Predicting the roughness length of turbulent flows over landscapes with multi-scale microtopography
Affiliation
Univ Arizona, Dept Geosci, Gould Simpson BldgIssue Date
2016-05-19
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COPERNICUS GESELLSCHAFT MBHCitation
Predicting the roughness length of turbulent flows over landscapes with multi-scale microtopography 2016, 4 (2):391 Earth Surface DynamicsJournal
Earth Surface DynamicsRights
© Author(s) 2016. This work is distributed under the Creative Commons Attribution 3.0 License.Collection Information
This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.Abstract
The fully rough form of the law of the wall is commonly used to quantify velocity profiles and associated bed shear stresses in fluvial, aeolian, and coastal environments. A key parameter in this law is the roughness length, z0. Here we propose a predictive formula for z0 that uses the amplitude and slope of each wavelength of microtopography within a discrete-Fourier-transform-based approach. Computational fluid dynamics (CFD) modeling is used to quantify the effective z0 value of sinusoidal microtopography as a function of the amplitude and slope. The effective z0 value of landscapes with multi-scale roughness is then given by the sum of contributions from each Fourier mode of the microtopography. Predictions of the equation are tested against z0 values measured in ∼ 105 wind-velocity profiles from southwestern US playa surfaces. Our equation is capable of predicting z0 values to 50 % accuracy, on average, across a 4 order of magnitude range. We also use our results to provide an alternative formula that, while somewhat less accurate than the one obtained from a full multi-scale analysis, has an advantage of being simpler and easier to apply.Note
Open Access JournalISSN
2196-632XVersion
Final published versionSponsors
Army Research Office [W911NF-15-1-0002]Additional Links
http://www.earth-surf-dynam.net/4/391/2016/ae974a485f413a2113503eed53cd6c53
10.5194/esurf-4-391-2016
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Except where otherwise noted, this item's license is described as © Author(s) 2016. This work is distributed under the Creative Commons Attribution 3.0 License.