Large eddy simulation of wind farm flows : improved Actuator Disk model and investigations of wake phenomena
(2018)
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- Abstract
- Wind energy is one of the fastest growing energy sources, leading to important research efforts targeting costs reduction, improved reliability and grid integration of the wind farms. The development of wind farm simulation tools is thus particularly important, as numerical approaches offer a convenient framework for elaborating control strategies aimed at responding to a grid demand or at mitigating the negative effects related to the rotor wakes. Indeed, in a wind farm configuration, the wake phenomena are responsible for a decrease in power production and a shortening of the lifetime of the turbines, and have a direct impact on the Levelized Cost of Energy. Numerical tools thus have to accurately capture the physics of the rotors and wakes and the unsteady nature of a wind farm production, at a reasonable computational cost. This work aims at achieving this by using Large Eddy Simulation on coarse meshes, combined with an Actuator Disk (AD) method for the wind turbine model. This last approach implies an averaged effect of the blade forces on the surface swept by the rotor. A major effort is made in order to have the most accurate response of the AD, in spite of the underlying approximation and of its coarse resolution: we here consider a rotating disk, for which the loads are estimated from local disk velocities, and a new methodology is implemented to enable the use of a tip-loss correction in wind farm flows. This correction aims at improving the AD behavior by accounting for the differences between a disk method and a discrete blade type approach. This implemented AD is first verified in terms of aerodynamics, loads and wake statistics for a single wind turbine, and results are compared to a higher fidelity approach at a finer resolution, here a Vortex Particle-Mesh method coupled to immersed lifting lines. In a second part, the AD is equipped with realistic control schemes and used in wind farm simulations. These aim at several purposes: (i) to evaluate the performances of the tool in large wind farms in terms of computational costs, (ii) to verify the power production against measurements for an actual wind farm, and (iii) to investigate the wake statistics and the rotor responses in several scenarios.
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Citations
Moens, M. (2018). Large eddy simulation of wind farm flows : improved Actuator Disk model and investigations of wake phenomena. https://hdl.handle.net/2078.5/171063