bluuebunny/crossref_metadata_2025 huggingface dataset:
Transversal Vibration Analysis of Vehicle Track System
Authors: Wang Pingxin , Rui Xiaoting , Zhang Jianshu , Yu Hailong
Published: November 2019

The track is mainly composed of track shoes, track pins and rubber bushing elements. In order to suppress the transversal vibration of the upper track during the smooth running process of the tracked vehicle, it is necessary to study the important factors affecting the frequency characteristics of the kinematic chain and their interaction. Unlike the conventional chain drive system, the track in the natural state has a bending rigidity due to the action of the rubber bushing. Based on the dynamic theory of axially moving beam, the differential equation of transversal vibration of a beam element is established. The entire upper track is assumed to be a continuous multi-span axially moving Euler-Bernoulli beam with an axial tension. Based on the Transfer Matrix Method of Multibody System, the transfer equation is obtained. According to the boundary conditions, the natural frequency of the system is solved. The correctness of the beam model hypothesis is verified by experiments. The results show that the first-order natural frequency of the upper track increases with the increase of the tension and the decrease of the vehicle speed. Through frequency analysis, the main excitation source for the transversal vibration of the track is the polygon effect produced by the meshing of the track and the sprocket. This study provides a theoretical basis for the vibration analysis and stability control of the upper track on the tracked vehicle.
Investigating Information: A Qualitative Analysis of Expert Designers’ Information Representation and Structuring Behaviors
Authors: Damen Nicole B. , Toh Christine A.
Published: November 2019

Information organization and utilization are integral to the design and development of creative ideas. However, navigating this often complex information space can be challenging, even for experienced designers. Therefore, deep analysis of how expert designers utilize and organize information is needed to provide qualitative insights into their information organization strategies. To address this, four professionals in the software design and development field were recruited for individual 3-hour design sessions. They were asked to generate ideas for a design challenge (reducing distraction-based pedestrian accidents) using information sheets specifically developed to contain different types of information, as identified by prior work. Results reveal individual differences in information approach and categorization, although these were motivated by similar underlying patterns of evaluating the relevance of information for its ability to inform the project constraints, resources or (user) requirements. Designer experience and use of design processes and knowledge transfer tools enhanced their ability to turn information into insights.
Lightweight Long-Reach 5-DOF Robot Arm for Farm Application
Authors: Zhang QianWei , Fotouhi Reza , Cote Joshua , Pour Majid Khak
Published: November 2019

Crop monitoring is frequently used by crop scientists to observe growth of plants and to relate plants phenotypes to their genotypes. Instead of traditional crop monitoring, which is labor intensive, high-throughput plant phenotyping (HTP) platforms using ground-based vehicle have several advantages over manual methods. Existing HTP platforms with robot arms has limited reach and payload, and they are sometimes not appropriate for monitoring large fields. In this research, a 5-DOF robot arm is developed and analyzed for monitoring several crops growth. This robot arm is a hybrid of both prismatic and rotational joints. This new mobile manipulator is light, has a compact structure, suitable for plant phenotyping, and doesn’t exist commercially. To investigate the performance of the robot arm, kinematics and dynamics analyses using Newton-Euler iterative method and MATLAB simulations are performed. Results matched with each other very well.
Exploiting Origami Shape Reconfiguration in Noise Control Applications
Authors: Fang Hongbin , Yu Xiang , Cheng Li
Published: November 2019

Noise has been recognized as a serious health hazard in modern society. Among various noise reduction ways, control of the transmission path from the source to the receiver is a feasible option for both existing and new facilities. More specifically, acoustic barriers and reactive or dissipative mufflers are two characteristic measures. The performance of a noise barrier or a muffler always depends on geometries. For the former, the key geometry is the barrier height; for the latter, the key geometries are the shape and size of the expansion chamber or resonance tubes. Conventional barriers and mufflers are scarcely capable of altering their key geometries, and hence, their performance based on requirements, nor possessing adequate versatility to adapt to variable noise conditions. In this research, we show that origami, the ancient art of paper folding, provides abundant inspiration for developing reconfigurable noise controlling devices, exemplified by Miura-ori noise barrier, modular-origami silencer, Miura-ori quarter-wavelength tube, and origami-ball expansion chamber. We show that the shape and characteristic geometries of these devices can be significantly altered via folding with a single degree of freedom, which can be exploited for tuning their attenuation performances. Then the modular-origami silencer is employed to exemplify the folding-induced advantages. Finite element studies reveal that folding could reconfigure the silencer such that the sound attenuation bandwidth can be effectively tuned. In addition, by incorporating multiple origami layers in a silencer and by programming their geometries, prescribed noise control requirement can be achieved. Overall, with the modular-origami silencer as a proof-of-concept example, we demonstrate that origami could inspire new innovation in designing noise control devices with the long-desired shape re-configurability and acoustic tunability.
Optimizing Topology and Fiber Orientations With Minimum Length Scale Control in Laminated Composites
Authors: Luo Chuan , Guest James K.
Published: November 2019

