Facilities
One basic approach to investigate mixing is the use of dye tracing. This usually consists of injecting a conservative dye into a system and monitoring its concentration.
Rhodamine dye is a tracer used commonly used at the University of Sheffield. This dye absorbs light at around 530 nm (green) and fluoresces at around 560 nm (yellow-green). This is detected by a fluorometer, which are calibrated to report concentrations. (Visit the Turner Designs website for more information on dye tracing and fluorometers.)
At the University, dye tracing has been used in various facilities.
Straight pipe
Currently, a long 24mm internal diameter pipe fitted with both fluorometers to measure dye concentrations and ultrasonic velocity profiling (UVP) probes to measure velocities. (Visit the Met-Flow website for more information on UVP probes.)
A laser has recently been fitted to measure cross-sectional variation in dye concentrations to investigate mixing in transitional flow.
Wide flume
The main water laboratory is equipped with a 1.2 m wide 15 m long flat flume currently fitted for mixing studies.
The flume has four full-width laser-line induced fluorescence dye concentration measurement stations as well as a full-width laser light sheet for measuring velocities through particle image velocimetry.
The flume is currently being used to investigate mixing in emergent vegetation.
Narrow flume
The narrow flume is a medium-scale Gunt teaching flume, 0.3 m wide and 12.5 m long.
It is primarily used by students as part of teaching exercises to help develop students' skills in conducting and analysing tracer experiments.
Most recently it has been used to investigate mixing around emergent vegetation.
Model manholes
Sheffield has several small-scale model manholes of varying diameter that can be fitted with upstream and downstream fluorometers for investigating the mixing caused within the manhole.
