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Interview with Ulf Ringertz about CERO project and more

Publicerad 2021-10-28

We talked with professor Ulf Ringertz about the CERO project and his contribution in it, as well as his interesting work with NASA in aeroelasticity.

Hello Ulf, tell us a little bit about yourself, where do you come from, your academic studies etc?

Well, I am pretty much an all-KTH product. I started the Aeronautics program at KTH in 1980 when I returned from the US having spent a year as exchange student in Tampa, Florida. I did military service during 1982-1983 and then graduated as civilingenjör in 1985. I went on to do a Ph.D. thesis on structural optimization finishing in 1988. I then left KTH briefly doing a Post Doctoral visit to the Department of Operations Research at Stanford and then worked a couple of years at the Aeronautical Research Institute of Sweden before returning to KTH in 1993. I was appointed professor of Aeronautics in 1997 and have stayed on since then.

What does your work as professor at KTH entail?

I teach classes on Flight Mechanics (SD2805) and Aeroelasticity (SD2810) and do project work and research mainly on Aeroelasticity. I also make sure to combine my work at KTH with active flying in my glider, often in competitions. I am also a certified aircraft technician licensed to work on sailplanes made of composite materials. I also do some work for the Swedish Accident Investigation Authority (Statens haverikommission) helping out with aircraft accident investigations.

What have been the biggest challenges?

Mainly the legal procedures of getting complicated project proposals through the Research Office at KTH and all the new layers of management.

Tell us about your research, what makes it important?

My main effort is directed to Aeroelasticity which is the interaction of aerodynamic forces with the structural flexibility of aircraft structures. Structural vibrations can be amplified by the aerodynamic forces causing divergent vibrations known as flutter which can lead to structural failure. So, it is important to demonstrate through experiments and analysis that any aeroelastic instability will not occur in normal flight operations. You would probably be surprised to know how small the margins of safety are for most passenger aircraft that you regularly fly with. I do work both on analysis and experiments, but a major part of my work involves designing and building wind tunnel models for testing in wind tunnels. A main effort I am involved in concerns testing in the Transonic Dynamics Tunnel (TDT) at NASA Langley in the US. We at KTH design and supply the model and the Americans provide the testing facility, we then share the data from the testing. We are now planning the next test campaign but the pandemic has created delays and significant difficulties for our joint effort.

What are the biggest challenges your research combats?

Again, it is the legal processes of getting the project contract signed with NASA and KTH lawyers involved. Testing at NASA is also complicated since the TDT facility is located on the Langley Air Force base meaning one needs security clearance from both NASA and the US Air Force. The technical issues are easier to deal with.

You are working on CERO-project, what is the project about?

Climate and Economic Research in Organizations (CERO) is a concept developed by KTH researcher Markus Robert and is a tool to help organizations find strategies to reach goals on reducing climate impact of travelling. So, we are working on strategies to reduce the negative consequences of our travelling without too much negative impact on our other goals such as increased international exchanges.

When did the project start, and does it have an end date?

I was asked to join in early 2020, but there had been activities going on before that. I do not know of an end date; this is an effort that is likely to continue in some form for a long time.

What are the goals of the project?

KTH has very ambitious goals to reduce our environmental impact. Our travelling is a significant contributor to this so how to reduce our impact without seriously damaging our other objectives is the main focus.

Have you already achieved something through CERO that you would like to share with us?

I have managed to run an interesting study together with a master student, Cherine Colliander. We investigated domestic travelling in Sweden by train, bus, car and aircraft using the KTH travelling guidelines for evaluation. This means that we need to solve a multi objective optimization problem where we consider the sometimes-conflicting requirements of time, cost, safety, work environment and environmental impact of travelling. So, we did a number of trips measuring these quantities as best as we could with the models and very modest means available to us. The report is available on Diva:

This little study gave some interesting perspectives such as that travelling by train is not always better than other alternatives. Travelling by electric car turns out to be very good, much cheaper than train, in particular if several share a car, and with similar environmental impact. Travelling by sailplane turned out be faster than all ground based modes of transportation and with zero emissions but unfortunately very dangerous compared to the alternatives.

Does the project have practical applications, if so, what would these be?

I do hope that this project will increase awareness on how to carefully plan and optimize your travelling to be as efficient as possible. One will need to decide themselves how to define efficiency since one has to balance the conflicting requirements in our travelling guidelines. There is no simple answer to this question. Clearly the best option is to stay at home and do all your meetings over the Internet but beware of the consequences of not participating in sensitive project negotiations in person.

Has your work been affected by the pandemic?

Very much so since I have not been able to travel to the US for a long time. I had booked a flight on March 26, 2020, which I had to cancel one week before departure as the pandemic ran out of control. The pandemic is still very much going on and I do not know when I can return to NASA for further preparations of our wind tunnel testing.

Is it important for you to communicate your work and research to the world, if yes why and how do you do that?

Well, my research is mainly communicated in a small but very international community of aeroelasticians. Not sure how our topic would be suitable for a more general audience since it could scare people from flying. It is a very dangerous mode of transportation in some sense, but since we are very careful with analysis and testing when designing and operating aircraft and that we also investigate the accidents that do happen carefully to learn and improve, we manage to make flying very safe.

Text: Elina Charatsidou

Innehållsansvarig:Kommunikation SCI
Tillhör: Skolan för teknikvetenskap (SCI)
Senast ändrad: 2021-10-28