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New Technology Boosts UT Water Research to Elite Level

Micah Wyssmann in the Hydraulics and Sedimentation Laboratory.

Micah Wyssmann in the Hydraulics and Sedimentation Laboratory with the PIV system.

UT Professor Thanos Papanicolaou is a well-known expert in water resources, river sedimentation, farm runoff, and many other water-related engineering disciplines, having earned the 2018 Einstein Award for his work.

As director of the Hydraulics and Sedimentation Laboratory at UT, Papanicolaou has helped position the university on the cutting edge of such research through various test beds and equipment, including two large water and sediment flumes complemented with high precision measurement tools.

Now, that precision has gotten many times better, thanks to the acquisition of an advanced Particle Image Velocimetry (PIV) system. This latest development is important enough that Papanicolaou now feels the lab is one of the top 10 in the country.

“With this new data from the PIV, we are able to resolve vortex structures like eddies that are generated and have a huge impact on sediment movement around structures, which, in turn, has a huge impact on the efficiency and turbine blades,” said Papanicolaou, UT’s Henry Goodrich Chair of Excellence.

This is the first time we can actually capture those and is one of the only systems where we can measure what’s happening with those eddies.”

—Thanos Papanicolaou

The PIV system is the latest technology for tracking flow particles, using a high frequency laser that can get 100 measurements per second, compared to other lasers that are about 10 times slower. As the laser gets transmitted through the water, it shoots down to illuminate the whole volume of the flow.

The flow is seeded with neutrally buoyant particles that look like white powder to the casual observer, but are really specially formulated glass spheres 10 microns (1/100th of a meter) in size. Wherever the flow goes, they go.

To measure that movement, the laser produces a strobe-like effect that deflects off the seed particles, scattering the light. Four with 12-million-pixel resolution look into the flume from different angles and work together with the laser to feed images directly into the computer.

As images are captured, they can track particle movement from one frame to the next, and by using a triangulation algorithm, it is possible to identify particles from multiple vantage points and locate them in 3D space.

“As they scatter the light, we can watch them with the cameras and then track exactly where they go,” said doctoral student Micah Wyssmann, whose research looks at particle flow around obstacles in mountain streams such as boulders. “The PIV system lets us characterize the flow in a whole volume.”

Knowing the fundamentals of how particles flow at the micron allows researchers to scale out to the bigger picture, impacting projects like bank protection structures, small head dam designs, and bridge supports.

For example, Papanicolaou is involved with a collaborative effort with Oak Ridge National Laboratory and the US Department of Energy to work on the new generation of low-head power dams to redesign them so as to better harvest energy.

With previous technology, the research team could get small glimpses inside the flow, but they couldn’t really see what was actually happening in detail. Now, with this new measurement capability, they can minimize errors in design by knowing critical infrastructure and measurements around a dam intake, improving sediment prediction by nearly 200 percent.

Since it holds promise in any area that studies the flow of particles, NASA, the National Cooperative Highway Research Program, and the US Army Corps of Engineers can all be aided by the technology.

Élan Young: