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wind tunnel
calibration
of ultrasonic anemometers
From
April 20 to 27 2001, a total of 12 ultrasonic anemometer were calibrated
by the University of Basel, the University of Padova and the Instituto
Politécnico de Bragança in a wind tunnel of the ETH-Zurich. From the
tunnel data matrix corrections were derrived. The calibration matrices
will be used to enhance the performance of the ultrasonic anemometers
operated during BUBBLE. |
|
 The
wind tunnel of the Institute
of Fluid Dynamics, Swiss Federal Institute of technology (ETH) has a
test section of 4m length with 3x2m in diameter.  The sonics
were operated upside down in the tunnel. They were continuously rotated
around their vertical axis at four different speeds (2, 4, 6 and 8 ms-1)
and eleven tilt positions between -25 and +25°. One rotation at one tilt
position lasted around five minutes. Additionally a reference propeller
vane (Meteolabor ONZ), the tunnel pitot speed, temperature and humidity
were sampled.
 The
instrument in the tunnel was precisely positioned with a positioning and
tilting device (CNC Nikken). The alignment was checked by a digital
inclinometer.
 From
all instruments raw data with a sampling rate of 20Hz was collected
(internal sampling rate 40Hz for USA-1). The raw data was streamed
together with the propeller speed and the position marks into files with a
software developed for this purpose in LabView.
Sample
plots from the wind tunnel (runs at 4ms-1
):
Gill
HS 000046 *
USA-1
9701001
USA-1
9903006 *
USA-1
9912002
USA-1
2001 04011
USA-1
2001 04012 *
USA-1
2001 04013 *
USA-1
2001 04014 *
USA-1
2001 04015 *
USA-1
2001 04016 *
USA-1
2001 04017
USA-1
2001 04018
*=operated during
BUBBLE
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|
The
wind tunnel of the Institute
of Fluid Dynamics, Swiss Federal Institute of technology (ETH) has a
test section of 4m length with 3x2m in diameter. 
