ANALYSIS OF TRACER DATA FROM URBAN DISPERSION EXPERIMENTS Akula Venkatram and Vlad Isakov Motivation for Field Experiments Field Studies Conducted in Barrio Logan Results from Current Models New Modeling Approach Results Future Work
Dec 16, 2015
ANALYSIS OF TRACER DATA FROM URBAN DISPERSION EXPERIMENTS
Akula Venkatram and Vlad Isakov
Motivation for Field Experiments Field Studies Conducted in Barrio
Logan Results from Current Models New Modeling Approach Results Future Work
Motivation Few experiments conducted for
ground-level releases in urban areas.– St Louis Experiment in 1968
Little data for near source dispersion
Data set is specific to Barrio Logan
Urban Effects on Dispersion
Stable air from the rural area becomes unstable when it flows over warmer urban area
Roughness increases turbulence and decreases wind speed
Field Experiments
Tracer studies designed to study dispersion at scales of meters to kilometers in urban areas.– Near source experiment at Memorial High,
April 2001– CE-CERT parking lot study, April-May 2001 – Summer and winter Barrio Logan field
studies– Dugway Proving Grounds Model Study
Near Field Dispersion-tens of meters
SF6 released at ground level in a school playground in an urban area
Source surrounded by two arcs at 10 and 20 meters
Flow measured with sonics, propeller anemometers, and mini-sodar
Real time analysis of data
Near source dispersion
v is comparable to effective wind speed transporting plume
Upwind dispersion becomes important
Plume model might not be applicable
Concentration Pattern on 4/14/01
-25 -20 -15 -10 -5 0 5 10 15 20 25-25
-20
-15
-10
-5
0
5
10
15
20
25
853
105
1319
142
176
122
Concentrations(ppt) for half hour ending 4/14/01 14:30
X
4
8
123
5
7
141
Y
u = (1.2815)i+ (1.1118)jDirection Vector
Concentration Pattern on 4/14/01
-25 -20 -15 -10 -5 0 5 10 15 20 25-25
-20
-15
-10
-5
0
5
10
15
20
25
0
76
1
108
123
83
Concentrations for half hour ending 4/14/01 05:30
X
0
63
330
0
436
221
Y
u = (-0.73455)i+ (-0.10971)j
Concentration Pattern on 4/13/01
-25 -20 -15 -10 -5 0 5 10 15 20 25-25
-20
-15
-10
-5
0
5
10
15
20
25
1148
151
1586
212
115
108
Concentrations(ppt) for half hour ending 4/13/01 11:30
X
34
37
120
32
35
98
Y
u = (1.2506)i+ (-0.83009)jDirection Vector
Concentration Pattern on 4/12/01
-25 -20 -15 -10 -5 0 5 10 15 20 25-25
-20
-15
-10
-5
0
5
10
15
20
25
19
709
9
610
339
448
Concentrations for half hour ending 4/12/01 20:00
X
2
58
639
0
0
399
Y
u = (1.8729)i+ (-0.38128)j
Low Wind Speed Model
The horizontal distribution is written as:
2y
2m
2v
2v
ran
2y
2
yranran
x2
u22
f
2y
exp21
)f1(r2
1f)y,x(H
Tracer Experiment at Barrio LoganTracer Experiment at Barrio Logan
Tracer Experiment conducted in August and December of 2001
Hourly SF6 concentrations sampled at 50 sites Tracer released at NASSCO during daytime
from 10 a.m. to 10 p.m.
Mobile van sampled continuously to measure crosswind SF6 concentrations
Mini-sodar to measure vertical winds up to 200m at 5m resolution
Six sonic anemometers to measure surface level winds and turbulence
WIND ROSE PLOT
Station #72290 - ,
NORTH
SOUTH
WEST EAST
3%
6%
9%
12%
15%
Wind Speed (m/s)
> 11.06
8.49 - 11.06
5.40 - 8.49
3.34 - 5.40
1.80 - 3.34
0.51 - 1.80
UNIT
m/s
DISPLAY
Wind Speed
CALM WINDS
11.05%
MODELER
DATE
10/2/01
COMPANY NAME
CARB
COMMENTS
WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com
PLOT YEAR-DATE-TIME
2000 Jan 1 - Dec 31Midnight - 11 PM
AVG. WIND SPEED
2.12 m/s
ORIENTATION
Direction(blowing from)
PROJECT/PLOT NO.
