Taylor and Lagrange correlations in a turbulent free shear layer

The objective of this research was to study the effect of various Lagrange- tracking correlation methods in estimating the eddy lifetime for a two-stre am, turbulent, planar free shear layer. Zeroth-, first- and second-order La grange correlation methods were applied to the time-evolving velocity field data collected from a cinematic particle image velocimetry technique. A ti me scale associated with the eddy lifetime was obtained based on a 2/e corr elation of either vorticity or streamwise velocity fluctuations. When based on vorticity, this time scale significantly increased as expected when the tracking was computed with a second-order Lagrangian tracking technique as compared to a (zeroth-order) Taylor hypothesis approach. However when base d on streamwise velocity fluctuations, this time scale did not increase sig nificantly for the higher order projection methods. The latter result is at tributed to occurrences of "reverse correlation" of the instantaneous strea mwise velocity fluctuations caused by eddy rotation.