Interactions of a Human Body with Parallel Angled Vanes Used to Improve Public Safety at a Low-Head Dam
The flow below low-head dams and weirs presents a significant public safety risk due to the formation of a submerged hydraulic jump that creates a dangerous recirculating flow or "roller”. Numerous safety incidents have been documented over the last several decades that have led to the development of guidelines for public safety at low-head dams, which encourage non-structural and structural modifications to the structures to improve safety. As a result, various structural modifications have been explored to mitigate these dangers. Recent studies at the University of Saskatchewan showed that angled parallel submerged vanes might improve public safety by eliminating the submerged hydraulic jump and creating a flow that carries a body entering that flow laterally toward the channel bank, thus improving the chance of rescue. In this work, the potential interactions between persons carried by the flow and the vanes were assessed, and mitigative measures were developed for interactions that appear to have a more significant chance of creating injury. This study followed an experimental approach, utilizing the same apparatus as Wilson (2022), to investigate potential body-vane interactions with a more realistic, scaled test body in terms of body density, segment size, mass distribution, lung volume, and body fat based on available biomechanics data. The experiments were conducted in a controlled flume environment, with scaled models of a human body designed based on the biomechanics literature. The test bodies were 3D-printed with segment-specific densities and flexible joints to simulate realistic movements. The experimental program was divided into four series. The first series repeated prior experiments by Wilson (2022) to observe body-vane interactions using a more realistic test body. In the second series, potential interaction types were categorized under various flow conditions. The third series tested the repeatability of these interactions through repeated trials, while the fourth focused on testing modifications aimed at reducing the most dangerous interactions. The results from the first series showed that vane interactions differed from previous studies when using a more realistic test body, indicating that factors such as body density and flexibility significantly influence outcomes. In the second series seven body-vane interaction types were identified: Type 1 – the nappe flow over the weir pushing the body onto the top of a vane; Type 2 – the flow pushing the body into the pressure side of a vane; Type 3 – the flow pushing the body into the suction side of a vane; Type 4 – the body hitting and or getting caught on the leading edge of a vane; Type 5 – brushing the top of a vane; Type 6 – brushing the pressure side of a vane; and Type 7 – brushing the suction side of a vane. Four of these seven body-vane interactions (Types 1-4) were deemed potentially hazardous due to more intense contact with the vanes. The remaining interaction types (Types 5-7) were a brushing action and were not considered particularly hazardous. In the third series, repeatability tests showed that despite maintaining constant flow conditions, interaction types varied across trials, suggesting a strong influence of turbulent flow on body paths and interaction types. However, some trends were discerned on how factors such as flow conditions and vane angle affect body-vane interactions. Finally, in the fourth series, modifications were used to minimize the most hazardous interactions. A combination of nappe disruptors and extended vanes at a 20° angle showed the most success, significantly reducing the most hazardous interactions while preserving the intended lateral flow toward the channel banks.
public safety at dams, public safety at low-head dams, dam safety, dam safety in Canada, submerged hydraulic jump, drowning machine, retrofit to low-head dams, scaled human model, vanes below weir, submerged parallel vanes, modifications to mitigate the dangers of submerged hydraulic jump, use of scaled human model in hydraulic engineering, use of scaled human model in hydraulic modelling, repeatability testing in hydraulic modelling
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