The paper addresses the flow-induced response of a rigid spool/jumper. It mainly focuses on its mechanical response resulting from internal intermittent slug flows but also addresses potential coupling with an external excitation due to vortex shedding. These works provide quantitative experimental data that match quite well with existing empirical correlations in terms of slug flow properties. The repeatability of the measurement system has been experienced and underlines promising capabilities. The tests provide exhaustive complementary data regarding the slug flow properties (e.g. pocket length) which will be reused for numerical modelling purpose. The mechanical response of the spool is exhaustively addressed for different regular slug flows. Some correlations are proposed aiming at describing the mechanical responses. The coupling with an additional external current solicitation and Vortex Induced Vibrations (VIV) is discussed and characterized for some conditions. Finally, a discussion on the current Industry Best Practices is introduced in order to challenge the capability of the proposed approaches to described and recover such complex phenomenon. The comparisons underline the weak agreement between experiments and numerical models, opening discussion on the best way to address this physics and the next developments.

In the Deep-Sea Mining, the seafloor mining tool is connected to the subsea slurry pump by a piece of flexible pipe named jumper. The jumper’s shape is similar to a steep-wave flexible riser. Compared to a flexible riser, the jumper is a reinforced hose and has a shorter length. Numerous studies shed light on the dynamic behavior of flexible riser; however, all studies were carried out by the way of numerical analysis. We carried out, in the Deep-Sea Basin, an experiment using 1/5 reduced scale model of the jumper. Unhappily, the model’s bending stiffness had to be distorted. During the experiment, an oscillator generated harmonic motion on the top end of the model and a centrifugal pump circulated water throughout the model. In addition, we installed load cells on the top and bottom ends of the model. Our Basin is equipped with a visual measurement system. Thus, we measured the displacement of targets attached to the model. The initial results show that axial tension amplitude increases with the frequency of the top end oscillation. This response is due to the drag force on the lower bend increases with the frequency of top motion. We also could observe that the internal flow may increase the vertical motion amplitude. The jumper’s motion generates an oscillation on the internal differential pressure between both ends and the flow velocity. The differential pressure amplitude increases with the top oscillation frequency, but it is proportional to the top end oscillation amplitude. We will use these experimental results to validate our numerical models. Further, it is important to understand the internal flow effects to design the actual pump used to convey the slurry through the jumper.

In our prior investigations, extensive numerical simulations have been conducted to reveal the unsteady aerodynamics of Floating Wind Turbine (FWT). To validate the simulation results and further deepen the corresponding topics, a dedicated experimental apparatus has been developed by the State Key Laboratory of Mechanical System and Vibration (SKL-MSV) and State Key Laboratory of Ocean Engineering (SKL-OE) at Shanghai Jiao Tong University (SJTU). The main modules of the test bed include a dedicated Wind Generation System (WGS), a Model Wind Turbine (MWT), a 6-DOF (Degree Of Freedom) Motion Control Platform (MCP) and an integrated measurement system. The WGS is able to generate controlled flows with different wind speeds, turbulence intensities, and horizontal/ vertical wind shears. The MWT is equipped with Fiber Bragg Grating (FBG) sensors on the blade surface to monitor the operating conditions. The MCP is developed to generate controlled oscillations to the MWT aiming to model the oscillation of the FWT in offshore environments. The measurement system includes a torque sensor, two 6-DOF load cells, a 3-DOF accelerator, 2 FBG-fibers each with 3 FBG sensors, and a Wake Detection System (WDS) consisting of 6 hot-wire probes. Extensive calibrations are conducted for the WGS and the transducers. Some primary results about the unsteady aerodynamics of the FWT are presented. In the future, the MCP will be replaced by a floating platform to conduct the tests in the wave tank at SKL-OE to reveal the fully coupled dynamics of FWTs.

Full-scale measurements of shaft torque have been performed on several voyages of a polar supply and research vessel, the SA Agulhas II. Previous work has looked at the determination of the externally induced ice moments on the propeller to shed light on the expected loading conditions in the harsh Antarctic environments. This has been done by making use of a lumped mass model, measurements taken on the shaft-line and an inverse prediction algorithm. Thus the externally applied loads are determined through the internal measurements on the shaft-line. The work presented here is in an effort to assess the validity of the lumped mass model parameters used in the external moment determination process. Two methods of validation have been performed. The first is through the comparison of the lumped mass model to operational modal analysis data of the shaft-line, obtained during dry-dock operations in 2017. The second validation method that is considered relies on data recorded on board the SA Agulhas II during its 2018–19 Annual Relief Voyage to Antarctica. The shaft-line measurement system has been expanded to include the measurement of torque at a second location, further down the shaft. These two measurement locations are each used to determine the external loads and their results are compared. It was found that the results of the validation show correlation, albeit with some error, and that the developed method is valid for use in determining externally induced ice moments. However, there is room for improvement of the current external moment determination method.

