Complete Characterization of Turbulence in Directions, Wind Speeds, - - PowerPoint PPT Presentation

Complete Characterization of Turbulence in an Urban Canyon Under All Wind Directions, Wind Speeds, and Thermal Stability Conditions Amir A. Aliabadi, Mohsen Moradi, Denis Clement, William D. Lubitz, & Bahram Gharabaghi Introduction

Background Objective

Methodology

Experimental

Results and Discussion

Mean Quantities Turbulence Statistics Scaling Analysis

Conclusions Future Work Acknowledgements References

Complete Characterization of Turbulence in an Urban Canyon Under All Wind Directions, Wind Speeds, and Thermal Stability Conditions

Amir A. Aliabadi, Mohsen Moradi, Denis Clement, William D. Lubitz, & Bahram Gharabaghi

University of Guelph American Meteorological Society, 10th International Conference on Urban Climate/ 14th Symposium on the Urban Environment

August 1, 2018

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Complete Characterization of Turbulence in an Urban Canyon Under All Wind Directions, Wind Speeds, and Thermal Stability Conditions Amir A. Aliabadi, Mohsen Moradi, Denis Clement, William D. Lubitz, & Bahram Gharabaghi Introduction

Background Objective

Methodology

Experimental

Results and Discussion

Mean Quantities Turbulence Statistics Scaling Analysis

Conclusions Future Work Acknowledgements References

Outline

Introduction Background Objective Methodology Experimental Results and Discussion Mean Quantities Turbulence Statistics Scaling Analysis Conclusions Future Work Acknowledgements References

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Complete Characterization of Turbulence in an Urban Canyon Under All Wind Directions, Wind Speeds, and Thermal Stability Conditions Amir A. Aliabadi, Mohsen Moradi, Denis Clement, William D. Lubitz, & Bahram Gharabaghi Introduction

Background Objective

Methodology

Experimental

Results and Discussion

Mean Quantities Turbulence Statistics Scaling Analysis

Conclusions Future Work Acknowledgements References

Introduction

Background

◮ Urban roughness sublayer: the lowest portion of the

atmospheric boundary layer over urban areas that exhibits numerous complexities [Raupach et al., 1980]

◮ Urban micro-climate and air quality: driven by vertical

and horizontal exchanges of momentum, heat, and pollutants within the urban roughness sublayer

◮ Gaps in the literature: few field observations, oblique

wind directions, low wind speeds, non-neutral stability conditions, horizontal exchanges, scaling

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Complete Characterization of Turbulence in an Urban Canyon Under All Wind Directions, Wind Speeds, and Thermal Stability Conditions Amir A. Aliabadi, Mohsen Moradi, Denis Clement, William D. Lubitz, & Bahram Gharabaghi Introduction

Background Objective

Methodology

Experimental

Results and Discussion

Mean Quantities Turbulence Statistics Scaling Analysis

Conclusions Future Work Acknowledgements References

Introduction

Objective

Figure: Reek Walk at University of Guelph; Quasi 2D canyon, 55-m long and 13-m high with unit aspect ratio [Aliabadi et al., 2018]

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Complete Characterization of Turbulence in an Urban Canyon Under All Wind Directions, Wind Speeds, and Thermal Stability Conditions Amir A. Aliabadi, Mohsen Moradi, Denis Clement, William D. Lubitz, & Bahram Gharabaghi Introduction

Background Objective

Methodology

Experimental

Results and Discussion

Mean Quantities Turbulence Statistics Scaling Analysis

Conclusions Future Work Acknowledgements References

Introduction

Objective

Figure: Turfgrass Institute rural site; 1.2 km away from campus; Weather station for World Meteorological Organization (WMO)

• perated by Environment and Climate Change Canada (ECCC)

[Aliabadi et al., 2018]

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Complete Characterization of Turbulence in an Urban Canyon Under All Wind Directions, Wind Speeds, and Thermal Stability Conditions Amir A. Aliabadi, Mohsen Moradi, Denis Clement, William D. Lubitz, & Bahram Gharabaghi Introduction

Background Objective

Methodology

Experimental

Results and Discussion

Mean Quantities Turbulence Statistics Scaling Analysis

Conclusions Future Work Acknowledgements References

Introduction

Objective

◮ Investigate Urban Heat Island (UHI) effect. ◮ Quantify horizontal and vertical turbulence exchanges

• f momentum and heat.

