Impact of the wind field at the complex terrain site Perdigão on the surface pressure fluctuations of a wind turbine

Abstract

Abstract. The influence of turbulent inflow, as it occurs in complex terrain, on the unsteady surface pressure distributions on a wind turbine is investigated numerically. A method is presented that enables an accurate reproduction of the inflow to the turbine in the complex terrain in Perdigao, Portugal. For this purpose, a precursor simulation with the steady-state atmospheric computational fluid dynamics (CFD) code E-Wind and a high-resolution Delayed Detached Eddy Simulation (DDES) with FLOWer is performed. The conservation of the flow field is validated by a comparison with measurements from the 2017 field campaign in Perdigao. Then, the resolved fluid-structure coupled generic wind turbine I82 is included in the FLOWer simulation to investigate the impact of the complex terrain inflow on the surface pressure fluctuations on tower and blades. A comparison with simulations of the same turbine in flat terrain with simpler inflows shows that the turbine in complex terrain has a significantly different vortex shedding at the tower, which dominates the periodic pressure fluctuations at the tower sides and back. However, the dominant source of periodic pressure fluctuations on the upper part of the tower, the blade-tower interaction, is hardly altered by the terrain flow. The pressure fluctuations on the blade have a rather broadband characteristic, caused by the interaction of the leading edge with the inflow turbulence. In general, it is shown that a sophisticated DDES of the complex terrain plays a decisive role in the unsteady aerodynamics of the turbine, due to its specific flow characteristic.

Impact of turbulent inflow and orography on the low-frequency noise sources of a wind turbine

“…and flat+turb. cases, which is consistent with the surface pressure fluctuations found at the tower in Wenz et al [10].…”

“…The BTI occurring at the blade-passing frequency f B = 3f R = 0.84 Hz and its higher harmonics at f h,n = n • f B as well as the vortex shedding at the tower with f V S < 1.55 Hz are aerodynamically well captured with the described setup, as shown in Wenz et al [10]. The captured inflow turbulence depends on the size of the turbulence eddies Λ resolved in the CFD.…”

“…For the simulation with complex terrain, the inflow conditions for FLOWer are taken from a precursor simulation performed by Enercon with the steady-state atmospheric CFD solver E-Wind [9], which was calibrated with met mast data from the site. The tools, their interfaces and the numerical setups are described in more detail in Wenz et al [10].…”

“…The computational setup is taken from Wenz et al [10]. The CFD model of the I82 turbine for the simulation with FLOWer consists of 17 independent meshes, which are embedded in the Perdigão terrain mesh or a flat background mesh, respectively, and are connected with the Chimera technique (see Figure 1).…”

“…The simulations evaluated in this study have already been aerodynamically investigated in Wenz et al [10], with a focus on surface pressure fluctuations. The main simulation contains the fluid-structure coupled I82 in the complex terrain in Perdigão with a situation-specific turbulent wind field (case terrain).…”