In connection with the Statoil SKT project, DNV GL have developed a method for estimating ice loads on the ship hull structure and mooring tension of the anchor handling tug supply (AHTS) vessel Magne Viking by full scale measurements. In March 2017, the vessel was equipped with an extensive measurement system as a preparation for the dedicated station-keeping trial in drifting ice in the Bay of Bothnia. Data of the ice impacts acting on the hull were collected over the days of testing together with several other parameters from the ship propulsion system. Whilst moored, the tension in the mooring chain was monitored via a load cell and logged simultaneously to the other parameters. This paper presents the processes involved in developing the measurement concept, including the actual installation and execution phases. The basic philosophy behind the system is described, including the methods used to design an effective measurement arrangement, and develop procedures for estimation of ice loads based on strain measurements. The actual installation and the process of obtaining the recorded data sets are also discussed.

Well system fatigue accumulated during drilling operations from mobile offshore drilling units (MODUs) has been a topic of intensive study in recent literature. A variety of efforts from individual operator studies to industry-wide joint industry projects have been launched in an effort to improve understanding of both the load and resistance elements of well system fatigue assessment. A key uncertainty in current predictive modeling practice is the level of conservatism inherent in that modeling, as compared to real-life system response. Collection of good quality, full-scale field measurement data is a key component in evaluating this uncertainty. A full-scale measurement campaign was recently conducted on a 6 th generation MODU during drilling operations in a shallow water region with a harsh environment. The measurement system on board the vessel captured vessel, riser and lower marine riser package (LMRP) accelerations and angular rates, along with riser tensioner pressures. Concurrent environmental measurements were acquired via wave rider buoy and acoustic Doppler current profiler (ADCP) located near the mobile offshore drilling unit (MODU), capturing wave height, period and direction, and full-depth current profiles. This paper focuses on data collected for one well during the winter months where significant wave heights at the drilling site varied from 6ft to 26ft. In this paper, a comparison between measured and predicted riser and well system loading is presented. The predicted riser and well system response is based upon global riser analyses performed in both the frequency and time domains to evaluate the effect of linearization in the modeling process. Loading demand on the well system is also presented as cycle-range histograms. This paper also summarizes the conclusions from the comparisons of these measurements with other published measurement campaign data. While loading derived from previous riser analysis studies have been found to be “conservative” as compared to full-scale measurements, this study finds that the predicted and measured responses match quite well. Furthermore, it is also shown that the frequency domain results are adequate for this study, suggesting that the nonlinearity within the riser and well system for the conditions studied is relatively minor.

Well cements are an important aspect of wellbore integrity and recent investigations focus on describing the cement lifetime using, when possible, non-destructive tests like ultrasonic measurements. However, the original API and ASTM testing standards were based on destructive mechanical testing of cements, leading to the decision to investigate the backward and forward compatibility between ultrasonic measurements and mechanical testing, which makes the subject of this work. Ultrasonic cement measurement became a very popular method to assess the mechanical properties of the cement in a non-destructive manner. Since various measurement systems exist on the market, the development of an accurate reference data base that can be used to calibrate such measurements becomes very important. Two major systems have therefore been compared: the ultrasonic compressive strength, using the ultrasonic pulse velocity (UPV) principle, and the unconfined compressive strength (UCS), using the standard testing frame according to API and ASTM standards. The tests have been performed at different curing times, using both devices, on class G API cements with bentonite and other additives. This paper presents the results of over two hundred experiments that have displayed a different UPV response as a function of the additive content. These allow us to expand the existing UPV vs. UCS correlations. Moreover, it was observed that after a given curing time, depending on the additive and its concentration, the UPV response is not as sensitive as the results yielded by the UCS method. The outcomes are an important step forward to improve and understand the wellbore integrity.

Trimaran, as a high performance ship, its special ship form is different from regular monohull ship. The particular characteristics of longitudinal and transverse wave loads are concerned greatly by ship structure designers. Theoretical methods for forecasting the wave loads of trimaran are under developing. And the relative comprehensive model test study of trimaran’s wave loads is rare in the publication. In this paper, the trimaran model test had been carried out in the tank. According to similarity theory and simulation of stiffness, a scale model of trimaran with measurement system had been manufactured. Then the segmented model had navigated in regular waves of different sea conditions. Through analysis of the experimental data, the wave loads characteristics of this trimaran are presented. A comparison of test results and theoretical values is also made to show the similarities and differences. This study can provide some useful information for further design of high-speed trimaran in the point of wave loads, which maybe a reference for research of trimaran.

