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| Titel |
High-resolution offshore wake simulations with the LES model PALM |
| VerfasserIn |
B. Witha, G. Steinfeld, D. Heinemann, E. Stutz |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250068028
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| Zusammenfassung |
| The turbulent wake of a wind turbine is important especially in wind farms, as it can affect
the flow and power output of downstream turbines. Upstream turbines extract momentum of
the mean flow so that the power output of subsequent turbines is reduced. On the
other hand, the turbulence intensity is significantly enhanced which results in an
increased load for downstream turbines. The marine atmospheric boundary layer
is different from that onshore, especially in terms of a lower turbulence intensity
and a higher wind speed due to the smaller roughness. So far, there has been little
experience in simulating a realistic marine boundary layer. Models used for the
design and energy yield prediction of offshore wind farms usually base upon onshore
measurements.
Several wind turbine models have been implemented in the LES model PALM: a simple
uniformly loaded actuator disk model, an enhanced non-uniformly loaded actuator disk
model which also accounts for rotational effects and an actuator line model. The comparison
of the three turbine models for the wake of a single turbine shows, that the enhanced actuator
disk model is a significant improvement and provides similarly good results as the
computationally unfeasible actuator line model.
With the enhanced actuator disk model simulations of a single wake have been conducted,
using different inflow boundary conditions. The results have been compared with
observations from the offshore test site “alpha ventus”. So far, only cyclic inflow boundary
conditions have been used for wake simulations, whose major drawback is the re-inflow of air
already modified by the wind turbine. With non-cyclic boundary conditions, used for the first
time in wake simulations, the inflow profile at the turbine remains undisturbed and constant in
time. The additional application of a turbulent inflow results in a fully turbulent
flow already at the inflow boundary, so that the model domain can be significantly
reduced.
Finally, results of a simulation of the offshore wind farm “alpha ventus“ will be shown. |
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