Thrust Load Research Articles

Data-driven farm-wide fatigue estimation on jacket-foundation OWTs for multiple SHM setups

Abstract. The sustained development over the past decades of the offshore wind industry has seen older wind farms beginning to reach their design lifetime. This has led to a greater interest in wind turbine fatigue, the remaining useful lifetime and lifetime extensions. In an attempt to quantify the progression of fatigue life for offshore wind turbines, also referred to as a fatigue assessment, structural health monitoring (SHM) appears as a valuable contribution. Accurate information from a SHM system can enable informed decisions regarding lifetime extensions. Unfortunately direct measurement of fatigue loads typically revolves around the use of strain gauges, and the installation of strain gauges on all turbines of a given farm is generally not considered economically feasible. However, when we consider that great numbers of data, such as supervisory control and data acquisition (SCADA) and accelerometer data (of cheaper installation than strain gauges), are already being captured, these data might be used to circumvent the lack of direct measurements. It is then highly relevant to know what is the minimal sensor instrumentation required for a proper fatigue assessment. In order to determine this minimal instrumentation, a data-driven methodology is developed for real-world jacket-foundation offshore wind turbines (OWTs). In the current study the availability of high-frequency SCADA (1 Hz) and acceleration data (>1 Hz) as well as regular 10 min SCADA is taken as the starting point. Along these measured values, the current work also investigates the inclusion of an estimate of the quasi-static thrust load using the 1 s SCADA using an artificial neural network (ANN). After data collection all data are transformed to features on a 10 min interval (feature generation). When considering all possible variations a total of 430 features was obtained. To reduce the dimensionality of the problem this work performs a comparative analysis of feature selection algorithms. The features selected by each method are compared and related to the sensors to decide on the most cost-effective instrumentation of the OWT. The variables chosen by the best-performing feature selection algorithm then serve as the input for a second ANN, which estimates the tower fore–aft (FA) bending moment damage equivalent loads (DELs), a valuable metric closely related to fatigue. This approach can then be understood as a two-tier model: the first tier concerns itself with engineering and processing 10 min features, which will serve as an input for the second tier that estimates the DELs. It is this two-tier methodology that is used to assess the performance of eight realistic instrumentation setups (ranging from 10 min SCADA to 1 s SCADA, thrust load and dedicated tower SHM accelerometers). Amongst other findings, it was seen that accelerations are essential for the model's generalization. The best-performing instrumentation setup is looked at in greater depth, with validation results of the tower FA DEL ANN model showing an accuracy of around 1 % (MAE) for the training turbine and below 3 % for other turbines, with a slight underprediction of fatigue rates. Finally, the ANN DEL estimation model – based on two intermediate instrumentation setups (combinations of 1 s SCADA, thrust load, low quality accelerations) – is employed in a farm-wide setting, and the probable causes for outlier behaviour are investigated.

Alignment of scanning lidars in offshore wind farms

Abstract. Long-range Doppler wind lidars are applied more and more for high-resolution areal measurements in and around wind farms. Proper alignment, or at least knowledge on how the systems are aligned, is of great relevance here. The paper describes in detail two methods that allow a very accurate alignment of a long-range scanning lidar without the use of extra equipment or sensors. The well-known so-called hard targeting allows a very precise positioning and north alignment of the lidar using the known positions of the surrounding obstacles, e.g. wind turbine towers. Considering multiple hard targets instead of only one with a given position in an optimization algorithm allows us to increase the position information of the lidar device and minimizes the consequences of using erroneous input data. The method, referred to as sea surface levelling, determines the levelling of the device during offshore campaigns in terms of roll and pitch angles based on distance measurements to the water surface. This is particularly well-suited during the installation of the systems to minimize alignment error from the start, but it can also be used remotely during the measurement campaign for verification purposes. We applied and validated these methods to data of an offshore measurement campaign, where a commercial long-range scanning lidar was installed on the transition piece platform of a wind turbine. In addition, we present a model that estimates the quasi-static inclination of the device due to the thrust loading of the wind turbine at different operating conditions. The results show reliable outcomes with a very high accuracy in the range of 0.02∘ in determining the levelling. The importance of the exact alignment and the possible applications are discussed in this paper. In conclusion, these methods are useful tools that can be applied without extra effort and contribute significantly to the quality of successful measurement campaigns.

