A wind tunnel based investigation into the effects of unsteady yaw angles on the aerodynamics of a
simple automotive body has been carried out to increase the understanding of the effects of unsteady
onset conditions similar to those experienced in normal driving conditions.
Detailed flow field measurements have been made using surface pressure tappings and PIV around a
simple automotive model in steady state conditions and these have been compared to measurements
made whilst the model was oscillating in the yaw plane. The oscillating motion was created by a
motored crank which was used to produce consistent and repeated motion which produced a reduced
frequency that indicated that a quasi-static response should be expected. The PIV data are used to
compare the wake flow structures and the surface pressures are used to infer aerodynamic loads and
investigate the development of the flow structures across the surfaces of the model. This includes a
comprehensive comparison of the surface pressures on the sides of the model during a transient and
quasi-static yaw angel oscillation. These results show differences between the two test conditions with
the oscillating model results containing hysteresis and the greatest differences in the flow field
occurring on the leeside of the model.
Two configurations of the same model with different rear pillar geometries were used to isolate model
specific effects. Square rear pillars create strong and stable trailing vortices which are less affected by
the model motion whereas radiused rear pillars created weaker and less steady vortices that mixed
with the quasi-2D wake behind the model base and were affected to a greater extent by the model
motion. The unsteadiness in the trailing vortex separation feeds upstream into the A-pillar vortex
demonstrating that small geometry changes at the rear can affect the entire flow field around the
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.