Discrete Material Optimization (DMO) has proven to be an effective framework for optimizing the orientation of orthotropic laminate composite panels across a structural design domain. The typical design problem is one of maximizing stiffness by assigning a fiber orientation to each subdomain, where the orientation must be selected from a set of discrete magnitudes (e.g., 0°, ±45°, 90°). The DMO approach converts this discrete problem into a continuous formulation where a design variable is introduced for each candidate orientation. Local constraints and SIMP style penalization are then used to ensure each subdomain is assigned a single orientation in the final solution. The subdomain over which orientation is constant is typically defined as a finite element, ultimately leading to complex orientation layouts that may be difficult to manufacture. Recent literature has introduced threshold projections, originally developed for density-based topology optimization, into the DMO approach in order to influence the manufacturability of solutions. This work takes this idea one step further and utilizes the Heaviside Projection Method within DMO to provide formal control over the minimum length scale of structural features, holes, and patches of uniform orientation. The proposed approach is demonstrated on benchmark maximum stiffness design problems in terms of objective function, solution discreteness, and manufacturability. Numerical results suggest that projection-based methods can play an important role in controlling the manufacturability of optimized material distributions in optimized design and that solutions are near-discrete with performance properties comparable to designs without manufacturing considerations.
Machine Learning for Evaluating the Social Impact of Engineered Products: A Framework
Authors: Stringham Bryan J. , Smith Daniel O. , Mattson Christopher A. , Dahlin Eric C.
Published: November 2019

Evaluating the social impact indicators of engineered products is crucial to better understanding how products affect individuals’ lives and discover how to design for positive social impact. Most existing methods for evaluating social impact indicators require direct human interaction with users of a product, such as one-on-one interviews. These interactions produce high-fidelity data that are rich in information but provide only a single snapshot in time of the product’s impacts and are less frequently collected due to the significant human resources and cost associated with obtaining them. A framework is proposed that describes how low-fidelity data passively obtained using remote sensors, satellites, and digital technology can be collected and correlated with high-fidelity, low-frequency data using machine learning. Using this framework provides an inexpensive way to continuously monitor the social impact indicators of products by augmenting high-fidelity, low-frequency data with low-fidelity, continuously-collected data using machine learning. We illustrate an application of this framework by demonstrating how it can be used to examine the gender-related social impact indicators of water pumps in Uganda. The provided example uses a deep learning model to correlate pump handle movement (measured via an integrated motion unit) with user type (man, woman, or child) of 1,200 hand pump users.
An Association Rule Approach for Identifying Physical System-User Interactions and Potential Human Errors Using a Design Repository
Authors: Soria Zurita Nicolás F. , Tensa Melissa Anne , Ferrero Vincenzo , Stone Robert B. , DuPont Bryony , Demirel H. Onan , Tumer Irem Y.
Published: November 2019

During the design process, designers must satisfy customer needs while adequately developing engineering objectives. Among these engineering objectives, human considerations such as user interactions, safety, and comfort are indispensable during the design process. Nevertheless, traditional design engineering methodologies have significant limitations incorporating and understanding physical user interactions during early design phases. For example, Human Factors methods use checklists and guidelines applied to virtual or physical prototypes at later design stages to evaluate the concept. As a result, designers struggle to identify design deficiencies and potential failure modes caused by user-system interactions without relying on the use of detailed and costly prototypes. The Function-Human Error Design Method (FHEDM) is a novel approach to assess physical interactions during the early design stage using a functional basis approach. By applying FHEDM, designers can identify user interactions required to complete the functions of the system and to distinguish failure modes associated with such interactions, by establishing user-system associations using the information of the functional model. In this paper, we explore the use of data mining techniques to develop relationships between component, functions, flows and user interactions. We extract design information about components, functions, flows, and user interactions from a set of distinct coffee makers found in the Design Repository to build associations rules. Later, using a functional model of an electric kettle, we compared the functions, flows, and user interactions associations generated from data mining against the associations created by the authors, using the FHEDM. The results show notable similarities between the associations built from data mining and the FHEDM. We are suggesting that design information from a rich dataset can be used to extract association rules between functions, flows, components, and user interactions. This work will contribute to the design community by automating the identification of user interactions from a functional model.
Overview of Remote Sensing Efforts at University of Maryland Eastern Shore
Authors: Nagchaudhuri Abhijit , Ford Travis , Hartman Christopher
Published: November 2019

