Tunnel Test: Freightliner shows off mirror aerodynamics in wind tunnel

WASHINGTON — If you’ve never driven through the eye of a hurricane, Freightliner can show you how it feels — and how much fuel it’ll cost you too.

North America’s largest truckmaker, in collaboration with the U.S. Department of Energy (DOE), recently completed a comprehensive two-year study on the impact of aerodynamics on fuel efficiency. Utilizing a new custom-built wind tunnel facility, Freightliner engineers conducted a study that has produced specific design guidelines to benefit all existing and future heavy-duty trucks operating on North America’s highways, the company says.

Even small improvements in a truck’s aerodynamic design can
save millions of gallons of fuel for fleets researchers find

Last week, Freightliner LLC — along with other OEM participants — provided details of their study to stakeholders and DOE officials.

“We built our Class 8 wind tunnel — the first and only of its kind — specifically for this type of research because it allows our engineers to replicate real-world aerodynamic scenarios in a controlled environment where we can precisely duplicate test conditions to evaluate even the slightest effects on aerodynamics,” said Elmar Boeckenhoff, senior vice-president of engineering and technology for Freightliner LLC.

“The variables of driver influence, weather conditions, road surfaces, and traffic, to name a few, are overcome in the wind tunnel. The flexibility provided by having the wind tunnel at our disposal enables us to evaluate many different scenarios in a very timely and cost effective manner.”

Research has shown that even small improvements in a truck’s aerodynamic design can save millions of gallons of fuel when applied to fleets. This is one of the reasons, the company says, why Freightliner chose to conduct a comprehensive study of the influence and impact of mirror-mounting systems on total vehicle aerodynamics. Without the wind tunnel, subtle changes in the mirror designs may not be recognized with traditional over-the-road testing.

“When you add it all up, we have the potential to make very significant aerodynamic improvements to our vehicles,” Boeckenhoff says.

Today’s best-designed mirrors can affect vehicle aerodynamics
by as much as 6 percent or more, according to Freightliner

Scott Smith, executive engineer for Freightliner LLC, was the project leader for Freightliner’s aerodynamics evaluation. “We focused our study on mirrors and mirror systems because our testing resources, such as the wind tunnel and Computational Fluid Dynamics (CFD), lend themselves to measuring relatively small aerodynamic changes,” he said.

Using the Freightliner wind tunnel and CFD analysis, engineers outfitted a Freightliner Century Class S/T tractor with several configurations of mirrors and conducted 11 different iterations to analyze how much each mirror style affected the truck’s overall aerodynamic drag.

They then analyzed the information collected and concluded What that the data can be used to identify sources of aerodynamic drag and conceive future designs that will be incorporated on new Freightliner LLC vehicles.

It was also learned that even today’s best-designed mirrors can affect vehicle aerodynamics by as much as 6 percent or more, depending their design and placement on the truck. It’s not just the mirror shape, but the placement on the truck and even the shape of the truck in the vicinity of the mirror that affect the efficiency of the airflow, the company says.

“Freightliner LLC’s unique testing resources have not only let us consider updates we can make to our own products, but also enable us to propose design recommendations for industry-wide fuel efficiency improvements,” said Smith.

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