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This paper was erroneously published in ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition, Vol. 2D and removed on October 13, 2021. Copyright © 2021 by ASME

This paper was removed from publication at the author’s request, August 30, 2021. Copyright © 2021 by ASME

The above referenced paper has been removed from publication. (April 21, 2020) Copyright © 2020 by ASME

This erratum corrects errors that appeared in the paper “Analysis of the Performance of Plasma Actuators Under Low-Pressure Turbine Conditions Based on Experiments and URANS Simulations” which was published in Proceedings of ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition, Volume 2A: Turbomachinery, V02AT40A034, June 2017, GT2017-64867, doi: 10.1115/GT2017-64867.

The above referenced paper has been removed from publication. June 29, 2017. Copyright © 2017 by ASME

The growing size of BOPs, longer drilling campaigns on wells, and operations in harsher environments has resulted in increased challenges in properly documenting wellhead fatigue during planned or executed drilling operations. The industry has started directing its efforts toward the calibration of analytical tools which are typically adopted for predicting wellhead fatigue. The ultimate goal for achieving this ambitious scope is to identify a benchmark set of analytical results that will predict field measurements. Early on Statoil identified a major obstacle: the absence of a good and comprehensive dataset of field measurements to serve as point of reference. Statoil and Aker Solutions cooperated on a pilot project with the intent of collecting a dataset of full scale measurements during drilling operations to be used to validate and calibrate the theoretical wellhead fatigue calculation methodologies. The main objective of the instrumentation campaign was to measure sectional forces as close as possible to typical wellhead hotspots by the use of three sets of strain gauges installed on the outside surface of the conductor and on the outside of the surface casing. With the objective of collecting an exhaustive dataset of measurements, accelerometers and inclinometers were installed on the BOP, the riser adapter, the riser below the upper flex joint and on the rig. An additional set of six strain gauges was installed on the riser to record riser tension variations. Environmental conditions were logged on board the rig and by the hindcast data provider. Operational events were carefully logged. This paper presents the following: • Data processing used for quality assurance and calibration of the measured data and the associated data challenges • Highlights of the instrumentation system capabilities to capture salient events of a typical drilling campaign and of ad-hoc performed rig operations to calibrate and validate the measured data • Effect of a controlled rig cross motion test, performed to evaluate quasi static loads on the well and calibrate strain gauge sensor orientations • A riser pull test, performed to validate strain gauge functioning • Several landing and disconnecting of the LMRP • Manipulation of the preload between the high pressure housing and the low pressure housing to investigate the effect of the preloading on the load sharing between the casings Since King and Soloman [2], the industry is still lacking quality field data to be used in order to validate the various analytical models used in the analyses of subsea conductor and wellheads. The results will confirm the quality of the measured data and will represent a first data point of comprehensive measured field data. This data will be used for future required work in calibrating the different building blocks pertaining to the analytical tools dedicated to well head fatigue predictions [3].

This erratum corrects errors that appeared in the paper “A Simple Method for the Prediction of Wall Temperatures in Gas Turbines”, which was published in Proceedings of the ASME 1978 International Gas Turbine Conference and Products Show, Volume 1A: General, V01AT01A090, April 1978, 78-GT-90, doi: 10.1115/78-GT-90. This paper was originally published in 1978. There were numerous equation errors due to the typesetting limitations which have been corrected. The references have also been updated to contain additional information. Reference 12 is a duplicate of reference 10 and has also been removed.

A riser is a key component for transporting produced oil and gas from the subsea wells to the surface production vessel. Through nearly 30 years of design and implementation, Steel Catenary Risers (SCRs) have been found to have the advantages of relatively low cost and good adaptability to floating platform’s motion. This paper investigates deepwater SCR system design for the Lingshui 17-2 (termed LS17-2) project. This paper first introduces a SCR system for the LS17-2 project. The field for this project is located in the northern South China Sea, with water depth of 1220m to 1560m. LS17-2 consists of a subsea production system, a deep-draft semi-submersible (SEMI), and an export riser/pipeline. The platform was designed to have a large storage capacity with a variable draft during its operation. Based on deepwater SCR engineering experience, the key SCR design challenges are summarized from the engineering executive perspective. The challenges to the SCR system design for the LS17-2 project include harsh environment condition in South China Sea and the impact on fatigue design for the requirement of 30-years’ service life. They call for design optimization and innovative ideas. The engineering design and analysis are discussed together solutions. To demonstrate the deepwater SCR system design for LS17-2 project, examples are provided to illustrate the challenges and solutions. The experience learned from this paper should have significant relevance to future SCR design.

At least 10 girth weld incidents in newly constructed pipelines are known to have occurred in North America. More than 30 girth weld incidents in newly constructed pipes have been identified worldwide. A review of the North American incidents identified a few main contributing factors: (1) weld strength undermatching, (2) heat-affected zone (HAZ) softening, and (3) elevated stresses/strains from normal settlement and other loads. Weld bevel geometries of manual welding processes that favor plastic straining along the softened HAZ and low strength root passes were also compounding contributing factors. Prior publications focused on the industry practices that led to the formation of those contributing factors. This paper covers the enhanced linepipe specifications and improved welding practice that aim to reduce the risk of similar girth weld incidents, thus leading to more resilient pipelines. The enhanced linepipe specifications include interim recommendations that aim to limit the upper-bound longitudinal strength for a given pipe grade and reduce the linepipe steels’ susceptibility to HAZ softening. The implementation of the interim recommendations is assisted by allowing alternative hoop tensile tests. The improved welding practice includes (1) the selection of welding procedures, including consumables, that minimizes the likelihood of weld strength undermatching and reduces the propensity for HAZ softening and (2) welding procedure qualification tests and requirements for the production of strain-resistant girth welds. The recommendations covered in this paper principally target new pipeline construction projects but are also applicable to pipe replacement projects. It is expected that pipeline operators would incorporate the recommendations in their internal procedures and work with welding contractors to execute the recommendations. The improved linepipe specifications and welding practice are expected to increase the resilience of pipelines subjected to realistic construction and in-service loads. The implementation of the recommendations requires changes to some long-standing industry practices and can only occur with collaborative efforts from all stakeholders.

This paper discusses the design and conceptualization of a novel robotic mechanism to clean the trench drains. It describes a different approach for drain cleaning with lesser human intervention and more safety to personnel involved. The robot is designed and built to be 4 inches in width and operate entirely within the limited space inside the drain. To achieve a wholesome cleaning process, the entire robot is modular in design and consists of a drive system, a suction tube and a cutting arm assembly with metal brushes installed onto it. The bidirectional drive system enables the robot to move through drain segments repeatedly for optimal performance. The purpose of the cutting arm assembly is to aid the removal of dirt from the drain. In order to improve the robot performance, two prototypes were designed and built. The overall design and modularity of both robot prototypes will be discussed in detail in the paper.

