Experimental investigation of different transverse periodic actuator-induced flow characteristics

Blowing flow control technology with air sources can enhance aircraft performance, while transverse jet technology may reduce air supply requirements and lower the pressure needed from engines or compressors. To investigate the characteristics of transverse jets, experimental studies were carried out by designing two schemes: Continuous Transverse Jet (CTJ) and Discrete Transverse Jet (DTJ). Using microcontroller technology, two forms of transverse jet actuators were developed for circular free jets that move radially. Particle Image Velocimetry (PIV) technology was used to experimentally study the flow fields of these two transverse jet actuators. By comparing the flow field characteristics under different transverse jet actuators, the mechanisms behind the structural differences in the external flow fields of the two types of actuators are analyzed. The results indicate that the main reason for the deflection of DTJ is the vortex suction effect from adjacent jets, while the deflection of CTJ is primarily due to the spanwise velocity introduced by the mechanical device at the nozzle. This leads to DTJ exhibiting self-similar, dimensionless velocity distribution across sections, while CTJ does not. In the time-averaged flow field, it is observed that the maximum flow velocity and coverage range of DTJ are larger than those of CTJ. The single jet of CTJ, after deflection, forms counter-rotating vortices at different flow directions, causing its flow velocity coverage to gradually shrink in the streamwise direction. The analysis from Proper Orthogonal Decomposition (POD) indicates that, compared to DTJ, the first two dominant modes of CTJ show a greater degree of deflection in the Z direction due to the additional spanwise velocity. The wind tunnel test verifies that, at the same flow rate, the traverse jet increases lift coefficient by up to 70 % compared to the steady jet.