Supercomputer Sims Illustrate Impact of Ocean Waves on Offshore Wind Turbine Efficiency

Published December 17, 2024

As shown in these Expanse simulations, mature waves (right) have longer wavelengths than newly formed waves (left). Credit: University of Puerto Rico at Mayaguez

By Kimberly Mann Bruch, SDSC Communications

Using the Expanse system at the San Diego Supercomputer Center (SDSC), part of the new School of Computing, Information and Data Sciences (SCIDS) at UC San Diego, University of Puerto Rico at Mayaguez Mechanical Engineering Professor Umberto Ciri has taken a deep dive into understanding how waves affect offshore wind turbines. Applying a powerful method called large-eddy simulations (LES), Ciri has revealed new insights about how different types of waves—ranging from young, choppy waves to long, gentle swells—alter wind flows around offshore wind turbines that could help optimize power generation in ocean-based wind farms.

To model these complex interactions, Ciri and his colleagues used an innovative technique that combines air and water flow simulations. They applied a hybrid immersed-boundary/level-set method, which simulates how the wind interacts with changing sea surface heights and a rotating actuator disk model – mimicking the wind turbine’s behavior as it encounters various wave conditions.

“Using Expanse at San Diego Supercomputer Center, we found that wave patterns play a significant role in shaping the wind speed and turbulence close to the water's surface,” Ciri said. “Specifically, waves tend to slow the wind in the lower layers of the atmosphere while boosting turbulence kinetic energy (TKE) near the ocean’s surface, causing shifts in the wind turbine's wake—the area behind the turbine where wind speed drops.”

He explained that the type of waves also affects how quickly the wind "wakes" up after passing a turbine: developed waves slow this wake recovery, while waves of intermediate age actually speed it up. This increase in turbulence near the rotor affects the turbine’s efficiency and durability, leading to more variability in power production and increased stress on the turbine blades.

However, the study found that this turbulence doesn’t follow a simple pattern or align with the wave frequency – suggesting that the impact of waves is more complex and dispersed over different frequencies.

“The study underscores the need to consider ocean wave patterns in offshore wind farm design – potentially guiding future improvements for more resilient and efficient turbines on the open sea,” Ciri said. “Thanks to funding by the U.S. National Science Foundation ACCESS program to create these simulations on supercomputers, we will continue this work to include even more detail about the impact of the varying waves on the turbine designs.”

The work was recently published in the Journal of Physics: Conference Series. Computational support was provided by the U.S. National Science Foundation ACCESS program (grant no. PHY210106).