Measurements of Flow Distortion
within the CSAT3
Sonic Anemometer
T.W. Horst and S.R. Semmer
National Center for Atmospheric Research
E. Dellwik, J. Mann, N.Angelou
Technical University of Denmark
Measurements of Flow Distortion
within the CSAT3
Sonic Anemometer
• History of Sonic Development
Measurements of Flow Distortion
within the CSAT3
Sonic Anemometer
• History of Sonic Development
• CSAT 3 Transducer Shadowing
Measurements of Flow Distortion
within the CSAT3
Sonic Anemometer
• History of Sonic Development
• CSAT 3 Transducer Shadowing
• Field Tests of Transducer Shadowing
• NCAR Comparison to ATI-K sonics
Measurements of Flow Distortion
within the CSAT3
Sonic Anemometer
• History of Sonic Development
• CSAT 3 Transducer Shadowing
• Field Tests of Transducer Shadowing
• NCAR Comparison to ATI-K sonics
• DTU Comparison to Doppler LiDAR
Hamilton, New York
1. Introduction
Chandran Kaimal
Credit for the first sonic anemometer should be given to Carrier and Carlson (Croft Laboratories, Harvard University), who in 1944
nd beyond recovery. He had brought with him ideas
proach. These ideas were provided by Peter Schofer,
Kaimal-designed sonic anemometers with dedicated vertical paths
ble range
in the signals
ls could then
hat could be
prototype, but
my
table and
be sharp
s accurate
U.
and
s my thesis advisor.
Figure 1a
of Washington,
1960
ed by the atmospheric physics group at the Hanford
h scattered sage brush 1 m high. A 125-m high tower
ometer probe was mounted on a short mast with its
t and 0.5 m for the second.
nd beyond recovery. He had brought with him ideas
proach. These ideas were provided by Peter Schofer,
Kaimal-designed sonic anemometers with dedicated vertical paths
ble range
in the signals
ls could then
hat could be
prototype, but
my
table and
be sharp
s accurate
U.
and
s my thesis advisor.
Figure 1a
of Washington,
1960
ed by the atmospheric physics group at the Hanford
h scattered sage brush 1 m high. A 125-m high tower
ometer probe was mounted on a short mast with its
t and 0.5 m for the second.
AFCRL/EG&G, 1973
BAO/ATI, 1990
nd beyond recovery. He had brought with him ideas
proach. These ideas were provided by Peter Schofer,
Kaimal-designed sonic anemometers with dedicated vertical paths
ble range
in the signals
ls could then
hat could be
prototype, but
my
table and
be sharp
s accurate
U.
and
s my thesis advisor.
Figure 1a
of Washington,
1960
ed by the atmospheric physics group at the Hanford
h scattered sage brush 1 m high. A 125-m high tower
ometer probe was mounted on a short mast with its
t and 0.5 m for the second.
BAO/ATI, 1990
Kaimal (1979): Horizontal paths require
correction for transducer wakes
Impinging on the acoustic paths
AFCRL/EG&G, 1973
Transducer shadowing depends on
wind direction w.r.t. path and d/L (Kaimal, 1979)
University of Washington non-orthogonal
sonic anemometer, Businger and Oncley (1984)
CSAT3 Geometry and Coordinates
CSAT3 Transducer Shadowing, L/d = 18, d/L = 0.056
0.97
Vertical velocity statistics, such as <w’w’> and <w’Ts’>, are
measured to be greater with a vertical-path sonic than with a
non-orthogonal sonic.
Vertical velocity statistics, such as <w’w’> and <w’Ts’>, are
measured to be greater with a vertical-path sonic than with a
non-orthogonal sonic. CSAT3 transducer shadowing?
CSAT3 Transducer Shadowing, L/d = 18, d/L = 0.056
0.16
18
+
CSAT3 transducer shadowing measured in the NCAR wind tunnel
Marshall-2012 sonic anemometer field test
5 sonics at 3m height, 0.5 m spacing
CSAT.x
(test sonic)
ATI-K.e
CSAT.w
CSAT.va
ATI-K.w
(reference) (vertical a-path) (reference) (test sonic)
CSAT3 intercomparison with 3-component DOPPLER LiDAR
E. Dellwik, J. Mann, N. Angelou, E. Simley,
M. Sjoholm & T. Mikkelsen, Technical University of Denmark
Technical University of Denmark
Risø Wind Scanner Experiment
November, 2013
Inside
Outside
o
α
o
α
LiDARs focused Inside sonic measurement volume
u, v, w
LiDARs focused 80 cm Outside of sonic
u, v, w
Thin lines: Sonic; Thick lines, LiDAR (60 Hz data)
Two possible causes for sonic flow distortion
1. Transducer shadowing:
Wakes behind transducers.
2. Blocking of flow: Flow
speeds up within sonic.
• Strong dependence on wind
direction.
• Weak dependence on wind
direction.
Two possible causes for sonic flow distortion
1. Transducer shadowing:
Wakes behind transducers.
2. Blocking of flow: Flow
speeds up within sonic.
• Strong dependence on wind
direction.
• Weak dependence on wind
direction.
• Maximum effect near
transducers.
• Maximum effect near
center of sonic array.
