MULTIPLE LIGHT-SCATTERING IN TURBULENT-FLOW

The time autocorrelation function, C-1(t), of the multiply scattered light field can reflect the nature of the flow of a fluid containing scatterers as markers which follow the fluid motion. It is well-established that, for instance, in the thick medium C-1(t) asymptotically behaves 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. For 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 derive the general expression of Cl(t) for a simplified model of nonhomogeneous turbulent flow consisting of a regular array of sheets of discontinuous shear flow embedded in a chaotic velocity field.