Abstract
In this study, a numerical investigation of the active aerodynamic control via flow discharge was performed on a two-dimensional simplified vehicle with a spoiler. The analysis was performed using computational fluid dynamics techniques based on the unsteady Reynolds averaged Navier–Stokes equations. Unlike the conventional aerodynamic control methods, in which the control flow is forcibly injected to increase the lift or reduce the drag, the flow discharge method uses the ram air flow to reduce both the downforce and aerodynamic drag of a road vehicle. The technique of aerodynamic control via the flow discharge is applied to a simplified vehicle with a rear spoiler. For the isolated spoiler, at a discharge speed of 40% of the vehicle driving speed, the flow discharge at 75% of the chord exhibited a reduction of 4.5% and 1.8% in the aerodynamic drag and downforce reduction, respectively. For the vehicle with a spoiler, the drag and downforce were respectively reduced, on average, by 3.4% and 19.3% for a vehicle velocity range of 100–300 km/h; in this case, the discharge speed was 40% of the vehicle driving speed, and the discharge position was 75% of the chord owing to the interaction between the spoiler separation flow and vehicle wake.
Highlights
The three aerodynamic forces acting on a high-speed driving vehicle, namely, the drag, lift, and side force, have a significant impact on the driving stability, power performance and energy efficiency of the vehicle
The discharge flow velocity was limited by the geometric shape of the spoiler because the ram air is used as the discharge flow, and under the conditions considered in this work, it was noted that the discharge flow rate was approximately
The aerodynamic drag and downforce were simulated with respect to the discharge position and discharge direction for a single spoiler shape
Summary
The three aerodynamic forces acting on a high-speed driving vehicle, namely, the drag, lift (or downforce), and side force, have a significant impact on the driving stability, power performance and energy efficiency of the vehicle. The aerodynamic drag acts in the opposite direction of the driving direction of the vehicle and can considerably influence the maximum speed, fuel economy, and energy efficiency of the vehicle. The downforce acts in the direction opposite to that of the lift and tends to push the vehicle toward the ground. The downforce increases the road grip of the tire, thereby increasing the vehicle stability during turning and braking. Most high-performance vehicles are equipped with rear spoilers to increase the downforce [7,8]
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