◮ Consider a comprehensive set of wind directions, wind

speeds, and thermal stability conditions.

◮ Perform scaling analysis with surface and near surface

parameters.

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Complete Characterization of Turbulence in an Urban Canyon Under All Wind Directions, Wind Speeds, and Thermal Stability Conditions Amir A. Aliabadi, Mohsen Moradi, Denis Clement, William D. Lubitz, & Bahram Gharabaghi Introduction

Background Objective

Methodology

Experimental

Results and Discussion

Mean Quantities Turbulence Statistics Scaling Analysis

Conclusions Future Work Acknowledgements References

Methodology

Experimental

◮ Ultrasonic anemometers: 2 Young 81000 anemometers

2-m high above street and roof; sampling at 4 Hz

◮ Temperature and relative humidity: 1 Campbell

Scientific HMP60 at street level

◮ Data logging: 2 Campbell Scientific CR-1000 data

loggers

◮ Thermal imaging: 1 FLIR E4 thermal camera for

surface temperature mapping

◮ Tethered balloon: Tethered And Navigated Air Blimp

(TANAB) to measure relative humidity and temperature

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Complete Characterization of Turbulence in an Urban Canyon Under All Wind Directions, Wind Speeds, and Thermal Stability Conditions Amir A. Aliabadi, Mohsen Moradi, Denis Clement, William D. Lubitz, & Bahram Gharabaghi Introduction

Background Objective

Methodology

Experimental

Results and Discussion

Mean Quantities Turbulence Statistics Scaling Analysis

Conclusions Future Work Acknowledgements References

Methodology

Experimental

Figure: Left: TANAB0, 2-m3 Latex balloon, filled with helium, 1.2-kg lift, measures position, temperature, and relative humidity; Right TANAB1, 8-m3 Polyurethane balloon filled with helium, 3.0-kg lift, measures position, temperature, relative humidity, pressure, wind, and thermal imaging

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Complete Characterization of Turbulence in an Urban Canyon Under All Wind Directions, Wind Speeds, and Thermal Stability Conditions Amir A. Aliabadi, Mohsen Moradi, Denis Clement, William D. Lubitz, & Bahram Gharabaghi Introduction

Background Objective

Methodology

Experimental

Results and Discussion

Mean Quantities Turbulence Statistics Scaling Analysis

Conclusions Future Work Acknowledgements References

Results and Discussion

Mean Quantities

Figure: Top: atmospheric and surface temperatures; Bottom: Urban Heat Island (UHI) intensity measured as 0.7 K ± 1.2 K; compared to 1.5-4.0K for London, UK, in September [Barlow et al., 2015]

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Complete Characterization of Turbulence in an Urban Canyon Under All Wind Directions, Wind Speeds, and Thermal Stability Conditions Amir A. Aliabadi, Mohsen Moradi, Denis Clement, William D. Lubitz, & Bahram Gharabaghi Introduction

Background Objective

Methodology

Experimental

Results and Discussion

Mean Quantities Turbulence Statistics Scaling Analysis

Conclusions Future Work Acknowledgements References

Results and Discussion

Mean Quantities

Figure: Left: TANAB profiles of temperature; stable-neutral-unstable roughness sublayer; local heating near roof at 0700 Local Standard Time (LST); Right: TANAB profiles of relative humidity; local heating near roof and reduction in relative humidity at 0700 LST

