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Physics Of Football In Flight About To Be Confirmed

A University at Buffalo researcher hopes this week to put into place the final piece of the puzzle for a never-before-quantified phenomenon in football.

After spending the past six years probing the physics of how a football travels during flight using computer simulations and the videotape of a single forward pass from a 1976 professional football game, the researcher is about to put the last piece into the puzzle.

Data from wind-tunnel testing, to be conducted on Wednesday (Aug. 22), together with numerical simulations developed by William J. Rae, Ph.D., should confirm a frequently observed, but never quantified, phenomenon in football, namely that a forward pass curves slightly to the left or right, based on the handedness of the passer.

Rae, SUNY Distinguished Teaching Professor in the Department of Mechanical and Aerospace Engineering in the UB School of Engineering and Applied Sciences, is a lifelong football fan who admits that his research has been a labor of love. He began studying the flight of footballs in 1995 when he was using the topic to introduce students in his flight dynamics class to the fundamental properties of aerodynamic flight.

He noted that while serious aerodynamic studies have been conducted on the flight of baseballs, soccer balls, golf balls and tennis balls, there have never been, to his knowledge, similar studies of footballs.

"That's surprising given the great popularity of this sport," said Rae, who in coming months will publish two scientific papers on his football-flight studies.

With funding provided by Wilson Sporting Goods and equipment purchased with funding from the National Science Foundation, the aim of Rae's research has been to address which way a football is pushed during a forward pass and with what forces.

In addition to his computer simulations, he has done detailed frame-by-frame analyses of the "Hail Mary" pass in the 1976 Dallas Cowboys vs. New York Giants game, information he uses thanks to the express written consent of the National Football League.

"The film gave me information on the time of flight, the distance the ball traveled and the spin-to-wobble ratio, that is, the number of times the ball spins versus the number of times it wobbles," said Rae.

To do his calculations correctly, he obtained architects' drawings of Giant stadium in East Rutherford, N.J., to accurately discern the geometry of the field, and to account for where the camera operator probably was standing during filming.

"These are not controlled conditions," Rae cautions, but based on the data from the film, he was able to deduce what the loads must be on the football, deductions he will confirm with the wind-tunnel experiments.

To do the experiments, Rae has outfitted the football with a strain-gauge balance, essentially a little motion sensor embedded in the football that measures loads, forces and torques on the football at different wind speeds.

The experiments will be done at Veridian Corp. in a low-speed wind tunnel that has been used to help members of the U.S. Olympic team improve their skills in downhill skiing and other winter sports.

Based on earlier wind-tunnel experiments he has conducted, Rae expects that the data he obtains in this week's tests, in conjunction with his numerical simulations, will confirm the interesting phenomenon he first observed with the 1976 videotaped pass.

"We expect to see an interaction between the gyroscopic and aerodynamic torques, which is what results in a slight curve to the right or left, depending on whether the passer is right- or left-handed," he said.

Rae's explanation for this phenomenon is that an interaction is occurring between the gyroscopic torque, which is present on any spinning body, and the aerodynamic torque, caused by wind rushing over the football, which blows harder on one end than the other.

"Nature wants to zero out the sum of those two effects," said Rae, "it wants to make the motion have no torque. The result is that the football swerves a few degrees to one side, thereby generating enough aerodynamic torque to cancel out the gyroscopic torque."

What effect will the scientific confirmation of this interaction have on the game?

"It probably will have no effect whatsoever on the game," Rae declared good-naturedly, "but in a sport where outcomes are decided on inches, who knows?"

The wind tunnel tests were made possible by the Calspan-UB Research Center, a non-profit organization formed by UB and Veridian Corp., to bring together scientists and engineers from academia and private industry to conduct joint research. - By Ellen Goldbaum

[Contact: Ellen Goldbaum]

21-Aug-2001

 

 

 

 

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