Increasing the Aerodynamic Performance of a Formula Student Race Car by Means of Active Flow Control 2019-01-0652

This article involves an experimental study regarding the capability of fluidic actuators to increase the aerodynamic performance of a four-element race car rear wing. Sweeping jet actuators are integrated in the upper flap, of which the angle of attack is increased by up to Δα_F3 = 40^° with reference to a passively optimized setup. Different velocities of the emitted sweeping jets are applied to study the influence of momentum coefficients c_μ = 0.04 … 0.98%. To prove the feasibility of the approach, flow control is first applied to a stand-alone rear wing tested in a small wind tunnel. Subsequently, a realistic race car model featuring the controlled rear wing is investigated in a larger-scale wind tunnel. Employing particle image velocimetry, flow visualization techniques as well as pressure and force measurements, we show that the velocity field on the suction side of the upper flap is characterized by flow separation of different degrees when the angle of attack is increased beyond Δα_F3 = 20^° (rear wing only) and Δα_F3 = 30^° (complete race car). Generally, the employed fluidic devices have a positive impact in terms of the aerodynamic performance for all investigated angles of attack as overall downforce increases by up to 22 % are achieved, however accompanied by larger drag. Nonetheless, an in-house simulation indicates a potential lap time reduction of 0.17 % at the Formula Student endurance race circuit at Hockenheim under permanent actuation. Even greater gains are to be expected for a selective employment during cornering only or for skidpad and acceleration competitions.