Stereo-PIV Measurements on Circular and Chevron Synthetic Jets

The evolution and flow mechanisms of a circular and of a 6-chevrons synthetic jet are experimentally investigated with stereoscopic particle image velocimetry (Stereo-PIV). Both synthetic jet configurations are driven at the same frequency equal to 96 Hz and at the same electrical power equal to 5.2 W. It yields to a Reynolds number (Re) equal to 5600 and 6000 and a Strouhal number (Sr) equal to 0.115 and 0.106 for the circular and the chevron synthetic jet respectively. Stereo-PIV measurements are carried out along both streamwise and crosswise planes in order to investigate the dynamic behavior of the vortex ring. A three-dimensional reconstruction of the vortex ring is performed by acquiring data in the crosswise plane. The chevron synthetic jet shows the presence of streamwise vortices together with a wavy-like vortex ring. The streamwise vortices disappear at approximately 4.5 diameters downstream from the nozzle exit where the vortex ring resembles a round circular one. The current investigation establishes that it is possible to generate a synthetic jet even in presence of a chevron exit nozzle, which does not disrupt the azimuthal coherence but confers a particular pattern to the vortex ring.