Comparison Between Finite-span Steady and Synthetic Jets Issued into a Quiescent Fluid

In this study a finite-span synthetic jet is compared to a steady jet with matched Reynolds number (Re_o=615${\mathit{Re}}_o=615$ and 1230). At the aspect ratios studied (AR = 6, 12, and 18) the synthetic jet flow field is very complex yielding very different flow behavior when compared to the steady jet. The entire flow volume was attained allowing for a unique three-dimensional characterization of the jets. Direct measurements of the jet momentum transport showed that the synthetic jet generated up to three times more streamwise momentum than the steady jet. The steady and synthetic jets also showed very different vorticity structures, where the synthetic jet was much more proficient in enstrophy production. Two popular velocity scales for the synthetic jet are compared throughout the article displaying that the interpretation of the results can be very different depending which scale is chosen.