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Numerical Simulation of Liquid Motion In SPB Tank
Kobayakawa, Hiroaki (Structural Engineering, Ship & Offshore Basic Design Department, IHI Marine United Inc) | Kusumoto, Hiroki (Structural Engineering, Ship & Offshore Basic Design Department, IHI Marine United Inc) | Toyoda, Masanobu (Structural Engineering, Ship & Offshore Basic Design Department, IHI Marine United Inc)
ABSTRACT: SPB tank is one of LNG tank types and it can avoid the resonance between internal liquid motion and ship motion by arranging internal structure. This paper describes validation study of simulation method for liquid motion analysis in SPB tank, sloshing experiment with large scale SPB tank model and numerical simulation of liquid motion in full-scale SPB tank. Through these studies, sloshing pressure in nonresonance condition is compared with that in resonance condition. These studies show that sloshing pressure is quite low level and simple CFD calculation can simulate it with sufficient accuracy in nonresonance condition. On the other hand, sloshing pressure is quite high level and it seems to be difficult to estimate it in resonance condition by simple CFD calculation. INTRODUCTION Many offshore gas fields are being discovered and developed due to increasing demand for clean and safe energy. Offshore gas storage systems have any level of partial filling conditions, which is generally severe in terms of sloshing. In fact, some incidents of damage to LNG tanks, such as Polar Alaska (1969), Arctic Tokyo (1971), Larbi Ben M'Hidi (1978), Catalunya Spirit (2006) and 3 Mark III ships (2008), was reported (Gavory et al., 2009). It was also reported that the damages were caused due to sloshing load and LNG filling height in tank played major role in sloshing intensity. Damage to LNG tank may cause wide-scale disaster and it should be averted. Furthermore recent large scale natural and man-made disasters brought the demands for preparation against unexpected situations and enhanced safety level to infrastructure industries. Therefore LNG tanks with non-resonance, the intrinsically safe containment systems, are desired. SPB tank system, developed by IHI (Fujitani et al., 1984), is one of LNG tank types and SPB means Self-supporting Prismatic Shape IMO type B.
- Asia > Japan > Kantō > Tokyo Metropolis Prefecture > Tokyo (0.25)
- North America > United States > Alaska (0.24)
- Research Report > New Finding (0.87)
- Research Report > Experimental Study (0.55)
Improved Structural Redundancy of Hull Structure In Collision By Applying Steel Plates With High Uniform Elongation
Hirota, Kazuhiro (Nagasaki Ship & Ocean Department, Mitsubishi Heavy Industries) | Nakayama, Shin (Structure Laboratory Technical Headquarters, Mitsubishi Heavy Industries) | Okafuji, Takashi (Structure Laboratory Technical Headquarters, Mitsubishi Heavy Industries) | Nakashima, Koichi (Steel Research Laboratory, JFE Steel Corporation) | Hase, Kazukuni (Steel Research Laboratory, JFE Steel Corporation) | Shiomi, Hiroshi (Plate Business Planning Department, JFE Steel Corporation) | Tsuyama, Seishi (Steel Research Laboratory, JFE Steel Corporation)
ABSTRACT: To improve structural redundancy of hull structure in accidental condition such as collision or grounding, and to prevent environmental loading, applying steel plates with high deformability for hull structure is considered to be effective, due to the increased absorbed energy before fracture. Steel plates with excellent uniform elongation† have been developed through the advanced thermo mechanical control process (TMCP). In order to improve uniform elongation, it is important to control the microstructure, consisting of the large volume fraction of ferrite, which has high capacity for work hardening, and the hard second phase, such as bainite. To accomplish the microstructural control, two-step accelerated cooling process was adopted after hot rolling in an actual plate mill. The obtained 20mm-thick YP355 grade steel plate showed excellent uniform elongation of 18 % with about 1.3 times larger than the conventional TMCP one. Numerical simulation was carried out to estimate damage reduction in collision in the case of using the developed plates for side shell of LNGC (Liquid Natural Gas Carrier). The calculation results indicated marked effect to reduce damage of hull structure in collision by applying the developed steel to side skin. INTRODUCTION To improve ship safety, and to prevent environmental loading in accidental collision or grounding, applying steel plates with high deformability for hull structure is considered to be effective, due to the increased absorbed energy before fracture. Many studies have been reported on microstructural control of steel to improve deformability. The dual phase structure, consisting of large volume fraction of ferrite, which has high capacity for work hardening, and hard second phase, such as bainite or martensite, is effective to improve deformability (Bucher et. al, 1979; Furukawa, 1980; Takahashi et. al., 1980, Kunishige, 2001; Oliver et. al., 2007).
