bluuebunny/crossref_metadata_2025 huggingface dataset:
Bayesian Optimization of Equilibrium States in Elastomeric Beams
Authors: Yoo David , Wiley Carson , Gillman Andrew , Chen Vincent , Juhl Abigail , Buskohl Philip
Published: November 2019

Architected elastomers have demonstrated great potential for energy absorption, multi-resonant vibration isolation, and multi-bandgap acoustic control, due to the reversibility and programmability of their mechanical instabilities. However, computational design tools are needed to explore the large parameter space that regulates buckling-based mechanical instability behavior. In this study, we develop a machine-learning-based design optimization framework to control equilibrium states of a bistable elastomeric beam, while also regulating the required energy to transition between these configurations. Leveraging symmetry to reduce the design space, the research is performed on a single element, an inclined, slender beam, through a Fourier series parameterization. To evaluate the force-displacement response of the bistable beam, a nonlinear finite element analysis (FEA) with an arc-length continuation method is employed in a commercial FEA tool. Due to the highly non-convex bistability response of the beam in this proposed design space and the computational cost of the FEA analysis, a Bayesian optimization is implemented to promote a better trade-off between the number of function evaluations and rate of convergence. Bayesian optimization depends on several optimization parameters, which are systematically tuned in this study to characterize their role on the optimization process. With the proposed method, the equilibrium displacement and the ratio of output to input energy between stable states can be optimized within a few tens of iterations. A multi-objective optimization is also carried out to study the trade-off between equilibrium position and the energetics to transition between the bistabilities.
Experimental Study on Folding Patterns and Deployability of Inflatable Structures
Authors: Ishida Sachiko , Azuri Hakimi
Published: November 2019

In this study, the authors experimentally investigate the relationship between folding patterns and performances of inflatable structures; compactness and deployability. Inflatable structures are widely applied in various engineering fields such as airbags in automobile industry, inflatable building in architectural field, and inflatable satellite antenna and landing equipment to Mars in space engineering field. However, these two requirements can be a tradeoff, as a compact product is hard to deploy in general. As a possible solution, circular spiral patterns are adopted in this study, because 1) they can be simultaneously deployed along spiral fold lines that is an advantage on deployability, and 2) the removal of the core of the circular sheet can make the sheet folded more compactly that is an advantage on compactness. Inflation models with different design parameters are created and tested. As experimental results, the inflation time (i. e. deployablity) and the initial width (i. e. compactness) can be optimized simultaneously in terms of four design parameters, but a trade-off relationship is observed in terms of the rest parameter; the folding angle formed by the V-shaped fold lines.
On the Unfolding Process of Triangular Resch Patterns: A Finite Particle Method Investigation
Authors: Yu Ying , Chen Yan , Paulino Glaucio H.
Published: November 2019

Many numerical approaches have been proposed to simulate the folding process of origami pattern under external force or displacement. Based on the Finite Particle Method (FPM), this paper develops a method to simulate the unfolding process of the Origami Pattern named triangular Resch Pattern by the energy stored in the crease. The formulations of the FPM for particle-bar-hinge models are derived. A simple fold origami example is given to verify the proposed formulations. Finally, the unfolding process of the triangular Resch pattern is simulated, and the symmetry properties of the triangular Resch pattern are obtained. The symmetry properties of this pattern have potential use in the degree-of-freedom reduction and motion control.
Calibration of Reconfigurable Stewart-Gough Platform for Mobile Machining Application
Authors: Hansen Andreas Bennekov , Laursen Jørgen Møberg , Henriksen Sebastian Theis , Ringgaard Kasper , Rydahl-Haastrup Morten , Balling Ole
Published: November 2019

This paper considers the problem of calibrating a reconfigurable Stewart-Gough platform for mobile machining applications using partial information measurements. The motivation for the work comes from the wind turbine industry, where cost reduction for machining of large components is desired. In the paper kinematic description of an actual prototype machine, together with description of partial information calibration methods of which simulated and experimental results are shown.

Results of the proposed calibration methods, where only positional data of the machine was measured by a laser tracker, showed great improvement of the machine performance. Results from experiments showed achievable positioning tolerances of maximum 65μm after an initial factory calibration, and 146μm for a secondary calibration, where fewer parameters were included to reduce lost machining time during configuration change. Machining tests furthermore indicated that it is possible to continue machining across different configurations.
Kinetic Energy Recovery System for Urban Mobility
Authors: Vignati Michele , Barzaghi Simone , Tarsitano Davide , Braghin Francesco
Published: November 2019

