by Stephanie Green ’09

The physics department at Bethel University has gone above and beyond the standard in recent years with alumni success, state-of-the-art equipment, awards and scholarships, and now the speed of sound.

Three times that, actually.

Professor of Physics Keith Stein, along with several Bethel students, is working on a supersonic flow device that will aid research on shock wave behavior and provide insight for solving problems associated with such devices. The structure, more than five meters in length and constructed of stainless steel, is currently scattered in pieces in Stein’s office and the physics department hallway, but the apparatus should be assembled and fully operational by the summer.

The device is shaped like a long tunnel with one end capped and a connecting nozzle at the other end. Attached to the nozzle is a “test section,” where shock waves and supersonic aerodynamics will be observed and analyzed by Bethel students. These shock waves, or “disturbances,” will travel through the test section at very high speeds and will result in air speeds around Mach 3—or three times the speed of sound—for a total of more than 2,000 miles per hour. Attached to the test section is a 120-gallon “dump tank,” where excess gas settles after being sent through the device.

Operation of the shock tunnel is achieved by pumping air to high pressure at the capped end (i.e., “driver” section) of the tunnel. The high pressure bursts a thin aluminum diaphragm, driving a supersonic flow of air through a test section and allowing for a few milliseconds of test time. Senior physics major Matt Freeland is working with a computer program to characterize the shock tunnel performance under a variety of test conditions.

Preliminary designs for the supersonic flow device were established by a group of four students as a project in Stein’s fluid mechanics class. Freeland and former Bethel student Andy Cureton finalized the design this past summer. Since then, construction of the tunnel has begun, with Ken Steinbach of the art department supporting the construction through the welding of the steel components. Stein has also received consultation from Professor of Physics Richard Peterson for his expertise with lasers and optical measurement techniques.

Stein recently received an Alumni Faculty Grant to bring Bethel alumnus Matt Borg ’03 to work with him and two undergraduates on the project this summer. Borg is finishing his Ph.D. in aerospace engineering at Purdue University.

“We are proud of our physics and engineering students, and we strive to provide them with relevant and valuable undergraduate research experiences,” said Stein, on the benefit of having a supersonic flow device at Bethel. “These experiences also serve to strengthen their opportunities for graduate school.”

Both Freeland and senior Laura Steen plan to study aerospace engineering in graduate school in the fall. Steen attests that her learning experience with the device’s creation will aid in her goals for graduate school.

“[It’s] really fascinating for a physics major to see the work that goes into simply creating the apparatuses that are used—a lot of analysis has to be done just to be able to begin testing…how a shock wave performs,” said Steen. “Every insight I have gotten [from] this is very useful for understanding the field that I will be entering.”