bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Investigation of Steady Flow-Induced Rotary Response of Circular Cylinder With Splitter Plate
Authors: Pang Dan , Xi Huili , Zhou Zhong-bing , Tang Guo-qiang , Lu Lin 
Published: November 2019

Abstract
This article presents numerical results of flow-induced rotary oscillation of a circular cylinder with rigid splitter plate in steady flow. Different from the previous examinations with freely rotatable assembly which mainly considered linear restoring force, the rotary oscillation of the structure in this work is modelled by a Duffing oscillator with both linear and nonlinear restoring force, denoted by dimensional k and ε, respectively. Numerical simulations were carried out for various reduced velocities Ur ∈ [9 to 15] and ε ∈ [0 to 20] at a relatively low Reynolds number. Our previous investigations of a purely linear oscillator (i.e., ε = 0) show that the equilibrium position of the rotary oscillation is not parallel to the free stream as the reduced velocity exceeds a critical value, that is, bifurcation occurs. The present numerical studies suggest that, for a specific reduced velocity Ur, the increase in the nonlinear stiffness ε can eliminate the undesirable bifurcation. The numerical results also suggest that both odd and even-number lift frequency components appear for bifurcate cases, while only odd-number lift frequencies are observed for non-bifurcate cases. The dynamic mode decompositions for the wake flow corresponding to each lift frequency are presented.
The Influence of Piping Arrangement on the Response of Vibration Isolation System Under Underwater Explosion Loading
Authors: Pan Chen , Qiang Wei , Zhizhong Liu , Guan Wang 
Published: November 2019

Abstract
The response of ship equipment under non-contact underwater explosion shock loading was one of the main loadings of equipment. In order to cut down mechanical noise caused by mechanical equipment, vibration isolation measures, such as floating raft, vibration isolation, were widely used on noise mechanical equipments in acoustical stealth of ship, vibration isolation can reduce the vibration transfer to install base effectively, while the anti-shock resistance of vibration isolation and the equipment was important synchronously, as for the response of the equipment on vibration isolation, especially the actual response of the vibration isolation with piping system under shock loading. In this paper, the research on the response of vibration isolation, equipment, flexible piping and piping under underwater explosion shock loading were considered together, and the response of vibration isolation under shock load was analyzed with different piping arrangement. Found that the piping system has a significant impact on the response of the equipment under horizontal impact, but almost all equipments were assessed in experiment without considering the piping system. With the precondition of the effect of vibration isolation, a more rigid flexible pipe can be taken was benefit to the anti-shock resistance of vibration isolation.
The Investigation of a Circular Cylinder With a Detached Flexible Plate Using Immersed Smoothed Point Interpolation Method
Authors: Yan Boqian , Wang Shuangqiang , Zhang Guiyong , Xiao Qihang , Wang Peng 
Published: November 2019

Abstract
Flow control is an attractive topic in consideration of its significance associated with drag reduction or vibration suppression in fluid-structure interaction (FSI) system. A circular cylinder with a flexible plate in the wake region has been investigated numerically. An immersed smoothed point interpolation method (IS-PIM) has been employed to solve this FSI system. The splitter plate with the same length as the cylinder diameter is placed horizontally in the wake region. The drag variation of the circular cylinder and the behavior of the vorticities have been studied with regard to different locations of the detached plate. A comparative study of the rigid plate control has been presented. It shows that the effect of the flexible plate control is inferior to the rigid plate control because the flow field of the former is more complicated than the latter. When the flexible plate is far from the cylinder relatively, it would produce an opposite effect.
Study on the Design Method of Deepwater Steel Lazy Wave Riser
Authors: Wang Zhao , Qin Wei , Zhang Xiaojie , Zhao Jiannan , Bai Yong 
Published: November 2019

Abstract
The steel lazy wave riser has been used in deep-water oil and gas field development because it has good adaption to the movement of the upper platform and economic efficiency. The typical design criterion and design flow of steel lazy wave riser are introduced in this paper. The design method and the equivalence principle of distributed buoyancy modules are given. The formulas of equivalent hydrodynamic parameters are derived in this paper. The influences of distributed buoyancy modules (DBM) and the buoyancy factor on the configuration of the riser, the top tension, and the bending moment distribution are discussed and summarized. The distribution law of effective stress response along the pipe can be analyzed by dynamic analysis, and it provides reference for the global design of steel lazy wave riser.
Study on a Wave Energy Converter With Tension Leg Mooring Under Optimal Control
Authors: Umeda Jun , Taniguchi Tomoki , Fujiwara Toshifumi 
Published: November 2019

