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Tire aerodynamics has long been viewed as a critical area in the ongoing research on vehicle drag reduction as it is a significant contributor to the overall automotive parasitic drag. Previous wind-tunnel experiments have revealed that the flow over a rotating wheel is a very complex phenomenon. This complexity arises from the tire-ground contact patch, various points of flow separation due to the wheel geometry, and the effects of wheel rotation. These aspects make the numerical simulation of this type of flow rather challenging. Existing literature shows a number of ways, like sliding mesh, by which to simulate the flow over an isolated wheel, but the problem of finding an accurate yet cost-effective solution still remains elusive. The current paper attempts to investigate the different methodologies to emulate the wheel motion. In addition, the paper will address the influence of mesh parameters and solver setting dependency of the solution.

Faster turn-around times and cost-effectiveness make the Reynolds Averaged Navier-Stokes (RANS) simulation approach still a widely utilized tool in racecar aerodynamic development, an industry where a large volume of simulations and short development cycles are constantly demanded. However, a well-known flaw of the RANS methodology is its inability to properly characterize the separated and wake flow associated with complex automotive geometries using the existing turbulence models. Experience suggests that this limitation cannot be overcome by simply refining the meshing schemes alone. Some earlier researches have shown that the closure coefficients involved in the RANS turbulence modeling transport equations most times influence the simulation prediction results.

Turbulence modeling and the specific boundary conditions are among the two major simulation physics setup variables that affect the prediction veracity of a CFD simulation. The existing literature is rich with studies investigating the effect of the inlet boundary conditions on the predictability of a CFD simulation, and it is recognized that the turbulence characteristics of the freestream flow, viz. the turbulence intensity and length scale, can impact the simulation results significantly, even with the same turbulence model. However, none of these studies encompasses the significance of these two boundary specifications on the CFD analysis of a realistic racecar model. Against this backdrop, the purpose of this study is to systematically investigate the effect of different freestream turbulence specifications on the CFD predictions of the aerodynamic characteristics of a latest generation NASCAR Cup racecar model.

Cost benefit and teraflop restrictions imposed by racing sanctioning bodies make steady-state RANS CFD simulation a widely accepted first approximation tool for aerodynamics evaluations in motorsports, in spite of its limitations. Research involving generic and simplified vehicle bodies has shown that the veracity of aerodynamic CFD predictions strongly depends on the turbulence model being used. Also, the ability of a turbulence model to accurately predict aerodynamic characteristics can be vehicle shape dependent as well. Modifications to the turbulence model coefficients in some of the models have the potential to improve the predictive capability for a particular vehicle shape. This paper presents a systematic study of turbulence modeling effects on the prediction of aerodynamic characteristics of a NASCAR Gen-6 Cup racecar. Steady-state RANS simulations are completed using a commercial CFD package, STAR-CCM+, from CD-Adapco.

Published information on studies of something so critical to safety as passenger vehicle tire pressures can be found [1, 2]; however, they only account for rolling tires. Studies related to spare tire pressures are lacking. This paper is the result of measurements on 150+ vehicles and the most surprising results are presented regarding the influence of Tire Pressure Monitoring Systems (TPMS) and the new spare tire locations and use. A statistical study was performed on the collected data to determine the correlation between tire pressures, vehicle age and TPMS. One particular topic of investigation was the relationship between various factors that influence spare tire pressure. Some newer models, particularly some mini-vans, have placed the spare tire in an unusual and inconvenient place for regular maintenance. Based on the data collected, TPMS has a positive influence on rolling tires but not on spare tires. The results support the need for TPMS to also monitor spare tire pressures.

The radiator is the key component of a vehicle’s cooling system. The cooling effectiveness of a radiator largely depends on the flow of fresh air through it. Thus, at high vehicle speeds, the mass flow rate and flow-distribution or flow-uniformity over the radiator surface are the major operating parameters influencing the performance of a radiator. Additionally, the mass of air coming from the front grille plays an important role on the total drag of the vehicle. This paper presents computational studies aiming at improving simultaneously the efficiency of a radiator and reducing the total drag of the vehicle; this is achieved using passive aerodynamic devices that alter the flow pattern approaching the radiator. The vehicle model considered is a Hyundai Veloster and all analyses were carried out using a commercial CFD code Star-CCM+ version 10.04 by CD-adapco.