P. Ferrant

• MEng, PhD, HDR
• Professor Emeritus at École Centrale de Nantes

This article presents a wave energy converter exploiting the pitch of a floating body moored to the seabed. When the floating body tilts under the action of an incoming wave, a movable mass, placed inside the hull, moves relative to the floating body and actuates an electrical generator. Most devices of this type have the drawback that the moving m...

This paper presents the experimental proof-of-concept of a nonlinear, deterministic wave prediction method. The method is based on the adapted version of the HOS-NWT wave model and uses wave-induced velocity profiles as input information on the sea state. Unlike most HOS approaches, it does not need any optimization procedure or data assimilation s...

This study aims at the experimental investigation of wave-induced motions and loads of a containership model without forward speed in -120 degree oblique regular waves to study the influence of the wave steepness and provide reference data for future benchmark studies. A mooring system with 4 horizontally arranged spring lines was used to maintain...

An alternative expression of the time domain free surface Green’s function is proposed. Its source and image source contribution satisfies the homogeneous Neumann condition on the mean free surface, therefore it can be useful for the boundary element method based on the double-body flow linearization. Furthermore, it is proved that it is also the s...

An efficient methodology for simulating nonlinear irregular waves in a Computational Fluid Dynamics (CFD) solver is proposed. The High Order Spectral (HOS) method is used to generate nonlinear irregular waves in an open ocean and a numerical wave tank. The inverse Fast Fourier Transforms (FFTs) and multi-dimensional interpolation from the HOS simul...

The coupled (Potential theory and Navier–Stokes) solver is applied to simulate the interaction of sea waves with substructure of floating offshore wind turbines (FOWT) platform, notably similar to the OC3 Hywind SPAR structure. The intention is to develop a numerical tool that allows the study of the survivability of floating structures in extreme...

This paper presents a comparative study of long-time irregular waves and equivalent design waves (EDW) in terms of geometric similarity and probability of exceedance (POE) distribution of the wave crest. For a proper comparison between the two wave types, the same nonlinear model was applied in the wave generation by application of the Higher-Order...

Extreme waves can be modelled in a numerical wave tank (NWT) as a focusing wave in order to generate events that are crucial for designing any offshore structures. The focused wave generation implemented in the completely nonlinear potential solver Higher Order Spectral method (HOS-NWT) with the time-reversal technique was used in the present work....

A consistent frame for the numerical simulation of lowering operations is investigated in this paper from a new wave-structure coupling. The mechanical modeling is based on the Composite-Rigid-Body Algorithm, which is able to simulate the nonlinear dynamics of multibody systems. The hydrodynamic model is based on the weak-scatterer approach, which...

This paper examines the hydroelastic response of a monopile structure, supporting an offshore wind turbine. A new numerical simulation tool is presented, coupling a nonlinear potential flow solver to a structural model based on modal superposition. The hydrodynamic solver is based on the Weak-Scatterer (WS) approach and assumes small perturbations...

In this paper, the comparative study carried out for focused wave interaction with a moving cylinder in ISOPE-2020 is reported. The fixed cylinder cases are reported in the companion paper as Part A (Sriram, Agarwal, Yan et al., 2021). The paper discusses qualitative and quantitative comparison between four different numerical solvers that particip...

This paper proposes an efficient potential and viscous flow decomposition method for wave-structure interaction simulation with single-phase wave models and two-phase Computational Fluid Dynamics (CFD) solvers. The potential part-represents the incident waves-is solved with spectral wave models; the viscous part-represents the complementary perturb...

Optimizing the production of wave energy converters using Model Predictive Control (MPC) requires a real-time, deterministic prediction of the waves arriving at the device. This study presents a new method for deterministic sea wave prediction, using the horizontal velocity profile over the water column as a boundary condition for a dedicated nonli...

This paper presents an original contribution to the coupled hydroelastic simulation of offshore wind turbines foundations. A non-linear coupled simulation tool has been developed to calculate the response of these systems. The hydrodynamic loads are computed by the non-linear potential flow solver WSCN , developed at Centrale Nantes and based on th...

In wave-structure interaction problems, the minimization of wave reflection at boundaries is important for achieving accurate results and limiting the disturbances on the air/water interface. The present study compares a set of existing wave outlet techniques which are commonly applied in free surface simulations using a viscous flow solver. These...