The aim of this work is to discuss the possibility to store energy on board electric vehicles by means of flywheels as alternative to common batteries. A detailed optimization of the power storage system for the mini-car Icar0 ZD-1 with a target autonomy of 50 km in urban context is carried out. A preliminary designed is then made considering the power consumption in urban context accounting for the full power-train energetic model. Material, geometry and motor have been selected to fit all the vehicle space requirements considering also that flywheels operate in vacuum environment. In particular, attention is focused on some critical aspects like the effect of vibrations transmitted to the flywheel. For this reason, induced gyroscopic effects are considered both in straight and during turns. Finally, a possible bearing configuration is presented.
Towards Consistent Value Orientation in Release Planning
Authors: Şahin Tarık , Inkermann David , Vietor Thomas
Published: November 2019

Product development is experiencing a paradigm shift under the impact of highly segmented and rapidly evolving markets. The intention to offer successful products in such turbulent conditions forces companies to provide value comprehensively but rapidly. These attempts conceal a high risk of rising product complexities and development efforts. For this reason, the aim of design should be to maintain or improve value contribution according to customer and market demands with fast response time while reducing internal product disruption and development efforts. A proactive planning of continuous value contribution by introducing new product features, while considering the complexity of product structures and corresponding development efforts, is established in the field of release planning. Here, systematic ways are proposed to support the identification and timing of product features to provide value for customers and markets as well as the consideration and planning of according efforts for their realization. However, the literature highlights a need for more consistent value orientation in release planning. For this reason, this contribution aims to present an outline and further steps for consistent value orientation in release planning in the context of systems engineering. Accordingly, this contribution first discusses the significance of consistent value orientation during release planning activities. On this basis, requirements for consistent value orientation in release planning are presented and the respective current state of existing concepts are discussed. Ultimately, a framework towards consistent value orientation in release planning is presented with a concluding outlook for further research.
Computationally Derived Adaptive Inspirational Stimuli for Real-Time Design Support During Concept Generation
Authors: Goucher-Lambert Kosa , Gyory Joshua T. , Kotovsky Kenneth , Cagan Jonathan
Published: November 2019

Design activity can be supported using inspirational stimuli (e.g., analogies, patents, etc.), by helping designers overcome impasses or in generating solutions with more positive characteristics during ideation. Design researchers typically generate inspirational stimuli a priori in order to investigate their impact. However, for a chosen stimulus to possess maximal utility, it should automatically reflect the current and ongoing progress of the designer. In this work, designers receive computationally selected inspirational stimuli midway through an ideation session in response to the state of their current solution. Sourced from a broad database of related example solutions, the semantic similarity between the content of the current design and concepts within the database determine which potential stimulus is received. Designers receive a particular stimulus based on three experimental conditions: a semantically near stimulus, a semantically far stimulus, or no stimulus (control). Results indicate that adaptive inspirational stimuli can be determined using Latent Semantic Analysis (LSA) and that semantic similarity measures are a promising approach for real-time monitoring of the design process. The ability to achieve differentiable near vs. far stimuli was validated using both semantic cosine similarity values and participant self-response ratings. As a further contribution, this work also explores the impact of different types of adaptive inspirational stimuli on design outcomes. Here, near inspirational stimuli increase the feasibility of design solutions. Results also demonstrate the significant impact of the overall inspirational stimulus innovativeness on final design outcomes, which may be greater than differences across individual sub-dimensions.
Towards Selective Volumetric Additive Manufacturing and Processing of Ceramics
Authors: Iliopoulos A. P. , Michopoulos J. G. , Steuben J. C. , Birnbaum A. J. , Graber B. D. , Rock B. Y. , Johnson L. A. , Gorzkowski E. P.
Published: November 2019

The development of advanced additive manufacturing (AM) and material processing techniques is currently a topic of great interest to broad communities of scientists and engineers. In particular, there is a need for AM processes capable of producing functional and high-quality components at a faster rate than is currently achievable. In response to this demand, the present work introduces the initial steps of a novel spatially-resolved and selective approach for processing volumetric regions of ceramic materials. The proposed method utilizes microwave radiation to heat material at desired locations within a domain filled with ceramic powder. Using this principle of operation, a number of methods for implementation of this process are proposed. As a first step, a multiphysics computational methodology and an associated model that allows for the analysis and design of relevant processing systems is introduced. Additionally, a number of simulations demonstrating the feasibility of the proposed methodology are presented. Based on these preliminary results, we conclude with a discussion of ongoing and future efforts to fully realize this technology.
Evaluating Idea Quantity and Variety When Using Digital Collaboration Tools to Support Brainstorming in Non-Collocated Teams
Authors: Kaweesa Dorcas V. , McComb Christopher , Menold Jessica , Ritter Sarah , Meisel Nicholas A.
Published: November 2019

