[PPT] - The Role of Vegetation in Traffic Emission Dispersion and Air PowerPoint Presentation

SLIDE 1

1 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

The Role of Vegetation in Traffic Emission Dispersion and Air Quality in Urban Street Canyons

13th International Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes 1 - 4 June 2010, Paris, France

Christof Gromke 1,2 and Bodo Ruck 1

1 Institute for Hydromechanics, University of Karlsruhe/KIT, Germany 2 WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland

Christof Gromke, HARMO13, 1 - 4 June 2010, Paris, France

SLIDE 2

2 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Basics of Flow and Pollutant Dispersion in Street Canyons

Long street canyon (L/H > 7 and 0.7 ≤ W/H ≤ 2.2)

urban street canyon

approaching wind perpendicular to street axis

two dominating large scale vortex structures
Canyon Vortex
Corner Eddy
superposition at street canyon ends

idealized street canyon

Corner Eddy Canyon Vortex

Introduction Approach Results Max. Concentration CODASC Summary ○○ ○○○○○ ○○○○○○ ○ ○

SLIDE 3

3 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Canyon Vortex Corner Eddy

numerical simulation with k-ε turbulence closure scheme

wall A wall B Basics of Flow and Pollutant Dispersion in Street Canyons

long street canyon, incident flow α = 90°

Introduction Approach Results Max. Concentration CODASC Summary ○ ○○○○○ ○○○○○○ ○ ○

SLIDE 4

4 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Urban Street Canyons with Avenue-like Tree Planting

Implications of Trees on Flow and Pollutant Dispersion?

Introduction Approach Results Max. Concentration CODASC Summary ○○○○○ ○○○○○○ ○ ○

SLIDE 5

5 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Approach

Introduction Approach Results Max. Concentration CODASC Summary ○○○○○ ○○○○○○ ○ ○

SLIDE 6

6 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Experimental Investigations in the Boundary Layer Wind Tunnel

W = 18;36 m A B L = 180 m H = 18 m u(z) a = 0,30 traffic lane model trees concentration measuring taps roughness elements line source z y x

Boundary layer wind tunnel

closed-circuit BLWT
vortex generators and roughness elements
adjustable ceiling
power law profile exponent a = 0.30
ud = 7 ms-1, uH = 4.65 ms-1
Reynolds-No. Re = 37.000

Street Canyon Model and Boundary Layer Wind Tunnel

Street canyon model (scale 1:150)

isolated long street canyon (L/W = 10, W/H = 1;2 )
line source at street level
tracer gas (sulfur hexafluoride SF6)
126 measurement taps at canyon walls
traffic induced turbulence

Introduction Approach Results Max. Concentration CODASC Summary ○○○○ ○○○○○○ ○ ○

SLIDE 7

7 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Wind Tunnel Trees – Modeling Approach

Aerodynamic of trees is governed by crown porosity

permeable for wind
form and skin drag (volume specific surface)
wake characteristics

Characterization of crown porosity/permeability

pressure loss coefficient λ

[m-1] integral measure for flow resistance

d u ρ 2 1 p p = d p Δp = λ

2 lee luv dyn stat

Similarity requirement

[ ] [ ]

M = d d = λ λ ⇔ d λ = d λ ⇔ p Δp = p Δp

field model model field field model field dyn del mo dyn

Introduction Approach Results Max. Concentration CODASC Summary ○○○ ○○○○○○ ○ ○

SLIDE 8

8 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Realization of model trees Modeling of trees/avenue-like tree planting

crown porosity/permeability
PVol

= 97.5 … 96%

λmodel = 80 … 250 m-1
planting density (#trees/unit length)
similarity criterion

Application of similarity criterion

λ of tree crowns not available
λ of vegetation shelterbelts (Grunert et al. 1984)
λfield = 0.4 … 13.4 m-1
Similarity criterion:
λmodel = 60 … 2000 m-1

