Analysis 01: OWF Effect on the Atmosphere - On the Effect of Offshore Wind Farms on the Atmosphere and Ocean Dynamics - page 36

Fig. 4.1 Adopted Brostr¨m wind stress formulation on a reference wind stress field of 0.012 N/m 2
mean for two different wind stress direction and a characteristic wind farm length L of L¼

6 km.
Illustrations (a1)-(a3) show results for westerly direction of 270 . Illustrations (b1)-(b3) show
results for southwesterly direction of 240 . Illustration (a1)/(b1) gives the horizontal wind stress
field. OWF is placed in the middle, encased by dashed dotted lines , around P (0,0). Horizontal
resolution is 3 km 3 km. Solid lines mark the cross sections W-E, N-S/SW-NE, NW-SE

through the OWF. Illustration (a2)/(b2) represents wind stress along the cross section W-E/SE-
NE and (a3)/(b3) along cross section N-S/NW-SE. Dashed dotted lines in the cross section plots
mark the OWF ' s position; the dashed line in (a2), (b2) clarifies the wake dimension in wind
direction. The wind stress along cross sections points to the wake behind and within the wind farm

Table 4.1 Key notes of Brostr ¨ m adoption
Brostr¨m(6 6km 2 OWF, based on 10-m mean

wind by ug ¼ 8 m/s) Max Min

Wind direction W SW W SW

Inflow of wind farm â ■ æ ■ â ■ æ ■

Difference between OWFr-REFr [%] No

increase

No
increase

45.88 44.92

const: [N/m 2 ]

x ¼ 100 1.18 1.18 0.64 0.67

const: [N/m 2 ]

y ¼ 100 1.18 1.18 1.01 0.93

Wake x -dimension [km] 42 (W-E) 38 (SW-NE)

Wake y -dimension [km] 24 (N-S) 18 (NW-SE)

only the impact of the wind field or, more explicitly, of the wind stress field in one
special height can be described. The method cannot be easily adapted to other
atmospheric parameters like temperature, humidity, and additional forcing fields
normally needed for ocean simulations. Even characterized details of wind turbines