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Abstract ACRIPREVISUB is a novel project for forecasting wave–induced flood hazards, such as wave runup and overtopping, that occur along coastal areas. The main scope of our project is the real time evaluation of emergency situations and the issue of warnings to the relevant coastal or port authorities and stake holders. Within the context of this study, we numerically investigated the propagation of directionally—spread short and infragravity waves towards the shore to predict runup heights and overtopping motions on structures and beaches. This novel methodology was applied in the coastal zone of Alpes Maritimes in France and was tested against laboratory experimental data. INTRODUCTION Coastal environment is a significant geographical area, since it gathers a wide range of human social activities. This complex system of natural variables is especially fragile and exposed to multiple risks, including flooding, shoreline erosion and infrastructural damages due to extreme hydro–meteorological events: storm surges, heavy precipitation and tides (Plomaritis et al., 2018; Mori et al., 2019). Coastal flooding phenomena are among the most damaging natural disasters affecting urban zones adjacent to the shorelines. Extreme coastal water levels may lead to considerable impacts in densely populated low–lying coastal areas, while anthropogenic unplanned infrastructures and poor governance are additional factors that increase flood risk. Flood hazard is rarely a function of one process alone but comprises multiple drivers, including energetic waves, extreme coastal water levels, heavy precipitation, and high river discharge (Ganguli and Merz, 2019). Monitoring of two key mechanisms, wave overtopping and run–up, is necessary to estimate the results of coastal flooding, therefore significant efforts have been undertaken in recent years into their predicting (Tsoukala et al., 2016; Xie et al., 2019; Beer et al., 2021) The accurate prediction of wave runup (the maximum vertical extent of wave uprush on the beach), as well as its components, time–averaged setup and the time–varying swash, is an important element of coastal storm hazard assessments, as runup height controls the potential for flooding by wave overtopping. Moreover, the oscillatory component of runup (swash) transfers energy from the waves to the shore, playing a dominant role in nearshore sediment transport and morphology, as it can drive significant erosion during storms. In addition, in order to meet design requirements for the construction of seawalls and dikes the evaluation of wave overtopping phenomena is of high engineering interest.
ABSTRACT Tests are performed in the 17 m long wave tank of Ecole Centrale Marseille (ECM) in order to measure the loads induced by non-impacting waves on a vertical piercing cylinder. Different configurations of the cylinder (shape and size of the section and length) are studied for two focusing waves. Wave loads as calculated by Morison equation are compared to measurements. The context is the assessment of the hydrodynamic loads due to sloshing on the pump tower in LNG tanks on floating structures. The comparisons turn out to be good in all cases studied provided Morison equation is used with relevant time series of liquid velocities and accelerations. INTRODUCTION Context Liquefied natural gas (LNG) membrane tanks are largely used on different kinds of floating structures such as LNG carriers, floating liquefied natural gas vessels (FLNG), floating storage regasification units (FSRU), LNG fueled ships (LFS), LNG bunker vessels (LBV) and all small scale related applications. In these tanks, the liquefied gas remains in conditions close to thermodynamic equilibrium (-162°C @ atmospheric pressure). Depending on the application, the volume of LNG tanks for floating structures ranges from a few thousand cubic meters for LFS or small scale applications to about 55 000 m for tanks of the largest LNG carriers. Whatever the application, the shapes of these tanks are always prismatic with large upper chamfers and smaller lower chamfers. The tanks do not include any structure that could mitigate LNG sloshing except a pump tower. The pump tower (Fig. 1) is a tubular vertical stainless steel structure that enables loading and unloading LNG, thanks to pumps located at its base. It is mainly made of three large vertical pipes, the emergency pipe at the front and two discharge pipes at the rear, connected together by struts. Located at the rear of the tank, in the central part but not necessarily exactly in the middle, it hangs from the liquid dome and is horizontally guided at its base by the pump tower base support (PTBS).
Abstract As part of the Monaco offshore extension project, is in charge of design & build a maritime infrastructure as the first step of the six-hectare expansion of the city into the sea. This maritime infrastructure consists of a fill enclosed by a band of 18 trapezoid reinforced concrete caissons and will serve as base for construction of the new eco-neighborhood in Monaco. The caisson precasting area is located in the port of Marseilles, using a dedicated floating dock. The paper focuses on some of the problems which had to be solved, among which : The optimization of promenade level, searching for : ○a compromise between architectural point of view and safety related to storm wave overtopping, taking into account sea level rise and correlations between extreme waves and water levels; ○minimal reflection coefficient for vertical concrete caissons, so as to minimize impact on existing Port Hercules wave disturbance. Caissons and rubble mound foundation stability related to waves and seism, including extra seismic forces due to buildings considering the high reclamation height (up to 40 m) and the immediate proximity of building foundations. The presence of a small craft harbor, whose location was fixed for urbanistic reasons, which requested optimizations in detail of anti-overtopping devices as much as possible integrated in the urban context, including a low crested "swimming pool caisson breakwater" Design and build of a dedicated floating yard Design has required a multidisciplinary approach (urbanists, landscapers, architects, marine infrastructure engineering, biologists), with unconventional infrastructure solutions due to the very specific context (direct exposure to offshore waves, proximity of sensitive port and natural areas, seismic hazard associated with buildings very close to 25 m high concrete caissons …).
