Characterizing Flow Patterns and Velocities in a Backwater Valve Using Fluorescent Particle Tracers for Image Velocimetry
Publication: Journal of Hydraulic Engineering
Volume 150, Issue 6
Abstract
Flooding in urban communities is an increasingly prevalent issue that causes significant financial loss, property damage, and long-term adverse health effects. Backwater valves can reduce the risk of basement flooding during sewer surcharge events at the lot-level scale. However, guidelines for installation and maintenance can be limited or inconsistent, with little underlying literature or research. Without proper installation and ongoing maintenance, solids can accumulate, resulting in the valve failing to close or being unable to form a watertight seal during a sewer surcharge event. This research provides insights to inform future design iterations or updates to best practices guidelines by characterizing flow patterns and velocities within the Mainline Fullport backwater valve. A series of laboratory experiments are described at two common flow rates (0.1 and ) and various slopes (, 0%, 2%, 5%, and 10%) using fluorescent particle tracers as a novel replacement for more traditional laser-based particle image velocimetry. Results revealed a complex flow environment influenced by slope, flow rate, initial water level conditions, and the fluid properties of water. Regions for potential solids accumulation leading to mechanisms of potential failure occurred near the inlet, at the downstream edge of the closing gate, and along the side channels. Increased slopes generally improved flow conditions, with least favorable outcomes below a 2% slope and diminishing returns above a 5% slope. Between 2% and 5% slope, conditions were the most complex but improved with increased flow rates. Fluorescent particle velocimetry shows promise as a powerful, affordable, and reliable tool to visualize flow and measure velocities in complex, shallow flow environments where other methods are unsuitable.
Practical Applications
Floods are an increasingly common and highly damaging problem, during which wastewater can back up in sewage pipes into basements. A backwater valve reduces the risk of sewer back-up and basement flooding. The valve closes when sewage flows backward and seals shut until the event ends. A backwater valve must be properly installed and maintained to ensure intended performance, but the associated guidelines can be unclear. To help improve those guidelines, this paper clarifies performance for various flow patterns and slopes in a backwater valve at different flow rates using laboratory experiments. Faster-moving water flushes debris and helps keep the valve clean, but raising slopes to achieve that may be difficult or expensive. Experiments used particles glowing under a black light to visualize water movement. Results reveal complicated flow patterns, with the worst conditions for flushing debris developing below 2% slope (2-cm drop per 100-cm of length) and the best conditions at 5% or above. Between 2% and 5% slope, the benefits of increasing slope were complex and depended on other factors. Methods used in these experiments can be adapted for different applications because they are relatively inexpensive and can work in shallow-water environments.
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Data Availability Statement
Some or all data, models, or code that support the findings of this study are available from the corresponding author upon reasonable request. For animated GIFs illustrating flow patterns, refer to Nguyen et al. (2024). Data files are named according to the slope used, flow rate (), and the trial number, as well as a label for the best trials used in the PIV and OpenCV flow velocity analyses.
Acknowledgments
The authors are grateful to the Institute for Catastrophic Loss Reduction (ICLR) and the Natural Sciences and Engineering Research Council of Canada (NSERC) (Grant #053309) for providing the support and funding for this research. The authors thank the Machine Shop staff in the School of Engineering at the University of Guelph for their technical support in building the laboratory setup. Many thanks also to the students who assisted with the laboratory experiments presented in this work: Julia Leith, Bryden Bray, and Emily Aitken.
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© 2024 American Society of Civil Engineers.
History
Received: Feb 17, 2023
Accepted: Apr 12, 2024
Published online: Jul 27, 2024
Published in print: Nov 1, 2024
Discussion open until: Dec 27, 2024
ASCE Technical Topics:
- Aerodynamics
- Aerospace engineering
- Backwater
- Computational fluid dynamics technique
- Continuum mechanics
- Dynamics (solid mechanics)
- Engineering fundamentals
- Engineering materials (by type)
- Engineering mechanics
- Equipment and machinery
- Flow (fluid dynamics)
- Fluid dynamics
- Fluid mechanics
- Fluid velocity
- Geomechanics
- Geotechnical engineering
- Hydraulic engineering
- Hydrologic engineering
- Materials engineering
- Motion (dynamics)
- Particle velocity
- Particles
- Slopes
- Solid mechanics
- Valves
- Water (by type)
- Water and water resources
- Water management
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