Characterization of the mean flow and the turbulence structure of a large river with bed – Dunes using an ADCP

LÓPEZ, F. M.; GARCÍA, C.M.

Seatle. USA.

Conferencia; International Water Resources Engineering Conference.; 1999

American Society of Civil Engineering (ASCE)

The use of Acoustic Current Doppler Profilers (ADCP) in hydrometry defines a new era in riverflow measurements, not only due to its simplicity and relatively low cost, but mainly because itallows for the temporal and spatial resolution of the flow field, thus providing information that isimpossible to obtain through conventional methods. In this way, several variables and flowcharacteristics in large rivers can be estimated that highly contribute to a better understanding offluvial dynamics and the associated transport processes. This work presents results of acomprehensive field work aimed at investigating the capability of an Acoustic Doppler CurrentProfiler (ADCP) to characterize both the mean flow and the turbulence structure of largestreams. Measurements were performed with static and with a moving boat at differentdisplacement speeds for testing the performance of the equipment under several configurations.Results show a large number of discharge measurements in the Paraná River, Argentina, rangingfrom 20 m3/s to 27,000 m3/s, corresponding to the last extraordinary flood of May 1998.Processing of the information allowed for the computation of vertical mean velocity profiles, andthus to estimate associated velocity and length scales, i.e. bed shear velocity and equivalentroughness, respectively, over large bedforms. The available velocity series also provided someinformation about the turbulence structure, e.g. turbulence intensities, which once normalizedwith the appropriate scale were compared against measurements by others in large rivers. Inparticular, the ratio between the longitudinal and the transverse standard deviations showed agood agreement with observations by others, both in natural streams and laboratory channels.Furthermore, our field observations are compared against laboratory measurements conducted in a 1:30 scale, Froudean model of the Paraná River. Results demonstrate the potential capability of this new technology to study the flow structure of large rivers and to characterize the associated transport processes.