Test facilities capable of simulating relevant operational environments for validating novel concepts are indispensable for advancing the state-of-the-art in turbomachinery sealing technology. A test rig suitable for demonstrating full-scale rotor-stator sealing concepts under operational environments relevant for a variety of turbomachinery gas paths was designed and commissioned at GE’s Seals Test Facility. The test rig, called the Advanced Seals Test Rig (or ASTR), can simulate conditions that include a range of rotor speeds, fluid pressures and temperatures, from steady state operating conditions of high pressure turbines of aircraft engines to sections of steam turbines. The present paper provides a system level description of the test rig. The main test section of the rig is housed within the centerpiece of a stamped pressure vessel. A drive train penetrates the pressure vessel and consists of an integral saddle mounted rotor. A motor connected to a high-speed gearbox through couplings on each end permits rotation of the test rotor. The test rotor is supported by two bearing pedestals. The paper describes these rig subsystems with focus on novel features for ease of operation. Key instrumentation and operating procedures that enable the rig to operate safely are also described. Key drivers of the rig design, such as test requirements, rotordynamics, mechanical design, ergonomics, safety and test productivity are outlined. Mechanical design considerations include strict requirements for thermal and pressure deformation under demanding conditions of pressure and temperature. Commissioning of the rig included phases of fabrication, installation, shakeout, calibration and benchmarking. Key learnings from the rig design and commissioning process, as well as operations, are summarized.

Subsea rigid jumpers are designed to meet numerous criteria including thermal and pressure effects, environmental and riser / pipeline interaction loads, slugging, and other field specific requirements. Jumper VIV can be a concern in fields with strong bottom currents. Without the benefit of detailed VIV fatigue analysis, designers must rely on experience and engineering judgement on placement of strakes if VIV is identified as a concern. VIV mitigation is even more challenging because the jumpers can contain numerous long and short design options to accommodate tolerances for subsea well locations and installation tolerances of subsea PLETS and manifolds. This paper will discuss a case study on optimization of 12 M-shaped jumpers designed for a sour service application in Gulf of Mexico. VIV fatigue assessment of the preliminary jumper design and the methodology adopted to optimize the jumper design and placement of VIV suppression will be discussed. Challenges in meeting high target fatigue life due to sour service application will be discussed. The key challenges whilst optimizing an acceptable VIV suppression solution are the assumed effectiveness of strakes, cost / available inventory of strakes, and physical limitations for placement of strakes. This paper will highlight the trade-offs that are required to strike a balance between strength and fatigue design requirements when using straked buoyancy modules vs. regular strakes. The paper will also highlight the current limitations in design code that relies on standards developed for pipeline application. An alternative method / modification to the DNV F105 approach used to calculate the cross-flow induced in-line VIV fatigue damage is also discussed.

The steel lazy wave riser has been used in deep-water oil and gas field development because it has good adaption to the movement of the upper platform and economic efficiency. The typical design criterion and design flow of steel lazy wave riser are introduced in this paper. The design method and the equivalence principle of distributed buoyancy modules are given. The formulas of equivalent hydrodynamic parameters are derived in this paper. The influences of distributed buoyancy modules (DBM) and the buoyancy factor on the configuration of the riser, the top tension, and the bending moment distribution are discussed and summarized. The distribution law of effective stress response along the pipe can be analyzed by dynamic analysis, and it provides reference for the global design of steel lazy wave riser.

The paper is part of the European research program JABACO (2015–2018), on the optimization of design and construction of offshore jacket platforms for supporting large wind turbines (5–10 MW) in water depths ranging from 30m to 80m. In particular, the paper describes an experimental investigation on the high-cycle fatigue performance of welded tubular connections, subjected to in-plane bending loading. Experimental results from seven (7) X-joint specimens are presented. The specimens were manufactured with 18-inch-diameter tubes and a brace-to-chord-diameter ratio equal to 1. Furthermore, the brace-to-chord-thickness ratio is equal 0.6, and the brace-chord angle is 90-degrees. The specimens are made of regular carbon steel grade 355, and have been fabricated using two different welding techniques: (a) manual (semi-automatic) welding (5 specimens); and (b) robot (automatic) welding (2 specimens). The comparison of the fatigue design life of those welding methods is a major objective of the present study. Prior to testing, numerical simulations have been performed to determine the critical locations around the weld toe, for proper instrumentation of the tubular specimens in terms of strain gage locations. This research work aims at a critical evaluation of available design standards, towards the development of more reliable design tools and reduction of the construction cost of the platform.

The mooring system for a floating offshore wind turbine ensures that the platform stays within pre-defined station keeping limits during operation, while it provides sufficient restraining forces in storm events to guarantee survival. This presents a challenge during the design process, since the cost of the mooring system is proportional to the peak loads, i.e. those that occur infrequently in extreme conditions. Mooring designs are governed by extreme and fatigue loads which determine the required Minimum Breaking Load (MBL) of the system. If uncertainties in the environmental loading or hydrodynamic coupled response exist, additional safety factors are required. This paper explores the application of a hydraulic based mooring system that enables a variable, non-linear line stiffness characteristic that cannot be achieved with conventional designs. This non-linear load-response behavior could function like a ‘shock absorber’ in the mooring system, and thus reduce the line tensions, enabling a more efficient mooring system that necessitates a lower MBL and thus lower cost. These claims are evaluated through numerical modelling of the NREL OC3 spar buoy and OC4 semi-submersible offshore wind platforms using the FAST-OrcaFlex interface. The simulations compare the dynamics with and without the inclusion of the hydraulic mooring component. The results suggest that mean mooring line loads can be reduced in the region of 9–17% through a combination of lower static and dynamic loads, while the peak loads observed in extreme conditions were reduced by 17–18%. These load reductions, however, come at the expense of some additional platform motion. The paper also provides an outlook to an upcoming physical test campaign that will aim to better understand the performance and reliability of the mooring component, which will provide the necessary evidence to support these load reduction claims.

Crop phenotyping is frequently used by breeders and crop scientists to monitor growth of plants and to relate them to plants genotypes. Seemingly, this contributes to better crop growth and results in higher yield. Instead of traditional crop monitoring, which is labor intensive, high-throughput phenotyping (HTP) platforms using ground-based vehicle have several advantages (in speed, efficiency, and cost) over manual methods. A wheeled mobile platform for HTP was developed, and automated data collection were performed for different traits of canola and wheat. These data were compared with manual measured data. In this paper, vibration analysis of a relatively long cantilever boom attached to a vehicle is reported. The paper investigates how different factors influence the boom attached to a regular farming machine, its vibration, and effects on phenotyping sensors attached to the boom.

As a major resource for electricity, hydropower is widely used around the world for renewable energy. Traditionally, large high-capital cost dam equipped with large turbine system is preferred to produce sufficient power supply. However, recently large hydropower system is questioned because of the impact of dams on the local environment, which could be a major barrier for development of large hydropower system. Besides, billions people remain without access to electricity and most of them are in remote and rural location where is not suitable for large hydropower system. Therefore, the utilization of ultra-low-head (ULH) water energy (situations where the hydraulic head is less than 3m or the water flow rate is more than 0.5m/s with zero head) has becomes more attractive. Part I of this paper focus on developing a design methodology for a low-impact, damless Kaplan turbine system for ULH water resource. Part II of this paper focus on providing detailed CFD simulations to demonstrate that this methodology is valid and effective.

