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The performance of Luvicap EG was investigated to verify the efficacy of mixing kinetic hydrate inhibitors (KHIs) and monoethylene glycol (MEG) while varying the pH conditions in an aqueous phase. ...

Thermal conductivity measurements of pure R1243zf and binary mixtures of R32 + R1243zf and R32 + R1234yf were conducted in the homogeneous liquid and vapour phases with a transient hot-wire technique. The mole fractions of R32 are 0.25, 0.50, and 0.75 in both binary systems. The temperature range of the measurements was from (264.1 to 405.6) K with pressures ranging between (0.9 and 6.1) MPa. The transient hot-wire apparatus was validated with measurements of pure CO2 in both the liquid and vapour regions. The relative combined expanded uncertainty (k = 2) in the experimental thermal conductivity was approximately 2.0 %. The relative deviations of the measured thermal conductivities from those calculated using the extended corresponding states (ECS) model as implemented in the software REFPROP 10 were between (−13 and 10) % in the vapour phase, and between (−14 and 1) % in the liquid phase. Additionally, the performance of a new approach to predicting fluid transport properties, the residual entropy scaling model incorporating the cubic-plus-association equation of state (RES-CPA model) was tested for these mixtures by first determining the scaling parameter of pure R1243zf. The RES-CPA model was then able to predict the mixture thermal conductivities generally within 10 %, which is similar to the ECS model; however no additional parameters were introduced to the RES-CPA model to describe binary interactions.

This paper presents the damage assessment of a free-fall dropped object on the seabed. The damage to a dropped object totally depends on the relationship between the impact energy and the soil strength at the mudline. In this study, unexpected dropping scenarios were first assumed by varying the relevant range of the impact velocity, structure geometry at the moment of impact, and soil strength profile along the penetration depth. Theoretical damage assessments were then undertaken for a free-fall dropping event with a fixed final embedment depth for the structure. This paper also describes the results of a three-dimensional large deformation finite element analysis undertaken for the purpose of validation. The analyses were carried out using the coupled Eulerian-Lagrangian approach, modifying the simple elastic-perfectly plastic Tresca soil model. The validation exercises for each dropping scenario showed good agreement, and the present numerical approach was capable of predicting the behavior of a free-fall dropped object.

The objective of this study is to develop a conceptual design for a hydrogen liquefaction process at a 300 tonnes per day scale. The process uses cold energy from the vaporization of liquefied natural gas and is integrated with a steam methane reforming process. This study is motivated by the fact that a cryogenic cooling system requires a large amount of energy to liquefy hydrogen. Moreover, sea water is mostly used as the heating medium for the vaporization of liquefied natural gas at terminals. The proposed process is compared with the commercialized hydrogen liquefaction process to verify its efficiency and feasibility. The simulation results reveal that the liquefaction energy is reduced from 13.58 kWh/kg of liquid hydrogen to 11.05 kWh/kg with proposed process. The cost associated with liquid hydrogen production is approximately USD 2.53/kg, making it economically viable. The results of this study can contribute to improving the hydrogen economy by using liquefied natural gas cooling system to liquefy hydrogen.

This paper provides the design basis and case study of soil improvement to secure the stability of jack up rig under operation and fabrication condition to effectively mitigate the risk associated with unexpected spudcan penetration. The two penetration curves of spudcan foundation are presented to confirm soil improvement influence using DMM (Deep Mixing Method) with native soil material. The results from 3D large deformation finite element (LDFE) analyses are reported on vertical penetration of skirted spudcan into multilayer clays. The LDFE analyses were carried out using the Coupled Eulerian-Lagrangian (CEL) approach and the modified simple elastic-perfectly plastic Tresca soil model. The seabed sediments were simulated as single layer soft clay with undrained shear strength increasing linearly with depth, two-layer stiff clayey sand overlying soft clay and sandy gravel. The circular block of soil improvement is partially located in the third sandy clay layer under the spudcan penetration path with specific thickness. The result with native soil condition is validated against ISO recommendation and the penetration curve for reinforced section is also overlaid concurrently. The punch-through phenomeneon predicted in the assessement by ISO method is replicated in the numerical analysis. The validation exercise of the original case shows a good agreement and the present numerical approach is capable of predicting the behavior of a spudcan penetration in multi-layered soil. The partially reinforced layer shows the load distribution during spudcan penetration. It provides the reduction of penetration depth under a given preload and seabed conditions efficiently. To ensure the structural stability of jack up rig, the uncertainties of site condition during installation should be removed such as partially trapped soft soil or soft thin layer at the footing location. The presented numerical approach can provide reasonable design basis for soil treatment to mitigate stability risk.

