Author(s): Hubert Chanson

Linked Author(s): Hubert Chanson

Keywords: Hydraulic structures Half-round circular weirs Nappe instabilities Ventilation Splitters Physical modelling

Abstract: In the last decade, a couple of physical studies highlighted the occurrence of instabilities and non-linear rating rating curve with half-round circular crested weirs, in absence of ventilation. The author conducted a series of physical measurements with half-round circular-crested weirs. Nappe ventilation was provided with various sidewall splitter arrangements. The rectangular splitters induced some flow separation and provided the necessary space for the ventilation of the overflowing nappe with the formation of a stable air cavity underneath. A systematic quantitative comparison between un-ventilated and ventilated circular weirs showed little hysteresis and no overflow instability in presence of ventilation by sidewall splitters. The relationship between water discharge and head above crest was very stable. For the smallest splitter geometry, the air cavity disappeared at large discharges. With the other splitters, the results were qualitatively and quantitatively very close, hinting no effect of the relative splitter size and transverse spacing, within the experimental configurations tested herein.

DOI:

Year: 2025