Skip to Content

Cardinal: Modeling a Power Plant Forebay

IIHR builds paired physical and numerical models for an Ohio power plant

Simulating Sediment

The IIHR Engineering Services team includes engineers, researchers, and skilled technicians.

The IIHR Engineering Services team includes engineers, researchers, and skilled technicians.

IIHR—Hydroscience & Engineering recently completed a multi-faceted research effort for American Electric Power (AEP) that includes a physical model of the Cardinal plant as well as computer simulations. The power plant draws cooling water from the Ohio River, but AEP has a sediment problem in the forebay area near the intakes. Every five years or so, the company must dredge the forebay to allow the water to flow in unimpeded — a costly proposition. AEP hired IIHR to model the site and test mitigation strategies to reduce the sediment problem.

In addition, a new U.S. Environmental Protection Agency rule requires companies that draw water from the river to protect fish, fish larvae, and other aquatic organisms. If the velocity of the intake water is too fast, fish larvae and other small creatures can be swept in, and bigger creatures can get stuck on the screens that cover the intakes. To comply with the rule, AEP asked IIHR to test new screen configurations in the forebay that meet the new velocity criteria.

A Model is Born

IIHR Director of Engineering Services Troy Lyons says that his team traveled to the site to collect bathymetry (riverbed topography) data needed to build the 1:24 scale model of the riverbed topography near the plant. While there, they also gathered velocity, sediment, temperature, and water-quality data.

Back in Iowa, the team used the information to build the Cardinal model in IIHR’s James Street facility. “We replicated everything exactly how it was in the field,” Lyons says.

IIHR completed a modeling project for American Electric Power that including this physical model of the Cardinal Power Plant on the Ohio River.

IIHR completed a modeling project for American Electric Power that including this physical model of the Cardinal Power Plant on the Ohio River.

They then used the model to test several options to try to slow the sediment deposition: vanes, walls, submerged walls, and more. Each test runs continuously for 12 hours. The team meticulously set the river flow rate, intake flows, and the amount of sediment to simulate what would occur in the plant’s forebay. At the end of each test, they used a laser scanner to produce a contour map of the surface. Lyons says they compared the new scans to those taken before the test. “By looking at the difference, we know exactly how much and where sediment was deposited, scoured, or changed,” he says.

IIHR is uniquely well prepared for this sort of project, Lyons says. “We have a lot of experience with structures in rivers and mitigating sediment, especially Jacob Odgaard, who has spent his entire career studying rivers.” The IIHR shop staff, led by Brandon Barquist, also has specialized expertise in precision model construction.

Computational modeling of the forebay of the Cardinal Power Plant.

Computational modeling of the forebay of the Cardinal Power Plant.

IIHR researcher Marcela Politano’s fully three-dimensional computer simulations (based on FLUENT, with several add-on functions Politano wrote herself) ran parallel to the physical testing at James Street. Each form of modeling offers strengths and limitations. For instance, it is impossible to scale the sediment particle size exactly in the physical model. “You can’t just scale a grain of sand 1:24,” Lyons says. “You’d end up with clay.” The team used ground-up acrylic material to simulate sediment, which Lyons says minimizes the scale effect. The physical model also allows researchers to study erosion and deposition of sediment, which can influence the flow patterns during the course of a test.

On the other hand, researchers can run computer simulations full-scale, using actual particle sizes and densities. But the current numerical model computer simulation doesn’t demonstrate erosion or deposition in the same way that physical model does.

“They’re both powerful tools,” Lyons says. “They can be used together, and there are ways to compare the data side by side. But you have to be very careful to understand the differences.”

Heating Up

One strength of the computer simulation is its ability to model temperature differences. “It turns out that was a very important factor that we didn’t see at the beginning of the project,” Lyons says. The team noticed a significant recirculation effect in the field data from the Ohio River. Water was leaving the plant and recirculating into the forebay, bringing with it water that was warmer than normal river water. Obviously, this was a problem.

Side-by-side images of the Cardinal Power Plant and IIHR's physical model of the plant.

Side-by-side images of the Cardinal Power Plant and IIHR’s physical model of the plant.

“Neither of our models predicted it,” Lyons says. “When we added a thermal component to the CFD model, all of a sudden, it matched! It was incredible.”

By simulating various options and integrating both models — computer and physical — the IIHR team was able to recommend two potential options to AEP. “It’s been a really fun project,” Lyons says. “Thinking through the process, doing the engineering, understanding the science behind it — it was fun.”

Politano agrees. She says that every time she takes on a new challenge, she finds herself deeply involved in the work. “It was the first time I worked with sediment in this way,” she says. “It is my new passion!”

Last modified on May 12th, 2017
Posted on May 9th, 2017

Site by Mark Root-Wiley of MRW Web Design