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Development of new, competitive vehicles in the context of stricter regulations to reduce greenhouse gas emissions and increase fuel economy is driving OEM of commercial vehicles to further explore options for reducing aerodynamic drag in a real-world setting. To facilitate this in regards to the aerodynamics of a vehicle, virtual design methods such as CFD are often used to compliment experiments to help reduce physical testing time and costs. Once validated against experiments, CFD models can then act as predictive models to help speed development. In this paper, a wind tunnel experiment of a Class 8 truck is compared to a CFD simulation which replicates said experiment, validating the CFD model as a predictive tool in this instance. CFD is then used to evaluate the drag and flow around the vehicle in an open road scenario, and the results between the open road and wind tunnel scenarios are compared.

Recent regulations on greenhouse gas (GHG) emission standards for heavy-duty vehicles have prompted government agencies to standardize procedures assessing the aerodynamic performance of Class 8 tractor-trailers. The coastdown test procedure is the primary reference method employed to assess vehicle drag currently, while other valid alternatives include constant speed testing, computational fluid dynamics (CFD) simulations, and wind tunnel testing. The main purpose of this paper is to compare CFD simulations with a corresponding 1/8th scale wind tunnel test. Additionally, this paper will highlight the impacts of wind tunnel testing on the total drag coefficient performance as compared to full scale open road analysis with and without real world, upstream turbulence wind conditions. All scale model testing and CFD simulations were performed on a class 8 tractor with a standard 53-foot dry-box trailer. The wind tunnel testing was performed in the Auto Research Center (ARC) wind tunnel.

Simulation of passenger compartment climatic conditions is becoming increasingly important as a complement to wind tunnel and field testing to help achieve improved windshield de-icing performance while reducing vehicle development time and cost. Windshield de-icing simulation involves not only geometric complexity but also interactions between airflow and two modes of heat transfer, namely, heat conduction and convection. In the present study, CFD is employed to numerically simulate windshield de-icing performance. The general-purpose CFD package Fluent is used to perform the numerical simulation. Two CFD analysis methodologies, windshield de-icing pattern analysis and windshield de-icing process analysis, are discussed. The validation is presented by comparing the CFD predicted windshield de-icing patterns with windshield de-icing tunnel test. The present full 3-D CFD windshield de-icing simulations demonstrated reasonable agreement with available tunnel test data.