Loire-Atlantique

High Froude Number Experimental Investigation of the 2 DOF Behavior of a Multihull Float in Head Waves

Kerdraon, Paul (VPLP Design, France and Ecole Centrale Nantes) | Horel, Boris (Ecole Centrale Nantes) | Bot, Patrick (Naval Academy Research Institute) | Letourneur, Adrien (VPLP Design) | David Le Touzé, David (Ecole Centrale Nantes)

OnePetroFebruary, 2021

Dynamic Velocity Prediction Programs are taking an increasingly prominent role in high performance yacht design, as they allow to deal with seakeeping abilities and stability issues. Their validation is however often neglected for lack of time and data. This paper presents an experimental campaign carried out in the towing tank of the Ecole Centrale de Nantes, France, to validate the hull modeling in use in a previously presented Dynamic Velocity Prediction Program. Even though with foils, hulls are less frequently immersed, a reliable hull modeling is necessary to properly simulate the critical transient phases such as touchdowns and takeoffs. The model is a multihull float with a waterline length of 2.5 m. Measurements were made in head waves in both captive and semi-captive conditions (free to heave and pitch), with the model towed at constant yaw and speed. To get as close as possible to real sailing conditions, experiments were made at both zero and non-zero leeway angles, sweeping a wide range of speed values, with Froude numbers up to 1.2. Both linear and nonlinear wave conditions were studied in order to test the limits of the modeling approach, with wave steepness reaching up to 7% in captive conditions and 3.5% in semi-captive ones. The paper presents the design and methodology of the experiments, as well as comparisons of measured loads and motions with simulations. Loads are shown to be consistent, with a good representation of the sustained non-linearities. Pitch and heave motions depict an encouraging correlation which confirms that the modeling approach is valid.

OnePetro

doi: 10.5957/jst/2021.6.1.1

SNAME

SNAME-JST-2021-01

Journal of Sailing Technology

Country:

Oceania (0.46)
Europe > France > Pays de la Loire > Loire-Atlantique > Nantes (0.25)

Industry: Leisure & Entertainment > Sports > Sailing (1.00)

SPE Disciplines:

Data Science & Engineering Analytics > Information Management and Systems (0.93)
Reservoir Description and Dynamics > Reservoir Characterization (0.70)
Reservoir Description and Dynamics > Formation Evaluation & Management (0.61)

Technology: Information Technology > Artificial Intelligence (0.68)

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Basin Test Validation of New Pendulum Offshore Wind Turbine

Ducasse, Marie-Laure (SAIPEM S.A) | Colmard, Christophe (SAIPEM S.A) | Delahaye, Thierry (SAIPEM S.A) | Vertallier, Florent (SAIPEM S.A) | Rigaud, Stéphane (SAIPEM S.A)

OnePetroMay, 2019

A new Floating Sub-Structure concept has been developed for Floating Offshore Wind Turbine (FOWT). It consists of a floating tubular sub-structure connected with tendons to a counterweight providing pendulum-restoring forces. The whole floating system is anchored with six low-tension mooring lines. Model tests were carried out in wave basin test facilities at Ecole Centrale de Nantes to provide insight into hydrodynamic behavior of the system under operational and extreme wave conditions. Two installation depths were studied: intermediate and deeper water depth configurations with 75 and 150 meters water depth respectively. Two wind turbine capacities were tested: 8MW and 12MW. Responses of the system were investigated under different irregular wave conditions: operational condition with significant wave height Hs = 4 m and two extreme wave conditions with significant wave heights Hs=8m and 14 m. Sensitivity tests were also performed for various wave periods Tp (Tp = 8, 12 and 16 seconds). Results of these tests demonstrate that the floater is extremely stable with very low pitch motions as well as low vertical & horizontal accelerations both in operational and extreme wave conditions. Detailed results are presented in this paper. This stable dynamic behavior is obtained because natural periods of the floater are far away from wave spectrum peak and it thus leads to low dynamic loads in the mooring lines. This beneficial seakeeping feature and the possibility of accommodating even larger wind turbines with minor modifications on the floater design make the proposed FOWT a relevant concept for the upcoming offshore floating wind market.

