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| Titel |
Turbulent flow and scalar flux through and over aligned and staggered wind farms |
| VerfasserIn |
C. D. Markfort, W. Zhang, F. Porte-Agel |
| 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 |
250070691
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| Zusammenfassung |
| Wind farm-atmosphere interaction is complicated by the effect of turbine array configuration
on momentum, scalar and kinetic energy fluxes. Wind turbine arrays are often arranged in
rectilinear grids and, depending on the wind direction, may be perfectly aligned or
perfectly staggered. The two extreme configurations make up the end members of a
spectrum of infinite possible layouts. A wind farm of finite length may be modeled
as an added roughness or as a canopy in large-scale weather and climate models.
However, it is not clear which analogy is physically more appropriate. Also, surface
scalar flux, including heat, evaporation and trace gas (e.g. CO2) fluxes affected by
wind farms, need to be properly parameterized in large-scale models. Experiments
involving model wind farms in aligned and staggered configurations, consisting of 13
rows with equivalent turbine density, were conducted in a thermally-controlled
boundary-layer wind tunnel. Measurements of the turbulent flow were made using
a custom x-wire/cold wire within and over the wind farms. Particular focus was
placed on studying the effect of wind farm layout on flow adjustment, momentum
and scalar fluxes, and turbulent kinetic energy distribution. Results show that the
turbulence statistics of the flow exhibit similar turbulent transport properties to
those of canopy flows, but retain some characteristic surface layer properties in a
limited region above the wind farms as well. The initial wake growth over columns
of turbines in the aligned wind farm is faster. However, the overall wake adjusts
within and grows more rapidly over the staggered farm. The effective roughness of
the staggered farm was found to be significantly larger than that of the aligned
farm. The flow equilibrates faster, and the overall momentum absorption is higher
for the staggered compared to the aligned farm, which is consistent with canopy
scaling. Lower surface heat flux was found for the wind farms compared to the
boundary-layer flow without turbines, with a greater reduction in the staggered case. |
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