Dynamics and entrainment mechanism of the jet flows from an elliptical nozzle: time-resolved tomographic PIV measurements

In this study, the coherent structure dynamics and entrainment capability of elliptical jets emitted from an nozzle with aspect ratio (AR) values 1 (i.e., a circular jet), 2, 4 at fixed Reynolds number 3000 were experimentally characterized by flow reconstruction using tomographic particle image velocimetry modal decomposition time-domain spectral proper orthogonal method. Statistical analysis indicated that synthetic jet had greater rate momentum flux than jet. The temporal showed all AR = dominant frequency Strouhal (St) 0.39, representing leading Kelvin–Helmholtz (K–H) vortex ring in each trailing was St 0.28 whereas 0.70. It found pairing merging, as well axis switching, are common jets, while merging process not strictly repetitive, sometimes single stretched disintegrated, without coalescing. When 4, there also large-scale between two merged rings, alone underwent transformation breakage. merger always occurred major plane because plane, vortices approached other result self-induction mutual induction. strongly correlated K–H weakly passing jets. appeared upstream part structures it enhanced axis-switching region An contribution mode to mass better nozzle, mainly many streamwise generated.