Modelling and Analysis of High-Speed Angular Contact Ball Bearing

Angular contact bearings are of primal importance in accommodating rotational mechanisms with high-speed characteristics. Their applications are centric to heavy axial and radial loads sustaining thrust loads to a single direction. In high-speed applications, factors such as centrifugal force, gyroscopic moments and relative displacements in various geometric features of the bearings are to be taken into consideration. This study focuses on establishing the contact angles, contact forces and spin speed for angular contact bearing to withstand varied rotational angular velocities. The forces experience a non-linear variation with respect to the body stiffness thus necessitating the involvement of numerical methods to converge at precise solutions through each juncture. The outer raceway of the bearing is accepted to be static with respect to the inner raceway as the input shaft for any application is predominantly affixed to the inner raceway of the angular contact bearing. Geometrical variations are determined under combined load conditions to simulate the natural working of the bearing at accelerated speeds. The analyses involve results for spatial parameters which are iteratively solved for each of the rolling elements in the bearing taken into concern. The spin speeds of the rolling elements are shown to dampen and exponentially increase with respect to their angular positions. The outputs manifested through this work can be utilized to accurately predict shift of salient design attributes of an angular contact bearings through low and high-speed applications.

Tectonic evolution of the foreland basin of the SE Alborz Mountains, northern Iran

Along the SE Alborz Mountains in northern Iran, thrust loading seems to have been accompanied by post-Eocene transversal left-lateral faulting during the late Cenozoic. Here, the range-front North Semnan Fault has played a major role in the thrust loading and the development of the foreland basin. This fault has placed the Cenozoic succession upon the foreland basin from the early Miocene to the present. It is linked to the Peyghambaran Fault as the back thrust that began its reverse kinematics sometime between the middle Miocene to the latest Pliocene-Quaternary times. The foreland basin of the SE Alborz Mountains was later disrupted as a result of the reverse reactivation of a south-dipping pre-existing structure known as the Attary Fault during the latest Pliocene-Quaternary times. This fault cuts through the Pliocene-Quaternary deposits and exhibits left-lateral kinematics as well. It is suggested that the Arabia-Eurasia collision and the regional kinematic changes in the South Caspian Basin explain the reverse reactivation and the onset of the left-lateral kinematics along the Attary Fault. The above-mentioned post-Eocene transversal left-lateral faulting in the SE Alborz Mountains is compatible with a NW-oriented compression at the time. This indicates the rotations of the structural trends or a change in the direction of compression since then. Our findings revealed that contractional deformation is still active in the SE Alborz Mountains. It is also proposed that the foreland basin is not yet capable of underthrusting beneath the Alborz Mountains despite having a relatively thick basin fill.

Design, static structural analysis and topology optimization of a four wheeler connecting rod

The connecting rod is a critical component of an engine. The connecting rod is very important part of an engine which connects crank to piston. It forms a basic mechanism in which reciprocating motion of piston is converted to rotary motion. In an internal combustion (IC) engine, the connecting rod plays a vital role in transferring power. The trend with connecting rods is towards lowering the weight of components. Despite its lighter weight, it should be able to tolerate higher thrust loads. This work attempts to present the structural analysis and optimization of connecting rod using finite element analysis in ANSYS 18.0. CATIA V5 software is employed to model the connecting rod, this model is then imported in ANSYS 18.0 workbench for meshing and it is analyzed with the help of finite element method. In this work effort has been made to exploit static analysis and weight reduction opportunities for the production of forged steel. Initially, static load analysis is performed on the three materials which are aluminium, grey cast iron and forged steel. Structural performance of the connecting rod model is compared on basis of deformation, von-mises stress and equivalent strain. Next, optimization is performed on the forged steel connecting rod model with some weight reduction activities. The results of weight reduction is achieved with the help of optimization. Furthermore, the simulation results revealed that the forged steel performs well in terms of static load analysis and weight reduction of 11% is achieved for forged steel connecting rod.