- Materials > Metals & Mining > Steel (1.00)
- Energy > Oil & Gas (1.00)
Influence of Phase Transition On Sloshing Impact Pressures Described By a Generalized Bagnold¿s Model
Ancellin, Matthieu (Centre de Mathématiques et de Leurs Applications, Ecole Normale Supérieure de Cachan and CNRS) | Ghidaglia, Jean-Michel (Centre de Mathématiques et de Leurs Applications, Ecole Normale Supérieure de Cachan and CNRS) | Brosset, Laurent (GTT (Gaztransport & Technigaz))
ABSTRACT: The effect of phase transition during liquid impacts involving entrapped gas pockets might play an important role for fluids close to thermodynamic equilibrium as LNG/NG in tanks of LNG carriers. However, this role is disregarded during Sloshing Model Tests. This issue was addressed in Braeunig et al. (2010) by introducing a simple 1D piston model. The phase transition between the liquid and its vapor was described through a simple quasi-static relaxation model including thermal exchanges at the wall. A more advanced version of this 1D model is presented. A thermodynamic description of the relaxation process from unbalanced conditions to the liquid/vapor equilibrium is proposed. The new model conserves the total energy of the liquid-vapor system. It generalizes the classical Bagnold's model (1939) and can be formulated in dimensionless form exhibiting not only the usual Impact number (Bagnold) and numbers related to thermo-dynamic properties of the fluid (thermal capacities, latent heat), but also characteristic times for respectively mass transfer and energy transfer. The model shows that, as observed experimentally (sloshing model tests with water and steam described by Maillard et al., 2009), phase transition mitigates pressure impacts involving entrapped gas and damps drastically the oscillations of the gas pockets. The amplitudes of mitigation and of damping depend on the fluid properties. INTRODUCTION Context Today, sloshing model tests, most of the time at scale 1:40, are considered as the only relevant tool for any sloshing assessment of a real project of LNG carrier (see Gervaise et al., 2009). The model tank motions are imposed by a six degree-of-freedom rig after down-scaling full scale calculated ship motions. The motion down-scaling is obtained by applying a coefficient 1/λ (geometrical scale) on the amplitudes and a coefficient 1/√λ on the times, namely by keeping Froude number the same at both scales.
ABSTRACT: MarkIII is one of the containment systems designed by GTT for LNG storage or transportation. It features a corrugated stainless steel membrane which modifies locally the flow of LNG in the tanks of LNG carriers, hence modifies the loads during sloshing impacts. The interactions between breaking waves and the MarkIII corrugated membrane were described in Bogaert, Brosset and Kaminski (2010). The observations were based on the large scale impact tests of the Sloshel project performed in 2009. In this paper, these interactions are described again but based this time on the Sloshel full scale impact tests performed in 2010. In both test campaigns, unidirectional breaking waves were generated in flume tanks in order to break onto instrumented walls. Full scale tests were performed with a water height at rest of 4 m and the wall was covered by the real MarkIII membrane. Special sensors were designed to measure the forces on corrugations. The wave-corrugation interactions were captured by high speed cameras synchronized with the data acquisition system. Qualitatively, the interactions observed at full scale are very similar to those observed at scale 1:6. However, full scale measurements allow a more in depth analysis of the local phenomena involved. The paper shows that the different kinds of interactions between breaking waves and either a flat or a corrugated wall induce loads that are combinations of only a few Elementary Loading Processes (ELPs):direct impact, building jet along the wall from the impact area and compression/expansion of entrapped or escaping gas. In case of a corrugated wall, additional combinations of ELPs occur because new local flow situations intervene. However, these are still combinations of the same ELPs. Therefore, the ELPs are considered as the building blocks of any load on a wall impacted by a wave.
