Coupled 6DoF Motion and Aerodynamics Simulation During Pass-By and Overtaken Motions

Abstract

Recently, unsteady aerodynamics has been drawing many attention because it is becoming clear that unsteady aerodynamics have a big effect on running stability, safety and ride comfort of vehicles. In order to estimate unsteady aerodynamics, it is necessary to reproduce the actual running condition including an atmospheric disturbance and vehicle motion. However, it is difficult to investigate the effect of unsteady aerodynamics in the road test because it has a lot of errors in measurement. In this study, a coupled simulation method between the 6DoF motion of a vehicle and aerodynamics was developed for these problems. Large Eddy Simulation (LES) was used to estimate the aerodynamics, and the motion equations of a vehicle was used to estimate vehicle motion. Vehicle motion in aerodynamic simulation was reproduced by using Arbitrary Lagrangian-Eulerian (ALE) method. In addition, sliding mesh method was used to reproduce overtaking and passing motions of two vehicles. By using the methods, aerodynamics and vehicle dynamics simulations are treated interactively (2-way) by exchanging each result at each time step. The 2-way results were compared with the 1-way coupled simulation estimating vehicle motion from aerodynamics results posteriori to investigate how vehicle’s motion itself further affects its aerodynamics during the pass-by and overtaking motions. Our main focus is, by using this method, to study the effect of unsteady aerodynamics on the running stability of a vehicle. The results of 1-way and 2-way coupling analysis showed difference with respect to behavior of a vehicle. It is believed that such differences result in the different aerodynamic forces and moments, which is caused by the vehicle’s posture changes in the 2-way coupling simulation.

Investigation of vehicle stability under crosswind conditions based on coupling methods

“…However, in their model, the aerodynamic force is passed non-directionally to the MBD model to conduct the simulation, which is also known as a one-way coupling method. 10 To a certain degree, one-way coupling methods are feasible and economical. 11 However, when the one-way coupling method is used, the vehicle orientation changes significantly as it is confronted with a large lateral aerodynamic force.…”

Aerodynamic drag change of simplified automobile models influenced by a passing vehicle

“…In previous studies, wind tunnel tests using two vehicle models were conducted, and the effects of the forces on vehicle motion were examined based on the obtained variations in aerodynamics (Noger, 2005;Yamamoto et al, 1997). The unsteady aerodynamic characteristics affected by other passing vehicles were also investigated using numerical simulations (Ishioka et al, 2015;Uystepruyst and Krajnović, 2013). The importance of two-way coupling analysis was highlighted considering the coupling of vehicle motion and aerodynamics.…”