Mean vertical velocity profiles from aDcp river discharge measurement datasets

Experimental vertical velocity profiles were extracted from 18 series of aDcp discharge measurements. The campaigns were performed in the Saône river at the CNR Saint-Georges gauging station in Lyon, France. Post-processing methods for aDcp data positioning, averaging and depth-integrating have been implemented and applied to the dataset to get 23 mean velocity profiles across the 100 m-wide section. Individual fitting by a logarithmic law gives a satisfactory representation of the profiles and depth-integrated velocities very close to the experimental ones (errors are typically less than 1%). However velocities near the free-surface are overestimated. The 414 non-dimensional profiles can be represented accurately by a unit log profile except near the surface. Indeed the site-specific surface velocity coefficient is estimated to be 0.91 ±0.04 instead of the unit log value (0.88) or even the usual default value (0.85). Fitting wake-law profile coefficients allows to reproduce the near surface velocities better. Such an analysis of site-specific vertical velocity profiles is especially useful for discharge estimate methods based on an incomplete investigation of the flow field (H-aDcp, LS-PIV, radar wave scattering, etc.).