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Complete Characterization of Turbulence in an Urban Canyon Under All Wind Directions, Wind Speeds, and Thermal Stability Conditions Amir A. Aliabadi, Mohsen Moradi, Denis Clement, William D. Lubitz, & Bahram Gharabaghi Introduction

Background Objective

Methodology

Experimental

Results and Discussion

Mean Quantities Turbulence Statistics Scaling Analysis

Conclusions Future Work Acknowledgements References

Results and Discussion

Turbulence Statistics

Figure: Turbulence exchanges can be defined in three directions: vertical, cross canyon, and along canyon [Aliabadi et al., 2018]

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Complete Characterization of Turbulence in an Urban Canyon Under All Wind Directions, Wind Speeds, and Thermal Stability Conditions Amir A. Aliabadi, Mohsen Moradi, Denis Clement, William D. Lubitz, & Bahram Gharabaghi Introduction

Background Objective

Methodology

Experimental

Results and Discussion

Mean Quantities Turbulence Statistics Scaling Analysis

Conclusions Future Work Acknowledgements References

Results and Discussion

Turbulence Statistics

Roof Street

Figure: Hourly variance of temperature t2 (a, b), and turbulence kinetic energy (TKE) k (c, d), classified based on the roof wind angle and the building Reynolds number ReH = (U

2+V 2)1/2H

ν

= SH

ν

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Complete Characterization of Turbulence in an Urban Canyon Under All Wind Directions, Wind Speeds, and Thermal Stability Conditions Amir A. Aliabadi, Mohsen Moradi, Denis Clement, William D. Lubitz, & Bahram Gharabaghi Introduction

Background Objective

Methodology

Experimental

Results and Discussion

Mean Quantities Turbulence Statistics Scaling Analysis

Conclusions Future Work Acknowledgements References

Results and Discussion

Turbulence Statistics

Roof Street

Figure: Hourly horizontal turbulent heat fluxes ut (a, b) and vt (c, d), classified based on the roof wind angle and the building Reynolds number ReH

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Complete Characterization of Turbulence in an Urban Canyon Under All Wind Directions, Wind Speeds, and Thermal Stability Conditions Amir A. Aliabadi, Mohsen Moradi, Denis Clement, William D. Lubitz, & Bahram Gharabaghi Introduction

Background Objective

Methodology

Experimental

Results and Discussion

Mean Quantities Turbulence Statistics Scaling Analysis

Conclusions Future Work Acknowledgements References

Results and Discussion

Turbulence Statistics

Roof Street

Figure: Continued; hourly vertical turbulent heat fluxes wt (e, f), classified based on the roof wind angle and the building Reynolds number ReH

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Complete Characterization of Turbulence in an Urban Canyon Under All Wind Directions, Wind Speeds, and Thermal Stability Conditions Amir A. Aliabadi, Mohsen Moradi, Denis Clement, William D. Lubitz, & Bahram Gharabaghi Introduction

Background Objective

Methodology

Experimental

Results and Discussion

Mean Quantities Turbulence Statistics Scaling Analysis

Conclusions Future Work Acknowledgements References

Results and Discussion

Turbulence Statistics

Roof Street

Figure: Hourly variance of temperature t2 (a, b), and turbulence kinetic energy (TKE) k (c, d), classified based on the roof wind angle and the bulk Richardson number Rib =

gH (UR−US)2+(V R−V S)2 T R−T S T A

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Complete Characterization of Turbulence in an Urban Canyon Under All Wind Directions, Wind Speeds, and Thermal Stability Conditions Amir A. Aliabadi, Mohsen Moradi, Denis Clement, William D. Lubitz, & Bahram Gharabaghi Introduction

Background Objective

Methodology

Experimental

Results and Discussion

Mean Quantities Turbulence Statistics Scaling Analysis

Conclusions Future Work Acknowledgements References

Results and Discussion

Turbulence Statistics

Roof Street

Figure: Hourly horizontal turbulent heat fluxes ut (a, b) and vt (c, d), classified based on the roof wind angle and the bulk Richardson number Rib

