now, this knowledge has been applied in the design of onshore and offshore salt caverns opened by dissolution for storage of natural gas and CO2. The geomechanical study, through the application of computational mechanics, of offshore giant salt caverns of 450 m high by 150 m in diameter, shows that one cavern can store about 4 billion Sm3 or 7.2 million tons of CO2. Before the construction of the giant cavern, which will be the first gas storage offshore in the world, it has been decided to develop an experimental one, with smaller size, to obtained field parameters. The experimental cavern will allow the calibration of parameters to be used in the structural integrity analysis of the cavern and well for storage of natural gas which is rich in CO2 under high pressure.

The offshore oil exploration in the pre-salt layer of Brazil is performed in ultra-deep water (above 2000 m) at 200 NM from the coast. The large distance from the coast provides a large downtime for the OSV (Offshore Supply Vessels) operations due to crew exchange, which is also increased due to port’s queue. The application of High Speed Vessels (HSV) as a crew boat to support offshore operations is a challenge since the required speed (above 25 knots) provides a large fuel consumption, which could be optimized by reducing the displacement, wetted surface and considering a multi-hull concept. However, the low displacement of these solutions usually provides a bad seakeeping performance, mainly under the harsh environmental conditions of Santos Basin. A large trimaran concept is proposed to support this mission, which requires an accurate prediction of either ship resistance or seakeeping performance in order to achieve the required uptime. A large experimental campaign was performed at IPT towing tank in the presence and absence of waves for the evaluation of calm water resistance, added resistance and seakeeping considering some pre-established conditions. The experimental data is applied to validate the Finite Volume Methods model to predict ship resistance in calm water, which is combined to the estimative of added resistance using strip theory and BEM to obtain the total ship resistance. The seakeeping performance is also validated using experimental data regarding regular waves and extended to irregular sea state conditions using spectral theory. The numerical models are applied to estimate the vessel performance considering the entire metocean conditions of Santos Basin providing the expected uptime.

This paper presents the quantitative evaluation of influence of liquid sloshing on FLNG motion. The numerical analysis of coupled floating motion of FLNG with six (6) rectangular tanks was performed and the result was compared with the experiment. Then, two (2) case studies to assess the sloshing effect on FLNG were performed, followed by the investigation of sway and roll motions in the irregular seas.

The new regulations regarding ship emissions based on IMO regulations combined to the high fuel prices require the application of new technologies to improve ship efficiency and to reduce the CO2, NOX, SOX and BC emissions. The application of LNG as fuel and battery packs to improve the conventional engines performance are already a reality in offshore supply vessels (OSV) around the world. However, the reduction in OPEX and payback time of the additional investment is very dependent of the ship operational profile, which are related to the FPSOs and port facilities particularities in Brazil. In order to estimate the advantages of these technologies in the PSV overall performance several different simulators regarding DP operation, sailing, waiting and anchored mode are combined to obtain a digital twin of the vessel. These simulators are combined to the real data monitored from the ships regarding ship speed, position and heading collected in Brazil based on AIS/AIS-Sat database. This database is combined to the environmental conditions regarding wave, current and wind obtained based on global numerical models to provide the environmental loads acting in the ship during the different stages of the operation. The DP simulations are performed applying a thrust allocation algorithm, the calm water resistance is obtained based on regression models and the added resistance due to waves are computed based on strip theory. The forces are converted into electric load by considering the propeller, generators, switchboard, electric drive and engine efficiency curves combined to a power management system (PMS) algorithm, which balance the loads in the engines according to the operational mode. The baseline for comparison is the current PSV without dual-fuel engines or battery pack.

