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Abstract
Cornering is a commonly-encountered condition for vehicles, yet one where the aerodynamic implications are not well understood. The curved path results in relative curvature of the freestream flow, causing a continuous change in the angle of yaw along the length and across the width of a vehicle. As this motion occurs within a rotating reference frame a radially orientated centrifugal acceleration acts on the flow at the surface, in addition to a freestream velocity which varies according to the radial displacement.
Flow around a reference automotive bluff body was analysed using Large Eddy Simulations to gain insight into the flow effects attributed to this condition. The yawed condition was initially investigated to gain an understanding of the geometry's sensitivity to flow angle. In this condition the formation of longitudinal vortices due to the oncoming flow angle promoted attached flow and resulted in vortex-induced lift. A side force and an increase in aerodynamic drag also occurred due to an increased frontal area and angled orientation of the wake.
Within the steady-state constant-radius cornering condition, cumulative effects resulted in the flowfield differing from the yawed condition. Acceleration due to the rotating reference frame caused a radially orientated pressure gradient which induced an external side-force directed toward the centre of the corner. The change in flow angle along the length of the bluff body resulted in a yawing moment which acted in a direction that would oppose the yaw rotation within a corner. A contraction of the wake separation bubble caused an increase in aerodynamic drag and an increase in magnitude of the periodic wake bursting mechanism. The bluff body geometry also demonstrated a heightened yaw sensitivity within the cornering condition. Force coefficient changes occurred that were up to three times the magnitude of those for different yaw angles in straight flow.
Finally a new experimental method was developed for the cornering condition, with a proof of concept constructed and an initial experimental analysis conducted. Through conceiving a design that continuously delivered flow to a rotating test-section, the correct relative curvature was able to be achieved within a rotating reference frame.