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Kim, Hyun-Sung (Ships and Ocean Engineering / Ship and Offshore Engineering, University of Science and Technology) | Kim, Byoung Wan (Ships and Ocean Engineering / Ship and Offshore Engineering, University of Science and Technology) | Ha, Yoon-Jin (Marine Renewable Energy Research Division, Korea Research Institute of Ships and Ocean Engineering) | Park, Ji Yong (Marine Renewable Energy Research Division, Korea Research Institute of Ships and Ocean Engineering)
ABSTRACT Studies on renewable energy generation systems are increasing with the growth of problems for the existing energy resources such as fossil fuels. Among the renewable energy generation, the generation in an offshore site is in limelight due to various energy resources and vast space. Wave energy generation using the potential and kinetic energies of the wave is possible to produce large-capacity energy generation considering installation site and characteristic of a system. In this work, the structural analyses on the arm structure of oscillating type wave energy converter are conducted. This type of structure consists of a support structure, floater, and connection arm connecting the structures. And PTO (Power Take-Off) device is attached to connection arm and has the role of maintaining a generation efficiency by controlling motions of the floater. As wave-induced force from floater, and PTO damping one are applied to connection arm, the structure must have structural safety enough for environmental conditions. To perform the structural analyses on connection arm, static and dynamic analyses could be used. Static analysis method have the advantage of simple modeling and fast computation time rather than dynamic one. But this analysis method cannot deal with dynamic property of a structure in the time domain. Thus, in case that needs to consider these dynamic phenomenon, a timedomain dynamic analysis should be performed. In this study, the results of two analysis methods are compared and the application of the methods is considered. INTRODUCTION The researches and developments on various renewable energies are increasing as the growth of problems on the depletion of existing energy resources like fossil fuel and environmental pollution. To resolve a limited generation area, civil complaints, and so on, marine renewable energy generation that could use offshore sites and energy resources including wave, wind, current, and so on is being in limelight. Among these marine renewable energy generations, wave energy generation that utilizes kinetic and potential energies of wave is a proper generation for sites having a higher wave height and long wave period, and have the various generation type. There are oscillating body types, oscillating water column types, wave overtopping types as energy generation types, and a large capacity of energy generation is possible depending on a generation site, characteristic of energy converter, and so on.
Lin, Meihong (CCCC Fourth Harbor Engineering Institute Co., Ltd) | Su, Linwang (CCCC Fourth Harbor Engineering Institute Co., Ltd) | Ying, Zongquan (CCCC Fourth Harbor Engineering Institute Co., Ltd) | Wang, Xuegang (CCCC Fourth Harbor Engineering Institute Co., Ltd)
ABSTRACT A tension leg mooring system based on the three-dimensional potential flow and dynamic mooring theories is proposed to improve the hydrodynamic performance of a submerged platform. Frequency-domain and time-domain analyses are conducted using ANSYS AQWA while considering the shallow water effect, the draft of the submerged platform, and the mooring line and construction-related parameters. The response amplitude operators (RAOs) of the submerged platform are obtained. As the platform is submerged into the water, the heave and roll responses and their natural motion periods decrease, improving the wave stability and adaptability of the platform. The dynamic responses of the submerged platform during the working condition are analyzed, focusing on the motion of the platform at different locations. Time-domain simulations of the tension leg mooring system are conducted, considering the coupling effect of the heave and roll. The maximum heave values are obtained for different wind, wave, and current conditions to reduce the heave and roll motion of the platform. When the leveling machine is located at the corner of the platform, the limit conditions of the environmental parameters must be considered to meet the leveling accuracy requirements. Parameter optimization is conducted for the draft of the platform and the pretension force of the tension leg under different conditions to improve the leveling accuracy. The optimized mooring has a leveling accuracy of ± 40 mm. This study provides an approach to determine the parameters of the tension leg mooring system for the design of shallow water construction platforms for water transportation engineering. INTRODUCTION Immersed tunnel engineering is used in road construction to cross rivers and straits. It has been used since the beginning of the last century and is widely applied (Lunniss and Baber 2013). Due to the advantages of a shallow buried depth, low foundation requirements, and a short construction period, immersed tunnel design has been used by many developed countries globally. This technology has high design and construction requirements. The foundation is a crucial aspect of immersed tunnel construction because it affects the deformation stability during construction and operation. An increasing number of tunnels have been constructed using the pre-bedding method (Hu, Xie et al. 2015). This method was used in combination with a specially designed ship to install the foundations of the Busan-Geoje Link (Janssen, de Haas et al. 2006) and Hong Kong-Zhuhai-Macao Link (Hussain, Wong et al. 2011). Leveling ships are designed to reduce the impact of the wind, waves, and current on the leveling accuracy of the foundation and are used for three reasons: installing the pile legs, lifting the leveling structure above the water surface during construction, and reducing the impact of waves (Hu, Xie et al. 2015). The feeding structure and leveling structure are separated, and leveling is achieved by the underwater leveling equipment to reduce the influence of waves and improve the leveling accuracy. Leveling platforms with a semi-submersible hull are required to reduce the influence of waves.