Remote sensing and aerial imaging efforts at University of Maryland Eastern Shore (UMES) have been ongoing for over a decade. It was initiated with the UMESAIR (Undergraduate Multidisciplinary Earth Science Airborne Instrumentation Research) project in early part of the century as an exploratory experiential learning project as means to foster collaboration and provide exposure to science and engineering students to scientists and engineers at NASA’s Wallops Flight Facility which is within 50 miles of campus. Subsequently, with significant support from USDA’s National Institute of Food and Agriculture (NIFA) the remote sensing endeavors have been integrated with the smart farming and precision agriculture efforts closely aligned with the land grant mission of UMES and the regional emphasis in the Delmarva Peninsula. Maryland Space Grant Consortium (MDSGC) have also supported a synergistic project titled Aerial Imaging and Remote Sensing for Precision Agriculture and Environmental Stewardship (AIRSPACES) on an annual basis which has allowed continued involvement of multidisciplinary undergraduate students from the STEM fields to remain involved with the efforts.
Design of a Human-Powered Roll Stabilization Attachment for Utilitarian Two-Wheeled Vehicles
Authors: Diaz Lankenau Guillermo F. , Daigle Lea , Ihns Samuel H. , Koch Eric , Saadi Jana , Tornes Patrick , Wu Jessica M. , Winter Amos G.
Published: November 2019

This paper describes the motivation and development of a human-powered roll stabilization attachment for utilitarian two-wheeled vehicles. The proposed design has been built and tested by the authors in both on- and off-road conditions. It provides balance by providing a rolling platform underneath the two-wheeled vehicle (motorcycle) for the user to push against with their feet. This platform is placed under the driver’s sitting position and is towed from a three degree-of-freedom joint behind the front axle (i.e. one of the implementations uses a ball hitch joint). Fifty eight percent of the world’s motorcycles are in Asia Pacific, and Southern and Eastern Asia. In most of those countries, motorcycles greatly outnumber cars and many of these motorcycles function as utility vehicles. The uses of motorcycles include transportation of goods on the bike frame, transportation of goods on a trailer, and even pulling agricultural implements in farms. If no modifications are made to the motorcycle, at slow speeds operators of motorcycles must drag their feet on the ground and lightly push upwards as needed to retain balance. Attaching conventional outrigger wheels, similar to a motorcycle side-car, can negate some of the advantages of motorcycles that users value by: (A) preventing leaning into turns when rigid outriggers arms are used, (B) significantly increasing complexity and mass when outrigger arms mounted on suspension systems are used, and (C) increasing the vehicle’s width such that it can no longer travel between car lanes or between rows of growing crop. An additional design consideration for balancing motorcycles is the user’s need for quick conversion between a statically balanced vehicle and a vehicle can lean dynamically in turns, for example for someone who wishes to operate a motorcycle on farms but also travel quickly between agricultural fields. This conversion convenience is affected not only by the ease of attaching and detaching the balancing system but also by the ability to comfortably carry on the balancing system on the motorcycle even when it is not being used, such that it can be deployed when it is needed. This paper describes a design for a human-powered roll stabilization attachment that address these concerns and other identified user needs. It also provides with general equations to design similar human-powered roll stabilization systems for motorcycles.
Anisotropic Multicomponent Topology Optimization for Additive Manufacturing With Build Orientation Design and Stress-Constrained Interfaces
Authors: Zhou Yuqing , Nomura Tsuyoshi , Saitou Kazuhiro
Published: November 2019

This paper presents a multicomponent topology optimization method for designing structures assembled from additively-manufactured components, considering anisotropic material behavior for each component due to its build orientation and distinct material behavior and stress constraint at component interfaces (i.e., joints). Based upon the multicomponent topology optimization (MTO) framework, the simultaneous optimization of structural topology, its partitioning, and the build orientations of each component is achieved that maximizes an assembly-level structural stiffness performance, subject to a maximum stress constraint at component interfaces. The build orientations of each component are modeled by its orientation tensor that avoids numerical instability often experienced by the angular representation. A new joint model is introduced at component interfaces, which enables identifying the interface region, assigning a distinct tensor for the region, and imposing a maximum stress constraint in the region during optimization. Both 2D and 3D numerical examples are presented to illustrate the effect of the build orientation anisotropy and the component interface behavior on the resulting multicomponent assemblies. The example 3D assembly, optimized for a multi-load condition, is fabricated for the purpose of demonstration.
Compact Tensegrity Robots Capable of Locomotion Through Mass-Shifting
Authors: Rhodes Tyler , Vikas Vishesh
Published: November 2019

Robustness, compactness, and portability of tensegrity robots make them suitable candidates for locomotion on unknown terrains. Locomotion is achieved by breaking symmetry and altering the position of center-of-mass to induce “tip-over”. The design of curved links of tensegrity mechanisms allows continuous change in the point of contact (along the curve) as compared to discontinuities in the traditional straight links (point contact) which induces impulse reaction forces during locomotion. The illustrated curve-link tensegrity robot achieves smooth locomotion through internal mass-shifting. Additionally, this tensegrity robot displays folding and unfolding. Introduced is a design methodology for fabricating tensegrity robots of varying morphologies with modular components created using rapid prototyping techniques, including 3D printing and laser-cutting. The techniques are utilized to fabricate simple tensegrity structures, followed by locomotive tensegrity robots in icosahedron and half-circle arc morphologies.
A Method to Detect Head Media Spacing Change in a Hard Disk Drive Using an Embedded Contact Sensor
Authors: Rai Rahul , Bhargava Puneet , Knigge Bernhard , Murthy Aravind N.
Published: November 2019