In 2006, giant oilfields were discovered in Brazil in a water depth of ∼ 2200 m and under a caprock of 2000 m of continues salt rock overlaying the reservoirs, called pre-salt. Currently more than a half of the Brazilian oil and gas production comes from these reservoirs. However, some of these assets have big Oil & Gas ratio with a high level of CO2 contamination, which are currently being reinjected in the reservoirs. This procedure gradually increases the CO2 content associated with the oil extracted, reducing well productivity and leading to high costs of CO2 and CH4 separation by the membrane technology. The Research Center for Gas Innovation (RCGI) located at the State University of São Paulo in Brasil, sponsored by Shell Brazil, is developing a technology that uses the thick layer of salt rock overlying the pre-salt reservoirs to build caverns where the contaminated gas will be injected and decontaminated. After 2 years of extensive research, several studies have been carried out to analyze the main critical aspects of the technology in order to evaluate its feasibility, and now it has been decided to advance to the field proof stage. The salt dome studied can accommodate the construction of 15 caverns, thus providing the confinement of approximately 108 million tons of CO2. Before the system be construct in full scale, it was decided to initially build an experimental cavern with smaller size to obtain field parameters of the final design of the caverns. This paper describes this development denominated Offshore Salt Cavern Ultra-deep Water CCS System, that aims to perform the natural gas storage, a natural gravitational separation between CO2 / CH4 inside the caverns, and the confinement of CO2 (CCS). It presents important results related to structural integrity analysis of the giant and experimental caverns, well design using the same methodology applied in more than 200 projects of the pre-salt oil wells, instrumentation plan of the experimental cavern, storage capacities and other relevant data. If the economics proves feasible, this offshore gas storage station will be the first of its kind and possibly the biggest CCS Project in the world.

This paper discusses the coupling influence of floating LNG (FLNG) motions with internal liquid sloshing. Model experiments were performed in an ocean model basin, and results were compared with numerical calculations. The FLNG model used in our study had six square tanks. To verify the liquid cargo effect, the FLNG model was tested under two conditions: a liquid cargo condition and a fixed solid-cargo condition. As for filling level, there were three loading conditions (15%, 50%, and 90% filled). Our numerical scheme solves internal liquid sloshing using a three-dimensional finite difference method, and ship motion by potential theory. The sloshing effect was computed by the time-domain coupled simulation. We obtained good agreement between experimental and numerical results even at the near-natural frequency of sloshing. In both experimental results and numerical simulations, the effect of internal liquid is significant for sway and roll motion. Furthermore, the internal free surface motions obtained by the experiments and numerical simulations showed similar non-linear free surface behavior in the case of low filling.

In recent years, the use of natural gas has remarkably increased due to growth in energy demands and concerns about the environment. Generally, pipelines are used for liquefied natural gas transportation; however, there are technical problems and cost increases in constructing liquefied natural gas pipelines in the deep sea. For this reason, floating liquefied natural gas system has attracted the attention of the industries, governments and academia. One of the major issues to be overcome in realisation of floating liquefied natural gas is the motion prediction of close-proximity floating bodies including the gap resonance between the two bodies. In this article, three steps were carried out in order to understand the ship motions and the gap resonance and their effects to the side-by-side offloading operations. First, the two-dimensional gap resonance between the two bodies was investigated using a viscous flow numerical method. Second, the three-dimensional gap resonance and the floating body motions were studied using a potential flow method and validated by the experimental model test. Finally, the limits of environmental conditions for the side-by-side offloading operations were examined by the results of numerical calculation.

With respect to the design of FLNG systems, the sizing of tanks is a major subject that impacts several areas. The use of fewer number of tanks reduces construction costs significantly. However, very large tanks have a large liquid cargo motion. This motion inside tanks is generally studied because of the impact on the structural design of tank walls. Many effects such as sloshing, trapped waves, breaking waves occur inside a tank and the problems caused by then are more than simple structural issues. In this work, an experimental arrangement was set up to investigate the influence of the liquid inside the tanks in the wave behavior of FLNG. The study comprised the vessel evaluation both in isolated and in side-by-side configurations. The latter considered the vessel operating close to an LNG carrier, emulating an offloading operation. The FLNG model was equipped with six acrylic tanks filled with water at three different levels: 15, 50 and 90%. In addition, the same cases were tested with corresponding solid ballasts to evaluate the impact of the liquid movement. In the side-by-side configurations, the models were equipped with fenders and connection lines. In addition, wave probes were used to measure the wave elevation in the gap between the vessels. The results are presented and discussed in terms of the comparisons: isolated versus side-by-side and solid cargo versus liquid cargo.