ABSTRACT The main objective is to investigate the possibility that machine learning can be used in the real-time simulation of ship motion. A short-term prediction of seakeeping and maneuvering is strongly required for the navigation process. However, accurate and instant prediction remains still challenging. In the present study, a physics-based machine learning model has been proposed. Two physical attributes that define the ship motion have been learned by applying a machine learning model suitable for each character and integrating them. The integrated machine learning model has successfully learned the motion characteristics of the vessel. INTRODUCTION An autonomous ship has been a contentious issue for the shipbuilding industry. A short-term prediction of seakeeping and maneuvering in the real-time simulation is strongly required for the navigation process to improve safety and efficiency. However, accurate prediction remains still challenging owing to the expensive computation cost of the numerical simulation for the ship motion (Weymouth et al., 2013). Existing methods are difficult to respond immediately to the provided information during a voyage. Real-time prediction of ship motions has been studied based on linear hydrodynamic equations, time series prediction models, and machine learning models (Ferrandis, et al., 2019; Liu et al., 2020). The prediction of the linear hydrodynamic equation is difficult to estimate the ship hydrodynamic coefficients that are time-varying in severe environmental conditions. The prediction of the time series models also faces difficulties in nonlinear ship motion modeling. Several alternate methods based on the auto-correlation function proposed by Nielsen et al. (2018) and the auto-regressive moving average by Yumori (1981) show better performance than the classical approaches while their accuracy and variability are still controversial. Machine learning has been recently used for ship motion prediction motivated by the effort to apply machine learning to various hydrodynamic problems (Chen and Chen, 1993). Ferrandis et al. (2021) and D’Agostino et al. (2021) show that the recurrent neural network (RNN) model can predict the motion time signals based on the CFD simulation by comparing their time signals. Li et al. (2017) used the collected sensor data on a vessel to show the feasibility of the neural network model to predict ship motion under the mild sea states. Liu et al. (2020) studied the required motion records for the recurrent neural network model to consider the memory effects. Sun et al. (2021) provide a hybrid model of the recurrent neural network and Gaussian Process Regression to describe the reliability of the prediction. It has been shown that the database could help to provide nonlinear characteristics of the vessel (Xu, et al., 2021). Although many previous studies have shown the possibility that machine learning can be a solution for real-time ship motion prediction, it is hard to confirm that those machine learning models have fully learned the physical motion characteristics of the vessel.
ABSTRACT Currently, the number of the fishing vessel in the world is very large. The studies related to cargo ships, tankers or large ships are more carried out than fishing vessels. Moreover, the fishing vessel operates for a long time at one position in the sea for exploiting fish. Thus, it is crucial to observe the effect of the irregular wave on the ship's motion. The purpose of this study is to investigate the ship motion in the irregular waves by performing the model test. The model test of the Russian trawler was performed in the square wave tank at Changwon National University in various wave directions at zero speed. An Optical-based system was used to measure the six degrees of freedom (6DOF) motion of the ship. Firstly, the motion responses of the ship in the irregular waves in various wave directions are investigated. The time histories of the ship motion response are transferred to the frequency domain from the time domain. Secondly, the effect of the wave frequency component on the ship motion responses is analyzed. The natural frequency of the ship and peak of the wave frequency have strong responses on the motion spectrum in irregular waves. Finally, the effect of the wave direction on the ship motion spectrum is discussed. INTRODUCTION Nowadays, the number of fishing vessels increase rapidly due to increased fishing demand. In addition, the fishing vessel operates for a long time at one position in the sea for drop and drag the net. The ship motions are affected by environmental conditions i.e. wind, wave, current… However, the wave is the most effect on the ship motion. Therefore, it is necessary to predict the ship motion in sea conditions. In the part, it has much research studied the ship motion in irregular waves. Shen, Ye and Wan (2014) predicted the ship motion response in irregular waves using URANS simulations. In their study, the ship motion responses in the irregular waves were compared by using the numerical method, experimental method and strip method. Jiao and Huang (2020) investigated the seakeeping performance of the S175 container ship by using CFD simulation. The results of ship motion responses in regular waves and cross waves were compared. This study discovered that the transverse and heave motion response in the cross waves can be large from those in the regular waves. Im and Lee (2021) investigated the effect of tonnage on the motion response of fishing vessel in regular waves. The ship motion responses were performed on different sizes of fishing vessel by using numerical method. Mainum, Yaakob, Kamal and Wei (2006) estimated the motion spectral of the Malaysian fishing vessel using operation data. The ship motion and wave elevation were measured by vessel motion monitoring system and the wave buoy. Hence, the motion spectral and response amplitude operator were obtained. Nurhasanah, Santoso, Romadhoni and Nasutioni (2020) predicted the response amplitude operator and spectral response in heave, roll and pitch motion by using strip theory calculation (Maxsurf software). The effect of rounded hull, double chine and multi chine on ship motion responses were investigated. Sivabalan and Sivakumar (2020) calculated the ship motion responses of the fishing vessel in various wave directions. The ship motion response were carried out in regular waves and irregular waves using potential flow (MOSES software). Lee, Choi, Ahn, Kim, Kim and Shighehiro (2015) studied the ship motion responses in irregular waves. The ship motion responses in irregular waves were obtained based on strip method in regular waves and using linear superposition theory to estimate the energy spectrum. Ghamari, Greco, Faltinsen and Lugni (2020) investigated the heave, roll and pitch motion of a fishing vessel by performing numerical method and experimental method with and without forward speed in regular waves. The results of the ship motion response of numerical and experimental method were compared.
