Experimental investigation of the characteristics of synthetic jet with different orifice aspect ratio and frequency

By means of experimental investigation of the unsteady flow near the orifice of synthetic jet actuator using PIV technology and using the phase-locked sample technique,72 instantaneous images and quantitative measurements during one actuating cycle for three different frequencies 10,20,30 Hz are obtained.The PIV measurements rdisplay the properties and structures of the unsteady flow field.Detailed study shows that in the current experiment,with fixed orifice scale and increasing frequency,the corresponding average orifice velocity U0 and stroke length L0 increase.While with constant driving frequency and increasing aspect ratio,both average orifice velocity U0 and stroke length L0 decrease.Also with increasing thickness of the orifice plate d,the friction in the orifice channel increases,consequently the average orifice velocity U0 and stroke length L0 decreases.Time-averaged flow field obtained by 350 image pairs overlapped shows the similarity of dimensionless cross-stream velocity profile and the centerline velocity decay ratio of synthetic jet in the fully developed segment is higher than the conventional 2D free jet.