In sequence of Part 1 of this two-part paper, this article describes the development and application of an optimization model developed for the design of a floating breakwater that has the main function of protecting large LNG vessels from sea waves. The model consists basically of a parametric model coupled to an optimization algorithm that evaluates a variety of breakwater geometries and searches for the one presenting the lowest construction cost, subjected to different constraints such as wave attenuation capability, stability margin, maximum structural loads, and uptime level. This methodology is applied to Uruguay’s coastal waters, which place is chosen because it presents harsh sea states in the Atlantic South region and would thus represent a big challenge for the feasibility of a floating breakwater. Results are discussed in terms of the geometry that presented the lowest cost considering an uptime level greater than 90%. For this geometry, a mooring system arrangement is also proposed in order to keep breakwater positioning passively while satisfying the maximum offset requirements.

Part 1 of this two-part paper presents the development of a parametric model for the design of a floating breakwater conceived to protect a LNG terminal. The model is composed by a set of numerical scripts that perform the classical steps of a typical design spiral in order to evaluate weights and centers, stability margins, structural loads, wave attenuation capability, and seakeeping performance. Each of these models is discussed in terms of sensitivity analysis, which demonstrates the influences of different parameters in the global design. Especial attention is given to the analysis of the structure wave attenuation capability, in which the effects of water depth, underkeel clearance, wave period and direction, breakwater motions are investigated.

The development of a the design process for a PSV floating terminal conceived to attend the future demands of drilling rigs that will be operate at oil fields located in the North and Northeast of Brazil is presented. The analyses are conducted by applying a synthesis model in which the main dimensions of the structure are varied in a thorough search, aiming at finding the floating structure that attends a specific uptime level, considering restrictions in terms of stability and wave elevation at the PSV berth. After this optimization process, the best solution is detailed with the design of a proper mooring system and an efficient mooring arrangement for the PSV, which included the definition of some equipment positions on the quay. As a result, a floating terminal conceptual design is presented, demonstrating to be technically feasible and a promising alternative to be applied in place of very time-consuming civil constructions related to offshore and port infrastructures.

The fuel consumption analysis of a Suezmax tanker customized to the offloading operation in the brazilian coast is performed in order to verify the possible savings produced by the so-called “slow steaming” technique during navigation. This ship is equipped of a single engine/propeller but there is a trend of building new vessels considering an equivalent two engines–two propellers for better safety during navigation and offloading operations, therefore a comparison regarding the propulsive efficiency, fuel consumption, and operational conditions (max engine power, rotation, and cavitation limitations) is performed in order to verify the benefits of this new concept. The methodology applied is based on a mixed approach considering numerical simulations using CFD (computational fluid dynamics) and regression models available in the literature: the first one applied to compute the ship resistance and nominal wake fraction in the propeller plane and the second one applied for the propulsive efficiency prediction, as the propeller curves based on Wageningen B-series. The specific fuel oil consumption curves were obtained from the engine manufacturer catalogue.

A hydrodynamic analysis is realized to predict the ship resistance of an inland vessel for cargo transport the Magdalena River lower course. The analysis is applied numerically by solving the 3D Reynolds-Averaging Navier-Stokes (RANS) equation together with the standard k-e model for turbulent effects, allowing the simulation of the viscous and pressure effects around the hull in a towing tank as long as the wall bottom and the side effects in the shallow water navigation. The Finite Volume method is applied for the discretization of flow domain. The Volume of Fluid (VOF) is used for the capture of the free surface, in which the formation of the waves is generated during the navigation of the inland vessel.