Shell has restarted the shipment of LNG from its multibillion-dollar Prelude FLNG facility off northwest Australia after being sidelined since 2 December 2021 due to significant power issues. The first cargo since late last year left the project site on 10 April, according to the company. Its restarted operations should provide some relief to term off-takers in South Korea and Japan, Rystad Energy wrote in a market note. "Spot buying interest from South Asia has been very robust over the past few days with several cargos being awarded around the $30 mark." The Prelude FLNG facility suffered a fire and lost power in December.
Abstract High pressure, high temperature (HPHT) corrosion in sour conditions is a major concern in oil and gas production. Here, the selection of corrosion inhibitor is a significant challenge in oil and gas industry. This paper presents the results using HPHT Hastelloy RC autoclave for the performance study of corrosion inhibitor with high H2S/CO2 environments and high shear stress of 25 Pa in 80 % water cut. The sour corrosion testing conditions were the combination of 16.8 bar H2S concentration and 12 bar CO2 concentration with the temperature of 121 °C. Triplicate API 5L X65 weight-loss coupons were used in the test. Some important standard tests (e.g. thermal stability, emulsification tendency, foaming tendency, and solubility) with material compatibility test (Alloy 825) were also presented. The test results show that the average corrosion rates using weight-loss coupons are less than 0.1 mm/yr with low corrosion inhibitor concentration. No pitting corrosion was observed. Introduction As traditional reserves deplete onshore and offshore, the oil industry is moving into increasingly deeper waters and harsh environments in the pursuit of hydrocarbons. As the industry drills deeper, the challenges that face infrastructure increase markedly with the longstanding issues of corrosion. One of the major challenges to corrosion management is the extreme pressure and temperature. In addition to these operating conditions, a sour condition makes even more challenging to manage the fluid handling equipment such as well production tubing and flowlines that are carrying the produced fluid. Sour fields consist of approximately one-third of oil and gas fields globally and this sour condition leads to the localized corrosion that causes a threat to the integrity of mild steel pipelines and equipment in the oil and gas industry. In oil field production, carbon steel is the most commonly used material due to its relatively low capital cost coupled with good mechanical properties. However, carbon steel is susceptible to corrosion in the oil field operating environment. In a sour environment, the most common form of corrosion damage found on carbon steel is localized pitting corrosion.