Wind Tunnel Trees – Modeling Approach

+

M = λ λ

model field

Introduction Approach Results Max. Concentration CODASC Summary ○○ ○○○○○○ ○ ○

SLIDE 9

9 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Street Canyon with Model Trees

Introduction Approach Results Max. Concentration CODASC Summary ○ ○○○○○○ ○ ○

SLIDE 10

10 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Overview: Wind Tunnel Experiments

Parameter study comprising 40 experiments

Variation of

street width to building height ratio W/H
angle of approaching flow α
planting density ρb
crown permeability λ (crown porosity PVol)
tree rows

(closed or open tree crown canopy)

traffic situation

www.codasc.de

(Concentration Data of Street Canyons)

Introduction Approach Results Max. Concentration CODASC Summary ○○○○○○ ○ ○

SLIDE 11

11 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Overview: Wind Tunnel Experiments

Parameter study comprising 40 experiments

Variation of

street width to building height ratio W/H
angle of approaching flow α
planting density ρb (#trees/unit length)
crown permeability λ (crown porosity PVol)
tree rows

(closed or open tree crown canopy)

traffic situation

www.codasc.de

(Concentration Data of Street Canyons)

Introduction Approach Results Max. Concentration CODASC Summary ○○○○○○ ○ ○

SLIDE 12

12 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Overview: Wind Tunnel Experiments

Parameter study comprising 40 experiments

Variation of

street width to building height ratio W/H
angle of approaching flow α
planting density ρb
crown permeability λ (crown porosity PVol)
tree rows

(closed or open tree crown canopy)

traffic situation

www.codasc.de

(Concentration Data of Street Canyons)

Introduction Approach Results Max. Concentration CODASC Summary ○○○○○○ ○ ○

SLIDE 13

13 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Measurement Results

Introduction Approach Results

Max. Concentration CODASC Summary

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SLIDE 14

14 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Pollutant Concentrations in narrow Street Canyon (W/H = 1, α = 90°)

Tree-free street canyon with wind approaching perpendicular

max. concentrations in central part of wall A close to the ground
concentrations at leeward wall A > windward wall B

(in wall average by 3.6)

concentration decreases towards street ends
concentration gradients give evidence for vortex structures

wall A wall B wind

normalized concentrations c+ [-]

5
4
3
2
1

1 2 3 4 5 y/H wall A 0.5 1 z/H

5
4
3
2
1

1 2 3 4 5 y/H wall B 0.5 1 z/H

Introduction Approach Results

Max. Concentration CODASC Summary

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SLIDE 15

15 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Pollutant Concentrations with Avenue-like Tree Planting (W/H = 1, α = 90°)

Single-row tree planting

high planting density ρb = 1.0, high crown porosity λ = 80 m-1 (PVol = 97.5%)

in comparison to tree-free street canyon

increase in concentrations at wall A (wall average: +41%)
decrease in concentrations at wall B (wall average: -38%)
in total: concentration increase

+ ref + ref + tree + c

c ) c c ( = δ change . rel

5
4
3
2
1

abs. 0.5 1 z/H

5
4
3
2
1

abs. 0.5 1 z/H 1 2 3 4 5 rel.

0. 5 1

1 2 3 4 5 rel.

0. 5 1

wall A wall B y/H y/H

Introduction Approach Results

Max. Concentration CODASC Summary

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SLIDE 16

16 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Pollutant Concentrations with Avenue-like Tree Planting (W/H = 1, α = 90°)

5
4
3
2
1

abs. 0.5 1 z/H 1 2 3 4 5 rel.

0. 5 1

wall A y/H

5
4
3
2
1

1 2 3 4 5 y/H wall A 0.5 1 z/H

Influence of decreased crown porosity/permeability

high planting density ρb = 1.0

tree-free λ = 80m-1 PVol = 97.5%

5
4
3
2
1

abs. 0.5 1 z/H 1 2 3 4 5 rel.

0. 5 1

wall A y/H

λ = ∞ PVol = 0%

5
4
3
2
1

abs. 0.5 1 z/H 1 2 3 4 5 rel.