Thrust Ripple Reduction in Linear Switched-Flux Machines via Additional Pole Optimisation

Linear switched-flux machines are a kind of permanent magnet machine with a passive ferromagnetic secondary. Therefore, they can achieve both a good performance and a low cost in long stroke applications. However, due to the end effect, these machines generate high detent force and on load thrust force ripples. There are several solutions in the literature that aim to minimise the thrust ripple. One of those solutions is the placement of additional poles in the ends of the machine. These can be passive, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i. e.</i> simple ferromagnetic teeth, or active, with additional magnets. The former is the most common solution in the literature. In this article, the optimal configuration of the additional poles is discussed via 4 additional pole sizing strategies, and the influence of the design variables and optimisation objectives is analysed. Then, a generic additional pole configuration is proposed, which combines a high effectiveness and a simple design. Finally, an experimental validation is carried out, and the measurements confirm the results from the optimisation.

SHIP MANOEUVRING PREDICTION BASED ON NUMERICAL TOWING TANK TECHNIQUE

A practical procedure is proposed in this paper to predict ship manoeuvrability. A three degrees of freedom MMG (Japanese Manoeuvring Mathematical Modelling Group)-type model is established to simulate rudder manoeuver. Propeller thrust and rudder loads are calculated by empirical formulas, whereas the hull forces as well as moment are determined with hydrodynamic derivatives which are derived from CFD (Computational Fluid Dynamics) computations. An own developed RANS (Reynolds-Averaged Naiver-Stokes) solver on the base of OpenFOAM is applied to simulate a range of PMM (Planar Motion Mechanism) tests and Fourier analyses of the computed results are carried out to obtain the required derivatives. In order to demonstrate the effectivity of the whole procedure and the RANS computations, the US (United States) combatant DTMB 5415 is taken as a sample for an application. Forced motions of surge, sway, yaw and yaw with drift for the bare hull with bilge keels are simulated. Thereafter, simulations of standard rudder manoeuvers, i.e. turning and zigzag, are performed by applying the computed derivatives. The results are compared with available measured data. It has been shown that the present procedure together with the RANS method can be used to evaluate the manoeuvrability of a ship since general good agreements between the simulated results and measured data are achieved.

Tectonostratigraphic framework in the eastern Korean continental margin, East Sea: Implication for evolution of the Hupo Basin

AbstractIntegrating seismic interpretation facilitates the discernment of tectonostratigraphic evolution in the eastern Korean continental margin, East Sea. The sedimentary succession of this margin is divided into three major seismic units based on distinct unconformities. These unconformities and their associated seismic characteristics indicate that the eastern Korean continental margin has experienced four evolutionary stages through extensional and subsequent two‐phase tectonic inversions. Early Miocene back‐arc opening of the East Sea triggered the extension of NNW–SSE and N–S trending rifts, resulting in non‐marine to deep‐marine deposition of typical rift‐related linked sedimentological systems in the eastern Korean continental margin. In the early Late Miocene, changes in plate motion and the subduction mode of the Japanese island (NW–SE compression) caused the positive inversion of extensional fault‐bounded half‐grabens in the eastern Korean continental margin, and the Hupo Basin was likely created by the regional flexural response. During this depositional period, hemipelagic sedimentation accompanied by episodic gravity‐controlled slope failures was predominant in the deep‐water environment. The subsidence of the Hupo Basin was enhanced by crustal shortening (E–W compression) that was induced by subduction initiation at the western margin of the Ulleung Basin during the late Early Pliocene (ca. 3.8 Ma). At that time, sedimentary environment gradually became shallower with time and coarse‐grained terrigenous input into the Hupo Basin began so that shallow‐ to deep‐marine sedimentation occurred. In the Quaternary period, the uplift of the Hupo Bank and coeval subsidence of the Hupo Basin were maintained by continued compressive neotectonics. The shallow‐ to deep‐marine deposition continued, but greater quantities of coarse‐grained terrestrial sediment were transported into the Hupo Basin due to combined effects on tectonics and eustasy. Based on the tectonostratigraphic reconstruction developed in this study, we propose that the Hupo Basin is likely a Late Miocene–Quaternary compression‐related basin induced by crustal or thrust loading.

