Predicting the roughness length of turbulent flows over landscapes with multi-scale microtopography
AffiliationUniv Arizona, Dept Geosci, Gould Simpson Bldg
MetadataShow full item record
PublisherCOPERNICUS GESELLSCHAFT MBH
CitationPredicting the roughness length of turbulent flows over landscapes with multi-scale microtopography 2016, 4 (2):391 Earth Surface Dynamics
JournalEarth Surface Dynamics
Rights© Author(s) 2016. This work is distributed under the Creative Commons Attribution 3.0 License.
Collection InformationThis 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 firstname.lastname@example.org.
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, 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.
NoteOpen Access Journal
VersionFinal published version
SponsorsArmy Research Office [W911NF-15-1-0002]