ABSTRACT Structural monitoring is increasingly becoming everyday business in the offshore industry. The monitoring may target the strain estimation or focus on tracking the changes in the dynamic properties of the structure in order to predict damages at remote / or possibly subsea locations. This paper will show that by monitoring the structural response, it is also possible to indirectly estimate the wave loading acting on the system. This information can be used to increase confidence in the load probability models for the structural design or aid the health monitoring procedure. During ambient vibration, the principles of operational modal analysis (OMA) are applied to harvest the dynamic properties of the structure. Successively, a dynamic model is formulated and used to calculate the loading from a random sea state using the response of the structure. A laboratory experiment is conducted in a wave flume at LASIF, Marseille, France, where a scaled offshore model is equipped with accelerometers to monitor the structural response during a random sea. The study shows that it is possible to use the structure as a dynamic load cell and monitor the loads occurring in actual conditions. Both the short time variations and the load spectra can be computed successfully using the structural response. INTRODUCTION In the field of offshore structures, an increase is seen in the subject of monitoring. Recently, TOTAL announced that as for the redevelopment of the Tyra field, the platform Tyra East will be equipped with no less than 100000 sensors (Beck, 2018). Most of these will, of course, target the production processes, but the monitoring scope will also include the structural performance. The aim of structural monitoring may be plentiful, for instance with regards to operational limitations such as heading, static deformation or vibration level. The vibration pattern can be used for health diagnostics, and since offshore structures are prone to fatigue damages, monitoring their well-being is essential for ensuring safety and reliability.
Abstract During the last decade, wave impact tests in flume tanks have become an important tool to scrutinize single wave impacts in order to better understand sloshing physics in LNG floating tanks and the scaling issues related to the use of sloshing model tests to derive design loads for the membrane containment systems. Wave impact tests enabled to gain much knowledge on the physics of liquid impacts including the influence of the compressibility of ullage gas and the interaction between waves and the protuberances on the wall like the corrugations of MarkIII containment system. This knowledge is obviously applicable for LNG sloshing with low or partial fillings leading to transverse breaking waves hitting the vertical longitudinal walls of LNG tanks. Is it applicable for liquid impacts occurring on the top corners of these tanks for high fill conditions? Those kinds of impacts related to the developments of free surface modes may have different patterns and characteristics that have not been so much studied at a large enough scale yet. This paper relates an attempt carried out in the wave canal of Ecole Centrale Marseille (ECM), in the frame of a long-term collaboration with GTT, to generate wave impacts on a horizontal plate that could be considered as a ceiling. The main challenge is to generate relevant wave shapes before impact with a sufficient vertical velocity. The different solutions in terms of wave-maker excitations are presented together with the corresponding wave characteristics. Wave impact tests with the most relevant selected waves have been performed either with a flat ceiling or with a corrugated ceiling obtained by the addition of three solid corrugations representing the geometry of the large corrugations of MarkIII membrane at scale ½. The corrugations were screwed to the ceiling plate in the transverse direction with regard to the canal. The instrumentation included numerous pressures sensors, located on the ceiling but also directly on the corrugations, and a visualization system with two high speed cameras. Characteristic pressure fields at the ceiling are shown with both configurations of ceiling. This work is part of a more general R&D program of GTT on experimental and numerical studies of liquid impacts in order to better understand the physics of sloshing impacts within LNG tanks on floating structures
Abstract We propose a fast reliable model for simulating the interaction between an air-water flow and a floating structure. We have developed a model which solves the three dimensional compressible Euler equations under the assumption of low Mach number for bi-fluid flows on unstructured mesh. We focus our attention on a sharp description of the air-water interface with an interface-sharpening procedure. An improvement of this model is suggested here to treat fluid-structure interaction (FSI) problems by introducing a rigid body in air-water flows. A penalization method is used to ensure a rigidity constraint through a penalized velocity in order to get the correct motion of the rigid body. We choose to calculate this velocity relative to the dynamic of the flow by using a projection method. The position of the boundary of the solid is computed at each time step through a ray-casting algorithm. Investigations through numerical simulations of free-surface flows with floating body are then conducted in order to validate the robustness of our penalization procedure. Introduction Although CFD simulations have been continuously improved in the past decades with stable accurate numerical schemes, the interaction between a fluid and a structure remains a difficult problem to solve. A classical resolution involves a full Navier-Stokes model with finite-volume schemes for the fluid and a finite-element mechanical solver for the structure. The coupling is carried out through the boundaries conditions between the nodes shared in the fluid-structure interface or through an interpolation. This approach is called partitioned. It can benefit from various existing solvers in fluid and solid mechanics (Felippa et al, 2001) since these are independent and called successively. However, partitioned methods suffer from a costly desynchronisation between the fluid and solid solver since they compute their solution at a different time. The other approach to treat FSI problems consists in solving the equation for the solid and for the fluid simultaneously with a single formulation, it is the monolithic approach. Only one solver is used, the coupling is implicit but requires a programming effort. Monolithic schemes are unconditionally stable and allow a larger time step than partitioned schemes for an equivalent accuracy (Michler et al., 2004).