Numerical modelling and dynamic response analysis of a 10 MW semi-submersible floating offshore wind turbine subjected to ship collision loads

The number of installed offshore wind turbines is continuously growing worldwide in recent years. Offshore wind farms are generally located near the coast close to traffic lanes and are exposed to the risk of collisions from visiting and passing ships. Potential consequences of collisions may vary from local structural damage to the detachment of turbine nacelles and rotors, and even tower collapse and capsizing of the turbine platform, causing significant economic loss and fatalities.This paper investigates ship collision responses of a semi-submersible floating offshore wind turbine (FOWT), i.e. the OO-STAR floater with the DTU 10 MW blades, using the nonlinear finite element code USFOS. The OO-STAR floater is made of post-tensioned concrete designed by Dr. techn. Olav Olsen. The striking ships are selected to be a modern supply vessel of 7500 tons and a shuttle tanker of 150,000 tons, representing respectively service/coastal merchant vessels and large passing vessels. Modelling of the FOWT in USFOS is described in detail including the OO-STAR floater, the DTU 10 MW turbine blade, the turbine tower, and the mooring system. The modelled hydrodynamic loads include buoyancy loads and motion induced radiation loads using the Morrison equation. The effects of external waves and currents are assumed to be small and ignored in all directions. Eigenmode analysis of the turbine model is performed to verify the established model.Global collision response analyses of the FOWT were performed in both parked and operating conditions. The ship resistance is modelled as nonlinear springs in USFOS containing force displacement curves simulated in LS-DYNA. In operating conditions, wind loads are introduced including wind thrust loads and wind induced torque to rotate the turbine blades. The changes of upstream wind speeds and rotor/wake interactions during collisions are neglected. The results are discussed with respect to energy absorption of the ship and the FOWT, and structural responses of the FOWT including global motions, nacelle accelerations, tower clearance, tower vibrations, and responses of the mooring system.

Foil stiffness optimization of a gas lubricated thrust foil bearing in enhancing load carrying capability

Air Foil Thrust Bearings (AFTB) are self-acting hydrodynamic members that support axial loads of high-speed rotating turbo-machineries. The load bearing capacity of such bearings mainly depends on the foil structure. The proposed Foil Thrust Bearing of 60 mm in diameter, designed and fabricated for performance evaluation, consists of a single top foil with an inner edge height equal to that of outer edge. This paper focuses on optimizing the foil stiffness in terms of foil thickness for steel and copper foil material with 60° and 90° sector angles. Various configurations of Gas Foil Thrust Bearings (GFTB) are tested for structural stiffness and thrust loads at higher operating speeds with an instrumented test rig dedicated for the purpose. Both geometric and operating parameters are varied to determine the best possible foil stiffness that enhances the load carrying capability of the Air Foil Thrust Bearing operating under hydrodynamic condition. CFD Simulation is also carried out to indicate the pressure distribution on the foil surface for the said bearing at actual boundary conditions.

Vibration Analysis to Detect Failure Bearing of Centrifugal Pump “Black Liquor Pump” in PT. Riau Andalas Pulp &amp; Paper (RAPP)

Bearing is one of machine element specialized to hold the load both radial and thrust load, also in supporting the shaft while operating. Because of a factor such as friction that occurred between bearing and shaft It would be influencing to machine’s performance is totally dependent to the currently used bearing and inefficiently operation. This research’s aim was to be analyzed what kind of failure and detected the cause of it failures that appear influencing to the bearing life time. The method used to research of that failures using relevant update issue such as literature study, surveying, collecting data. The result of this researching showed the cause of that bearing failure was happened at the cage of bearing and broken of bearing ring. Furthermore, supervising by control of a good maintenance schedule, making influence to the effect of load on reliability. So the remaining life of bearing had been investigated, showing that a potential decrease in remaining life significantly.

