Investigation of Improved Energy Dissipation in Stepped Spillways Applyinga Bubble Image Velocimetry

Abstract

This study focuses on the skimming flow regime, two-phase air-water flow conditions, and simple measures for improving energy dissipation, and aims to optimize the design, operation, and modeling of stepped spillways. The experiments were carried out at the Norwegian Hydraulic Laboratory at the Norwegian University of Science and Technology in Trondheim. Velocity field measurements were made in two physical models of different scales, conducted in two different rectangular flumes. For the first scenario, a 1:50 scale spillway model was used, and for the second, a larger model, 1:17 scale was built with planks and marine plywood with a crest of extruded polystyrene (XPS). Crest splitters were installed to further increase energy dissipation, and the hydraulic jump method was applied to measure the residual energy level. Flow properties were investigated the flow properties with the Bubble Image Velocimetry (BIV) technique, which tracks air bubbles. Experimental results show that BIV is remarkably successful for studying turbulent two-phase air-water flow. Additionally, two experiments were carried out with and without splitters on the ogee crest with ADV, revealing how the splitters changed the velocity profile above the crest. The study found crest splitters to be a practical and cost-effective measure to improve energy dissipation, in addition to reducing the length of inception and cavitation potential.