Title: Improvement of aerodynamic characteristics of a passenger car by side-airdams

Authors: H. Ohno, I. Kohri

Addresses: Passenger Car Engineering Centre, Mitsubishi Motors Co. Ltd., 1 Nakashinkiri, Hashime-cho, Okazaki-ahi, Aichi-ken 444, Japan. ' Passenger Car Engineering Centre, Mitsubishi Motors Co. Ltd., 1 Nakashinkiri, Hashime-cho, Okazaki-ahi, Aichi-ken 444, Japan

Abstract: This paper describes the mechanisms of the effects of side-airdams on C_D and C_L and on the aerodynamic characteristics of a vehicle passing through a cross-wind, and also refers to an example for improving aerodynamic characteristics on the basis of hose mechanisms. C_D and C_L, proved to be reduced by side-airdams at zero yaw angle. However, a marked effect of increase in C_L at a large yaw angle appears when the configuration of a side-airdam is not adequate. These mechanisms are investigated by measuring the pressure distribution and the change in the flow field caused by attaching the side-airdams. Side-airdams interrupt the air stream which flaws over the side of the underfloor. Therefore, when the yaw angle is small and the longitudinal underfloor air stream is predominant, the side-airdam accelerates the stream and reduces C_L. On the other hand, when a cross-wind which flows in and out at the side of underfloor is predominant, side-airdams interrupt the underflow air stream, so that C_L, is increased. These results also confirm that C_L is decreased by optimising the bottom shape of the side-airdam for large yaw angles.

Keywords: vehicle aerodynamics; airflow; cross-winds; drag; side airdams; spoilers; yaw angle; vehicle design.

DOI: 10.1504/IJVD.1991.061703

International Journal of Vehicle Design, 1991 Vol.12 No.5/6, pp.598 - 608

Published online: 27 May 2014 *

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