Growth in the demand for higher capacity hard disk drives (HDD) has pushed the requirement for head-media spacing (HMS) to sub-nanometer levels. The drop in operational clearance makes a head-disk interface (HDI) more susceptible to potential head-wear and contamination related issues. Such degradation processes are often accompanied by a noticeable shift in the head-disk clearance. Hence monitoring an interface for a spacing change can be helpful in early detection of its imminent failure. In this paper, we present a method to detect the change in head-disk spacing using an embedded contact sensor (ECS). This technique involves the analysis of ECS dynamic response for an interface that is subjected to heater induced spacing modulations. As the head moves closer to the disk surface, the magnitude of the ECS frequency components can be used to determine the ‘characteristic spacing’ which can be used as a metric to detect any physical change for a given interface.
Achieving Sensing Precision of 0.5nA in Pixel With 7µs Settling Time by a New External Current Sensing Circuit for AMOLED Displays
Authors: Pandey Rajeev , Huang Tzu Hao , Ho Wei-Hsuan , Chao Paul C.-P. , Pribadi Eka Fitrah
Published: November 2019

This study proposes a new push-pull transient current feedforward (PPTCF) based pixel current sensing circuit for active matrix organic light emitting diode (AMOLED) displays with precision within 0.5nA. A finite state machine (FSM) based digital control circuit is designed and developed for the baseline compensation. In order to achieve high accuracy, the digital baseline compensation circuit also incorporates the current digital-to-analog converter (CDAC) and successive approximation current analog-to-digital converter (CADC). The minimum LSB current for the CADC is 10nA. The readout circuit is implemented in the integrated chip with chip area of 125μm × 46μm and fabricated via TSMC T18 process. With standard 3.3V supply, the experimental result shows that the overall power consumption of the chip is 990μW watt. Despite of all parasitic capacitances of the panel display, experimental results show that the proposed circuit can sense 0.5nA current within 7μs of settling time. The sensing precision of 0.5nA within 7μs are the best among all reported literature to date.
Elementary Loading Processes and Scale Effects Involved in Wave-in-Deck Type of Loading: A Summary of the BreaKin JIP
Authors: Scharnke Jule
Published: November 2019

To quantify the loading due to breaking waves, model tests are currently the option of choice. However, it is suspected that scale effects lead to an overestimation of the prototype loading. As such, a typical question in impact load assessment is how conservative load measurements are. To understand how realistic model testing is in this respect, it is necessary to quantify scale effects in the measured loading due to breaking waves as well as to investigate to which extent entrapped air in the wave and during the wave impact is involved. To do so, the BreaKin Joint Industry Project was started in 2016. The objective of the BreaKin JIP was to get more insight into scale effects involved in wave-in-deck model tests and to take first steps towards linking wave kinematics with measured impact loads.

During this JIP wave-in-deck model tests were carried out in MARIN’s Depressurized Wave Basin (DWB) at two scales (25 and 50) in atmospheric and depressurized condition. This paper gives an overview of the results of the BreaKin JIP regarding loading processes involved in wave-in-deck type of impacts, effects of depressurization on measured loads and possible sources of scale effects.
Piston-Modal Resonance in a Box-Wall System
Authors: Huang Yu-xin , Geng Bao-lei , Jiang Sheng-chao
Published: November 2019

Hydrodynamic behavior of wave responses and wave forces induced by piston-modal resonance in the narrow gap formed by a ship section in front of a bottom mounted terminal is investigated based on the OpenFOAM® package. Numerical simulations suggested that the free surface piston-modal oscillations in the narrow gap have closely relationship with the vertical velocity along the gap bottom, implying the velocity flow around the gap bottom is able to affect the wave amplitude in the narrow gap, significantly. The horizontal wave forces can be decomposed into static water forces due to the difference of water level besides the box and the dynamic water forces due to the velocity flow. The amplitudes of static water forces are larger than that of horizontal wave forces, implying that the dynamic water forces can counteract part action of the static water forces. The dynamic wave forces approach to the maximal values at resonant frequencies, indicating that the extreme flow velocity around resonant frequency is useful for reducing the horizontal wave forces.
Design and Inclusion of a Desalination System in a Floating Offshore Wind Farm
Authors: Miriello Davide , Walker Michael , Canizares Loris , Smith Aaron , Roddier Dominique
Published: November 2019

This paper investigates the techno-economic feasibility of integrating a desalination system to an offshore wind farm.

