Coupled Analysis of Unsteady Aerodynamics and Vehicle Motion of a Passenger Car in Crosswind Condition

Abstract

High-speed passenger car requires a lighter weight for improving power performance and reducing fuel consumption; a car with higher-speed and lighter weight will lead to the passenger car more sensitive to the crosswind, which will affect the stability and drivability of the passenger car. This study employs the fully-coupled method to investigate a passenger car subjected "1-cos" crosswind with consideration of the vehicle motion. Large eddy simulation (LES) and dynamic mesh is adopted to investigate the unsteady aerodynamic, and the vehicle is treated as a three-freedom-system and driver's control is considered to investigate the vehicle dynamic. The one-way simulation and quasi-steady simulation are also conducted to compare with the fully-coupled simulation. The results of the three simulation methods show large difference. The peak value of the lateral displacement in fully-coupled simulation is the smallest between the three simulation approaches. While the change of aerodynamic loads and vehicle motion in fully-coupled simulation is more complicated than in one-way and quasi-steady simulation. These results clearly indicate the significance of including of the unsteady aerodynamic loads in passenger car moving analysis.

Coupled analysis of vehicle stability in crosswind on low adhesion road

“…The vehicle model studied in this paper is a 1:1 model of real vehicle, as shown in Figure 2, which we have ever used in a previous study (Huang et al, 2017a(Huang et al, , 2017b. The length of the vehicle is L = 4.587 m and the height is H = 1.467 m, while the width is W = 1.799 m. The frontal projection area of the vehicle is 2.06 m 2 .…”

“…where C S is the model coefficient, which is set to be 0.1 according to the research of Huang et al (2017aHuang et al ( , 2017b, D denotes the filter width and f d is expressed by the Van Direst damping function as follows: Vehicle stability in crosswind…”

“…The crosswind in this paper is a resultant velocity of Vx and Vy, which is used at the left boundary and front boundary of the computational domain, respectively, as shown in Figure 5(a). The velocity of main stream direction Vx is 30 m/s, which is equal to vehicle (Efraimsson, 2011) is used, and the maximum of the crosswind present in this paper is 15 m/s (Huang et al, 2017a(Huang et al, , 2017b, generating a great yaw angle of approximately 27°. As shown in Figure 5(b), the ramp up and down time corresponds to 1.5 vehicle lengths (Hassan Hemida, 2009).…”

“…Carbonne et al (2016) study the vehicle stability by two-way coupling, and compare the sensitivity of different vehicle styles exposed to a crosswind and also investigate the driver model in crosswind with the two-way coupling approach (Winkler et al, 2016). Huang et al (2017aHuang et al ( , 2017b investigate the necessity to conduct the two-way coupling with a 3-DOF vehicle model in crosswind. Favre et al (2016) use the 12-DOF vehicle dynamic model coupled with detached eddy simulation.…”

Numerical investigation for the influence of the car underbody on aerodynamic force and flow structure evolution in crosswind

“…5,6 Aerodynamic lift is sensitive to airflow distribution around the car underbody. However, most works under crosswind condition had been confined to a simplified model which did not consider the effect of underbody details on aerodynamic force, [7][8][9][10][11] and the influence of underbody structure under no-crosswind is such that it changed flow field, which could be lead to the aerodynamic force changing. For example, Gorre et al 12 showed that there was a considerable air resistance due to underbody components.…”