OnePetro

doi: 10.4043/29623-MS

OTC

OTC-29623-MS

Offshore Technology Conference

Country:

North America > United States > Texas (0.28)
Europe > France > Pays de la Loire > Loire-Atlantique > Nantes (0.25)

Industry: Energy > Renewable > Wind (1.00)

SPE Disciplines:

Health, Safety, Environment & Sustainability > Sustainability/Social Responsibility > Sustainable development (1.00)
Facilities Design, Construction and Operation > Offshore Facilities and Subsea Systems > Mooring systems (1.00)
Facilities Design, Construction and Operation > Offshore Facilities and Subsea Systems > Floating production systems (1.00)
Facilities Design, Construction and Operation > Facilities and Construction Project Management > Offshore projects planning and execution (1.00)

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Towards Unsteady Approach for Future Flutter Calculations

OnePetroOctober, 2018

In prior work to define an improved hydrodynamic approach to flutter calculations, Centrale Nantes, Bureau Veritas Marine & Offshore and Farr Yacht design investigated the possibility of defining a linearized unsteady hydrodynamic model using a fluid response database coming from a series of 2D unsteady RANSE computations. The approach is compared to the Theodorsen theory. The linearized hydrodynamic model was used in a strip theory model for frequency domain flutter analysis. In this latest work, the IMOCA 2006 keel which has been used previously in frequential domain flutter calculation is also analyzed using an alternative and more accurate solution, featuring a fully coupled FSI modal approach with CFD. As described in the literature, the results present a large impact of the unsteadiness on the phase and module for both lift and moment with a fairly good match compared to Theodorsen theory. The implementation of the results on a frequency domain flutter analysis tool reduces the critical speed for the studied model. Thus the results are closer to the 3D modal CFD approach which gave an lower critical speed.

OnePetro

doi: 10.5957.jst.2018.07

SNAME

SNAME-JST-2018-07

Journal of Sailing Technology

Country: Europe > France > Pays de la Loire > Loire-Atlantique > Nantes (0.25)

Industry:

Leisure & Entertainment > Sports > Sailing (1.00)
Energy (0.94)

SPE Disciplines:

Reservoir Description and Dynamics > Reservoir Simulation (0.68)
Data Science & Engineering Analytics > Information Management and Systems (0.68)

Technology: Information Technology (1.00)

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2D Simulations of Breaking Wave Impacts on a Flat Rigid Wall – Part 2: Influence of Scale

Guilcher, P. M. (ENSTA-Bretagne, NextFlow Software) | Jus, Y. (HydrOcean) | Brosset, L. (GTT (Gaztransport & Technigaz))

OnePetroJune, 2018

ABSTRACT Four different breaking wave impacts against a flat rigid wall have been numerically simulated in 2D at two different scales, scale 1 and scale 1:6, with Froude-similar inflow conditions but keeping the same fluids (water and air) at both scales. Sufficiently refined discretizations have been used in order to adequately capture the impulsive loads at wall. The simulations have been performed with SPH-Flow, a CFD software, developed by HydrOcean and Ecole Centrale Nantes (ECN), which solves the compressible Euler equations for liquid and gas thanks to a Smoothed Particle Hydrodynamics (SPH) method. The four waves have been selected in order to generate wave shapes just before impact representative of those leading to the largest loads during 2D sloshing model tests for low filling levels or during wave impact tests in flumes. A flip-through impact and three gas-pocket impacts with different sizes of the gas cavity have been chosen. Results obtained at scale 1 have been presented in Part 1 of this work (Guilcher et al., 2014). Results at scale 1:6 are presented in this Part 2, mainly by pressure maps P(y, t), where y is the vertical location of any point at wall and t is the time, and by time-traces of the different components of the energy, in the same way as for results at scale 1 in order to enable an easy comparison. Results at both scales are compared after scaling the results from scale 1:6 as though the flows were in complete similarity. Inconsistencies are shown and explained by unscaled gas and liquid compressibility. INTRODUCTION Context The context of this study is the sloshing assessment of LNG membrane tanks on floating structures based on sloshing model tests. Those tests are usually performed with model tanks at scale 1:λ (λ = 40) filled with water and a mixture of gases chosen in order to have the same gas-to-liquid density ratio as on board ships with Natural Gas (NG) and Liquefied Natural Gas (LNG). Irregular tank motions, calculated at full scale by a sea-keeping software, are imposed to the model tank by a six-degree-of-freedom hexapod after having been down-scaled according to Froude similarity. This down-scaling simply means that amplitudes are divided by λ and times are divided by (equation).