In the field of underwater robotics, Autonomous Underwater Vehicles (AUV) have made many advancements in operating depth, mission endurance, and acoustic range making them the ideal vehicle for surveying and searching for any Object of Interest (OOI) over large areas of water. The downside to this technology is that the operator must wait for the vehicle’s mission to end to determine whether an OOI has been identified. Additionally, if an OOI is identified this object will need to be found again. The solution to this lengthy process is to equip the AUV with a suite of Underwater Locator Beacons (ULB) which can be deployed and anchored next to any positively identified OOI. This way, the operator can be actively listening for the pinging frequency of a deployed ULB where then a secondary Remotely Operated Vehicle (ROV) can be launched to retrieve or further investigate the OOI while the AUV continues its search and tag. This paper presents the design and test of a ULB deployment system that would be implemented into an AUV. An AUV is sensitive to changes in weight, therefore this novel design leverages the concepts of Archimedes Principle by preserving neutral buoyancy pre- and post-deployment of the ULB. Upon deployment, the ULB will be capable of securely anchoring itself in a wide range of seabed environments. To test the design described above, a custom ROV has been fabricated with the sole purpose of transporting the ULB deployment system to operating depth. The paper describes in detail both the test results from the ULB deployment system and a design for implementation into an AUV.

Wheel design and wheel rotation have been identified to be key factors influencing the overall aerodynamic performance of passenger cars. Hence, wheel aerodynamics has been the topic of various studies over the past few years. Recently, vehicle manufacturers have moved towards time-resolving CFD simulation methods. Therefore, a trend towards resembling the physical effect of wheel rotation by utilizing the Sliding Mesh Method can be observed in academia and the industry. The first part of the presented paper shows the results of CFD simulations using the Sliding Mesh Method on two generic test cases employing the Delayed Detached Eddy Simulation turbulence model. A rotating cylinder is investigated as well as a rotating wheel geometry, both in ground contact and lifted from the ground. The results show dependencies on the solution algorithm and the background turbulence model applied within the RANS region of the Delayed Detached Eddy Simulation model. The prediction accuracy of the CFD setup is assessed by comparing the results to experimental results on the rotating wheel geometry with ground contact obtained in a model scale wind tunnel. The second part of the paper focuses on the influence of the rim design on the aerodynamics of a full vehicle. Four rim geometries are investigated regarding their aerodynamic influence on the DrivAer reference body by CFD simulations using the Sliding Mesh Method. The DrivAer has recently been updated to include an engine bay geometry. This new version of the DrivAer is used for the presented study because the engine bay flow is expected to have a considerable influence especially on the flow around the front wheels. The simulation results are compared to experimental results obtained on a 1:2.5 scale model of the DrivAer with engine bay flow and are in good agreement.

Secondary flow injection is a way which allows for the efficiency of a turbomachine to be increased further, after blade design optimizations have already been performed. In this paper, a novel method in improving turbine performance using secondary flow injection through an injection slot over the turbine shroud is investigated. A steady state numerical analysis of a low pressure mixed flow turbine was conducted. A baseline model without the injection slot was first validated against existing experimental data and reasonable agreement was found between the experiment and simulation results. Then, the shroud of the turbine was modified to include an injection slot from which a secondary injection flow enters and exits the turbine. The simulations were performed at a rotational speed of 30,000 rev/min, and the main performance parameters monitored are: total-to-static pressure ratio, non-dimensional mass flow parameter, isentropic velocity ratio, total-to-static isentropic efficiency, and blade torque. The effects of injection mass flow and direction were studied, and the parameters varied were the injection mass flow and yaw angle. The results show that generally, injection increases the power output of the turbine, although the power input of the injected fluid cancels out the power gain and results in no significant net gain in efficiency. The largest turbine power and efficiency gains were obtained at operating points with high isentropic velocity ratio. Also, the yaw angle of the injection had a significant effect on both turbine power and efficiency. However, when injection mass flow is reduced accordingly to maintain the same injection velocity at different yaw angles, the effect of injection yaw angle was smaller, suggesting that injection velocity might be a dominant factor in changing turbine performance. Flow visualization and blade loading diagrams show that injection has two main effects on the flow. Firstly, it energizes the leakage vortex which travels close to the suction surface, improving blade tip loading. Secondly, if injected with a significant circumferential velocity in the same direction of the blade rotation, the injected flow increases blade torque directly by entraining fluid near the blade tip to ‘push’ the blade, but this pushes the leakage vortex away from the suction surface as well. Overall, secondary injection at a yaw angle of 60° can provide an overall work increase of up to 11.4 percentage points over the baseline model, while injection at 45° yaw can provide up to 1.9 percentage points increase in efficiency at high velocity ratios. If the injection can be performed without any additional system power input, the net performance improvements can be very significant. Indeed this concept could represent a valid solution to recover exhaust gas which are discharged through the wastegate valve without contributing to any additional performance/power output improvement; the results obtained are explained and discussed in detail in the paper.

The United States Navy has successfully operated their Landing Craft Air Cushion (LCAC) with Vericor’s ETF40B engines since 2001. The engines interface with the craft drivetrain through sprag clutches, which engage when the engine output is greater than the drive shaft speed. Historically, sprag clutch failures have been observed on multiple LCACs, resulting in craft downtime and associated repair & replacement costs. Subsequently, a US Navy investigation revealed the presence of high frequency, low level fluctuations in the shaft rotational speed when operated at steady state conditions. The study also suggested that the speed governor fuel control could excite these fluctuations and induce sprag clutch failure. The original speed governor gains were tuned for maximum transient performance, but not necessarily steady state stability. The aggressive gain selection resulted in a governor response that could be characterized as “hyper-reactive” where the system was willing to respond to even the slightest disturbance, including common drivetrain noise. The US Navy requested that Vericor modify the Full Authority Digital Engine Controller (FADEC) speed governor logic to improve steady state stability while maintaining an acceptable transient response. This paper summarizes the basics of ETF40B operation on the LCAC and describes the effort that improved the governor response. As of the writing of this paper, two (2) years have passed in which no sprag clutch failures have been observed on US Navy LCACs operating with the optimized speed governor.

A key aspect in the design of a mooring system for a floating production unit is the estimation of the extreme mooring line loads for a specified short-term sea state of typical duration equal to 3 hours. Commonly used design approaches today are based on time-domain simulations whereby each 3 hour sea state is run a number of times (typically 10–30 times) to represent the randomness of the sea. A maximum response is recorded from each simulation. Particular statistic of the maxima data (e.g. mean, most probable maximum or a percentile) is used to represent the extreme mooring load for which the lines are designed. This paper studies and assesses the accuracy of obtaining design value from a population of maxima with reference to the mooring line load of a large ship-shaped floating production vessel. A coupled model, including all mooring lines and risers, has been developed, validated and used to generate responses for 100yr extreme condition and 10,000yr survival condition. To establish an accurate benchmark against which the results are compared, the time-domain analyses (duration 3 hours) are repeated 170 times, for each sea state, to represent different random realisations of each environment. It is examined how the accuracy of predicting the design mooring line load, from a sample of response maxima, improves as the number of simulations is increased progressively from 10 through to 170. The assessment is performed across different statistics of maxima that are usually chosen to represent the design response. Besides the mooring line load, other response parameters such as heave and turret excursion, are examined in this paper. The paper examines whether the severity of the response (100yr vs 10,000yr storm) or the response variable affect the number of maxima required to achieve statistical stability. The results indicate fitting a Gumbel distribution to the maxima from about 30–40 simulations can yield results that are statistically stable and accurate and are recommended as preferred methods of estimating the design response.