The advent of modern digital communication technology has enabled engineers to effectively collaborate regardless of team members’ geographic locations. As such, introducing engineering students to virtual environments and collaborative tools is particularly important to prepare them for careers in increasingly digital environments. This study investigates how integrating online collaboration tools in students’ idea generation activities impacts the i) quantity and ii) variety of ideas generated after a peer-feedback session. Students from five sections of a first-year engineering design course were assigned to either a collocated design team or a non-collocated design team to participate in a collaborative design feedback activity. Students individually generated an idea set using an online brainstorming tool (Stormboard), received peer-feedback via one of two delivery conditions (in-person or virtual through video conferencing), and revised their idea set based on the received feedback. Each final idea set was analyzed and compared to identify any differences in the final idea quantity and variety due to the assigned feedback delivery condition. Results revealed a statistically significant difference, but with minimal realistic impact on the final quantity of ideas (equivalent to a difference of one idea between groups). No statistically significant difference was found in the final variety of ideas generated between collocated and non-collocated design teams after the peerfeedback session. This suggests that feedback provided through digital collaboration tools may be used to support idea generation in non-collocated teams without being detrimental to ideation solutions. The implications of these findings are significant for faculty or students who may be involved in online learning activities centered on engineering design.
Renormalization Group Method for Singular Perturbed Systems Driven by Fractional Brownian Motion
Authors: Guo Lihong , Shi Shaoyun , Chen YangQuan
Published: November 2019

In this article, we use the renormalization group method to study the approximate solution of stochastic differential equations (SDEs) driven by fractional Brownian motion with Hurst parameter H∈12,1. We derive a related reduced system, which we use to construct the separate scale approximation solutions. It is shown that the approximate solutions remain valid with high probability on large time scales. We also expect that our general approach can be applied to the fields of physics, finance, and engineering, etc.
Thinking About Design Thinking: Toward Capturing Students’ Metacognition in Solving Design Problems
Authors: Olewnik Andrew , Stuhlmiller Brian , Yerrick Randy
Published: November 2019

In this short-paper we describe the ongoing development of a research methodology toward accessing how students think about design. Consideration of the formulation of a design problem statement that is suitable for supporting discussion with students from multiple disciplines at various points in their engineering education is the specific focus. The discussion draws from work on problem typology, design thinking, and metacognition as a theoretical basis that informs the problem formulation and planned approach for analysis.
Conducting Non-Adaptive Experiments in a Live Setting: A Bayesian Approach to Determining Optimal Sample Size
Authors: Sudarsanam Nandan , Chandran Ramya , Frey Daniel D.
Published: November 2019

This research studies the use of predetermined experimental plans in a live setting with a finite implementation horizon. In this context, we seek to determine the optimal experimental budget in different environments using a Bayesian framework. We derive theoretical results on the optimal allocation of resources to treatments with the objective of minimizing cumulative regret, a metric commonly used in online statistical learning. Our base case studies a setting with two treatments assuming Gaussian priors for the treatment means and noise distributions. We extend our study through analytical and semi-analytical techniques which explore worst-case bounds and the generalization to k treatments. We determine theoretical limits for the experimental budget across all possible scenarios. The optimal level of experimentation that is recommended by this study varies extensively and depends on the experimental environment as well as the number of available units. This highlights the importance of such an approach which incorporates these factors to determine the budget.
Satisfactory Optimization Design for Fractional Order PID Controller
Authors: Liu Tianyu , Jia Yuanjun , Jin Weidong , Wang Yong
Published: November 2019

This paper presents a new parameters optimization approach for fractional order PID controllers, which uses a satisfactory optimization model. To fulfill different design performance specfications and constrains of systems, the application of multi-criterion satisfactory optimization to fractional control systems is considered. At the same time, the performance of fractional control systems controlled by fractional order controller and integer order controller is discussed. The simulation illustrates the effectiveness of the proposed method and the superiority of the fractional order controller in both time domain and frequency domain.
Multi-Parameter Coupling Effect of Wearable Energy Harvesting Backpack From Human Motion
Authors: Hou Zehao , Cao Junyi , Zuo Lei
Published: November 2019

The main purpose of wearable energy harvesting devices is to replace the chemical battery and supply enough power for portable devices. Therefore, this paper derives the function expression of harvested energy via frequency ratio (excitation frequency/natural frequency) and external resistance, aiming to optimize running conditions directly in practical matters. It proposes that when energy harvesting devices work at direct force excitation the optimal condition is the frequency ratio equal to one. But the optimal excitation frequency is related to damping at base excitation, When the value of the damping ratio is less than 0.258, there is a local peak output power. Conversely, the larger excitation frequency is the larger output power is. The optimal external resistance is related with back EFM constant of the electromagnetic transducer at both cases. In the end, some experiment was conducted to study the relationship between output and some parameters.
From Idea to Production: A Retrospective and Longitudinal Case Study of Prototypes and Prototyping Strategies
Authors: Arndt Hansen Camilla , Özkil Ali Gürcan
Published: November 2019