- Europe (1.00)
- North America > United States (0.28)
ABSTRACT: Model tests are widely used for the analysis of cargo sloshing in LNG tankers, and for design purposes. The complexity of the phenomena involved in LNG cargo sloshing impedes the application of simple scaling laws, and the transposition of model tests results to full scale remains an important issue. A solution to enhance the representativeness of model tests is to refer to full scale measurements of sloshing. A first significant series of such measurements has recently been performed, followed by a model tests campaign reproducing the conditions corresponding to the full scale sloshing measurements. INTRODUCTION A Joint Industry Project with BW Gas, Teekay, DSME, Lloyd's Register, DNV, Light Structures and GTT, dedicated to the Full Scale Measurement of sloshing, is currently providing an unprecedented insight into cargo sloshing in the tanks of LNG tankers. This first significant attempt to detect and measure sloshing impacts at full scale in operational conditions has been producing more than two years' worth of measurement data, thanks to the instrumentation installed in tank n°2 of a 148 000 m3 LNG Carrier, the LNG IMO, built by DSME and owned by BW Gas. Sloshing impacts are recorded at high fills, in the two forward corners of the tank ceiling. Within the JIP, GTT has performed a first model tests campaign reproducing the conditions of the full scale sloshing measurements. The ship motions recorded on board the LNG IMO for a selection of voyages have been used as an input for the tests. The preparation of the model tests, the test rig and the test plan are described, and results from the model test are provided and commented, with emphasis on the comparison with the full scale measurement results. Finally, the questions and challenges raised by the full scale / model scale analysis are briefly discussed.
- Energy > Oil & Gas > Midstream (1.00)
- Transportation > Freight & Logistics Services > Shipping > Tanker (0.74)
ABSTRACT: After years of efforts (Deuff, 2007, Oger et al., 2009; Guilcher et al., 2010), HydrOcean and Ecole Centrale Nantes, supported by GTT, succeeded in the development of a SPH software gathering all functionalities for relevant simulations of sloshing impacts on membrane containment systems for LNG carriers. Based on Riemann solvers, SPH-Flow deals with two compressible fluids (liquid and gas) that interact with the impacted structure through a complete coupling. The liquid, the gas and the structure are modelled by different kinds of dedicated particles allowing sharp interfaces. An efficient parallelisation scheme enables to perform calculations with a sufficiently high density of particles to capture adequately the sharp impact pressure pulses. The development of the bi-fluid version led in a first stage to unstable solutions in the gaseous phase for pressures below the ullage pressure. This difficulty was presented in ISOPE 2010 (see Guilcher et al., 2010) and has been overcome since. Simulations of a unidirectional breaking wave impacting a rigid wall after propagating along a flume are presented in this paper. The physical phenomena involved in the last stage of the impacts are scrutinized and compared with experimental results from Sloshel project (see Lafeber et al., 2012b). A comparison between calculated results at full scale and at scale 1:6 is proposed. Conclusions about scaling in the context of wave impacts are given. INTRODUCTION Context For the time being, GTT developed a know-how based on the feedback from the LNG carrier fleet in order to derive appropriate statistical scaling factors. Elementary Loading Processes (ELP) Scaling impact pressures from sloshing model tests to the full scale of an LNG carrier implies being able to decompose all the loading components for any liquid impact on the walls and evaluate their relative importance at both scales.
