Detached eddy simulation of a closely running lorry platoon

Abstract

In recent years, the concept of autonomous road vehicles has gained a great deal of technical respectability, with expected fuel benefits arising from running vehicles closely in platoons. However, the aerodynamics of such vehicles travelling in close proximity is still not understood. This paper presents for the first time a detailed study of drag benefits and the flow structure around a platoon of high-sided lorries, through conducting Delayed Detached Eddy Simulations (DDES). The lorry surface pressure and slipstream flow characteristics show good agreement with experimental data. Drag reductions of up to 70% have been observed for all trailing lorries in the platoon. Analysis of the flow field indicated highly turbulent regions on the top and sides of trailing lorries. Turbulent kinetic energy and Reynolds stresses were found to concentrate at the connection region between lorry cab and box. Spectral analysis of the side forces identified oscillating behaviour on each lorry in the platoon due to strong vortex shedding, suggesting that platooning lorries are potentially more likely to develop lateral instabilities than an isolated lorry. The study indicates that autonomous vehicle developers and operators should consider the significant drag reduction benefits of platooning against the risk associated with potential lateral instabilities.