Through its ecoTECHNOLOGY for Vehicles II (eTV II) program, Transport Canada has commissioned a study to investigate the potential safety implications of using boat-tails to reduce fuel consumption and greenhouse-gas emissions from heavy-duty vehicles (HDVs) on Canadian roads. A concern has been raised regarding the possibility for ice and snow to accumulate and shed from the cavity of a boat-tail, posing a potential safety hazard for other road users. This report describes a preliminary evaluation for the potential for ice and snow accumulation in the cavity of a boat-tail-equipped HDV.
A 2012 report to Transport Canada, prepared by the National Research Council Canada (NRC), identified no relevant scientific literature on the topic of ice or snow accumulation in cavities at the rear of a ground vehicle. The report identified that on-road observations, wind tunnel testing, or computational fluid dynamics (CFD) simulations are three possible approaches to investigate the problem. A computational-simulation based approach was selected for the work presented herein based on its ability to provide repeatable results and a parametric approach to the investigation.
Results of the quasi-static particle tracking analyses showed that the greatest numbers of particles impinge on the base of the HDV for the no-boat-tail case, concentrated on the upper surface of the back face of the trailer. The 3-panel boat-tail provides the lowest level of particle impingement. Adding the fourth, lower panel to the boat-tail provides an added surface on which snow particles impinge and can accumulate. This lower horizontal panel provides the greatest concern for potential snow build up, and a rudimentary estimate shows the potential for 4 kg of snow to accumulate per hour on this surface.
The identification of sufficient accumulation of snow on a boat-tail lower surface was based on assumptions regarding the particle properties kicked-up behind HDVs. It is not clear whether the conditions evaluated, which represent a worst case condition, are prevalent on Canadian roads during the winter. It is advisable that on-road observations be performed during various adverse winter conditions for a 4-panel boat-tail to identify the true potential for snow accumulation. It is also recommended that the effect of side-skirts on the potential snow accumulation in a boat-tail be evaluated.
The full report can be found at: http://nparc.cisti-icist.nrc-cnrc.gc.ca/eng/view/object/?id=ff65a068-0834-41c6-8223-bedc411bfda6