0. 5 1

wall A y/H

λ = 200 m-1 PVol = 96%

PVol

+ λ

Introduction Approach Results

Max. Concentration CODASC Summary

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SLIDE 17

17 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Parameter Study on the Influence of Crown Permeability λ

Single-row tree planting (W/H = 1, α = 90°, high planting density ρb = 1)

wall A: increase of c+

wall increasing λ, max. change +60%

wall B: decrease of c+

wall increasing λ, max. change -50%

asymptotic limit

“impermeable” tree crown (λ = ∞)

c+

wall average

pressure loss coefficient λ

10 20 30 40 100 200 300

wall A wall B

Introduction Approach Results

Max. Concentration CODASC Summary

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SLIDE 18

18 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Pollutant Concentrations in Broad Street Canyon (W/H = 2)

Two-row tree planting (W/H = 2, α = 90 )

high planting density ρb = 1.0, low crown porosity λ = 200 m-1 (PVol = 96.0 %)

in comparison to tree-free street canyon (W/H = 2)

increase in concentrations at wall A (wall average: +41 %)
max. increases in the canyon center
decrease in concentrations at wall B (wall average: -32 %)

 implications analog to narrow street canyon (W/H = 1)

5
4
3
2
1

abs. 0.5 1 z/H

5
4
3
2
1

abs. 0.5 1 z/H 1 2 3 4 5 rel.

0. 5 1

1 2 3 4 5 rel.

0. 5 1

wall A wall B y/H y/H

Introduction Approach Results

Max. Concentration CODASC Summary

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SLIDE 19

19 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

wall A wall B

Pollutant Concentrations for Inclined Approaching Flow (W/H = 2, α = 45°)

Two-row tree planting (W/H = 2, α = 45 )

high planting density ρb = 1.0, low crown porosity λ = 200 m-1 (PVol = 96.0 %)
norm. concentrations c+ [-]
rel. changes δc

+ [-]

5
4
3
2
1

1 2 3 4 5 y/H wall A 0.5 1 z/H

5
4
3
2
1

1 2 3 4 5 y/H wall A 0.5 1 z/H

increases/decreases of concentrations at wall A (average: +88 %)
increases in concentration at wall B
accumulative traffic pollutant transport along street canyon axis
max. pollutant concentrations at canyon end
max. rel. changes in concentration for inclined approaching flow

Introduction Approach Results

Max. Concentration CODASC Summary

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SLIDE 20

20 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Maximum Pollutant Concentration

Introduction Approach Results Max. Concentration CODASC Summary ○ ○

SLIDE 21

21 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Maximum Pollutant Concentration at Canyon Wall

 

) α , H W ( f a e a a c

i ) P ( ρ a m ax

Vol b

 

 100 2 1

3

a1 a2 a3

0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 22.5 45 67.5 90 a 5 10 15 20 25 30 35 40 22.5 45 67.5 90 a 10 20 30 40 50 60 70 80 22.5 45 67.5 90 a

W/H = 1.0 W/H = 1.5 W/H = 2.0

Estimate for maximum traffic pollutant concentration c+

max was derived based on

40 wind tunnel experiments
dimensional analysis

) , , , (

max

a 

Vol b P

H W f c 



Introduction Approach Results Max. Concentration CODASC Summary ○

SLIDE 22

22 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Introduction Approach Results Max. Concentration CODASC Summary

CODASC

SLIDE 23

23 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

CODASC

Introduction Approach Results Max. Concentration CODASC Summary

CODASC - Concentration Data of Street Canyons

Internet data base
collection of wind tunnel concentration data
comprises more than 40 street canyon/tree planting configurations
contains also information on
approaching flow characteristics
street canyon geometry
vegetation/tree modeling approach
purpose: serve for the validation of numerical models and simulations

SLIDE 24

24 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Introduction Approach Results Max. Concentration CODASC Summary

SLIDE 25

25 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Introduction Approach Results Max. Concentration CODASC Summary