We assess the capability of fast wave models to deterministically predict nonlinear ocean surface waves from non-uniformly distributed data such as sampled from an optical ocean sensor. Linear and weakly nonlinear prediction algorithms are applied to long-crested irregular waves based on a set of laboratory experiments and corresponding numerical s...

This paper proposes an efficient potential and viscous flow decomposition method for wave-structure interaction simulation with single-phase potential flow wave models and two-phase Computational Fluid Dynamics (CFD) solvers. The potential part - represents the incident waves - is solved with spectral wave models; the viscous part - represents the...

Ce papier présente les derniers développements concernant le couplage de la méthode SWENSE ( Spectral Waves Navier-Stokes Equations ) et d'une méthode de résolution des équations RANS ( Reynolds Averaged Navier-Stokes ) avec capture d'interface de type Level Set . Ce couplage permet de combiner les avantages des deux méthodes, c'est-à-dire avoir un...

Accurate real-time simulations and forecasting of phase-revolved ocean surface waves require nonlinear effects, both geometrical and kinematic, to be accurately represented. For this purpose, wave models based on a Lagrangian steepness expansion have proved particularly efficient, as compared to those based on Eulerian expansions, as they feature h...

Numerical wave tanks rely on specific models to generate realistic wave condition, propagate accurately the waves in the domain, and absorb the reflected waves at the boundaries. In this paper, three wave modeling methods for two-phase CFD solvers are compared, including the Internal Wave Generator method, the Relaxation Zone method, and the Spectr...

L’éolien offshore est l’énergie marine la plus avancée et utilisée dans le monde. Afin d’accroître l’énergie extraite du vent, les dimensions des éoliennes deviennent plus importantes et les parcs éoliens sont installés de plus en plus loin des côtes, où les mers sont agitées et les vents forts. De fait, les opérations marines sont plus complexes e...

This paper presents a new mesh strategy for unsteady potential flow based solvers. It is based on the coupling between a panel cutting method used for the body mesh and an advance front method to generate the free surface mesh. The goal is to deal with complex geometries for time-domain simulations for marine operations. Firstly, the new mesh gener...

This study focuses on the impact of the aerodynamic model on the dynamic response of a floating vertical axis wind turbine (VAWT). It compares a state‐of‐the‐art quasi‐steady double multiple streamtube (DMS) solver, a prescribed vortex wake (PVW), and a free vortex wake (FVW) solver. The aerodynamic loads acting on a bottom‐fixed VAWT and computed...

The efforts to couple viscous and inviscid flows in naval and offshore engineering have been studied from the early 90s. The researches showed a possibility of reducing the computational domain but the most of researches are concluded to the increase of total computation cost and complexity of methodology [2, 3]. Because two-way coupling needs to s...

Over the last decade, several coupled simulation tools have been developed in order to design and optimize floating wind turbines (FWTs). In most of these tools, the aerodynamic modeling is based on quasi‐steady aerodynamic models such as the blade element momentum (BEM). It may not be accurate enough for FWTs as the motion of the platform induces...

CN-Stream is a library for the computation of nonlinear regular ocean waves. The library is developed in order to be easily integrated with wave generation models in CFD solvers. It is based on the stream function theory and provides significant improvements regarding the applicability of the method for waves close to breaking (in deep or shallow w...

The performance of a phase-resolved algorithm is assessed for the prediction of nonlinear ocean wave fields based on remote optical measurements of free surface elevations in space and time. The accuracy of the wave forecast is evaluated here for the simple case of a unidirectional wave field, by ensemble averaging a large number of synthetic data...

Global navigation satellite systems (GNSSs) and modern motion-sensor packages allow the measurement of ocean surface waves with low-cost drifters. Drifting along or across current gradients provides unique measurements of wave–current interactions. In this study, we investigate the response of several combinations of GNSS receiver, motion-sensor pa...

Floating Offshore Wind Turbines (FOWTs) can have a very unsteady aerodynamic behaviour at sea. However state-of-the-art aerodynamic models used for FOWTs usually assume a steady and inviscid flow around the rotor. The induction factor is then computed using Froude-Rankine Actuator Disk theory, also called momentum theory. For a Horizontal Axis Wind...

This paper presents the recent developments of the Spectral Wave Explicit Navier-Stokes Equations (SWENSE) method to extend its range of application to two-phase VOF solvers. The SWENSE method solves the wave-structure interaction problem by coupling potential theory and the Navier-Stokes (NS) equations. It evaluates the incident wave solution by w...