An increasing use of submarine power cables is found in dynamic applications such as floating wind, floating wave and tidal generation technologies. These applications substantially differ from common applications, such as floating oil and gas installations in that they are more dynamic. Power cables that cross the water column, so-called umbilicals will be exposed to considerable extreme and fatigue loads mainly induced by the motion of the device, incident waves and tidal current. The actual loading regimes of dynamic submarine power cables in operation are not well understood for marine renewable energy (MRE) applications due to a lack of field experience. The cable design has to consider a combination of cable geometry, hydrodynamic parameters, suitable layout configuration, suitable ancillary systems (e.g. bend stiffeners) in relation to the environmental site conditions. This paper evaluates the influence of the environmental conditions and the cable design parameters on the mechanical loads and potential failure modes of a dynamic submarine power cable attached to a dynamic floating body in form of a generic point absorber. One notable result is the large effect of the tidal direction, even in relatively moderate flow conditions. The full range of tidal flow conditions should be considered in the power cable design to ensure that the cable MBR is not exceeded in any conditions. The shown configurations also give some insight into the possible variations of the geometric cable configuration. A well balanced S-curve shape yields some of the best results and achieves a good load distribution along the cable and the transition points, whilst avoiding cable compression. The design challenge for the cable configuration is to maintain the S-shape for as many environmental and device response modes as possible in order to achieve high reliability. This paper will be useful for cable, device and site developers of floating MRE to inform the selection of the most suitable cable design.

Over the last decades, the complexity and duration of offshore drilling operations have steadily increased. The size and weight of the risers and BOP stack has grown significantly. These factors have led to an increase in fatigue loads imposed on the wellhead structures during drilling and completion operations. Wellhead fatigue might ultimately lead to loss of well structural integrity and pressure containment and therefore safe and reliable drilling of subsea wellheads has gained high priority in the global oil and gas industry. This paper presents two of the most complex real time instrumentation campaigns for drilling operations. Analyses of a connected drilling riser system including the well structure are complex and involve several engineering disciplines. In addition, there are many unknowns going into the equations when accumulated fatigue damage of the wellhead is estimated. Therefore, assumptions need to be made, very often on the conservative side. A typical example are the global drilling riser analyses where the environmental conditions, actual rig motion and riser / BOP behavior are uncertain. With the duplex scope of accurately documenting the wellhead fatigue status during drilling operations and of achieving a better understanding of the actual risk level of wellhead fatigue, Statoil decided to start a very comprehensive monitoring campaign. Two MODU representing very different generations of rigs in terms of weights and types of equipment were instrumented from topside to BOP connector. Strain gauges were installed around the BOP connector as close as possible to the wellhead in order to capture wellhead response as accurately as possible. Due to the large number of sensors, high accuracy requirement and high sampling frequency of data to be shown live, a cabled solution was selected vs remote battery operated sensors transmitting via acoustic. Double set of cables, sensors and topside equipment were installed in order to make the instrumentation system fully redundant and suited for permanent installation. All data were additionally made available real time onshore to allow the full overview of the operation. To author’s knowledge, these two instrumentation systems are the most comprehensive and complex of this type installed on a drilling riser as of today. The first of the two system was installed approximately three years ago and it is still in operation. This paper describes the instrumentation systems installed and gives an extract of the quality data extracted and already used in already published studies [1, 2, 3].

For merchant vessels full scale resistance is determined by extrapolating the towing tank tests using Hughes’ method. For blunt and simple shapes this approach might not be valid due to significant Reynolds dependency. In this paper a study is presented on two semi-submersible pontoon shapes and one drillship. The resistance for these hulls was calculated using URANSE simulations. Four different scales: 1:1, 1:10, 1:20 and 1:40 were investigated for all the different hull shapes. The goal of the study was to determine a form factor to use when scaling towing test results to full scale. However due to the simple shapes of the pontoons it was found that there was a significant Reynolds dependency at all the different scales. This Reynolds dependency had much more influence on the full scale resistance than a form factor. For the drillship no significant Reynolds dependency was found and applying ITTC 1978 method [1] with a form factor improved the accuracy of the resistance prediction compared to using the Froude method which is not using a form factor. The simple pontoon shapes used were based on a combination of boxes, cylinders and spheres. The cylindrical and spherical shapes have a Reynolds regime where a drag crisis occurs. For all the shapes the drag crisis regimes were right in the same Reynolds number range at which typical model tests would be performed. Therefore performing towing tests and making accurate full scale resistance predictions for these simple shapes is not straightforward. Applying the ITTC 1978 method does not provide the same level of accuracy as it does for merchant vessels. The paper identifies limitations involved in scaling towing test results for typical offshore hull shapes. Further possible solutions are proposed to improve the accuracy of the resistance predictions.

In this paper, numerical modelling and analysis of a hybrid-spar floating wind turbine is presented. The hybrid-spar consists of steel at the upper part and the precast prestressed concrete (PC) at the lower part. Such a configuration is referred to as a hybrid-spar in this paper. The hybrid spar was successfully installed offshore of Kabashima Island, Goto city, Nagasaki prefecture, Japan on October 18, 2013 (see OMAE2015-41544 [1] for details). In this paper, some details on numerical modelling of the hybrid-spar for design load analysis are presented. Then, the validation of the numerical analysis model is presented for a full-scale hybrid-spar model with 2-MW wind turbine.

Fatigue occurs in structures due to the stresses from cyclic environmental loads. Offshore environmental loads being highly cyclic and recurring in nature, fatigue analysis with high degree of accuracy is required for reliable and optimized design of offshore structures. The main aim of this paper is to automate the process of identification of fatigue critical tubular joints of an offshore jacket structure using deterministic fatigue analysis with emphasis on the Hot Spot Stress Range (HSSR), an important measure in estimating fatigue damage, calculated using three different approaches for each tubular joint. The first approach determines HSSR at the time of maximum base shear of the jacket, the second, by calculating the difference between maximum and minimum Hot Spot Stress (HSS) and the third, at all time-instants of the wave cycle. Thus fatigue damage and fatigue life of the tubular joints are estimated using the highest HSSR value and the joints with lower fatigue life are identified as fatigue sensitive joints. This ensures effective identification of critical tubular joints of the offshore jacket structure which needs detailed investigation or redesign for fatigue. The deterministic approach discussed in this paper is applicable to large jackets which contains more number of tubular joints where sophisticated fatigue assessment at the preliminary stage is computationally intensive and manual identification of fatigue critical joints is laborious.

Current methods for installation of offshore wind turbines are all sensitive to the weather conditions and the present cost level of offshore wind power is more than twice the cost of land-based units, increasing with water depth. This paper presents numerical simulations of a novel experimental gripper design to reduce the environmental effects applied to a catamaran type of vessel during wind turbine installation. In SFI MOVE project in NTNU Aalesund, our team proposed a novel wind turbine installation process. A new catamaran vessel will carry pre-assembled wind turbines to the installation location. Two new designed grippers on the deck will make a lifting operation to install the wind turbine onto the turbine foundation. Three prismatic grippers with several rolling contact points at the end are attached in an arc at the catamaran’s aft, designed to grasp the turbine foundation in order to make a connection between the two in the horizontal plane. This paper will only emphasize the contact responses between the turbine foundation and the three grippers during the wind turbine installation process. Numerical simulations are carried out using the virtual prototyping framework Vicosim which is developed by NTNU Aalesund. The simulation results show validation of a key part of the proposed new wind turbine installation idea.

