Entrainment and power estimation in large finite-length wind plants*

As the calls for increased levels of wind energy production grow, the size of future wind farms is expected to also increase. In large wind plants, unlike isolated turbines or small wind farms, the physical mechanism that is primarily responsible for transporting the energy of the wind to the turbines' location is turbulence. A detailed analysis of the energy extraction mechanisms from large wind farms is of critical significance in order to avoid large power losses and fatigue loads - which are already significant in small and medium size farms - as these grow in size. In the present work, we use the well-established high-order numerical framework WInc3D to perform high-fidelity simulations of the flow in large finite-length wind farms of different sizes and layouts in an attempt to gain insight into entrainment - the transport of fluid across an interface by turbulence - and its relationship with power density. To this end, we look into the relative importance of different mechanisms of energy transport in wind farms according to the position of a turbine within the farm and investigate the way in which different farm designs affect the transfer of energy to the turbines by directly calculating the rates and coefficients of turbulent entrainment.