CFD Analysis on the Aerodynamic Characteristics of Small-Sized Car Vehicles Under the Influence of Steady Crosswind

Abstract

One of the factors that can cause road accidents is the crosswind. Crosswind is defined as the side force which causes a vehicle to be unstable and allow the vehicle to deviate from its desired path.  This article is focusing on assessing the flow behaviour and aerodynamic loads that affect vehicle stability when the car is moving under the influence of steady crosswind. In this study, a numerical approach is performed in which ANSYS Fluent software is utilized as a platform to run the simulation. In this research, the crosswind flow angle (Ψ) is varied from 0° to 90°. The incompressible flow surrounding the vehicle is solved using the Reynolds-averaged Navier-Stokes (RANS) equations in conjunctions with the k - ε turbulence model. The Reynolds number is utilised depending on the velocity of the vehicle which are 2.76×10⁶ for high Reynolds number and 7.23×10⁵ for low Reynolds number respectively. In the results, it was found that the crosswind has a significant impact on the aerodynamics quantitatively and qualitatively. In term of aerodynamics load, as the crosswind yaw angle increase, the side coefficient (C_s) increases as well. When the crosswind yaw angle (Ψ) increases to 60°, it occurs a significant drop then remain almost constant when crosswind yaw angle is at 90°. In flow structure perspective, when the crosswind yaw angle increase, the vortex formation on the leeward region becomes larger, hence increase the imbalance of vehicle stability. Lastly, there is no substantial difference between the aerodynamics quantitative characteristics of the high Reynold number and the low Reynold number.