Subsea exploration well systems are subjected to complex loading due to vessel motion and hydrodynamic forces on the riser. In design of the wells, both the ULS/ALS design under extreme loading and fatigue design under operational loading are heavily dependent on the soil support along the uppermost 20 m of the conductor casing. In today’s practice, design of the conductor against extreme loading is typically performed using the soil reaction curves (p-y springs) recommended in API RP 2GEO [1]. In recent years, 4Subsea have been monitoring the BOP and riser responses during exploration drilling campaigns for Lundin Norway. The purpose of these monitoring campaigns is to track the performance of the wells with time, based on integrity parameters such as well stiffness, BOP resonance frequency and BOP motion rotational depth. This paper summarizes the monitoring results from seven well locations in the North Sea and the Barents Sea. The observed well response is compared with up-front design analyses. The discrepancy between up-front design analyses and the observed performances is discussed in light of the uncertainties associated with the geotechnical input parameters and soil reaction models. The purpose of the paper is to reflect on the challenges faced with exploration well design and highlight areas that improvements can be made.

Station-keeping is one of the important factors in the design of offshore platforms. Some offshore platforms, such as Spar, Semi-submersible and FPSO, use mooring lines as a mean for station-keeping. Tensions in the mooring lines are one of the key factors in station-keeping. The design of an offshore platform and its mooring lines is based on computed motions of the platform and associated mooring line tensions from numerical simulations using a software code on the basis of metocean criteria. This paper presents an Artificial Neural Network (ANN) model for the prediction of mooring line tensions based on the motions of the platform. This ANN model is trained with time histories of vessel motions and corresponding mooring line tensions for a range of sea states from the results of numerical simulations. After the model is trained, it can reproduce with great fidelity and very fast the mooring line tensions. In addition, it can generate accurate mooring line tensions for sea states that were not included in the training, and this demonstrates that the model has captured the knowledge for the underlying physics between vessel motions and mooring line tensions. The paper presents an example of the training and the validation of the model for a semi-submersible offshore platform for a range of sea states. The training of the ANN model employed a back-propagation learning algorithm. In this algorithm the computed output error is back-propagated through the neural network to modify the connection weights between neurons. The training started with a small number of hidden neurons, and the model grew adaptively by adding hidden neurons until either the target output convergence is achieved or a maximum number of additional hidden neurons is reached. The ANN model discovers nonlinear relationships between the input and output variables during training. The paper presents comparison of time series of mooring line tensions for sea states that were and were not included in the training between those from the numerical simulations and those computed by the trained ANN model. Fatigue assessment is also used to quantitatively measure the accuracy of the ANN model prediction of the time series of mooring line tensions. The paper presents the results of fatigue assessment using various stages of the ANN models with different number of hidden neurons. This shows that the additional hidden neurons improve the prediction of the ANN model of the mooring line tensions for sea states that were and were not included in the training. This approach of prediction of mooring line tensions based on vessel motions using ANN model paves the way to the development of an ANN-based monitoring system. Also, this ANN study demonstrates a great potential for the use of a more general and comprehensive ANN model to help monitor the dynamic behavior of floating systems and forecast problems before they occur by detecting deviations in historic patterns.

Direct Electric Heating (DEH) is an increasingly attractive method for flow assurance that has been in use for more than 15 years. All current systems in operation consist of a single flowline or have subsea architecture such that interaction between systems as well as components in the proximity is limited. DEH is selected as flow assurance for two ongoing field developments where the layout is such that there will be interaction with other subsea architecture. One system has numerous flowline systems in close interaction and the other has unfavorable crossing. This paper presents some of the design aspects which do arise for fields where the flowlines are in close proximity to each other. The paper also discusses how to handle interference with existing infrastructure when installing DEH in a complex field layout. The aspects studied are effect on power rating, ac corrosion and thermal rating of cables and flowlines.

Renewable energy technologies are a growing subject of concern these days. Wind energy is one among the renewable energy sources which has been implemented in a large scale for energy production. A large amount of capital has been invested in this field to harness energy and power homes. Wind energy from highways is usually unused and can provide a considerable amount of wind energy to drive a turbine due to high vehicle traffic and the speed of the vehicles. Extensive research on wind patterns is required to determine the average velocity of the wind created by oncoming vehicles. The objective of this work is to design and analyze a horizontal axis wind turbine to capture wind energy from moving vehicles on the highway. A computational fluid dynamics approach is used to solve this problem. The major innovation in this paper is that wind energy is being harvested in a very unique manner and also turbine power calculations have been done to quantify the amount of energy being harvested. Although a few of the literatures have discussed similar ideas power quantification has never been done. Also the entire mechanism has been simulated in MATLAB to find out the number of cars required to charge a battery which is very unique to this paper. Power calculations have been done for the turbine and validated against theoretical calculations which were done using the concept of velocity triangles. The idea is to have a separate mounting for cars and heavy vehicles which can be realized by having separate lanes on highways. The analysis will be done for vehicles moving in a range of speeds on the highway. The wind turbines will be placed on overhead shafts (the height of which is be determined suitably) thereby capturing the wind generated as a result of pressure difference. The mounts can also be used as signboards for vehicles moving on the highway and hence serve a dual purpose. In addition, extensive structural and fatigue analysis will be done for the turbines and the mounting structures in order to determine a suitable material for the turbine as well as the mounts to withstand the forces generated. Using all of the collected energy, existing amenities such as street lights on the medians can be powered by these wind turbines. Thus the main objective of this work is to complement the conventional electrical energy used for powering amenities along highways by a renewable source of energy (wind power) thereby leading to the concept of sustainable highways.Copyright © 2016 by ASME

Buried pipeline heat transfer modeling has become an important topic in the Oil and Gas industry. The viscosity of fluid i.e. crude oil travelling through the buried pipeline largely depends on the flow temperature and pressure. The aim of this paper is to give an overview of designing the experiment for heat loss from offshore buried pipelines and validation of the experimental model using analytical solution and CFD modeling. Several benchmark tests have been performed to ensure the validity of the test using theoretical shape factor models which depend on the amount of heat flow, thermal conductivity and geometry of the surrounding medium. This theoretical model has limitations such as the assumption of uniform soil properties around the buried pipeline, isothermal outer surface of the buried pipeline and soil surface. This paper illustrates several steady state and transient experiments to simulate the mechanism of heat loss from an offshore buried pipeline along with the experimental procedures. This paper also shows the transient response for shutdown tests performed in dry sand medium with numerical runs as well. With the progress of the research, several investigations will be made using different burial depths and diameters of the buried pipeline with backfill materials and trenching for different soil conditions, affecting the actual behavior of the model.

This paper presents the transference of a well-established nuclear power industry technique to perform environmentally-assisted fatigue monitoring for application to offshore, subsea High Pressure, High Temperature (HPHT) components using existing instrumentation. Applying fatigue monitoring is an effective way to manage these assets against the threat of fatigue failures and meet regulatory expectations during the service life. Our objective is to provide the background and overview of the approach so that design engineers better understand and evaluate its potential in contrast to traditional design changes that may actually produce an unintended consequence that increases the fatigue potential associated with heavy section thicknesses. This paper describes the overall analysis approach that may be used to perform fatigue monitoring of an HPHT component. At the conclusion, recommendations are provided for further research and development to close existing gaps.

