Role of Wake Production on the Scaling Laws of Scalar Concentration Fluctuation Spectra Inside Dense Canopies

The scalar concentration fluctuations within a plane parallel-to-the-ground surface were measured inside a model canopy composed of densely arrayed rods using the laser-induced fluorescence technique. Two-dimensional scalar concentration spectra were computed and were shown to exhibit an approximate...

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Bibliographic Details
Published in:Boundary-layer meteorology 2011-04, Vol.139 (1), p.83-95
Main Authors: Poggi, D, Katul, G. G, Vidakovic, B
Format: Article
Language:English
Subjects:
Analysis
Atmospheric boundary layer
Atmospheric Protection/Air Quality Control/Air Pollution
Atmospheric Sciences
Canopies
Canopy turbulence
Computational fluid dynamics
Convection, turbulence, diffusion. Boundary layer structure and dynamics
Earth and Environmental Science
Earth Sciences
Earth, ocean, space
Exact sciences and technology
External geophysics
Fluctuation
Fluid dynamics
Fluorescence
Inertial
Invisibility
Laser-induced fluorescence technique
Meteorology
Relaxation time
Scalar concentration spectra
Scalars
Similarity
Spectra
Spectrum analysis
Turbulence
Wake production
Wakes
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Summary:The scalar concentration fluctuations within a plane parallel-to-the-ground surface were measured inside a model canopy composed of densely arrayed rods using the laser-induced fluorescence technique. Two-dimensional scalar concentration spectra were computed and were shown to exhibit an approximate −3 power-law scaling at wavenumbers larger than those associated with wake production during quiescent instances when von Karman vortex streets dominated the flow. However, during instances when sweeps disrupted the flow, the spectral exponents increased above −3. The −3 power-law for these concentration fluctuation spectra measurements was shown to be consistent with a simplified spectral budget for locally homogeneous and isotropic turbulence augmented with a relaxation time scale similarity argument that assumed a constant enstrophy injection rate and wake generation mechanism. Hence, the origin of this −3 power-law scaling here differs from the well-known −3 power-law result for the so-called inertial diffusive range derived for the scalar concentration spectrum at small Prandtl numbers.
ISSN:0006-8314
1573-1472
DOI:10.1007/s10546-010-9573-1