Simulating tidal turbines with mesh optimisation and RANS turbulence models

A versatile numerical model for the simulation of flow past horizontal axis tidal turbines has been developed. Currently most large-scale marine models employed to study marine energy use the shallow water equations and therefore can fail to account for important turbulent physics. The model presented here is based on actuator disc momentum (ADM) theory, uses a RANS model to account for turbulence and utilises mesh optimisation in order to address the multi-scale nature of the problem. Furthermore, a series of laboratory experiments were carried out in the hydrodynamics laboratory of the Civil and Environmental Engineering Department at Imperial College London which were used to help validate the numerical model. Turbulence correction terms have been used to capture the short circuiting of the turbulence cascade due to the presence of the disc and thereby improve the match with the experimental data. This model has been developed with the aim that it will be seamlessly combined with larger numerical models simulating tidal flows in realistic domains, e.g. the Inner Sound of the Pentland Firth. This is where the adaptive meshing capability is a major advantage as it enables the mesh to be refined only in the locations required, thus making optimal use of limited computational resources.