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Complete Characterization of Turbulence in an Urban Canyon Under All Wind Directions, Wind Speeds, and Thermal Stability Conditions Amir A. Aliabadi, Mohsen Moradi, Denis Clement, William D. Lubitz, & Bahram Gharabaghi Introduction

Background Objective

Methodology

Experimental

Results and Discussion

Mean Quantities Turbulence Statistics Scaling Analysis

Conclusions Future Work Acknowledgements References

Results and Discussion

Turbulence Statistics

Roof Street

Figure: Continued; hourly vertical turbulent heat fluxes wt (e, f), classified based on the roof wind angle and the bulk Richardson number Rib

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Complete Characterization of Turbulence in an Urban Canyon Under All Wind Directions, Wind Speeds, and Thermal Stability Conditions Amir A. Aliabadi, Mohsen Moradi, Denis Clement, William D. Lubitz, & Bahram Gharabaghi Introduction

Background Objective

Methodology

Experimental

Results and Discussion

Mean Quantities Turbulence Statistics Scaling Analysis

Conclusions Future Work Acknowledgements References

Results and Discussion

Turbulence Statistics

Figure: Hourly symmetric autocorrelations RUU (a), RVV (b), RWW (c), and RTT (d), classified based on the roof wind angle and diurnal time; E.g. autocorrelation definition for U component

• f velocity: RUU(r, x) = u(x + r, τ)u(x, τ) [Aliabadi, 2018]

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Complete Characterization of Turbulence in an Urban Canyon Under All Wind Directions, Wind Speeds, and Thermal Stability Conditions Amir A. Aliabadi, Mohsen Moradi, Denis Clement, William D. Lubitz, & Bahram Gharabaghi Introduction

Background Objective

Methodology

Experimental

Results and Discussion

Mean Quantities Turbulence Statistics Scaling Analysis

Conclusions Future Work Acknowledgements References

Results and Discussion

Scaling Analysis

Table: Scaling of Reynolds stresses; subscripts R and S signify roof and street, respectively; constants of the linear regression y = ax + b with correlation coefficient r are shown for each fit, where y is the scaled variable and x is the scaling variable. For each scaled variable, the scaling variables are ranked from highest r to lowest r. High correlations identified using a box |r| > 0.4 .

• Var. 1
• Var. 2
• Var. 3

a b r a b r a b r kR S2

G

u2

∗R

uvR 0.09

• 0.02

0.46 0.01 0.01 0.43 0.35 0.02 0.25 kS u2

∗S

S2

S

uvS 0.01 0.01 0.13 0.01 0.01 0.09 0.02 0.00 0.08 u2

∗R

kR S2

G

uwR 0.46

• 0.01

0.52 0.06

• 0.01

0.48 0.01 0.01 0.35 u2

∗S

kS S2

S

uwS

• 0.99

0.03

• 0.99
• 0.76

0.25

• 0.98
• 2.59

1.28

• 0.89

u2

∗R

S2

G

kR vwR

• 0.68

0.02

• 0.70
• 0.01
• 0.01
• 0.67
• 0.09

0.02

• 0.65

kS u2

∗S

S2

S

vwS 0.01 0.01 0.14 0.01 0.02 0.12 0.03 0.00 0.11 19 / 27

Complete Characterization of Turbulence in an Urban Canyon Under All Wind Directions, Wind Speeds, and Thermal Stability Conditions Amir A. Aliabadi, Mohsen Moradi, Denis Clement, William D. Lubitz, & Bahram Gharabaghi Introduction

Background Objective

Methodology

Experimental

Results and Discussion

Mean Quantities Turbulence Statistics Scaling Analysis

Conclusions Future Work Acknowledgements References

Results and Discussion

Scaling Analysis

Table: Scaling of turbulent kinematic heat fluxes; subscripts R and S signify roof and street, respectively; T SR signifies roof surface temperature, and T SC signifies canyon surface temperature averaged over canyon walls and street. High correlations identified using a box |r| > 0.4 .

