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High-Performance Computing Aids in Predicting Oil Dispersal During Spills

Supercomputer simulations detail oil's behavior during crossflow waves

Researchers from the New Jersey Institute of Technology recently published this supercomputer-enabled simulation detailing what happens when oil disperses during a water crossflow. They relied on Comet at the San Diego Supercomputer Center to conduct their simulations since the high-fidelity models need high spatial and temporal resolution of the turbulent flow structures which was achieved in a reasonable time using many nodes in parallel on Comet. Credit: Center for Natural Resources, New Jersey Institute of Technology

 

By Kimberly Mann Bruch, SDSC Communications

 

According to the National Oceanic and Atmospheric Administration (NOAA), thousands of oil spills occur each year in the United States. Although the majority of incidents involve less than one barrel, the spills have wreaked economic and environmental devastation for decades. To better understand the fate of oil droplets for effective countermeasures, researchers recently created simulations using supercomputers, including Comet at the San Diego Supercomputer Center (SDSC) at UC San Diego and Bridges at the Pittsburgh Supercomputing Center (PSC).


"We used the supercomputers to create high-fidelity, large eddy simulations of underwater oil blowout in water crossflow conditions," Daskiran explained.  "The main goal was to understand the fluid dynamics and estimate the trajectory of different-sized oil droplets, which is important for the countermeasures following oil spill incidents."The systems allocations were funded by the National Science Foundation Extreme Science and Engineering Discovery Environment (XSEDE) and provided the perfect resources for Cosan Daskiran, a postdoctoral researcher and senior engineer at New Jersey Institute of Technology (NJIT), to model studies on how oil dilutes under specific conditions.

Daskiran's XSEDE-allocated supercomputer simulations showed that large oil droplets rose faster and separated from the oil plume without spreading spatially much within the plume due to their higher individual buoyancy. Meanwhile, small droplets were trapped in a counter-rotating vortex pair, which is considered a signature of the jets in crossflow.

Daskiran worked with Michel Boufadel, a professor at the Civil and Environmental Engineering Department at NJIT who has spent much of his career examining the dispersal of oil after a spill. The research team compared Daskiran's simulations with actual oil dispersal experiments before publishing their findings in the October 2020 issue of International Journal of Heat and Fluid Flow.

"We used Ohmsett, short for the Oil and Hazardous Materials Simulated Environmental Test Tank, here in New Jersey to create a life-like oil spill in a controlled environment," said Boufadel. "Ohmsett is operated by the U.S. Navy and provided us an environmentally safe place to conduct tests for this project."

Specifically, the researchers conducted experiments that capture the main features of an oil jet by towing a pipe horizontally in the Ohmsett wave tank and then created simulations on Comet and Bridges based on this study.

"The supercomputers helped us see things in finer detail; for instance, to capture small flow structures (i.e. eddies in the turbulent flow), we needed a high spatial and temporal resolution of the flow which was achieved using many nodes on Comet and Bridges. The supercomputers were also good for large file sizes, but the main contribution of Comet and Bridges was using many nodes in parallel which decreased the simulation time and allowed us to see the details of the flow." -- Cosan Daskiran, Postdoctoral Researcher and Senior Engineer, New Jersey Institute of Technology

By incorporating the findings from predictive numerical simulations with experimental results into the models estimating oil droplet size distribution, the results were more accurate when dealing with an accidental oil spill. Some numerical models might have made simplifications that do not represent the actual physics of the problem, such as assuming that the oil concentration and mixture velocity are axisymmetric (depend only on the distance from the center of the plume), and drop off rapidly toward the edge of jet following a Gaussian or bell-shaped profile.

 "However, this is not the case," said Daskiran. "The formation of the CVP vortices changes the hydrodynamics dramatically, and the oil concentration and velocity do not have an axisymmetric, Gaussian distribution across the plume, assuming so will result in inaccurate estimation of the droplet size distribution which is important for the fate of oil droplets."

Daskiran credited a great deal of the study's success to the XSEDE allocations on Comet and Bridges.

"The supercomputers helped us see things in finer detail; for instance, to capture small flow structures (i.e. eddies in the turbulent flow), we needed a high spatial and temporal resolution of the flow which was achieved using many nodes on Comet and Bridges," he said. "The supercomputers were also good for large file sizes, but the main contribution of Comet and Bridges was using many nodes in parallel which decreased the simulation time and allowed us to see the details of the flow."

The NJIT group, including Postdoctoral Research Associate Fangda Cui and Research Assistant Professor Xiaolong Geng, with the lead of Professor Boufadel, are also working on the transport of saliva droplets in an indoor environment (e.g. a supermarket) for COVID-19. The droplets were tracked using the team's in-house Lagrangian particle tracking code ‘NEMO3D' running on Comet. Understanding how saliva droplets travel within the indoor environment will be critical for national guidelines for controlling the spread of COVID-19, such as those created by the Centers for Disease Control and Prevention.

Funding for this project include an allocation from XSEDE (TGBCS190002). The authors also acknowledge support by the Department of Fisheries and Oceans (DFO) Canada through Multi-Partner Research Initiative (MECTS-39390783-v1-OFSCP), and funding from the Center for Offshore Oil and Gas Environmental Response, or COOGER.

At a Glance

  • To better understand fluid dynamics and estimate the trajectory of different-sized oil droplets, which is important for the countermeasures following oil spill incidents, NJIT researchers recently created simulations using XSEDE-allocated supercomputers.
  • Comet at SDSC at UC San Diego and Bridges at the PSC were used to created models detailing the flow of oil during an incident.
  • The research team published their findings in the October 2020 issue of International Journal of Heat and Fluid Flow.