4/9/2013 Written by Melissa Mitchell, News Editor
Written by Written by Melissa Mitchell, News Editor
For the past year, the students - under the tutelage of former department head Mike Bragg (now an associate dean in the College of Engineering) and research scientist Andy Broeren (now with NASA) - have been conducting a series of experiments with half-scale and smaller models of racing wheelchairs and their own mini-sized version of a crash-test dummy in the department's wind tunnel. Some of the students began working on the project in Broeren's senior design course last fall and have since formed a registered student organization called the Racing Wheelchair Aerodynamics Design Team.
The team's goal has been to figure out how the U. of I. racers - and other competitive racers - can make aerodynamic improvements that would ultimately enhance performance speeds.
"There are very few examples in the literature on wheelchair aerodynamics," said research team member Greg Busch. "There is a lot of intuitive thought on how to do it. For instance, to keep the frontal area of the chair small, or for the racers to tuck their heads."
Bleakney said some racers have tried other tricks, including taping contact paper to the undercarriage of the chair. As it turns out, "that doesn't do anything measurable," said Busch, noting that undercarriage taping was one of several theories put to the test.
A couple of the other ideas did yield noticeable, measurable results. For instance, the research team found that athletes who position their heads and torsos in a tucked, rather than upright, position, realize a 10 percent reduction in drag.
The students also have studied the effect of attaching various sizes of fairings to the scale models they've tested. Similar in function to the windshield on some motorcycles (also known as a fairing), the bullet-shaped attachment "smoothes airflow around riders, reducing aerodynamic drag," Busch said.
Their most successful attempt on that front yielded a 12 percent drag reduction.
The best overall benefit, however, appears to be combining a fairing with the racer in the tucked position. With that configuration, drag was reduced by 25 percent. "We figured we would have a few percentage-point differences," Busch said, "but 25 percent was a big surprise."
Other variables the engineering students have investigated include the design of the chairs' front wheel - spoked or solid - and positioning the rider's feet tucked under the body versus feet dangling.
U. of I. coach and Paralympics competitor Bleakney said he and the student athletes are excited about the initial findings of the engineering team because prior to this, ideas about what worked and what didn't were largely unproven.
"Because we had no scientific data, everything was ad hoc," he said. "That's what's exciting about the work and the data we've got now. It gives us a base to work off of, for starting testing on the field to see if the data in the wind tunnel correlates to the real world."
Busch said the engineering team hopes to be able to move to that next phase - testing their theories using human racers, on the track - this fall. Such tests might include measuring the total power needed to propel a chair around a track.
According to the students' Web site, challenges of such future testing would be difficulties related to controlling external variables such as wind, and obtaining reliable measures of required power.
Besides Busch, other members of the engineering research team have included Jeremy Alonso, Jeff Burgess, Maulik Choksi, Austin Ellis, Wes Hammes, Bryan Lin, Krunall Patel and Chris Richgruber. The scale-model wheelchairs are based on a computer model from wheelchair manufacturer Invacare Top End and are constructed from rapid prototyping material in the engineering college’s Ford Lab in the Mechanical Engineering Laboratory. Wind-tunnel time was donated by the aerospace engineering department.