Influence of atmospheric stratification on the integral scale and fractal dimension of turbulent flows
In this work the relation between integral scale and fractal dimension and the type of stratification in fully developed turbulence is analyzed. The integral scale corresponds to that in which energy from larger scales is incoming into a turbulent regime. One of the aims of this study is the underst...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-11-01
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| Series: | Nonlinear Processes in Geophysics |
| Online Access: | http://www.nonlin-processes-geophys.net/23/407/2016/npg-23-407-2016.pdf |
| Summary: | In this work the relation between integral scale and
fractal dimension and the type of stratification in fully developed
turbulence is analyzed. The integral scale corresponds to that in which
energy from larger scales is incoming into a turbulent regime. One of the
aims of this study is the understanding of the relation between the integral
scale and the bulk Richardson number, which is one of the most widely used
indicators of stability close to the ground in atmospheric studies. This
parameter will allow us to verify the influence of the degree of
stratification over the integral scale of the turbulent flows in the
atmospheric boundary layer (ABL). The influence of the diurnal and night
cycles on the relationship between the fractal dimension and integral scale
is also analyzed. The fractal dimension of wind components is a turbulent
flow characteristic, as has been shown in previous works, where its relation
to stability was highlighted. Fractal dimension and integral scale of the
horizontal (<i>u</i>′) and vertical (<i>w</i>′) velocity fluctuations have been
calculated using the mean wind direction as a framework. The scales are
obtained using sonic anemometer data
from three elevations 5.8, 13 and 32 m above the ground measured during the
SABLES 98 field campaign (Cuxart et al., 2000). In order to estimate the integral scales, a method
that combines the normalized autocorrelation function and the best Gaussian
fit (<i>R</i><sup>2</sup> ≥ 0.70) has been developed. Finally, by comparing, at the
same height, the scales of <i>u</i>′ and <i>w</i>′ velocity components, it is found
that the turbulent flows are almost always anisotropic. |
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| ISSN: | 1023-5809 1607-7946 |