• Var. 1
• Var. 2
• Var. 3

a b r a b r a b r SG (T SR − T R ) u∗R (T SR − T R ) SR (T SR − T R ) utR 0.00 0.01 0.04 0.01 0.01 0.03 0.00 0.00 0.00 u∗S (T SC − T S ) SS (T SC − T S ) SG (T SC − T S ) utS 1.17 0.56 0.63 1.47 0.43 0.53 0.25 0.72 0.20 SG (T SR − T R ) u∗R (T SR − T R ) SR (T SR − T R ) vtR

• 0.01
• 0.02
• 0.11
• 0.01
• 0.03
• 0.08
• 0.01

0.03

• 0.05

u∗S (T SC − T S ) SS (T SC − T S ) SG (T SC − T S ) vtS

• 0.01

0.04

• 0.20
• 0.01

0.04

• 0.02
• 0.01

0.04

• 0.02

u∗R (T SR − T R ) SR (T SR − T R ) SG (T SR − T R ) wtR 0.02 0.03 0.41 0.01 0.03 0.41 0.01 0.03 0.38 u∗S (T SC − T S ) SS (T SC − T S ) SG (T SC − T S ) wtS

• 0.78
• 0.37
• 0.62
• 0.97
• 0.28
• 0.52
• 0.16
• 0.48
• 0.20

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Complete Characterization of Turbulence in an Urban Canyon Under All Wind Directions, Wind Speeds, and Thermal Stability Conditions Amir A. Aliabadi, Mohsen Moradi, Denis Clement, William D. Lubitz, & Bahram Gharabaghi Introduction

Background Objective

Methodology

Experimental

Results and Discussion

Mean Quantities Turbulence Statistics Scaling Analysis

Conclusions Future Work Acknowledgements References

Conclusions

◮ Urban Heat Island (UHI) in Guelph is by a factor of 3-4

lower than Metropolitan Cities, e.g. London, U.K.

◮ Turbulent fluxes of momentum and heat are non-zero in

the horizontal directions and are comparable to those in the vertical direction.

◮ In the vertical direction turbulence statistics

◮ are governed by local conditions. ◮ are governed by short integral lengthscale and short

integral timescale.

◮ scale well with other flow parameters.

◮ In the horizontal directions turbulence statistics

◮ are governed by non-local conditions, particularly along

the canyon.

◮ are governed by large integral lengthscale and long

integral timescale.

◮ do not scale well with other flow parameters,

particularly along the canyon.

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Complete Characterization of Turbulence in an Urban Canyon Under All Wind Directions, Wind Speeds, and Thermal Stability Conditions Amir A. Aliabadi, Mohsen Moradi, Denis Clement, William D. Lubitz, & Bahram Gharabaghi Introduction

Background Objective

Methodology

Experimental

Results and Discussion

Mean Quantities Turbulence Statistics Scaling Analysis

Conclusions Future Work Acknowledgements References

Future Work

◮ Measure the turbulent flux gradients in the horizontal

and vertical directions.

◮ Perform an energy budget analysis to determine relative

magnitudes of mean versus turbulent transport mechanisms.

◮ Measure a regional temperature distribution in the order

• f a kilometer to better quantify horizontal transport of

heat.

◮ Measure vertical profiles of temperature, momentum,

and relative humidity more actively.

◮ Use observations to develop and validate both low and

high fidelity urban climate models.

