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.