Assessment of Fluid-Structure Interaction for Marine Renewable Energy Device Using CFD


Title: Assessment of Fluid-Structure Interaction for Marine Renewable Energy Device Using CFD

Director of studies: Professor Deborah Greaves

Funded by: Self-funded (co-funded by Plymouth University and AW-Energy)

Researcher: Teng Tan Loh

Objectives

  • To construct a scale model simulation of the WaveRoller configuration in OpenFOAM to improve the representation of the non-linear wave-structure interaction with existing simulation approaches (eg. WaveDyn). 
  • To validate the numerical results with experimental data provided by AW-Energy. 
  • To predict the device wave load and impact under extreme wave conditions to assess the device survivability.
Background:

The WaveRoller device (Fig. 1) is an oscillating wave surge converter (OWSC) developed by AW-Energy. The device operates near-shore, at approximate distance of 0.3 km-2 km from the shore and at depths between 8 and 20 meters, where the panel is driven back and forth by surge forces induced by shoaling waves for generating electrical power. The WaveRoller is mounted on the seabed and consists of either a fully submerged or surface piercing buoyant panel depending on the tidal conditions. The PTO (power take-off) drive unit of the device is composed of a hydraulic piston pump that is attached to the panel, where high-pressure fluids are fed into a hydraulic motor that drives the electricity generator. The electricity output is then connected to the local power grid via a subsea cable. 

While innovative marine renewable energy device technologies are gaining popularity, the technicalities of operating them in hostile environment remain complex and challenging. In order to anticipate the performance and survivability of these devices, it is necessary to be able to model their behaviour accurately using the latest techniques available for solving fluid flow problems. In this research, open source CFD software, OpenFOAM is used to explore the effectiveness of using CFD methods to assess and improve AW-Energy’s modelling tools for the WaveRoller device. Unlike linear hydrodynamic methods which are mainly based on linear potential flow theory, OpenFOAM is not subject to the use of simplifying approximations when simulating the performance of wave energy devices. The CFD software utilises a finite volume technique for solving the discretised Reynolds Averaged Navier-Stokes equations. 

The main objective is to construct a scale model simulation of the WaveRoller configuration in OpenFOAM, in order to improve the representation of the non-linear wave-structure interaction with existing simulation approaches (eg. WaveDyn) and also for validating the experimental data provided by AW-Energy. The simulation model will then be used to predict the device wave load and impact under extreme wave conditions to assess the device survivability.

Fig. 1 Illustrative view of the WaveRoller devices as deployed along the shore line (aw-energy.com)