Predicting the roughness length of turbulent flows over landscapes with multi-scale microtopography

Persistent Link:
http://hdl.handle.net/10150/618956
Title:
Predicting the roughness length of turbulent flows over landscapes with multi-scale microtopography
Author:
Pelletier, Jon D.; Field, Jason P.
Affiliation:
Univ Arizona, Dept Geosci, Gould Simpson Bldg
Issue Date:
2016-05-19
Publisher:
COPERNICUS GESELLSCHAFT MBH
Citation:
Predicting the roughness length of turbulent flows over landscapes with multi-scale microtopography 2016, 4 (2):391 Earth Surface Dynamics
Journal:
Earth Surface Dynamics
Rights:
© 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, <i>z</i><sub>0</sub>. Here we propose a predictive formula for <i>z</i><sub>0</sub> 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 <i>z</i><sub>0</sub> value of sinusoidal microtopography as a function of the amplitude and slope. The effective <i>z</i><sub>0</sub> 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 <i>z</i><sub>0</sub> values measured in  ∼ 10<sup>5</sup> wind-velocity profiles from southwestern US playa surfaces. Our equation is capable of predicting <i>z</i><sub>0</sub> 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 Journal
ISSN:
2196-632X
DOI:
10.5194/esurf-4-391-2016
Version:
Final published version
Sponsors:
Army Research Office [W911NF-15-1-0002]
Additional Links:
http://www.earth-surf-dynam.net/4/391/2016/

Full metadata record

DC FieldValue Language
dc.contributor.authorPelletier, Jon D.en
dc.contributor.authorField, Jason P.en
dc.date.accessioned2016-08-27T00:46:52Z-
dc.date.available2016-08-27T00:46:52Z-
dc.date.issued2016-05-19-
dc.identifier.citationPredicting the roughness length of turbulent flows over landscapes with multi-scale microtopography 2016, 4 (2):391 Earth Surface Dynamicsen
dc.identifier.issn2196-632X-
dc.identifier.doi10.5194/esurf-4-391-2016-
dc.identifier.urihttp://hdl.handle.net/10150/618956-
dc.description.abstractThe 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, <i>z</i><sub>0</sub>. Here we propose a predictive formula for <i>z</i><sub>0</sub> 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 <i>z</i><sub>0</sub> value of sinusoidal microtopography as a function of the amplitude and slope. The effective <i>z</i><sub>0</sub> 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 <i>z</i><sub>0</sub> values measured in  ∼ 10<sup>5</sup> wind-velocity profiles from southwestern US playa surfaces. Our equation is capable of predicting <i>z</i><sub>0</sub> 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.en
dc.description.sponsorshipArmy Research Office [W911NF-15-1-0002]en
dc.language.isoenen
dc.publisherCOPERNICUS GESELLSCHAFT MBHen
dc.relation.urlhttp://www.earth-surf-dynam.net/4/391/2016/en
dc.rights© Author(s) 2016. This work is distributed under the Creative Commons Attribution 3.0 License.en
dc.titlePredicting the roughness length of turbulent flows over landscapes with multi-scale microtopographyen
dc.typeArticleen
dc.contributor.departmentUniv Arizona, Dept Geosci, Gould Simpson Bldgen
dc.identifier.journalEarth Surface Dynamicsen
dc.description.noteOpen Access Journalen
dc.description.collectioninformationThis 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.en
dc.eprint.versionFinal published versionen
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