"In industry, my job was to mitigate problems. Now I look for causes"
Eunok Yim © Adrian Alberola Campailla
Eunok Yim is head of EPFL’s new Hydro Energy & Applied fluid Dynamics Lab. Her path to academia was illuminated by a four-year stint at General Electric, where she worked on optimizing hydropower mechanical performance.
As a high school student near Seoul, South Korea, Eunok Yim was already interested in a science career. She loved her science classes and was active in her school’s physics club. But it was a volunteer visit to a local care home that sparked her interest in engineering.
“You might think that working in a care home would inspire an interest in medicine or biology, but all I could think about was how technology – especially mechanical engineering – could really help people, especially those with reduced mobility,” she says.
Yim decidede to enrol in KAIST, the Korea Advanced Institute of Science & Technology, where she earned her bachelor and master degrees in mechanical engineering. Her interest in fluid dynamics was born – again unexpectedly – when she joined an acoustics lab: “Our work was on pure acoustics, which is more about pressure fluctuations than the flow of soundwaves. But I really wanted to understand what happens when waves start to flow.”
In my lab, I want to find the source of these fluid flow instabilities so that we can control them.
Today, as head of the newly formed Hydro Energy & Applied fluid Dynamics Lab in EPFL’s School of Engineering, Yim is doing just that. Her research focuses on understanding turbulence, vortices, and other fluid flow instabilities via theoretical models and simulations. Her work is important for improving the efficiency of hydraulic machines like turbines and generators, especially as global demand for sustainable hydropower continues to grow.
Getting to the bottom of flow instability
After graduating from KAIST, Yim wanted to pursue a PhD in fluid mechanics, but she wanted just as much to explore life and learning outside of Asia.
“I was considering several schools around Europe, and I made my choice – École Polytechnique in Palaiseau, France – based on how easy it would be to visit as many other countries as possible!” she laughs. “I really liked the the culture of learning through discussion that I discovered in Europe, which is very different from Korea. It was a kind of culture shock, but it led me to discover new ways of thinking and studying.”
By the time she had completed her doctoral studies on the stability analysis of fluid vortices, she had fallen in love with Europe – as well as with a French man who would become her husband. So she opted to pursue postdoctoral studies, first in Marseilles, and then at EPFL in the Lab of Fluid Mechanics and Instabilities led by François Gallaire.
But at the end of her postdoc, Yim found herself at a crossroads. She wanted to stay in Europe, but the only suitable open faculty position was back in Korea. As fate would have it, Yim was offered the faculty post at the same time as an industry job that had opened at General Electric in Baden, Switzerland.
“I had never worked in industry, and the job was in hydropower, so I felt I could still contribute to helping people – this time by making the world’s energy cleaner.”
At GE, Yim’s job was to use computational modelling to rapidly predict the overall performance of turbine and generator systems within certain parameters for prospective clients. An important part of this work was predicting fluid instability linked to vortices, because such instability limits the operational range of these systems, resulting in inefficiencies and decreased performance.
Yim thoroughly enjoyed this work, and her eventual decision to return to EPFL as a professor was driven not by a dissatisfaction with industry, but by a persistent scientific curiosity that could only be satisfied in the lab. Her ultimate goal: to develop new approaches to controlling instabilities in hydropower flows.
“If you have a flow in a hydraulic system, you need to know if it’s unstable, and if so, to find the root cause of that instability so you can suppress it,” she explains. “In industry, if you know how to mitigate problem, then your work is done – you don’t go beyond that. In my lab, I want to bridge that gap: to go beyond, and find the source of these instabilities so that we can control them.”