Through its ecoTECHNOLOGY for Vehicles (eTV) Program, Transport Canada has commissioned a study to investigate safety implications of using boat-tails for the drag reduction of heavy-duty vehicles (HDVs) on Canadian roads. A wind tunnel study was carried out in 2012 to investigate the dynamic wind loads experienced by passenger vehicles travelling in the wake of a boat-tail-equipped HDV. Two passenger-vehicle models, representing a compact car and a sport utility vehicle, were placed in the wake of a 1/10-scale tractor + dry-van-trailer model and the dynamic wind loads experienced by the vehicles were measured with and without different combinations of boat tails and side skirts. The results of this study have shown that the addition of a boat-tail to the base of an HDV trailer can increase the dynamic wind loads related to directional stability of a following vehicle.
This report presents the results of vehicle-dynamic simulations using the wind loads measured in the wind tunnel as an input to evaluate the impact on the directional stability of the vehicle.
The simulations were performed using the SIMPACK Automotive model software which is a suitable tool used for vehicle-dynamic analysis. The cases that have shown the largest amplification of the dynamic wind loads in the wind tunnel, especially for the side force and yawing moment, were selected to evaluate the impact on vehicle stability. For this study, the influence of road-friction and driver-response were additionally varied to identify any scenarios in which the presence of a boat-tail-equipped heavy vehicle may influence the stability of the vehicle in the wake.
This study revealed that the amplified wind loads, as measured on a vehicle following a tractor-trailer equipped with a boat-tail, did not adversely influence the lateral stability of the vehicles studied. This conclusion is mainly based on the results obtained for the lateral deviation and the wheel reaction force and their limit values as defined in this report.
The full report can be found at: http://nparc.cisti-icist.nrc-cnrc.gc.ca/eng/view/object/?id=06a32771-be7e-4264-8055-0900dc6a3082