The first part of the paper involves a proposal for the design of a desalination system fitted inside the WindFloat Atlantic hull. Taking into account of the power, footprint, volume and weight requirements of the desalination system, the desalination capacity is chosen to be 10,000 m3/d per platform2. A 3D model of the system is also presented.

The second part of the paper focuses on the development of an economic model that gives as output the levelized cost of water (LCOW) for the studied technology. At first, a methodology to estimate capital expenditure (Capex) and operational expenditure (Opex) of an offshore desalination system with the above-mentioned characteristics is presented. Then, three locations with high wind speeds and with frequent exposure to droughts (Gran Canaria, California and South Africa) are chosen and the model is applied. Particularly interesting results are found for Gran Canaria, isolated system with favorable conditions (high electricity price, high water production cost and good offshore wind resource).
Analytical Study for Lateral Buckling of Imperfect Pipelines With Distributed Buoyancy Section
Authors: Wang Zhenkui , van der Heijden G. H. M. , Tang Yougang
Published: November 2019

Distributed buoyancy method is one of the buckle initiation techniques used to trigger controlled lateral buckling at planned locations for subsea pipelines operating under high temperature and high pressure (HT/HP) conditions. Deviations from a straight profile for pipelines may be introduced by the pipe-laying vessel’s sway motion during the installation process. In this study, analytical solutions of lateral buckling are deduced for imperfect unburied subsea pipelines with a distributed buoyancy section. The effect of initial imperfections on buckled configurations and typical post-buckling behaviours is illustrated and analysed. The results show that, compared to the case without initial imperfection, lateral displacement amplitude becomes larger when initial imperfection exists. Maximum compressive stress increases when wavelength of initial imperfection is smaller than buckled length of pipeline. However, maximum compressive stress decreases when wavelength of initial imperfection is larger than buckled length of pipeline. So it’s better to introduce longer wavelength of initial imperfection.
Study of Extreme Waves Propagating Over Reefs in Large Wave Flume
Authors: Chen Songgui , Wang Zeming , Zheng Jinhai , Zhang Chi , Hu Ke
Published: November 2019

Waves propagating over reefs have been studied by many researchers. However due to limitation of small wave flume, most experiments focused on the normal waves. Extreme waves are the input parameters for structure design on reefs. Thus, experiments of extreme waves propagating over reefs were conducted in the large wave flume of the Tianjin Research Institute of Water Transport Engineering. Extreme wave hydrodynamic within surf zone will be focused on. Tests with different wave heights Hi, wave periods T and water levels on reefs h have been carried out. The model scale is set to be 1:15, then Hi from 4.5m to 12m, T from 9s to 17s, hr from 0 to 3m are generated in the test. Wave breaking points are observed by high speed camera. Wave breaking points move offshore as Hi and T increase and h decrease. Wave setups and wave-induced flows along the reef are measured at different locations. It can be found that wave setups increase with increasing Hi and T and decreasing water level h. Wave-induced flows increase with increasing Hi and h and decreasing T. As waves propagate towards landside, wave setups and wave-induced flows have a local extremum at the middle of surf zone. Compared with our test, Gourlay’s formulas overestimate wave setup while underestimate wave induced flow within extreme wave surf zone.
Analytical Methods for Preliminary Design of Anchor Flanges for Subsea Structures
Authors: Rajaratnam Sabesan , Sriskandarajah T. , Clayton Daryl , Roberts Graeme , Loentgen Vincent , Charnaux Carlos
Published: November 2019

Anchor flanges are interface items which are used to connect pipelines to subsea in-line and end termination structures. They are forged and tend to be long-lead items; therefore, the design of an anchor flange should be completed at a very early project stage, possibly even during the tender phase. An optimised, analytical method for preliminary design would result in reduced design time overall and have beneficial cost implications.

The analytical notch methods (i.e. Neuber’s and Glinka’s) that are presented utilise linear-elastic stress concentration factors to make realistic predictions of the ultimate load carrying capacity of an anchor flange in the non-linear regime.

The linear-elastic stress concentration factor values are calculated with simple analytical formulae and graphs. The analytical notch methods are deployed to predict the anchor flange limit load and peak plastic strain and thereby ensure that the plastic strain remains within the allowable limits of design codes.

The cost and time saving associated with the analytical notch methods, and the accuracy that is maintained, are assessed by comparison with the predictions results obtained from detailed finite element analyses.
Variability in Encountered Waves During Deterministically Repeated Seakeeping Tests at Forward Speed
Authors: van Essen Sanne
Published: November 2019

Numerical seakeeping codes for ships at forward speed in waves are often validated or tuned based on experiments, which makes knowledge about the experimental variability essential. This variability was evaluated using repeat tests during a state-of-the-art seakeeping campaign.

A steep wave condition over the longitudinal basin axis (waveA) and a less steep oblique wave condition (waveB) were studied. Overall similarity as well as individual crest height, steepnesses and timing variability are discussed, because ship response is not equally sensitive for every point in the wave time series. The variability of the measured incoming wave crests and their timing increases with distance from the wave generator for waveA. The crest height variability for waveB is lower and more constant over the basin length (because the propagation distance to the model is constant in oblique waves and wave breaking is less likely).

