Quantified turbulent diffusion of suspended sediment using acoustic Doppler current profilers

• Published in: Geophysical research letters 2013-11, Vol.40 (21), p.5692-5697
• Main Authors: Sassi, M. G., F. Hoitink, A. J., Vermeulen, B.
• Format: Article
• Language: English
• Subjects: Acoustics; ADCP; boundary-layer; Diffusion; Diffusivity; Doppler effect; Eddies; Eddy diffusion; eddy viscosity; flow; Flow velocity; Fluid dynamics; fluxes; Freshwater; Meteorology; open channels; reynolds stress; Reynolds stress tensor; sand; Sediment concentration; sediment diffusivity; sediment transport; Sediments; Suspended sediments; suspension; Tidal rivers; transport; Turbulence; Turbulent flow
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2013GL058299

Collocated profiles of the Reynolds stress tensor and eddy covariance fluxes are obtained to derive vertical profiles of turbulent momentum and sediment diffusivity in a tidal river, using coupled acoustic Doppler current profilers (ADCPs). Shear and normal stresses are obtained by combining the variances in radial velocities measured by the ADCP beams. The covariances between radial velocities and calibrated acoustic backscatter allow the determination of the three Cartesian components of the turbulent flux of suspended sediment. The main advantage of this new approach is that flow velocity and sediment concentration measurements are exactly collocated, and allowing for profiling over longer ranges, in comparison to existing techniques. Results show that vertical profiles of the inverse turbulent Prandtl‐Schmidt number are coherent with corresponding profiles of the sediment diffusivity, rather than with profiles of the eddy viscosity. Key Points A new way to monitor eddy diffusivity of suspended river sediment is introduced Sharp peaks observed in vertical profiles of the eddy diffusivity Profiles of turbulent Prandtl-Schmidt number coherent with eddy diffusivity