This study explores the value of visualizing the prototyping activities in a new product development process from idea to production. Through a case study of a hardware startup, we present a visualization of their prototyping processes, from early idea to the introduction of several product versions to market. Analyzing qualitative and quantitative parameters of the visualization allows us to understand how prototyping strategies can change over the course of a product development process. Specifically, we focus on the prototyping of parallel concepts, iterations of concepts, manufacturing processes used for prototypes as well as prototyping of isolated or integrated systems. Based on this longitudinal analysis, we present a number of insights that are otherwise difficult to extract. We observe how parallel prototypes of isolated systems can be used to explore the solution space and later be synthesized into prototypes for integrated systems. Furthermore, we understand how the need to scale up production can lead to increased prototyping activities, as several parts of a product must be redesigned. This study illustrates the utility of a retrospective visualization approach and serves as the first step in formulation of generalized guidelines for prototyping strategies for holistic product development, through further case studies.
Spacecraft Failure Analysis From the Perspective of Design Decision-Making
Authors: Kattakuri Vikranth , Panchal Jitesh H.
Published: November 2019

Space mission-related projects are demanding and risky undertakings because of their complexity and cost. Many missions have failed over the years due to anomalies in either the launch vehicle or the spacecraft. Projects of such magnitude with undetected flaws due to ineffective process controls account for huge losses. Such failures continue to occur despite the studies on systems engineering process deficiencies and the state-of-the-art systems engineering practices in place. To further explore the reasons behind majority of the failures, we analyzed the failure data of space missions that happened over the last decade. Based on that information, we studied the launch-related failure events from a design decision-making perspective by employing failure event chain-based framework and identified some dominant cognitive biases that might have impacted the overall system performance leading to unintended catastrophes. The results of the study are presented in this paper.
Precision Measurement and Comprehensive Analysis of Dielectrophoretic Crossover Behavior of Micro-Particles
Authors: Kao Ying-Chuan , Lu Yun-Wei , Sun Chieh , Hung Chia-Ling , Juang Jia-Yang
Published: November 2019

To be one of the hottest topics recent years, a huge amount of diverse applications of the Dielectrophoresis (DEP) phenomenon have been discovered and published. The DEP force mainly comes from the difference in dielectric polarizability between the suspended particles and the suspending medium and it only occurs when the applied AC electric field is non-uniform in space. There are many important parameters that affect the magnitude, direction and the crossover frequency of the DEP force, such as the applied AC electric field frequency, electric field distribution, applied voltage, medium conductivity, particle permittivity, particle size, the electric double layer of particles and so on. Variation of each of the above mentioned parameters could cause great difference in the dielectrophoretic behavior of particles. People have made great efforts in quantifying the influence of them but there are still a lot of uncertain relations and mechanisms to be verified. Therefore, we present a comprehensive analysis of the crossover behavior of micro-particles due to DEP and several concurrent phenomena through both experiments and finite element simulations and provides an important foundation for further insight into electrical properties of micro-particles and for more advanced Lab-on-chip devices developments.
Hybrid Lubricant Film With High Bonding Ratio and High Coverage
Authors: Tani Hiroshi , Uesaraie Yuki , Lu Renguo , Koganezawa Shinji , Tagawa Norio
Published: November 2019

The frictional properties of a hybrid lubricant film composited from perfluoropolyether (PFPE) lubricant (Moresco DDOH) with single end group and PFPE film deposited from HT170 (Solvay) via photoelectron-assisted chemical vapor deposition (PACVD) were evaluated using a pin-on-disk tester and compared with that of a Z-tetraol dip-coated film. The frictional coefficient of only the HT170 film deposited via PACVD was considerably high; however, the hybrid lubricant film without the mobile fraction showed a friction coefficient equivalent to that of the Z-tetraol film with a mobile fraction of 40%.
Design and Implementation of a High Accuracy Interpolation Encoder IC for Magnetic Sensor
Authors: Chen Wen-Yu , Zhang Yi-Feng , Chao Paul C.-P. , Pribadi Eka Fitrah
Published: November 2019

The magnetic encoder (ME) always employs sensor passing through periodic and equal distance grating and then generates periodic quadrature scaling signals for displacement measurement. The phase is relative to the movement. To improve encoder accuracy or resolution, electronic interpolation technique had been developed to subdivide the phase of quadrature scaling signals. According to the trends, this paper proposed a specific method with excellent noise immunity characteristic and a complete calibration process to improve the accuracy of the system. The designed circuit is taped-out using TSMC 0.18-μm CMOS process, where the active area is 1643 μm × 1676 μm. The chip has the specification of 3.3 V supply voltage, 20 MHz clock frequency, and 0.0859 mW power consumption. The accuracy of the measurement system is 1.065um.
Air Bearing Pushback in Heat Assisted Magnetic Recording
Authors: Xiong Shaomin , Smith Robert , Nguyen Chanh , Zhang Youfeng , Yoon Yeoungchin
Published: November 2019