The interaction between two floating vessels has been a subject of much study in recent years due to its relevance to floating liquefied natural gas (FLNG) developments. The safety and operability of these facilities are directly influenced by the wave elevation in the gap between the two vessels as well as the relative motions between the vessels. In the industry, it is common practice to use potential flow models to calculate free-surface responses under various wave conditions. Given that these numerical models are inviscid, calibration of additional damping terms are usually carried out using model tests to in order to account for the viscous dissipation on the gap hydrodynamics. However, it is known that the dissipative effects of viscosity may be nonlinear and thus, model test data obtained using one set of wave conditions may not be suitable for use in another scenario. In this paper, model experiments of two identical side-by-side barges of 280m (length) × 46m (breadth) × 16.5m (draught) under various wave excitation are described. The experiments considered a range of parameters such as gap width, wave heights, periods and wave directions. The results obtained for each set of these parameters are discussed and compared between the two types of incident waves (regular and irregular).

Offshore structures design and validation currently involves complex numerical simulations and experimental verifications using reduced models. These experiments are usually conducted in ocean wave tanks. The wave focalization using time reversal is a well-known technique in the field of acoustics. It was proved using several physical waves, but was not experimentally tested in ocean wave in the scale of a wave tank. For this purpose, the tank of the University of Sao Paulo was used for these experiments. The tank has 148 flaps equipped with wave probes for control feedback of active wave absorption. Hence, the waves can be recorded and re-emitted by the flaps. The time reversal technique is here experimentally evaluated in order to generate focused waves in water tests. First, a small object dropping into the tank water acts as a source of impulsive wave for time reversal experiments. In a second experiment, a reflective wall is introduced into the tank, in order to distort the wave propagation and generate wave reverberations. The results show the ability of the time reversal technique to focalize impulsive waves back at the origin, even in the case of obstacles to the wave propagation.

This article presents a Technology Readiness Assessment (TRA) of a new concept called the Salt Cavern Hybrid Subsea Carbon Capture and Storage (CCS) System, which performs all the offshore natural gas and CO2 separation process with subsequent storage in offshore underground salt caverns. Currently there is a demand for CCS of large quantities of CO2 associated with CH4 in the pre-salt offshore oil fields in Brazil. The pre-salt reservoirs have as caprock 2000 m of continuous rock salt. This hybrid system is expected to perform, at the same time, the separation between the natural gas and CO2, and Carbon Capture and Storage of CO2, allowing the monetization of the separated natural gas. The Technology Readiness Levels (TRL) approach is discussed in this paper for estimating the maturity of the CCS System. The TRL analysis concluded that no technological gaps were identified that would made the project unfeasible and the TRL level enables the project to advance to the field test stage within a reasonably short time horizon. Once implemented it could be one of the largest CCS projects in the world. Also, this paper describes the conceptual design of this hybrid system and presents the results of a TRA showing the methodology that was employed in the process, the technology critical items that were analyzed and the results obtained for each of them and the design of a salt cavern for the storage of 1 billion Sm3 (Standard cubic meter) of a natural gas stream with high CO2 content.

This article describes a new concept to reduce carbon dioxide emissions of offshore oil production of high gas-to-oil ratio reservoirs and high content of CO2, denominated Offshore Salt Cavern Ultra-deep Water CCS (Carbon Capture and Storage) System. This hybrid system is intended for natural gas storage, the gravitational separation between CO2/CH4, and CO2 confinement for final destination. This development emerged from a current demand of some Brazilian pre-salt reservoirs to destinate a gas stream with high CO2 contamination, produced during the oil extraction. These reservoirs have a continuous salt rock layer of 2000 m as caprock making the construction possible of salt caverns by leaching using seawater. In the first stage of technology development, the system will only store a gas stream contaminated with a high concentration of CO2. In the second stage of its development, it will allow not only the separation of natural gas from the CO2 but also its storage and the monetization of CH4. This paper presents the conceptual design of this technology, showing the steps from the parametric study to select the best relation between flowrate, leaching time, structural stability, and the volume of gas with the high content of CO2 storage, up to the final geomechanical design using the set of parameters selected.