In this study, wind and waves are studied for offshore wind power at the Donghae gas field in South Korea. Two kinds of data sets are compared: one set contains 39-year National Oceanic and Atmospheric Administration (NOAA) hindcast data and the other 3-year buoy-measured data obtained by the Korea Meteorological Administration in South Korea (KMA). The NOAA and KMA data sets for different reference periods, recording intervals, and measuring altitudes are compared. Furthermore, data from 2.7-year (2 years and 8 months) in situ measured waves at the end of a jetty and wind at a height of 100 m in the shipyard of Samsung Heavy Industries Co., Ltd. (hereafter referred to as the SHI yard) are used in advance to investigate the feasibility of these conversions. This study proposes the conversion relations between different conditions for wind and waves. For waves, an uncertainty correction factor with different reference periods is suggested to convert and compare the significant wave heights for the data sets in the Donghae gas field and the SHI yard. For wind, the traditional Norwegian Petroleum Directorate (NPD) wind profile optimized for open sea as recommended by DNV GL is directly used to convert the wind speed in the Donghae gas field with different reference periods. However, because of significantly complex terrain conditions in the SHI yard, a newly modified NPD wind profile is suggested to adjust the turbulence intensity. Then it is applied to convert and compare the wind speed in the SHI yard. This modified NPD wind profile shows a good match, but it requires further study because of the limited data length used in this study. Introduction There is a growing interest in renewable energy around the world to reduce gas emissions from the combustion of fossil fuels. The Korean government has also developed offshore wind power as an alternative. Reliable design environment conditions such as wind and waves are highly desired in applications of offshore structures or floating offshore wind turbines (FOWTs). Unfortunately, there are several different reference periods of duration of wind and waves with different recording intervals, including idling times. For example, the National Oceanic and Atmospheric Administration (NOAA) hindcast wave data typically provide 3 hr-Hs and 10 m-1 hr-Vw every 3 hr as an offshore standard, where 3 hr-Hs denotes significant wave height (Hs) in a 3 hr reference period, and 10 m-1 hr-Vw denotes the 1 hr average wind speed (Vw) at an average water level of 10 m in a 1 hr reference period. Meanwhile, the Korea Meteorological Administration (KMA) in South Korea provides measurement data recorded by an offshore wave buoy composed of 17 min-Hs for wave heights and 5 m-10 min-Vw for wind speeds. Their recording interval is 30 min or 1 hr. Waves are sampled at 1 Hz. Every one of the 1,024 samples is analyzed by Fourier transform to get spectral quantities of Hs and the spectral peak wave period in seconds (Tp). The height of an anemometer on the buoy is about 5 m from its draft. Therefore, the conversion relations of magnitudes of wind and waves with different reference periods should be considered to compare them with different sources of data sets of wind and waves.
Communication and prediction are symmetrical. Communication, in effect, is prediction about what has happened. And prediction is communication about what is going to happen. Few industries contain as many phases, steps, and levels of interface between the start and end product as the oil and gas industry—field, office, offshore, plant, subsea, downhole, not to mention the disciplinary, functional, managerial, logistics handovers, and boundaries that exist. It therefore is hardly surprising that communication, in all its varied forms, is at the very heart of our business. The papers selected this month demonstrate how improved communication can deliver the prediction required for a variety of reasons, including safety, efficiency, and informational purposes. The application of new and exciting ways of working, partially accelerated by recent events, is leading to breakthrough improvements on all levels. Real-time processing, improved visualization, and predictive and machine-learning methods, as well as improvements in all forms of data communication, are all contributing to incremental enhancements across the board. This month, I encourage the reader to review the selected articles and determine where and how the communication and prediction are occurring and what they are delivering. Then perhaps consider performing an exercise wherein your own day-to-day roles—your own areas of communication, interfacing, and cooperation—are reviewed to see what enhancements you can make as an individual. You may be pleasantly surprised that some simple tweaks to your communication style, frequency, and format can deliver quick wins. In an era of remote working for many individuals, it is an exercise that has some value. Recommended additional reading at OnePetro: www.onepetro.org. OTC 30184 - Augmented Machine-Learning Approach of Rate-of-Penetration Prediction for North Sea Oil Field by Youngjun Hong, Seoul National University, et al. OTC 31278 - A Digital Twin for Real-Time Drilling Hydraulics Simulation Using a Hybrid Approach of Physics and Machine Learning by Prasanna Amur Varadarajan, Schlumberger, et al. OTC 31092 - Integrated Underreamer Technology With Real-Time Communication Helped Eliminate Rathole in Exploratory Operation Offshore Nigeria by Raphael Chidiogo Ozioko, Baker Hughes, et al.
Using a small-aperture circular array deployed in the urban center of Busan, Korea we report the results on (a) characteristics of urban vibrational noise and (b) the geological and geotechnical characteristics of shallow sedimentary formations. With focusing on urban studies the frequency band of the ambient noise is well above 1 Hz. The analysis results show that the anthropogenic origin from city center of Pusan is the main cause of the observed ambient noise energy. Polarity and amplitude of noise interferometry show that ambient noise is dominated shown as vibrations and waves propagating horizontally. Other characterization parameters include shear strain in the horizontal plane and the rotation vector of 3 components. The analysis results show that the alluvial sediment is about 100 m at the site, with a possible clay-sand interface at 40-50 meters. Anisotropy analysis shows the principal direction of NW-SE, consistent with the Nakdong River Delta history.
The vessels will be constructed at Daewoo Shipbuilding & Marine Engineering Co. Ltd. headquartered in South Korea. Slated for delivery in 2024, the 174,000 m3 membrane-type carriers will be equipped with the MAN Energy Solutions engines, which offer improvements in fuel efficiency. It also adopts a new design that generates less boiloff gas from cargo tanks using a reliquefaction unit on board, and a shaft generator system that uses the rotating propeller shaft for power generation. MOL said the vessels are more environmentally friendly than current LNG carriers. A JPT report, "Russian LNG Aims High, Leveraging Big Reserves and Logistical Advantages," provides an overview of the investment Russia is pouring into LNG projects, including the country's largest natural gas producer, Novatek.