Two possible causes for sonic flow distortion
1. Transducer shadowing:
Wakes behind transducers.
2. Blocking of flow: Flow
speeds up within sonic.
• Strong dependence on wind
direction.
• Weak dependence on wind
direction.
• Maximum effect near
transducers.
• Maximum effect near
center of sonic array.
• LiDAR and sonic data differ for
the Inside case.
• LiDAR and sonic data agree
for Inside case.
Two possible causes for sonic flow distortion
1. Transducer shadowing:
Wakes behind transducers.
2. Blocking of flow: Flow
speeds up within sonic.
• Strong dependence on wind
direction.
• Weak dependence on wind
direction.
• Maximum effect near
transducers.
• Maximum effect near
center of sonic array.
• LiDAR and sonic data differ for
the Inside case.
• LiDAR and sonic data agree
for Inside case.
• USonic/ULiDAR are the same for
Inside and Outside cases.
• USonic/ULiDAR are different for
Inside and Outside cases.
Outside case: k = USonic/ULiDAR , U = UZ
1.05
k = Usonic/Ulidar
1
0.95
0.9
uz
0.85
−50
0
50
100
Wind direction on sonic [°]
150
Outside case: k = USonic/ULiDar , U = UX,Y
1.05
k = Usonic/Ulidar
1
0.95
0.9
u
x
uy
0.85
−50
0
50
100
Wind direction on sonic [°]
150
Two possible causes for sonic flow distortion
1. Transducer shadowing:
Wakes behind transducers.
2. Blocking of flow: Flow
speeds up within sonic.
 Strong dependence on wind
direction.
• Weak dependence on wind
direction.
• LiDAR and sonic data differ for
the Inside case.
• LiDAR and sonic data agree
for Inside case.
• Maximum effect near
transducers.
• Maximum effect near
center of sonic array.
• USonic/ULiDAR are the same for
Inside and Outside cases.
• USonic/ULiDAR are different for
Inside and Outside cases.
Comparison between Inside and Outside cases, U = UZ
1.05
k = Usonic/Ulidar
1
0.95
0.9
uz
0.85
−50
0
50
100
Wind direction on sonic [°]
150
Comparison between Inside and Outside cases, U = UX,Y
1.05
k = Usonic/Ulidar
1
0.95
0.9
u
x
uy
0.85
−50
0
50
100
Wind direction on sonic [°]
150
Two possible causes for sonic flow distortion
1. Transducer shadowing:
Wakes behind transducers.
2. Blocking of flow: Flow
speeds up within sonic.
 Strong dependence on wind
direction.
• Weak dependence on wind
direction.
 LiDAR and sonic data differ for
the Inside case.
• LiDAR and sonic data agree
for Inside case.
• Maximum effect near
transducers.
• Maximum effect near
center of sonic array.
• USonic/ULiDAR are the same for
Inside and Outside cases.
• USonic/ULiDAR are different for
Inside and Outside cases.
Two possible causes for sonic flow distortion
1. Transducer shadowing:
Wakes behind transducers.
2. Blocking of flow: Flow
speeds up within sonic.
 Strong dependence on wind
direction.
• Weak dependence on wind
direction.
 LiDAR and sonic data differ for
the Inside case.
• LiDAR and sonic data agree
for Inside case.
 Maximum effect near
transducers.
• Maximum effect near
center of sonic array.
• USonic/ULiDAR are the same for
Inside and Outside cases.
• USonic/ULiDAR are different for
Inside and Outside cases.
Two possible causes for sonic flow distortion
1. Transducer shadowing:
Wakes behind transducers.
2. Blocking of flow: Flow
speeds up within sonic.
 Strong dependence on wind
direction.
• Weak dependence on wind
direction.
 LiDAR and sonic data differ for
the Inside case.
• LiDAR and sonic data agree
for Inside case.
 Maximum effect near
transducers.
• Maximum effect near
center of sonic array.
 USonic/ULiDAR are the same for
Inside and Outside cases.
• USonic/ULiDAR are different for
Inside and Outside cases.
Two possible causes for sonic flow distortion
 Transducer shadowing:
Wakes behind transducers.
2. Blocking of flow: Flow
speeds up within sonic.
 Strong dependence on wind
direction.
• Weak dependence on wind
direction.
 LiDAR and sonic data differ for
the Inside case.
• LiDAR and sonic data agree
for Inside case.
 Maximum effect near
transducers.
• Maximum effect near
center of sonic array.
 USonic/ULiDAR are the same for
Inside and Outside cases.
• USonic/ULiDAR are different for
Inside and Outside cases.
• Analysis is continuing of the DTU Wind Scanner/CSAT3 data,
with the goal of directly measuring the sonic anemometer flow
distortion/transducer shadowing.
• Analysis is continuing of the DTU Wind Scanner/CSAT3 data,
with the goal of directly measuring the sonic anemometer flow
distortion/transducer shadowing.
• Results of the NCAR data analysis will be published in
an upcoming issue of Boundary Layer Meteorology:
Horst, T.W., S.R. Semmer and G. Maclean,
Correction of a Non-Orthogonal, Three-Component Sonic
Anemometer for Flow Distortion by Transducer Shadowing,
Accepted, with minor revision, for publication in
Boundary Layer Meteorology.