# The PIV Measurements of Time-Averaged Parameters of the Synthetic Jet for Different Orifice Shapes
## 4 Conclusions  
In this study, the circle, square, and slot orifices were investigated at the same Reynolds number, i.e., \(Re=5000\), and two different dimensionless stroke lengths, i.e., \(L_{0}=2\) and \(10\). The orifices had the same equivalent diameter. The flow fields of time-averaged velocity, TKE, and vorticity were determined based on the PIV measurements. Additionally, the axial and radial profiles at a distance of \(x/d=10\) were presented. It is a very large data set that is unique and has not been comprehensively presented in any of the analyzed works from the literature. The data should be used to validate the numerical measurements. The maximum value of the time-averaged velocity decreased with the increase of the dimensionless stroke length. However, the time-averaged velocity decreased more slowly at \(L_{0}=10\), and as a result, it was higher at a distance of \(x/d=10\) than the time-averaged velocity at \(L_{0}=2\) and the same distance. Nevertheless, the TKE was much higher at \(L_{0}=10\) than at \(L_{0}=2\). In the case of the circle and square orifices, the centerline distributions of the velocity and TKE decreased slower than in the case of slot orifices. The flow fields of the time-averaged velocity, TKE, and vorticity for the slot-long side contract at some distance from the orifice and then later expand. The dimensionless vorticity at a low distance from the orifice \(x/d<4\) was higher at the \(L_{0}=2\), and a fields area of very high vorticity (\(\omega d/U_{e}>|3.5|\)) was also higher at \(L_{0}=2\). The low dimensionless stroke length at the same Reynolds number appears for higher actuation frequency (see Table 1). It is less time between the next expulsions of fluid, in which the SJ can be formed, and the loudspeaker membrane peak-to-peak distance must be slighter. The flow is more orderly, and the TKE is lower than for the high dimensionless stroke length, despite the higher velocity. For the same reason, the parameters of the SJ decreased faster at \(L_{0}=2\) than at \(L_{0}=10\). Conceptualization, E.S. and P.G. ; methodology, E.S., P.G. and P.D. ; software, P.G. ; validation, P.G. ; formal analysis, E.S. and P.G. ; investigation, E.S. and P.G. ; resources, P.G. ; data curation, E.S. ; writing--original draft preparation, E.S. ; writing--review and editing, M.J., P.G. and P.D. ; visualization, E.S. and P.G. ; supervision, P.G. and P.D. ; project administration, P.G. ; funding acquisition, P.G. All authors have read and agreed to the published version of the manuscript. This work was supported by the National Center for Research and Development, Poland, Grant No. LIDER/6/0024/L-10/18/NCBR/2019. Not applicable. All data generated or used during the study are available from the corresponding author upon request. The authors* [PERSON] et al. (2015) [PERSON] [PERSON]; [PERSON] [PERSON]; [PERSON]; [PERSON] Comparison between synthetic jets and continuous jets for active flow control: Application on a NACA 0015 and a compressor stator cascade. _Aerosp. Sci. Technol._**2015**, _43_, 256-280. [CrossRef]
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