SLIDE 26

26 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

CODASC Concentration Data of Street Canyons

CODASC

www.codasc.de

Introduction Approach Results Max. Concentration CODASC Summary

SLIDE 27

27 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Summary and Conclusions

Introduction Approach Results Max. Concentration CODASC Summary

SLIDE 28

28 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Summary and Conclusion

Vegetation/Tree modeling approach for wind tunnel studies
accounts for the porosity/permeability of tree crowns/vegetation
is based on similarity criterion
proofed to give reasonable results in wind tunnel dispersion studies
Tree planting and traffic pollutant concentrations
tree planting resulted in higher/lower concentrations at the leeward/windward wall
overall increase in traffic pollutant concentrations
max. concentrations for flow approaching inclined
Maximum pollutant concentration
for regulatory purposes in dispersion modeling
can be used by town planers to estimate the implications of trees on pollutant concentrations

Introduction Approach Results Max. Concentration CODASC Summary

CODASC – Concentration Data of Street Canyons
comprises more than 40 wind tunnel experiments
is a useful tool for validation of CFD codes and numerical simulations

SLIDE 29

29 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Appendix

SLIDE 30

30 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Related Journal Papers

Buccolieri, R., Gromke, C., Di Sabatino, S., Ruck, B. (2009) Aerodynamic effects of trees on pollutant concentration in street canyons, Science of the Total Environment, Vol. 407, No. 19, pp. 5247-5256. Gromke, C., Ruck, B., (2009) Effects of trees on the dilution of vehicle exhaust emissions in urban street canyons, International Journal of Environment and Waste Management, Vol. 4, No. 1/2, pp. 225-242. Balczó, M., Gromke, C., Ruck, B. (2009) Numerical modeling of flow and pollutant dispersion in street canyons with tree planting, Meteorologische Zeitschrift, Vol. 18, pp. 197-206. Gromke, C., Ruck, B. (2009) On the impact of trees on dispersion processes of traffic emissions in street canyons, Boundary-Layer Meteorology, Vol.131, pp. 19-34. Gromke, C., Buccolieri, R., Di Sabatino, S., Ruck, B. (2008) Dispersion modeling study in a street canyon with tree planting by means of wind tunnel and numerical investigations - Evaluation of CFD data with experimental data, Atmospheric Environment, Vol. 42, pp. 8640-8650. Gromke, C., Ruck, B. (2008) Aerodynamic modeling of trees for small scale wind tunnel studies, Special Issue on Wind and Trees in Forestry, Vol. 81, No. 3, pp. 243-258. Gromke, C., Ruck, B. (2007) Influence of trees on the dispersion of pollutants in an urban street canyon – experimental investigation of the flow and concentration field, Atmospheric Environment, Vol. 41, pp. 3387-3302. Under Review Gromke, C., Ruck, B. () Wind-tunnel study and dimensional analysis on traffic pollutant concentrations in urban street canyons with trees, submitted to Boundary-Layer Meteorology. Buccolieri, R., Di Sabatino, S., Salim, M. S., Ielpo, P., Gennaro de, G., Piacentino, C. M., Chan, A., Gromke, C. () Influence

f tree planting on flow and pollutant dispersion in urban street canyons in Bari (Italy), submitted to Atmospheric Environment.

SLIDE 31

31 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Measurement Instrumentation

Concentration Measurements

Electron Capture Detector (ECD)

model Meltron LH 108

measurement of mean tracer gas

concentrations (sulfur hexafluoride SF6)

determination of dimensionless

concentrations c+ according to

l Q L u c c

T ref ref m

=

+

Velocity Measurements

Laser Doppler Velocimetry (LDV)
4 W Argon-Ion Laser
2-component LDV-system
Bragg-cells 40 MHz
backscatter system
sampling frequency 50 Hz

cm measured concentration uref reference velocity Lref reference length QT/l strength of line source

