The critical incidents of the brash ice accumulation are considered using the port of Sabetta as an example. The heat volume, required for the keeping the certain thickness of the brash ice layer is determined using a thermodynamic simulation. The simulation results determine the power capacity of the required heat producing generator. The various methods, that can be used to reduce the energy consumption costs are described, such as: scheduling of the vessels traffic, change of the vessel movement scheme, optimization of the location of the bubbling lines and discharge points of the heated water. INTRODUCTION Currently, active development of the Arctic coast of Russia is under way. Mining companies developed the vigorous activities for development of oil, gas, gas-condensate and other fields. A maritime transport plays an important role in these works. It delivers consumables, machinery and ready-made structures to the Arctic to build the infrastructure. The developed fields begin to supply the raw materials (hydrocarbons and other) to markets by sea. The largest economic activity is observed in the Ob-Yenisei region. It includes the construction of ports and other hydraulic facilities. The port of Dudinka has long operated on the Yenisei River. It provides a transportation of finished products from Norilsk mining and metallurgical plant. The port of Sabetta and the terminal "Arctic Gate" in the Ob' bay had already built for LNG and oil offloading. The design and construction of other facilities, mainly in the northern part of the Ob' bay, continues. The "Utrennyi" terminal is being built on the Gydan Peninsula and it is part of the port of Sabetta. The LNG carrier vessels will be loaded with liquefied natural gas at this terminal. The development of the region is causing a transfer from seasonal sea transportations to year-round traffic. In the Yenisei Gulf, a regular winter sea navigation from the port of Dudinka is carried out since 2008. In the Ob'Bay, a regular winter navigation is carried out from the port of Sabetta since 2013 and from the oil terminal "Arctic Gate" near Kamennyi Cape since 2015. During this time, a sea traffic, for example, in Sabetta, has grown from single calls to several hundred vessels per season.

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 3 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).

In this research, the investigation on simulation of sloshing pressure based on SPH is mainly demonstrated. Two different boundary conditions, dynamic boundary conditions (DBC) and dummy particle conditions (DPC), are utilized in the SPH models. The benchmark test with respect to the traditional 2D rectangular tank is firstly conducted. Then, simulations based on two boundary conditions are performed for 3D spherical shape MOSS-Type tank. The corresponding model tests are carried out to verify the performance of numerical simulation. Smoothed boundary model (SBM) is used to better illustrate the 3D spherical shape and the predicted pressure based on DBC and DPC can be enhanced by SBM. Finally, the influence of particle shift algorithm on the prediction of surface pressure is discussed. INTRODUCTION With the increasing demand of Liquid Natural Gas (LNG) and growing LNG exportation from the United States, Australia and other countries, how to qualitatively and quantitatively evaluate the in-tank LNG sloshing influence on the LNG ship motion and structural strength is always a challenging concern. Conventional scale model test is the most straightforward approach to study the sloshing behavior. However, performing model test usually involves huge budget and large amount of time and scale effect can not be considered as well. To overcome the shortage of model test, as an alternative solution, Computational Fluid Dynamics (CFD) has been successfully utilized in sloshing research in recent decades. Many studies have demonstrated the accuracy of the Eulerian grid-based fluid model for sloshing simulations. Kishev et al. (2006) successfully used the constraint interpolation profile method to tackle the 2D violent sloshing problem. The popular finite volume method (FVM) solver OpenFOAM has been widely used to investigate sloshing behavior (Li et al., 2011; Moirod et al., 2010; Jiang et al., 2015). Lee et al. (2007) used the commercial FVM solver FLOW-3D to examine the parametric sensitivity of the sloshing force in liquefied natural gas (LNG). In the above FVM models, establishing how to obtain the free surface is usually the crucial problem. Although this problem can be solved by volume-of-fluid (VOF) theory or level-set (LS) theory, new problems may be introduced as VOF is essentially a step function, and the law of mass conservation is usually violated in LS models. Furthermore, numerically capturing the fluid surface and updating the fluid mesh make the numerical model more complex and more time consuming.

Experimental results of sloshing model test have been investigated by data mining in the database of Seoul National University. More than 540 terabytes experimental data have been accumulated for various cargo holds, vessels, environmental conditions, operational conditions, and experimental conditions. The database was organized, cleaned, and analyzed. Model tests related to the floating units larger than standard size LNG carriers or LNG fueled vessels were selected. Then, the selected target data had been used for the artificial neural network to predict the model test results from the test conditions. The network successfully predicted the experimental results considering the various parameters. INTRODUCTION Vessels carry many different liquids such as Liquefied Natural Gas (LNG), petroleum, and sea water in cargo tanks. When a vessel sails under the environmental loads, sloshing occurs in a tank containing partially filled liquid, which can cause serious damage to the structure. Therefore, when designing a ship, it is necessary to accurately estimate the sloshing loads (Faltinsen and Timokha, 2009; Malenica et al., 2017). Recently, many studies have been conducted to estimate sloshing load. One reason is the increase in LNG volume and the rapid expansion of the LNG carrier construction market (BP, 2018; Kuo et al., 2009). LNG carriers have been enlarged for efficient transport. Since larger sloshing impact loads may occur in larger cargo holds, studies have been actively conducted to estimate them. With the expansion of the LNG carrier market, LNG fueled vessels have recently become one of the main products in the shipbuilding market (Congressional Research Service, 2019). Environmental regulations for ship operations have been tightened and LNG has begun to be used as a propulsion fuel for the vessels. Fuel tanks used in the LNG fueled vessels have a different shape from the cargo holds; therefore, partial loading conditions must be considered unlike the LNG carriers.