It was shown that only a small part of the variability close to the wave generator is caused by ‘input’ uncertainties such as the accuracy of the wave generator flap motions, measurement carriage position, their synchronisation and measurement accuracy. The rest of the variability is caused by wave and basin effects, such as wave breaking instabilities and small residual wave-induced currents from previous tests. The latter depend on previous wave conditions, which requires further study.

Further work on the influence of the wave variability on the variability of ship motions, relative wave elevation along a ship and impact loads on deck of a ship at forward speed will be presented in a next publication.
Mean Load Impact on Mooring Chain Fatigue Capacity: Lessons Learned From Full Scale Fatigue Testing of Used Chains
Authors: Gabrielsen Øystein , Larsen Kjell , Dalane Oddgeir , Lie Hans B. , Reinholdtsen Svein-Arne
Published: November 2019

Fatigue of mooring chain is for many floating offshore installations a limiting factor in design. With aging installations and the need for field life extension beyond the original design life, questions on mooring chain endurance are raised. Current SN curves utilized in fatigue limit state (FLS) calculation are based on full scale testing of new chain, performed at a high mean load level (20% of the chains minimum breaking load (MBL)). The high mean load level in the tests do not correspond to the conditions for many chains in operation, as mean load in fatigue relevant seastates are often significantly less than mean load used in the new chain fatigue tests. Mooring chains in operation also experience different degree of corrosion, both general corrosion and pitting. Surface roughness and corrosion pits contribute to crack initiations, and thus reduce fatigue capacity. Fatigue tests with new chain condition cannot be assumed representative for corroded chains.

As part of mooring integrity programs, Equinor has been replacing mooring chains since year 2000. To assess actual fatigue capacity, many chain segments have been full scale fatigue tested. First tests started in 2011, and the tests cover different degrees of corrosion. The tests have been performed at typical mean load levels relevant for operation of the installations, which for most cases are less than 20%MBL. From these tests it is observed that fatigue capacity in some cases are better than expected for new chain, even for chain segments with significant corrosion. Fatigue test results show a large effect of the mean load. For test cases with significant corrosion and high mean load (20%MBL), a significant reduction in fatigue capacity compared to new chains is found.

This paper presents some of the fatigue test results on used chain, highlighting the effect of the mean load for the given chain conditions. Effect of corrosion at mean load of 20%MBL is also included. The paper discusses some of the underlaying causes for the mean load dependency.
State of the Art and Knowledge Gaps on Modelling Structures in Cold Regions
Authors: von Bock und Polach R. U. Franz , Klein Marco , Kubiczek Jan , Kellner Leon , Braun Moritz , Herrnring Hauke
Published: November 2019

The environment in cold regions undergoes significant changes that manifest in rising temperatures and melting ice caps. These processes allow access to new areas for shipping and the installation of structures. However, the occurring changes are not solely a reduction of ice, but also waves increasingly occur in cold regions contributing to ice break up in the Marginal Ice Zone (MIZ) and the transport of ice towards the open sea. Much work has been done to combine the single topic disciplines: wave-hydrodynamics, ice mechanics and structure mechanics to wave-structure (WSI) and ice-structure interaction (ISI). The changing environment in cold regions and the increased wave activity form a new combined discipline: wave-ice-structure interaction (WISI). This paper addresses existing knowledge gaps of the future loading scenario WISI that need to be addressed in engineering to ensure safety for future operations in Polar Regions.

The knowledge gaps however, do not only refer to the discipline interfaces, i.e. challenges in combining them, but also to knowledge gaps within them.

Wave statistics and the cross-effect between wave and ice are widely unknown which limits the definition of a design wave-scenario. Structures in such environments are exposed to subzero temperatures and neither their impact on properties nor on fatigue life is fully understood. While most phenomena of these two disciplines and their implementation into numerical models are established the ice mechanics appear as the weakest link. Ice is a complex material and not all aspects of its mechanical behaviour are understood and if – the implementation into (numerical) models has not been successful yet. Ice pieces that are energetically charged by waves and collide with structures at high velocities and for such high impact loads the governing ice mechanics are hardly covered by the state of the art or not at all.
Hydrodynamics of Towed Vertical Surface-Piercing Cylinders
Authors: Potts Douglas A. , Binns Jonathan R. , Marcollo Hayden , Potts Andrew E.
Published: November 2019

