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Titel:
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TNO boundary layer tunnel. Quality of velocity profiles.
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Auteur(s):
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Gepubliceerd door:
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Publicatie datum:
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ECN
Windenergie
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1-5-2005
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ECN publicatienummer:
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Publicatie type:
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ECN-C--05-050
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ECN rapport
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Aantal pagina's:
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Volledige tekst:
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28
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Download PDF
(521kB)
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Samenvatting:
Thevelocity profiles and Reynolds stresses of the empty boundary layer
tunnel of TNO Apeldoorn have been characterized. This tunnel has a measurement
section of 3 m wide, 2 meters high, and 9 meters long. The tunnel was
set up to represent an offshore atmospheric boundary layer scaled by
a factor of 400. The measurements were carried out by a hotwire traverse
system. The results are listed below.
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characteristic
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neutrally stable, offshore atmosphere in reality
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empty TNO-tunnel (6-9 m/s)
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vertical velocity profile
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logarithmic
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logarithmic up to 80 cm height (320m
on scale) over first 9 m (3600m on scale);
separate fits of lower 17 cm yield
25% larger values for u*.
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horizontal velocity profile
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flat
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varies by 3% over tunnel width between
17 and 37 cm height (68m - 148m on scale)
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friction velocity u*
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constant
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varies by 9% over first 9 meters
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shear stress
(Reynolds stress, <u'w'>)
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'independent' of height
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'independent' of height in first
4.5 meters.
decreases about 30% in 80 cm height in next 4.5 meters.
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surface roughness z0
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0.2 mm
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0.4-7.2*10-4 mm (0.02-0.3
mm on scale)
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dynamic pressure gradient in wind
direction dP/dx
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'none'
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» -0.5 Pa/m (-1.3 Pa/km
on scale)
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We conclude
that the test section of the tunnel represents offshore conditions well
in an on-scale area ranging from sea level to 320 m altitude and extending
over 3.6 km in flow direction.
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