Similarity analysis of planar and axisymmetric turbulent synthetic jets

Data on synthetic jets suggest that planar and axisymmetric turbulent synthetic jets exhibit self-similarity in the far field. A similarity analysis, similar to that of continuous turbulent jet, for both these two-dimensional cases, has been undertaken in this paper. Important differences between synthetic and continuous jets arise because of a larger spread rate in the case of synthetic jets. The analysis predicts the same streamwise variation of velocity and spread rate with synthetic jets as the corresponding continuous jets. It is argued that to first order, the momentum flux with contribution from both mean and fluctuating velocity should be conserved in the self-similar region, but with a value less than that supplied at the source. The predictions of similarity analysis are supported by the experimental data.