A New Technique to Measure the Aerodynamic Response of Passenger Cars by a Continuous Flow Yawing 2007-01-0902
A comprehensive treatment of a new technique to measure vehicle aerodynamic response under side wind conditions is presented. In opposition to the traditional measurement technique of yawing the vehicle by rotating the turntable, the flow itself is continuously deflected by the Pininfarina Turbulence Generation System (TGS), while keeping still the vehicle under investigation.
By using this new technique it is possible to assess the dynamic behavior of vehicles, with particular regard to side forces and yawing moment, in more realistic unsteady conditions opposed to the static setup of traditional measurements.
In the first part of this work, the unsteady flow, generated by the TGS, is characterized both by means of 4-hole Cobra probe and stereo PIV measurements in empty and non-empty wind tunnel configuration. Some data acquired on the road will also be shown and compared with wind tunnel measurements.
In the second part, the different wind tunnel setups will be used to test various vehicles in the wind tunnel, and the results will be compared with traditional wind tunnel measurements.
The results obtained show a dynamic behavior which significantly varies with the yawing frequency of the oncoming flow. This technique allows to investigate vehicle behaviors which are overlooked in traditional wind tunnel measurements, and to establish closer links with on road tests.