The air bearing surface is critical to the spacing control in current hard disk drives (HDDs). Thermal protrusions, including thermal flying height control (TFC) and writer coil protrusion, drive the reader/writer elements closer to the magnetic media. The spacing control actuation efficiency depends on the air bearing push back response after the TFC or writer protrudes. In the next generation hard disk drive technology, heat assisted magnetic recording (HAMR), laser induced protrusions further complicate the spacing control. The laser induced protrusions, such as the localized NFT protrusion and a wider change of the crown and camber, have very different dimensions and transient characteristics than the traditional TFC and writer protrusion. The dimension of the NFT protrusion is relatively smaller, and the transient is much faster than the TFC protrusion. However, it is found that the NFT protrusion is large enough to generate an air bearing push back effect, which changes the read and write spacing when the laser is powered on. To accurately control spacing in HAMR, this push back effect has to be taken into account.
Laser Current Studies in Heat-Assisted Magnetic Recording
Authors: Trinh Tan D. , Rajauria Sukumar , Smith Robert , Schreck Erhard , Dai Qing , Talke Frank E.
Published: November 2019

In heat-assisted magnetic recording (HAMR), optical power from a laser diode mounted on the slider is used to heat up a nanometer scale area on the disk surface to approximately 450°C, facilitating the writing process. Controlling optical power or current that is applied to the laser diode in HAMR is a critical task. In this study, a fully integrated system of HAMR heads and disks is used to study laser current as a function of the magnetic write width (MWW), the operating radius, and the head-disk clearance. Our experimental results show that the laser current is a linear function of the magnetic write width and the head-disk clearance. As the operating radius increases from the inner diameter to the outer diameter of the disk, the laser current increases by approximately 20%.
Snap Load Induced by Slack-Taut Process in a Taut Mooring Line
Authors: Qiao Dongsheng , Tang Wei , Suo Yunfei , Yan Jun , Li Yugang , Zhou Daocheng
Published: November 2019

The large amplitude motion of floating structures could cause slack-taut transformation in the taut mooring system, which may result in snap load. The dynamic finite element analysis model is established to simulate the slack-taut process through adding a series of sinusoidal excitation with different amplitudes and frequencies to the upper end of a taut mooring line. During the slack-taut process, the minimum dynamic tension could be close to zero, and the maximum dynamic tension could come up to several times of pretension. The change laws of dynamic tension during the slack-taut process are compared and summarized. The calculation results show that the phenomenon of slack-taut could occur when the amplitude and frequency of excitation reach some certain value. The mooring line tension spectra show that the doubling and higher frequency components appear in addition to the frequency of excitation. The results could provide a reference for further investigating on the mechanism of snap load and the design of mooring system.
An Approach for Estimating the Corrosion Rates on Aging FPSO Hull Structures
Authors: Larangeira Vicente d’Orema Albuquerque , Videiro Paulo Maurício , Júnior José Alfredo Ferrari , Sagrilo Luis Volnei Sudati
Published: November 2019

This paper presents a methodology to estimate the thickness loss on hulls of Floating, Production, Storage and Offloading (FPSO) platforms under general corrosion. The main purpose is to define characteristic corrosion rates for structural reassessment of the extension of life of FPSOs considering results of previous in-life inspections.

The steel wear generates sectional loss and capacity reduction, possibly leading to structural failure. Being capable of estimating FPSO’s plates and stiffeners thickness along the operational life would be a considerable safety improvement for the whole industry, benefiting operators and classifications societies.

During this research, different models were investigated to define the proposed methodology: (a) Model A (Garbatov and Soares [1,2]); (b) Model B (Melchers et al. [3–11] and, the one considered more appropriate to this study, Model C (Paik et al. [12,16]).

The proposed approach, based on Paik et al (2003), considers that the results of thickness loss readings in inspections during the operational life of the FPSO may be modeled by the Weibull model. Then, this model is applied to estimate the characteristic corrosion rate for the structural reassessment of FPSO extension life.

Results of the proposed methodology are presented for four structural components of a typical converted FPSO single hull in operation at Campos Basin, Brazil offshore.
Comparison of the Environmental Contour Method and Response-Based Analysis Using Response Emulator for Estimating Extreme Ship Responses
Authors: Vanem Erik , Guo Bingjie
Published: November 2019

Environmental contours are often applied in probabilistic structural reliability analysis to identify extreme environ-mental conditions that may give rise to extreme loads and responses. They facilitate approximate long term analysis of critical structural responses in situations where computationally heavy and time-consuming response calculations makes full long-term analysis infeasible. The environmental contour method identifies extreme environmental conditions that are expected to give rise to extreme structural response of marine structures. The extreme responses can then be estimated by performing response calculations for environmental conditions along the contours.

Response-based analysis is an alternative, where extreme value analysis is performed on the actual response rather than on the environmental conditions. For complex structures, this is often not practical due to computationally heavy response calculations. However, by establishing statistical emulators of the response, using machine learning techniques, one may obtain long time-series of the structural response and use this to estimate extreme responses.