We investigate a nonlinear phase-resolved reconstruction algorithm and models for the deterministic prediction of ocean waves based on a large number of spatio-temporal optical measurements of surface elevations. We consider a single sensor (e.g., LIDAR, stereo-video, etc.) mounted on a fixed offshore structure and remotely measuring fields of free...

The capability of wave generation and absorption in a viscous flow solver becomes important for achieving realistic simulations in naval and offshore fields. This study presents an efficient generation of nonlinear wave fields in the viscous flow solver by using a nonlinear potential solver called higher-order spectral method (HOS). The advantages...

Global Navigation Satellite Systems (GNSS) and modern motion-sensor packages allow the measurement of ocean surface waves with low-cost drifters. Drifting along or across current gradients provides unique measurements of wave-current interactions. In this study, we investigate the response of several combinations of GNSS receiver, motion-sensor pac...

Wave-to-Wire numerical models being developed for the study of wave energy converters usually make use of linear potential flow theory [[1], [2], [3], [4], [5]] to describe wave-structure interaction. This theory is highly efficient from a computational perspective. However, it relies on assumptions of small wave steepness and small amplitude of mo...

This paper presents validation tests for a new numerical tool for the numerical simulation of marine operations. It involves multibody dynamics modeling, wave-structure interactions with large amplitude body motion and cable’s dynamic modeling. Hydrodynamic loads are computed using the WS_CN weakly nonlinear potential flow solver, based on the weak...

Spectral Wave Explicit Navier-Stokes Equations (SWENSE) method couples potential wave models and CFD solvers to enhance the efficiency of numerical simulations for wave-structure interactions. Good acceleration is achieved with the original method proposed for single-phase CFD solvers. In this paper, we attempt to extend the method to two-phase and...

The use of RANS based CFD methods has increased recently in naval and offshore engineering to overcome the limits of classical potential flow methods. The problem of seakeeping with forward speed causes many difficulties even for the linear potential flow methodolgy based on boundary integral equation (BIE) and enormous efforts are demanded when th...

Wave generation solvers using Higher Order Spectral Method (HOS) have been validated and developed over the years. HOS solves nonlinear wave propagation in open sea (HOS-Ocean) and in numerical wave tank (HOS-NWT) with low computation time comparing with other nonlinear solvers. HOS solvers are released as open-source codes under the terms of GNU G...

The simulation of marine operations, in particular of lifting or lowering operations, requires the modeling of the whole system (ship, cable and payload) along with a theory of multibody dynamics, an appropriate hydrodynamic theory and cable’s modeling. This paper presents a new approach to achieve this type of simulation based on a coupling betwee...

A fully non-linear High-Order Spectral (HOS) model, already developed for a flat bottom in the LHEEA Lab of Ecole Centrale de Nantes, has been expanded to a variable bottom. This paper deals with the validation of the HOS model for wave propagation over a 3D variable bottom. A comparison to the finite difference scheme OceanWave3D developed at the...

Depending on the environmental conditions, floating Horizontal Axis Wind Turbines (FHAWTs) may have a very unsteady behaviour. The wind inflow is unsteady and fluctuating in space and time. The floating platform has six Degrees of Freedom (DoFs) of movement. The aerodynamics of the rotor is subjected to many unsteady phenomena: dynamic inflow, stal...

Dealing with freely-floating bodies in the framework of non-linear potential flow theory may require solving Laplace's equation for the time derivative of the velocity potential. At present, there are two competing formulations for the body boundary condition. The first one was derived by Cointe [1] in 2D. It was later extended to 3D by van Daalen...

The scattering of nonlinear and non-breaking surface gravity waves propagating over a three-dimensional varying bathymetry is considered in this paper. In a recent study (Gouin et al., 2016) two numerical schemes for propagating waves over a variable bottom in an existing High-Order Spectral (HOS) model have been introduced. Both the computational...

Presentation of M. Cathelain’s development during her PhD thesis at ECN/LHEEA. The code coupling takes advantage of P. Sullivan (UCAR) LES atmospheric model Thesis defended 01/2017

Afin d’exploiter au mieux le potentiel énergétique marin, des concepts d’éoliennes flottantes voient le jour. Les éoliennes à axe vertical (Vertical Axis Wind Turbine : VAWT) sont au centre de plusieurs travaux de recherche pour des applications flottantes. L’aérodynamique de ces éoliennes est très instationnaire. En effet, chaque pale passe à chaq...

