Abstract : Annular jet flows are mainly used in industrial processes (bluff-body flows, glass fiber processes...) but paradoxically represent a negligible part of fundamental jet flow studies. So, we are interested in an experimental study of the aerodynamic of an annular jet with a diameter ratio equal to 0.91 (Do=53.88 mm, Di=48.75 mm). Velocities have been measured by laser Doppler Velocimetry (L.D.V.), Particle Image Velocimetry (P.I.V.) and hot wire anemometry in the near field and in the far field until l0 Do diameters.
A spatio-temporal study of the instabilities, which develop in the intemal and extemal mixing layers in the recirculation zone, has been realized. The joint use of non time correlated P.I.V. measurements, of Proper Orthogonal Decomposition (P.O.D.) and a local time resolved A.D.L. measurement allows determining a scenario of the temporal evolution of the wake.
The fully developed merging zone has also been studied from L.D.V. and hot wire anemometry measurements. The variation of integral quantities (momentum, flow rate, velocities, half width of the jet, turbulent Reynolds number), turbulent scales (Kolmogorov, Taylor and integral scales) and mean dissipation rate have been measured on the axis of the flow. A comparison of the variation of these quantities allows including the round jet as an asymptotic case or me annular jets.