Arnaud, Gwendoline (Université de Toulon, Aix-Marseille université ACRI-IN) | Touboul, Julien (Université de Toulon, Aix-Marseille université) | Sous, Damien (Université de Toulon, Aix-Marseille université) | Gouaud, Fabrice (ACRI-IN) | Rey, Vincent (Université de Toulon, Aix-Marseille université)
Abstract This communication is related to the energy dissipation by porous media. A particular attention is paid on the effects of specific surface on dissipated energy through a porous media constituted by a compact network of emerging vertical cylinders. Experiments have been performed with three porous structures with varying cylinder diameters. The porosity is chosen constant whereas the specific surface depends on diameters of cylinders. Two series of experiments have been carried out, the first with stationary flows and the second with regular waves. Finally, scale effects on the reflection and transmission coefficients are also studied.
Henry, Alan (Aquamarine Power Ltd.) | Kimmoun, Olivier (Ecole Centrale Marseille) | Nicholson, Jonathan (Aquamarine Power Ltd.) | Dupont, Guillaume (Ecole Centrale Marseille) | Wei, Yanji (University College Dublin) | Dias, Frederic (University College Dublin)
Abstract This paper describes a series of experiments undertaken to investigate the slamming of an Oscillating Wave Surge Converter in extreme sea states. These two-dimensional experiments were undertaken in the Wave Flume at Ecole Centrale Marseille. Images from a high speed camera are used to identify the physics of the slamming process. A single pressure sensor is used to record the characteristic of the pressure. Finally numerical results are compared to the output from the experiments.
Jeanne, Pierre (Lawrence Berkeley National Laboratory) | Rinaldi, Antonio Pio (Lawrence Berkeley National Laboratory) | Rutqvist, Jonny (Lawrence Berkeley National Laboratory) | Cappa, Frédéric (Lawrence Berkeley National Laboratory) | Guglielmi, Yves (CEREGE (UMR7330))
Abstract: In this study, we have examined the influence of the fault zone characteristics on pressure diffusion and fault reactivation by CO2 injection. Especially, we studied the effect of lithological and rock physical properties on the fault zone response inside a multilayer sedimentary system. Through numerical analysis, we compared four models where the complexity of the fault zone internal architecture is considered. Results show how the presence of hydromechanical heterogeneity influences the pressure diffusion, as well as the effective normal and shear stress evolutions. The more complex the fault zone architecture is and the more heterogeneities that are present, the faster the pressurization within the damage zone occurs. But, these hydromechanical heterogeneities (i) strengthen the fault zone resulting in earthquake of smaller magnitude, and (ii) impede fluid migration along the fault. We also show that the effects of the hydromechanical heterogeneities within the reservoir are negligible relative to those between the caprock and the reservoir.
Abstract Water is an essential element in the upstream and downstream operations of oil and gas companies. Yet water, particularly fresh water, is already a scarce resource in many parts of world and further constraints are predicted. Continuing the development and implementation of water stewardship practices across the oil and gas lifecycle is therefore considered an important component in a company’s sustainability strategy. IPIECA, the global oil and gas industry association for environmental and social issues, has recently made significant strides in this arena to raise stakeholders and the industry’s awareness of water management issues. IPIECA has developed a water management framework which adopts the principles of water stewardship. Uptake and adoption of the framework should lead to recognition by internal and external stakeholders that the oil and gas inudsty is proactively and collectively managing the issues related to sustainable water use and acting as stewards of this valuable resource. The IPIECA water management framework outlines a series of industry guidelines, tools and initiatives providing a comprehensive approach through the full lifecycle of oil and gas development and production. The framework builds upon the systematic approach which is adopted by IPIECA to manage water risk – ‘global->local->guidance’ (SPE 157544). This approach includes the use of the IPIECA Global Water Tool for Oil and Gas and the Global Environmental Management Initiative (GEMI) Local Water Tool for Oil and Gas to help business better understand both the global and local level water risk from which specific guidance is then developed. The World Water Forum Target 2.3.6 which was identified at the 6 World Water Forum in Marseilles in 2012, to "drive responsible water management in oil & gas exploration and production" is aligned with the IPIECA Water Management Framework. Work on this target is being led by IPIECA with support from the International Association of Oil and Gas Producers (OGP). The development of the IPIECA framework should support and improve the sector’s water management practices and approaches.