Predicting velocities and turbulent exchange in isolated street canyons and at a neighborhood scale

Urban planners need a fast, simple model to assess the impact of early design phase iterations of neighborhood layout on the microclimate. Specifically, this model should be able to predict the expected urban heat island intensity and the locations in neighborhood layouts that are prone to pollutant retention. Current models are inadequate for this purpose because they use computationally intensive techniques to solve for flow through a neighborhood and often require a strong technical background for effective use of the models. In this thesis, we use analytical equations and empirical relationships to calculate the expected wind speeds in isolated, idealized street canyons. We demonstrate that flow in street canyons is driven by momentum exchange with the air above. We discuss the importance of flow separation and turbulent exchange between the urban canopy layer and the urban boundary layer for removing heat and pollutants from street canyons. Next, we introduce a method to parameterize this exchange and extend this work to more realistic street canyons and idealized neighborhoods. We evaluate this work using computational fluid dynamics and comparison to experimental results and models from the literature. We examine cases where the flow is influenced by buoyancy effects and assess the applicability of our work in these situations. Finally, we address how this work could be further developed into generalized planning guidelines and incorporated into a comprehensive model for urban planners.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Mechanical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2010

Author dc:creator

• Hall, Terianne C

Advisor dc:contributor.advisor

• Leslie K. Norford.

• Mechanical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/61867

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/61867