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First-order turbulence closure for modelling complex canopy flows

Finnigan, J., Harman, I., Ross, A. and Belcher, S. (2015) First-order turbulence closure for modelling complex canopy flows. Quarterly Journal of the Royal Meteorological Society, 141 (692). pp. 2907-2916. ISSN 1477-870X

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To link to this item DOI: 10.1002/qj.2577


Simple first-order closure remains an attractive way of formulating equations for complex canopy flows when the aim is to find analytic or simple numerical solutions to illustrate fundamental physical processes. Nevertheless, the limitations of such closures must be understood if the resulting models are to illuminate rather than mislead. We propose five conditions that first-order closures must satisfy then test two widely used closures against them. The first is the eddy diffusivity based on a mixing length. We discuss the origins of this approach, its use in simple canopy flows and extensions to more complex flows. We find that it satisfies most of the conditions and, because the reasons for its failures are well understood, it is a reliable methodology. The second is the velocity-squared closure that relates shear stress to the square of mean velocity. Again we discuss the origins of this closure and show that it is based on incorrect physical principles and fails to satisfy any of the five conditions in complex canopy flows; consequently its use can lead to actively misleading conclusions.

Item Type:Article
Divisions:Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
ID Code:57909
Publisher:Royal Meteorological Society


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