Abstract
A safety assessment for wave energy converters (WECs) in model scale is necessary before a demonstration test. WECs have various control conditions such as a maintenance and power generation mode etc. Although the safety assessment is required to carry out while considering the control conditions, the motion and load characteristics of the moored WEC to which applies various control conditions remains unclear. This study investigated the motion and load characteristics of the WEC including a mooring system when each control conditions was used. In experiments, the motion and load characteristics of the WEC without control were revealed. In the simulation, the motion and load characteristics were compared between two control methods which are the resistive loading control (RLC) and the approximate complex-conjugate control with considering the copper loss (ACL). The control methods have little effects on the surging, pitching and bending moment of the WEC. Mooring tension increased with increasing wave period when the RLC was used. When the ACL was applied, mooring tension reached the peak value near the natural period and decreased with increasing the wave period. The difference in the trends leads to that the control method maximizing mooring tension is not necessarily the same in each wave period. The select of the operating condition based on the wave period is required when the mooring tension of the WEC is assessed in the model-scale test stage.
Numerical Analysis of GBS Float-Over Deck Installation at Docking and Undocking Stages Based on a Coupled Heave-Roll-Pitch Impact Model
Authors: Chen Mingsheng , Zou Meiyan , Zhu Ling , Sun Liang 
Published: November 2019

Abstract
This paper aims to compare the impact responses in float-over installation for a gravity-based platform under two different simplifications of shock absorbers. A coupled heave-roll-pitch impact model based on the Cummins equation has been established to analyze the dynamic behaviors of installation system, in which the time-consuming convolution integral is replaced by a state-space model, resulting in a constant parameter time-domain model. In present dynamic model, the Leg Mating Units (LMUs) and the Deck Support Units (DSUs), known as shock absorbers, are simplified as vertical gap springs (compression only) with appropriate damping properties since the heave motion of the float-over installation system is the main contribution to the impact loads. Linear and nonlinear springs are assumed to evaluate how the properties of LMUs/DSUs will affect the heave impact response at docking stage and undocking stage. The influence of characteristics of LMU and DSU on the dynamic responses at docking stage is also addressed through the Poincare map and phase portraits.
Dynamic Load Inversion Method of Ship Body Based on Influence Coefficient Matrix
Authors: Ren Huilong , Feng Guoqing , Liu Hao , Hu Xuecong , Zou Jian 
Published: November 2019

Abstract
Ships sail in complex marine environments, the load is complex and uncertain. In the actual hull strength analysis, hull health monitoring and diagnosis, structural optimization design and other issues, it is very important to determine or estimate the dynamic load which applied on the hull structure. Due to the complexity and uncertainty of the working environment of the ship, many dynamic loads such as slamming loads applied on the bow of the hull are impossible or difficult to be measured directly. However, the structural response (strain, displacement, acceleration, etc.) of the corresponding part and other system characteristic parameters such as natural frequency, vibration mode, damping ratio, etc. can be obtained by installing sensors. Using the dynamic response of the structure, combined with the load identification model, the dynamic load on the hull can be calculated reversely. The time domain method and the frequency domain method are currently the most commonly used methods on load inversion. The time domain method is very suitable for the inversion identification problem of non-stationary loads and impact loads. The solution is intuitive and easy to use. In this paper, on based the time domain method, for the non-transient dynamic load, the displacement and time orthogonal function basis functions are loaded on the structure as the load function, and the response of the structure is obtained. The influence coefficient matrix is established by the response, and then the inversion load function is fitted; For transient dynamic loads such as slamming load, unit pulse load is applied on the structure to obtain the response of the structure. Then the corresponding data are filtered to overcome the ill-conditioned matrix problem. The matrix of the influence coefficient is established by the response, and the dynamic load is obtained. The two methods of dynamic load inversion based on the influence coefficient matrix are verified by numerical examples. The error is within a reasonable range, which proves that the inversion method is feasible.
Improved Model for Tubular Burst
Authors: Brechan B. , Sangesland S. , Dale S. 
Published: November 2019

