A ground-effect diffuser is an upward-sloping section of the underbody of a racing car that enhances aerodynamic performance by increasing the downforce, thus improving tire grip. The downforce generated by a diffuser can be increased by geometric modifications that facilitate passive flow control. Here, we modified a bluff body equipped with a diffuser ramp surface (the baseline/plane diffuser) to introduce a convex bump near the end of the ramp surface. The flow features, force, and surface pressure measurements determined in wind-tunnel experiments agreed with previous studies but the bump favorably altered the overall diffuser pressure recovery curve by increasing the flow velocity near the diffuser exit. This resulted in a static pressure drop near the diffuser exit followed by an increase to freestream static pressure, thus increasing the downforce across most of the ride heights we tested. We observed a maximum increase in downforce when the modified diffuser was compared to the plane diffuser. The downforce increment declined as the ride height was gradually reduced to the low-downforce diffuser flow regime.
Aerodynamics of a Convex Bump on a Ground-Effect Diffuser
Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received September 28, 2017; final manuscript received February 26, 2018; published online April 19, 2018. Assoc. Editor: Daniel Maynes.
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Ehirim, O. H., Knowles, K., Saddington, A. J., and Finnis, M. V. (April 19, 2018). "Aerodynamics of a Convex Bump on a Ground-Effect Diffuser." ASME. J. Fluids Eng. September 2018; 140(9): 091102. https://doi.org/10.1115/1.4039518
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