The University of Southampton
University of Southampton Institutional Repository

Thermal stratification effects on turbulence and dispersion in internal and external boundary layers

Thermal stratification effects on turbulence and dispersion in internal and external boundary layers
Thermal stratification effects on turbulence and dispersion in internal and external boundary layers
A synthetic turbulence and temperature fluctuation generation method embedded in large-eddy simulations (LES) was developed to investigate the effects of weakly stable stratification (i.e. with Richardson number $Ri\leq1$) on turbulence and dispersion following a rural-to-urban transition region. The work was based on firstly validating predictions of mean velocity, turbulent stresses, and point-source dispersion against wind-tunnel experiments of a stable boundary layer approaching a regular array of uniform cuboid elements at $Ri=0.21$. The depth of the internal boundary layer (IBL) formed at the leading edge of the uniform array was determined using the method which we have previously proposed. Vertical profiles of wall-normal turbulent stress showed that the height and the growth rate of the IBL were sensitive to the thermal stability prescribed at the inlet. We found that the IBL height was reduced when the inflow turbulence kinetic energy ($TKE$) was reduced while maintaining the same stratification condition. Lastly, scalar fluxes and mean concentrations within and above the canopy from a ground-level line source were simulated and analyzed. It was found that increasing the stable stratification level reduced the vertical transport of the pollutant, which increased the volume-averaged concentration within the canopy. For a given level of stable stratification, the effect on the total scalar fluxes within and above the canopy, and on the volume-averaged mean concentration within the lateral streets is more pronounced when the $TKE$ is reduced.
IBL, dispersion, inflow turbulence, stable stratification
0006-8314
61-83
Sessa, Vincenzo
93db2e6d-48cb-4825-ad38-fc77f1e069a2
Xie, Zheng-Tong
98ced75d-5617-4c2d-b20f-7038c54f4ff0
Herring, Steven
15f891b4-1a9e-4ac8-af74-ce4158274451
Sessa, Vincenzo
93db2e6d-48cb-4825-ad38-fc77f1e069a2
Xie, Zheng-Tong
98ced75d-5617-4c2d-b20f-7038c54f4ff0
Herring, Steven
15f891b4-1a9e-4ac8-af74-ce4158274451

Sessa, Vincenzo, Xie, Zheng-Tong and Herring, Steven (2020) Thermal stratification effects on turbulence and dispersion in internal and external boundary layers. Boundary-Layer Meteorology, 176 (1), 61-83. (doi:10.1007/s10546-020-00524-x).

Record type: Article

Abstract

A synthetic turbulence and temperature fluctuation generation method embedded in large-eddy simulations (LES) was developed to investigate the effects of weakly stable stratification (i.e. with Richardson number $Ri\leq1$) on turbulence and dispersion following a rural-to-urban transition region. The work was based on firstly validating predictions of mean velocity, turbulent stresses, and point-source dispersion against wind-tunnel experiments of a stable boundary layer approaching a regular array of uniform cuboid elements at $Ri=0.21$. The depth of the internal boundary layer (IBL) formed at the leading edge of the uniform array was determined using the method which we have previously proposed. Vertical profiles of wall-normal turbulent stress showed that the height and the growth rate of the IBL were sensitive to the thermal stability prescribed at the inlet. We found that the IBL height was reduced when the inflow turbulence kinetic energy ($TKE$) was reduced while maintaining the same stratification condition. Lastly, scalar fluxes and mean concentrations within and above the canopy from a ground-level line source were simulated and analyzed. It was found that increasing the stable stratification level reduced the vertical transport of the pollutant, which increased the volume-averaged concentration within the canopy. For a given level of stable stratification, the effect on the total scalar fluxes within and above the canopy, and on the volume-averaged mean concentration within the lateral streets is more pronounced when the $TKE$ is reduced.

Text
blm2019 - Author's Original
Download (2MB)

More information

Submitted date: 12 August 2019
Accepted/In Press date: 13 April 2020
Published date: 22 May 2020
Keywords: IBL, dispersion, inflow turbulence, stable stratification

Identifiers

Local EPrints ID: 436815
URI: http://eprints.soton.ac.uk/id/eprint/436815
ISSN: 0006-8314
PURE UUID: 2bbceef1-a83f-479a-b695-97279d4ae486
ORCID for Zheng-Tong Xie: ORCID iD orcid.org/0000-0002-8119-7532

Catalogue record

Date deposited: 10 Jan 2020 17:31
Last modified: 28 Apr 2022 01:53

Export record

Altmetrics

Contributors

Author: Vincenzo Sessa
Author: Zheng-Tong Xie ORCID iD
Author: Steven Herring

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×