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Velocity profiles measured on the windward slope of a transverse dune
Author(s) -
Mulligan Kevin R.
Publication year - 1988
Publication title -
earth surface processes and landforms
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.294
H-Index - 127
eISSN - 1096-9837
pISSN - 0197-9337
DOI - 10.1002/esp.3290130703
Subject(s) - crest , geology , wind speed , turbulence , wind shear , acceleration , transverse plane , shear velocity , flow (mathematics) , flow velocity , wind gradient , geomorphology , atmospheric sciences , meteorology , mechanics , physics , oceanography , structural engineering , classical mechanics , quantum mechanics , engineering
Velocity gradients measured on the windward slope of a transverse dune show that flow acceleration strongly affects the turbulence structure of wind. Wind profiles measured below a height of 1.6m are nonlogarithmic and the altered nature of velocity profiles varies over the windward slope of a dune. These findings suggest that calculated values of shear velocity are largely dependent upon the height and location of wind speed measurements, as well as the strength of the prevailing wind. Moreover, if Bagnold‐type transport equations are used to calculate rates of sand transport on a dune, wind speeds must be measured within 0.2 m of the dune surface. If wind speeds are measured above this height, the resulting errors in calculated shear velocity will manifest themselves as errors in calculated rates of sand transport. If rates of sand transport are derived from wind speeds measured above 0.2 m the calculated rates may underestimate sand transport on the windward face of a dune as a result of flow acceleration. In contrast, if a dune has a separate crest upwind of the brink, the expansion and subsequent deceleration of flow downwind from the crest may result in an overestimation of sand transport.