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CONTENTS
Volume 12, Number 3, September 2022
 


Abstract
A subsea pipeline designed across active shipping lane prones to failure against external interferences such as anchorage activities, hence risk assessment is essential. It requires quantifying the geometric probability derived from ship traffic distribution based on Automatic Identification System (AIS) data. The actual probability density function from historical vessel traffic data is ideal, as for rapid assessment, conceptual study, when the AIS data is scarce or when the local vessels traffic are not utilised with AIS. Recommended practices suggest the probability distribution is assumed as a single peak Gaussian. This study compares several fitted Gaussian distributions and Monte Carlo simulation based on actual ship traffic data in main ship direction in an active shipping lane across a subsea pipeline. The results shows that a Gaussian distribution with five peaks is required to represent the ship traffic data, providing an error of 0.23%, while a single peak Gaussian distribution and the Monte Carlo simulation with one hundred million realisation provide an error of 1.32% and 0.79% respectively. Thus, it can be concluded that the multi-peak Gaussian distribution can represent the actual ship traffic distribution in the main direction, but it is less representative for ship traffic distribution in other direction. The geometric probability is utilised in a quantitative risk assessment (QRA) for subsea pipeline against vessel anchor dropping and dragging and vessel sinking.

Key Words
automatic identification system; Gaussian Distribution; marine traffic; Monte Carlo; QRA

Address
Vincent Alvin Tanujaya: Ocean Engineering Program, Institut Teknologi Bandung, Indonesia
Ricky Lukman Tawekal and Eko Charnius Ilman: Ocean Engineering Program, Institut Teknologi Bandung, Indonesia;
Offshore Engineering Research Group, Institut Teknologi Bandung, Indonesia

Abstract
This paper adopts the Smoothed Particle Hydrodynamics (SPH) open-source code SPHinXsys to study the solitary wave interaction with coastal structures. The convergence properties of the model in terms of particle size and smoothing length are tested based on the example of solitary wave propagation in a flat-bottom wave flume. After that, the solitary wave interactions with a suspended submerged flat plate and deck with girders are studied. The wave profile and velocity field near the surface of the structures, as well as the wave forces exerted onto the structures are analyzed.

Key Words
coastal structure; solitary wave; SPH; submerged deck; wave-structure interaction

Address
Guozhen Cai, Min Luo and Zhaoheng Wei: Ocean College, Zhejiang University, Zhoushan, China
Abbas Khayyer: Department of Civil and Earth Resources Engineering, Kyoto University, Kyoto, Japan

Abstract
Herein, we report meaningful and selective review of the progress made on 'Vortex Induced Vibration (VIV)' and

Key Words
catenary riser; computer simulation model; current velocity; moored structure; semi-submersible; steel catenary riser; towing velocity; vortex induced motion; vortex induced vibration

Address
Patitapaban Sahoo and R. Sharma: Design and Simulation Laboratory, Department of Ocean Engineering, Indian Institute of Technology Madras, Chennai (TN) - 600 036, India
Vamshikrishna Domala: Post Doctoral Fellow, CADIT Laboratory, Department of Naval Architecture and Ocean Engineering,Seoul National University, Seoul - 08826, Republic of Korea

Abstract
Hydrodynamic field alteration around a cylindrical pier using a curved vane is numerically investigated. The curved vane with various angles ranged from 10 to 220 degree is placed at the upstream of the cylindrical pier. Laminar flow is adopted in order to perform the steady-state analysis. It is found that the flow separation leads to the formation of four bubbles depending on the value of the curved vane angle. Two bubbles are located in the region between the rear of the curved vane and the leading surface of the cylindrical pier, while the remaining two bubbles are located at the wake zone behind the cylindrical pier. Numerical analysis is performed to reveal the hydrodynamic field and influence of curved vane on the formation and evolution of the bubbles. It is found that the center and size of the bubble depend mainly on the value of the curved vane angle. It is observed that the flow velocity vector shows clearly the alteration in the flow velocity direction especially at the leading surface and rear surface of the curved vane owing to the occurrence of flow separation and flow dissipation along the circumference of the vane.

Key Words
bridge pier; CFD; circular vane; flow field; laminar flow

Address
Rafi M. Qasim and Tahseen A. Jabbar: Department of Fuel and Energy Eng., Southern Technical University, Basra, Iraq
Safaa H. Faisal: Department of Thermal Mechanics Eng., Southern Technical University, Basra, Iraq

Abstract
We develop in this work a new well-balanced preserving-positivity path-conservative central-upwind scheme for Saint-Venant-Exner (SVE) model. The SVE system (SVEs) under some considerations, is a nonconservative hyperbolic system of nonlinear partial differential equations. This model is widely used in coastal engineering to simulate the interaction of fluid flow with sediment beds. It is well known that SVEs requires a robust treatment of nonconservative terms. Some efficient numerical schemes have been proposed to overcome the difficulties related to these terms. However, the main drawbacks of these schemes are what follows: (i) Lack of robustness, (ii) Generation of non-physical diffusions, (iii) Presence of instabilities within numerical solutions. This collection of drawbacks weakens the efficiency of most numerical methods proposed in the literature. To overcome these drawbacks a reformulation of the central-upwind scheme for SVEs (CU-SVEs for short) in a path-conservative version is presented in this work. We first develop a finite-volume method of the first order and then extend it to the second order via the averaging essentially non oscillatory (AENO) framework. Our numerical approach is shown to be well-balanced positivity-preserving and shock-capturing. The resulting scheme could be seen as a predictor-corrector method. The accuracy and robustness of the proposed scheme are assessed through a carefully selected suite of tests.

Key Words
AENO reconstruction procedure; path-conservative central-upwind scheme; Saint-Venant-Exner model; sediment transport processes

Address
Arno Roland Ngatcha Ndengna: Laboratory of Energy Material Modeling and Method (E3M);
National Higher Polytechnic School of Douala, University of Douala, P.O.BOX 2701, Douala, Cameroon
Abdou Njifenjou: Laboratory of Energy Material Modeling and Method (E3M)
National Higher Polytechnic School of Douala, University of Douala, P.O.BOX 2701, Douala, Cameroon
National Advanced School of Engineering, University of Yaounde I, P.O. Box: 8390, Yaounde, Cameroon




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