The sloshing flows in a LNG cargo tank model (1/50 scale) of a ship are measured by an embedded panoramicPIV system. The measurement system consists of a Nd-Yag laser(120mJ, 15Hz), two cameras(1k x 1k) and a host computer. Four experimental cases were tested for the tank model, in which swaying motions are made by a 6 DOF-motion platform. The amplitudes of swaying are 9.76mm and 29.29mm, and the swaying frequencies are 0.633Hz and 0.828Hz. The measurement regions are the vertical plane 50mm away from the front wall of the tank where a pump tower is installed. It was verified that the flow patterns of the sloshing are similar to each other when the swaying amplitudes are similar.

The violent free-surface motions interacting with structures are investigated using the moving particle semi-implicit (MPS) method, which was originally proposed by Koshizuka and Oka (1996) for incompressible flow simulation. In the present numerical method, a more efficient algorithm for Lagrangian moving particles is used for solving various highly nonlinear free-surface problems without using the Eulerian approach or the grid system. Therefore, the convection terms and time derivatives in the Navier–Stokes equation can be calculated more directly without any numerical diffusion, instabilities, or topological failure. In particular, the MPS method is applied to the simulation of liquid-entry and slamming problems, such as wet-drop (liquid–liquid collision) tests in an LNG tank and slamming loads (solid–liquid collision) on rigid plates with various incident angles. The numerical results are in good agreement with available experimental data.

The free-surface motions interacting with structures are invest igated numerically using the Moving Particle Semi-implicit (MPS) method proposed by Koshizuk a et al. (1996) for solving incompressible flow. In the method, Lagrangian moving particles are used instead of Eulerian approach using grid system. Therefore the terms of time derivatives in Navier-Stokes equation can be directly calculated without any n umerical diffusion or instabilities due to the fully Lagrangian treatment of fluid particles and topological failure never occur. The MPS method is applied to the numerical study on the fluid impact loads for wet-drop tests in a LNG tank, and the results are compared with experimental ones. ※Keywords: Non-linear free-surface motions(비선형 자유표면 유동), Impact loads(충격 하중), MPS method(입자 상호작용 모델), Kernel function(커넬 함수), CFD(전산유체역학), Wet-drop tests(유체 충격 시험)

The two dimensional PIV (particle image velocimetry) measurement technique is applied to water flow in a narrow cavitation tunnel. The nearly homogeneous and isotropic turbulent flows are generated by the honeycomb installed in the tunnel and visualized with a PIV technique. The velocities in the measurement plane at the tunnel centerline 184cm downward from the honeycomb were measured and calculated by an image correlation technique. The turbulent properties are evaluated and each term in the turbulent kinetic energy equation is calculated for the conditions with different internal pressures. Lowering the internal pressure gives an effect on the turbulent flow due to growing bubbles which are resolved in the water. The turbulent kinetic energy in the measurement plane is decayed much slower than those of other research results carried out with wind tunnels. With decreasing the tunnel internal pressures the turbulent intensities are increased about 1.5 times and the anisotropic tendency is also increased.

Contrary to the conventional single-point measuring devices such as LDV, pitot-tube, hot-wire, etc., it would be possible to measure instantaneously 3-D flow fields with a stereoscopic PIV system. In this paper, we present an analysis algorithm for a stereoscopic PIV system using the normalized cross-correlation (NCC) and a 3 -D calibration based reconstruction method. The evaluation method based on NCC is one of the most accurate correlation-based methods. We validated the developed algorithm through a benchmarking comparison with 3-D artificial SPIV images and calibration target images.

In this paper the development process of mobile dynamic positioning system using the offshore wireless network system is studied. During the DP operation, monitoring and ease of operation are very important. In General, the DP operator controls the DPS in the DP room with DP operator, captain and helmsman or more crew. At that time, the DP operator, captain and other crew are necessary to monitor the DPS. The DPS using ship wireless network system makes the DP operator, captain and crew possible to monitor the DPS in other place. Therefore they could operate and work at field efficiently with monitoring the DP conditions. To achieve this goal, mobile DP monitoring system using the offshore internal wireless network and its performance was studied. This mobile DPS could monitor the DP operation and control the emergency stop function. Furthermore this DPS could communicate with the tablet PC. Another Issue is maintenance. Dynamic positioning system maintenance is big issue for operation. Because it was needed very high cost and manpower. The remote maintenance could be supported by mobile dynamic positioning system. The maintenance engineer could connect to the offshore dynamic positioning system in their office.

