River discharge measurement by surface imaging of the velocity field (E. Barthélemy)
Measuring the flow of a river has important applications: flood forecasting, water quality, hydroelectric potential... Exploring the velocity field remains the most effective approach to obtain the flow at a given section. Acoustic instruments such as surface aDcp to measure a set of vertical velocity profiles. « Blind » areas, a few tens of centimetres, in the near field and at the bottom of the river are one of the disadvantages. Since De Prony (1804) and his idea of index velocity, engineers have tried to avoid measuring the entire profile using a priori assumptions on these profiles.
Information entropy theory is used to approximate velocity fields (C.-L. Chiu, 1987). It completely describes the vertical velocity profile with 2 constants. It allows both to extrapolate into blind areas and to merge with data collecteded by other instruments such as surface measurements of velocity fields obtained by PTV type processing of video images. As part of the Nour Chahrour Master’s degree and in collaboration with TENEVIA consultancy, we have developed a method to estimate the discharge based only on surface velocity fields. The method requires a preliminary calibration of the constants of the theory of information entropy through simultaneous measurements aDcp and surface velocity fields.
(E. Barthélemy)