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Acoustic observations of near‐bed sediment concentration and flux statistics above migrating sand dunes
Author(s) -
Wilson G. W.,
Hay A. E.
Publication year - 2016
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2016gl069579
Subject(s) - sediment , geology , mass flux , flux (metallurgy) , sediment transport , acoustic doppler current profiler , bed load , flow (mathematics) , geomorphology , mechanics , current (fluid) , physics , oceanography , materials science , metallurgy
A coherent Doppler profiler was used to measure coincident time series of velocity ( u , w ), sediment mass concentration ( c ), and sediment grain size ( d ), above mobile sand dunes in unidirectional flow (∼1 m/s, ∼1 m water depth). The measurements are used to extract statistical distributions of sediment concentration and flux just above the bed. Observed mass fluxes ( u c , w c ) were well fit by quasi‐exponential distributions, at all positions along the dune profile, similar to previous observations of single‐particle momenta for bed load over flat beds. Observed concentrations of moving particles were well fit by negative‐binomial distributions, also similar to previous observations over flat beds. These probability distributions relate to two recent stochastic theories, previously derived and verified for uniform flow over flat beds. It is hypothesized that these theories may also be used as a local approximation in natural‐scale flows with bed forms.