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CONTENTS
Volume 13, Number 1, March 2023
 

Abstract
An iterative focused wave generation method is developed and implemented in a local analytic based Navier-Stokes solver. This wave generation method is designed to reproduce the target focused wave by matching the target amplitude spectrum and phase angle. A 4-waves decomposition scheme is utilized to obtain the linearised component of the output wave. A model test studying the interaction between different focused waves and a fixed cylinder is selected as the target for the wave generation approach. The numerical wave elevations and dynamic pressure on the cylinder are compared with the experimental measurement and other state-of-the-art numerical methods' results. The overall results prove that the iterative adjustment method is able to optimize the focused wave generated by a CFD approach

Key Words
computational fluid dynamics (CFD); extreme waves; focused wave generation

Address
Haoyuan Gu: Zachry Department of Civil and Environmental Engineering, Texas A&M University, College Station, TX, USA
Hamn-Ching Chen: Zachry Department of Civil & Environmental Engineering and Ocean Engineering, Texas A&M University, College Station, TX, USA

Abstract
Decarbonization and energy transition can be considered as a main concern even for the oil industry. One of the initiatives to reduce emissions under studies considers the use of renewable energy as a complimentary supply of electric energy of the production platforms. Wind energy has a higher TRL (Technology Readiness Level) than other types of energy converters and has been considered in these studies. However, other types of renewable energy have potential to be used and hybrid concepts considering wind platforms can help to push the technological development of other types of energy converters and improve their efficiency. In this article, a preliminary hydrodynamic assessment of a new concept of hybrid wind and wave energy conversion platform was performed, in order to evaluate the potential of wave power extraction. A multiple OWCs (Oscillating Water Column) WEC (Wave Energy Converter) design was adopted for the analysis and some simplifications were adopted to permit using a frequency domain approach to evaluate the mean wave power estimation for the location. Other strategies were used in the OWC design to create resonance in the sea energy range to try to maximize the potential power to be extracted, with good results.

Key Words
energy; hydrodynamics; wave; WEC; wind

Address
Allan C de Oliveira:Petrobras R&D Center, Petrobras, Av Horacio de Macedo, 950, Cidade Universitaria, Brazil

Abstract
In this study, the SCFs in tubular T-joints stiffened with external ring under axial load are studied and discussed. After verification of the present numerical model with the results of several available experimental tests, 156 FE models were generated and analyzed to parametrically evaluate the effect of the joint geometry and the ring geometry on the SCFs. Results indicated that the SCF of the stiffened T-joints at crown point can be down to 24% of the SCF of the corresponding un-reinforced joint at the same point. Also, the effect of the ring on the SCF at saddle point is more remarkable than the effect of the ring on the SCF at crown point. Moreover, against un-reinforced joints under axial load, the SCF at saddle point of the stiffened joint is smaller than the SCF at crown point of that stiffened joint. The ring results in the redistribution of stresses in the ring and metal substrate. Also, the effect of the ring thickness on the decrease of the SCFs is slight and can be ignored. In final step, the geometric parameters affecting the SCFs of the stiffened T-joints are analyzed by multiple nonlinear regression analyses. An accurate formula is proposed for determining the SCFs.

Key Words
axial load; offshore structures; parametric equation; ring; SCF; T-joi

Address
Hossein Nassiraei: Department of Civil Engineering, Faculty of Engineering, University of Guilan, Guilan, Iran
Pooya Rezadoost: Faculty of Civil Engineering, K.N. Toosi University of Technology, Tehran, Iran

Abstract
In the present study, the total hydrodynamic pressure exerted by the fluid on walls of rectangular tanks due to horizontal excitations of different frequencies, is investigated by pressure based finite element method. Fluid within the tanks is invisid, compressible and its motion is considered to be irrotational and it is simulated by two dimensional eight-node isoparametric. The walls of the tanks are assumed to be rigid. The total hydrodynamic pressure increases with the increase of exciting frequency and has maximum value when the exciting frequency is equal to the fundamental frequency. However, the hydrodynamic pressure has decreasing trend for the frequency greater than the fundamental frequency. Hydrodynamic pressure at the free surface is independent to the height of fluid. However, the pressure at base and mid height of vertical wall depends on height of fluid. At these two locations, the hydrodynamic pressure decreases with the increase of fluid depth. The depth of undisturbed fluid near the base increases with the increase of depth of fluid when it is excited with fundamental frequency of fluid. The sloshing of fluid with in the tank increases with the increase of exciting frequency and has maximum value when the exciting frequency is equal to the fundamental frequency of liquid. However, this vertical displacement is quite less when the exciting frequency is greater than the fundamental frequency.

Key Words
compressibility of water; finite element method; fundamental frequency; sloshed displacement; total hydrodynamic pressure

Address
Kalyan Kumar Mandal: Department of Civil Engineering, Jadavpur University, India

Abstract
An onshore dismantling yard is an important part in the supply chain of the offshore oil and gas decommissioning industry. However, despite having more than 500 offshore structures to be decommissioned in the Southeast Asia region, there are a very limited number of well-equipped dismantling yards to fully execute the onshore dismantling. Recent investigations discovered that shipbuilding and offshore structure fabrication yards are still potential options for upgrades to include dismantling. Despite the huge potential opportunities from upgrading to dismantling, research studies on this area are relatively scarce, and most past studies mainly focused on the North Sea region. To date, the potential opportunities of Southeast Asia and Malaysia yards to develop onshore dismantling capability are still unclear. The aim of this study is to identify the criteria to develop a technical preparedness checklist to evaluate an onshore dismantling yard; consequently, this will assist with assessing and bridging the gaps and identify the opportunity of developing an onshore dismantling yard in Southeast Asia region. Requirements for onshore dismantling and related rules and regulations have been investigated and summarized in the form of checklist. Findings from this study can help local oil and gas operators to pursue more local solutions and resilient supply chain performance.

Key Words
abandonment; decommissioning; offshore structures; onshore dismantling; Southeast Asia

Address
Jing-Shuo Leow and Jing-Shun Leow: Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, Johor Bahru 81310, Malaysia
Hooi-Siang Kang and Omar Yaakob: Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, Johor Bahru 81310, Malaysia;
Marine Technology Centre, Institute for Vehicle and Systems and Engineering, Universiti Teknologi Malaysia, Johor Bahru 81310, Malaysia
Wonsiri Punurai: Department of Civil and Environmental Engineering, Faculty of Engineering, Mahidol University, Thailand
Sari Amelia: Institut Teknologi Bandung, Jl. Ganesa No.10, Lb. Siliwangi, Kecamatan Coblong, Kota Bandung,
Jawa Barat 40132, Indonesia
Huyen Thi Le: PetroVietnam University, 762 Cach Mang Thang Tam Street, Long Toan Ward, Ba Ria City, Ba Ria-Vung Tau Province 790000, Vietnam


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