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Collaborating Authors
ABSTRACT The initial separation of mixed oil/gas and water from risers is done by wash tanks inside FPSO/FLNG hull. As vessel size increases, larger size separators/wash-tanks and storage tanks are considered. The performance of separators/wash-tank is in general affected by vessel motions and the vessel motion itself is also influenced by multi-layer-liquid sloshing motions inside wash tanks. MPS (Moving Particle Simulation) method has shown that it is adequate in predicting violent sloshing pattern and the corresponding impact loading on tank walls in case of single-phase-liquid problems. However, the application of the MPS method to multi-layer-liquid system has been very rare in the open literature. In the case of multi-phase-fluid system, a proper buoyancy model including surface tension has to be included to more accurately simulate the behavior among different-density particle members. Another important factor of multi-phase-liquid problem is a reasonable treatment of tracing multiple interfaces and imposing proper kinematic and dynamic boundary conditions at the interfaces. The newly developed MPS method for multiple liquid layers is validated through comparisons against linear potential theory (in the case when interfacial amplitudes are small) and some available experimental results. The multi-phase-liquid MPS sloshing program is also coupled in time domain with a ship-motion program to assess their interactions in a typical operational sea environment. The generation of interfacial sloshing waves depending on excitation wave period is clearly demonstrated and the internal waves are in several cases much greater than free-surface waves. Since various interfacial sloshing motions of different frequencies can be generated at the respective interfaces, the influence of large separators on vessel motion can be more complicated than the single-liquid tank.
- Europe (0.68)
- North America > United States (0.28)
The initial separation of mixed oil/gas and water from risers is done by wash tanks inside the FPSO/FLNG hull. As the vessel size increases, larger-sized separators/wash tanks and storage tanks are considered. The performance of separators/wash tanks is in general affected by the vessel motions, and the vessel motions themselves are influenced by multi-layer-liquid sloshing motions inside the wash tanks. The MPS (Moving Particle Simulation) method has shown that it is adequate in predicting violent sloshing patterns and the corresponding impact loading on tank walls in single-phase-liquid problems. However, the application of the MPS method to the multi-layer-liquid system has been very rare in the open literature. In the multi-liquid system, a proper buoyancy model including surface tension has to be incorporated to more accurately simulate the behavior among different-density particle members. Another important factor of the multi-liquid problem is the reasonable treatment for tracing multiple interfaces and imposing proper kinematic and dynamic boundary conditions at the interfaces. The newly developed MPS method for multiple-liquid layers is validated by comparison against linear potential theory (in the case when interfacial amplitudes are small) and by comparison against some available experimental results. The multi-liquid MPS sloshing program is also coupled in time domain with a ship-motion program to assess their interactions in a typical operational sea environment. The generation of interfacial sloshing waves depending on the excitation wave period is clearly demonstrated, and the internal waves are in several cases much greater than the free-surface waves. Since various interfacial sloshing motions of different frequencies can be generated at the respective interfaces, the influence of large separators on vessel motion can be more complicated than the single-liquid tank.
- Europe (0.68)
- North America > United States (0.46)
Abstract The two-layer sloshing of water and diesel oil is studied numerically by using the Consistent Particle Method (CPM). CPM solves the Navier- Stokes Equations through the two-step projection scheme. Compared to other projection-based particle methods, the distinct feature of CPM lies in its consistency and high-order accuracy in computing the spatial derivatives. By studying an experimental benchmark case, the capability of CPM in modelling large-amplitude two-layer sloshing and reproducing a clear fluid interface is demonstrated. Using the validated model, the two-layer sloshing under sway-only and coupled sway-heave excitations are studied. For the coupled excitation case, it is found that the sum or difference of the sway and heave frequencies being close to the odd multiple of the system's natural frequency induce secondary violent sloshing waves even both excitations are further away from the natural frequency. INTRODUCTION With the global shortage of resources, the demand for liquefied natural gas (LNG) keeps growing and by 2035 the gas is projected to supply the largest share of energy demand growth and over 40% of growing demand (Shell 2019). Compared to the traditional LNG system, the FLNG (floating liquefied natural gas) facility integrates the production, storage, processing, and transportation, and hence saves the gross cost. Therefore, the FLNG is getting more market share in the LNG industry. The integrated capability of FLNG in production and storage also implies that the filling level in an FLNG tank can vary from very shallow to very high. Previous studies on sloshing have suggested that the wave impact pressures and loads induced by middle-filling sloshing can be very violent (Luo et al. 2020), which may cause local damages to tank structure (Wang 2010) or global instability to the ship (Luo et al. 2016). For the safe design of FLNG vessels, therefore, the sloshing waves in FLNG tanks especially the resonant scenarios in middle filling levels need to be thoroughly investigated.
Abstract SDPSO platform is a deep-draft floating platform integrating the key functions of drilling, dry-tree production, oil storage and offloading capabilities, and improves the flexibility of technical solution and reduces the overall cost of deepwater oil field development. However, the motion of SDPSO platform induced by ocean waves may result in sloshing effect at the oil-water interface and cause mix of the two fluids, i.e. oil-water emulsification, which may cause the oil content in the displaced water to exceed international standard. Therefore, in the present study, the oil-water interface sloshing phenomena in the SDPSO's storage tank is investigated by means of ANSYS Fluent 14.0. The RANS κ- ε model and the VOF method are adopted to model the turbulence effect and track the free surface, respectively. The numerical results analyzed include mix of oil and water and the vertical displacement at the interface of two liquids. From this study, it is found that the motion of SDPSO platform will not result in obvious sloshing effect at the oil-water interface and mix of the two fluids.
- North America > United States (0.46)
- Asia > China (0.29)
ABSTRACT A liquid sloshing experimental system driven by a wave-maker is developed in the State Key Laboratory of Hydraulics and Mountain River Engineering at Sichuan University of China to study the sloshing of a two-liquid system with free surface in a rectangular tank. The chosen immiscible fluids are fresh water and 0# diesel oil from bottom to top in the tank. A series of laboratory experiments are conducted in the experimental rig to estimate the pressure distribution on the tank walls and the interfacial wave displacement by changing external excitation frequency of the shaking table. Comparisons are also presented with results from an in-house CFD code with improved volume of fluid (IVOF) tracking of the interface and free surface. Very good agreements are also obtained in the comparison.