In this paper, the contour method will be compared to response-based estimation of extreme vertical bending moment for a tanker. A response emulator based on Gaussian processes regression with adaptive sampling has been established based on response calculations from a hydrodynamic model. Long time-series of sea-state parameters such as significant wave height and wave period are used to construct N-year environmental contours and the extreme N-year response is estimated from numerical calculations for identified sea states. At the same time, the response emulator is applied on the time series to provide long time-series of structural response, in this case vertical bending moment of a tanker. Extreme value analysis is then performed directly on the responses to estimate the N-year extreme response. The results from either method will then be compared, and it is possible to evaluate the accuracy of the environmental contour method in estimating the response.
The Aerodynamic Performance of Offshore Twin Vertical Axis Wind Turbines With Deflector
Authors: Jiang Yichen , Zhao Peidong , Zou Li , Zhang Guiyong , Zong Zhi
Published: November 2019

A novel design of offshore twin counter-rotating vertical axis wind turbines (VAWTs) with deflector is proposed in this paper. We investigate the performance of the twin VAWTs by the two-dimensional computational fluid dynamic method with the Spalart-Allmaras turbulence model. Then, the performances of twin VAWTs with three kinds of deflectors are compared. The results show that installing the front deflector leads to significant improved aerodynamic performance. To better understand the simulation results, we introduce a simple and effective method to obtain the blade’s angle of attack. The mechanism of enhanced performance by deflector is pointed out, based on the information of the blade’s local angle of attack and flow field. Finally, a guideline on the design of deflector for the twin vertical axis wind turbines is provided.
Extreme and Fatigue Analysis of a Dynamic Subsea Power Umbilical
Authors: Yan Qu , Hong Guo , Lei Zhang , Zhenqin Yuan , Juyue Li
Published: November 2019

This paper presents an analysis procedure and results of extreme loading effect and fatigue damage of a dynamic subsea power umbilical. The umbilical was proposed by Hengtong submarine power cable Co., Ltd intended for a FPSO in south China sea at a water depth of 400 m. The umbilical cross section consists of three copper conductor strands and two layers of steel amour wires. A pliant wave configuration is used to accommodate large offset of the FPSO in the harsh environmental condition. Orcaflex is used to verify the tension and curvature of the umbilical in extreme condition against the umbilical capacity curve. UFLEX is used to estimate the mechanical properties and local stress of the umbilical. Fatigue damage is estimated by using results from the global analysis and local stress analysis. The results show that the umbilical cross section design satisfices the acceptance criteria for both extreme and fatigue damage.
Development of a Low-Cost Autonomous Underwater Vehicle for Irrigation Canal Monitoring
Authors: Masud Mamoon , Mazhar Suleman
Published: November 2019

Indus river basin’s irrigation system in Pakistan is extremely complex, spanning over 90,000 km. Maintenance and monitoring of this extensive network demand enormous resources. This paper describes the development of a streamlined and low-cost autonomous underwater vehicle (AUV) for the monitoring of irrigation canals including water quality monitoring and water leak detection. The vehicle is a hoveringtype AUV, designed mainly for monitoring irrigation canals, with fully documented design and open source code. It has a length of 0.43 m, and a radius of 0.09 m with a depth rating of 4m. Multiple sensors have been installed onboard the AUV for monitoring water quality parameters including pH, turbidity, total dissolved solids, temperature, and electrical conductivity. A 9-DOF IMU, GY-85, is used, which incorporates an accelerometer, a gyroscope, and a magnetometer. The readings from these three sensors are fused together using direction cosine matrix algorithm, providing the AUV with the roll, pitch and yaw angles. A water pressure sensor, MS5837, gives the depth of the AUV. Four thrusters control the vehicle’s surge and heave, providing 3 DOF. The thrusters are controlled using a proportional-integral-derivative feedback control system, with IMU data and water depth being the controller’s input and the thruster’s speed as the output. The AUV is controlled by a single onboard processor, Arduino Mega 2560.

A flow sensor has been installed beneath the main hull, for monitoring the changes in canal water flow and detecting potential water theft in the irrigation system. For recording underwater sounds, an indigenously developed hydrophone is placed on the AUV. The vehicle also provides information on water quality, providing the capability to identify the potential source(s) of water contamination. Detection of such events can provide useful policy inputs for improving irrigation efficiency and reducing water contamination. The AUV, being low cost and of small size, is suitable for autonomous maneuvering and water quality monitoring in the irrigation canals and can be used for monitoring irrigation networks at a large scale.
Eliminating the Uncertainties in Hydraulic and Ice Loads on Berm Breakwaters
Authors: Pontiki Maria , Leira Bernt Johan , Høyland Knut Vilhelm
Published: November 2019

A model for the computation of failure probabilities for partly reshaping mass-armored berm breakwaters in the Arctic is presented. The model consists of a reliable tool for the design of port structures in the rapidly changing Arctic environment and considers the simultaneous effects of wave and ice forces.