It is a common challenge for pressure vessel and foundation engineers to determine the effects of piping loads on the foundation and vessel support design and to find out the appropriate design method to be used. Pressure Vessel Codes specify loadings to be considered in the vessel design but limited guidance is provided on the application of piping loads when designing vessel supports. Consideration of piping loads in the design of vessel supports and foundation is left to the engineer’s judgment. Vessel supports are typically designed to withstand the operating weight of the vessel, seismic and wind loading. Pressure vessel literatures provide well-established methodologies in considering these loads in the design of vessel supports. Civil engineering literature, such as the American Society of Civil Engineers (ASCE) Wind Loads for Petrochemical and Other Industrial Facilities [11] or the ASCE Guidelines for Seismic Evaluation and Design of Petrochemical Facilities [17], provide well documented procedures and guidelines for evaluating wind and seismic loads. However, there is limited literature on how to account for external loads from attached piping. Typical major project schedules have vessels and their supports/foundations designed well before the development of the piping design that provides calculated actual nozzle and piping loads on the vessel. This paper reviews the type of piping loads, how the piping loads are translated to the vessel support/foundation and provides a proposal for simplified approach analysis on how to apply these piping loads in the design of the vessel support/foundation. There might be cases where the piping loads will cancel out, but that may not always be the case. Ignoring and not considering nozzle loads in the support design/foundation may not be appropriate for all vessels. The intent of this paper is to also make the Vessel Engineer aware of ways to reduce these loads and to encourage communication with Stress Engineers in regards to flexibilities and other factors used to calculate nozzle/piping loads. In most cases, the vessel shell and nozzles are considered as rigid anchors in the piping stress analysis. By using the proper flexibility at nozzle junctions and the global vessel flexibility, the effect of piping loads in the design of the vessel support can be reduced. There is little or no industry guideline on how to include loads due to the thermal expansion or contraction of piping. Since the thermal loads and calculation of flexibility are the least understood part of the analysis, this paper provides background including examples of how these loads and flexibilities can be calculated. In short, the intent of the paper is to provide a better understanding of how piping loads are translated to the vessel support and to provide some design guidelines that are not readily available in current literature and are not clearly specified in the industry codes or standards.

Plant operating experience with Alloy 600 reactor pressure vessel top head penetration nozzles in U.S. PWRs shows that the inspection intervals prescribed by ASME Code Case N-729-1 have been successful in managing the PWSCC concern. No through-wall cracking has been observed in the U.S. after the first in-service volumetric or surface examination was performed on all CRDM or CEDM nozzles in a given head. The current inspection intervals have facilitated identification of any PWSCC in its early stages, with small numbers of nozzles affected and substantial margins to leakage at the five affected heads operating at Tcold. MRP-395 demonstrated through both deterministic and probabilistic analyses that the inspection intervals of Code Case N-729-1 remain valid to conservatively address the PWSCC concern. This paper supplements MRP-395 with additional deterministic crack growth analyses coupled with assessments of the PWSCC indications detected in heads operating at Tcold. The supplemental deterministic assessments presented in this paper demonstrate the acceptability of a 36-month volumetric or surface inspection interval for heads with previously detected PWSCC and that operate at Tcold. Until Code Case N-729-5 is approved by U.S. NRC, use of the 36-month interval in the U.S. for such heads would require review and approval by U.S. NRC of a relief request submitted by the licensee.

Floating Production Storage and Offloading (FPSO) floaters have the advantages of providing the required storage in the hull and direct offloading to tankers of opportunity in deep and ultra-deep water in areas lacking infra-structure. Steel Catenary Risers (SCRs) are the preferred solution in wet-tree applications due to their simplicity, robustness and low Capital costs (CAPEX) and Operational costs (OPEX) compared to other riser options. However, due to its relatively high dynamic motions, FPSO is not a feasible host for SCRs in most environments and especially so in the North Sea very harsh environment. Also, for efficient production from rich reservoirs, large diameter and number of risers are typically required. This makes it more challenging to find a robust and commercially attractive riser solution. In this paper a novel design for an FPSO with the ability to host SCRs in the North Sea very harsh environment is presented and evaluated. The novel design, namely, Low Motion FPSO (LM-FPSO), has a hull form with a generally rectangular cross-section. The platform is moored in-place using a conventional mooring system. The LM-FPSO performance is enhanced with the robust low-tech feature, namely, free-hanging solid ballast tank (SBT). The SBT is located certain distance below hull keel and connected to the hull through four groups of short tendons. All tendon components are the same as those used in conventional TLPs. Through the mass and added mass of the SBT, the LM-FPSO provides significantly improved heave, roll and pitch responses. The paper presents detailed description of the novel North Sea LM-FPSO design and its in-service performance. The SCR’s feasibility is discussed. The identified risks and associated mitigations for the new design compared to the conventional FPSO are investigated and reported. The paper concludes with discussions on the project execution plan and cost benefit when developing fields using this novel design.

Tidal turbines are emerging technologies offering great potential for the harnessing of a renewable and predictable oceanic resource. However, exploitation at sea comes with significant design, installation, grid connection, and maintenance operations challenges. Consequently, guidelines and standards are required to ensure safety, quality, performance and accelerate tidal turbines development and commercialisation. Standardisation is also a necessity to support and improve safety and confidence of a wide range of Marine Renewable Energy (MRE) stakeholders such as designers, project operators, investors, insurers or final users. There are undergoing developments on guidelines, standards and certification systems within the International Electrotechnical Commission (IEC) Technical Committee TC 114 “Marine energy - Wave, tidal and other water current converters” and the IEC Renewable Energy “Marine Energy - Operational Management Committee” (IECRE ME – OMC). However, as the tidal energy concepts are only at the demonstration stage, only few guidelines and no dedicated certification scheme has been published so far within this organization, which guarantee an international, independent, non-governmental and consensus-based elaboration process. The aim of this paper is to present a proposal of certification methodology, developed by Bureau Veritas for the design assessment of current and tidal turbines, and its application to a French case study. This certification procedure was developed within the French research project Sabella D10 funded by ADEME and is published in the Bureau Veritas guideline NI603 “Current & Tidal Turbines”. The suggested certification procedure addresses prototype, component, type and project certification. Main objective, scope, intermediary steps to be completed and resulting certificates will be detailed for each certification scheme, as well as their interactions. This methodology will be illustrated by the case study on the Sabella D10 prototype, a French tidal turbine installed in 2015 in the Fromveur Passage, off Ushant Island. Sabella D10 is a 1 MW tidal turbine fully submerged laid on the seabed with a horizontal axis and 6 blades. It is the first French tidal turbine producing electricity and connected to the electrical network. The Sabella D10 case study will focus on prototype certification and computations performed for support structure and blades. The paper will describe the load cases that have been considered, the review procedure for the support structure and the blades design assessment, including description of a streamlined method for basic design and a detailed method for final design. In conclusion, the next steps will be introduced to continue the certification developments of tidal and current turbines.

Semi-submersible type offshore floating structures are expected to be used in the Japanese coastal area and at sea off Japan for promoting resource exploitation and development in near future. As a moored offshore floating structure may be suffered from current, Vortex-induced Motion (VIM) effect should be assessed in an appropriate manner since the VIM may cause fatigue damage of the floating structure’s mooring lines. VIM phenomenon on semi-submersible type floating structures, however, is not clear, and its comprehension is insufficient since there are only small number of open research papers with lack specifications of the structures. Moreover, a standardized assessment method for the VIM on them has not ever been proposed. At first in this paper, the results of VIM measurement test using some large semi-submersible floating structure models in relatively high Reynolds number flow are presented, and afterwards simplified estimation method, that is useful in the design stage for a semi-submersible type offshore floating structure, is introduced as one trial.

