CFD simulation of novel wave energy, tidal energy and floating wind energy concepts to assess hydrostatic stability, motion response in regular and irregular waves, power absorption, wave, current and mooring loads and the connecting forces between coupled bodies in waves, implicitly taking into account fluid viscosity derived forces.
Extreme wave survival loads on static and floating marine energy concept using solitary focused waves or short duration large irregular waves are also feasible. The unique combination of advanced free surface tracking and flexibility to model several connected moving objects without the need to re-mesh enables complex body motions in response to wave and current forces to be accounted for, including the detection of power dissipating parametric roll and pitch motions which can result from dynamic changes in hydrostatic stiffness.
Performance Tests in regular and irregular waves taking into account the occurrence of non-linear free surface effects resulting from local wave refraction and dissipation of energy due to wave breaking and vorticies as seen here in a CFD simulation of the Bristol Cylinder wave energy converter, are conducted in a numerical wave tank without needing to build, instrument and test in a conventional wave tank. Prime mover geometry changes and power take off coefficients, can be changed quickly and reliably. Mooring configurations are represented by combining elastic ropes with the required any stiffness and damping coefficients.
Motion decay tests in any of the six degrees of freedom and natural oscillation periods and drag coefficients can be extracted and used to supplement more extensive radiation diffraction based simulations in irregular seas, leading to a more realistic motion response and power absorption than would be achieved using potential flow based methods alone.
Moving Flap type wave energy converters operating in deep and shallow water are particular amenable to free surface simulation using our CFD modelling methods which can capture the non-linear effects due to overtopping and drag forces. These effects cannot be accurately accounted for using any other method other wave tank or full scale testing. The PTO can be added in terms of rotational stiffness and damping coefficients and the power absorbed calculated. Floating platform type wave energy converters where one or more flaps react against the platform can also be handled. Incident waves may be regular, irregular or extreme survival waves.
Tidal Turbine simulations using our moving bodies modelling capability makes the performance and thrust loads on rotor and stators including blade tower/stanchion interactions possible without the usual complexity and inherent instability of moving meshes. The performance of Array layouts in shallower water taking account of the momentum deficit created by each tidal stream turbine, the local bathymetry and tidal forcing boundary conditions, allowing the project developer to test different layouts in terms of power output and environmental impact.
Deployment Scenarios where for example an ocean energy converter is towed to site in waves and current, ballasted into its upright position and mooring lines attached, can be simulated and problems which may have been overlooked uncovered, potentially reducing boat hire costs and risk to personnel and the project. Estimation of drag coefficients during wet tow operation can be used to specify boat sizes and speeds and extreme ocean current loads on electrical transmission cables on the seabed can be simply calculated.
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