Predictability of Turbulent Flow in Street Canyons

• Published in: Boundary-layer meteorology Vol. 156; no. 2; pp. 191 - 210
• Main Authors: Lo, K. W., Ngan, K.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.08.2015; Springer; Springer Nature B.V
• Subjects: Analysis; Atmospheric Protection/Air Quality Control/Air Pollution; Atmospheric Sciences; Boundaries; Canyons; Computational fluid dynamics; Earth and Environmental Science; Earth Sciences; Errors; Marine; Mathematical models; Meteorology; Modelling; Predictive control; Shear layers; Turbulence; Turbulent flow; urban areas; Predictability; Turbulence; Street canyons
• ISSN: 0006-8314; 1573-1472
• DOI: 10.1007/s10546-015-0014-z

Although predictability is a subject of great importance in atmospheric modelling, there has been little research on urban boundary-layer flows. Here the predictability of street-canyon flow is examined numerically via large-eddy simulation of a unit-aspect-ratio canyon and neutrally stratified atmosphere. In spectral space there is indication of cascade-like behaviour away from the canyon at early times, but the error growth is essentially independent of scale inside the canyon; in physical space the error field is rather inhomogeneous and shows clear differences among the canyon, shear layer and inertial sublayer. The error growth is largely driven by the shear layer: errors generated above roof level are advected into the canyon while contributions from intermittent bursting and in situ development within the canyon play a relatively minor role. This work highlights differences between the predictability of urban flows and canonical turbulent flows and should be useful in developing modelling strategies for more realistic time-dependent urban flows.