Author(s): Hubert Chanson
Linked Author(s): Hubert Chanson
Keywords: Circular crested weirs; Fluid-structure interactions; Hydrodynamic instabilities; Physical modelling; Air cavity transients
Abstract: Liquid overflowing over rounded weirs experiences a rapidly accelerating fluid flow region near the crest. Depending upon the discharge and radius of curvature, the overflow nappe may be attached or detached. Herein, careful physical modelling was conducted under carefully controlled conditions with a circular weir equipped with a relatively small radius of curvature. Based upon simple experiments across a very broad range of flow rates, the results highlighted a narrow range of hydrodynamic transient conditions for which both attached and detached nappe situations may co-exist. Cavity transients were observed as a result of nonlinear instabilities at both detachment and re-attachment. The transients were characterised by massive nonlinear instabilities, associated with very rapid change in hydrodynamic properties, and sometimes loud acoustics and impact on the weir structure. The hydrodynamic processes presented some form of hysteresis.