In June, Windshear, a subsidiary of Haas Automation Inc., will open just the third full-scale rolling road wind tunnel in the world and the first of its kind in North America. Perhaps more notable is the fact that the facility is also set to become the only commercially available wind tunnel of its type in existence.
Located in the NASCAR hotbed of Concord, NC, Windshear will operate continuously and be available to all motorsports teams and auto manufacturers. According to Site Manager Jeffrey Bordner, interest in the facility has been expressed by “every racing series that’s out there” as well as some production vehicle manufacturers.
As of early May, the company had sold more than 80% of its available time for a one-shift operation for the remainder of the year. Shifts are sold in 10-h segments with an hour on either side, allowing for the potential of two 12-h shifts per day. Bordner expects to expand to a two-shift operation by the end of the year to accommodate the heavy interest.
What makes this wind tunnel so unique is that it conducts testing using a single belt, thereby avoiding the development of a boundary layer during testing, which can skew results.
“With air moving through a closed duct, there’s a frictional loss of the air velocity at the walls of that ductwork,” Bordner said. “The walls and the ceiling in the case of a wind tunnel don’t matter, but on the ground the boundary layer is an issue because the vehicle is sitting on the ground. Out in the real world, you don’t have that because it’s not the wind moving in relationship to the vehicle and the facility, it’s the vehicle moving in relationship to the air and the ground. The ground and the air have the same relative velocity.”
While some wind tunnels have made modifications to remove or limit the boundary layer, such as suction slots, blowing slots, and perforation plates, the single-belt approach is the only way to replicate real-world conditions with respect to the boundary layer, according to Bordner.
The 10.5- x 29.5-ft (3.2- x 9.0-m) rolling road is an MTS Single Belt FlatTrac system that uses a continuous steel belt just 1 mm (0.04 in) thick to simulate the road beneath a racecar or traveling on a speedway. The rolling road is capable of accelerating from 0 to 180 mph (0 to 290 km/h) in less than 1 min.
The belt is designed to last up to 5000 operational hours, during which time a vehicle continuously on the belt would travel 300,000 to 400,000 km (186,000 to 248,000 mi). During testing, “through-the-belt” sensors measure the aerodynamic downforce under each tire.
The facility’s wind tunnel provides constant air speeds up to 180 mph by way of a 22-ft (6.7-m) diameter fan and 5100-hp (3805-kW) motor. The air in the wind tunnel flows from the fan to the vehicle, then is collected and returned to the fan in a closed circuit.
Temperatures within the facility are controlled to within 1ºF (0.6°C) by a heat exchanger to maintain a constant temperature of 75°F (24°C), which prevents having to correct for a density change.
“As air temperature changes, density changes, and the density affects the forces that are imparted on the vehicle due to the airflow around it,” Bordner said. “Here in the South, it can be rather chilly in the morning and very warm in the afternoon; that becomes an issue. Also, the fact that we’re running at such high speeds, there’s a lot of heat that comes from the motor. We have to be able to account for that as well.”
Bordner joined Windshear in October 2007 after 17 years with Chrysler LLC, where he was most recently the Manager of Aerodynamics and Body Design for all Dodge and Mopar motorsports programs. In this role, he was responsible for aerodynamic development and body design of high-performance and racing vehicles, including NASCAR Nextel Cup and Craftsman Truck, NHRA Funny Car & Pro-Stock, and SCCA Speed World Challenge GT race programs, as well as all high-performance production vehicles bearing the SRT badge.