In the present paper two numerical schemes for propagating waves over a vari- able bathymetry in an existing High-Order Spectral (HOS) model are intro- duced. The first scheme was first developed by Liu and Yue (1998), and the second one is an improved scheme which consider two independent orders of non-linearity: one for the bottom and one for the...

HOS-ocean is an efficient High-Order Spectral code developed to solve the deterministic propagation of nonlinear wavefields in open ocean. HOS-oceanis released as open-source, developed and distributed under the terms of GNU General Public License (GPLv3). Along with the source code, a documentation under wiki format is available which makes easy t...

The increase in ship dimensions shifts their structural natural frequencies towards common wave frequencies, inducing more interactions between the classic seakeeping response and the structural response. CFD solvers are developed to tackle such problem. Here a new numerical approach with a viscous flow solver is proposed and validated against the...

Liu and Yue [1] developed a numerical scheme for propagating waves over a variable bathymetry with a High-Order Spectral (HOS) Method. The development of this nonlinear model is detailed and validated on three different test cases. They intend to demonstrate that such a model may be applied to small bottom variations as considered in [1] but also o...

In continuation of [1], this paper presents the progress made towards the development of a new modeling tool based on the Weak-Scatterer approaches. Recent developments are the coupling of the fluid and body solver in order to predict the free motion response of the body. Pressure field over the wetted area is obtained by solving an additional boun...

Highlights • Presentation of an HOS scheme for modelling non-linear water waves over a variable bathymetry. • Validation of the method for a small variation of the bottom with Bragg reflection. • Application of the HOS model to wave propagation over a bathymetry with high variation of the bottom: submerged bar.

The state of the art tools to assess the efficiency of the wave energy converters comprise the boundary element method (BEM) codes which are based on the potential linear approach whereas computational fluid dynamics (CFD) is still considered to be relatively computationally expensive. An attempt to enlarge the scope of the state of the art computa...

We present a comparison between two distinct numerical codes dedicated to the study of wave energy converters. Both are developed by the authors, using a boundary element method with linear triangular elements. One model applies fully nonlinear boundary conditions in a numerical wavetank environnment (and thus referred later as NWT), whereas the se...

http://www.iwwwfb.org/Abstracts/iwwwfb29/iwwwfb29_13.pdf

A weakly nonlinear potential flow model based on the boundary element method is presented. The hydrodynamic force is integrated on the exact body position. In the Weak-Scatterer approximation, the potential flow and the free surface elevation are separated into an incident component, computed by an external solver, and a perturbation component. No...

Cet article présente une nouvelle variante du couplage de la méthode SWENSE (Spectral Wave Explicit Navier-Stokes Equations) avec un algorithme de capture d'interface de type Level Set monophasique dans un code RANSE (Reynolds Averaged Navier-Stokes Equations). Le but final est de simuler numériquement l'interaction houle-structure en présence de d...

This paper deals with the development of an enhanced model for solving wave-wave and wave-structure interaction problems. We describe the appli-cation of a nonlinear splitting method originally suggested by Di Mascio et al. [1], to the high-order finite difference model developed by Bingham et al. [2] and extended by EngsigKarup et al. [3, 4]. The...

The purpose of this paper is to present combination of the SWENSE (Spectral Wave Explicit Navier-Stokes Equations) method –an original method to treat fully nonlinear wavebody interactions- and a free surface RANSE (Reynolds Averaged Navier-Stokes Equations) solver using a single-phase Level Set method to capture the interface. The idea is to be ab...

A new hybrid-spectral solution strategy is proposed for the simulation of the fully nonlinear free surface equations based on potential flow theory. A Fourier collocation method is adopted horisontally for the discretization of the free surface equations. This is combined with a modal Chebyshev Tau method in the vertical for the discretization of t...

This paper compares numerical and experimental results in the study of the resonance phenomenon which appears between two side-by-side fixed barges for different sea-states. Simulations were performed using SWENSE (Spectral Wave Explicit Navier-Stokes Equations) approach and results are compared with experimental data on two fixed barges with diffe...

A model of the Dutch Tri-floater semi-submersible platform equipped with the NREL 5MW wind turbine has been tested in the hydrodynamic and ocean engineering tank of École Centrale Nantes under wind and wave loads. This paper aims at comparing the results obtained with numerical simulations with these experimental results. The numerical model is bas...