The present study investigates the resonant fluid flow within horizontal axisymmetric tanks under forced harmonic translation in the transversal direction. Experiments and numerical simulations with the MPS method were carried out for a reduced-scale model with a 2:1 aspect ratio and semi-spheres as end shells. The numerical and experimental results presented good agreement. In addition, longitudinal resonant modes were excited by the transversal motion of the tank and four different flow patterns were identified, including a double swirling flow. Furthermore, numerical simulations were performed for two additional models, with prolate and oblate semi-spheroidal end shells. The tank with prolate end shell did not show the formation of the double swirling. INTRODUCTION Liquid Natural Gas (LNG) is the most environmental-friendly fossil fuel since it produces the lowest greenhouse gas emissions per unit of energy. In such sense, the demand for LNG as energy source increased remarkably in recent years (International Gas Union, 2019). The LNG is gradually replacing traditional high sulphur bunker fuel as fuel in a number of new ship engines, known as small-scale LNG. Horizontal axisymmetric tanks are commonly used as LNG fuel containers but also could be adopted as LNG cargo tanks, such as the IMO type C tanks of pressure vessels. The violent fluid motion in partially filled containers, known as sloshing, is particularly dangerous for the case of LNG fuel tanks because it may result in a rapid drop in the system pressure and impair the operation of the gas-fuel system (Grotle, 2018). Several works in the literature investigated the sloshing in tanks with different shapes, including cylindrical and spherical containers. Budiansky (1960) proposed analytical estimations for the resonance frequencies of sloshing on horizontal cylinders and spherical containers from the solution of the boundary value problem with conformal mapping. McIver (1989) estimated analytically the lowest four symmetric and anti-symmetric modes of sloshing for cylindrical and spherical containers by using a toroidal coordinate transformation. McCarty and Stephens (1960) performed experiments to estimate the resonant frequencies of cylindrical and spherical containers.

In the process of long-distance ocean transportation, the wave and the tank sloshing have a great influence on the ship motion. The sloshing of the liquid in the tank will produce a large moment to the hull, which may cause the ship to overturn; and the strong impact force of the sloshing on the bulkhead may also cause damage to the hull structure. In this paper, sloshing coupled ship motions are solved numerically in a time domain approach, such as numerical method based on Reynolds-averaged Navier–Stokes (RANS) equation. Through comparison with the experimental data of S175 ship model loaded with tank at zero speed, present numerical methods are validated. Under the head sea conditions with forward speed, the movement effects of ship with or without tank are compared and analyzed. Furthermore, the influence of tank sloshing under different working conditions and the wave contour around ship are systematically studied. INTRODUCTION With the development technology of liquefied natural gas (LNG) ships and liquefied petroleum gas (LPG) ships, the impact of tank sloshing on ship movements has received increasing attention. During the navigation of such liquid-laden ships in the ocean, multi-degree-of-freedom motions will occur under the action of wind and waves, and the liquid contained in ship tanks will also cause sloshing due to the corresponding movement of the hull. With such sloshing phenomenon, when the frequency of the external incoming wave and the natural frequency of the tank are relatively close, the fluid attack effect caused by its severe resonance phenomenon acts on the bulkhead, which not only has a great possibility of causing serious damage to the bulkhead structure but also increase the amplitude of the motion of the hull. Serious conditions may cause the ship to capsize, which will have a more serious impact on the ship's navigation environment and safety factors.

The intricate physical mechanisms involved during sloshing impacts in LNG tanks lead to biases in sloshing model tests when the impact loads are predicted. In order to increase the understanding of these biases, a new state-of-the-art facility dubbed the Multiphase Wave Lab (MWL) has been established. In the MWL, impact tests are performed within an autoclave (15 m long x 2.5 m diameter), whose purpose is to provide an accurately controlled environment in which the pressure, temperature and gas composition can be controlled and monitored. Wave impact tests are performed by generating waves in a flume which is located inside the autoclave. In this paper, we present the capabilities of the MWL to control the temperature, ullage pressure and gas composition in the autoclave. We study also the quality of the global flow repeatability by means of a breaking wave which is created with a wave-focusing technique. We quantify the repeatability of the waves with a Sobolevnorm-like criterion on the frequency domain and evaluate the repeatability for different ullage pressures. Preliminary experiments show a good degree of repeatability, in accordance with high-speed recordings of the impacting waves. INTRODUCTION Ships that transport liquefied natural gas (LNG), floating units that produce or re-gasify LNG and ships that use LNG as a fuel need to be equipped with dedicated tanks to hold the LNG and minimize the heat transfer between the LNG and the environment (LNG is stored at -162°C at atmospheric pressure). In terms of containment, membrane LNG tanks such as the NO-line and the Mark-line tanks (GTT, France) are widely used because they utilize the hull space efficiently. However, these structures are more sensitive to sloshing impacts inside the tanks. Thus, it becomes of great importance to quantitatively assess the magnitude of these impacting forces in the design stage. Currently, this is done by performing sloshing model tests at reduced scale (Gervaise et al., 2009). These tests, however, are inherently biased. Empirical scaling factors based on feedback at sea are then used to account for these biases. Dedicated measurements on-board LNG carriers have shown that the long-term statistics of the impact loads as defined by the prevailing sloshing assessment methodology are conservative (Lund-Johansen et al., 2011; Pasquier & Berthon, 2010). However, the short-term statistics derived from the tests do not consistently represent reality (Karimi et al., 2014). Resolving this inconsistency between the scaled and the full-scale measurements would lead to optimized tank designs in terms of strength and thermal capacity, as well as to increasing the operating envelope of the vessels (e.g. operating with partially-filled tanks).