Aeroelastic response of a propulsive rotor blade with synthetic jets

Understanding the aeroelastic response of a propulsive rotor blade is critical to implementing active flow control techniques to mitigate blade structural vibration. In this experimental study, the coupling between rotor blade aerodynamic loading and first flap mode bending and torsion is explored. The three-bladed rotor is 2.58 m in diameter, and contains a NACA 0012 airfoil with zero pre-built twist. Each blade contains 20 high-performance synthetic jet actuators distributed along the span and are activated with a constant mean jet velocity of 66.3 m/s. The rotor was tested at rotor speeds, Ω of 250, 500, 750, and 1000 revolutions per minute (RPM) and collective blade pitch angles, θc of 2, 5, and 8 degrees. Rotor thrust and torque were measured using a high-capacity load cell, and the flow near the blade tip was measured using laser Doppler velocimetry (LDV) techniques. Blade bending and torsion was measured at three equally spaced radial stations on the blade root, middle, tip regions defined by r/R= 0.32, 0.64, and 0.96 respectively using three onboard electronic accelerometers. Synthetic jets reduce the near-wall streamwise velocity deficit and turbulence intensity in the near wall flow, improving the sectional lift coefficient of the blade and delaying flow separation which results in marginally higher thrust and lower torque loading of up to 7.4% and 4.3 % respectively. At higher rotor speeds of 750 and 1000 RPM, there is a pronounced non-linear increase in bending and torsion along blade span. In the blade tip region, the streamwise flow undergoes a significant decrease in velocity and momentum, which contributes to instabilities in the boundary layer with early-stage unsteady flow separation at θc= 8°. This is correlated to a dramatic rise in the baseline power spectral density (PSD) at the blade’s natural frequency along with an increase in root mean square (rms) of bending acceleration and blade pitch angle, where the maximum values measured are arms= 0.74 g and θrms= 1.45°.

A novel optimised nacelle to alleviate wind turbine unsteady loads

A comparative study of the effectiveness of an innovative optimised nacelle on fatigue loads alleviation and performance improvement in both upwind and downwind configurations has been conducted. The idea is to optimise wind turbine nacelles using flaps to push the flow towards outer spans, which leads to improved turbine performance, as well as mitigates unsteady loads, therefore, extending the fatigue life of wind turbine's components. Theoretical explanations indicate that in the case of upwind configuration, increasing downstream velocity leads to a reduction in turbine power. However, lower wind speeds seen by inner spans lead to mitigate thrust load generated by inner spans. In the case of downwind configuration, increasing upstream velocity leads to improve turbine power based on the turbine Euler equation, and pushing flow towards outer spans with higher lift/drag ratios leads to mitigate unsteady loads generated by inner spans. Experimental results show that using flaps to optimise the nacelle shape not only mitigates unsteady loads and therefore extends the fatigue lifetime of blades but also improves turbine power and yaw stability. Furthermore, using flaps in downwind configuration can compensate for the adverse effect of wind turbine yaw misalignment on the wind turbine performance and unsteady loads.

Power conversion performance of airborne wind turbine under unsteady loads

The study presents the systematic analysis of power conversion performance of the airborne wind turbine (AWT) using time-resolved air loads. The power harvesting behavior of the rotating blades in shell configuration is numerically investigated to analyze the influence of wind shear, yawed and tilted inflows at design operating conditions. An inherently unsteady scheme of the sliding mesh is incorporated to capture the complex flow field across the 3-bladed rotor. The fully-resolved computations closely match the expected results derived from the empirical calculations. The conversion performance supplements the turbine's power curve as a means of determining the distribution of aerodynamic forces, performance coefficients, vortex structure and shell thrust loadings. The time-marching response of the AWT gradually attains steady flow characteristics after two rotation periods when the wind shear profile is fully aligned with the rotor's axis of rotation. This yields a beneficial gain of 64% more power output with the rotor in shell configuration than those of the bare configuration. Meanwhile, cyclic fluctuations (±21%) significantly undermine the continuous production of power in the case of skewed flow conditions. Moreover, the flow misalignment causes a localized shifting of effective forces on the rotor plane due to the intricate impact of the shell structure.

