Wind, wave research
Photo courtesy of Kianoosh Yousefi March 25, 2021
Postdoctoral researcher reflects on time at UD, plans for the future
For the last six years, University of Delaware postdoctoral researcher Kianoosh Yousefi has made UD his home.
But now, after being selected as a 2020 Computing Innovation Fellow (CIFellows 2020) by the Computing Research Association and its Computing Community Consortium with support from the National Science Foundation (NSF), Yousefi will be joining Columbia University as an associate research scientist where he will be mentored by Marco Giometto, assistant professor of civil engineering and engineering mechanics.
Yousefi will join 58 other CIFellows 2020 who cover a broad range of computing research interests and come from 46 different universities.
While he is undoubtedly excited to start his new position in summer 2021, Yousefi admitted that it would be tough to say goodbye to UD.
“UD is like my home. I’m really comfortable here. I know everyone and working with people is very easy for me so I will miss UD a lot,” said Yousefi. “I love being here but at the same time, I have to leave my safe zone. You have to do that at some point. You have to get out of your safe zone, be more adventurous.”
Yousefi earned his bachelor’s and master’s degrees in mechanical engineering from the Islamic Azad University, Mashhad Branch, in Iran, and when it came time to apply for doctoral programs, he decided to continue his studies in the United States. He heard about UD from one of his friends who was attending UD as a doctoral student.
While a doctoral student in the College of Engineering, Yousefi conducted his doctoral and postdoctoral work with Fabrice Veron, deputy dean in the College of Earth, Ocean and Environment (CEOE), whose research focus closely aligned with Yousefi’s interest in fluid mechanics.
“I came to Fabrice and he told me he had an interesting project about the turbulence and airflow separation, which was similar to what I had done for my master’s degree. So, I happily started my work with Fabrice in February 2016,” said Yousefi.
Veron said that during his time at UD, Yousefi “has done a tremendous amount of great, quality work. The fact that he was selected as a Computing Innovation Fellow, a program supported by NSF, speaks to his remarkable abilities and his great potential as a researcher."
For his doctorate, Yousefi researched how ocean surface waves can influence momentum and energy transfers between the ocean and the atmosphere. These exchanges are strongly contingent on small- and large-scale dynamics at the interface between the marine atmospheric boundary layer, the part of the atmosphere that has a direct contact and is directly influenced by the ocean, and the oceanic boundary layer just below the water waves in the ocean.
Several studies have been performed in recent years to investigate these processes, but the coupling between the turbulent boundary layers and the wind-driven waves is still not completely understood. This is especially true in conditions where the wind increases the intensity of the waves.
Yousefi’s research focused on measuring and analyzing airflow velocity above the surface, experimentally and theoretically investigating the turbulence in the airflow above wind-driven waves and the coupling between the turbulent and the wave-induced fields in strongly forced conditions.
“About two-thirds of the surface of the Earth is covered by the ocean. The exchanges of momentum and energy between the atmosphere and ocean over such a huge area profoundly influence the functioning of Earth’s climate and weather systems,” said Yousefi. “This information can help us better understand and characterize extreme weather events where it is important for us to make accurate forecasts of the amount of rainfall and the path of the storm, for example.”
Air-sea exchange processes are particularly crucial for wave prediction models, climate modeling, storm-surge modeling, weather forecasting, and environmental impact studies. Yousefi said that climate forecasting models rely on a process known as parameterization, in which scientists use simplified “parameters” to represent complicated physical processes, allowing mathematical investigations of the phenomena and faster model predictions. In particular, climate forecasting models require the parameterization of momentum, energy, heat, and moisture transfers at the air-sea interface. But the current model parameterizations are far from satisfactory.
“In Hurricane Ivan in 2004, for example, the largest measured wind-driven wave was 27.7 meters, while computer models predicted waves up to 40 meters in the region of strongest wind,” said Yousefi. “The more recent example is Hurricane Harvey in 2017, where most models predicted the storm path correctly but not the intensity of the storm. My work — including my PhD and postdoc projects and the near-future research at Columbia — will lead to improving these model parameterizations.”
Now a postdoctoral researcher in the School of Marine Science and Policy in CEOE, Yousefi has continued his work in the Air-Sea Interaction Laboratory, which is led by Veron, and is building off of his previous doctoral research by examining the airflow above and below surface waves.
By doing this, Yousefi will be able to simultaneously measure the flows on both sides of the air-sea interface in order to investigate the dynamics of the coherent structures and turbulence that drive air-sea interfacial fluxes.
For all of his work at UD, Yousefi utilized the wind-wave tunnel facility at the Air-Sea Interaction Laboratory. Particularly for his postdoctoral research, this will enable him to acquire extensive high-resolution velocity measurements near the interface above and below wind-driven surface waves and turn those measurements into a dataset.
Utilizing particle image velocimetry (PIV), Yousefi will put small tracer particles into the airflow and take snapshots of these selected, or “seeded,” particles in a very short time to see how they move from one image to another.
“The seeded flow will be illuminated with a light source and imaged with a digital camera,” said Yousefi. “The motion of the particles from one snapshot to another snapshot can then produce a local velocity estimate, and these velocity fields can be used to study the flow structure and to calculate the momentum and energy fluxes.”
Yousefi will build off of this work at Columbia but will focus on the multiscale modeling of hurricane boundary-layer flows.
About the CIFellows 2020 Program
The CIFellows 2020 program targeted recent and soon-to-be doctoral graduates in computing whose academic job search was impacted by COVID-19 and aimed to provide them with a career-enhancing bridge experience. With funding from the National Science Foundation, the CIFellows 2020 program offers a 2-year postdoctoral, research-based opportunity in computing, with cohort activities to support career development and community building.