One of the possible solutions, LNG propulsion has been widely adopted in order to handle a 0.5% sulphur cap for the ship's fuel oil in compliance with IMO 2020 other than the SOx scrubber and using the low-sulphur fuel. Recently, the LNG fueled Ultra Large Containerships (ULCs) have been developed in order to meet these needs. For example, their LNG fuel tanks instead of conventional heavy fuel oil (HFO) tanks could be designed as IMO type B type or Membrane type depending on the Owner's preference or CAPEX. This paper is basically to introduce the design concept for the LNG fueled ULCs which has been designed and consistently developed by DSME. In addition, the outstanding engineering technologies for the novel design of the LNG fueled ULCs is to be presented which should be inevitably required to ensure the structural adequacy. Consequently, the results of the economic efficiency evaluation for the application of each LNG fuel tank type (IMO type B or Membrane type) will be shown on this paper for reference. INTRODUCTION On 1 January 2020, International Maritime Organization (IMO) will implement a new regulation, a 0.5% global sulphur cap for marine fuels. Accordingly, all commercial ships shall use a marine fuels with a sulphur content of no more than 0.5% against the current limit of 3.5% in an effort to reduce amount of sulphur oxide except for the Emission Control Areas (ECAs) where 0.1% S content since 2015. To comply with this IMO 2020 requirement except for the marine gas oil (low sulpur distillate fuel), there are multiple options as follows: Heavy fuel oil: 0.1% ultra low sulphur fuel oil (ULSFO) and 0.5% very low Sulphur fuel oil (VLSFO) Exhaust gas cleaning system (scrubber) LNG fuel Alternative fuels: liquefied petroleum gas, methanol, biofuel, compressed natural gas, solar power and fuel cells etc. Of the mentioned things above, LNG fuel is well known to be the most cost-competitive which is available to clients today. In connection with this, the newbuilding LNG fueled vessels have been steadily increased up to about 440 vessels every year as shown on Fig. 1.

In this work, computational fluid dynamics (CFD) simulations have been conducted on leaked LNG vapor diffusion in which the gas is discharged from the vent post of a LNG powered RORO ship. A numerical model is proposed based on an open source Computational Fluid Dynamics (CFD) tool called OpenFOAM® for numerical simulation of the turbulent gas diffusion. The numerical method is first validated against a benchmark case and an experimental case. Two turbulence models, k-ε and LES, are applied and the numerical results are compared and discussed. By using the proposed numerical model, a series of LES simulations have been conducted on the LNG vapor diffusion of the RORO ship under several wind speeds and air temperatures. INTRODUCTION In recent years, a number of LNG powered merchant ships have been or are being built for the advantage of cleaner emissions over conventional oil engines. However, since LNG is of extremely low temperatures, using it as fuel for merchant ships introduces new systems on board together with their associated risks. One of the major risks is the LNG vapor (natural gas) leakage which should be thoroughly investigated. Due to the very low boiling point (111.7 K), once LNG is leaked it vaporizes very quickly. At atmospheric conditions, the cold LNG vapor is about 1.5 times heavier than the ambient air (Koopman & Ermak, 2007), and therefore is called as a dense or a heavy gas. The leaked LNG vapor, mainly in the engine room, will be collected and discharged from the vent post of the ship into the air. Then the gas will be diffused by the surrounding turbulence air flow. To design such ships, it is needed to ensure that the concentration of the leaked gas on designated areas of the ship does not exceed a safety value. Prediction of the gas diffusion needs to consider ship speed, superstructures of the ship, and surrounding air conditions such as the wind and temperature.

