Face rough seas | MIT News

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On his first day of classes at the School of Naval Architecture and Maritime Engineering at the Technical University of Athens, Themistoklis Sapsis had a very satisfying achievement.

“I realized that ships and other maritime structures are the only ones to operate at the interface of two different media: air and water”, explains Sapsis. “This property alone creates so many challenges in terms of mathematical and computational modeling. And, of course, these media are not at all calm – they are random and often surprisingly unpredictable. “

In other words, Sapsis did not have to choose between his two great passions: immense ships and oceanic structures on the one hand, and mathematics on the other. Today, Sapsis, an associate professor of mechanical engineering at MIT, uses analytical and computational methods to try to predict behavior – like that of ocean waves or instability inside a gas turbine – in the midst of uncertain and sometimes extreme dynamics. Its aim is to create structural designs that are strong and safe, even under a wide range of conditions. For example, it can study the loads acting on a ship during a storm, or the separation of flow and reduction in lift around a helicopter rotor blade during a difficult maneuver.

“These events are real – they often lead to great disasters and great casualties,” says Sapsis. “My goal is to predict them and develop algorithms capable of simulating them quickly. If we achieve that goal, then we could start talking about optimizing and designing these systems with these extreme, rare, but possibly catastrophic events in mind. “

Growing up in Athens, where great maritime and mathematical traditions date back to antiquity, Sapsis’ house was “full of machine parts, spare engines and engineering plans,” his father’s tools of the trade. as a superintendent engineer in the maritime industry.

His father traveled abroad to oversee major ship repairs, and Sapsis often accompanied him.

“I think what impressed me the most when I was a kid was the size of these ships and especially the engines. You had to climb five or six flights of stairs to see everything, ”he recalls.

There were also math and engineering books in the Sapsis house – “a lot of them,” he says. His father insisted that he study mathematics closely, at the same time that young Sapsis was carrying out physics experiments in the basement.

“This back and forth between dynamic systems – mathematics more generally – and naval architecture” was frequently on his mind, says Sapsis.

In college, Sapsis ended up taking all of the math courses on offer. He says he was fortunate enough to come into contact early on with the most mathematically inclined professor at the School of Naval Architecture and Marine Engineering, who then mentored Sapsis for three years. In his spare time, Sapsis even took classes at the university’s School of Applied Mathematics.

His undergraduate thesis focused on the probabilistic description of dynamical systems subjected to random excitations, an important topic for understanding the movements of large ships and loads. One of Sapsis’ most memorable research breakthroughs occurred while he was working on this thesis.

“My thesis supervisor gave me a nice problem,” says Sapsis. “He warned me that I probably wouldn’t be able to get anything new, as this was an old problem and many had tried over the past decades without success.”

Over the next six months, Sapsis went through every step of the methods that appeared in the academic literature, “over and over again,” he says, trying to understand why various approaches have failed. He began to discern a path to deriving a new set of equations that might achieve his goal, but there were technical hurdles.

“Without much hope, because I knew it was an old problem, but with a lot of curiosity, I started to work on the different stages”, explains Sapsis. “After a few weeks of work, I realized that the steps were over, and I had a new set of equations!

“It was definitely one of my most enthusiastic moments,” says Sapsis, “when I heard my advisor say, ‘Yes, this is new and this is important! “”

Since that early success, the engineering and architectural issues associated with building for the extreme and unpredictable ocean environment have provided Sapsis with many research problems to solve.

“Naval architecture is one of the oldest professions, with many outstanding issues and many more to come,” he says. “Theoretical tools should not be more complex than the problem itself. However, in this case there are some really difficult physical problems that require the development of fundamentally new mathematical and computational methods. I always try to start with the fundamentals and build the right theoretical and computational tools to hopefully get closer to modeling some complex phenomena.

Sapsis, who joined MIT faculty in 2013 and was tenured in 2019, says he enjoys the energy and pace of the Institute, where “there is so much going on here that you can never feel that you’ve done enough – but in a healthy way. “

“I always feel touched by the incredible accomplishments of my colleagues and our students and post-docs,” he says. “It is a place filled with pure passion and talent, mixed for a good cause, to solve the world’s toughest problems.”

These days, Sapsis says it is his students who experience the sheer excitement of finding solutions to problems on the ground.

“My students and post-docs are now the ones who have the pleasure of being the first to know when a new idea works,” says Sapsis. “I have to admit, however, that I have a few problems with myself.”

In fact, Sapsis says he relaxes by “thinking about an interesting problem: a problem with high risk and low expectations.” I am thinking of a strategy to achieve this but be aware that it probably won’t work. It’s something that I don’t consider work.


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