Apply MPS Method to Simulate Liquid Sloshing In LNG Tank
Zhang, Yuxin (State Key Laboratory of Ocean Engineering, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University) | Wan, Decheng (State Key Laboratory of Ocean Engineering, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University)
ABSTRACT: In the present study, liquid sloshing in a 2D membrane-type LNG tank is simulated based on Moving Particle Semi-Implicit (MPS) method, which is a meshless method. However, the traditional MPS method suffers from strong unphysical pressure oscillation. To overcome this, the present MPS employs some improvements, such as: nonsingular kernel function, mixed source term for pressure Poisson equation (PPE) and an accurate surface detection method. Smooth pressure field is obtained based on the present MPS method. The tank is forced to move at various modes: sway and roll motion. The effects of excitation period and amplitude on the flow are investigated. It is shown that the impact behavior is significantly affected by excitation period and amplitude. When excitation period is near resonance period, resonance phenomenon is observed. The flow is violent and a periodic impact behavior shows two large pressure peaks in each period. A case by combining the horizontal, vertical and roll motions is simulated. The predicted pressure on the wall of the LNG tank by MPS method shows a good agreement with experimental data and other numerical results. The impact behavior induced by liquid sloshing is accurately numerically predicted. In addition, violent free surfaces are observed. INTRODUCTION Sloshing is a kind of fluid motion in partially filled tank. It is of great importance in design of ships that carry liquid cargo, such as LNG(Liquefied Natural Gas) ship, since the impact load induced by liquid sloshing may cause large damage on the tank and affect the safety of ship. So there is a strong need to predict the impact loads on the structure in design of LNG ship. Sloshing flow is a highly nonlinear problem, which may involve complicated phenomena, such as breaking wave, high-speed impact on tank wall and overturning of free surface.
Repeatability And Two-Dimensionality of Model Scale Sloshing Impacts
Souto-Iglesias, A. (Naval Architecture Department (ETSIN), Technical University of Madrid (UPM)) | Botia-Vera, E. (Naval Architecture Department (ETSIN), Technical University of Madrid (UPM)) | Bulian, G. (Department of Mechanical Engineering and Naval Architecture, University of Trieste)
ABSTRACT: Canonical test cases for sloshing wave impact problems are presented and discussed. In these cases the experimental setup has been simplified seeking the highest feasible repeatability; a rect- angular tank subjected to harmonic roll motion has been the tested configuration. Both lateral and roof impacts have been studied, since both cases are relevant in sloshing assessment and show specific dynamics. An analysis of the impact pressure of the first four impact events is provided in all cases. It has been found that not in all cases a Gaussian fitting of each individual peak is feasible. The tests have been conducted with both water and oil in order to obtain high and moderate Reynolds number data; the latter may be useful as simpler test cases to assess the capabilities of CFD codes in simulating sloshing impacts. The repeatability of impact pressure values increases dramatically when using oil. In addition, a study of the two-dimensionality of the problem using a tank configuration that can be adjusted to 4 different thicknesses has been carried out. Though the kinematics of the free surface does not change significantly in some of the cases, the impact pressure values of the first impact events changes substantially from the small to the large aspect ratios thus meaning that attention has to be paid to this issue when reference data is used for validation of 2D and 3D CFD codes. INTRODUCTION The state of the art sloshing assessment procedures for LNG vessels and floating production and storage units are based on risk assessment techniques (DNV, 2006; LRS, 2009; Gervaise et al., 2009; Kuo et al., 2009; Diebold, 2010). Due to the extra costs that derive from these campaigns, a mid-term goal of designers is to characterize the sloshing loads using CFD technologies.
Improvement Method On Offloading Operability of Side-by-side Moored FLNG
Kim, M.S. (Offshore Technology Research, Marine Research Institute, Samsung Heavy Industries Co. Ltd.) | Jeong, H.S. (Offshore Technology Research, Marine Research Institute, Samsung Heavy Industries Co. Ltd.) | Kwak, H.W. (Offshore Technology Research, Marine Research Institute, Samsung Heavy Industries Co. Ltd.) | Kim, B.W. (Offshore Technology Research, Marine Research Institute, Samsung Heavy Industries Co. Ltd.) | Eom, J.K. (Offshore Technology Research, Marine Research Institute, Samsung Heavy Industries Co. Ltd.)