OnePetro

ISOPE

ISOPE-I-18-697

The 28th International Ocean and Polar Engineering Conference

Country:

Asia (1.00)
Europe > France > Pays de la Loire > Loire-Atlantique > Nantes (0.24)

Industry: Energy > Oil & Gas > Upstream (1.00)

SPE Disciplines: Facilities Design, Construction and Operation > Natural Gas Conversion and Storage > Liquified natural gas (LNG) (1.00)

Technology: Information Technology (0.46)

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New Wave Spectrums Models Developed Based on HOS Method

Song, Jiaqi (Shanghai Jiao Tong University) | Zhuang, Yuan (Shanghai Jiao Tong University) | Wan, Decheng (Shanghai Jiao Tong University)

OnePetroJune, 2018

ABSTRACT HOS-ocean is an open-source solver for the simulation of nonlinear waves in open sea based on High-Order Spectral method, developing by Ecole Centrale Nantes, LHEEA Lab. For the recent release, the wave spectrum is limited in JONSWAP spectrum. In this paper, P-M spectrum and ITTC 2-parameter spectrum are introduced into HOS-ocean solver. The validations of new spectrums are taken by the statistical analysis on different probes located in domain. A series of long time and large domain simulations of wave fields with different directionality evolution are taken for the detection of freak waves. All the works have developed the application range of HOS-ocean solver. INTRODUCTION For ships and offshore platforms which are usually operating in open seas, the extreme sea-states could bring large potential risk. In those conditions, the freak waves with large height and rapidly changing of shape may appear, which can cause fatigue and damages to ships and structures. Therefore, the study of extreme waves becomes an important work to do. However, these extreme waves are both high-nonlinear and directional. To obtain the formation and propagation mechanism is not a easy thing. There are main two ways to modal extreme wave condition. The wave tank is the most direct and reliable method to make rough waves and measure the movement and loads of the ship or platform models. But this approach need complex preparation and expensive facilities. The extreme condition also could be discounted considering the limitation of the scale of basin. Another way is numerical simulation which is also very challenging. For the randomness of the occurrence of freak waves, to get those events, long time simulation and large domain are required. The potential methods are suitable to solve long-time evolution. But in large domain condition the Boundary Element Method, one of the most classical methods, may be too slow to simulate the square kilometers of open ocean evolution. The High-Order Spectral (HOS) method was separately proposed by West (1987), Dommermuth and Yue (1987). This method exhibits high efficiency and accuracy thanks to its pseudospectral formalism and shows its ability to handle the evolution of the free surface of large wave fields in long time propagation considering highly nonlinear effects.

OnePetro

ISOPE

ISOPE-I-18-046

The 28th International Ocean and Polar Engineering Conference

directional function, directionality, ducrozet, extreme wave, freak wave, free surface, ho method, hos-ocean, initialization, ittc 2-parameter spectrum, JONSWAP spectrum, long time simulation, propagation, Simulation, spectrum, Upstream Oil & Gas, wave field, wave height, wave spectrum

Country:

Asia (0.47)
Europe > France > Pays de la Loire > Loire-Atlantique > Nantes (0.24)

Industry: Energy > Oil & Gas > Upstream (0.34)

SPE Disciplines:

Data Science & Engineering Analytics > Information Management and Systems (1.00)
Reservoir Description and Dynamics (0.88)

Technology: Information Technology (1.00)

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Validation of INNWIND.EU Scaled Model Tests of a Semisubmersible Floating Wind Turbine

