An experimental and computational study of the aerodynamic and passive ventilation characteristics of small livestock trailers

This paper presents a combined experimental and computational study of the aerodynamics and passive ventilation characteristics of small livestock trailers within which the majority of animals in the United Kingdom are transported to market. Data obtained from a series of wind tunnel experiments using a 1/7th scale model of a simplified towing vehicle and trailer are compared with complementary computational fluid dynamics (CFD) analyses, based on steady-state RANS turbulence modelling, of the coupled external/internal flow field. Good agreement between the two is obtained everywhere except at the rear of the trailer. Since the internal flow field and overall ventilation rates contribute to animal welfare, CFD is used to generate detailed internal flow fields and air residence times for use within an overall welfare assessment. The results demonstrate that the flow fields in the upper and lower decks differ significantly and that ventilation rates are much larger and air residence times much smaller on the upper deck.