Top hypersonic researchers entice student to Minneapolis

Q&A with Ph.D. student Sean Cranford

Of all the places in the world he could have gone to study hypersonic flow and massive computer simulations, Sean Cranford chose Minneapolis. What sealed the deal for this second-year Ph.D. student from Kansas was the faculty reputation at the University of Minnesota College of Science and Engineering, and a fellowship from the Air Force Research Lab. 

“Minnesota is actually one of the best places to study hypersonics,” he said, “and it is probably the best place in the world to study computational methods for hypersonics.”

Cranford works at the Computational Gas Dynamics Laboratory led by Professor Tom Schwartzentruber in the Department of Aerospace Engineering and Mechanics. The research team here specializes in particle simulation methods including molecular dynamics—and work is spilt between developing algorithms and physical models for the numerical simulation of complex gas flows. 

In both the video and Q&A below, Cranford shares insights into his field of interest.

What is your research focus? 
My research is focused on computational methods for hypersonics. I study flight vehicles that move at very high speeds, and I analyze their hypersonic flows to better understand their physics and chemical reactions. A lot of my work deals with simulating continuum and rarefied regimes, a gas flow pattern in which the molecules rarely collide.

Because of how complicated and complex hypersonic activity is, we use supercomputers to model and simulate their problems—so we can get answers and data that flight tests can’t get. What would take a typical laptop months or even years to calculate, supercomputers can solve faster. 

For example, this summer when I was finishing up my internship at the Lawerence Livermore National Lab, I ran about 450,000 CPU hours over those 12 weeks using world-class supercomputers. If I were to that work on my own laptop, it would take roughly three-and-a-half years.

How, or why, did you choose the University of Minnesota? 

Hypersonics a small field, but everyone knows about the work being done at the University of Minnesota. Many people I talked to when I was considering a graduate degree told me that this is the place to go. 

Because of my Air Force Research Laboratory fellowship, I pretty much could have gone anywhere. But I chose to come here. The University of Minnesota Department of Aerospace Engineering and Mechanics is just very well renowned in the field of hypersonics. Our professors are some of the top names in the field. Companies and national labs are constantly looking for students from this department to join them.

What is the impact, or real-world application, of your work? 

I get to help analyze and predict things that occur at speeds people can’t see with the naked eye. Think of a capsule reentering from orbit traveling at Mach 20 or more. That's 20 times the speed of sound. My research can directly impact the design of flight vehicles or wind tunnels, and other ground test facilities.

What make the University of Minnesota a great place to this research?

The research-grade vehicles we are looking at are specific flight experiments where we’re pushing the bounds of understanding aerospace applications. We recently hosted an Air Force scientific research seminar where experts from across the nation came to present here. 

Hypersonics has started gaining national attention in last few years as we push for more research and design in aerospace applications. This is a very complicated field. So, there is really not that many experts—but the University of Minnesota has a lot of those experts. Multiple people I worked with in the past were working with some of these well-respected professors. 

The Department of Aerospace Engineering and Mechanics on the Twin Cities campus also produces a lot of the experts in this field. Industry and national labs are constantly looking for students to hire or work with from this department. 

What do you enjoy about your research?

For me, it’s a beautiful blend of applied mathematics, computer science, and very practical or applied engineering. Some of these vehicles we’re looking at typically have extremely high speed, where the aerodynamics and chemistry become very complicated. It’s really cool to see what can happen when we simulate them, push them and see their limits. 

Interview by Pauline Oo