OnePetroMarch, 2018

The subject of this study is the verification and the validation of existing numerical codes for floating offshore wind turbine structures using wave tank model tests as part of the INNWIND.EU project. A model of the OC4-DeepCwind semisubmersible platform, together with a Froude-scaled rotor model, is tested in a combined wind-and-wave basin. The simulation environment comprises a multibody approach with hydrodynamic and aerodynamic loads and mooring line forces. The focus of this paper is the validation of the hydrodynamics of a modified model hull shape, which compensates for the excess mass of the nacelle. The results show that the simulation model agrees well with the experiment. Introduction At offshore sites with higher water depths, the use of floating structures is more reasonable than the use of large fixed-bottom structures such as monopiles, tripods, and jackets as described by James and Costa Ros (2015) and Beiter et al. (2016). A floating wind turbine experiences many different loading conditions. Floater motion with six degrees of freedom (6DOF) as well as aerodynamic and hydrodynamic loads have to be considered. At this point, few floating wind turbine prototypes have been built, e.g., the Fukushima FORWARD project, which was started in 2013. To increase the reliability of wind turbines for floating applications, validated simulation codes are needed to predict the forces on the system structure and their dynamic responses for combined stochastic wave and wind loadings (Müller et al., 2016). Although several verification tests have been done by Robertson et al. (2013), Huijs et al. (2014), and Müller et al. (2014), for example, the validation of coupled simulation of floating wind turbines is still part of current research. This work is associated with task 4.2 of the INNWIND.EU project as part of its model test campaign at LHEEA, École Centrale de Nantes (ECN), France, in 2014. INNWIND.EU, with its 27 European partners, aims to improve the design of beyond-state-of-the-art 10–20 MW offshore wind turbines, including hardware demonstration. A scaled 10 MW model of the OC4-DeepCwind semisubmersible was built at the University of Stuttgart, together with a Froude-scaled wind turbine with low Reynolds rotor blades, developed by the Politecnico di Milano.

OnePetro

doi: 10.17736/ijope.2018.fv04

ISOPE

ISOPE-18-28-1-054

International Journal of Offshore and Polar Engineering

Country:

Europe > Germany > Baden-Württemberg > Stuttgart (0.26)
Europe > France > Pays de la Loire > Loire-Atlantique > Nantes (0.24)
Asia > Japan > Tōhoku > Fukushima Prefecture > Fukushima (0.24)

Genre: Research Report > New Finding (0.34)

Industry: Energy > Renewable > Wind (1.00)

SPE Disciplines:

Health, Safety, Environment & Sustainability > Sustainability/Social Responsibility > Sustainable development (1.00)
Facilities Design, Construction and Operation > Offshore Facilities and Subsea Systems (1.00)

Technology: Information Technology > Modeling & Simulation (0.48)

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Numerical Simulation of Highly Nonlinear Sloshing in a Tank Due to Forced Motion

Scolan, Yves-Marie (ENSTA Bretagne) | Brosset, Laurent (GTT (Gaztransport & Technigaz))

OnePetroMarch, 2017

FSID stands for free-surface identification. This is the name of a computational code that simulates highly nonlinear 2-D free-surface flow in potential theory. This theoretical framework is shown to be still valid to describe the interaction between two nonmiscible fluids (gas/liquid) in a closed tank, whatever the density ratio. That is why GTT has used FSID for years. This code quickly generates flow conditions before impact, hence providing more sophisticated computational fluid dynamics (CFD) codes with initial flow conditions. The last developments of the code concern the forced motion in three degrees of freedom and two-phase flow modeling. In the present paper the governing equations of the model are presented along with illustrative results. Introduction To study the consequences of unscaled properties on the sloshing loads derived from model tests, GTT has undertaken a research program where numerical simulations play an important role. Indeed, numerical simulation enables the inclusion of progressively more physics into a model and is therefore very relevant to the disentanglement of different influences. The strategy is based on studies of 2-D single wave impacts, varying the fluid properties at a given scale or varying the scales with the same properties. Many long-term partnerships have been developed with different universities, research centers, and laboratories in order to follow this strategy. This allows the comparison of results for the same problem obtained with different numerical methods. For instance, compressibility effects have been studied by NextFlow/Ecole de Centrale Nantes with smoothed particle hydrodynamics (SPH) calculations (Guilcher et al., 2013, 2014) or by Eurobios/ENS-Cachan with a finite volume method (Costes et al., 2014). Those approaches solve the Euler compressible isentropic equations. Phase change influence has been studied recently by Airbus Defense and Space using the Hertz-Knudsen model with a finite volume method (Behruzi et al., 2016).

