Numerical simulation of an array of heaving floating point absorber wave energy converters using OpenFOAM

In this paper we use the CFD toolbox OpenFOAM to perform numerical simulations of multiple floating point absorber Wave Energy Converters (WECs) in a numerical wave basin. The two-phase Navier-Stokes fluid solver is coupled with a motion solver to simulate the wave-induced rigid body heave motion. The key of this paper is to extend numerical simulations of a single WEC unit to multiple WECs and to tackle the issues of modelling individual floating objects close to each other in an array lay-out. The developed numerical model is validated with laboratory experiments for free decay tests and for a regular wave train using two or five WECs in the array. For all the simulations presented, a good agreement is found between the numerical and experimental results for the WECs’ heave motions, the surge forces on the WECs and the perturbed wave field. As a result, our coupled CFD–motion solver proofs to be a suitable and accurate toolbox for the study of wave-structure interaction problems of multiple floating bodies in an array configuration

Towards the numerical simulation of 5 Floating Point Absorber Wave Energy Converters installed in a line array using OpenFOAM

In this paper we use the CFD toolbox OpenFOAM to perform numerical simulations of multiple floating point absorber Wave Energy Converters (WECs) in a numerical wave basin. The two-phase Navier-Stokes fluid solver is coupled with a motion solver to simulate the wave-induced rigid body heave motion. The purpose of this paper is twofold. The first objective is to extend numerical simulations of a single WEC unit to multiple WECs and to tackle the issues of modelling individual floating objects close to each other in an array layout. The second objective aims to include all the physical processes (e.g. friction forces) observed during experimental model tests in the numerical simulations. The achievements are verified by validating the numerical model with laboratory experiments for free decay and regular wave tests using a line array of two and five WECs. For all the simulations presented, a good agreement is found between the numerical and experimental results for the WECs’ heave motions, the surge forces on the WECs and the perturbed wave field. As a result, our coupled CFD–motion solver proves to be a suitable and accurate toolbox for the study of wave-structure interaction problems of WEC arrays.location: Cork, Irelandstatus: publishe

Performance of a buoyancy-modified k-ω and k-ω SST turbulence model for simulating wave breaking under regular waves using OpenFOAM ®

© 2018 Elsevier B.V. In this work, the performance of a buoyancy-modified turbulence model is shown for simulating wave breaking in a numerical wave flume. Reynolds-Averaged Navier-Stokes (RANS) modelling is performed by applying both a k-ω and a k-ω SST turbulence model using the Computational Fluid Dynamics (CFD) toolbox OpenFOAM. In previous work of the authors (Devolder et al., 2017), the observed significant decrease in wave height over the length of the numerical wave flume based on RANS turbulence modelling for the case of propagating waves has been avoided by developing a buoyancy-modified k-ω SST model in which (i) the density is explicitly included in the turbulence transport equations and (ii) a buoyancy term is added to the turbulent kinetic energy (TKE) equation. In this paper, two buoyancy-modified turbulence models are applied for the case of wave breaking simulations: k-ω and k-ω SST. Numerical results of wave breaking under regular waves are validated with experimental data measured in a wave flume by Ting and Kirby (1994). The numerical results show a good agreement with the experimental measurements for the surface elevations, undertow profiles of the horizontal velocity and turbulent kinetic energy profiles. Moreover, the underlying motivations for the concept of a buoyancy-modified turbulence model are demonstrated by the numerical results and confirmed by the experimental observations. Firstly, the buoyancy term forces the solution of the flow field near the free water surface to a laminar solution in case of wave propagation. Secondly in the surf zone where waves break, the buoyancy term goes to zero and a fully turbulent solution of the flow field is calculated. Finally and most importantly, the buoyancy-modified turbulence models significantly reduce the common overestimation of TKE in the flow field.status: publishe

Numerical simulation of a single floating point absorber wave energy converter using OpenFOAM

status: publishe

Accelerated numerical simulations of a heaving floating body by coupling a motion solver with a two-phase fluid solver

© 2018 Elsevier Ltd This paper presents a study on the coupling between a fluid solver and a motion solver to perform fluid–structure interaction (FSI) simulations of floating bodies such as point absorber wave energy converters heaving under wave loading. The two-phase fluid solver with dynamic mesh handling, interDyMFoam, is a part of the Computational Fluid Dynamics (CFD) toolbox OpenFOAM. The incompressible Navier–Stokes (NS) equations are solved together with a conservation equation for the Volume of Fluid (VoF). The motion solver is computing the kinematic body motion induced by the fluid flow. A coupling algorithm is needed between the fluid solver and the motion solver to obtain a converged solution between the hydrodynamic flow field around and the kinematic motion of the body during each time step in the transient simulation. For body geometries with a significant added mass effect, simple coupling algorithms show slow convergence or even instabilities. In this paper, we identify the mechanism for the numerical instability and we derive an accelerated coupling algorithm (based on a Jacobian) to enhance the convergence speed between the fluid and motion solver. Secondly, we illustrate the coupling algorithm by presenting a free decay test of a heaving wave energy converter. Thirdly and most challenging, a water impact test of a free falling wedge with a significant added mass effect is successfully simulated. For both test cases, the numerical results obtained by using the accelerated coupling algorithm are in a very good agreement with the experimental measurements.keywords: Modelling and Simulation,Computational Theory and Mathematics,Computational Mathematics location: Ghent Univ, Ghent, BELGIUMstatus: publishe

Survivability simulation of a wave energy converter in a numerical wave tank

location: Shanghai, Chinastatus: publishe

Validation of a roll decay test of an offshore installation vessel using openfoam

In this work, the offshore heavy lift DP2 jack-up vessel Innovation from the DEME group is studied using the Computational Fluid Dynamics (CFD) toolbox OpenFOAM. The two-phase Navier-Stokes fluid solver is coupled with a motion solver using a partitioned fluid-structure interaction algorithm. Firstly, two dimensional numerical simulations of a cross-section of the hull are performed using two different mesh motion techniques: a mesh morphing method and an overset mesh method. Subsequently, the addition of a bilge keel pair on the hull is studied numerically by performing a two dimensional roll decay simulation. Finally, a three dimensional simulation is performed for a roll decay test and validated by using experimental data measured in the MARIN seakeeping and manoeuvring basin. As a first result, the coupled CFD–motion solver proofs to be a promising toolbox for the study of fluid-structure interaction problems of realistic marine structures such as an offshore installation vessel