The analysis of the influence of risers on the motions of a floating platform is often conducted and simplified by uncoupled method. As the number of risers and water depth increase, this method would not predict system motion accurately. Coupled analysis method in time domain becomes a very convenient approach in response calculation since it automatically includes the interaction among platform, mooring lines and risers. This paper introduces a full coupled approach by AQWA-NAUT to include viscous damping of the semi submersible and effects of steel catenary risers on the wave frequency response of platform in time domain motion analysis. The main conclusion of this paper is that full coupled method can accruately predict semi submersible Response Amplitude Operator (RAOs) comparing to the case without risers. Other conclusions are that risers have an important effect on the wave frequency motion of semi submersible and also lead to a phase lag with respect to platform motions.

This paper presents the outcome of investigations on the effects of H2S consumption in the annulus of a flexible pipe. Low-molecular gases, such as CH4, H2S, H2O and CO2, permeate slowly from the bore through the inner liner into the annular space between the inner liner and outer sheath of a flexible pipe. This space is densely packed with carbon steel armour wires leaving a very limited free volume. In the presence of water, a corrosive environment for the armour wires is generated and a risk of sour service cracking is introduced. H2S concentration in the annulus is traditionally calculated by balancing the inflow through inner liner and the outflow through outer sheath and vent valve. In order to assure H2S resistance of the armour wires towards calculated H2S concentrations, pipes for sour service are typically designed with lower strength wire grades of larger dimensions compared to the possibilities of sweet service pipes. Over the last decade, more and more offshore data has been obtained indicating considerably less H2S in the annulus than predicted by the traditional annulus models. This observation has triggered in-depth investigations of the complex corrosive H2S environment inside a flexible pipe annulus exposed to sour service conditions. An extensive small-scale test program has been conducted and showed that at permeation rates typical for flexible pipes, the consumption of H2S in the corrosion processes occurring in the annular space lowers the concentration and hence criticality of the H2S so significantly that it leaves the traditional models overly conservative to an extreme extent. Using this knowledge of consumption of the corrosive gases in the annulus has become an increasingly important topic with the focus on deeper waters, cost savings and service life extensions without compromising flexible pipe integrity. Based on experimental data obtained, a new annulus model for prediction of H2S pressure in annulus has been derived. Data is presented in this paper to illustrate the methodology for an annulus prediction where the consumption of H2S is included. The data presented covers laboratory tests with variations and effects of gas flux, H2S concentration and total pressure. A full-scale validation, led to an Independent Verification Agency certification of the model. With the introduction of this new annulus prediction model, a wider range of wire products becomes available for the pipe designers. Lower weight pipes with stronger armour wires render optimizations for both cost savings and applications at deeper waters possible.

As offshore reservoirs are depleted, the seabed may subside. Bottom fixed installations which have previously had sufficient clearance between the deck and the sea surface may be in a situation where wave impact with the deck must be considered at relevant probability levels. Some statistical aspects associated with the calculation of a deck impact load with a prescribed probability of occurrence are the subject of the present paper. The Short Crest JIP addressed the distribution of the crest height in extreme sea states, the properties of the largest crests and the deck impact loading on a closed deck. It was concluded that the largest waves in the sea may be in the process of breaking and thus have properties which deviate significantly from estimates found from weakly nonlinear irregular or regular wave theory. The present paper addresses findings from the Short Crest JIP regarding • long-term analysis of wave heights and crest, including the effect of wave breaking • air gap analysis for jacket, TLP and semisubmersible using 2nd order time domain simulations over the platform area • statistics for horizontal wave-in-deck impacts for short crested sea versus for long crested sea • structural reliability analysis of jackets for some simple limit states that are governed by loads caused by impact of extreme crests

The floating offshore wind turbine (FOWT) market is currently dominated by single unit demonstration projects and first pre-commercial wind farms such as the Hywind Scotland wind farm. Today’s FOWT substructure design process is therefore not yet at a level of industrialization comparable to fixed-bottom substructure design methodologies, where standardized design and realization procedures are well established throughout the industry. Aligned with work performed in the Ramboll and University of Stuttgart-led work packages “Concept Industrialization” and “Design practice” of the European H2020 LIFES50+ project, the ambition of this paper is to define state-of-the-art fixed-bottom and floating design methods and based on these identify key differences through comparative analysis. In the first part of the paper the scope and selected details of today’s industrialized design process for fixed-bottom substructure design is presented, including e.g. load iteration schemes and applied numerical methods, risk assessment incorporation, optimization, and cost modelling. In the second part, the key elements of this industrialized procedure which are different to FOWT design are identified and described: This is done based on a review of the current FOWT common design practice, where elements are identified that are unique and/or different for FOWTs — this includes e.g. the requirement to adapt the controller to the specific platform behaviour, as well as a tower and/or selected rotor-nacelle assembly (RNA) component redesign, and also includes differences in terms of defining and performing load case simulations. Another observation that is described relates to the floating specific required numerical methodologies applied for the detailed structural and mooring design, where challenges exist regarding the interface between coupled global loads analyses tools and detailed structural, mooring, and geotechnical tools. A further key item discussed in this respect is the industry-common load exchange practice for fixed-bottom design, where only a limited data exchange between WT manufacturers and platform designers is done; a procedure that is challenging to be applied for FOWTs. Compared with fixed-bottom design, the consideration of manufacturability, fabrication constraints, serial production, design complexity reduction, assembly, supply chain, installation, geotechnics, O&M and risk is often limited and these items will also be briefly discussed. Overall the paper is intended as a technical review of existing fixed-bottom design procedures and, facilitated through the comparative analysis with these established design methodologies, identifies and presents the key differentiating design elements and challenges for an industrialized FOWT design. The content of the paper will provide input for the focused development of design processes for industrialized detailed design of FOWTs to guarantee the demanded technology-readiness and manufacturing-readiness levels (TRL and MRL) and ultimately improve their CAPEX and OPEX by applying industrial design procedures. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 640741 (LIFES50+ project, www.lifes50plus.eu).

With the aim of aiding mitigation efforts, in mapping and simulating the transport of the discharged hydrocarbon this paper proposes an autonomous surface vehicle (ASV), propelled by wind and water currents for the long-term monitoring of spilled oil on the ocean surface. This paper makes a unique contribution to the literature in proposing a cluster-based decision-making algorithm for sailing the ASV based on a complete scanning history of the area surrounding the vehicle by the oil detection sensor. A Gaussian-based oil cluster filtering algorithm is introduced to identify the largest oil slick patch. The physical constraints of the ASV have been taken in account to allow for the computation of feasible maneuvering headings for sailing to avoid sailing upwind (i.e., in the direction from which the wind is coming). Finally, using neoprene sheets to simulate oil spills, field test experiments are described to validate the operation of the ASV with respect to oil spill tracking using a guidance, navigation, and control system based on onboard sensor data for tracking the artificial oil targets.