Drilling fluids play an important role in safe and efficient drilling operations. Wellbore stability, formation integrity, drill string lubrication, and cuttings transport are among their main requirements. The removal of a cuttings bed is one of the major difficulties while trying to keep up a steady drilling progress. Deviated and long horizontal wellbore sections provide challenges not only to the drilling equipment in use, but also to the fluids. Cuttings accumulate easily on the bottom of a wellbore section due to gravity and can therefore reduce hole cleaning efficiency. Cuttings transport is highly dependent on the properties of the drilling fluid. Viscosity, density and gel strength are among the key parameters. Drilling fluids have in general a complex composition with either water or oil as a base substance. Demanding operating conditions, for example high temperature difference from topside to the deep downhole sections or varying shear rates throughout the wellbore, also influence the properties of the fluids during operation. Drilling fluids have to be adapted to all these different drilling situations. The aim of the full project is to compare different water- and oil-based drilling fluids regarding their hole cleaning abilities. As part of the experimental study where drilling fluids are circulated in a 10 m long flow-loop test section with a free-whirling rotating inner drill string, rheological characterization with an Anton Paar MCR rheometer is performed. These measurements include determination of flow properties, yield stress and viscosity-temperature dependence. The results are correlated with the industry standard procedures for the testing of drilling-fluid properties with Fann 35 viscometers (API/ ISO standards). Measurements performed on viscometers at the oil rigs are done to receive fast results in order to control the drilling operation. In contrast, rheometer measurements provide the possibility of a deeper comprehension of the rheological properties of the drilling fluids due to the advanced measurement system. This work presents rheological properties for a typical oil-based drilling fluid commonly used on the Norwegian Continental Shelf, and includes a comparison with two other oil-based drilling fluids based on previously published work. The rheometer results are analyzed in relation to the flow loop experiments and to the viscosity data measured in accordance with the API/ISO specifications. The results from the rheological comparison together with the results from the flow-loop experiments are expected to make an influencing contribution to the question of why various drilling fluids perform so differently in terms of cuttings transport.

Extreme and long-term wave data near small islands, which are quite different from that of open seas, are crucial for the safety of offshore platforms. An environmental measurement system was deployed around a small reef island, which includes three wave buoys. The concerned environment parameters, such as wave height and period, current and wind speeds etc., have been measured by the system in a long-term plan. Meanwhile, a numerical scheme based on shallow water theory was developed, and the numerical simulations of the wave evolution around the islands were carried out and the results were validated with the measured data. It was revealed that the wave statistics changed significantly on the route of wave propagation. The ratios of wave parameters between near island locations and far field were obtained. Based on the method developed in this study, it is possible to predict the wave conditions at a location close to the shore on the basis of the known far field incident wave, which can be used for the design of near shore structures in the future.

In August 2014 Heerema Marine Contractors (HMC) have successfully installed the Solan Subsea Oil Storage Tank (SOST), using its Semi-Submersible Crane Vessel (SSCV) Thialf. The SOST installation is regarded as unique due to its dimensions, complex hydrodynamics and the utilization of nearly the full crane capacity. The Solan SOST is a Subsea Oil Storage Tank with a future storage capacity of 48,000 m 3 of oil. The SOST has a dimension of 45m × 45m × 25m, a dry weight of 9,500mT and a total submerged mass of 60,000mT including ballast water. It was installed offshore west of the Shetland Islands at a depth of 135m. Prior to installation the SOST was wet-towed to the field. At location the SOST was installed by a dual crane lift sequence, lowering the SOST from 2m freeboard to the seabed. The lowering sequence is characterized by the usage of a compressible air pocket to reduce hookloads during the most critical stage of the installation, the lowering of the SOST through the splash zone. Prior to the installation ballast and dynamic lift models were generated to understand both the hydrostatics and hydrodynamics of the SOST - SSCV Thialf system throughout the installation. Numerical simulations of the flooding operation were performed to predict all relevant parameters for various scenarios. The lift dynamics were analysed with frequency domain models. Most resonance modes between SSCV Thialf and SOST were found not to be excited due to the differences in natural periods of the hydrodynamic systems and the occurring wave periods. During installation vital parameters such as ballast volume, compartment fill rates, differential pressure and hookloads were continuously monitored with dedicated measurement systems. The values were compared with the results from the engineering models. As some of the parameters were directly related to each other, the values could be back-calculated and cross-checked, thereby increasing the reliability of the measurements. Both the understanding of the principle hydrostatics and hydrodynamics of the system as well as the close monitoring of all vital parameters have resulted in a safe and controlled installation of the Solan SOST by the SSCV Thialf; the installation of a 60,000mT dual crane pendulum. This paper describes the hydromechanic engineering work performed by HMC and the SOST offshore installation.