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Complete Characterization of Turbulence in an Urban Canyon Under All Wind Directions, Wind Speeds, and Thermal Stability Conditions Amir A. Aliabadi, Mohsen Moradi, Denis Clement, William D. Lubitz, & Bahram Gharabaghi Introduction

Background Objective

Methodology

Experimental

Results and Discussion

Mean Quantities Turbulence Statistics Scaling Analysis

Conclusions Future Work Acknowledgements References

Future Work

Figure: Ultrasonic anemometers spread in three directions to measure flux gradients; TANAB reaching four times the canyon height

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Complete Characterization of Turbulence in an Urban Canyon Under All Wind Directions, Wind Speeds, and Thermal Stability Conditions Amir A. Aliabadi, Mohsen Moradi, Denis Clement, William D. Lubitz, & Bahram Gharabaghi Introduction

Background Objective

Methodology

Experimental

Results and Discussion

Mean Quantities Turbulence Statistics Scaling Analysis

Conclusions Future Work Acknowledgements References

Future Work

Figure: SOnic Detection And Randing (SODAR) instrument by Atmospheric Systems Corporations (ASC) to measure wind profiles at 10-m resolution up to 200 m altitude

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Complete Characterization of Turbulence in an Urban Canyon Under All Wind Directions, Wind Speeds, and Thermal Stability Conditions Amir A. Aliabadi, Mohsen Moradi, Denis Clement, William D. Lubitz, & Bahram Gharabaghi Introduction

Background Objective

Methodology

Experimental

Results and Discussion

Mean Quantities Turbulence Statistics Scaling Analysis

Conclusions Future Work Acknowledgements References

Acknowledgements

The authors thank Physical Resources staff members at the University of Guelph, in particular Steve Nyman and Chris Duiker, for assisting with the campaign logistics. The authors also thank Health and Safety staff members at the University of Guelph, in particular Manuela Racki and Jeffrey Dafoe, for assisting with safety inspections required to authorize the campaign. The authors appreciate the assistance of Joanne Ryks, Ryan Smith, and Stephen Stajkowski with the logistics of the field campaign.

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Complete Characterization of Turbulence in an Urban Canyon Under All Wind Directions, Wind Speeds, and Thermal Stability Conditions Amir A. Aliabadi, Mohsen Moradi, Denis Clement, William D. Lubitz, & Bahram Gharabaghi Introduction

Background Objective

Methodology

Experimental

Results and Discussion

Mean Quantities Turbulence Statistics Scaling Analysis

Conclusions Future Work Acknowledgements References

Acknowledgements

Financial support for this project was provided by the Undergraduate Research Awards (URA) program from the University of Guelph and the Discovery Grant program from Natural Sciences and Engineering Research Council (NSERC) of Canada (Grant No. 401231).

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Complete Characterization of Turbulence in an Urban Canyon Under All Wind Directions, Wind Speeds, and Thermal Stability Conditions Amir A. Aliabadi, Mohsen Moradi, Denis Clement, William D. Lubitz, & Bahram Gharabaghi Introduction

Background Objective

Methodology

Experimental

Results and Discussion

Mean Quantities Turbulence Statistics Scaling Analysis

Conclusions Future Work Acknowledgements References

References

Aliabadi, A. A. (2018). Theory and applications of turbulence: A fundamental approach for scientists and engineers. Amir A. Aliabadi Publications, Guelph, Ontario, Canada. Aliabadi, A. A., Moradi, M., Clement, D., Lubitz, W. D., and Gharabaghi, B. (2018). Flow and temperature dynamics in an urban canyon under a comprehensive set of wind directions, wind speeds, and thermal stability conditions.

• Environ. Fluid Mech.

Barlow, J. F., Halios, C. H., Lane, S. E., and Wood, C. R. (2015). Observations of urban boundary layer structure during a strong urban heat island event.

• Environ. Fluid Mech., 15(2):373–398.

Raupach, M. R., Thom, A. S., and Edwards, I. (1980). A wind-tunnel study of turbulent flow close to regularly arrayed rough surfaces. Boundary-Layer Meteorol., 18(4):373–397. 27 / 27