The aim of this paper is to present the development of an ecological and efficient shuttle tanker structural parametric model with optimized capacity that was designed to operate at the Brazilian pre-salt region. Such a model estimates the weights and centers of the bare hull, as well as the structural weight, the center of gravity of the ship, and the moments of inertia at different dimensional, geometric, and capacity features of the ship from structural elements of the parallel middle body. These elements were automatically dimensioned at a MATLAB® environment. After an exhaustive search method through several dimensioning cases of these elements, the lowest structural weight was obtained, which satisfies the rules of classification societies. Finally, the results are shown as a response surface, which was built by means of artificial neural networks. These allow assessing the behavior of weights and centers characteristics of the ship, based on the variation of design parameters.

This paper presents a few hydrodynamics analyses of two corvette hulls with different operational profiles (corvette 1 with maximum maintained speed of 25 knots and corvette 2 with 35 knots), which designs follow some Brazilian Navy high-level system requirements and are based on modern world military vessels. The total resistance coefficient and wave pattern were determined from computational fluid dynamics simulations using free surface models and ITTC procedures, and the form factors of both ships by Prohaska’s method and CFD simulations at low Froude numbers (to neglect the wave resistance). A preliminary numerical analysis of bulbous bow was carried out using CFD, and it was possible to notice that, at high Froude numbers, the ship resistance substantially decreased if compared to the bulbless hull and, with low Froude numbers, the resistance subtly increased. Moreover, the propulsive arrangements of both ships were predimensioned and it was possible to notice the differences due to the operational profiles. Corvette 1 has a combined diesel and diesel propulsion system with two controllable pitch propellers, which optimum pitch was defined using the OpenProp software and the wake field from CFD. Corvette 2, which has a broader range of speed, has a propulsive arrangement of two waterjets and a gas turbine at high speeds, and a CPP with diesel engines when operating at low speeds.

The offshore oil fields exploitation, especially giant fields in the Santos basin, brings with it demands for systems capable of operating at ultra-deep waters, with high capacity production wells and high gas/oil ratio (GOR) with large amount of contaminants. In this scenario, steel catenary risers (SCRs) offer the simplest, most robust and lowest cost solution. However, due to its rigidity compared to flexible risers, this solution is affected by the high dynamic forces imposed on the top of the riser, in consequence of the FPSOs large vertical movement in waves, making difficulties on their application in conventional FPSO hull units. This dynamic problem is caused by environmental conditions of the region, which are harsher than those observed in the Campos Basin. The reservoir characteristics described above demands high-capacity oil & gas process plants, larger than those used today in the Brazilian offshore. Initial estimates show that these plants require a much larger deck area than conventional platforms and, more than that, a greatest breadth of the vessel. This paper presents the ULFPSO (Ultra Large Floating Production, Storage and Offloading) concept, developed to satisfy such conflicting requirements. The design process, including the preliminary sizing, physical scale model test and the hull form optimization are discussed and presented in this paper based on a high-capacity process plant case study.

This paper presents the new active absorption wave basin, named Hydrodynamic Calibrator (HC), constructed at the University of Sao Paulo (USP), in the Laboratory facilities of the Numerical Offshore Tank (TPN). The square (14 m × 14 m) tank is able to generate and absorb waves from 0.5 Hz to 2.0 Hz, by means of 148 active hinged flap wave makers. An independent mechanical system drives each flap by means of a 1HP servo-motor and a ball-screw based transmission system. A customized ultrasonic wave probe is installed in each flap, and is responsible for measuring wave elevation in the flap. A complex automation architecture was implemented, with three Programmable Logic Computers (PLCs), and a low-level software is responsible for all the interlocks and maintenance functions of the tank. Furthermore, all the control algorithms for the generation and absorption are implemented using higher level software (MATLAB®/Simulink block diagrams). These algorithms calculate the motions of the wave makers both to generate and absorb the required wave field by taking into account the layout of the flaps and the limits of wave generation. The experimental transfer function that relates the flap amplitude to the wave elevation amplitude is used for the calculation of the motion of each flap. This paper describes the main features of the tank, followed by a detailed presentation of the whole automation system. It includes the measuring devices, signal conditioning, PLC and network architecture, real-time and synchronizing software and motor control loop. Finally, a validation of the whole automation system is presented, by means of the experimental analysis of the transfer function of the waves generated and the calculation of all the delays introduced by the automation system.

