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This paper talks about using an approach to simulate snow mass falling from roof of cab on the cowl tray of a commercial truck and predicting the durability life of the cowl tray based on this loading. It has always been a challenge for analysts to model the behavior of snow/slurry in dynamic simulations especially where the area of concern is structure and not the fluid. The conventional approach followed in most industries would be either to model snow as soft rubber or to divert from the conventional Lagrangian algorithm for mesh movement towards Eulerian method (or ALE algorithm). Although modeling snow as soft rubber captures the basic physics of the problem, it is not able to correctly simulate the fluid structure interaction behavior and the pressure wave movement inside the snow/slurry when it comes in contact with the structure.

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.

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.

Wobble and shimmy vibrations are commonly observed in commercial highway vehicles with solid-beam front axles. These vibrations are typically self-excited and manifest themselves as sustained oscillations about the kingpin and axle tramp. A study was initiated to investigate and quantify wobble and shimmy behaviors, with a primary focus on wobble. A cross functional team including test and simulation engineers evaluated a vehicle exhibiting these behaviors. The team developed an ADAMS model to reproduce the behaviors and developed a DOE to quantify the impact of variables and combinations of variables. The evaluation demonstrated that dynamic imbalance in the rotating masses is a primary source of excitation. Wheel run-out, caster angle, tire brand, tire wear and tire inflation are also significant sources. Future studies will use these findings to mitigate the concern.

Recent regulations on greenhouse gas (GHG) emission standards for heavy duty vehicles have prompted government agencies to standardize procedures to assess aerodynamic performance of Class 8 tractor-trailers. The coastdown test procedure is the primary reference method to assess vehicle drag and other valid alternatives include wind tunnel testing and computational fluid dynamics (CFD) simulations. While there have been many published studies comparing results between simulations and wind tunnel testing, it is less well understood how to compare results with coastdown testing. Both the wind tunnel and simulation directly measure aerodynamic drag forces in controlled conditions, while coastdown testing is conducted in an open road environment, aerodynamic forces are calculated from a road load equation, and variable wind and vehicle speed introduce additional complexity.