Aerial observations of density-driven streamwise vortices at a confluence

Rivers of different density can develop impressive streamwise orientated vortices when they collide. Apart from being incredibly interesting, the vortices largely determine how quickly suspended sediments and pollutants mix downstream of the rivers’ confluence.

Multiphase bubble induced recirculation

Environmental multiphase flows allow lighter particles to remain in suspension whilst permitting heavier particles to settle. They are also important to aeration and mixing separated fluids. 3D numerical modelling of multiphase flows remains challenging and fully 3D validation studies are lacking. This project compared OpenFOAM’s twoPhaseEulerFoam to an extensive 3D dataset including stereoscopic particle image velocimetry and optical void fraction measurements.

OpenFOAM fishway modelling

Commercial licenses for 3D hydrodynamic models are exorbitantly expensive (100k$ + plus 20k$ annual fees). OpenFOAM, however, is free and open-sourced making it an attractive lower cost alternative. This study compared Flow-3D with OpenFOAM over a full-scale (100 m +) fishway in collaboration with a large hydroelectric provider in the province of Québec. OpenFOAM was equal to Flow3D, yet was much easier to scale on Compute Canada’s high-powered computational clusters making it much more attractive for industrial and academic workloads.

Sediment deposition and fish locomotion

Turbulence generated by flow over objects affects fish locomotion. For example, it can increase the difficultly a fish encounters navigating a baffled reach of a culvert (first video). Filling in the highly turbulent region downstream of the baffle results in drastic improvements of various fish passage metrics (second video). This study applied high-speed 3D position tracking and 3D stereoscopic particle image to understand how fish interact with turbulence caused by bed-mounted objects with implications for improving passage over smooth culverts.

How do baffles reduce hydraulic capacity of culverts?

Increasing bed roughness generally improves the ability of fish to traverse a culvert. However, adding roughness also reduces the hydraulic capacity of the culvert. Engineers must therefore balance fish passage requirements with the practical consideration of ensuring flood waters efficiently exit the culvert. This laboratory study investigated the effect of a wide variety of baffle arrangements, inlet conditions and loss of flow area due to sliplining on the fully pressurized hydraulic capacity of culverts.

Smooth culvert fish passage

Water flowing over a sloped smooth material rapidly accelerates to a high velocity. The practice of sliplining aging culverts with smooth plastic pipes can severely reduce a fish’s ability to traverse the culvert, leading to significant loss of spawning and feeding habitat upstream. This project, in collaboration with USGS, addressed this issue by studying the movements of trout as they navigated baffle arrays of increasing complexity. A key finding: ‘short’ and wide weir baffles can drastically improve passage metrics, with little affect on hydraulic roughness.

Fish ladder to address perched culverts

Scour downstream of culverts often causes a ‘perched’ outlet condition. In these cases, the outlet can be located anywhere between 10 cm to 300 cm above the downstream water surface level. This perching blocks upstream passage of even the strongest jumping fish species. In collaboration with industry and a provincial ministry, this project applied 3D numerical modelling to assist in the design of a low cost, lightweight, easily transportable fish ladder to address perched conditions in remote regions or anywhere for that matter.