An experimental investigation of a coherent structure in the axisymmetric mixing layer of a basic annular jet was carried out. The Reynolds number of the flow under investigation was $2.17\times10^5$, based on the outer diameter of the annulus. The flow structure of the shear layer at several downstream stations within 3 outer diameter distance was examined. Conditional sampling technique was employed to educe naturally occuring large-scale structures. Trigger condition was derived from the positive peaks of the longitudinal velocity signal at the given reference position.
Various turbulence structural properties such as turbulence intensity, coherent vorticity, and coherent Reynolds stress were measured.
It was observed that the coherent Reynolds stress production and turbulence intensity level were much higher than those of the conventional time mean value.