ABSTRACT In the Floating LNG (FLNG) development, STS (Ship-to-ship) offloading operation is considered to transfer LNG cargo into shuttle LNG carrier through loading arm system with side-by-side mooring arrangement. For the safe operation of loading arm, the good offloading operability regarding operation envelop is one of key factors in FLNG development. The operational envelop of loading arm is functions of relative motion and wave drift force between two vessels. Also, the STS offloading operability is affected by the side-by-side mooring configuration. To ensure safe loading arm operation, the relative motion reduction methodology or device, and optimization of side-by-side mooring arrangement are required. Based on the relative motion reduction concept, we performed model test for the relative motion at loading arm point in two environment conditions. The experimental results show the present reduction concepts can be used effectively to ensure safe loading arm operation. INTRODUCTION As the demand of natural gas is increasing, a LNG-related offshore plant such as FLNG and FSRU (Floating Storage and Re-Gasification Unit) is receiving much attention these days. In general, many offshore operations involve the use of two or more floating structures, which are positioned closely to transfer oil or gas during offloading operation. In case of the LNG-related offshore plant, a side-by-side offloading system with loading arm is applied instead of a typical tandem offloading system. The side-by-side moored vessels show different characteristics from the tandem moored vessels. Hydrodynamic interaction between the vessels is highly increased and it gives an effect on relative motion and drift forces due to their close proximity (Kim and Ha, 2002, 2003, Ha and Kim, 2004). The shielding effect on current and wind load is another important consideration (Yuck et al. 2007). Recently, for more accurate results, the time-domain approach using Rankine panel method is applied to the multiple-body problem (Kim at al, 2009).
- Research Report > New Finding (0.34)
- Research Report > Experimental Study (0.34)
- Energy > Oil & Gas > Midstream (1.00)
- Transportation > Freight & Logistics Services > Shipping > Tanker (0.74)
The Study On Natural Gas Liquefaction Cycle Development For LNG-FPSO
Lee, Sanggyu (R&D Division, KOGAS (Korea Gas Corporation)) | Choe, Kunhyung (R&D Division, KOGAS (Korea Gas Corporation)) | Lee, Chulgu (R&D Division, KOGAS (Korea Gas Corporation)) | Yang, Young-myung (R&D Division, KOGAS (Korea Gas Corporation))
ABSTRACT With worldwide LNG demand increasing rapidly, LNG liquefaction plants and liquefaction processes are higher value-added industries. Recently, there has been an increase in research and development of LNG-FPSO technologies in offshore liquefied natural gas (LNG) service instead of land-based LNG plants. While onshore LNG facilities have traditionally focused on power efficiency as a key criterion for process design and equipment selection, offshore LNG would require not only power efficiency but also safety and compactness. A new natural gas liquefaction cycle is proposed in this paper. The structure of the new cycle is based on the SMR (Single Mixed Refrigerant) liquefaction cycle which has a very simple structure. The proposed liquefaction cycle has liquid-vapor separator to separate MR into HK (Heavy Key) and LK (Light Key) components, and each key is compressed separately after the main cryogenic heat exchanger, and then mixed again to make a single MR. The proposed cycle can be optimized using the temperature profiles in cryogenic heat exchanger and compressor power using each separated compressor. The proposed liquefaction cycle has a simple structure with high compactness and power efficiency, therefore the proposed cycle could be suitable for the LNG-FPSO liquefaction process. INTRODUCTION Thermodynamic process for the liquefaction of natural gas has evolved since 1970's (Barron, 1985; Roberts, 2002; Andress, 2004; Flynn, 2005; Venkatarathnam, 2008; Chang, 2009, Lee, 2010) in order to meet a number of challenges, including the demand of greater efficiency and larger capacity. A liquefaction system is primarily composed of a series of compressors, coolers, expanders, and heat exchangers. Natural gas is cooled-down to LNG temperature in thermal contact with closed-cycle refrigerant(s). In order to reduce the input power for liquefaction, it is crucial to reduce entropy generation due to the temperature difference between hot stream (including feed gas and hot refrigerants) and cold refrigerants in the heat exchangers.