Mechanical engineering professor Jenn Rossmann explores the science of an American hobby – The Lafayette

Mechanical engineering professor Jenn Rossmann was recently featured in an NPR podcast last Thursday with reporters Emily Kwong and Maddie Sofia about her research into the science of the curve of a Wiffle Ball.

As a “longtime listener” to NPR, it was a surreal experience for Rossmann.

“I never imagined hearing my own voice among the familiar extended family of NPR hosts. Emily Kwong was so much fun to talk to,” Rossmann wrote in an email.

As explained in the podcast, the Wiffle ball game was invented in 1953 and is a lightweight alternative to using a baseball. What is different with this ball is that youYou don’t need a good pitching arm to bend these balls, and the makers don’t even really know why.

As a specialist in fluid mechanics and known for researching ways to make learning more convenient for her students, Rossmann was inspired by the mechanics of the Wiffle Ball and began using it for research with her students. This research began in 2002 and experiments are carried out in a wind tunnel.

Rossmann explained that fluid mechanics involves studying both how and why fluids flow, as well as the forces that push them and the kind of patterns they trace.

Rossmann and his students study the “peculiar physics of the Wiffle ball curve”. This idea was relatively nNew mystery for her to explore, because no one had really studied this question scientifically before.

It turns out that asymmetry is what makes the Wiffle Ball so dynamic. As explained in the podcast, the ball is hOles disrupt the airflow around the ball, and because it is so light, it has an unstable and unpredictable trajectory.

Rossmann bbegan conducting experiments with students in which they used the wind tunnel on the Lafayette campus.

“The Acopian Wind Tunnel [Engineering Center] allows us to study a wide variety of flows, so we use it to help students learn about lift and drag forces, and we use it to test prototypes for design and projects (d ‘a high-altitude satellite balloon that the ASME club had designed, to an aircraft components) or to measure aerodynamic forces for research projects, for example on models of wing-flapping insects in flight,’ wrote Rossmann.

They then skewer the Wiffle balls to hold them in place at different angles and manipulate the velocity to measure subsequent forces on the ball.

Rossmann’s research paper in the American Journal of Physics focused on what happens with the air above, on, and inside the balloon using the wind tunnel. She called this mechanism the “trapped vortex effect”.

“It’s when the flow inside a chamber or cavity swirls around—a vortex is a spinning region of fluid—and it doesn’t leave the chamber,” Rossman explained. “In the case of the Wiffle Ball, there are a pair of trapped vortices inside the ball which together exert a force on the ball from within, affecting its trajectory.”

Part of wiffle ball culture, as the podcast discussed, includes the art of scuffing wiffle balls to increase their performance. Rossmann and his students are currently creating an “atlas” showing how different surface scuffs, knife patterns and other “aftermarket” adjustments affect corresponding aerodynamic performance. They even received donations from Wiffle ball players of balls with different scratches to help with research.

“It’s so rewarding to be able to extend knowledge beyond the classroom and to ask new questions, make discoveries and solve problems together,” Rossmann said.

His research showed how the effect on the ball depended on the speed at which the ball was thrown as well as the orientation of the ball when thrown. Rossmann and his students used a computer model to show whether external or internal air had a greater effect on overall ball flight.

Rossmann thinks it is useful to understand phenomena, even if there is no immediate practical application in mind. However, she explained that this research can be used to design other sport projectiles, or, “it can also be something that is transferable to another field, like maybe we could apply this work to think about the stability of a small plane or a drone,” she says.

In the podcast, Rossman emphasized the importance of making mistakes and learning from them in science.

“Sometimes science is taught as if it were this monolithic body of knowledge that was set in stone…People acquired this knowledge, and they did it by stumbling, trying things, and having the bad idea, and learning over and over,” she said. . “The more human you make it, the more possible it is for any student, I think, to see themselves as potentially a ‘science maker’.”