��ɫ��Ƶ

This month, INSTAAR welcomed associate professor of mechanical engineering��Nathalie Vriend��to the institute as a senior faculty fellow. Vriend’s research aims to deconstruct the physics of granular flows in nature. In particular, her work provides insight into the physics of avalanches and migrating sand dunes.

As a senior faculty fellow, Vriend will become a voting member of the��INSTAAR directorate while continuing her teaching and research in the��Paul M. Rady Mechanical Engineering College of Engineering and Applied Science. She is also eager to explore new collaborations with other INSTAAR scientists.

“Nathalie is an outstanding scientist who will enhance our interdisciplinarity, deepen our expertise in fluid mechanics, and expose INSTAARs to novel laboratory techniques for the study of geophysical phenomena,” INSTAAR director Nicole Lovenduski said, adding that her appointment will strengthen ties between INSTAAR and the Paul M. Rady Mechanical Engineering College of Engineering and Applied Science.

In light of her recent appointment, INSTAAR sat down with Vriend to talk about her career, research interests and aspirations for future collaborations at the institute.

Q: Why were you interested in joining INSTAAR?

A: When I came to ��ɫ��Ƶ two-and-a-half years ago, I heard about the different institutes, but I wasn't really aware what the mechanics or benefits of joining were. More recently, I struck up a conversation with INSTAAR director Nicole Lovenduski, and I realized that INSTAAR’s focus overlaps with at least half of my work, because snow and avalanches occur in the arctic and alpine.

After talking with Nikki, I saw great potential in connecting with people that do field work in these environments. I’m in mechanical engineering and barely any of my colleagues actually go out into the field. INSTAAR’s logistical support, storage facilities, and experience in applying for field grants and executing field campaigns—those things were big selling points for me.

Q: Tell us about your research on avalanches.

A: It goes back to my very first research job after my PhD, where I studied avalanches in Switzerland. In essence, my research has always focused on moving snow. So we're not talking about fracturing or the initiation of a snow avalanche, which is a completely different topic. But, if a snow avalanche has already started and is moving along, how fast does it go? What kind of pressures are exerted on it? What's the reach? What's the run out? I’m interested in the physics of avalanches.

Then come the implications. Where could you build infrastructure safely? What kind of defensive structures could you build to divert an avalanche out of the path of greatest danger? How can we model avalanches, so that we can predict where they might go?

I recently gave a guest lecture on snow avalanche field work and one of the students was like ‘Wow. You went and built this experiment and recorded three artificial releases of snow throughout the winter and that’s all the data you could collect?’ Yeah. Field work with avalanches is just hard because you’re dependent on factors you can’t control. And, if an avalanche goes, you have to get the data there and then. If something fails, you’re out of luck.

So, because of those factors, I moved more into the lab. It’s much more controllable. We can repeat it. We can change certain parameters to nudge behavior in a certain direction. In my lab right now, we’re specializing in a technique called photoelasticity. It creates these fantastic images that are not only beautiful, but hold a lot of quantitative information.��

Q: Fascinating. I know you also do research on sand dunes. Can you tell us a little bit about that?

A: Sand Dunes were my first scientific love. It’s what I did my PhD on, which was 15 years ago mind you, I guess I’m getting a bit old. I looked at the booming sand dunes or the singing sand dunes. Basically, if you create an avalanche on a sand dune it creates a very musical tone. We explained that using geophysical methods, acoustics and some, you might say, granular mechanics.��

It creates such a magical, mystical sound, and there were a ton of TV news segments about the research—PBS, National Geographic, the Discovery Channel. It was 15 years ago, and PBS even asked me to do an interview a couple of years ago. They keep coming back to it.

Since then, I’ve done several field trips to Qatar and White Sands National Park here in the U.S. to investigate the structure of sand dunes—how they are layered and what that tells us about their history.��

When you cut a cross-section of a tree you get tree rings. You can count them, measure them and see which years the tree was growing slow or fast. The same thing happens to sand dunes. As they migrate, they continuously avalanche and form layers. Depending on the width, you can see how fast it was moving.

Q: Why does your research matter? Why is it important?

A: It’s very simple in both cases. For sand dunes, we’re living in a drying world. We have a loss of agricultural resources. Rivers are drying up. Playas are drying up and creating more sand and more dust. So sand dunes are really important.��

I visited places in Qatar where dunes were engulfing roads. In the capital of Mauritania, Nouakchott, a dune field is slowly encroaching on the city. It's just engulfing houses, and there's nothing they can do about it. And, closer to home, we have Lake Michigan. They have a row of villas next to these sand dunes and, one by one, they are getting overtaken. They’re trying to get them out with bulldozers, but, of course, it isn’t working. So one by one, you can see your neighbors losing your house, and you know you're next.

Sand dunes can have a huge impact on human infrastructure, so we need to understand how sentiments move, and how we can adjust their behavior. Can we stabilize them? Can we divert them?

The rationale is very similar for avalanches. We might have been able to rely on historical data in the past, but with climate change avalanches may be bigger. They may be happening in different areas. Their impact may be much, much more significant. So we really need to understand how avalanches move, and how other debris flows and landslides move.This might allow us to predict their behavior and plan for it. I approach that through physical modeling.��

Q: What kind of collaborations do you envision might be possible within INSTAAR?

A: I’ve been talking with��Julia Moriarty, who does coastal research. She does a combination of sedimentology, fluid dynamics and coastal oceanography. We had been talking about potentially applying for an NSF grant, but in the end we split the project into separate proposals with the postdoc involved. Nonetheless, we know we have a common research interest that could lead to further collaborations.

There’s also a very clear overlap between my research and��Irina Overeem’s work. She works with glaciers and ice streams and sediments.��

Finally, Bob Anderson has worked on geomorphological problems that I’m interested in. There might be something there.

I still want to reach out to Mountain Research director Scott Taylor and the people in charge of cold rooms to explore more possibilities. I’ve talked with Nikki and some others about the possibility of doing some small experiments in the cold room, because some of my work could definitely benefit from a cold environment. We’re still investigating whether our cameras, which are quite fancy, could deal with minus 10 degrees.

I will also be giving a talk at the Mountain Research Station summer seminar series [stay posted here and on our��events page for more info].