Abstract
We present measurements of wind velocity and sand flux performed on the
windward side of a large barchan dune in Jericoacoara, northeastern
Brazil. From the measured profile, we calculate the air shear stress
using an analytical approximation and treat the problem of flow
separation by an heuristic model. We find that the results from this
approach agree well with our field data. Moreover, using the calculated
shear velocity, we predict the sand flux according to well-known
equilibrium relations and with a phenomenological continuum saltation
model that includes saturation transients and thus allows for
nonequilibrium conditions. Based on the field data and theoretical
predicted results, we indicate the principal differences between
saturated and nonsaturated sand flux models. Finally, we show that the
measured dune moves with invariant shape and predict its velocity from
our data and calculations. (C) 2003 Elsevier Science B.V. All rights
reserved.
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