MULTIPLE LIGHT-SCATTERING IN TURBULENT-FLOW

The time autocorrelation function, C-1(t), of the multiply scattered l ight field can reflect the nature of the flow of a fluid containing sc atterers as markers which follow the fluid motion. It is well-establis hed that, for instance, in the thick medium C-1(t) asymptotically beha ves like C-1(t)similar or equal to 1 - t(alpha), with alpha = 1/2 for the Brownian motion and alpha = 1 for the homogeneous laminar flows. F or more complex flows, even for laminar flows, the t(alpha)-dependence (with alpha not equal 1/2, 1) of C-1(t) is no more valid. Here we der ive the general expression of Cl(t) for a simplified model of nonhomog eneous turbulent flow consisting of a regular array of sheets of disco ntinuous shear flow embedded in a chaotic velocity field.