Box Trailer Aerodynamic Design Optimisation

Aerodynamics experts at HORIBA MIRA have developed a unique design for box trailers that, alongside subtle aero enhancements to the cab, reduces total drag by up to 30 per cent whilst retaining its practicality in operation.

The main idea was to develop a trailer design that recognised the operational considerations of business but still delivered tangible performance gains in financial and environmental terms.

To meet these objectives, HORIBA MIRA's aerodynamicists made use of the latest Computational Fluid Dynamics (CFD) simulation techniques along with their expertise to improve the poor aerodynamic performance of a standard 4.5m box trailer - seeking to preserve its load capacity but reduce drag to the levels of a smaller 4m equivalent.

Starting from the initial CAD geometry, HORIBA MIRA engineers applied advanced morphing techniques to modify the trailer shape and maximise aerodynamic efficiency without compromising overall load space. They then added underbody panels to the cab and trailer to further minimise drag - the result of which was a reduction in aerodynamic drag of up to 30% whilst avoiding the complex surfacing and space constraints of more complex ‘tear drop’ designs.

HORIBA MIRA’s efforts to retain practicality when redesigning the 4.5m trailer saw the rear door aperture reduced only marginally, to the height of a standard 4m box trailer, for ease of loading and underbody panels enable easy access for routine maintenance on brakes and axles and apertures were created in the side skirts to allow for checking of the wheel nuts.

HORIBA MIRA’s aerodynamicists calculate that the resulting fuel savings and reduction in CO2 emissions (of between 15 and 20 per cent) mean the cost of the adaptations to the trailer could be recouped by fleet operators within 12 months. The enhancements can also be applied to curtain-sided trailers – making it highly commercially viable and highlighting why MIRA’s design was recognised with an award from by the Low Carbon Vehicle Partnership in November 2010.

CFD analysis of baseline Box Trailer design.

CFD analysis of MIRA's improved Box Trailer design.