Integral Quantities of Axisymmetric Synthetic Jets Evaluated from a Direct Jet Thrust Measurement

This paper proposes a relatively simple and user-friendly experimental method for evaluating synthetic jet (SJ) characteristic velocity and fluxes of time-mean momentum and kinetic energy. The proposed method is based on the direct measurement of the SJ thrust by means of precision scales. The measurements were performed over a large range of Reynolds and Stokes numbers. The Reynolds number was between 1600 and 7100, and the Stokes number was between 15.4 and 202. To correlate the obtained results, hot-wire measurements of the velocity profiles were used and spatial-temporal integration of the hot-wire data was performed. To obtain the integral quantities, the correlations between the thrust and hot-wire results were used. Despite the relative simplicity of the proposed method, it yielded a very good evaluation of the characteristic velocity and fluxes of time-mean momentum and kinetic energy. The study was mostly focused on SJs with moderate and high stroke lengths (larger than five diameters of the orifice). The experimental data were within ±3.4% of the proposed correlation. For small stroke lengths (i.e. below five orifice diameters), the maximum deviation was within ±5.4%.