Potential of coastal armour units as energy dissipators to enhance the characteristics of hydraulic jumps

Abstract

Energy dissipating structures are strategically positioned at the base of dam spillways to prevent riverbed erosion and safeguard downstream infrastructures. The objective of this study is to experimentally explore the potential of a novel approach involving the use of coastal structures, known as armour units, as energy dissipators. Two armor unit models were designed using AutoCAD by adopting the geometry of a wave and tetrapod, and subsequently fabricated using a 3D printer with polyactic acid (PLA) material. Using a HM 160 Hydraulic Flume, experiments were performed by simulating discharge over short-crested weir, with a sloped spillway, and generating hydraulic jumps over the armour units that were installed downstream. Inflow conditions of the jumps ranged from a Froude value (Fr1) of 1.7 to 4.0. It was observed that both the wave and tripod structures induced a ski-jump effect before the hydraulic jump, which would facilitate the transportation of sediments and minimize scour risks in practical applications. Additionally, the energy dissipation level through the jumps had improved by four-fold as the height of the ski-jump doubled. Both structures also caused a significant reduction in sequent depth and length of the hydraulic jumps, up to 40% and 50%, respectively, as compared to the classical hydraulic jump formation on a smooth bed, which may lead to a more cost-effective basin design. Overall, the findings of this research highlights the possibility of utilizing a minimal number of units for adequate energy dissipation, offering significant advantages in scenarios where mitigating flood energy in open channels is required.