Author(s): D. Wuthrich; R. Shi; H. Wang; H. Chanson
Keywords: Hydraulic jump; Energy dissipation; Air-water flow properties; Sidewall effects; Physical modelling; Hydraulic structures
Abstract: Hydraulic jumps are commonly employed as energy dissipators to guarantee long-term operation of hydraulic structures. Thus, a comprehensive and in-depth understanding of its main features is fundamental. In this context, the current study focused on a hydraulic jump with a low Froude number (Fr1=2.4) and a relatively high Reynolds number (Re=1.83×105). Experimental tests employed dual-tip phase-detection probes to provide a comprehensive characterisation of the main air-water flow properties of the hydraulic jump in terms of void fraction, bubble count rate and interfacial velocities. Importantly, this research focused on the air-water flow property distribution across the channel width, revealing lower values of void fraction and bubble count rate next to the sidewall as compared to the channel centreline. Such a spatial variability in the transverse direction questions whether data near the walls may be representative of the flow behaviour in the centreline, raising the issue of sidewall effects in image-based techniques. These findings provide helpful information to both researchers and practitioners for a better understanding of the physical process, leading to an optimised design of hydraulic structures.