In situ behaviour of an instrumented ring subjected to incipient TBM steering around a curve

During the TBM tunnelling of curved tunnel sections with passively articulated shield tails, the concrete segmental rings are susceptible to ring deformation and structural damage. In this paper, the in situ loading condition and response of the CAM4 instrumented ring in the Crossrail’s Thames tunnel (CTT) during tail seal passage at incipient TBM steering around a left curve are examined in detail. The field data comprises selected TBM data, the distributed strain measurements of a Brillouin Optical Time Domain Reflectometer (BOTDR) and the output quantities of vibrating wire strain gauges (VWSGs) and biaxial micro-electro-mechanical system (MEMS) tiltmeters. The field data was completed with relevant analytical models (Gil Lorenzo, 2019a, 2021c) and compared with the outputs of the finite element modelling conducted alongside (Gil Lorenzo, 2021a, 2021b). It was found that the eccentric tail seal passage was the main cause of the highest lining pressures and pressure gradients detected at the early stages of tunnelling. The machine turned around the thrust symmetry axis so that the shield posture changed from vertical and upwards to left and inwards. The transverse jack forces near the CAM4 ring switched orientation from downwards to rightwards. The locking mechanism of opposing TBM transverse actions during the eccentric tail seal passage triggered the ring deformations in the unsupported tunnel, which became essentially irrecoverable. The radial rotations of the outer springline segment were largely affected by the interfacial quality between ram shoe and segment first and between segments once the next ring was erected. The moderate sealing pressure gradients and the effective ring coupling ensured by the high thrust loads translated into a very limited ring distortion. The top half of the unbedded ring behaved as an arch-like structure with the crown segment being supported by the neighbouring segments. The in situ hoop curvatures were the result of ring ovalisation developed under the sealing pressure gradients and, in the first TBM cycle, the segment interaction with the hydraulic jacks. A temporary intrados front longitudinal crack near the mid length of the outer springline segment was detected at the time of incipient machine turning. The crack was caused by the combination of the spalling stresses between ram shoes with the front hoop tensile stresses typical of segmental rings loaded at the rear. Initial in-plane angularities of longitudinal joints with contact at the segment front can be corrected by the sequential loading of the ring from rear to front. There was good agreement between the in situ and FE-computed deformational quantities.

Decentralised optimisation for large offshore wind farms using a sparsified wake directed graph

Considering the wake effects, developing an efficient wake-based graph clustering algorithm is essential for the decentralised coordinated online control of large offshore wind farms. In this study, the idea of graph sparse is introduced into the algorithm, in which the sparsified wake-directed graph is generated while preserving the original wake-directed graph critical wake coupling relationship between turbines. The key is to construct the original wake-directed graph by quantifying wake intensity and applying the graph sparseness constraints algorithm to achieve an ultra-sparse wake subgraph. Based on the sparsified wake-directed graph and wake intensity weighting matrix, the wind farm is split into almost uncoupled cluster subsets to establish decentralised sparse communication architectures. By doing so, a decentralised sequential quadratic programming optimisation strategy is proposed to solve a nonconvex optimisation problem, in which the thrust load problem is converted into a power controlling optimisation problem, and the thrust load distribution is balanced using the power margin. Simulation results reveal that the proposed scheme can maximise wind farm power production while minimising thrust loads in various turbulence intensities, making it functional for real-time operations on a large-scale wind farm.

