An investigation of the effect of rear body pitch on the aerodynamic characteristics of a simplified tractor-trailer model

Abstract

A wind tunnel investigation of the effect of changing the rear body pitch of a simplified tractor-trailer model is reported. This investigation was carried out in the Cranfield Department of Aerodynamics 8 × 6 ft. closed section return circuit wind tunnel. The model was tested on a fixed ground plane and all six forces and moments were measured using an electromechanical balance. The force and moment measurements were complemented by surface pressure and flow visualisation investigations. The model is approximately 1 10 th 1 5 th full scale Reynolds number. To simulate vehicles of different aerodynamic design the model was tested with both tractor and trailer leading edge radii varied. The differences in the flowfield created by these variations and their effects on the forces and moments acting on the model are discussed. The different model configurations were then tested with the rear body pitched at angles in the range −6 < θ < 6. The changes in flowfield due to variation of θ and their effects on force coefficients are described. The results demonstrate a considerable dependence on both leading edge radii and rear body pitch for all forces and moments. Changes in gap flow, wake development and vortex formation cause differences in wind averaged drag coefficient of over 15%.