The road transport sector, a major consumer of global energy, relies predominantly on oil-based fuels and contributes significantly to greenhouse gas emissions. Enhancing fuel efficiency through improved vehicle aerodynamics is essential for sustainable mobility. However, crosswind disturbances compromise aerodynamic performance by increasing drag and rolling resistance, particularly for heavy-duty vehicles. This study investigates the impact of extreme crosswind on vehicle energy consumption and dynamic behaviour by considering driver steering response under extreme conditions at different delay times. A two-way coupled aerodynamic and vehicle dynamics simulation framework is employed to capture these interactions. The findings highlight the critical role of driver skills, i.e., prompt steering by driver effectively mitigates energy losses, whereas delayed or abrupt corrections exacerbate rolling resistance through pronounced tyre slip angles. For example, delayed steering response of the driver (e.g., 1.0 second delay) increases energy consumption by 77% when compared to 44% maximum increase for prompt steering of the driver. These results underscore the complex interplay between aerodynamic forces and driver-induced dynamics in shaping vehicle energy efficiency under crosswind conditions.

The general approach in the previous studies was to ignore the driver’s steering contribution to a vehicle while investigating the interactions between crosswind and vehicle. Therefore, the goal of this study is to find out how steering inputs by drivers affect a heavy-ground vehicle’s dynamic reaction to crosswinds. In the investigation, a two-way interaction between vehicle dynamics and aerodynamic simulations was employed. The steering inputs of drivers were modelled using a driver model taken from the previous literature that is able to reproduce the steering responses of a human driver. The study’s findings demonstrated that the steering inputs made by drivers significantly impacted how the vehicle responded to crosswinds. For instance, the greatest lateral displacement of the least skilled driver (Driver 1) was around 1.53 times the greatest lateral displacement of the most skilled driver (Driver 3) at the delay time of t_δ,delay = 0.5 s in the steering input. Additionally, the maximum lateral displacement results of Driver 1 and Driver 3 at t_δ,delay = 1.0 s became 1.39 and 1.56 times greater than their maximum lateral displacement results at tδ,delay = 0.5 s. Similarly, the total steering inputs of Driver 1 and Driver 3 at t_δ,delay = 1.0 s were 1.4 and 2.2 times greater than their total steering inputs at t_δ,delay = 0.5 s, respectively. In general, the results of a driver who is more skilled than Driver 1 (Driver 2) fall in between the respective results of Driver 1 and Driver 3. On the other hand, each driver’s total steering inputs at t_δ,delay = 0.5 s were roughly the same as their total steering inputs at t_δ,delay = 0 s. In all delay scenarios for the start of the driver’s steering inputs, the drivers’ steering inputs amplified the yaw moment applied to the vehicle. Meanwhile, they diminished the lateral force and roll moment.

The present study assesses the use of a two-equation eddy-viscosity turbulence model, which is a shear-stress transport (SST) k-ω turbulence model, in two-way coupled aerodynamics and vehicle dynamics simulation of a heavy ground vehicle subjected to crosswind. The obtained results are compared with the corresponding results of the improved delayed detached-eddy simulation (IDDES) conducted at similar conditions from the previous literature. The aim is to evaluate the effects of different turbulence models used in aerodynamics simulations to resolve the vehicle dynamics results in two-way coupled simulations. The results present that the absolute relative percent differences between the lateral displacement, yaw angle and roll angle results of the SST k-ω and the IDDES simulations are less than 1%, 3%, and 10%, respectively. As for the aerodynamics results, the absolute relative percent differences between the lateral force, yaw moment, and roll moment of the SST k-ω, and the IDDES simulations are less than 7.3%, 8.5%, and 10.0%, respectively. The results also show that the magnitudes of the lateral force, roll moment, and yaw moment are mostly increased due to the crosswind excitations among all other force and moment components. The yaw moment presents the fastest response to the crosswind excitations.

Ground vehicles often encounter turbulent flows with wide range of scales, e.g. crosswind gusts, when moving on-road conditions. Crosswinds can be considered as an important factor in heavy vehicle’s roll-over accident due to their relatively high center of gravity and lateral surface area. However, there are few studies which investigate effects of crosswinds on heavy vehicles. Furthermore, existing studies have generally focused on lateral or yaw dynamics of heavy vehicles and neglected their roll dynamics. Therefore, effects of crosswinds on heavy ground vehicles should be understood in all aspects in order to design less wind-sensitive vehicles especially at early stages of their design processes. Inherently, crosswind studies require a multidisciplinary approach which involves coupling between aerodynamics and vehicle dynamics. In the present study, investigation of effects of the coupling methods, e.g. one-way and two-way couplings, between aerodynamics and vehicle dynamics simulations are aimed by considering both lateral and roll dynamics of heavy vehicles which are subjected to crosswind gust. Vehicle dynamics and aerodynamics results are presented. Results of the one-way coupled simulations, in general, overestimate the absolute maximum values of the vehicle dynamics results. However, differences in lateral displacement results Δymax are less than 0.2 m for the studied case.

Improvements in vehicle technologies in recent decades enable the use of lighter materials and the development of control systems for autonomous vehicles. However, these improvements lead to a need for better understanding of how flow phenomena affect crosswind stability of ground vehicles which will enable the design of the less wind-sensitive vehicles. Therefore, the present study investigates the significance of roll on the dynamics of ground vehicles subjected to crosswind gusts. It includes a multidisciplinary approach in which there is a two-way coupled simulation between aerodynamics and vehicle dynamics equations. As a result of the investigations, significant differences have been found be- tween the computations considering no-roll and roll motions.

Crosswinds which stem from on-road flow conditions can deteriorate a ground vehicle's driving performance. In spite of the numerous studies investigating aerodynamics of the ground vehicles in the previous literature, there is still a need for thorough understanding of the underlying flow phenomena related to crosswind sensitivity of the ground vehicles. Therefore, the present study is aimed to investigate characteristics of the flow features around the ground vehicles under steady crosswind conditions within a range of yaw angles 0 degrees <= beta <= 15 degrees using the Ahmed vehicle model with rear slant angles of alpha = 25 degrees and 35 degrees. Throughout the investigations, flow visualizations using dye injection technique and velocity measurements using particle image velocimetry PIV technique are conducted. The Reynolds number of the flow which is based on the free stream flow velocity U = 200 mm/s and height of the model H = 72 mm is Re-H = 1.4 x 10(4). Results are presented in terms of time averaged vorticity <omega> contours and streamline <Psi> patterns together with velocity magnitude ((< u >(2)+ < w >(2))(1/2)/U) of the flow fields. Additionally, turbulence quantities such as Reynolds stresses < u'w' >/U-2 and turbulent kinetic energy TKE are presented and discussed in details. Results of the present study show that characteristics of the flow features in the near wake region downstream of the Ahmed model are very sensitive to the effects of the crosswind.