Study on cracking behaviors of shield tunnel segment with annular interfacial unevenness under jacking thrust force

As one of the major engineering disasters in tunnel structures, segment lining cracks have significant impacts on the carrying capacity and durability of shield tunnels. This study focused on the lining cracking problems that are induced by annular interfacial unevenness during construction; a three-dimensional finite element model of shield tunnel linings was established that uses particular gasket elements and considers the assembly tolerance between segments and dowel pads at the annular interface. Through the numerical simulation, the lining’s structural deformation and crack propagation in the presence of the annular joint’s unevenness were studied by adjusting the initial gap and the normal stiffness modulus of the dowel pad at the annular interface. The numerical results indicate that the cracks induced by the jacking thrust force are initiated in hang holes in the midspan of the segments and subsequently develop along the longitudinal direction. In addition, the critical thrust loads for crack occurrence and the crack length are directly related to the initial gap and the stiffness modulus of the dowel pads at the annular interface of the segments. Moreover, the higher the assembly tolerance and the dowel pad stiffness modulus, the more serious will be the longitudinal cracks. It is confirmed that the use of appropriate dowel pads can effectively control the initiation and development of longitudinal cracks and enhance the structure’s carrying capacity.

Investigation of the Influences of Thrust Loads Resulted by Helix Angle Directions of Planetary Gear Sets on Bearing Power Losses in Automotive Planetary Gear Trains

In the recent automotive industries, automotive technologies for improving fuel efficiency have focused on the developments of reducing power losses in a transmission. As a well-developed and conventional power transmitting system, an automatic transmission is still widely used in many automotive vehicles. The automatic transmission is co-axially designed with several planetary gear sets and other mechanical parts. The co-axial arrangements and gear helix angles make the transmission necessarily include bearings for supporting loads and allowing relative rotations. In this study, the influences of thrust loads yielded by helix angle directions of planetary gear sets on bearing power losses are presented by performing the structural and power loss analysis. Bearing power losses consist of mechanical and spin power losses. For calculating thrust loads and bearing rotations, a complete transmission model is constructed by using an example structure, and structural analysis is performed for the combinations of helix angle directions of the gear sets. Finally, bearing power losses are computed by using the bearing power loss model, and the results of the entire combinations of helix angle directions are discussed.

Cavitation funnel effect: Bio-inspired leading-edge tubercle application on ducted marine propeller blades

Cavitation is an ever-present issue in the maritime industry as it causes damage to the propeller in the form of erosion, reducing hydrodynamic performance and increasing the underwater radiated noise (URN) level generated. Therefore, containing cavitation on marine propellers is an important area to research in order to reduce structural damage, efficiency loss and noise pollution. Recently there has been growing research in the leading-edge (LE) tubercles located on Humpback whale pectoral fins that have been attributed to give the whales superior manoeuvrability through prolonged flow attachment and have shown to improve hydrodynamic performance on marine applications.This paper assesses the sheet cavitation containment capability of the LE tubercles on a benchmark ducted propeller blade in both heavy and light cavitating conditions. The analysis is carried out over a range of operating conditions using commercial code STAR-CCM+ with the implicit unsteady Improved Delayed Detached Eddy Simulation (IDDES) method and the Schnerr-Sauer cavitation model. The investigation encompassed two tubercle designs with varying geometrical configurations of wavelength while maintaining the amplitude.In summary, it was found that LE tubercles as applied to the Kaplan propeller blade has presented a cavitation funnel effect which can successfully reduce the sheet cavitation development by a maximum of 50%, while enhancing the total thrust coefficient in all operating conditions by a maximum of 10%. Comparing at the same thrust loading coefficient, the propulsive efficiency in heavy-cavitating conditions can be improved by a maximum of 6.5%.

OC6 semisubmersible response to waves in offset positions caused by constant thrust loads

In 2019, a semisubmersible floating wind foundation was tested in the Concept Basin of MARIN in waves and under several levels of constant thrust. This paper compares the motion of the floater and the tensions in its mooring lines in waves under different levels of thrust. The end goal of this work is to present experimental results of the response of a floating wind turbine semisubmersible under the combined effects of waves and constant thrust. As these new experiments were focused on the hydrodynamic response of the floater in its offset position, their results represent reference data for the validation of numerical tools that account for this offset in the calculation of the hydrodynamic loading and response.