The modal decomposition of two flow fields related to axisymmetric synthetic jet creation has been done by using Dynamic Mode Decomposition (DMD). Both the case without synthetic jet formation defined by nondimensional stroke length L = 0.615 a the case with synthetic jet creation which is defined by L = 1.174 are studied. The analyses are based on the data by using ANSYS Fluent solver. Numerical results are validated by hot-wire anemometry data measured along the jet centerline. The vortex

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... tification is based on residual vorticity, which allows identifying of the regions where continuum particle rotates. It is shown that in the case of L = 1.174 exist travelling vortex which diminishes two diameters behind orifice and this case is very close to the case of a synthetic jet without vortex roll-up. It is possible to expect that the vortex path would be shorter with decreasing stroke length until the vortex completely vanishes and the jet is not synthetized. The travelling vortex speed is measured by using vortex tracking and by using wavelength measured from DMD modes. It is shown that the vortex is travelling not only in the axial direction, but there is also a radial component which leads to the change of vortex ring size. The evaluation of travelling vortex speed leads to not typical behaviour because of a non-monotonous character of the vortex speed. It is shown that the vortex speed has an increasing-decreasing behaviour in the case of nondimensional stroke length L = 1.174.