SLIDE 32

32 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

kinematic

Dimensional Analytical Considerations

) Q , ν , α , u , P , , , z , x , W , L , B , B , H ( f c

l H j , Vol i , ls i , ls B A 1 max j j k, K

x 

H, BA, BB

building length scales

L, W

street length scales

xls,i, zls,i

source positions

xK,j, Kj, tree positions and length scales
PVol,j

crown porosity

uH
char. velocity
α

angle of approaching flow

ν

kinematic viscosity

Ql

source strength

14 parameters

geometric

Estimate for the max. pollutant concentration

SLIDE 33

33 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Elimination of parameters

which have not been varied for the wind tunnel study
BA, BB building width
L street canyon length
are considered not to vary strongly in typical urban street canyons
xLq,i, zLq,i source positions
xK,j, Kj positions and length scales of trees
Buckingham π theorem
elimination of 2 more parameters
dimensionless π parameters

) H u Q , e R , α , P , ρ , H W ( f c

H l Vol b 2 max 

(6 parameters)

Dimensional Analytical Considerations

SLIDE 34

34 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Further considerations

π5 Reynolds No. Re = uHH/ν
sharp-edged geometries → critical Reynolds number similarity Recrit > 10.000
experimental evidence

=> cmax can be considered to be independent of Re

π6 dimensionless source strength Ql/(uHH)
cmax ~ Ql

(twofold source strength → twofold concentration) => cmax is linear in Ql/(uHH)

Dimensional Analytical Considerations

) α , P , ρ , H W ( f = c

Vol b 3 + max

(4 parameters)

) H u Q , e R , α , P , ρ , H W ( f c

H l Vol b 2 max 

(6 parameters)

SLIDE 35

35 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

ρb

planting density

PVol

crown porosity describe the avenue-like tree planting Idea: combination of ρb und PVol to a single "alley parameter" AP which is a measure for the amount of vegetation (solid crown material)

Dimensional Analytical Considerations

[ ]

> c ) % P

100

(

)

ρ ( = AP

i c Vol c b

2 1

General approach:

AP increases with increasing vegetation
determination/choice of values for c1 and c2 remains (moist obvious choice: c1 = c2 =1)

) α , P , ρ , H W ( f = c

Vol b 3 + max

(4 parameters)

) α , AP , H W ( f = c

4 + max

(“3” parameters)

SLIDE 36

36 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Relationship

=> exponential relationship between c+

max und AP

(W/H, α)

c+

max from experimental results for c1 = c2 = 1 =>

[ ])

% P

100

(

)

ρ ( = AP

Vol b

1 10 100 1 2 3 4 5 AP c+

max

1, 90° 1, 45° 1, 0° 2, 90° 2, 45° 2, 0°

SLIDE 37

37 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

) α , H W ( f = a , > a ) AP a

exp(

a

a

= c

i i 3 2 1 + max

Requirements to the relationship between c+

max and AP

exponential dependency
asymptotically approach c+

max for AP → ∞

Meaning of ai

a1 largest possible maximum concentration (AP → ∞)
a2 range of maximum concentrations (tree-free – AP → ∞)
a3 stretching factor
determination of ai by regression analyses in dependency of W/H and α

Relationship

General approach:

SLIDE 38

38 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Dimensional Analytical Considerations

[ ] { }

) α , H W ( f = a [%]) P 100 (

ρ

a exp a a = c

i Vol b 3 2 1 + max

determination of ai by regression analyses in dependency of W/H and α

a1 a2 a3

0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 22.5 45 67.5 90 a 5 10 15 20 25 30 35 40 22.5 45 67.5 90 a 10 20 30 40 50 60 70 80 22.5 45 67.5 90 a

W/H = 1.0 W/H = 1.5 W/H = 2.0

Functional relationship for c+

max

asymptotically approaches limit case λ → ∞

SLIDE 39

39 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Konzentrationen in "breiter" Straßenschlucht (B/H = 2, α = 90°)

5
4
3
2
1

1 2 3 4 5 y/H Wand A 0.5 1 z/H

5
4
3
2
1

1 2 3 4 5 y/H Wand B 0.5 1 z/H

Baumfreie Straßenschlucht (Referenzfall)

