Chevrolet Impala Ss to Debut in Bristol

By: Noah Scott

The Chevrolet Impala SS has made its debut at the NASCAR Nextel Cup Series. And of course with its launching is the unveiling of the GM Racing's all-new R07 small-block V-8 racing engine which provides a glimpse to the new direction in technology that America's most popular racing series is heading.

One of the most powerful element in GM Racing's toolbox is what the automaker calls as the CFD or the Computational Fluid Dynamics which is a mathematical simulation of the airflow around a vehicle. This new CFD technology is influencing the design of both racing and production automobiles. CFD also played an important role in GM Racing's analysis and development of a racing version of the Impala SS which is considered as the new generation NASCAR race car that will make its debut in a competition that will be held in Bristol, Tennessee scheduled on March 25, 2007.

According to Kevin Bayless, GM Racing oval track chassis/aero program manager, "The best way to describe CFD is a wind tunnel in a computer. CFD is a simulation that predicts the aerodynamic forces acting on a vehicle using computational methods rather than physical measurements. CFD allows engineers and racing teams to evaluate the effects of aerodynamic changes quickly on a computer screen rather than in a conventional wind tunnel."

The CFD technology was first developed for aerospace and defense usage however it migrated to the civilian sector as supercomputers which became available to manipulate complex programs. "The CFD software requires a supercomputer because the number of calculations is immense. Foe example, our aerodynamic models typically have more than 10 million discrete data points that are used to calculate the force. It really is rocket science," explained Bayless.

"The computing time required to run CFD programs is a limitation even with a supercomputer," Bayless noted. "A team can run through more tests in a day in a wind tunnel than can be done with CFD. At this point in its development, CFD supplements the testing that's done in wind tunnels and on race tracks. We share the information that GM Racing obtains through CFD with the Chevy teams. Given the level of competition in NASCAR today, it's vital for every team."

Although the price that is involved in this type of technology is high but the benefits of CFD are worth it. The highly advanced software makes it possible to see the invisible movement of air over the vehicle's body.

Bayless said, "CFD allows us to visualize the flow to understand what the air is doing and where the aerodynamic forces are being generated. That's simply not possible with a model or a full-size vehicle in a wind tunnel. CFD also allows us to test aerodynamics without a physical model, which can be helpful in the early stages of a design. We can analyze and compare various alternatives before actually building a prototype vehicle."

Aside from the Impala SS becoming the new NASCAR race car of today it will be Chevrolet's high-profile entry in Nextel Cup competition. The CFD played an important role boosting the identity of Chevy's new on-track representative.

"Although the Car of Tomorrow is highly regulated, it's not a spec race car. As a manufacturer, Chevrolet was able to define many of the details that separate the Impala SS from our competitors' cars. The headlights, grille, portions of the hood, and the tail were areas where GM Racing was able to incorporate Impala SS styling cues and brand identity. These areas are now fixed as part of the NASCAR Impala SS package," added Bayless.

The Impala SS is entirely different from the Monte Carlo SS in terms of aerodynamics but also similar in some ways like both are equipped with quality GM auto parts like the high quality which are responsible for converting fuel into energy that powers the vehicle. For the Impala SS GM engineers have employed CFD to better understand the effects of the new body shape, front splitter, and adjustable rear wing on aerodynamic performance. "NASCAR specifications require the Impala SS to be wider and taller than the Monte Carlo SS that it is replacing, so its frontal area is larger and its aerodynamic drag is approximately 10 percent greater. Initially the Impala SS will have about 15 percent less downforce than the Monte Carlo SS, which has been highly refined over the years. The change from a spoiler to an adjustable rear wing appears to reduce turbulence in the wake of the car, so when two cars are running nose-to-tail, the less turbulent air behind the first car should alleviate some of the aerodynamic push experienced by the trailing car," explained further by Bayless.

It is also important to note that although the CFD is a powerful engineering tool it is not designed to replace the conventional wind tunnels and track testing.

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