Look anywhere at the School of Engineering and you’ll find students engaged in brainstorming, tinkering, and building. But a new wind tunnel in a mechanical engineering lab puts a fresh (and high-speed) spin on that passion for problem-solving. 

The compact, ten-foot wind tunnel was built over the past 10 years by students passing the torch to their successors. Interruptions both academic (students graduate, faculty take sabbaticals, labs are moved), and unexpected (a global pandemic), might have slowed progress, but the collective effort wrapped up earlier this summer. That’s when Rob White, associate professor of mechanical engineering, and his students turned the wind tunnel on and took it on a spin in room 313 at 574 Boston Avenue.

White shared his enthusiasm on social media: “We have flow!! Now on to aerodynamics and experiments!!” he reported, as the tunnel, with the cautious increase of air flow from a blower, reached its target speed of Mach 0.5, or 380 miles per hour. 

White, whose research spans a variety of sensing systems, including aerodynamic measurement technologies, said the tunnel will support highly controlled research related to aerodynamics, including development of micro-electromechanical systems (MEMS) surface and pressure sensors, and wind sensor technology with a wide range of aerospace applications.

Most importantly, he adds, the success of the wind tunnel, no small engineering feat given its exacting and complex design, speaks volumes about the importance of providing creative opportunities for students to grow as engineers.

“Students put a lot of work into building the system from the ground up,” he says. “There were many challenges, but they were inspired to keep going. Now their hard work has come together, which is phenomenal.”

Ethan Laverack, E16, first took on building the tunnel in 2015 for an independent project with White to build on a class in Fluid Mechanics with Professor Jeff Guasto (and whom he credits for providing the “math and theory” he needed to conceptualize its design.)

 He was glad to hear about the project’s success and reflected on what its back story exemplifies and what it can teach aspiring engineers. 

“I hope students take away that it’s OK to not see a project through all the way to the end,” he says. “Work hard, do the best you can do. But if you have to drop it, it’s OK. Everybody has a unique set of skills that are suited to solve problems. You just have to seek out the problems that match your strengths and get started.”

It Takes a Village 

The idea of a Mach 0.5 tunnel (the Mach number is the ratio of an object’s speed to the speed of sound), was on White’s wish list a decade ago. At the time, he thought a tunnel that achieved that threshold of high velocity would be a useful tool for aerospace engineering research that involved sensors to reduce cabin noise in commercial aircraft. 

Specifically, he envisioned a recirculating wind tunnel, meaning air flows within a closed loop. While the actual test section of the tunnel would be small (at its cross-section, just two by four inches), it would require an array of supporting components that make sure air flow is smooth and consistent, allowing for accurate measurements.

The tunnel development is a case study in putting problem-solving skills to work. Laverack, for starters, drew up initial design calculations, then he went on to build the test section and the contractior, or funnel, that leads into the test section. He wasn’t sure how to fabricate the contraction’s curved shape until he recalled his experience sailing a Sunfish sailboat, with its smooth, lightweight fiberglass hull.

As for molding fiberglass for the contractor, he was inspired by his grandfather, a former physics professor at Penn State, who had a hot wire cutter he used to build model airplane wings out of foam. 

Laverack went on to create a kind of “layer cake” of foam coated with a sealant and layering the fiberglass on top, a design and fabrication process that was proved to be not only solid, but accurate. 

Graduate student Yucheng Sha, EG20, focusing on the wind tunnel design and operation in his master’s thesis, followed up by checking those initial design calculations and by building the diffusers and settling chamber, essential to smooth airflow. (The diffuser gradually slows the flow from high speed before it goes back around the loop, and the settling chamber allows turbulence coming from the blower to settle out before it gets to the test section.)

“He didn’t find my calculations to be totally wrong,” says Laverack, gratefully.  “I’m happy that I was able to provide a good foundation for the students who came after me.”

Solid groundwork on the tunnel resumed last summer when Owen Swint, a high school summer student, built some of the wooden framing and the “honeycomb,” a pattern of tubes that further reduces turbulence. 

Then this past academic year, Steven Rauso, E26, and Sean Doherty, E27, took on other crucial elements by completing the duct system that channels airflow back to the fan after it has passed through the test section. 

They also designed and 3D printed pivotal pipe connectors, or flanges, built a stand to hold the heavy 15 horsepower blower, and further ensured structural integrity by checking all measurements and fasteners.

Rauso also ventured into woodworking. As the tunnel was on the floor—not an ideal place for conducting future research experiments—he built a sturdy, 10-foot table out of two-by-fours and plywood. 

“We wanted to raise it up so that the test section could be seen. The idea was if you sit down, you should be eye level with the test section,” he says. “The length of the table is what made it difficult. The structural supports I put in at first weren’t good, so I had to take the whole thing apart and put it all back together again.”

His work on the wind tunnel provided a deep sense of accomplishment, he says, largely because it was an opportunity “to try something new that had a ‘real-life application,’ he says. “And I was using my manufacturing knowledge and fluid systems, tying it together was really cool.”

More recently, Erika Tragin, E28, and Daniyal Maitekov, E27 got to work on tunnel’s connection to a computer system and the speed controller, called a variable frequency drive (VFD), which will allow precise and computer automated flow speed control and measurements of both flow properties and model lift and drag.

The project, she recalls, had its share of questions to solve. “I had to figure out what kind of protocols were necessary to connect to the computer,” she says. “What kind of software would actually control the VFD? And once we get data, how do we interpret it? All those kinds of things I was working on and hope to work on again this year.”

Indeed, White sees the wind tunnel as an ongoing catalyst for student learning, invigorating curiosity about aerodynamics, a field that can engage engineers with wide interests. “I expect it will spark interest and open up ideas,” he says. “Laboratory work is always good for that.”

“Now that we know it works, it opens so many doors to engineering, and to me that’s amazing. Professor White has told us that now, if we come up with ideas, to let him know. And I’m like: yes, absolutely!”