OnePetro

doi: 10.17736/ijope.2017.jc678

ISOPE

ISOPE-17-27-1-011

International Journal of Offshore and Polar Engineering

Country: Europe > France > Pays de la Loire > Loire-Atlantique > Nantes (0.24)

Industry: Energy > Oil & Gas > Upstream (1.00)

SPE Disciplines:

Data Science & Engineering Analytics > Information Management and Systems (1.00)
Reservoir Description and Dynamics > Reservoir Fluid Dynamics (0.88)

Technology: Information Technology > Mathematics of Computing (0.91)

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Influence of Jet Flow on the Aerodynamics of a Floating Model Wind Turbine

Klein, Levin (University of Stuttgart) | Schulz, Christoph (University of Stuttgart) | Lutz, Thorsten (University of Stuttgart) | Krämer, Ewald (University of Stuttgart)

OnePetroJune, 2016

Abstract Within tests during the INNWIND.EU project, a model offshore wind turbine has been placed in the jet of a wind generator whose outlet size is similar to the rotor area. This paper deals with the CFD (Computational Fluid Dynamics) simulation of this turbine in a simplified experimental environment. As this is a preliminary study to evaluate the influence of the jet flow, no comparison to experimental results is done. The loads on the wind turbine are evaluated and compared to a uniform inflow case. The study is focused on the thrust which is the biggest acting force and most important for floating turbine motion. The results show that the thrust of the whole rotor is comparable to the unifonn inflow case although there are bigger differences in the spanwise distribution for a single blade. Hence, it can be concluded that the model turbine in the jet flow is suitable for the experiments as long as it is guaranteed that the turbine is placed in the center of the jet at the investigated distance to the wind generator. INTRODUCTION The INNWIND. EU Project is dealing with investigations on large offshore wind turbines of the 1O:MW class. Basis of the investigations is the three bladed horizontal axis 10 MW DIU reference turbine (Bak, Zahle, Bitsche, Kim, Yde, Henriksen, Andersen; Natarajan, Hansen). To install this large turbine at offshore sites, new platform concepts are investigated for bottom fixed as well as for floating installation. Different codes are used to simulate the turbine on the platform. To simulate the floating platform, codes for aerodynamics, hydrodynamics as well as structural analysis are combined. The only way to validate the numerical results experimentally within the project is wave tank testing using a scaled model of the platform. These tests have been performed at Ecole Centrale de Nantes, France (ECN). On the one hand platform only tests have been conducted to evaluate the suitability of the hydrodynamic simulations using a Froude scaled model of the platform. On the other hand tests of the entire system, including turbine and platform have been performed. The geometric scaling factor is 1/60 and the scaling factor for the velocity is 1/60. Therefore a model turbine has been developed by Politecnico di Milano, Italy (POLIMI). It operates at the same tip speed ration (TSR) as the DTU reference turbine and has been designed for similarity of the thrust coefficient using a low Reynolds number airfoil (RG 14) for all sections excluding the cylindrical root. As it is operating at very low Reynolds numbers (~45000 in the present case), it is not possible to match the power coefficient of the full size turbine which is much higher than for the model turbine. As the motion of the turbine is mostly influenced by forces, the mismatch in power and respectively torque is expected to be negligible and the thrust is representative. This is a common approach, also presented in other publications like Make, Vaz, Fernandes, Bunnester and Gueydon (2015), which deals with the need of blade redesign for scaled model offshore wind turbines using CFD and BEM (Blade Element Momentum). Gueydon, Venet and Fernandes (2015) are presenting an optimization process for the simulation of the aerodynamics of a floating offshore wind turbine with a BEM approach. To match the measured Cp and CT they adjusted the polars with different approaches. Additionally, they show that the thrust coefficient in the referenced measurements could be match best using 3D CFD simulations.

