Turbulence Statistics and Spectra Observed from Joint Urban 2003

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Turbulence Statistics and Spectra Observed from
Joint Urban 2003

• G. Huynh, S. Chang, C. Klipp, C. Williamson, D.
  Garvey, and Y. Wang
• Battlefield Environment Division
• U.S. Army Research Laboratory
• Adelphi, MD 20783
• For BACIMO 2005, Monterey, CA
• Oct 12 14, 2005

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Turbulence Statistics and Spectra Observed from
Joint Urban 2003

• ARL deployed 5 towers with sonic anemometers
  sampling at 10 Hz at 10m, 5m and 2.5m AGL in a
  variety of locations in Oklahoma City.

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5
2
1
3
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Turbulence Statistics and Spectra Observed from
Joint Urban 2003
USGS aerial photos of five ARL tower
sites. (Obtained from U.S. Geological Survey,
Sioux Falls, SD)
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1
5
3
4
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Turbulence Statistics and Spectra Observed from
Joint Urban 2003
Suburban tower site (tower 1)
Photos by Young Yee, Army Research Lab. (7/2003)
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Turbulence Statistics and Spectra Observed from
Joint Urban 2003
Urban tower sites
tower 2
tower 5
Photos by Young Yee, Army Research Lab. (7/2003)
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Turbulence Statistics and Spectra Observed from
Joint Urban 2003
Estimated values of d (m) with respect to the
wind direction for the 5 ARL tower locations.
Reference Rotach (1994), BLM Vol.67, 187-193.
Wind Dir. Tower 1 Tower 2 Tower 3
Tower 4 Tower5
0 - 90
1.4 4.7 6.8
4.8 5.7 90 - 180 1.7
5.7 1.8 4.0
4.2 180 - 270 2.9 5.6
6.6 2.5 5.3 270 - 360
5.3 5.9 5.3
6.1 7.4
0 - 360 2.6
5.5 5.7 3.2
5.0


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Turbulence Statistics and Spectra Observed from
Joint Urban 2003
Scatter diagram of friction velocity, u, for
Tower 2 and Tower 3
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Turbulence Statistics and Spectra Observed from
Joint Urban 2003
Vertical variation of averaged friction velocity,
ltugt, for the 5 ARL towers.
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Turbulence Statistics and Spectra Observed from
Joint Urban 2003
Heat flux at 10m, 5m, and 2.5m level from Tower
2 on July 29, 2003.
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Turbulence Statistics and Spectra Observed from
Joint Urban 2003
Scatter diagram of heat flux, H, for Tower 2
and Tower 3
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Turbulence Statistics and Spectra Observed from
Joint Urban 2003
Vertical variation of averaged heat flux, ltHgt,
for the 5 ARL towers.
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Normalized standard deviations vs. (z-d)/L
from 5 ARL towers. The lines show the
Monin-Obukhov similarity relations.
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Turbulence intensities vs. (z - d)/L from 5
ARL tower locations . The lines show the
Monin-Obukhov similarity relations.
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Turbulence Statistics and Spectra Observed from
Joint Urban 2003
Variation of turbulence intensities , and
with four wind sectors (0-90o, 90-180o,
180-270o, 270-360o). measured at five tower
locations.
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Turbulence Statistics and Spectra Observed from
Joint Urban 2003
Linear regressions between turbulence intensities
vs. displacement height (d).
0.0382
0.2832
0.0376
0.2495
0.0174
0.1623
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Turbulence Statistics and Spectra Observed from
Joint Urban 2003
Normalized spectra for u, v, w, and T at
10m on suburban Tower 1 (solid black) and urban
Tower 2 (dashed red) at four different CDT times
on Jun 30 and Jul 01, 2003 versus fz/u on a
log-log plot where f is the natural frequency
(Hz), z is the measurement height, and U is the
30 minute averaged wind speed (m/s). The straight
lines indicate a -2/3 slope.
u
v
w
T
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Turbulence Statistics and Spectra Observed from
Joint Urban 2003
Conclusion
1. Turbulent momentum flux and heat flux,
ltugt and ltHgt, increase with height (z-d)/L, in
the Roughness Sublayer (RS), the lowest part of
the Surface Layer (SL). The classical concept of
constant flux in the SL can not be applied to the
RS. 2. The displacement height (d) appears to
be wind direction dependent, so are the
turbulence intensities in the RS. 3.
Normalized standard deviations of turbulent u, v,
w, and T and the turbulence intensities of u, v,
and w appear to be very scattered around
Monin-Obukhov similarity formulations. It implies
that the M-O similarity or local scaling can
hardly be applied to the RS. 4. There is a
significant shift of the normalized peak
frequency of the u, v, w, and T spectra toward
higher frequency from a suburban area to an urban
area.