Abstract
Modern casing design can reduce significant amounts of CO2 and considerable cost per well [1]. Collapse design was modernized by ISO/API Technical committee 67, Sub Committee 5, Work Group 2b (ISO/API TC67/SC5/WG2b). Modernization of burst design has so far not had the same focus and only minor changes have been made. A new burst design model has been developed to add to the collapse prediction for a complete environmental and cost effective well design tool. It is based on the theories of Lubinski [2] (1975) and presents designs using “exact von Mises ellipsis” together with the Klever and Stewart ductile rupture model [3].
This paper presents the model developed for burst design and the improvement compared to current industry practice. Inspired by the current most accurate collapse prediction model [4], the modified burst model (prototype) is the first to consider actual wall thickness to predict a more accurate internal yield of OCTG (Oil Country Tubular Goods). Investigations show that the standard 12.5% wall thickness reduction for manufacturing tolerances may be obsolete. ISO 10400 offers physical measurements and statistics of tubular properties. Following the principals by WG2b applied with the Klever & Tamano collapse prediction, there is a set of data to be used for a specific batch of tubulars or they are deducted through large quantum of measurements; ensemble Probability Density Function (PDF). The value proposed as “ensemble PDF” for wall thickness is based on more than 10 000 measurements of tubulars from 11 vendors distributed over Electrical Weld (EW) and quenched and tempered (Q&T) qualities of miscellaneous sizes and grades. The batch specific value proposed is based on more modest numbers of specimens from 4 sources but offers “minimum measured wall thickness” for all the samples. Adding to the confidence of the final design is the automated ductile burst calculation, which is one of the latest contributions to burst modeling in the industry [4] [5] [6]. It is a useful aid for the design engineer to know the potential failure mode and the limit before loss of integrity. However, burst is limited to yield because exceeding this limit may lead to loss of the pipe’s effective diameter and eventually loss of integrity. Therefore, the ductile burst prediction is proposed as a visual aid only.
Wear Performance of Mooring Chain in Wet Environment With Substitute Ocean Water
Authors: Gotoh Koji , Ueda Tetsuya , Murakami Koji , Utsunomiya Tomoaki 
Published: November 2019

Abstract
Floating wind turbine facilities installed in deep sea areas play an essential role in the promotion of green energy. One of the problems associated with the commercialization of facilities installed in the deep sea is the maintenance cost of mooring chains, because they are expensive and wear between links leads to chain breakage. Therefore, it is necessary to establish a quantitative wear evaluation method for mooring chains.
An experimental facility to reproduce the wear caused by sliding between links at the scale of an actual floating wind turbine was developed to investigate the wear performance in seawater conditions, and wear tests were conducted. Substitute ocean water was applied to the experiment instead of seawater. In addition, a procedure for nonlinear finite element analysis was improved to estimate the behaviour of wear between links. Measured stress versus strain relations of the links was considered in the finite element analysis.
The experiments and numerical analysis confirmed that the amount of wear in the substitute ocean water was less than that obtained in dry air and that the tensile force between links is an important factor for the degree of wear between links.
A Parameterization of DNV GL Storm Profile for Long-Term Analysis of Ocean Storms: Trapezoidal Storm Model
Authors: Laface Valentina , Bitner-Gregersen Elzbieta M. , Arena Felice , Romolo Alessandra 
Published: November 2019

Abstract
The paper introduces a parameterization of the DNV GL storm profile for developing an analytical model for calculations of the return period of a storm whose peak exceeds a given threshold. The DNV GL storm evolution is represented via an isosceles trapezoidal shape in which the minor base represents the storm peak duration, the major base the total storm duration and the height is half of the highest significant wave height in the actual storm. In this representation, the storm duration is not related to the storm intensity and it is fixed constant and equal to 42 hours, while the peak duration is assumed to be 6 hours. The parameterization proposed in the paper consists in expressing the peak duration as a fraction of the total storm duration allowing to investigate the effects of storm peak duration on long term estimates. The analytical solution for the return period is derived by following the classical approach of Equivalent Storm Models that is referring to the equivalent storm sequence, with the only difference that all the Trapezoidal Storm durations are identical whatever the storm intensity is. This assumption leads to significant simplification on the model development and potential employment as well. Further, a closed form solution is achieved for the return period which is also a generalization of the triangular shape. Finally, data analysis with NDBC buoys data is carried out for validating the model and elucidating analogies and differences with respect to classical Equivalent Storm approach. Results have shown that the Trapezoidal Model can be thought as a triangular one with a prudential factor on the storm peak duration which results in a reasonable overestimation of maximum expected wave height and return values.
Seismic RTDT: Real-Time Digital Twin for Boosting Performance of Seismic Operations
Authors: Sadjina Severin , Skjong Stian , Pobitzer Armin , Kyllingstad Lars T. , Fiskerstrand Roy-Jostein , Torben Sverre , Granholt Jason D. D. A. 
Published: November 2019

