Special Issue "Nonlinear Numerical Modelling of Wave Energy Converters"

A special issue of Journal of Marine Science and Engineering (ISSN 2077-1312).

Deadline for manuscript submissions: 30 November 2019

Special Issue Editor

Guest Editor
Assoc. Prof. Claes Eskilsson

Department of Civil Engineering, Aalborg University, Thomas Manns Vej 23, DK-9220 Aalborg Ø, Denmark
Website | E-Mail
Interests: numerical modelling, wave propagation, wave-body interaction, wave energy, mooring, high-order finite element models, computational fluid dynamics

Special Issue Information

Dear Colleagues,

The performance of wave energy converters is traditionally estimated using numerical models based on linear radiation/diffraction theory. However, over the last couple of years, we have seen an increase in the use of high-fidelity nonlinear hydrodynamic modelling for wave energy converters. The nonlinear approach is, of course, used in order to overcome the shortcomings of the small-wave-amplitude/small-motion assumptions underlying the linear approach. To include nonlinearity in the modelling is especially important for survival cases including steep and breaking waves and large amplitude motions, as well as the often highly nonlinear response in the resonance region of wave energy converter (WEC). Closely related to the resonance response is the application of phase control strategies that also increase the nonlinear response.

We would like to invite papers dealing with numerical method development especially of nonlinear models for wave energy. This includes, but is not limited to, computational fluid dynamics (CFD) as well as medium fidelity models such as fully and weakly nonlinear potential flow models and nonlinear Froude-Krylov approach. We are also interested in studies covering applications of nonlinear models in the wave energy field, and papers investigating nonlinear and viscous effects on WECs, for example parametric excitation. Additionally, experimental papers looking into nonlinear effects are highly encouraged.

Assoc. Prof. Claes Eskilsson
Guest Editor

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Journal of Marine Science and Engineering is an international peer-reviewed open access monthly journal published by MDPI.

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Keywords

  • wave energy
  • numerical methods
  • nonlinear hydrodynamics
  • phase control

Published Papers (2 papers)

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Research

Open AccessArticle
Evaluation of the Viscous Drag for a Domed Cylindrical Moored Wave Energy Converter
J. Mar. Sci. Eng. 2019, 7(4), 120; https://doi.org/10.3390/jmse7040120
Received: 14 March 2019 / Revised: 11 April 2019 / Accepted: 16 April 2019 / Published: 25 April 2019
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Abstract
Viscous drag, nonlinear in nature, is an important aspect of the fluid–structure interaction modelling and is usually not taken into account when the fluid is assumed to be inviscid. Potential flow solvers can competently compute radiation damping, which is related to the radiated [...] Read more.
Viscous drag, nonlinear in nature, is an important aspect of the fluid–structure interaction modelling and is usually not taken into account when the fluid is assumed to be inviscid. Potential flow solvers can competently compute radiation damping, which is related to the radiated wave field. However, the drag damping primarily related to the viscous effects is usually neglected in the radiation/diffraction problems solved by the boundary element method (BEM), also known as the boundary integral element method (BIEM). This drag force can have a significant impact in the case of structures extending much deeper below the free surface, or for those that are completely submerged. In this paper, the drag coefficient C d was quantified for the heave and surge response of a structure which consists of a moored horizontally oriented domed cylinder with two surface piercing square columns located at the top surface. The domed cylinder is the primary part and is submerged. The drag coefficient is estimated using the experimental measurements related to harmonic monochromatic wave–structure interaction. Finally, this estimated drag coefficient was used in the modified time domain model, which includes the nonlinear viscous correction term, and the resulting device response in heave and surge directions is presented for an irregular incoming wave field. The comparison of the numerical model and the experiments validates the estimated C d values obtained earlier. Prior to the time domain model, frequency-dependent parameters such as added mass, radiation damping, and excitation force were computed using three mainstream potential flow packages (that is, ANSYS AQWA, WAMIT, and NEMOH), and a comparison is presented. The effect of free surface on the drag coefficient is investigated through differences in C d values between heave and surge modes. Full article
(This article belongs to the Special Issue Nonlinear Numerical Modelling of Wave Energy Converters)
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Open AccessArticle
Assessment of Scale Effects, Viscous Forces and Induced Drag on a Point-Absorbing Wave Energy Converter by CFD Simulations
J. Mar. Sci. Eng. 2018, 6(4), 124; https://doi.org/10.3390/jmse6040124
Received: 26 September 2018 / Revised: 17 October 2018 / Accepted: 19 October 2018 / Published: 22 October 2018
Cited by 2 | PDF Full-text (7110 KB) | HTML Full-text | XML Full-text
Abstract
This paper analyses the nonlinear forces on a moored point-absorbing wave energy converter (WEC) in resonance at prototype scale (1:1) and at model scale (1:16). Three simulation types were used: Reynolds Averaged Navier–Stokes (RANS), Euler and the linear radiation-diffraction method (linear). Results show [...] Read more.
This paper analyses the nonlinear forces on a moored point-absorbing wave energy converter (WEC) in resonance at prototype scale (1:1) and at model scale (1:16). Three simulation types were used: Reynolds Averaged Navier–Stokes (RANS), Euler and the linear radiation-diffraction method (linear). Results show that when the wave steepness is doubled, the response reduction is: (i) 3% due to the nonlinear mooring response and the Froude–Krylov force; (ii) 1–4% due to viscous forces; and (iii) 18–19% due to induced drag and non-linear added mass and radiation forces. The effect of the induced drag is shown to be largely scale-independent. It is caused by local pressure variations due to vortex generation below the body, which reduce the total pressure force on the hull. Euler simulations are shown to be scale-independent and the scale effects of the WEC are limited by the purely viscous contribution (1–4%) for the two waves studied. We recommend that experimental model scale test campaigns of WECs should be accompanied by RANS simulations, and the analysis complemented by scale-independent Euler simulations to quantify the scale-dependent part of the nonlinear effects. Full article
(This article belongs to the Special Issue Nonlinear Numerical Modelling of Wave Energy Converters)
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