Logan Memorial
Logan Memorial Wind RoseLogan Memorial Wind Rose
Nov 1, 1999 to
Oct 31, 2000
Sea Breeze (predominately daytime)
Land Breeze (predominately nighttime)
Map of Barrio Logan tracer experimentAugust 2001
yellow dotd -stationarysamplersblack lines - mobile vanlocations
Model for Urban Areas
Micrometeorological variables used to describe flat terrain dispersion do not apply to urban areas
Formulate model that uses measured turbulence and velocity profiles
Model for Plume Spread
)mp(1pm
ref
zrzrz
)mp(1p
ref
zryry
m
ref
zwrefw
p
ref
zref
zσ
σσ
zσ
σσ
get you
zσ
σσ ;zσ
UU
If
Comparison with Prairie Grass Data
Observed and Predicted Horizontal Spreads
Convective Boundary Layer
1
10
100
1000
1.0 10.0 100.0 1000.0
Predicted Sigma- Y (m)
Obse
rved S
igm
a-Y (
m)
Comparison with Prairie Grass Data
Observed versus Predicted Concentrations
Convective Boundary layer- Prairie Grass
1
10
100
1000
10000
1.0 10.0 100.0 1000.0 10000.0
Modeled Concentration (us/m3)
Obs
erve
d Con
cent
rati
on (
us/m
3)
Comparison with Prairie Grass Data
Observed versus Predicted Horizontal Spreads
Stable Boundary Layer- Prairie Grass
1
10
100
1.0 10.0 100.0
Predicted Sigma- y (m)
Obs
erve
d S
igm
a-y
(m)
Comparison with Prairie Grass DataObserved Versus Modeled Concentrations
Stable Boundary Layer- Prairie Grass
1
10
100
1000
10000
100000
1.0 10.0 100.0 1000.0 10000.0 100000.0
Modeled Concentration (us/m3)
Obs
erve
d Co
ncen
trat
ion
(us/
m3)
Model Field Study
Understand dispersion in flat terrain at distances of less than 50 m
Examine the effect of increasingly complicated building structures on– Turbulence– Dispersion
Model Field Study
Conducted at Dugway Proving Ground, Utah July 17,18,19,26 2001
13.5 hours under a variety of stability conditions
Velocity and turbulence measured with sonic anemometers
Buildings simulated with barrels
Model Urban Area 59 array of 45 barrels H=0.91 m and D=0.57 m at spacing
of 1.8 m- frontal area/plan area=16% Propylene released at z=0 and z=H 6 different configurations to examine
the effect of release height and source structure
Concentration Measurements
Tracer measured with 43 PIDs arranged in 3, 50 degree arcs
Arcs at 1.5S, 2.5S, and 4.5S PIDs at 5o spacing PIDs located at z=0.23 m Four 2 m towers were used to
measure vertical profiles Concentrations measured at 50 Hz
Meteorological Measurements
Turbulence measured with 6 sonics Sonics mounted on 3 and 5 m
towers Mounted at 0.5, 1.5, 2.2 and 3.5H
at various distances from the source
Measurements at 20 Hz
Figure 2. Observed versus Predicted concentration using model plume spreads without obstacle for ground level release
1.0E-02
1.0E-01
1.0E+00
1.0E-02 1.0E-01 1.0E+00
Pred. Conc. (gm/m3)
Obs.
Con
c. (
gm/m
3)
Figure 3. Observed versus Predicted concentration using linear plume spreads with one obstacle in array for ground level release
1.0E-03
1.0E-02
1.0E-01
1.0E+00
1.0E-03 1.0E-02 1.0E-01 1.0E+00
Pred. Conc. (gm/m3)
Obs
. Co
nc.
(gm
/m3)
Figure 4. Observed versus Predicted concentration using model plume spreads with one obstacle in array for ground level release
1.0E-03
1.0E-02
1.0E-01
1.0E+00
1.0E-03 1.0E-02 1.0E-01 1.0E+00
Pred. Conc. (gm/m3)
Obs
. Co
nc.
(gm
/m3)
Figure 6. Observed versus Predicted concentration using model plume spreads with two obstacles in array for ground level release
1.0E-03
1.0E-02
1.0E-01
1.0E+00
1.0E-03 1.0E-02 1.0E-01 1.0E+00
Pred. Conc. (gm/ m3)
Obs
. Co
nc.
(gm
/m3)