Downforce

Abstract: A study was performed of a cambered, double-element, high-lift wing operating in ground effect. The effect of ground proximity and flap setting has been quantified in terms of aerodynamic performance and off-surface flowfield characteristics. Measurements include surface pressure taps, force, surface streaklines, and laser doppier anemometry (LDA). It was found from the Haw visualization that the flow is three-dimensional (3D) towards the wing tip with the main element generating most of the downforce, but retains quasi-2D features near the centre of the wing. However, at large heights the downforce increases asymptotically with a reduction in height, Then there is either a plateau, in the case of a low flap angle, or a reduction in down-force, in the case of a large flap angle. The downforce then increases again until it reaches a maximum, and then reduces at a height near the ground. The maximum downforce is dictated by gains in downforce from lower surface suction increases and losses in downforce due to upper surface pressure losses and lower surface suction losses, with a reduction in height. For the high flap angle, there is a sharp reduction just beyond the maximum, due to the boundary layer separating, and a resultant loss of circulation on. the main element.

Abstract: We review the progress made during the last thirty years on ground effect aerodynamics associated with race cars, in particular open wheel race cars. Ground effect aerodynamics of race cars is concerned with generating downforce, principally via low pressure on the surfaces nearest to the ground. The “ground effected” parts of an open wheeled car's aerodynamics are the most aerodynamically efficient and contribute less drag than that associated with, for example, an upper rear wing. Whilst drag reduction is an important part of the research, downforce generation plays a greater role in lap time reduction. Aerodynamics plays a vital role in determining speed and acceleration (including longitudinal acceleration but principally cornering acceleration), thus performance. Attention is paid to wings and diffusers in ground effect and wheel aerodynamics. For the wings and diffusers in ground effect, major physical features are identified and force regimes classified, including the phenomena of downforce enhancement, maximum downforce and downforce reduction. In particular the role played by force enhancement edge vortices is demonstrated. Apart from model tests, advances and problems in numerical modeling of ground effect aerodynamics are also reviewed and discussed.

Abstract: Roller cone drilling wherein the bit optimization process equalizes the downforce (axial force) for the cones (as nearly as possible, subject to other design constraints). Bit performance is significantly enhanced by equalizing downforce.

Abstract: Research is being conducted at the Georgia Tech Research Institute (GTRI) to develop advanced aerodynamic devices to improve the performance, economics, stability, handling and safety of operation of Heavy Vehicles by using previously-developed and flight-tested pneumatic (blown) aircraft technology. Recent wind-tunnel investigations of a generic Heavy Vehicle model with blowing slots on both the leading and trailing edges of the trailer have been conducted under contract to the DOE Office of Heavy Vehicle Technologies. These experimental results show overall aerodynamic drag reductions on the Pneumatic Heavy Vehicle of 50% using only 1 psig blowing pressure in the plenums, and over 80% drag reductions if additional blowing air were available. Additionally, an increase in drag force for braking was confirmed by blowing different slots. Lift coefficient was increased for rolling resistance reduction by blowing only the top slot, while downforce was produced for traction increase by blowing only the bottom. Also, side force and yawing moment were generated on either side of the vehicle, and directional stability was restored by blowing the appropriate side slot. These experimental results and the predicted full-scale payoffs are presented in this paper, as is a discussion of additional applications to conventional commercial autos, buses, motor homes, and Sport Utility Vehicles.