Detached Eddy Simulations of the local Atmospheric Flow Field within a Forested Wind Energy Test Site located in Complex Terrain

Letzgus, Patrick; Lutz, Thorsten; Krämer, Ewald

doi:10.1088/1742-6596/1037/7/072043

Cited by 16 publications

(13 citation statements)

References 12 publications

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“…Among others, the fifth-order weighted essentially nonoscillatory scheme WENO is available for spatial discretisation (Kowarsch et al, 2013) and several hybrid RANS/LES schemes have been implemented in FLOWer (Weihing et al, 2018). Furthermore, a body forces approach is included to superimpose atmospheric turbulence on the inflow (Schulz et al, 2016) and forest regions are accounted for by volume forces added to the momentum equation of the Navier-Stokes equations (Letzgus et al, 2018). The work of Klein et al (2018) introduced a revised coupling to the multi-body simulation tool SIMPACK.…”

Section: Unsteady Cfd Solver -Flowermentioning

confidence: 99%

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

Wenz

Langner²,

Lutz

et al. 2021

Preprint

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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.

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Section: Unsteady Cfd Solver -Flowermentioning

confidence: 99%

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

Wenz

Langner²,

Lutz

et al. 2021

Preprint

Self Cite

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show abstract

“…1, large parts of the test site, especially the escarpment, are covered by a dense forest. To be able to model vegetation in the simulation, adaptations in the FLOWer code are required, which were implemented in previous works (Letzgus et al, 2018). The implementation is based on the model of Shaw and Schumann (1992) for the implementation of leaf area densities above the height.…”

Section: Forest Setupmentioning

confidence: 99%

CFD Studies on Wind Turbine Interactions with the Turbulent Local Flow Field Influenced by Complex Topography and Thermal Stratification

Letzgus

Guma

Lutz

2021

Preprint

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Abstract. This paper shows the results of CFD studies of turbulent flow fields and their effects on a wind turbine in complex terrain. As part of the WINSENT project a research test site comprising four meteorological masts and two research wind turbines is currently being constructed in the Swabian Alps in Southern Germany. This work is an essential part of the research of the Southern German wind energy research cluster WindForS. The terrain site is characterised by a densely forested escarpment and a flat plateau downstream of the slope. The met masts and wind turbines are built on this plateau. In the first part, high-resolution CFD simulations are performed to separately investigate the effects of the forested escarpment and of thermal stratification on the flow field and on the wind turbine accordingly. In the second part, all the examined effects are combined for a real-life case dated March 2021. There, unstable conditions prevailed and the forest shows low leaf area densities due to the wintertime. It is shown that atmospheric turbulence, forests, orographies, and thermal stratification must be considered when assessing the impact of wind turbines in complex terrain. All of these effects influence the flow field both at the turbine position as well as in its wake. Turbulent structures of the forest wake cross the rotor plane temporarily and thereby affect the turbine inflow. Moreover, convective conditions and upward flows caused by the orography have an impact on the performance output as inclined flows result in asymmetric torque distributions. The wind turbine wake and the forest wake mix further downstream, resulting in a fast decay of the turbine wake. The paper also describes how the turbulent flow in the wake changes in the presence of thermal stratification.

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“…3a shows many small clusters with different heights. The implementation of the forest model in FLOWer (Letzgus et al, 2018) expects separate forest meshes when the forest characteristics change in flow direction making it unsuitable for small clusters. Therefore, the small clusters were summarized into six forest patches with different heights and LAD distributions which were included in the simulations.…”

Detached Eddy Simulations of the local Atmospheric Flow Field within a Forested Wind Energy Test Site located in Complex Terrain

Cited by 16 publications

References 12 publications

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

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

CFD Studies on Wind Turbine Interactions with the Turbulent Local Flow Field Influenced by Complex Topography and Thermal Stratification

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