Aerodynamic drag reduction of a simplified vehicle model by promoting flow separation using plasma actuator

Abstract

In recent years, the dielectric barrier discharge plasma actuator (DBD-PA), which is a fluid control device, has been investigated for achieving both high aerodynamic performance and pleasing styling of transportation equipment. In this study, the authors installed a DBD-PA system on a simplified three-dimensional bluff automobile body to reduce the aerodynamic drag. In particular, the authors focused on the sides of the rear end of the body, where the local shape has high sensitivity regarding both styling and aerodynamic drag. At the rear sides of the automobile-like bluff body, a sharp edge rather than a smooth rounded corner often reduces the aerodynamic drag by promoting airflow separation. Therefore, the authors aimed to reduce the aerodynamic drag by using a DBD-PA system to promote flow separation at the rear end while retaining its rounded shape. Aerodynamic measurements using a one-fifth scale simplified automobile model were conducted in a wind tunnel. Preliminary investigation of the aerodynamic effect at the rear clarified how the longitudinal vortices from the rear pillar and the side edge of the trunk deck cause the drag increase at the rear-end corners. Two parallel DBD-PAs were installed on the rear surface to shift these vortices away from the corners by promoting flow separation. The drag reduction rate reached 3% at the highest applied voltage using the DBD-PA system on a rounded shape, and it achieved approximately half the effect of the sharp-edged shape. The longitudinal vortices were successfully kept away from the rear-end corners by the DBD-PAs. The surface pressure increased with the displacement of the vortices, which led to the drag reduction observed.

Effects of Jet Induced by String-type Plasma Actuator on Flow Around Three-Dimensional Bluff Body and Drag Force

“…Moreover, the effects of the frequency of the pulse jet on flow structures and drag force have been analyzed. Results indicate that the change of frequency of the pulsed jet has a considerable impact on the drag force acting on the square back shaped 3D bluff body [16]. These efforts present certain possibilities of the drag reduction by the active flow control in the case of the square back shaped 3D bluff bodies.…”

“…From the flow structures in the case of without flow control, the longitudinal vortices generated from the slant around the 3D bluff body with slant angle at the rear end strongly correlate with the magnitude of the pressure drag [14]. Since the pressure drag most likely dominates the total drag acting on the 3D bluff body, weakening or transferring the vortices is conducted using flaps or Pas [15,16]. Recently, flow control using a pulse jet controlled by a solenoid valve on a square back shaped 3D bluff body model has been studied [16][17][18].…”

“…Since the pressure drag most likely dominates the total drag acting on the 3D bluff body, weakening or transferring the vortices is conducted using flaps or Pas [15,16]. Recently, flow control using a pulse jet controlled by a solenoid valve on a square back shaped 3D bluff body model has been studied [16][17][18]. The correlation between the flow Pattern in the wake and the generation of the drag on the square back shaped 3D bluff body due to the pulse jet flow control has been reported [16,17].…”

“…Recently, flow control using a pulse jet controlled by a solenoid valve on a square back shaped 3D bluff body model has been studied [16][17][18]. The correlation between the flow Pattern in the wake and the generation of the drag on the square back shaped 3D bluff body due to the pulse jet flow control has been reported [16,17]. Moreover, the effects of the frequency of the pulse jet on flow structures and drag force have been analyzed.…”

“…where fm, U∞, Ton, and Toff indicate the burst frequency, main flow velocity, duration in one cycle for driving PA under burst control, and duration in one cycle for switching PA off under burst control, respectively. In this study, in order to investigate the influences of the fm + on flow around the model and the drag force acting on the model, fm + varied from 0.04 to 16 In the catalog specification, the measurement accuracy of the three-component force transducer is shown as 0.001 N, which is equivalent to 0.024 in terms of a drag coefficient under the without flow control condition at Re = 1.3 × 10 4 in this study. In addition, as a result of calibration using a standard weight, the ratio of load to output voltage shows high linearity with changes in load near the maximum load on the test piece.…”