Numerical Simulation of Class 8 Tractor Trailer Geometries and Comparison with Wind Tunnel Data 2024-01-2533

This article analyzes the aerodynamic performance of Class 8 tractor-trailer geometries made available by the Environmental Protection Agency (EPA) using CFD simulation. Large Eddy Simulations (LES) were carried out with the CFD package, Simerics-MP+. A Sleeper tractor and a 53-foot box trailer configuration was considered. The configuration featured a detailed underbody, an open-grille under-hood engine compartment, mirrors, and the radiator and condenser. Multiple tractor-trailer variants were studied by adding aerodynamic surfaces to the baseline geometries. These include tank fairings and side extenders for the cabins, two types of trailer skirts, and a trailer tail. The effect of these devices towards reducing the overall vehicle drag was investigated. Mesh generation was carried out directly on the given geometry, without any surface modifications, using Simerics’ Binary-Tree unstructured mesher. Subsequently, simulations were setup considering realistic driving conditions with lateral wind, rotating wheels, and moving floor. The obtained numerical results were then compared with wind-tunnel test data, which highlighted the excellent predictive capabilities of the simulations. These accurate results, as presented in this paper, demonstrate the feasibility of using high fidelity simulation as a tool in the EPA’s SmartWay Verification Program.