OnePetro

ISOPE

ISOPE-I-16-407

The 26th International Ocean and Polar Engineering Conference

aerodynamic, jet flow, Model Wind Turbine, renewable energy, subsea system, wind energy

Country:

Europe > France > Pays de la Loire > Loire-Atlantique > Nantes (0.24)
Asia > Middle East > Lebanon > Beqaa > Zahle (0.24)

Industry: Energy > Renewable > Wind (1.00)

SPE Disciplines: Facilities Design, Construction and Operation > Offshore Facilities and Subsea Systems (1.00)

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Green Water and Wave impacts are amongst the most severe and dangerous loads that effect offshore structures. Even if many design procedures are well established, they can over or underestimate the structural loading in complex conditions as they are outside of their application scope. This therefore leads to over designed and expensive structures, or to under designed structures leading to dangerous situations. The calculation of complex structure loadings is therefore a key issue for engineering companies. HydrOcean, in cooperation with Ecole Centrale de Nantes and Next Flow, has developed the SPH-flow software, based on the SPH method. This paper details the development and validation of a methodology dedicated to the evaluation of green water loads on offshore structures. This methodology was developed in cooperation with Total and Technip. Comparisons with experimental results are provided. The following aspects will be addressed in this article:Validation of wave propagation by the SPH method and development of a forcing with a Higher-Order Spectral method to simulate open sea. Validation on slamming and green water cases. The experiments were performed in the wave tank of the Ecole Centrale de Nantes. SPH calculations are performed under similar conditions, to compare the results obtained with the experiments. Application of the developed and validated methodology for the assessment of green-water event on offshore structures.

OnePetro

SNAME

SNAME-TOS-2016-016

SNAME 21st Offshore Symposium

Artificial Intelligence, boundary, Computation, Ecole Centrale, february 2016, greenwater event, Houston, inlet outlet boundary, naval architect, outlet boundary, particle, proceedings, propagation, Simulation, solver, st offshore symposium, texas texas section, Upstream Oil & Gas, wave train

Country:

Europe > France > Pays de la Loire > Loire-Atlantique > Nantes (0.47)
North America > United States > Texas (0.21)

Industry: Energy > Oil & Gas > Upstream (1.00)

SPE Disciplines:

Reservoir Description and Dynamics (1.00)
Data Science & Engineering Analytics > Information Management and Systems (1.00)

Technology: Information Technology > Artificial Intelligence (0.48)

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A Design Framework for Sliding Foundations: Centrifuge Testing and Numerical Modelling

Wallerand, Regis (Subsea 7) | Stuyts, Bruno (Cathie & Associates) | Blanc, Matthieu (IFSTTAR) | Thorel, Luc (IFSTTAR) | Brown, Neil (Subsea 7)

OnePetroMay, 2015

Abstract Pipeline end termination (PLET) structures used in subsea deepwater developments are subjected to significant axial expansion forces arising from heating up and cooling down of the incoming HP/HT pipelines. Resisting these forces with a fixed foundation solution such as a skirted mudmat or hybrid foundation with pin piles would lead to excessive foundation sizes when axial expansions are large. Allowing the foundation to slide over the seabed as a whole could lead to a more economical solution (Bretelle & Wallerand, 2013). A study has been initiated to develop a design framework for sliding PLET foundations, allowing a controlled movement of the foundation during its design life. Such a performance-based design needs to characterize displacements and rotations of the foundation during several cycles of large-amplitude foundation movement in order to provide a robust design. Series of scale model tests in the centrifuge of IFSTTAR in Nantes have been performed to validate the performance based design approach outlined by this study. These tests have focused on the influence of the interface roughness and degree of soil consolidation to characterize the soil response under in-plane loading.

OnePetro

doi: 10.4043/25978-MS

OTC

OTC-25978-MS

Offshore Technology Conference

Country:

North America > United States > Texas (0.28)
Europe > France > Pays de la Loire > Loire-Atlantique > Nantes (0.25)

Industry: Energy > Oil & Gas > Upstream (1.00)

Oilfield Places: Europe > United Kingdom > England > London Basin (0.91)

SPE Disciplines:

Data Science & Engineering Analytics > Information Management and Systems (1.00)
Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Piping design and simulation (0.34)

Technology: Information Technology > Artificial Intelligence (0.71)

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