The applied probabilistic approach was based on Bayesian inference. Hydrodynamic and ice historical data from Prudhoe Bay, Alaska were collected and analyzed to supply the Bayesian network with a large pool of information for the analysis. The model performed real-time predictions based on historical data and the user’s prior knowledge and assigned relevant values to load and resistance parameters. The predictive skill of the Bayesian network was validated with log-likelihood tests. Furthermore, the main outputs were applied for a Level III (fully probabilistic) reliability assessment of the structure.

The study shows that a well-formulated Bayesian network can be a powerful tool in the design process and for the purpose of reliability analysis of coastal structures in highly unpredictable environments, such as the Arctic. The model can represent the dependencies between wave and ice loads in relation to the characteristics of the breakwater, as well as, its response. The average deviation of computed probabilities of failure relative to the prior estimates was 58.7%.
Numerical Solutions and Model Test Design for Anti-Typhoon Drilling Riser
Authors: Wang Jinlong , Li Lihui , Lim Frank , Zhang Hui , Xu Liangbin , Sheng Leixiang , Jin Ruijia
Published: November 2019

Anti-typhoon drilling riser, a solution to overcome high time cost of offshore drilling riser emergency retrieval under the situation of imminent arrival of a typhoon, is to modify the existing drilling riser to make it disconnectable closer to the surface and leave the long riser string below (and subsea blowout preventer (BOP)) in a safe and freestanding mode to survive the typhoon. The freestanding riser is held up by a buoyancy can system. And during the normal drilling operation, the buoyancy can maintain neutral thus it has limited effect on the riser overall global performance. However, locally the buoyancy can system will have some effect on the riser system nearby. To study these effects, numerical analytical methodology and results of anti-typhoon drilling rise under connected mode and freestanding mode are proposed, and a model test of 1:21 scale factor is designed. Three configuration modes: freestanding mode, connected mode and disconnecting mode are simulated in the tank test. A series of load cases under various current and wave, buoyancy upthrust are conducted in the experimental test to evaluate the hydrodynamic and strength performance of the riser near buoyancy can. The numerical solution and model test design can be a significant basis of water tank test for anti-typhoon drilling riser and a valuable reference for deepwater drilling engineering.
An Energy-Maximising MPC Solution to the WEC Control Competition
Authors: Tona Paolino , Sabiron Guillaume , Nguyen Hoai-Nam
Published: November 2019

The WEC Control Competition is a benchmark devised to compare energy-maximising controllers for wave energy converters, first in simulation, then in real time, using a scale device in a tank test situation. For the first round of the competition, the evaluators have provided a model of a leg of a Wavestar-like device, in the WEC-Sim simulation environment. The evaluation is based on an energy-related criterion computed on six irregular waves.

IFPEN’s solution is an energy-maximising model predictive control (MPC), composed of an estimation algorithm for wave excitation force moment, using measurements (or estimations) of float displacement and velocity and PTO moment; an algorithm for short-term wave force prediction from present and past wave excitation force estimates, where no information about wave elevation is used; a real-time compatible MPC algorithm using wave force prediction, which maximises the average produced electric energy, taking into account the nonlinear PTO efficiency law.
The Aerodynamic Analysis of Helical-Type VAWT With Semi Empirical and CFD Method
Authors: Guo Ying , Liu Liqin , Lv Xinxin , Tang Yougang
Published: November 2019

Comparing to Φ-type and H-type VAWT (Vertical Axis Wind Turbine), the amplitude changes of the aerodynamics acting on Helical-type VAWT are much smaller, so Helical-type VAWT has advantages in steady output power and avoiding fatigue of structure. Considering the characteristic of helical-type VAWT, this paper modifies the semi empirical method of calculating aerodynamic loads and compares with CFD results. A comparison is presented between CFD results and experiment results to confirm the model used in CFD. Single parameter analysis and muti-parameters analysis are carried out to study the influence of structural parameters on the dynamic torque. Based on an objective output power as 5MW, the parameters of wind turbine are adjusted, and optimal values of these parameters are determined.
Numerical Modelling and Sensitivity Analysis of Gas Kick Migration and Unloading of Riser
Authors: Gomes Dalila , Bjørkevoll Knut S. , Fjelde Kjell K. , Frøyen Johnny
Published: November 2019

In deepwater wells there is a risk of gas entering the riser. This can be caused by gas being trapped by the BOP after a well kill operation, or it can be that the BOP was not closed quickly enough upon kick detection. With oil-based mud (OBM), gas is dissolved, and larger kicks may go undetected and circulated up in the riser by accident.

If a gas kick comes into the riser, a rapid unloading event can occur. This can in worst case lead to a blowout scenario. In addition, the riser may be subject to a collapse load due to reduced liquid level inside. The unloading behavior will be different when comparing kicks in oil-based and water-based mud (WBM).

