Computational Fluid Dynamics Model Creation and Simulation for Class 8 Tractor-Trailers 2023-01-5051

The Environmental Protection Agency (EPA), in partnership with Research Triangle Institute (RTI International) and Auto Research Center (ARC-Indy), have created digital geometries of commercially available heavy-duty tractor-trailers. The goal of this effort was to improve the agency’s understanding of aerodynamic modeling of modern trucks and to provide opportunities for more consistent engagement on computational fluid dynamics (CFD) analyses. Sleeper and day cab tractors with aerodynamic features and a 53-foot box trailer with aerodynamic technology options were scanned to create high-resolution geometries. The scanning process consisted of a combination of physical scanning with a handheld device, along with digital post-processing. The completed truck geometries are compatible with most commercial CFD software and are publicly available for modeling and analyses. With the ability to change specific tractor and/or trailer aerodynamic features, CFD software can be used to calculate total tractor-trailer aerodynamic drag as well as changes in drag associated with tractor and/or trailer modifications. Preliminary CFD simulations of these geometries were compared to current and future U.S. EPA aerodynamic bins for heavy-duty tractors. Changes in drag associated with trailer modifications were evaluated and removal of tractor aerodynamic fairings were demonstrated to increase drag. Overall, the CFD simulation data showed that the drag values from these geometries were within the range of expectations for this type of tractor-trailer combination. Likewise, drag changes from adding or removing the aerodynamic fairings or devices were also in line with expectations and good engineering judgment.