In this work, we performed a comprehensive analysis of possible technical solutions for the main facilities for the development of hydrocarbon deposits in the southwestern part of the Kara Sea, the selection of competitive options for in-depth study at the subsequent design stages, identification of critical technologies required for the implementation of the selected conceptual solution, as well as the development of schedule for further work. INTRODUCTION A conceptual solution is understood in this work as a selection of type(s) of the facility and a selection of the best possible design option(s) among the obtained number of facilities, as well as determination of its basic dimensions, weight and check of stability on soil (for facilities standing on the bottom). Riser types and main characteristics of anchoring systems shall be selected for floating facilities. Then it is needed to select a facility type (or a set of facility types) and to obtain main technical characteristics of the best possible facilities that fulfill functional requirements under given metocean and soil conditions. Finally, the best possible facility option is selected out of various technically feasible options using developed criteria, some of which are brought into the category of restrictions. The choice of facility type shall be based on a number of influences that may include the following (Mirzoev, 2009): Technological; Engineering and geologic; Metocean (geographic); Production; Environmental. At the current stage, special attention will be paid to the first three influences. Facility selection taking into account these influences is a Next, the best possible facility must be selected out of the chosen technically feasible facilities. A number of criteria should be developed to select the best possible facility. The criteria allowing to determine the best possible facility may include the following (Mirzoev, 2009): Proven technical solutions; Manufacturability; Composition of materials; Material intensity of each material; Compliance with requirements of current regulations; Cost of the facility (taking into account 2, 3, 4).

ABSTRACT To quantify and set up the LNG carrier's Moving Safety Zone is the precondition for ensuring the safety of the LNG carrier in the Yangtze River downstream. Based on the car-following model of traffic flow and the control characteristics of the LNG carrier, the mathematical model of the LNG carrier's braking maneuver is constructed. Applying the theory of ship domain to construct the ship domain of inland LNG carrier, then adapted to the characteristics of the channel in the downstream of the Yangtze River, so that the scale of LNG carrier's Moving Safety Zone is quantificationally defined and the longitudinal scale of LNG carrier's Moving Safety Zone is further obtained INTRODUCTION For a long time, China's energy structure system, with coal as its main energy source, has been challenged by air pollution, acid rain and declining atmospheric quality. Therefore, it is imperative to adjust the energy structure. Liquefied Natural Gas (LNG) has attracted more and more attention due to its advantages of easy transportation, high storage efficiency and environmental protection. Although LNG reserves are abundant in China, most of its producing areas are far away from industrial and population-intensive areas, especially in offshore gas development. Therefore, transportation and storage problems must be solved. LNG itself has the characteristics of low temperature, explosiveness and evaporation, which lead to high cost and high risk of LNG carrier, so it is particularly important to ensure the safety of LNG ship in the process of transportation. Especially in the areas near the port where the traffic flow density of LNG ships is high, it needs more attention from operators, ship pilots and port managers. In order to ensure the safety of LNG ships entering and leaving the port, the concept of safety zone is put forward. But up to now, there is no unified standard for the definition of safety zone. The size of safety zone varies with the size of LNG ships, the navigation environment of port waters, the meteorology during the process of ships entering and leaving the port, the sea conditions and the navigation density of local ports. If the scope of the safety zone is too large, not only can not effectively restrict the surrounding ships, but also waste the manpower and material resources of the port, waterway and other management departments, prolonging the impact on the normal navigation of the waterway; if it is too small, it can not limit the interception of surrounding ships to ensure the safety of ships. Therefore, the study on the safety zone of LNG ships in inland navigation process not only provides a reliable barrier for the safety of LNG ships, but also reduces the impact on inland navigation, which has important practical significance for the implementation of safety protection measures for waterways.

ABSTRACT Several features of an industrial sloshing model test are presented. Data mining is conducted for an experimental database at Seoul National University. 3,000 different test cases have been fetched from the database. The fetched data are 15,000 hours of 6DoF irregular model tests with various cargo hold dimensions, floating units, environmental conditions, and operational conditions in 1/50 – o1/30 scales. The severity of the model test based on the impulse peak pressures is described. A correlation between 6DoF motions and the severities are illustrated. Dynamic characteristics of sloshing events are discussed by unsupervised machine learning techniques. INTRODUCTION When the LNG tanks of the floating units are designed, it is important to analyze possible sloshing loads. Since the LNG transportation market has been continuously expanded (BP, 2018), numerous LNG carriers have been constructed. In addition to the LNG carriers, a lot of LNG fueled ships have been built because emission regulations of greenhouse gases have been tightened. Moreover, owing to the increasing size of the floating units (Kuo et al., 2009; Malenica et al., 2017), accessing the sloshing loads becomes more significant. Because of the highly nonlinear and complex nature, the sloshing impacts are commonly analyzed by conducting a model test (Malenica et al. 2017) in a 1/50 or 1/40 scale. ITTC and the Classification societies suggest several guidelines of the test (ABS, 2009; BV, 2011a; 2011b; DNV-GL, 2006; ITTC, 2014; LR, 2009), and numerous sloshing model test have been conducted as an industrial project (Gavory and de Seze, 2009; Malenica et al., 2017, Ryu et al., 2016). Seoul National University (SNU) has carried out parts of these industrial sloshing model tests and has created an experimental database from those model tests (Ahn et al., 2018; Lee et al., 2018; Kim et al., 2017; Oh et al., 2015; Park et al., 2009; 2014). The present paper presents three parts of an industrial sloshing model test: a severity of sloshing impact peak pressure, a relation between 6DoF motions and the peak pressures, and dynamic characteristics of the sloshing events. First, an industrial sloshing model test is briefly introduced. A database of the industrial sloshing model test in SNU is described. Second, the severity, which is analyzed based on the impulse peak pressure, of the database is presented. The severities on the location are also presented by the faces of the cargo hold models. Last, several data mining techniques are used to analyze the dynamic characteristics of the sloshing events, which occur during the industrial sloshing model test. Rise times and rise impulse areas are mainly discussed. Clustering techniques for the data are illustrated, and the results are discussed.

