Coupling analysis of transient aerodynamic and dynamic response of articulated heavy vehicles under crosswinds

Abstract

Vehicle aerodynamics and dynamics in gusty crosswind conditions are of increasing significance for the lateral stability of heavy ground vehicles, especially articulated heavy vehicles (AHVs). The unsteady aerodynamic loads acting on AHVs can greatly exceed loads of a single-vehicle unit; these may deteriorate the lateral stability and lead to a loss of handling control. In this study, the time characteristics of aerodynamic loads and dynamic response of a tractor semi-trailer were considered, based on simulating the relative motions of these two components to reproduce actual scenarios of AHVs in crosswinds. A dynamic fully coupled method was developed and adopted to realize a real-time data exchange of flow fields and multi-bodies. Two multi-body systems (for non-articulated heavy vehicles and AHVs, respectively) were created to study the influences of the relative motions on the aerodynamic performance and lateral stability of the vehicles. The Reynolds-averaged Navier-Stokes (RANS) method and renormalization group (RNG) k - ϵ equation were adopted to account for the turbulence. A wind tunnel experiment was conducted to validate the numerical method. The results show that AHVs are more sensitive to the crosswind, with significant differences in the magnitudes and directions of the aerodynamic forces, moments, dynamic yaw angle, and lateral displacement. Three different wind types were considered (step, linear, and sinusoidal). The step crosswind produces the largest average lateral force and yawing moment, resulting in the largest lateral displacement and yaw angle. The largest hitch angle is found for linear gusts, presenting the highest safety risks in regard to jackknifing and trailer swings.