Session: 09-05-01 Wave Energy: Hydrodynamics

Submission Number: 157670

High-Fidelity Modelling of a Simplified Hinged-Raft WEC: A CFD Approach 

The use of high-fidelity Computational Fluid Dynamics (CFD) has become increasingly popular in the wave energy sector for investigating the dynamic behaviour of devices and to inform design choices. Compared to low-fidelity models, CFD is capable of capturing highly non-linear phenomena such as viscous effects and turbulence. Also, compared to a full tank testing programme, CFD can simulate different wave conditions and geometries relatively quickly and cheaply. However, little guidance exists in the current literature for the setup of floating hinged-raft Wave Energy Converters (WECs) such as the Mocean Energy device using CFD. There are certain challenges that need to be overcome to simulate such a complicated system. One of the main issues is the numerical instability of solving two bodies in close proximity to each other.

This paper aims to outline the basic workflow and provide a robust methodology for the CFD simulation setup of a simplified two-body hinged-raft geometry using the OverInterDyMFoam solver in OpenFOAM. The modelling practice for handling the gap between the two hulls is also addressed. The floating hinged-raft is simulated in four different Overset (OS) mesh configurations, with results compared between the different setups. The same simulations are carried out for various reduced gap sizes, with the OS mesh configuration that manages the smallest gap being identified. The impact of different gap sizes on the responses of the device is also explored. Lastly, the hinged raft with a suitable setup is simulated under various wave periods, and the flex motion response is verified against Frequency-Domain (FD) simulation results from the potential flow solver WAMIT.

As a result of the above, this study helps to inform the CFD model setup of hinged-raft devices with complex geometries. This, in turn, provides another step forward towards CFD survivability studies of this type of device.

Presenting Author: Nian Liu University of Edinburgh, Mocean Energy

Presenting Author Biography: Nian is currently an EngD student on the IDCORE programme which collaborates between partner universities: the University of Edinburgh, the University of Strathclyde and the University of Exeter. Nian’s project mainly works with Mocean Energy, a wave energy company based in Edinburgh, focusing on device geometry optimisation and Computational Fluid Dynamics (CFD) modelling.