Analysis 02: OWF Effect on the Ocean - On the Effect of Offshore Wind Farms on the Atmosphere and Ocean Dynamics - page 114

Onward, the analysis will be concentrated on the CTD data taken along four
sections westerly, northerly, easterly, and southerly of the wind farm alpha ventus
(Fig. 5.41 ). The northern and southern sections are around 12.80 km long, the
western and eastern ones around 10.90 km. The distance to alpha ventus

center
counts in longitude direction around 5.5 km and in latitude direction, 6.4 km
because of bordering prohibited zones based on wind farm constructions.
The arrangement of investigated locations was chosen based on previous model
results, with focus on catching modeled OWF effects.
The used model simulation for the evaluation is the run T012ug08
TS03HD30F01 of the model setup TOS-01 (ocean box), which means a wind
farm of 12 wind turbines (T012) within 4 grid cells, a wind forcing based on a
prescribed geostrophic wind of 8 m/s (ug08), a temperature and salinity start field
based on the measured profiles during the ship cruise (denoted as TS03), a model
depth of 30 m (HD30), and only a forcing being established by METRAS 10-m
wind field and surface pressure (denoted as F01).
Hence, the main differences have been simulation assumptions, and nature
conditions existing during the measuring campaign are the use of a simplified
meteorological forcing, not the exact same wind turbines (hub height difference
of 10 m, rotor diameter difference of 36 m, and different technical parameters), a
homogeneous water depth of 30 m, an averaged initial conditions for temperature,
and salinity based on taken CTD measurements, and in the model simulations the
tide is neglected.
Considering only meteorological pressure and wind, forcing is justified due to
the fact that there was no possibility to get an area-wide realistic meteorological
forcing (for example, satellite data) and due to the fact that dynamical oceanic
changes are dominantly driven by wind (result of Sect. 5.3.5 ). The decision of using
wind forcing based on a prescribed geostrophic wind of 8 m/s is leaned on to be the
closest description of wind situation discovered on-site.
The wind turbine parameters were not changed for the comparison simulation
due to computation time and costs, as well as because the used model resolution
tends to overestimate the wind wake dimension orthogonal to the wind direction.
Additionally, it must be said that during the measuring period, not even all of the
12 turbines were running all the time due to planned maintenance, and regarding
alpha ventus

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power plan, the turbines were not running with full power. Based on
these facts, it is supposed that the used smaller turbine may balance the later listed
issue of horizontal resolution and that the used wind turbine adjustment fits
reasonably with reality.
The bathymetry of model is flat, which is not a big limitation since the investi-
gation area around alpha ventus is known as flat and sandy with an average depth of
30 m in marine charts. Such a bottom topography was chosen because the depen-
dence of OWF effect on the water depth is relatively low, as shown in Sect. 5.3.6 .
It must be clear that this section provides an evidence of physical accuracy of
model results and gives an estimation of OWF effect

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s dimension by means of

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temperature analysis.