Publishers version - DTU Orbit

RMSPE (%)
70
60
50
40
30
20
10
0
vu u nnu n nns s vs
Atmospheric Stability (−)
Figure 170: Comparison of the root mean square percent error (RMSPE) in the prediction of
the systematic errors for the WindCube and ZephIR. The solid line is for the WindCube and
the dashed line is for the ZephIR with the low-pass filter. See table 19 for the meaning of the
abbreviations on the x-axis.
2 2
w'wcw' 0.6
0.5
0.4
0.3
0.2
0.1
Mast wake
0.0
0 50 100 150 200 250 300 350
Wind direction°
Figure 171: The ratio of the vertical velocity variance as measured by the WindCube and
the actual variance measured and modeled at 100 m. The thin lines are the theoretical
expectations using P = cos 2 Θ and Q = sin 2 Θ (solid line) and P = Q = 1/2 (dashed line)
in Eq. (307), respectively. The corresponding measurements are shown as broad curves with
the first and third quartiles displayed as shades
shown as a thin solid line in Fig. 171 and the latter as a thin dashed line. The spectral tensor
parameters used are for neutral atmospheric stability from Peña et al. (2010b) at 100 m. The
measurements of 〈w ′2
wc 〉/〈w′2 〉, shown as broad curves on Fig. 171, are from the same height,
and both, measurements and theory show that 〈w ′2
wc〉/〈w ′2
〉 using Leosphere’s choice of P
and Q can vary by a factor of two solely by changing the wind direction. If P = Q = 1/2 is
chosen the reduction of the vertical velocity variance does vary much less with wind direction,
DTU Wind Energy-E-Report-0029(EN) 255
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v
w