A damping method for RANS wind farm flow simulations subjected to shallow atmospheric boundary layers

Energy losses due to wind turbine interaction are sensitive to atmospheric conditions, and it is not trivial to take this into account in Reynolds-averaged Navier-Stokes simulations. For low atmospheric boundary layer (ABL) heights relative to the turbine size, numerical standing waves can appear that reduce the numerical stability and solution quality. In the present work, a damping method based on an artificially high eddy viscosity regime above the atmospheric boundary layer is proposed. It is shown that the damping method can remove the spurious waves and improve numerical stability. The damping method has an operational envelope limited to ABLs at least twice as tall as the turbine; for lower ABLs relative to the turbine height, too much damping is required, which consequently changes the flow upwind, through, and above the wind farm.