The topic of this paper is preliminary front-end engineering and design (pre-FEED) of mining vessel (MV). The vessel will be used exclusively for mining manganese nodules located at around 5,000 meter water depth of northern east Pacific Ocean, called Clarion-Clipperton fracture zone. In this engineering process, the scope of MV's pre-FEED is confined to design basis, general arrangement (G/A), trim and stability calculation, motion analysis, down time analysis, DP capability analysis and electric load analysis (ELA).

This paper presents a methodology for identifying a set of irregular sea states for sloshing model test conditions that are most likely to produce large sloshing pressures on tank walls. To identify the critical sea states, the sloshing pseudo-response amplitude operator (RAO) is defined based on the total sloshing wave energy that is the sum of kinetic and potential energies on the free surface. The mathematical model is formulated in the frequency domain within the regime of potential flow theory. A concept of sloshing intensity is then introduced to define the sloshing severity in an irregular sea state based on the area under the sloshing wave energy response spectrum curve. The tank is expected to induce violent fluid motions for high sloshing intensity values and, as a result, its walls can experience large sloshing impact pressures. The validity of the proposed methodology is investigated by comparing the results of the numerical analysis to those of the model test for the cargo tank of a floating liquefied natural gas terminal. Favorable results in identifying the critical sea states are obtained for tested filling levels. The proposed methodology can be utilized as a pre-screening procedure for selecting relevant sea states at the initial phase of the sloshing model test and for use in the selection of sloshing flow simulation conditions.

It is widely acknowledged that mesh generation is a major bottleneck in computational fluid dynamics for non-expert users to maximize the efficiency and effectiveness of the technology. In the case of mesh generation around a ship hull, the areas around the bow and stern require special care and experience, because of their complex and delicate shape. In the present study, a hybrid mesh generation approach is proposed that only a small portion of the computational domain surrounding the bow and stern is treated separately and filled with tetrahedral cells. The remaining part of the domain, for which mesh generation is relatively easy because of geometric simplicity, is filled with hexahedral cells to ensure high quality solution there. Based on the proposed mesh generation approach, a computational analysis of POD propulsion cruise ship is performed. An improved ship hull form was found by the parametric study in terms of resistance performance. The computational results are compared with the experimental data and discussed, considering the prediction of the resistance and wave pattern of a pod propulsion cruise ship.

Still limited to knowledge about the actual phenomena so far, the comparative method has been used to assess the design load and the strength of cargo containment system for target ship designs. In the comparative approach, the sloshing load and strength of a conventional sized LNG carrier are compared with the load and strength for target LNG vessels. A 138,000 m3 LNG carrier with 4 cargo tanks is used as a reference vessel in the comparative approach according to the market practice. Recently, a Joint Development Project (JDP) on the formal assessment of the reference design sloshing load has been undertaken with four major Classification Societies using the sloshing test facility (21). During the JDP period, a “common” test procedure to make a reference load was developed. After a detailed investigation of the test data obtained using the developed procedure, the reference load was derived. The reference load will be used for the safety assessment of the NO96 containment system for DSME’s future LNG carriers or LNG related offshore floating vessels. This paper describes the test procedure and some investigated results.Copyright © 2009 by ASME

Numerous experiments with a scaled pilot facility were carried out to compare the relative bulk transfer performance of three special devices for applications to drilling systems. The pipe diameter for bulk transportation was 3 in., which corresponds to around half of the actual system dimensions. Two different pressures, 3 and 4 bar, were considered to check the relative performance under different pressure conditions at a bulk storage tank. And to make a practical estimation method of the bulk transfer rate at the early design stages of the bulk handling system, a series of experiments were conducted for real scaled bulk handing systems of two drilling vessels. The pressure drops at each pipe element as well as the bulk transfer rates were measured under different operating conditions. Using the measured results, the friction factor for each pipe element was calculated and a procedure for transfer rate estimation was developed. Compared to the measured transfer rate results for other drilling vessels, the estimated transfer rates were within a maximum 15% error bound.