Experimental study on the synergy of sweeping jets on the afterbody flows of a slanted-base cylinder

Abstract

The synergistic effects of sweeping jets (SWJs) hold significant potential in controlling afterbody vortex flows of a cargo fuselage. A combination of SWJ pairs, located at various streamwise positions, are employed to investigate the efficiency of their synergy in influencing the afterbody flows of a slanted-base cylinder with a 30° angle at a Reynolds number of 200,000. The total mass flow rate is kept similar resulting in a variation of the momentum coefficient of SWJs from Cμ=4.3×10−3 to 1.0×10−1. Energy efficiency and mass flow interactions were examined through direct force measurement, stereo Particle Image Velocimetry (PIV), and surface pressure measurement. The results show that the jet impingement on the surface is stronger when there is synergy among SWJs positioned more upstream (e.g. the combination of Top and Mid pairs), particularly at low momentum coefficients (Cμ < 0.02); conversely, when considering the synergy of SWJs located more downstream (e.g. the combination of Mid and Bot pairs), a greater reduction in surface pressure is observed at higher momentum coefficients (Cμ > 0.05); a potential net energy saving is achieved in the case of the combination of Top, Mid and Bot pairs (T+M+B). The controlled vorticity distribution observed in the collaborative configurations was mostly sandwiched by curves of individual SWJ cases, which is due to the fact that downstream SWJs (located at Mid and Bot positions in case T+M+B for instance) manage to weaken the enhanced vortex induced by the SWJ at upstream (located at Top position), highlighting a compromise in the synergy effectiveness of the jets with reverse roles at different positions. However, by taking the similar advantages of SWJ at certain positions on the vortex control, at Cμ=1.7×10−2, the vorticity reduced by the case combining Mid and Bot pairs is even 7 % and 13.5 % greater than cases Mid and Bot, respectively, which could serve as a hint on the potential benefit of SWJs’ synergy in the future.