ABSTRACT No-vent filling (NVF) is important to reduce the boil-off gas during LNG filling process. This paper suggests a numerical model for predicting the NVF process with considering the transfer line chill-down effect. The model simulates the pressure history of the NVF process in various conditions. The calculation error of the pressure history during the NVF process by the model has been reduced from 14% to 6%. Furthermore, the NVF simulation for large scale storage tanks as large as an actual LNG tank is conducted, and a guideline for NVF model to an actual system is suggested accordingly. INTRODUCTION Natural Gas (NG) is a kind of clean energy, which is safer than liquefied propane gas (LPG) and cleaner than petroleum gas. Since the demand for NG increases (Cornot-Gandolphe, S, Appert, O, Dickel, R, Chabrelie, M-F and Rojey, A, 2003), several research groups have studied the transfer and management technologies of NG. NG is generally transported in a liquid state, as liquefied natural gas (LNG), to increase the energy density. The normal boiling temperature of LNG is approximately 110 K, so it has to be managed to maintain the low temperature during the transportation and storage process to reduce boil-off gas (BOG). However, BOG is indispensable during the transfer process of LNG due to the warm storage tank and transfer line in general. The generated BOG has to be vented to maintain the tank pressure for the safety reason, which causes a waste of the fuel. Furthermore, as the main component of NG, methane (CH4), is the greenhouse gas, the vented BOG will increase the emission of greenhouse gas. Therefore, reducing the BOG is important to prevent environmental problems. One of the cryogenic fluid transfer methods called no-vent filling (NVF) can solve the BOG problems. The first idea of NVF was suggested by NASA (Chato, DJ, 1989), and the key parameter of NVF was also studied by aerospace engineers (Taylor, W and Chato, D, 1991). Fig. 1 (a) shows the schematic illustration of the NVF process. The transferred fluid is supposed to be filled into the storage tank without a venting port. The tank pressure spontaneously increases by cooling down of the storage tank as well as the transfer line with cold liquid. The large temperature difference between the storage tank and the incoming fluid into the tank generates a large amount of the vaporized gas at the initial state, and the storage tank is abruptly pressurized. The degree of pressurization of the storage tank at the initial filling process can be alleviated by the small temperature difference between the tank and the incoming fluid. When the tank pressure becomes larger than the saturation pressure of the liquid in the tank, condensation occurs. Then the pressure can be held at a nearly constant value. The pressure history during a typical NVF process is shown in Fig. 1 (b). Since the NVF is carried out by the pressure difference of a supply tank and a receiver tank, the pressurizing process at the initial state of the filling process is critical to determine the result of NVF. If the effect of the evaporation process is larger than the effect of the condensation process, the tank pressure may reach the supply pressure, and the NVF process will stop. The previous research (Taylor, W and Chato, D, 1991) mentioned earlier was conducted with liquid hydrogen and liquid nitrogen. In addition, the safety verification of the actual LNG tank (the allowable pressure) also has to be checked. In order to simulate the NVF process with LNG, previous studies on NVF were carried out using tetrafluoromethane (CF4) due to a similar molecular structure with methane. A non-dimensional map was suggested to predict the NVF results (Kim, Y, Lee, C, Park, J, Seo, M and Jeong, S, 2016), and a numerical analytic model was also proposed by CF4 (Kim, KJ, Jin, L, Kim, Y and Jeong, S, 2017). The numerical model can simulate the pressure of the storage tank during the drastic pressurizing at the initial state of the filling process. However, the numerical model was verified at the pressure conditions about 200 kPa or higher. To apply the NVF process to a low-pressure actual LNG storage tank, it should be verified to ensure that it can be performed below the allowable pressure of the real LNG tank. In addition, if the thermal inertia of the transfer line becomes large, the tank pressurization effect by the transfer line chill-down process becomes important. The line chill-down process with liquid methane was simulated by considering two-phase flow heat transfer (Jin, L and Jeong, S, 2018). The simulation results of the line chill-down process by liquid methane shows that the single-phase vapor convection is the dominant mechanism during the chill-down process due to the physical property of methane.