This project investigates a cantilevered cylinder projecting down into the water column moving at high velocity through still water, as is applicable to submarine masts. Surface-piercing cylinders differ from fully submerged cylinders due to the generation of surface wakes and under increasing flow speeds the formation of a ventilated pocket in the lee of the cylinder, both of which grow with increasing velocity, with concomitant effects on the hydrodynamic loading. The relative length of submergence, or immersed aspect ratio (L/D) and end conditions of the cylinder with respect to tip vortex drag effects may also impact the hydrodynamic loads and wake formation. Laboratory testing of surface-piercing cylinders to date has predominantly been confined to characterising the wakes shed from a rigid cylinder cantilevered down into the water from a towing tank carriage, which under certain test conditions will also exhibit significant Vortex-Induced-Vibration (VIV), though not adequately identified and accounted for in its magnification of drag and wake.
Laboratory Investigation of Helical Strakes With Serrated and Twisted Fins to Suppress VIV
Authors: Assi Gustavo R. S. , Crespi Tommaso
Published: November 2019

Slender offshore structures of a cylindrical cross section, such as drilling and production risers, are susceptible to vortex-induced vibrations (VIV) when exposed to water currents. The present work presents an experimental investigation of the suppression of VIV of a circular cylinder by means of three different types of helical strakes: (i) a strake with continuous blades, (ii) a strake with serrated blades (or fins) and (iii) a strake with serrated blades individually twisted in relation to the incoming flow. By altering the blade geometry to produce the twisted-bladed strake, it was possible to keep the same level of suppression of the cross-flow vibration achieved by conventional strakes, but reducing drag in 15%. Experiments have been conducted in a recirculating water channel at moderate Reynolds numbers.
Making Effective WEC Design Choices Based on Simulation and Analysis
Authors: Vance Charlene , Ringsberg Jonas W. , Yang Shun-Han
Published: November 2019

The study presents analyses of key parameters that affect the performance of the point absorbing wave energy converter (WEC). Performance is assessed by running hydrodynamic and structural response simulations and calculating the power absorption of the WEC and fatigue damage in the mooring lines from the output data. The baseline model of the WEC input to the simulation is modelled after the WaveEL 3.0 device, designed by Waves4Power and installed in Runde, Norway. Simulations are run for single buoy and small array configurations, varying environmental conditions, mooring system, and WEC buoy shaft length. Environmental conditions are chosen to reflect locations studied as potential future installation sites. Select configurations are further analyzed through an analysis of LCOE and LCA. The results show that optimal mooring line geometry depends on water depth, and that optimal shaft length depends on the average sea conditions at the location. The array simulations show that small WEC separating distances will limit the mooring line length, which will result in lower power absorption and lower fatigue lives in the mooring lines. The LCOE shows that the four-buoy array configuration is the most profitable, and both the LCOE and LCA show that the main process contribution to climate change and the total product cost is the manufacturing of the WEC buoy itself. The research in this study demonstrates the importance of using simulations to make effective WEC design choices for a given environment.
The Modelling and Optimal Control of a Hybrid Propulsion System for an Ice-Capable Ship
Authors: Zhou Yi , Pazouki Kayvan , Norman Rose
Published: November 2019

Due to the effect of global warming, navigation on the Northern Sea Route (NSR) has become a more economical and reliable choice for international cargo transportation. In some ways, global warming has increased the opportunity of shipping activities in the Arctic region and hence the need for ice-capable vessels. NSR shipping provides benefits for international trade, but challenges still exist. Although conventional direct drive propulsion system connected to 2 stroke marine engine is normally considered the most efficient approach for long-range transport, for icebreaking operation which requires prime movers to work at partial load, conventional mechanical propulsion systems generally have poor fuel efficiency and high emissions. Moreover, the harmful gases produced by ships trading in NSR have a significant impact on the Arctic climate. Moreover, a traditional mechanical drive icebreaker with a diesel engine is required to operate at high torque, low rpm during icebreaking operation. Thus conventional diesel engine that isn’t optimised to operate at this point would be inefficient and would produce black carbon due to incomplete combustion, which has the potential to cause ice, snow, and cloud albedo out of proportion with normal pattern, thus lead to serious impacts on the Arctic environment and eco-system. Arctic ship propulsion systems have been developing since the 19th century, with modifications such as the use of diesel electric propulsion systems and nuclear power propulsion systems which can ideally meet the requirements of ice breaking operation (low speed and high torque), however, drawbacks still exist in these systems, such as poor fuel efficiency at low speeds for diesel electric propulsion and for nuclear power, there are limitations such as high initial cost, management of nuclear waste and the fact that the required deep knowledge of nuclear technology is mastered by few countries. Hybrid propulsion is a new technology for ice-capable ships, which can address the partial loading efficiency problem in diesel-electric propulsion by charging and discharging a battery energy storage unit which can allow the ship to work in zero-emission mode in some sensitive areas. In this paper, detailed modelling, primary control strategies (voltage and frequency stability) and efficiency analysis of system components such as the motor, generator, battery and conversion devices etc. are and implemented in software, and then the whole power system is simulated with a secondary control strategy (load power sharing and battery aging concern) in both ice and open water load conditions. The results from the diesel electric system and hybrid system total fuel consumption within a target journey are compared to investigate the advantage of the hybrid system, which show up to a 40% fuel consumption reduction for hybrid propulsion arrangement. A tertiary control strategy for energy management is analysed and implemented in the system to further reduce system fuel consumption.
Experimental and Numerical Investigations on Wave Dynamics of a Dual-Chamber OWC Wave Energy Device
Authors: Ning Dezhi , Wang Rongquan , Teng Bin , Zou Qingping
Published: November 2019