The increasing demand for natural gas is encouraging the development of novel floating units’ designs, capable of processing large quantities of hydrocarbon. These units called FLNG (Floating Liquefied Natural Gas) are facilities that produce, process and store liquefied natural gas (LNG) offshore. Once the topside and tanks of a FLNG are larger and more complex than the regular FPSO vessels, a design process considering these particularities must be used. Once just few FLNG units are under construction and under design and not yet in operation, the information on the design first stages is poor. It is difficult to obtain a first hull sizing without taking in account the complexity mentioned above. Thus, a set-based approach that works with sets of possible solutions that are analyzed and compared using a merit function in order to select the best and feasible solutions was used. However, to produce a sufficiently large family of solutions, which includes most of the solution space, either the solution descriptions or the models must be simplified. From the computational point of view, the analyses of a family of design solutions basically relies on an initial parameterization of the object and a set of mathematical models that, as a group, will be referred as synthesis model. Additionally, some restrains are also applied to eliminate unfeasible solutions. The output of the synthesis model is a set of performance quantities that will be used to rank the solutions. This design approach is particularly useful to deal with project trade-offs and to optimize multiple characteristics. Optimal solutions belongs to a surface (or a hyper surface) called Pareto boundary. This paper aims to achieve a platform design capable of producing, storing and offloading liquefied natural gas. It must safely survive under environmental conditions of Santos Basin in São Paulo, Brazil. In the same way, the design should guarantee the shortest downtime as well as keep costs, of acquisition and operation, as low as possible. Each of these characteristics must be quantified to allow a ranking of the generated solutions through an objective function. Capacities, production rates, equipments, load distribution, environmental actions, stability, sea keeping and structural design estimates are the major areas to consider and will be related to one or more mathematical models, constraint and objective functions. The work will present a general overview of each model separately and how they work together, as well as examples of solutions and analyses depending on the input values. It must be clear that this approach is applicable just in the early stages of design to obtain the first hull sizing. After that it is necessary to fall back on the traditional iteration process to rely in a feasible design.

O artigo aborda as diversas pesquisas feitas no campo da produção do petróleoe que levaram o Brasil à descoberta de reservas de hidrocarbonetos abaixodas camadas salinas, ou seja, em locais até então considerados não propícios.Nesse sentido, destaca o Centro de Pesquisa e Desenvolvimento da Petrobras(Cenpes) e a participação da Universidade de São Paulo nesse processo.

In order to investigate the effects of an elastically-linked moving body on liquid sloshing inside a tank, an analytical formulation and a numerical approach were proposed to assess hydrodynamic loads in a partially filled rectangular tank with a body connected to the tank by springs. The analytical approach was developed based on the potential theory to calculate fluid velocity field, and the dynamics of the liquid sloshing coupled to the moving body are described as a mechanical system with two degrees of freedom. The coupling between the fluid and the moving body is given by a damping force calculated based on the body geometry and the fluid velocity field. The proposed numerical approach is based on the Moving Particle Semi-implicit (MPS) method, which is a Lagrangian particle-based method and very effective to model nonlinear hydrodynamics due to fluid–structure interaction. In the numerical approach, the rigid body is modeled as a cluster of particles and the motions are calculated considering its mass, moment of inertia, hydrodynamic loads and springs restoring forces. The elastic link between the body and tank is modeled by applying Hooke’s law. Simple cases of floating body motion were used to validate the numerical method. Finally, analytical and numerical results were compared. Despite its simplicity, the analytical approach proposed in the present work is an efficient approach to provide qualitative understanding and a first estimate of the moving body effects on the sloshing inside the tank. On the other hand, the numerical approach can provide more detailed information about the coupling phenomena, and it is an effective mean for the assessment of the reduction of the sloshing loads due to the moving body with elastic link. Finally, the effectiveness of the concept as a sloshing suppressing device is also investigated.