ABSTRACT Classical RANS turbulence closure models bring the excessive turbulence level which leads to the unphysical interface motion in the simulation of the sloshing flow. This paper aims to explore the appropriate turbulence modeling method and proposes two modifications to improve the unphysical interface motion. One is to modify the transport equations, in which the density term and buoyancy effect are considered in the equations. The other is to add an eddy-viscosity limiter, particularly a linear limiter is designed. The comparison between this work and the previous experiments shows that both modifications are effective to improve the unphysical interface motion. INTRODUCTION As the demand for clean energy increases, two novel vessels are developed to operate on the sea for a long time. They are the FLNG (floating liquefied natural gas) vessel which can collect the natural gas from the sea and the FSRU (floating storage and regasification unit) which is a vital component to transfer the LNG. Those ships are exposed to external excitations caused by wind or sea waves, which inevitably trigger the resonant sloshing in partially filled tanks. Sloshing influences the ship motion and threatens the structural safety. DNV-GL considers that sloshing brings the largest uncertainty in the design stage. Nowadays, computational fluid dynamics (CFD) becomes an excellent tool to investigate the sloshing phenomenon with the rapid development in computer technology. Sloshing is an interfacial flow with strong turbulence effects. Maillard and Brosset (2009) and Karimi et al. (2016) found that the gas phase plays a crucial role in the sloshing flow, indicating the equal importance of the gas and liquid phase. For the two-phase flow, the numerical methods can be divided into two categories, one is the multi-fluid model, and the other is the single-fluid model. In the multi-fluid model, each phase has its own set of governing equations. In the single-fluid model, the two-phase flow is considered as a new single continuum fluid with immediate jumps of the associated properties across the interface, e.g., the density and the viscosity, resulting a single set of governing equations to be solved. The single-fluid model is more commonly used for the problems related to wave-elevation prediction, and it is adopted by the commercial software, such as ANSYS Fluent and STAR-CCM+, as well as the open-source package, OpenFOAM. Moreover, Reynolds-averaged Navier-Stokes (RANS) simulation is more popular than large eddy simulation (LES) and direct numerical simulation (DNS) because LES and DNS have much larger computation effort than RANS. Volume-of-fluid (VOF) method is used to capture the interface because the mass conservation is essential in such an enclosed tank (Roenby et al. (2016), Bilger et al. (2017)).

ABSTRACT Offshore floating liquefied natural gas facility (FLNG) is one of the important facilities for developing deepwater gas fields. It is very important that FLNG liquefaction process is suitable for the offshore environment in South China Sea. This paper, taking a deepwater gas field in the South China Sea as the research object, based on propane pre-cooling and dual nitrogen expansion liquefaction process, compares and analyzes the enlargement of a small-scale experimental facility, a pilot plant and a target actual gas field. Through the sensitivity analysis of amplification of FLNG liquefaction process system with three different natural gas scales, it is considered that with the scale-up, liquefaction process flow is more optimized, equipment selection is more reasonable, specific power consumption is gradually reduced, the influence of feed gas flow rate, temperature and pressure on power consumption is gradually reduced, and the adaptability to feed gas is stronger, and the sensitivity will decrease. Through the magnification analysis, it is considered that the experimental rules obtained by FLNG small-scale and pilot plant simulation can be extended to target gas field. It is proved that propane pre-cooling and dual nitrogen expansion liquefaction process has good offshore adaptability for target gas field. INTRODUCTION China's sea area is 3 million square kilometers, and the total oil and gas resources in the South China Sea account for more than one third of the total oil and gas resources in the country. 70% of offshore oil and gas resources are in deep water, the total offshore oil and gas resources in deep water in the South China Sea are about 35 billion tons of oil equivalent, and the amount of gas hydrate resources is about 80 billion tons of oil equivalent, which is called "the second Persian Gulf". Natural gas resources account for 83% of the total oil and gas resources in the South China Sea. 70% of the natural gas resources come from deep water. How to develop the natural gas resources in South China Sea economically and effectively has gradually become one of the focuses of attention. Conventional pipeline transportation of natural gas may not be suitable for the development of deepwater gas fields in the South China Sea due to technical and economic factors, so it is urgent to develop a new type of engineering development mode. Floating Liquid Natural Gas (FLNG) is a new type of FPSO device which integrates liquefaction, storage and processing of offshore natural gas and petroleum gas. It has the characteristics of short construction period, flexible development, independent development, recyclability and reusability. It can be applied to small, medium and large offshore gas fields. It is suitable for shallow and deep water gas field development(Kirillov N G,2004; Iversen I,2009; Ganielsen HK). Liquefaction process is one of the key technologies of offshore FLNG plant and one of the main parts of FLNG distinguishing FPSO. At present, our country is still in the initial stage of liquefaction process technology. Liquefaction process is under the patent protection of international countries(Gu Anzhong,2010; Yu Xichong et al.,2014). Most onshore liquefaction plants adopt liquefaction process packages provided by international patent companies. The liquefaction process of offshore FLNG should meet the following requirements(Zhu Jianlu,2012; Liu Miaoer et al, 2015): Simple, compact, small number of equipment, less occupied area, low overall demand for topside deck space; high degree of production automation, safe and reliable operation, ship swaying will not significantly affect its performance; easy to start and stop; strong operational and maintainability in marine environment; more adaptable to changes in inlet gas components and inlet gas flow rate, etc. Therefore, a comprehensive analysis of technology, economy and security is needed(Yu Xichong et al,2015).

