Estimation of numerical uncertainty in computational fluid dynamics simulations of a passively controlled wave energy converter
Journal article, 2018

The wave loads and the resulting motions of floating wave energy converters are traditionally computed using linear radiation–diffraction methods. Yet for certain cases such as survival conditions, phase control and wave energy conver- ters operating in the resonance region, more complete mathematical models such as computational fluid dynamics are preferred and over the last 5 years, computational fluid dynamics has become more frequently used in the wave energy field. However, rigorous estimation of numerical errors, convergence rates and uncertainties associated with computa- tional fluid dynamics simulations have largely been overlooked in the wave energy sector. In this article, we apply formal verification and validation techniques to computational fluid dynamics simulations of a passively controlled point absor- ber. The phase control causes the motion response to be highly nonlinear even for almost linear incident waves. First, we show that the computational fluid dynamics simulations have acceptable agreement to experimental data. We then present a verification and validation study focusing on the solution verification covering spatial and temporal discretiza- tion, iterative and domain modelling errors. It is shown that the dominating source of errors is, as expected, the spatial discretization, but temporal and iterative errors cannot be neglected. Using hexahedral cells with low aspect ratio and 30 cells per wave height, we obtain results with less than 5% uncertainty in motion response (except for surge) and restraining forces for the buoy without phase control. The amplified nonlinear response due to phase control caused a large increase in numerical uncertainty, illustrating the difficulty to obtain reliable solutions for highly nonlinear responses, and that much denser meshes are required for such cases.

verification and validation

passive control

Wave energy converter

numerical uncertainty

computational fluid dynamics modelling

Author

Weizhi Wang

Chalmers, Mechanics and Maritime Sciences

Minghao Wu

Chalmers, Mechanics and Maritime Sciences

Johannes Palm

Chalmers, Mechanics and Maritime Sciences, Marine Technology

Claes Eskilsson

Aalborg University

Chalmers, Mechanics and Maritime Sciences

Proceedings of the Institution of Mechanical Engineers Part M: Journal of Engineering for the Maritime Environment

1475-0902 (ISSN)

Vol. 232 1 71-84

Subject Categories

Other Mechanical Engineering

Applied Mechanics

Vehicle Engineering

Driving Forces

Sustainable development

Areas of Advance

Energy

Infrastructure

C3SE (Chalmers Centre for Computational Science and Engineering)

DOI

10.1177/1475090217726884

More information

Latest update

4/4/2018 2