Previous papers related to the optimization of pressure vessels have considered the optimization of the nozzle independently from the dished end. This approach generates problems such as thickness variation from nozzle to dished end (coupling cylindrical region) and, as a consequence, it reduces the optimality of the final result which may also be influenced by the boundary conditions. Thus, this work discusses shape optimization of axisymmetric pressure vessels considering an integrated approach in which the entire pressure vessel model is used in conjunction with a multi-objective function that aims to minimize the von-Mises mechanical stress from nozzle to head. Representative examples are examined and solutions obtained for the entire vessel considering temperature and pressure loading. It is noteworthy that different shapes from the usual ones are obtained. Even though such different shapes may not be profitable considering present manufacturing processes, they may be competitive for future manufacturing technologies, and contribute to a better understanding of the actual influence of shape in the behavior of pressure vessels.

One of the most difficult challenges in the offshore industry is to reduce hydrocarbon production costs, which increase as exploration advances to deeper water regions. Most of the Brazilian oil companies demand the use of a conventional ship-shaped FPSO (Floating Production, Storage and Offloading System) as a solution for offshore production due to the lack of pipelines, soft local environmental condition, and the characteristics of the oil fields. However, the small roll damping and the relatively large heave motions of the FPSO pose some limits to the use of rigid risers and nearly forbid the use of dry tree completion system facilities. In order to make the application of rigid risers and dry tree completion feasible on an FPSO, Brazilian universities and research institutes, in a partnership with Petrobras, have developed a new concept of a hydrocarbon exploration and production platform - the MPSO (Monocolumn Production Storage and Offloading System) - which is a floating unit based on a monocolumn with a moonpool. The development of the MPSO concept was focused on reducing the motions, keeping storage capability and allowing the use of rigid risers. Furthermore, recent studies have pointed towards the possibility of using dry tree completion system in MPSO. Considering this scenario, the MPSO concept evolution in which the hull forms and hydrodynamic appendages were developed, always aiming at motions mitigation, is presented herein. Initially, the MPSO was proposed to operate in the Campos Basin (Brazil) and, after new design considerations, it is being adopted to operate in the Gulf of Mexico (USA) at a no pipeline area. Thus, the MPSO solution proved to be versatile enough to be adapted to any location, including the pre-salt in Brazil.

The offshore exploration of gas requires the use of new platforms design called FLNG (Floating Liquefied Natural Gas). Nowadays just a few number of FLNG are in advanced stages of design or under construction. This type of vessel requires large tanks to storage the liquefied gas and in some cases the movement of the liquid inside the tanks can modify the vessel behavior in waves. The work objective is to obtain the influence of liquid cargo in the floating vessels motions. An experimental setup was proposed to investigate this influence. A FLNG model was tested for two configurations: with fixed dry cargo and with liquid cargo. For the latter, the model was equipped with tanks which were filled with water in three different levels. In total six different tests were carried out in the Hydrodynamic Calibrator from University of Sao Paulo, a tank with 14 m long, 14 m wide and 4 m depth equipped with 144 flaps capable of generating waves with different angles of incidence. The vessel motion was obtained for the six degree of freedom using an optical system. Furthermore, numerical models were made in WAMIT for both configurations with and without free surface effect due the liquid inside tanks. Results presented significant differences in the RAO curves. Basically, amplification in surge and sway motions was observed and changes in the roll natural period were obtained, both due the presence of liquid cargo. Furthermore, some limitations were obtained for numerical model mainly in cases with tanks filled at low levels. In these cases, the viscous forces presented significant influence and some effects as breaking waves (sloshing) inside tanks were observed. Both breaking waves and viscous forces are not considered in WAMIT model, once it uses the potential linear wave theory. Discussions are concerned in the comparison of motions obtained for the two tested configurations and in the limitations and applications of numerical model.