This paper investigates the stability of a submarine gassy slope triggered by tidal variations. Under tidal variations on an unsaturated slope, failure may occur under specific combinations of increasing degree of saturation and soil permeability, and decreasing tidal period. A novel physical model test in a geotechnical centrifuge was undertaken of a submarine slope containing gassy sediments. The model preparation techniques, measurement systems and preliminary results are presented. The response observed in the model test is discussed and further developments proposed. Existing numerical simulations may provide a basis for verification and validation of future physical model test results.

Anti-Roll Tanks (ARTs) can be a successful device to reduce ship roll motion (Figure 1), but the tank has to be properly designed. A good design includes an appropriate number of damping devices in the tank to reduce the water motions at resonance and to increase the frequency range over which the tank works efficiently. It is difficult to accurately predict the effect of different damping devices on the roll damping moment of the tank; usually tests on a rotating table, so called bench tests, are performed for each individual design. Nowadays, CFD (see e.g. [1]) calculations solving the URANS equations can predict the effect of damping devices on the roll motion of the tank. In order to validate such codes a series of experiments with a U-type ART on a rotating table have been carried out where the interior arrangement in the duct of the tank has been varied. The set-up of the experiment, the measurement system and the results of the experiments are presented and discussed in this publication; the raw data of the experiments are also made available.

A Wave Energy Converter (WEC) measurement system has been constructed and installed with the purpose to measure, log and evaluate the WEC’s performance during operation at sea. The WEC is to be deployed at Uppsala University’s wave power research site in Lysekil on the west coast of Sweden. In designing such a system the key research objectives has been (1) to study the risk of overheating due to high currents in the stator windings, (2) to evaluate how the WEC’s outer structure withstands drag and bending forces from the buoy line and (3) to construct a detection system which indicates if water leaks into the generator. The measurement system was designed to collect data essential to study these key objectives. Transducers were used to measure: buoy line force, translator position, phase currents, bending and tensile strain on the generator hull, water level inside generator and the temperature at multiple places inside the generator. The measurement system has been installed and calibrated in the WEC. Furthermore, the design has been evaluated in lab experiments in order to verify the function and accuracy of the different measurements. This paper presents the underlying research objectives for developing the WEC generator measurement system, together with a description of the technical implementation.

An experiment using a 1/70 reduced scale model of a Free Standing Riser (FSR) was carried in the Deep-Sea Basin of the National Maritime Research Institute in Japan. For instance, the model’s vertical pipe was about 32 m long and the jumper was about 8 m long. The FSR model had several measurement stations attached along the vertical pipe, subsurface buoy and jumper; and the motion of each station was measured in 3D by the Visual Measurement System. During the experiment, the effects of the jumper’s top end oscillation on the whole system were investigated. In this case, the top oscillation had propagated along the jumper; however the top oscillation had a reduced effect on the dynamics of the subsurface buoy and vertical pipe. In another experimental case, a current was generated in order to investigate the Vortex Induced Motion (VIM) on the FSR’s Subsurface Buoy . The VIM experiment was repeated for two different buoy models (a smooth cylinder and a cylinder with 3-start heli-coidally strakes) and the results were compared. In this article, some of the experimental results are presented and discussed.

We describe the design and performance of a novel optical measurement system that can be used for measuring vortex-induced vibrations (VIV) of long flexible cylinders. We believe this is the first time this technology has been used to measure VIV in a long flexible cylinder. The emphasis is given to the measurement technique itself. It can be used either in air or in water and we believe it is a better alternative to other traditional vibration response measurement techniques used to study VIV in the laboratory. The measurement system is based on the Defocusing Digital Image Particle Velocimetry (DDPIV) concept, proposed by Willert and Gharib in [1] for measuring velocity flow fields. A set-up, which was built to conduct vortex-induced vibration measurements in a wind tunnel facility with a cross-section of 1.8 × 1.2 m, has been used in a laboratory to demonstrate the capabilities of the optical measurement system when known displacements are produced in the mappable or measurement volume. The same supporting structure designed to provide suport for the cylinder models inside the wind tunnel test section, has been used to hold a target which has been move to different known locations to measure the performance of the system. The design, description and performance of the measurement technique are discussed.