Oscillating Water Column (OWC) wave energy device is one of the most studied and applied wave energy converters (WECs). The survivability of WECs is a major concern in the OWC design. In this study, the wave dynamics of a dual-chamber OWC device is numerically and experimentally investigated. The experimental tests were carried out in the wave-current flume at the State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology. A fully nonlinear numerical wave flume based on potential-flow theory and time-domain higher-order boundary element method (HOBEM) is developed and applied to simulate the interaction between air, wave and the dual-chamber OWC device. The numerical model is validated by comparing the simulated wave induced pressure on the barrier walls with the measurements. Then the wave forces and the moment on the device is numerically investigated. The model and experimental results indicate that the horizontal wave force on the front barrier wall is much larger than that on the internal barrier wall. The joint between the back wall and the ground withstands the largest bending moment, therefore, is most vulnerable to structure damage and fatigue.
Preliminary Experimental Study on the Influence of the Local Wind Field on Forces From Breaking Waves on a Circular Cylinder
Authors: Caroee Kristoffersen Julie , Bredmose Henrik , Georgakis Christos Thomas , Tao Longbin
Published: November 2019

The spatial localized influence of wind on wave induced load on a flexible cylinder has been assessed throughout a test series conducted in a wave-wind-current flume at Newcastle University. The tests are motivated from other experimental and numerical investigations showing air flow separation on the leeward side of steep waves that can lead to added wind energy transfer, which could suggest an increase in the impulsive wave loading. The waves are generated as focused waves, resulting in a plunging breaker, leading to an impulsive wave load. The test model was equipped with a load cell measuring the connection load. Due to the flexibility of the cylinder, the measured force response shows oscillations and dynamic amplification of the load. The maxima of the force responses are compared for the tests with and without wind. Another measure for comparison is the local and short-lived impulse, which is responsible for the amplification. This impulsive load is estimated from the load cell and acceleration measurements. For the tests in this study, the introduction of wind over the breaking waves does for some cases lead to a slight increase in the peak of the impulsive load and thereby the load response, although large scattering is present. Further investigations are needed to verify this effect. Some differences in the time series of the free surface elevation are observed when wind is present, but the maximum of the surface elevation does not change notably, and the slope is only minimally changed, meaning that this should not give basis for the differences in the loads.
Laminar Displacement Flows in Vertical Eccentric Annuli: Experiments and Simulations
Authors: Etrati Ali , Frigaard Ian
Published: November 2019

We present a numerical investigation of laminar miscible displacement flows in narrow, vertical, eccentric annuli. This study is motivated by the primary cementing stage of oil and gas well production, where successful displacement of drilling mud is crucial for the well integrity and zonal isolation. The large number of characterizing parameters makes a complete description of such flows challenging. In turn, this means that the design of effective strategies for primary cementing is a difficult task. As a result the existing literature is mostly based on non-inertial Hele-Shaw models and experiments in narrow annuli, where the dimensionality of the problem is reduced. In this preliminary study, we run a series of three-dimensional numerical simulations, using a Volume of Fluid (VOF) method to capture the interface between the fluids. Both Newtonian and non-Newtonian fluids are considered, and a variety of different phenomena are observed, e.g. dispersive spikes, static layers, instabilities and secondary flows. The range of flow parameters used in the simulations are similar to existing experimental data to allow for a preliminary comparison. The results show qualitative agreement with the experiments and gap-averaged models.
Solitary Wave Interaction With Vertical Porous Barriers
Authors: Francis Vivek , Ramakrishnan Balaji , Rudman Murray
Published: November 2019

Tsunami waves pose a threat to the coastal zone and numerous studies have been carried out in the past to understand them. The present study — carried out in the 2D wave flume at the Ocean Engineering Laboratory of IIT Bombay — focusses on the interaction and run-up of solitary waves on coastal protection structures in the form of thin, rigid vertical porous barriers with special attention given to the degree of energy dissipation. In order to understand the physics of the energy dissipation problem, the propagation of the solitary wave and its interaction with the porous barrier has been studied from the viewpoint of energy balance. Based on this, a proper relationship for the wave energy dissipated by the barrier has been developed. Using this relationship, the experimental data has been analyzed and we have determined that the plate porosity that gives the optimal energy dissipation characteristics lies within the 10–20% range. In addition, using the experimental data, we have derived a formula for calculating the maximum wave run-up on the porous barrier models which should be useful in the planning, design, construction and maintenance of coastal protection structures.