ABSTRACT As a solution to the emission controls, there is an increasing interest in the use of LNG as ship fuel. Accordingly various types and materials are suggested for the containment system of LNG. In this study, the various cryogenic materials for the IMO Type C LNG fuel tank are reviewed to be installed on world's first LNG-fuelled AFRAMAX tanker. The design results and relevant costs are compared for the LNG fuel tanks made of various cryogenic materials such as 9% nickel alloy steel, stainless steel, aluminum and high manganese steel. The LNG fuel tanks of each material have been designed reflecting the material characteristics adopted by Classification Societies. In order to verify the structural integrity, the LNG fuel tank structures have been evaluated through structural strength assessment. Finally, after the cost comparison using the weight of base metal, the weight of relevant weldment and the required manpower considering weldability of each material, 9% nickel alloy steel has been selected as the optimum material for the LNG fuel tank. INTRODUCTION An emission of nitrogen dioxide, sulfur dioxide and carbon dioxide has been limited and continuously decreased by various Regulations adopted by IMO. The emission of nitrogen dioxide was already limited to 80 percent lower than conventional emission level by Tier III regulation taken effect in 2016. Especially, in 2020, sulfur content in fuel shall be decreased to 0.1% for ships cruising in ECAs and to 0.5% in worldwide. The emission of carbon dioxide has been reduced gradually by adopting EEDI phases I through III which will further limit the emission amount by introducing phases IV and V. To comply with the Regulations for emission limitation, ship owners carefully consider choosing a best way among emission reduction methods, such as the installation of Scrubber/SCR/EGR while using conventional fuel oil, the adoption of various energy saving devices and the use of alternative fuel. Among them, LNG has been considered as one of promising alternative fuel and chosen by a few ship owners. However, its high capital expenditure for fuel tank, FGSS and relevant equipment makes ship owners reluctant to adopt.

ABSTRACT Sloshing impact loads have been reported repeatedly throughout the lifetime of the ship. However, a study on the mechanical performance of polyurethane foam with repetitive impact load has not been conducted despite the necessity of evaluation. Therefore, in this study, the effect of repetitive impact loading on mechanical behavior of glass fiber reinforced polyurethane foam was investigated. To do this, a series of drop impact test was performed on glass fiber reinforced polyurethane foam which applied to LNG insulation panel. After the impact test, evaluation of mechanical behavior was conducted. INTRODUCTION The glass fiber-reinforced polyurethane foam (RPUF) has excellent mechanical performance and thermal insulation performance due to the porous microstructure with glass fiber and has been applied to cryogenic environmental structure (Desai et al., 2000). The liquefied natural gas (LNG) cargo hold should be able to withstand the impact load, thermal load and hydrostatic pressure (Park et al., 2016a). Fig. 1 shows typical failure in polymer foam for insulation panel under the repetitive impact of low energy. Failure of LNG cargo hold even under not an extreme condition can lead to a great loss of property and human life. Therefore, structural integrity and failure prediction are very important. A performance evaluation study was also conducted considering the operating environment of the LNG storage structure to predict the behavior and damage of polyurethane foam. Park et al. (2016b) analyzed the effect of temperature on the compressive behavior of various types of polymer foams used in cryogenic applications (Park et al., 2016b). Denay et al. (2013) analyzed the behavior of polyurethane foams under various loading conditions such as monotonous, repeated compressive and creep loading under cryogenic environment (Denay et al., 2013). The tensile, compressive and shear performance of polyurethane foam under high strain rate range using Hopkins bar were also performed (Pellegrino et al, 2015).

ABSTRACT Refrigeration system is regarded as the significant factor to influence the utilization efficiency of liquefied natural gas (LNG) cold energy, and proper selection of refrigerant can decrease exergy loss and increase the cold energy utilization. As refrigerant played a key role for thermal transport procedure, various refrigerant design methods were reviewed, and the refrigerant selection principle was determined. Furthermore, a new molecular design method for newly developed refrigerants and existing refrigerants modified was proposed. Based on this method, refrigerants with optimal thermodynamic properties were generated, which could work efficiently for LNG cold energy power generation system. For the molecular design method verification, a LNG cold energy power generation system with two circulation loops was designed, seawater worked as high temperature heat source, combined with the low temperature LNG cold energy. INTRODUCTION As the energy consumption increases, utilization of the low grade thermal energy becomes more and more important because of cost effectiveness of operation. The performances of the fluid are directly connected with the effective using and transferring of thermal energy, especially in the field of thermal conversions. In particular, the organic fluids have many different characteristics from water (Stine and Harrigan, 1985). Therefore, working fluids used in organic Rankine cycles have been studied. However, performance of the organic fluids varied depending on the working conditions (Musthafah and Yamada, 2010). The thermal and physical properties of the fluid are influenced by temperature (Yuan et al., 2016), and this lead to various thermal coefficients. Fredy et al. simulated a Rankine cycle operating at low temperature (2012), with the pressure ratio of 2.5 and the temperature ranging approximately from 70 to 85, and eventually R152a offers the best performance. While for temperature between 85°C and 97°C, the fluid with best performance turned out the R290. This result is demonstrated by the research (Bertrand et al., 2009), which shows that R152a, R600a, R600 and R290 offer attractive performances. In addition, R407C appears high evaporator pressure and low efficiency, R12, R113, R114 and R500 result high GWP and high ODP, RC318 results high GWP, R141b shows high turbine outlet volume flow rate and high ODP. R134a followed by R152a, R290, R600 and R600a emerges as most suitable fluid for low-temperature applications with heat source temperature below 90°C. However, the disadvantages of R290 are also obviously: it is combustible and the size of the compressor would be bigger than that of using R22 in the assigned refrigeration machine (Hadya et al., 2012). Furthermore, R227ea gives the highest power for heat source temperature range of 80–160°C in another study (Amlaku and Bolland, 2010), and R245fa produces the highest power in the range of 160–200°C. The least heat exchanger area required at constant power rating is found when the working fluid is npentane, the turbine size factor of R134a is smaller compared to other working fluids. However, R134a requires more heat exchanger surface area. According to these results, working fluids with high vapor pressure has lower turbine size factor. Finally, 35 organic working fluids were reviewed for the conversion of low grade heat (Chen et al., 2010). The results showed that working fluids with high density and high latent heat provide high unit turbine work output, also, isentropic and dry fluids are preferred in organic Rankine cycles. In conclusion, various researches have been done on the working fluids for low temperature Organic Rankine cycles. On the other hand, there is no fluid which can fit for one certain cycle. Various fluids working for the thermal cycles have their own characteristics with the production issues, and for this reason, numerous efforts have been made to modify the thermodynamic characteristics of working fluid.