In the past of the offshore petroleum production, each riser had conveyed the hydrocarbon production from a single vertical well; the riser’s internal flow rate was relatively low and only the internal fluid pressure was taking into account for the riser analysis. Other internal flow effects, such as internal fluid’s linear moment, and Coriollis effects, were neglected. However, the paradigm for petroleum production in ultra-deepwater is shifting nowadays. New technologies, such as horizontal wells, have increased the production rate from a single well. In addition, a subsea booster system can increase both pressure and flow rate of the riser’s conveyed fluid. Further, the Offshore Mining is rising as a new industry and will demand riser systems to convey, at high flow rates, the mineral ore’s slurry from the seafloor up to the production support vessel. In a previous experiment, the effects of the internal flow on a vertical riser were investigated. In the current experiment, the main objective is to investigate the effect of the internal flow on the dynamic response of a pipe in “jumper configuration”. The experiment was carried out at the Deep Sea Basin of the National Maritime Research Institute using a 10 m long flexible pipe. The actual “jumper” is a piece of flexible riser, in U-shaped configuration, that connects the main structure of “Self-Standing Hybrid Riser” to the production vessel. During the experiment, fresh water was pumped into the model by positive displacement pump; and an oscillator applies a harmonic vibration on one pipe’s end. Then the pipe’s dynamic response is measured by the Deep Sea Basin’s 3D Visual Measurement System. Results for different internal flows and oscillations are compared.

Torpedo pile has become one of the most popular foundation systems in Brazil’s offshore oil exploitation, mostly, due to its low installation cost. Additionally, torpedo piles have shown good fixation capability even when applied in mooring configuration such as taut leg with relatively close angles to the vertical. This fixation capability is closely dependent to the depth of penetration and the final attitude of the pile. In order to determine these parameters, MEMS-based Inertial Measurement Units have been used. Units of this kind are known for high noise density and, alone, are not adequate to any kind of navigation. Concerning these limitations, other sources of data are added to the inertial measurements, in order to improve the system state estimation. This data fusion is carried out by the Kalman Filtering and is also called Aided Inertial Measurement Units. This paper presents the Kalman Filter implementation and the results obtained from the fusion of the pressure gage signal, alternative pitch and roll measurements and the inertial measurements applied to the torpedo pile deployment.

This paper describes a detailed investigation into structural effects on wind measured on an offshore platform. Squalls dominate the extreme wind regime in the West Africa region. The West Africa Gust (WAG) Joint Industry Project was initiated to provide critical new data to support engineering design. The WAG squall measurement system was carefully designed to characterise the horizontal and vertical structure of squall winds. A total of 8 anemometers were installed at various locations on a platform offshore Congo. This application required a high level of confidence in wind speed differences measured at separate locations. An intensive investigation into platform structural effects was undertaken using the in-situ data, supported by independent wind tunnel testing. This paper will explain how the wind tunnel results were effectively used to quantify structural contamination at each key anemometer location, for the full range of incident wind directions. The wind tunnel results were verified using empirical structural correction factors derived from the in-situ data. The study successfully established the required high level of confidence in the measured data, so that squall structure could be characterised for engineering design.

Nowadays, flexible risers are widely deployed in various configurations for the production of hydrocarbons in offshore fields. For example, in the self-standing hybrid risers’ applications, a single riser or a set of risers are suspended by a subsurface buoy called “Can”. Then a piece of flexible riser connects the Can to the production platform conveying the hydrocarbon production stream. This work concerns about this jumper, an experiment using a 10 m long model was carried out at the Deep Sea Basin of the National Maritime Research Institute in Japan. The model was made by three concentric unbonded layers: a silicon made inner layer; a crisscross steel wire layer; and a rubber made outer layer. During this experiment, the model was suspended through both ends; one model’s end was fixed and the other end was connected to an oscillator that generates the oscillatory motion in three different directions. In addition, a positive displacement pump injected fresh water into the model. Further, the model was instrumented with two degrees of freedom accelerometers fixed along its length; and a six degrees of freedom force/torque transducer was also installed at one pipe end. In addition, the Deep Sea Basin’s Visual Measurement System tracks and calculates the motion of several measurement stations along the pipe. A parametric analysis was carried out changing the oscillating frequency and internal flow rate. Discussion and results of numerical simulation are also included.