The Effect of Scale on the Applicability of Taylor’s Frozen Turbulence Hypothesis in the Atmospheric Boundary Layer |
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| Authors: | Chad W Higgins Martin Froidevaux Valentin Simeonov Nikki Vercauteren Caitlin Barry Marc B Parlange |
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| Institution: | 1.Department of Biological and Ecological Engineering,Oregon State University,Corvallis,USA;2.School of Architecture, Civil and Environmental Engineering,Ecole Polytechnique Federale de Lausanne,Lausanne,Switzerland |
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| Abstract: | Taylor’s frozen turbulence hypothesis is the central assumption invoked in most experiments designed to investigate turbulence
physics with time resolving sensors. It is also frequently used in theoretical discussions when linking Lagrangian to Eulerian
flow formalisms. In this work we seek to quantify the effectiveness of Taylor’s hypothesis on the field scale using water
vapour as a passive tracer. A horizontally orientated Raman lidar is used to capture the humidity field in space and time
above an agricultural region in Switzerland. High resolution wind speed and direction measurements are conducted simultaneously
allowing for a direct test of Taylor’s hypothesis at the field scale. Through a wavelet decomposition of the lidar humidity
measurements we show that the scale of turbulent motions has a strong influence on the applicability of Taylor’s hypothesis.
This dependency on scale is explained through the use of dimensional analysis. We identify a ‘persistency scale’ that can
be used to quantify the effectiveness of Taylor’s hypothesis, and present the accuracy of the hypothesis as a function of
this non-dimensional length scale. These results are further investigated and verified through the use of large-eddy simulations. |
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