Abstract
Here, we present the R&D project Real-Time Digital Twin for Boosting Performance of Seismic Operations, which aims at increasing the overall operational efficiency of seismic vessels through digitisation and automation. The cornerstone in this project is the development of a real-time digital twin (RTDT) — a sophisticated mathematical model and state estimator of all the in-sea seismic equipment, augmented with real-time measurements from the actual equipment. This provides users and systems on-board the vessel with a live digital representation of the state of the equipment during operations. By combining the RTDT with state-of-the-art methods in machine learning and control theory, the project will develop new advisory and automation systems that improve the efficiency of seismic survey operations, reduce the risk of equipment damage, improve health monitoring and fault detection systems, and improve the quality of the seismic data. This will lead to less unproductive time, reduced costs, reduced fuel consumption and reduced emissions for a given operational scope.
The main focus in this paper is the presentation of today’s challenges in offshore seismic surveys, and how state-of-the-art technology can be adopted to improve various operations. We discuss how simulation technology, machine learning and live sensor measurements can be integrated in on-board decision support and automation systems, and highlight the importance of such systems for designing the complex, autonomous offshore vessels of the future. Finally, we present some early results from the project in the form of two brief case studies.
Wave Interaction With a Shallowly Submerged Step in 2D
Authors: McCauley Guy J. , Wolgamot Hugh , Draper Scott , Orszaghova Jana 
Published: November 2019

Abstract
Water wave propagation over shallowly submerged structures is of much interest in the context of submerged wave energy devices, breakwaters or barrier reefs. This work examines waves passing over a two-dimensional shallowly submerged fixed step extending to the seabed. The problem has been modelled in CFD using the open source toolbox OpenFoam utilising the Reynolds Averaged Navier-Stokes Equations. These simulations are compared to experimental work from a previous study as means of validation and extended to larger amplitude waves for a single incident wave frequency. The flow over the step is characterised and examined in the context of developing an efficient hybrid numerical model for the problem.
Numerical and Experimental Wind Tunnel Analysis of Aerodynamic Effects on a Semi-Submersible Floating Wind Turbine Response
Authors: Fontanella Alessandro , Bayati Ilmas , Taruffi Federico , Facchinetti Alan , Belloli Marco 
Published: November 2019

Abstract
This paper presents the main results of an experimental campaign about the DeepCwind semi-submersible floating offshore wind turbine (FOWT), that was carried out at Politecnico di Milano wind tunnel, adopting a hybrid hardware-in-the-loop (HIL) testing technique. Differently from previous works by the authors, this further analysis herein reported, is specifically focused on evaluating the effects of aerodynamic loads on the FOWT platform motions. In order to reproduce the FOWT response to combined wind and waves in a wind tunnel, exploiting the high-quality flow, a HIL system was used. The aerodynamic and rotor loads were reproduced by means of a wind turbine scale model operating inside the wind tunnel and were combined with numerically generated wave loads for real-time integration of the FOWT rigid-body motion equations. The resulting platform motions were imposed to the wind turbine scale model by a hydraulic actuation system. A series of HIL tests was performed to assess the rotor loads effect on the FOWT response. Free-decay tests in still water under laminar un-sheared wind were carried out to evaluate how the aerodynamic forcefield modifies the platform modes frequency and damping. Irregular wave tests for different steady winds were performed to investigate the dependency of platform motion from the wind turbine operating conditions. A FAST v8 model of the studied floating system was developed to support the analysis and numerical simulations were performed to reproduce environmental conditions equivalent to those of the experimental tests. The FAST model prediction capability is discussed against HIL wind tunnel tests results.
Increased Recovery Using Autonomous Inflow Management
Authors: Aadnøy Bernt S. , Al Furati Beder 
Published: November 2019

Abstract
Inflow control devices (ICD) were first introduced 26 years ago on the Troll field. The main purpose was to reduce water coning to delay water production. This technology is commonly used in long horizontal wells. An ICD is a passive orifice.
More recently several types of active devices have been developed. The choking effect here depends on viscosity, fluid density or pressure contrasts. They are called autonomous devices as they react on changes inside the reservoir, without signal from surface.
The main objective is to maximize oil recovery, before water production is so large that the wells are abandoned. A master thesis study conducted at the University of Stavanger together with Neptune Energy has investigated the applications of passive and autonomous inflow devices, to see which tool actually provides the highest oil recovery. The analysis was based on existing products and tools under development. Areas where a specific tool works most optimally were identified. Wells from a producing field were used as candidates for the analysis. A considerable portion of the work was to build a realistic reservoir simulator from production data. This paper will present the work and discuss the results of the study.