"enge" Straßenschlucht (B/H = 1) im Vergleich zur engen Straßenschlucht (B/H = 1)

geringere Konzentrationen an der leeseitigen Wand A

(im Wandmittel: -24 %)

ähnliche Maximalbelastung an Wand B
vergleichbare Verteilung der Konzentrationen

 Strömungsregime ähnlich, Schadstoffbelastung unkritischer

normierte Konzentrationen c+ [-]

SLIDE 40

40 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Konzentrationen bei Schräganströmung (B/H = 1, α = 45° )

Baumfreie Straßenschlucht (Referenzfall) bei Schräganströmung

5
4
3
2
1

1 2 3 4 5 y/H Wand A 0.5 1 z/H

5
4
3
2
1

1 2 3 4 5 y/H Wand B 0.5 1 z/H

Wand A Wand B Wind bei schräger Anströmung

Konzentrationen an Wand A deutlich höher als an Wand B
helixartige Wirbelstruktur (Überlagerung von Canyon Vortex und Paralleldurchströmung)
Totwassergebiet an Einströmseite von Wand A
max. Konzentrationen am Straßenschluchtende
akkumulativer Schadstofftransport entlang der Straßenlängsachse
kritisch bei längeren Straßenschluchten (L/H > 10)

normierte Konzentrationen c+ [-]

SLIDE 41

41 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

norm. concentrations c+ [-]
rel. changes δc

+ [-]

increases and decreases of concentrations at wall A (wall average: +91 %)
decreases in concentration at wall B (wall average: -49 %)
accumulative traffic pollutant transport along street canyon axis
max. rel. changes in concentration for inclined approaching flow
max. pollutant concentrations at canyon end

wall A wall B

Pollutant Concentrations for Inclined Approaching Flow (W/H = 1, α = 45°)

Single-row tree planting

high planting density ρb = 1.0, high crown porosity λ = 80 m-1 (PVol = 97.5%)
5
4
3
2
1

1 2 3 4 5 y/H wall A 0.5 1 z/H

5
4
3
2
1

1 2 3 4 5 y/H wall A 0.5 1 z/H

SLIDE 42

42 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

0.4
0.2

0.2 0.4 x/H 0.2 0.4 0.6 0.8 1 1.2 z/H

impermeable crown (9 m x 12 m) LDV Measurement

Comparison of impermeable and permeable tree crown

continuous block-shaped permeable crown

(97 % pore volume, l = 250 Pa Pa-1m-1) w+ = w/uref [-]

0.4
0.2

0.2 0.4 x/H 0.2 0.4 0.6 0.8 1 1.2 z/H

permeable crown (9 m x 12 m) LDV Measurement

w+ = w/uref [-] impermeable - permeable

vertical velocities

are similar

volume flux at z/H = 0.7

differs only by 8 %

no significant influence
f crown permeability
n flow field

Influence of Crown Porosity on Velocity Field

SLIDE 43

43 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Traffic induced Turbulence

W P T P P T 

H 3 u f c W P d  

H W 3 T u T F T n D c T P  

Turbulence production ratio TP

turbulence production by moving traffic assumption (total kin. energy of traffic is transformed into TKE ) turbulence production by interaction of building environment with atmospheric wind Similarity is given when: TP,Model = TP,Nature

SLIDE 44

44 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Konzentrationen bei Berücksichtigung Verkehrsinduzierter Turbulenz

Referenzfall: Baumfreie Straßenschlucht B/H = 1 bei senkrechter Anströmung

Gegenverkehr, uv = 40 km/h
Verkehrsstärke nv = 37 Kfz/km
cf = 0.02 (cf = ρu*

2/(0.5 ρUδ 2))

