We’ve come a long way since the early days of analyzing airflow. Before the advent of wind tunnels and computerized simulations, automotive designers would tape small tufts of yarn, called telltales, on a car body in order to observe turbulence. While driving alongside, if they saw those snippets of woolen fringe wiggling too much in the wind, it was back to the drawing board. Crude, and only somewhat effective.
 In addition to wind-tunnel testing and on-track experience, Computational Flow Dynami
Much more recently, development of the new Corvette Stingray’s wind-cheating shape involved sophisticated CFD (Computational Flow Dynamics), leading up to lengthy hours of wind-tunnel testing. Computer-generated meshed models and “ribbons” have replaced those bits of yarn on a fullsize vehicle. These digital ribbons visually display the path of a single particle as it travels through and around the body. And this powerful analytic tool provides data on dozens of parameters—such as heat, velocity, and pressure coefficients—among many others, allowing for an unprecedented level of precision.
For instance, Corvette designers found through CFD that adjusting the shape of the side mirrors by as little as a single millimeter impacted the smoothness and direction of the airflow over the ’14 Stingray’s body, as well as through the rear ducts and spoiler. In addition, CFD analysis facilitated the design process, as it minimized the amount of time required for wind-tunnel testing. Even so, many hours went into evaluating airflow at speeds as high as 120 mph in the tunnel, and then 180 mph in a rolling road tunnel as a final check.
But the design of the new Corvette was not determined solely by digital readouts generated in a virtual setting, or in the controlled environment of a wind tunnel. As noted in last month’s feature on the design of the ’14 Stingray, the initial R&D on aerodynamics was derived from real-world experience on the track with the C6.R competition Corvette. One area in particular focused specifically on tilting the angle of the radiator forward, along with releasing air from the center of the hood. In this follow-up article in our series on the new Stingray, we’ll be digging into more detail on the interplay of drag and lift, along with other aspects of the arcane world of aerodynamics.
In addition to speaking with Kirk Bennion, the Corvette’s Exterior Design Manager, we gathered input from John Bednarchik, Corvette Lead Aerodynamics Engineer. A 15-year veteran who’s worked on a variety of Chevrolet vehicles, Bednarchik has degrees in mechanical engineering from both Lawrence Technological Institute and the University of Michigan, with special studies on fluid dynamics. While he notes that the primary reason for refining aerodynamics on Chevrolet vehicles in general is to improve fuel efficiency, the Corvette presented added challenges.
 Every surface of the Stingray was analyzed for airflow, including the vents in the si
As Bednarchik worked early on with Bennion to develop surfaces for the Stingray, “One of the big goals for the C7 was to enhance the lift performance,” he says. On the other hand, “We wanted the Cd [coefficient of drag] to be as low as possible.” Those are competing concerns, because as you reduce drag, lift increases. And conversely, as lift decreases and the car hunkers down, drag goes up. Balancing these two key elements more than doubled the amount of aerodynamic work, he notes.
Indeed, a critical question for each of the final five thematic, third-scale models of the seventh-generation Corvette was whether they hit the aero targets. If they didn’t, the team couldn’t move forward with them. Bednarchik didn’t specify what sort of design elements impede airflow, but he did allow that certain “more aggressive” styles either weren’t as slippery or created more lift.
“The new exterior is not just about styling,” Bennion confirms. In effort to create uniqueness, much of the shape was “aero driven, a sign of the times.” Partly because of the increase in amateur racing in recent years, the new Stingray had to be more track capable right off the showroom floor. So the airflow aspect had to not only reduce fuel consumption and optimize lift/drag characteristics, but also enhance several other areas such as brake and differential cooling.
Starting at the front, the leading edge of the front fascia needed to set up the airflow using a parabolic shape (as seen from the top down). “You really have to nail that front corner,” Bednarchik points out. In addition, the frontal area has to address multiple demands: lift/drag, noise levels, manufacturability, and even European pedestrian-safety requirements. Balancing this mix of competing concerns actually drives the entire process. Put another way, Bednarchik says his task as aerodynamic engineer for the C7 was, “To make it look good and still function—we gave Kirk what he needed.”