For water-based muds, field experience and experiments have shown that gas can be trapped by the mud. This effect is the same that causes mud to capture cutting particles, and it is related to the non-Newtonian and time-dependent rheology behavior of the mud. The suspended gas can only be removed from the riser by circulation. The kick must therefore be of a certain volume to be able to unload the well.

Modelling of the mentioned complex phenomena, with the violent transient phase seen when a large volume of gas expands as it moves towards the liquid surface in the riser, is still a challenge for numerical algorithms to do accurately and reliably. Robust handling of numerical diffusion in two-phase flow is one of the key topics, as are slippage and extension of gas in the liquid.

The paper describes how an explicit numerical scheme (AUSMV) is used as a numerical solver with the application of the slope-limiter technique to handle numerical diffusion. This has not yet been done for unloading of gas in riser.

A simulation case will be constructed considering gas migration and expansion in a long riser. A sensitivity analysis will be performed where both the kick volumes and the threshold for gas suspension will be varied to study when kicks will start to unload the well vs. situations where they will become fully suspended. The phenomena mentioned will be studied for water-base drilling fluids.

The paper will review previous work on the subject and highlight how transient flow models can be useful for gaining more insight into how the gas behaves in risers and what can be done to mitigate the consequences.
Removal of Viscoplastic Gels From Conduits
Authors: Alba Kamran , Oladosu Olamide , Brown Paris , Bhakta Jai , Frigaard Ian
Published: November 2019

There exist many industrial processes in which it is necessary to remove a gelled material from a duct. Some examples include mud removal in oil and gas well cementing, waxy crude oil pipeline restarts, and Enhanced Oil Recovery (EOR). Here, the dynamics of the removal of a viscoplastic fluid by a Newtonian fluid are investigated experimentally in an inclined pipe. We focus on both miscible and immiscible fluids mimicking wells drilled using water-based as well as oil-based mud. Under the miscible limit two major flow regimes, namely center-type and slump-type, are observed depending on the density difference between fluids. These flows are explored in great details through displacement front speed measurement which is inversely related to the efficiency of removal process. Displacement flows in the immiscible limit are accompanied by interfacial instability, gel fracture, and droplet formation. These flows are quantified through flow visualisation and spatiotemporal diagrams of fluids concentration. The findings of our study can help improve well cementing operations worldwide.
Downtime Technique Using Artificial Intelligence: A Case Study for an Exposed Berthing Facility
Authors: El Chahal Ghassan , Morel Peter A. B. , Mole Sindhu , Saadali Nadjib
Published: November 2019

Hydrodynamic modelling is significantly improved in the last decade, however, the coupling of these hydrodynamic models with methods to estimate berth downtime due to environmental conditions (wind, waves, currents) is less developed. The large number of environmental inputs (wind speed, wind direction, wave height, wave period, wave direction, current speed, current direction) and mooring outputs (vessel motions in six degrees of freedom, mooring lines, fender forces) to be considered in a downtime study requires major simplifications as the full wind-wave time series cannot be calculated. Downtime assessment is normally simplified by calculating a limited number of wind-wave combinations.

A new approach is developed and presented in this paper by calculating the downtime for the long-term environmental time series using artificial neural networks. Neural networks are some of the most capable artificial intelligence tools for solving very complex problems like the present case. The approach has been applied for a bulk terminal project located in the Arabian Sea. The terminal has no shelter and is totally exposed to wind and swell waves. The wave climate for a 15 years period is established at the project site using spectral wave modelling software MIKE 21 SW. A large set of combined environmental conditions is selected for the dynamic mooring analysis of the vessel at berth. The time domain mooring analysis software MIKE 21 MA is used in this study. An inhouse Matlab code/program is developed using neural network to calculate the downtime for the long-term environmental time series based on the dynamic vessel response for the set of selected environmental combinations. This approach provides a more accurate downtime estimate which is important for the operability of such exposed facilities. The downtime tool is also tested for a different set of environmental combinations and mooring layouts in order to assess the sensitivity of these parameters on the downtime estimate.

Up to the authors’ knowledge, this is the first published work applying artificial intelligence techniques for downtime studies.
Wave Load and Response Predictions Combining HOSM, CFD and Machine Learning
Authors: Oberhagemann Jan , Kaufmann Jan , Ervik Anna Kringlen , Gramstad Odin , Helmers Jens Bloch , Sireta Francois-Xavier
Published: November 2019

We present efforts to progress on numerical predictions of extreme wave loads of ships by combining a variety of state-of-the-art numerical tools. Aims are the generation of wave scenarios to represent the wave excitation and corresponding structural response associated with a pre-defined probability of, e.g., one expected exceedance per life cycle, as well as the further development of numerical methods to predict the ship response to the selected wave events.