A ship hull is regarded as a box girder structure consisting of plates and stiffeners. When the ship hull is subjected to excessive longitudinal bending moment, buckling and yielding of plates and stiffeners take place progressively and the ultimate strength of the cross-section is attained. The ultimate longitudinal bending strength is one of the most fundamental strength of a ship hull girder. Finite element method (FEM) analysis using fine-mesh hold models has been increasingly applied to the ultimate longitudinal strength analysis of ship hull girder. However, the cost and elapsed time necessary for FEM analysis including finite element modelling are still large for the design stage. Therefore, the so-called Smith’s method [1] has been widely employed for the progressive collapse analysis of a ship hull girder under bending. Recently, there is a growing demand for a container ship, which is characterized as a hull girder with large open decks. This type of ship has a relatively small torsional stiffness compared to the ships with closed cross-section and the effect of torsion on the ultimate longitudinal strength may be significant. However, the Smith’s method above mentioned cannot consider the influence of torsion. Therefore, some of the authors developed a simplified method of the ultimate strength analysis of a hull girder under torsion as well as bending [2–4]. In this method, a hull girder is modeled by linear beam elements in the longitudinal direction, and the warping as well as bending deformation is included in the formulation. The cross-section of a beam element is divided into plate elements by the same way as the Smith’s method. Therefore, the shift of instantaneous neutral axis and shear center can be automatically considered by introducing the axial degree of freedom as well as the bending ones into the beam elements, and keeping the zero axial load condition. In this study, the average stress-average strain relationship of each element is calculated using the formulae of the Common Structural Rules (CSR) [5] and HULLST proposed by Yao et al. [6, 7] considering the effect of shear stress due to torsion on the yield strength. There had been a lot of papers [8] which discuss the importance of strength assessment to large container ships under torsion. However, there are few papers which discuss the influence of torsion on the ultimate hull girder strength. In this paper, the proposed simplified method is applied to the existing Post-Panamax class container ship. First, a torsional moment is applied to the beam model for the ship within the elastic range. Then, the ultimate bending strength of cross-sections is calculated applying the Smith’s method to a beam element considering the warping and shear stresses. On the other hand, nonlinear explicit FEM are adopted for the progressive collapse analysis of the ship by using LS-DYNA. The effectiveness of present simplified analysis method of ultimate hull girder strength under combined loads is discussed compared with the LS-DYNA analysis.

Current elevated turbine inlet temperatures were made possible by the development of blade thermal barrier coatings (TBCs). However the effectiveness of these coatings could be compromised by erosive particles ingested into the engine with the incoming air or generated by the combustion of heavy and synthetic fuels. Reliable test facilities are essential to characterize their erosion resistance in increased test temperatures. This paper provides a detailed description of an advanced high temperature erosion tunnel capable of testing at temperature of 1370 °C (2500 °F) that has been recently constructed and installed in the University of Cincinnati Gas Turbine Erosion Lab. The paper also presents an overview of both theoretical and experimental investigations dealing with the new high temperature erosion tunnel design optimization and validation with comparisons to our legacy erosion tunnels. Results are presented for tested standard plasma sprayed 7 wt% Yttria stabilized Zirconia (7YSZ) TBC coated samples’ erosion rates at different temperatures, particle impact velocities and impingement angles.

The present paper analyzes the effect of passive flow control (PFC) with respect to the retrofitting on small horizontal axis wind turbines (sHAWTs). We conducted extensive wind tunnel studies on a high performance low Reynolds airfoil using different PFC elements, i.e., vortex generators (VGs) and Gurney flaps (GF). qblade, an open source blade element momentum (BEM) code, is used to study the retrofitting potential of a simulated small wind turbine. The turbine design is presented and discussed. The simulations include the data and polars gained from the experiments and give further insight into the effects of PFC on sHAWTs. Therefore, several different blades were simulated using several variations of VG positions. This paper discusses their influence on the turbine performance. The authors especially focus on the startup performance as well as achieving increased power output at lower wind speeds. The vortex generators reduce the risk of laminar separation and enhance the lift in some configurations by more than 40% at low Reynolds numbers.

The efficiency and reliability of turbomachinery will be improved by blade tip clearance (BTC) and blade tip timing (BTT) monitoring. Several types of sensors such as eddy-current, capacitance and optical probes are used to realize this objective. Eddy current sensor (ECS) is an ideal choice with its advantage of durablity and that it is unaffected by gas stream properties such as contamination, water vapor, and moisture. However, the bandwidth of ECS is usually less than 100 kHz, which will limit the resolution of the monitoring result. In this paper, a pulse-trigger technology based BTC method was presented. This method optimizes the static radial and circumferential calibration technology to obtain the sensitivity of the ECS in the different relative locations against the tip of blade. The information from the clearance sensor will be fused with that from the once per revolution (OPR) or key phase sensor. The method is more generally applicable in the condition where the ECS is insufficient sampling caused by the limit of narrow bandwidth, especially under the high blade tip velocity condition. A small scale and larger scale BTC measurement rig are established to validate the feasibility of this method. The small one is easy to calibrate with high accuracy and can be used to illustrate the performance of the method, while the larger scale test rig is close to real industry turbine blade. In this apparatus, the axial displacement and radial displacement of rotor vibration as well as the clearance can be monitored together so that further investigation can be conducted. Experimental research was carried out on both test rig at different rotating speed. The results show that the method presented in this paper can improve the accuracy of tip clearance monitored by ECS very well. Furthermore, this work is a proof-of-concept demonstration using a laboratory setup providing the basis for BTC active control and blade health monitoring (BHM) based on ECS.

The Synchro-Self-Shifting (SSS) overrunning clutch is well known, particularly in the Naval Marine field. This paper reviews the clutch operating principle, then outlines some of the service experience since 1962, particularly in naval main propulsion drives beginning with CODOG, CODAG, COGOG and COGAG plant, and then the experience with more recent applications such as combined electric motor propulsion with either gas turbines or diesel engines and hybrid electric plants. Extra features are then described such as a lock-out control as is usually necessary for turbine applications to permit turbine testing, e.g., when in harbor; also a lock-in control as is essential when the clutch has to transmit power in both directions of rotation. Various clutch mounting arrangements will be presented with respective advantages. The paper concludes with information regarding reliability during many years of service experience.

Small horizontal axis wind turbines (sHAWTs) are mostly designed by smaller companies with no or just small possibilities of aerodynamic testing and hence, airfoil selection is often based on published performance data and minimal or no experimental testing from the blade designer’s side. This paper focuses on the aerodynamic consequences resulting from an unqualified airfoil selection and accumulating surface soiling. The high performance low Reynolds profile FX 63-137 is compared to an Eppler-338 wing section as well as to a high performance utility scale wind turbine airfoil, AH 93-W-174 -1ex. We extensively investigated these three different airfoils within the low Reynolds regime between 50,000 and 200,000. This regime is especially important for the starting behavior of a wind turbine, i.e. a quick speed up, and is crucial for small wind turbines because they have more frequent start/stop events. A Reynolds number of 200 k is additionally the operational regime of some sHAWT under the 5–10 kW level. The present study discusses not only the low Reynolds performance of the smooth profiles but investigates the influence of surface soiling. This ranges from 2D disturbances, such as a 0.2mm thin tripwire or several zigzag tapes, up to the simulation of massive sand build up by covering the entire leading edge region with a 40 grit sand paper. The experiments reveal that even small surface soiling has an impact and massive roughness leads in some cases to the loss of 50% in lift coefficient. The experimental data is used to simulate a sHAWT in different stages of debris. While the peak power was reduced by two thirds compared to the clean configuration the annual energy production has halved under certain conditions.