Turbulenzproduktion PW ≈ 10 PT
Konzentrationsabnahmen
Wand A: 2 %
Wand B: 31 %

Wand A Wand B Wind

5
4
3
2
1

1 2 3 4 5 y/H Wand A 0.5 1 z/H

5
4
3
2
1

1 2 3 4 5 y/H Wand B 0.5 1 z/H

5
4
3
2
1

1 2 3 4 5 y/H Wand A 0.5 1 z/H

5
4
3
2
1

1 2 3 4 5 y/H Wand B 0.5 1 z/H

mit Verkehr

hne Verkehr

SLIDE 45

45 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

5
4
3
2
1

1 2 3 4 5 y/H Wand A 0.5 1 z/H

5
4
3
2
1

1 2 3 4 5 y/H Wand B 0.5 1 z/H

Konzentrationen bei Berücksichtigung Verkehrsinduzierter Turbulenz

Straßenschlucht mit impermeabler Baumpflanzung (B/H = 1, α = 90 )

mit Verkehr

hne Verkehr
Gegenverkehr, uv = 40 km/h
Verkehrsstärke nv = 37 Kfz/km
cf = 0.02 (cf = ρu*

2/(0.5 ρUδ 2))

Konzentrationsänderungen
Wand A: -23 %
Wand B: +19 %
5
4
3
2
1

1 2 3 4 5 y/H Wand A 0.5 1 z/H

5
4
3
2
1

1 2 3 4 5 y/H Wand B 0.5 1 z/H

SLIDE 46

46 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Dimensionsanalytische Betrachtung

Elimination der Basisgröße Länge [L] durch Einflussgröße Gebäudehöhe H

c H B ρb PVol uH α ν Ql x y z L 1 1 1 2 2 1 1 1 T

1
1
1

c B/H ρb PVol uH/H α ν/H2 Ql/H2 x/H y/H z/H L T

1
1
1

π1 π2 π3 π4 π5 π6 π7 π8 π9 π10 c B/H ρb PVol α ν/(uHH) Ql/(uHH) x/H y/H z/H L T

Aufstellen der Dimensionsmatrix Elimination der Basisgröße Zeit [T] durch Einflussgrößenkombination H/uH

SLIDE 47

47 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Funktionaler Zusammenhang

Regressionsanalysen zur Bestimmung der Parameter ai

2.) Beschreibung der Parameter ai in Abhängigkeit der π Gruppen B/H und α mittels gemischt quadratischer Polynomansatz für funktionalen Zusammenhang ai = f(B/H,α)

2 2 8 2 7 2 6 5 2 4 2 3 2 1

a a a a a a                                              H B c H B c H B c H B c c H B c c H B c c a

i i i i i i i i i i

j j j j j j H B i

c H B c a a

a

 

 

       

2 , 2 , /

3.) Regressionsanalyse zur Bestimmung der Parameter ci

ci0 ci1 ci2 ci3 ci4 ci5 ci6 ci7 ci8 i = 1 55.3

23.8

94.2 0.0

48.7
15.5

0.0 10.7 0.0 i = 2 14.1

5.3

41.0 0.0

17.6

6.4 0.0

6.0

0.0 i = 3 0.0 0.9 0.3 0.0

0.2
0.8

0.0 0.4 0.0

SLIDE 48

48 Christof Gromke

Institute for Hydromechanics, University of Karlsruhe/KIT WSL Institute for Snow and Avalanche Research SLF

Funktionaler Zusammenhang

a1 a2 a3

100 22.5 45 67.5 90

B/H = 1 (Tab. 9.1) B/H = 2 (Tab. 9.1) B/H = 1 (Gl. 9.13) B/H = 2 (Gl. 9.13) B/H = 1.5 (Gl. 9.13) 0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 22.5 45 67.5 90 a 5 10 15 20 25 30 35 40 22.5 45 67.5 90 a 10 20 30 40 50 60 70 80 22.5 45 67.5 90 a

Gegenüberstellung berechneter und aus Windkanalversuchen resultierenden Parametern ai

1.0 < B/H < 2.0 Zwischenwerte liegen im physikalischen sinnvollen Bereich (B/H = 1.5)
höchst mögliche Maximalkonzentrationen bei schräger Anströmung (α ≈ 50 … 55 )