|
Title:
|
|
TNO boundary layer tunnel. Quality of velocity profiles.
|
|
|
|
Author(s):
|
|
|
|
|
|
Published by:
|
Publication date:
|
|
ECN
Wind Energy
|
1-5-2005
|
|
|
|
ECN report number:
|
Document type:
|
|
ECN-C--05-050
|
ECN publication
|
|
|
|
Number of pages:
|
Full text:
|
|
28
|
Download PDF
|
Abstract:
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.
|
characteristic
|
neutrally stable, offshore atmosphere in reality
|
empty TNO-tunnel (6-9 m/s)
|
|
vertical velocity profile
|
logarithmic
|
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*.
|
|
horizontal velocity profile
|
flat
|
varies by 3% over tunnel width between
17 and 37 cm height (68m - 148m on scale)
|
|
friction velocity u*
|
constant
|
varies by 9% over first 9 meters
|
|
shear stress
(Reynolds stress, <u'w'>)
|
'independent' of height
|
'independent' of height in first
4.5 meters.
decreases about 30% in 80 cm height in next 4.5 meters.
|
|
surface roughness z0
|
0.2 mm
|
0.4-7.2*10-4 mm (0.02-0.3
mm on scale)
|
|
dynamic pressure gradient in wind
direction dP/dx
|
'none'
|
» -0.5 Pa/m (-1.3 Pa/km
on scale)
|
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.
Back to List