Active Aerodynamic Control of a Separated Flow Using Streamwise Synthetic Jets

Journal article, 2019

LES simulations at Re=1×10^5 and wind tunnel experiments at Re=5×10^5 were con-ducted to investigate the beneficial effect of an active flow control (AFC) technique on theaerodynamic performance of a simplified truck geometry. The paper involves the investiga-tion of a synthetic jet actuator characterized by periodic blowing and suction that defines azero net mass flux flow control mechanism. The actuation aims to suppress the flow sep-aration occurring at the A-pillar (front rounded corner) of a truck cabin. The work flow isdefined as it follows. First, LES at low Reynolds number are conducted for different dispo-sition of the actuation slots. The results show a beneficial effect when the actuation slots arepositioned in streamwise direction compared to spanwise (vertical) direction. Second, basedon the previous considerations, wind tunnel experiments are conducted to verify and sup-port the numerical findings. Both numerical solutions and experimental data show the sametrend and the superiority of the streamwise slots actuation when compared to traditional ver-tical slot actuation. In particular, this work shows the weakness of a vertical slot actuation,when its location is not optimized. A small change in its positioning greatly worsen the effi-cacy of the separation control in terms of drag reduction and separation bubble length. Theslot location directly affects the length of the separated flow region which its reduction canvary between 40–70% based on the positioning. Conversely, a streamwise actuation, span-ning a larger portion of the curvature of a rounded A-pillar, is not affected by this behaviourand contributes up to 80% of the recirculation bubble reduction measured in the unactuatedcase. The effect of the location change and the orientation of a zero net mass flux jet slot istherefore investigated and discussed in this work.