A series of wave basin experiments is reported that investigates the flexural response of one or two floating thin elastic discs to monochromatic waves. The work is motivated by numerical model validation. Innovative techniques are used to ensure the experimental configuration is consistent with the model. This demands linear motions, time-harmonic...

Validation of a linear numerical model of wave interactions with floating compliant discs is sought using data obtained from the wave basin experiments reported in Part 1 (Montiel et al. J. Fluid Mech., vol. 723, 2013, pp. 604–628). Comparisons are made for both single-disc tests and the two-disc tests in which wave interactions between discs are o...

A coupled dynamic analysis of a floating wind turbine system has been performed to investigate effect of wave direction relative to wind on the system. Hydrodynamic loads are calculated by linear frequency domain approach and aerodynamic effect is taken into account by increasing hydrodynamic damping and restoring matrices with aerodynamic damping...

This paper describes the improvement of an existing wind generation system, associated with a wave basin, for physical model testing of a floating wind turbine. Methodology set up for the study of a floating wind turbine subjected to wind and swell will also be presented. This paper complements previous papers Courbois et al. (2011) where first ste...

This paper describes an implementation of the fast multipole algorithm using the free-surface Green’s function for ocean water waves. Its aim is to investigate different parameters of the fast multipole algorithm in order to efficiently carry out computations on sets of unknowns that are very inhomogeneously distributed in space. Some limits of the...

Ce papier présente le couplage de la méthode SWENSE (Spectral Wave Explicit Navier-Stokes Equations) avec un algorithme de capture d’interface de type Level Set monofluide dans un code RANSE (Reynolds Averaged Navier-Stokes Equations). L’objectif est de pouvoir simuler l’interaction houle-structure en présence de déformations importantes de l’inter...

This paper presents the recent development on the nonlinear directional wave generation process in a 3D Numerical Wave Tank (NWT). The NWT is based on a nonlinear model using the High-Order Spectral (HOS) method, which exhibits high level of accuracy as well as efficiency properties provided by a Fast Fourier Transform (FFT) solution. The wavemaker...

This paper presents a comparison in terms of accuracy and efficiency between two fully nonlinear potential flow solvers for the solution of gravity wave propagation. One model is based on the high-order spectral (HOS) method, whereas the second model is the high-order finite difference model OceanWave3D. Although both models solve the nonlinear pot...

This paper presents an aero-hydro-elastic model of a semi-submersible floating wind turbine. A specific attention is drawn to hydrodynamic modelling options and its effect on the dynamic response of the platform. The NREL 5MW reference wind turbine mounted on the historical concept of semi-submersible platform Dutch Tri-floater is considered. A spe...

Some recent marine incidents have shown that damaged Ro-Ro ferries can be extremely vulnerable to loss of stability. After an abrupt ingress of water caused by a maritime accident, flooding of the spaces below the car deck may endanger the ship and eventually lead to its sinking within a short period of time. The flooding stages depend upon many fa...

This paper presents a parametric study on arrays of wave energy converters (WECs). Its goal is to assess the influence of interactions between bodies on the overall yearly energy production of the array. Generic WECs (heaving cylinder and surging barge) are considered. Nine to twenty-five WECs are installed along regular square and triangular grids...

A generic Oscillating Surge Wave Energy Converter (OSWC) has been tested numerically against the impact of the viscous forces. The study makes use of both the linear potential theory as well as the computational fluid dynamics (CFD). A state-of-the-Art time domain wave-to-wire numerical model of the wave energy converter (WEC) is developed. Viscous...

This article recalls the recent developments of the SWENSE (Spectral Wave Explicit Navier-Stokes Equations) method and presents a first validation case for a multidirectional irregular wave field. The SWENSE approach is aimed at simulating fully nonlinear wave-body interactions including viscous effects. It combines the benefits of a potential flow...

This paper presents new developments on the multipole expansion of the infinite water depth free-surface Green's function, in the scope of wave farm simulation. The multipole expansion of the Green's function and its derivatives have been extended to be used in a 3D fast multipole algorithm. Previous restrictions over the use of the multipole expan...

This work presents a numerical method able to take into account wind wave coupling and energy dissipation related to wave breaking in a deterministic sea state model. We carry out such simulations with an HOS model developed at LMF-ECN since 2002 and based on the work of West et al. (1987) and Dommermuth & Yue(1987). This model performs direct nume...