# Superbowl DeflateGate Scandal Debunked Using Engineering Simulation

You can’t turn on the news without hearing about the latest scandal to hit the sports industry. The New England Patriots — the National Football League (NFL) team that faces the defending champ Seattle Seahawks in Super Bowl XLIX this Sunday — are under pressure (pun intended) for using under-inflated footballs when they routed the Indianapolis Colts in the recent AFC championship that decided who would go on to the Super Bowl. One of the theories around DeflateGate is that a softer, less inflated ball will deform more when grasped, making it easier to hold. This could make for a more consistent pass, or a softer catch.

So, as simulation experts, what can we add to the national dialogue? Good question!

We used our new ANSYS AIM multiphysics simulation environment to do analysis on a football structure inflated to 12.5 psi and 10.5 psi — the two pressures in question. Then, we modeled the pressure points of a human hand on the exterior of a football that represents a throwing configuration and force. This allowed us to simulate the difference in deformation that a 2 psi pressure would create. The result? Not much. The difference in deformation between the two pressures was less than 1 mm, keeping the quarterback’s “squeeze” imprint at roughly 5 millimeters. The same applied to the receiver’s catch. In the world of players wearing tacky, rubberized football gloves, the “softness” difference is negligible.

Now, let’s say Tom Brady is throwing a pass to Rob Gronkowski who is being covered by Richard Sherman. What makes the difference in whether the high-stakes pass is a first-down or an interception? Drag.

We modeled the axis of a perfectly thrown, tight spiral football against one that wobbled slightly on its axis – in other words, a poor pass. On the aerodynamics of a ball in flight, our simulations showed that a spiral that’s off axis by only 10 degrees — just 10 degrees — will increase the drag by more than 20 percent, taking as much as a few yards off a long pass.

So, what’s our thesis? Throwing a tight spiral always matters but, the football pressure over the range in question doesn’t impact the game.

That’s what simulation teaches us about the realities of DeflateGate. And, yes, ANSYS is based outside Pittsburgh which makes us Steelers fans. So we may have a thing against the Patriots. But, the truth is real and simulation helps us see the facts.

Here’s a quick look at the simulation.

This entry was posted in Sports & Consumer Goods, Systems Engineering and tagged , , , , by Barry Christenson. Bookmark the permalink.

Director of Product Management for ANSYS Inc. The product management team is responsible for planning the product capabilities of new releases as well as marketing the capabilities of current products. Prior to joining ANSYS Inc. in May 2000, Barry worked at Delphi Automotive Systems since 1987 in various engineering and project management roles related to automotive emission control systems for Latin American markets. Barry holds a B.S. in Mechanical Engineering from North Dakota State University, Fargo, North Dakota and a M.S. in Mechanical Engineering from Kettering University, Flint, Michigan.

## 11 thoughts on “Superbowl DeflateGate Scandal Debunked Using Engineering Simulation”

1. “But, the truth is real and simulation helps us see the facts.”

Umm, but in your drag calculation you did not mention anything about the turbulence model. So what’s the Reynolds number? And, is it a RANS, LES, DES, DNS calculation? And, how is the texture of the ball modeled?

As we know in the world of simulation, the devil is in the details. And, by turning a knob, one can sometimes get many different answers.

2. This is a red herring. It’s accurate facts, but irrelevant to the discussion.

This isn’t about catching and drag (of course in perfect conditions would be crucial), it’s about BALL CONTROL AFTER the handoff or catch. A squisher football is harder to dislodge -especially when slippery.

This debunked nothing, but was still a fun read.

• Actually, they addressed that in the 1st analysis – difference in ball deflection with the same grip results in <1mm with the change in pressure. They did not, however, specify pressures used, but the point is that if ball deflection is so small, then ball control should not be substantially changed and you probably aren't getting much more difficult to dislodge with that kind of deflection, either.

3. Questions: So which are the forces for each pressure to have same displacement or pressure hold by hand? On a throwing configuration and force.
Which are frictional force comparison between analysis on a football structure inflated to 12.5 psi and 10.5 psi? On a throwing configuration and force.
Which are the displacement and de-acceleration comparison when a receiver’s catch hold a football structure inflated to 12.5 psi and 10.5 psi on a same specific velocity?

4. Can someone confirm how much analysis was done in Lebanon, NH. The people in New England don’t think the Patriots cheated…wow…Mind Blown.

5. Well said Martin. Simulation are not fact they just mearly a good approximation. Better approximations means less assumptions and more realistic physics captured. It can never be 100% (fact), can be 99.9% that still doesn’t qualify it to be a fact.

6. I have a more difficult question, posed to me by a coworker … what keeps a thrown football’s nose pointing more or less along it’s trajectory (even when the trajectory is highly curved, such as when throwing a “bomb”).