ABSTRACT We studied the optimization method to reduce the amount of resin rope that used to fill the gap between the LNG tank and insulation panels while complying with the flatness criteria of the insulation panels. The space between the thermal insulation panels and LNG tank hull should be reduced to minimize the use of resin rope. In this study, the corrugation of the inner side of the hull is measured, and the offset table of the corrugation is used to calculate the deformation of the LNG tank hull. To solve the optimization problem, an objective function with constraints is mathematically formulated and solved by using the genetic algorithm. To check the applicability of the proposed method, we simulated thermal insulation panel installation and compared with an existing program. The results show that the proposed method can be effectively used for installation of the thermal insulation panels of the LNG tank. INTRODUCTION As the importance of LNG carriers increases, it is needed to improve value-added and increase the competitiveness of LNG carriers. Design of the LNG tank is one of the most important factors in the design of the LNG carrier. Because the LNG carrier transports low-temperature LNG, the thermal insulation panel is used inside of LNG tank to maintain the temperature of LNG. But because the inside hull of the LNG tank is rugged, the resin ropes are used to equalize the height and flatten the slope of the insulation panel. A large amount of resin ropes is necessary to fill the gap between thermal insulation panels and LNG tank especially when the LNG tank hull's flatness is uneven, and this will increase the production cost of the LNG carrier (Chun et al., 2009; Kim et al., 2010). To decrease the amount of reins rope, there is a software that calculates the estimated amount of resin ropes while complying with the flatness criteria of the insulation panels made by GTT. The software tends to demand additional usage of resin ropes because the software is focused on the flatness of the thermal insulation panel and wouldn't reflect the recent change of LNG carrier and thermal insulation panel. In this study, the amount of resin ropes is reduced as a primary target while the flatness criteria of thermal insulation panel are satisfied.

ABSTRACT Floating LNG Bunkering Terminal(FLBT) is a newly emerging offshore platform which can be regarded as a LNG station at sea. It has its own station-keeping system, while it is additionally moored with other vessels during LNG loading or unloading processes. The ship-to-ship mooring system is composed with a number of mooring ropes and fenders, which might trigger unexpected motions. In this study, eigenvalue analysis was conducted, which gives the resonant frequencies and modes of vessels induced by the ship-to-ship mooring system. These eigenvalues were drawn in the model test results. Finally, we figured out some notable characteristics induced by ship-to-ship mooring system. INTRODUCTION A demand on energy resources has been steadily increased according to the world population increasing. Among alternative resources which might supplement the present fossil fuels, a natural gas is considered as environmental-friendly as the emissions from this resource has almost no sulfur. Recently, a liquefied natural gas(LNG) has been studied as a marine fuel respond to the enhanced regulation on sulfur emission by International Maritime Organization(IMO). In order to operate LNG fueled vessels frequently, the infrastructures shall be established properly. Since an onshore LNG supplying terminal has a potential danger of explosion, a new concept of offshore terminals have been considered. In Korea, a national R&D project has been conducted since 2014 in order to develop the core technologies of an floating type LNG bunkering terminal(FLBT). It aims to be moored at the certain target ocean sea, and receive LNG from LNG carrier(LNGC) and give LNG to LNG bunkering shuttles(LNG BSs) simultaneously. FLBT is self-moored by the internal turret and catenary mooring lines, while LNGC and other LNG BSs are side-by-side(SBS) moored to FLBT with mooring ropes and fenders. As a number of ship-to-ship(STS) mooring lines or fenders are included in the LNG transfer process, it is necessary to figure out the effect of the STS mooring system precisely.