Organized motions in a fully developed turbulent axisymmetric jet

An experiment has been conducted to study the occurrence, configuration and dynamics of large-scale coherent vortical motions in the fully developed region of a turbulent axisymmetric jet. The key idea is to use vorticity signals from a spatial grid to detect and sample large-scale vortical structures and then use the (smoothed) vorticity peaks of spatial vorticity patterns to align and ensemble average successive realizations to determine structure configuration and dynamics. Measurements were made in an air jet at Re_D = 69000 by employing a radial rake of seven x-wires to obtain the azimuthal vorticity map. Two additional conditioning probes were placed ±90° away from the rake to determine the three-dimensional phase and hence the structure configuration.